All elements kept equal but chamber length, is there any reason a shotgun would have more recoil when firing a 2 &3/4" shell in a shorter chamber? Thanks for the replies!

Ben, I don't know the scientific answer but can tell you after shooting tens of thousands 2 3/4" shells in both 2 1/2" and 2 5/8" chambers I can't tell any difference in recoil.

I've heard anecdotal reports of increased recoil, even with British shells especially designed for guns with 2 1/2" chambers (but in slightly longer cases), on a few very old guns with short and sharply-angled forcing cones. Seems to be more a function of the cone than it does chamber length. Like Joe, I've shot a lot of 2 3/4" shells, reloaded to appropriately low pressures, in guns with short chambers, without any significant increase in recoil. Sherman Bell, in his "Finding Out for Myself" series in DGJ, did report a slight increase in pressure with some 2 3/4" shells in 2 1/2" chambers. But a pressure increase does not necessarily equate to a recoil increase.

Dad's Fox AE 20 2.5 chamber shot many cases of 2.75 shells and is still sound but it did go through 3 stocks. In my experience it a stock splitter.
bill

Thanks to all for your replies. You confirm my thinking that the situation would not effect recoil. Thanks again.

Actual recoil is only a function of gun weight, weight of shot and velocity of that shot.
Felt recoil is a subjective quantity and you find 'theories' and I use the term 'theory' loosely, all over the place but mostly concerns what is technically called 'impulse' or how the force applied acts over time. Shooting a 2&3/4" shell in a 2&1/2" chamber may cause other problems but not recoil related.-Dick

If the shooter is sensing buttstock acceleration as felt recoil, as opposed to total recoil, then there could be the following issue. The payload is constant in weight, so the rearward acceleration of the gun will be basically (neglecting the powder gas portion of the acceleration) proportional to the forward acceleration of the payload. Acceleration will be basically proportional to pressure except that there may be a slight additional acceleration in the forcing cone if it is sized and shaped such as to have some venturi effect on the shot charge. Also, per Bell, there might be enough pressure rise to increas acceleration enough for a shooter very sensitive to acceleration to sense it as increased recoil.

I would not totally discount the possibility, but would add that my experience, which seems to match general experience, is that it is not a factor for me.

One of these years at a large event perhaps a blind firing test of felt recoil could be set up and put an end to the endless discussions of felt recoil, perceived recoil and actual recoil as relates to velocity, short chambers, short and long forcing cones pressures.

Bill, I'd be more inclined to blame it on the game loads you were probably shooting than them being 2-3/4". The same thing would happen with 2-1/2" high velocity, high pressure loads.
Now a Parker would handle it a little better. "wink"

My 3" chamber Uggy is a kicker. Someone in the past saw to a recoil pad (no wonder about why, at least) and a tiny crack is developing up next to the tang.
All I've ever fired are 2 3/4 1 1/8th oz trap loads, it still bites me.
A few others have reported the Uggies hit them hard. Mine has tight bores and chokes, maybe forcing cones as well. I'll have some sense put into it via Mike Orlan when I have some spare coin, hope it helps.


Best,
Ted

I did that very thing with an A grade Fox a few years ago at the Southern Side by Side and a couple of smaller shoots. (Over 200 subjects shot a 26" cut barrels cyl and cyl gun with only one forcing cone lengthened.) I never managed to sell the story but the results were interesting. I'm sure I still have the results somewhere in my computer. The short story is that there wasn't statistical evidence that there was a percieved difference. On the reporting sheet, I asked the vollunteers if they believed it made a difference and caught a few trying to look in the chambers.

Trust me, you could run the results on 20/20 and it wouldn't end the discussions.

Dick;
I absolutely believe your results. Had I seen them on 20/20 I likely would "NOT" have. I lost total confidence in it & all similar shows years ago, as nothing but "Headline/Rating" seekers. It is known fact they have not always aired reliable results.
Ted;
Prior to having that work done, do a statistically signicicant chronograph test for velocity on the shells you are & will be using. Have enough of them to run a like test after the work is accomplished. I will state up front, "IF" you do not get a significant change of ballistics you will likewise not get a "Feelable" change of recoil.

Though not one to place every cent of emphasis on recoil formulas, I think one should use a chronograph to verify equivalent velocities between short/long chamber guns before concluding that differences in perceived recoil have anything to do with the chambers.

Sam

I'll bite.........again. I can testify that recoil was brutal shooting AA 2 3/4" 7/8 oz. target loads in a 20g 1922 Trojan with chambers measuring very close to 2 3/8." The gun literally jumped out of my hands, and it was obvious to the others on the squad. I do wish that I had paid more attention to the case mouth, but was a bit (more than usual) discombobulated at the time, and never tried that experiment again

Several years ago Kent gave me various 12 guage Tung. Matrix duck loads to test (before Katrina) when Destry and I were still shooting ducks at Delacroix LA (soon to suffer again with a dose of BP's oil). To compare the 2 3/4-inch Kent TM Waterfowl loads I bought several boxes of 2 3/4-inch Bismuth; some of the boxes of Bismuth were loaded in Winchester-marked shells while other Bismuth boxes held shells marked Eley. All shells, Kent and Bismuth were clearly marked 2 3/4-inch on the boxes and the shell casings. I was shooting my 1928 Parker GH F&F...

When the gun doubled and the recoil was severe! I don't recall whether I got the duck...but when I tried to open the "Old Reliable" it was stuck shut. I intuited that the shells were swollen and the extractor rods would not push the shells and, thus, the extractor rods were holding the gun closed. I removed the fore-end to release the push rods and the gun opened, albeit with the Bismuth/Eley shells firmly stuck. Destry cut a rod from the blind brush and we were able to push the shells out. The Parker Gun--to its credit--suffered no damage.

The Bismuth/Eley shells, however, were destroyed with mouths stretched and shredded and brass bases swollen, distorted, and cracked. Each Bismuth/Eley shell was clearly stamped 2 3/4-inch, but measured over 3-inches open!

So there it is: 3-inch shells in 2 3/4-inch chambers are not good. I stopped shooting the Bismuth. When I got home I did some forensic research by deconstructing some of the loaded shells: The Bismuth-Winchester shells were all 2 3/4-inch as marked; the Bismuth/Eley shells all opened to 3-inches even though they were marked 2 3/4-inch both on the box and shell casing.

I called Ken Levine at Bismuth and he blew me off; I wrote an article praising Kent and blasting Bismuth...R. E. Petersen passed away and I heard from a source that the widow's lawyers advised her not to sell the Bismuth brand for the liability, but I believe that someone is still making the stuff. I hope they measure their powder and shot loads better than they measured their shells.

I sold the remainder of those bogus Bismuth/Eley mis-marked accident-waiting-to-happen shells (about 15 boxes) to none other than Doug Turnbull last year. We marked each box "3-inches" with a black magic marker.

And the point of all this is that over-long shells can produce great recoil causing a gun to double.

Fortunately the gun was not damaged, probably due to the manufacturing date coincidental with Lindbergh flying solo across the Atlantic versus a turn of the century gun reflecting the technology and metallurgy which preceded the Wright brothers barely getting off the ground. EDM

I personally have noticed a difference. My 2 3/4" low pressure loads (7/8 oz. @5200 psi @ 1150 fps) have alot LESS recoil than the 2.5" Nobel Sports, Gamebores, and B&P's I was shooting in my short chambered guns. I would like to note too that my handloads produce significantly less pressure than most factory loaded 2.5" shells, especially when compared to the Italian offerings. RST's are just about as soft shooting and have almost as low pressures as the handloads, but way more expensive. I've shot thousands of 2 3/4" shells in my vintage guns and have never had a cracked stock or blown barrel. The only stock I had crack was on a Darne and I was shooting my last box of 2.5" fibre wad Noble Sports. Those puppies had some bite. All of Sherman Bells articles over the years concerning this very topic has convinced me that if you keep your pressures down, shot charge light, and velocities within reason, you should never have a problem.

Dustin

Miller,
True 'dat, but, I'm not typically the guy who can best utillize a gun with .019 and .039 points of choke. The gun is also under bore, at .725.
I scratch my head at the pattern board, wondering what in heavens name I should do with a gun that throws lovely, 45 yard patterns of, 1 1/4 oz loads of #4s. That also leave my vision fuzzy for a few seconds after the shot. Normal 1 1/8 oz loads of shot any smaller are actually un-even and, sort of clumpy, for lack of a better term.
It is a somewhat light 12 gauge, 6lbs 12 ozs, I think, and I shudder to think of pulling the trigger on a 3" round, although the gun was proofed for that.
If a guy used a tight choked gun his whole life, well, maybe. But, I haven't.

Still pondering what I should do. I like guns "in proof" but, I like guns I can shoot comfortably, and hit the more common 25-35 yard shots with, a little better.

I think.


Best,
Ted

Like a lot of other folks, i have been shooting 2 3/4 shells in short chambers with no problems. Caveat that they are low pressure loads (mine) using one of Joe Woods recipes. BUT the lil 16 hammer gun I just picked up will NOT allow a 2 3/4 inch shell to be chambered, without a great deal of force being applied...It will shoot short RST's as long as I have it...

That sounds more like a Diameter problem than a length one. Assuming the 2 3/4" shells are fold crimped & the gun has 2 9/16" (65mm) chambers there should be absolutely no problem encountered from the length in chambering them.
Have you already tried the RST's, unles they are a little slimmer you may well encounter the same problem.
Chamber itself may have been reamed under present minimum size.
PS; You did mention you used reloaded shells. Were those hulls possibly fird in a "Loose" chambered gun. They may be running oversized. I have encountered this in using hulls I had picked up which were fired from an Auto-loader. Some of these seem to have "Generous" Chamber dimensions.

I think I'm confused here. I thought this post was about shooting 2 3/4" shells in guns originally chambered for 2 1/2, 2 5/8 shells ect. Obviously different loads will make a marked difference. I was assuming we were talking the same shot and powder charge.

My experience was with identical ammunition and different chambers. When you change loads, all bets are off.

LD I think 2 Piper is correct. Check the crimp area of your reloaded shell and see if it is not "belling" out. Just a little bit can cause a hard chambering round (by the way it doesn't make the shell unsafe just makes it a pain in the ass to chamber) If it is there are some simple adjustments that can be made to your crimp start and final crimp dies on your re-loader that should solve your problem.

Dick the discussions on recoil, felt recoil etc. have raged for years but the simple truth is that recoil is governed by Newtons Third Law of Motion which simply put says that for every action there is an equal and opposite reaction.

So long as the total ejecta weight, exit velocity and firearm weight remain constant recoil energy will remain the same no matter what the hull length is, no matter what the chamber length is, no mater what the forcing cone angels are and no matter what the bore size is.

Here is the formula for calculating recoil:

E= 1/2(Wr/32)(WbxMv+4700xWp/7000xWr) squared

E= energy in foot pounds
Wr= weight of gun in pounds
Wb= weight of shot and wad
Mv= muzzle velocity in fps
Wp= weight of powder in grains

You will notice that there are no allowances for chamber length, chamber pressure or anything but gun weight, ejecta weight and muzzle velocity.

Dustin, I've noticed pretty much the same thing. However, the short shells are often hunting loads rather than target loads--perhaps more velocity and a heavier shot charge. Other than RST's and some Polywads, it's hard to find short shells in this country that are loaded to the same kind of modest velocities (and reduced shot charges) many of us use in our low pressure, 2 3/4" reloads.

Several years back, a now-deceased friend was shooting his own low pressure reloads through one of his Belgian "best" game guns. I had been sent some Brit loads to field test. Can't recall what they were, although I know they were neither Eleys nor Gamebores. Anyhow, I handed him a couple and said, "Here, try these light English loads!" After which he told me where I could put my light English loads.

If it didn't make a difference, why bother even noting the chamber length on the gun (if it is marked) - why not just 12GA and let it go at that?

There are so many reasons why it might or might not work that you can waste a lot of your life at it. Why not just use the correct case and LET IT GO AT THAT?? And besides, you trust these people to know what YOUR gun is doing?

And BTW - I have a Perazzi with .723 bores and it is way soft shooting even with pigeon loads. Gun fit, not bore ID, makes for recoil or not. And that is not JMO, it's a simple fact.

WtS

Had the same issue with my 16s. Factory RSTs would chamber perfect but my reloads would not. Culprit was the brass base of the hull needed to be re-sized slightly smaller during the reloading. Lowered the re-sizer collet (MEC Sizemaster) by 1/8 turn and the problem was solved.

Except that totally ignores acceleration rates which DO affect PERCEIVED recoil. The total recoil energy is easily calculated per above but what you FEEL is not without incorporating the impulse as has been noted elsewhere.

WtS

Well, heres the deal...RST's chamber and shoot perfectly....BUT even FACTORY 2 3/4 inch loads require a good push to make em chamber...So, I dont consider it a problem, I'll jusr feed it RST's...Perceived recoil discussions always open up a can of worms. I dont notice any more recoil in my 12 bore guns, shooting 2 3/4 loads in shorter chambers....But then again, I shoot a .416 at water jugs....

WtS As far as I know there is no calculation for "PERCEIVED" recoil even using the same ammunition and firearm because everyone's nervous system is different. I do agree wholeheartedly that stock fit, type of mechanical configuration of the gun ( gas operated, recoil operated of fixed breech) and recoil reduction system used and even the activity you are engaged in (shooting flying game birds versus shooting pattern) will definitely affect how we perceive recoil but the constant is what is measurable and perception isn't.

So the moral is get your gun fitted, shoot the ammunition your gun was intended to shoot and drink 7 year old sour mash whisky.

I agree except for the sour mash whiskey. It's not that there is anything wrong with fancy "corn squeezins", it is just that I would prefer 50-year-old Cognac...if I could afford it.

Chas,
I bet your P gun weighs more than 6 3/4 lbs, by the way. I think you forgot that part of the story....

Best,
Ted

You beat me to it, Ted.

As for only the gauge and not the chamber length . . . well, in the case of the specified 12ga, they make them from 2" up to 3 1/2". If you could fit a 3 1/2" shell in a 2" chamber, or even a 2 1/2" chamber, I think you'd get a rather unpleasant surprise when you pulled the trigger. That's too much additional case length . . . not to mention the fact that the 3 1/2" 12ga has a much higher proof than the 2 3/4" or 3" guns. And even higher still than the 2" or 2 1/2" guns.

Most loaders are set up for 2 3/4" hulls, which are readily available (and of very good quality) in this country. Given the price of factory 2 1/2" shells, it makes a whole lot of economic sense to reload 2 3/4" hulls to appropriately low pressures, especially if you're going to shoot a 2 1/2" gun a lot.

And we now know why CA is in dire economic straits. I thought it was just the politicians, but it appears to have short-circuited Wonko too. Must be something in the water.

It may or may not be the reason for the higher perceived recoil when shooting drastically longer shells than the chamber length, but here's my take on why it is. When the crimp opens and contacts the forcing cone, preventing complete opening, for a microsecond the entire load being propelled pushes against the forcing cone. Note that this is a FORWARD push. The load chokes itself down to get through the constricted case mouth as the gun is pushed ever so slightly forward. Then, after passing into the barrel the load passes without interference through the barrel and exits the muzzle where, and when, the laws of physics again cause gun movement. This time rearward. However, because of the slight forward push at the forcing cone the gun now has further to move as it recoils into your shoulder. This greater movement causes a harder "whack" when the recoiling gun meets resistance in the form of flesh and bone. This all occurs so quickly that we cannot perceive the forward movement from the short chamber, but I am convinced it occurs.

Some of us, being more recoil sensitive than others, can notice less difference than others. I can definitely feel the difference when a 3" shell is fired in a 2 3/4" chamber, but can't feel it when the difference is only 1/8".

One of the local idiots around here was, for a few days, fooling people into shooting a short barreled coach gun that he had gotten hold of. He was loading it with 3 1/2" magnums loads and betting them they wouldn't pull both triggers at the same time. I am not certain, but believe the gun has 2 3/4" chambers, certainly not over 3". He was forcing the shells into the gun and closing it before letting the (other) unsuspecting idiot shoot it. It is, amazingly, still sound. He never was.

Baby cartridge in a Brit toy gun or a pigeon load in a Perazzi.
That actually has nothing to do with the underlying physics. And like was mentioned it would be VERY difficult to acquire and factor in the acceleration rates of the shot charge. That does NOT mean that it is not the preeminent factor in perceived recoil as far as internal ballistics is concerned.

Obviously, gun fit can mitigate the nasties but plain old Newtonian physics still sets the parameters.
And that is not some JMO last I checked

And BTW, you guys are really funny with all the made up physics. And I thot the amplifier people were alone in the level of their nutso cosmic constructs. All y'all will have to reach some to equal them but you're on the way. Good luck on that

WtS

Uh, not an expert, Wonk, but, your analysis seems a bit light on the law of "conservation of momentum", that being a lighter object exhibits greater impulse than a heavier one receiving the same amount of energy. If I load my sub 5 lb. Italian folding 12 gauge ( Relax! we're talking a 3" chamber here-who says the Italians are cowards?) with one of your pigeon loads, I'm pretty sure it'll bend your remaining teeth in a way the P gun might not.
Only thing I can surmise about amps is, I'm betting you own several....
Best,
Ted

Nah. You got that all wrong. Its the pressure pushing forward to open the crimp that gives the gun the forward push, not going through the forcing cone
Seriously, I am reminded of a statement I once read from Julian Hatcher, "That sounds good IF you say it Real Fast, but it won't hold up to scrutiny". The gun doesn't swap directions in recoil, it moves reaward only.

You may well be right, Miller. But, if the pressure pushing forward gives the gun the forward push, as you say, and not the payload, then could not that ever so brief forward push from the pressure lend to some minute forward movement? I'm not proposing a big forward motion, only a tiny amount in a microsecond. The difference in the recoil is not much, either, as I perceive it, just enough to notice a difference.

Ballistics have been being studied for a mighty long time. No one seems to have discovered the reversal of motion & reported on it. Upon firing a conventional gun the expanding gases from the burning powder are exerting their pressure in all directions. As the projectile moves forward the gun moves backward.
I have fired a 3.5 rocket launcher of Korean vintage. There was a definite reversal of movement with this, "BUT" this is not a conventional firearm. It is a simple launch tube open at both ends, the "Rocket" is propelled by its exiting gases. There is a definite forward pull from the friction of the rocket moving down the tube & a slight reversal as it exits & the blast of gases strike the muzzle bell, put there to protect the firer. This is of course a totally different situation from a gun having a closed breech.
The shot charge is accelerating as it enters the cone & will continue to acceleraate as it passes through it. The gun also will continue to accelerate in the opposite direction. This will not present a situation where the gun would be moved away from the shoulder, to then return with greater force.

Well reasoned, Miller. I can see that. Don't think too hard of me for my theory. You wouldn't believe what the mind of a shotgun nut can come up with when he spends as many hours a day as I do in a tractor cab. You can listen to just so much of that drivel on the radio in a day without nutting up. Then again, there IS the occasional crow that gets a load of 6's out of my old 32" Montgomery Ward New Leader that rides with me.

Stan;
I would believe. Being 72 yrs old & having been interested in shotguns since around age 15 I have heard a lot of them. My very first shotgun which was all mine was an old, pre WWI J Stevens double. This gun had a through bolt for stock attachment.
Would you believe someone told me if I took off the butt plate & dropped a penny down in the bolt hole it would reduce the "Kick". Now even at that age I could see absolutely no effect a penny down the stock bolt hole could have on kick, but naturally had to try it. Just as naturally no difference at all could be felt, but as far as I know that penny is still there, just have no idea where the gun is.
If anyone ever runs across a J Stevens model 325 with a penny in the stock bolt hole it was probably mine. Actually this was a rather heavy gun & I was shooting regular field loads so kick was not an issue to begin with. I have though been rather skeptical of all "Magic Cures" for recoil ever since & found virtually all of them to simply exist in someones imagination, as you say shotgunners are an imaginative lot.

We, obviously, are speaking to different topics.

Unfortunately, like the guns, several is a long passed assessment.

WtS

None of the complicated formulas have anything to do with my test. It dealt with PERCIEVED recoil as reported by shooters who didn't know which barrell had a lengthened cone.

There was no statistical difference. If you think you gun will kick less after you lengthen the cones, you have a preconcieved notion that will affect your perception. Happens all the time.

When I ran the NC Civilian rifle team I had a shooter I was using in the National Trophy Match who had a bad day before the match. He was certain the barrel in his M14 was going bad. An All Guard Coach who was helping me showed me how to me correct the problem.

We took the gun and shooter to the repair trailer having advised the armorer what we were doing. The armorer told the shooter he'd found a big problem and had corrected it. The next day, the confident shooter shot better than he had in months and talked the rest of the trip about how his gun had been going south for weeks. The coach and I just looked at each other and grinned.

Wonky,
I don't see several as an unfortunate thing in either case.

Best,
Ted

Good job, 2-p. Very well explained.

Chamber length has nothing to do with recoil, so unless the short chamber produces more velocity, it will not produce more recoil. Beside that, "more recoil than what"? Unless you lengthen the same chamber, in the same gun, and use the same shells, what would be you comparing it to?

I think there is a horsefly in the yogurt on your explanation as well, Jim. If one has a short chamber gun, and uses 2 3/4" ammunition, only to discover the cases ripped off down to the contact length at the cones, velocity will not automatically increase-but, recoil will. I suspect pressure would, also, but, I can't prove it.
A friend owns a French Charlin that rips the cases down to a bit below 2 1/2", sometimes even with European spec 65mm ammunition. To say the gun is unpleasant to shoot is an understatement.

Best
Ted

Your statement doesn't prove anything, either. There would obviously be SOME increase in pressure and likely some increase in velocity(if it's ripping the cases off). You don't say what length your imaginary chambers are but if your example even exists, they would probably have to be 2", in order to "rip off the 2-3/4" shell "down to the contact length at the cones". Ripping off part of a case that extends past the cone, into the bore is believable, not barely into the cone. Of course, you don't say what the chamber length of your friend's Charlin is, and more importantly, how much it weighs. I'll bet it is a very light gun. Ask him to lengthen the chambers and report back if the "unpleasant shooting" becomes pleasant. Maybe he's putting the shells too far into the chambers, resulting in the Gough Thomas recoil syndrome.
Best to you, as well

Why would recoil automatically increase? If pressure goes up, acceleration of the shot load will also go up. This would tend in the direction of higher MV, but, I agree, not automatically assure it. The pressure spike will increase powder burn rate and might cause burn-out enough early to result in similar MV's.

My thinking is the effort it takes to uniformly rip the end off a case, in the direction of the shot, would have an equal and opposite effect going the other direction-toward the shooters shoulder. More recoil being the result. The effort expended by the cartridge powder charge to rip the end off may or may not increase velocity, but, I'm guessing not, since more "work", has been done, the work of ripping the case mouth off. Even if it it undesirable work, it costs energy. The expenditure of more energy in this example is more likely to cost velocity, inspite of higher pressure.
My opinion, proven nowhere I know of.
Unless you can think of a reason for this not to be true, I'll run with it, based solely on the one example of a gun that I've seen that does it.

Open to any theories you may have, however.

The gun in question has 65 stamped on the tubes, but, a 16 gauge chamber tool from Brownell's stops a good 1/4" prior to the 2 1/2" mark. Monday morning gun at the proof house, maybe? It is well used, so, someone isn't/wasn't sensitive to recoil. Owner doesn't hunt or shoot it, just a collector. Nothing will be altered on this gun, by him.

Best,
Ted

Charles Fergus reported something along these lines with two Brit guns he owned. Both 2 1/2", one late 19th century with short, sharply angled cones; the other 1930's with longer cones. 2 1/2" shells were fine in both. However, the longer Brit ammo (67.5 MM, I think) loaded for use in 2 1/2" guns resulted in the ends blown off the cases and increased recoil in the older gun; no problems in the newer one. Don't know whether those shells were getting past the cones on the older gun, but something was causing very different results in one compared to the other.

If I remember correctly the gun Fergus reported on was a very early gun which essentially had "No Cone" but a step at chamber. It could have been cut with something like a 45° angle rather than being absolutely square, but this would still be essentially not a forcing cone as such. In such case the longer shell would indeed open into the "Bore" of the gun.
As to more Work producing more recoil, if one placed a fitted solid steel plug into the forcing cone which effectively blocked the bore & totally prevented the crimp even opening at all or any movement of the charge enough "Work" would be performed to "Rip Open" the chamber walls but no recoil would occur because nothing moved.
Anything which "Retards" the movement of the shot, friction etc, produces a "Forward" push on the gun equal to the retardation of the charge. This is the reason "Pressure" is not a factor in recoil formulas. Recoil is the result of the gun moving in an opposite direction to the charge.
One more time, Anything which "Retards" the movement of one "Retards" the opposite movement of the other. Mr Jim Legg's statement is absolutely true, any "Anecdota" statements notwithstanding. Any statement of increased recoil without accurate velocity checks is totally "Worthless"

If I remember correctly the gun Fergus reported on was a very early gun which essentially had "No Cone" but a step at chamber. It could have been cut with something like a 45° angle rather than being absolutely square, but this would still be essentially not a forcing cone as such. In such case the longer shell would indeed open into the "Bore" of the gun.
As to more Work producing more recoil, if one placed a fitted solid steel plug into the forcing cone which effectively blocked the bore & totally prevented the crimp even opening at all or any movement of the charge enough "Work" would be performed to "Rip Open" the chamber walls but no recoil would occur because nothing moved.
Anything which "Retards" the movement of the shot, friction etc, produces a "Forward" push on the gun equal to the retardation of the charge. This is the reason "Pressure" is not a factor in recoil formulas. Recoil is the result of the gun moving in an opposite direction to the charge. This is also why that the statements which have been made regarding overboring etc reducing friction allowing for more velocity with lessened recoil are "TOTAL BUNK". It sounds good if you say it Fast, but doesn't stand up to scrutiny. "Julian Hatcher saying"
One more time, Anything which "Retards" the movement of one "Retards" the opposite movement of the other. Mr Jim Legg's statement is absolutely true, any "Anecdotal" statements notwithstanding. Any statement of increased recoil without accurate velocity checks is totally "Worthless"

As an addition to the above I have read (& fully believe) from loading Co ballisticians the "Max" pressure of any given load can be varied significantly with no change other than crimp. Thus a stronger crimp, being harder to open will produce significantly higher "Max" pressures. "Anyone" who fires a load from a gun & finds the crimp end ripped off & subsequently fires another like load from it totally deserves to have his gun destroyed. When the British were expermenting with the fold crimp shell being loaded in a longer length which would contain a regular roll crimp load & end up approx the same "Loaded" length some 50-60 yrs prior to Bell, the determination was that such was acceptable with no significant change in pressure or ballistics "BUT" that no shell should be fired in a gun in which the "Loaded Length" of the shell entered the cone. It is also to be noted they were only working with "Normal" length cones "Not" a stepped chamber.

Miller, we do know from Bell's tests that pressure does increase when firing long shells in short chambers, although usually not a significant amount (a few hundred psi). And we also know that lengthening the cone usually results in a reduction in pressure, vs a short cone (from the same tests). Of course that doesn't tell us anything about recoil, because those tests were conducted in a pressure gun. The 2 3/4" low pressure reloads I've fired in short chambers--many thousands of them--generally seemed quite mild in the recoil department. But then I never compared them to the same load fired in a hull cut down to 2 1/2" either.

Ted, I can't improve on Miller's explaination.

Generally speaking, we would expect that the total recoil would be much more dependent on the energy content of powder charge in the load rather than the pressure curve (assuming reasonable burning of the powder). Looking at various loads with powder of varying burn rate and similar MV shows that there are many ways to "skin the MV cat," pressure curve wise. However, I, for one, hold that there may be people sensitive enough to sense felt recoil from the gun's rearward acceleration, as opposed to the gun's rearward velocity as in total recoil. If this is true, then it may be that pressure peaks in the forcing cone cause rearward acceleration peaks of the gun and are detectable by certain sensitive shooters.

In the above context, it may be that tearing off the end of a hull indicates a higher pressure (it may not be necessarily so, though) which might show up as more felt recoil to a sensitive shooter without an increase in MV. However, I don't thing either felt recoil or MV increase/decrease is "necessarily" so. It is a complex question to which we are short a few pieces of data.

Not to beat a dead horse, but I think it is critical to not think in terms of pressure but rather the resultant charge acceleration. AND, as Rocketman has noted, acceleration per se does not make MV.

It would be fairly simple, but probably expensive, to build a rig to measure the RESULT of all of those bits and pieces. And fun as it would be to quantify and chart all that I'm guessing the Lotto God would have to intervene for me to do it.

WtS

OK, Wonk-Lets say we build our device with an infinite number of barrels, and we can dial up any chamber/bore size/choke combination. The accelerometer/scale we have built into the receiving end is capable of determining peak recoil force, pulses of any duration that occur during firing, and peak acceleration. If we standardize our test loads, for pressure and length, which chamber length, forcing cone length and taper, bore size, and choke combination are going to produce the least measured response on our machine?
We can get to velocity variations at a later date-this first test is all about recoil in its various measurable forms.
Anyone want to take a stab? I can only guess that an over standard bore, with gentle cone dimensions and minimal if any choke gets us a bit tamer recoil event at firing.
That is a guess.
Who's next?

Best,
Ted

"Anyone want to take a stab? I can only guess that an over standard bore, with gentle cone dimensions and minimal if any choke gets us a bit tamer recoil event at firing.
That is a guess.
Who's next?"

I am but only if any or all of those things reduce velocity, no other reason. And that's not a guess, it's a fact.

"I can only guess that an over standard bore, with gentle cone dimensions and minimal if any choke gets us a bit tamer recoil event at firing."

Larger bore equal more volume in the combustion chamber and larger wad base area. Payload acceleration is the product of pressure times wad base area. Bigger combustion chamber will, at some point, equal lower pressure. When the product of lower pressure times larger wad base area becomes less than standard bore pressure times standard bore wad base area, the acceleration will drop and so, likely, will recoil experienced either from total recoil (MV will probably drop) or from acceleration (maybe felt) recoil.

The gentle cone and choke may make a longer, flatter shot acceleration spike and might show up in acceleration (maybe felt) recoil. The cone and choke constrictions should cause an acceleration to the shot and gun during passage and a shooter sensitive to gun acceleration might sense this as felt recoil.