I am in the process of geting the chambers polished and the smith recommended extending the forcing cones.

What would be the Pros and Cons to extending the forcing cones?

Pro: Gunsmith gets more paid work.

Con: You have less money after he does work.

Really, I NEVER have the forcing cones lenghtened on my old guns. I will polish them if rough (common situation for cheaper guns) -- that really does make difference in evenness of patterns. I do have one that previous owner lengthened forcing cones. Does not shoot any more even patterns than those with short cones from early 1900s.

Niklas

I agree 100% with Niklas.
I have the forcing cones lengthened on my target guns.

Shooter's myth that it would decrease recoil and improve patterns. No proof for any claim.

This is just good old fashioned snake oil.
Modern powders are progressive burinig powders and the wad type, wad pressure , crimp depth and forcing cones all play a part in developing the fire in a very progressive way.

Lengthen your forcing cones and the first thing you will notice is much dirtier barrells as you are now not getting a full burn and if you put your favourite rounds over the Chrony you will find that they are not going as fast. Recoil is generally reduced by the drop in velocity

Next thing you do is get a faster burning powder and guess what your speed is back up but so is recoil.

If pattern quality is a problem buy better shells or shoot lower velocity shells, if recoil is a problem shoot better quality low velocity shells.

There is nothing really new in shotgunning, it was all sorted out in the 1800's and that remains true to today, but there are plenty of snake oil salesmen out there who will tell you different in an effort to part you and your money.

Hotrack

I personally, conducted my own tests on the same gun, lengthening one barrel's cone and leaving the other. The first test was standard forcing cone vs. a 1 1/2" long cone. I felt no recoil difference, but did see a decernable difference in pattern around the edges. The "flyers" were less and the pattern bprder more defined. Some might say it had the effect of making the pattern smaller. I say it reduced the damaged shot that created the edge irregularity. Either way, it wasn't my imagination. Next, I cut the standard cone to a 4" long cone and compared it to the 1 1/2" cone. I could see little difference. There might have been some slight improvement in pattern edge quality, but it was inconclusive to me, since I didn't do quantitative analysis nor a statistical sample of shots fired.

Me? I could not tell any recoil drop from a longer cone. I think many modern clays guns have longer cones than a early gun or SAAMI spec chamber and won't benefit. My K80 had longer cones than a SAAMI chamber. I do believe it matters in pattern quality from my testing. If the guys above have tested more thoroughly than I and have a different opinion, so be it. Until I see something to convince me otherwise, I believe it helps the pattern.

If the walls of a gun are thin, easing the forcing cones will take off a little strain according to my barrel man. He also recommends the job if cones are very steep, as this will reduce pressure and recoil will be eased a little. I recently had this done to a client's damascus barreled Purdey that was down to 17 thou towards the end of one tube.

If cones are very steep, you may find anything other than 65mm shells (in a 2 1/2" chamber)get ragged at the ends because they are not opening flat -this produces extra pressure and more recoil and requires surgery unless you stick to the 65mm shells. I had this as an issue with a Purdey re-barrelled in the early 1970s and solved the problem.

If any of the above are a concern, it can be a good idea.

However, doing it for its own sake is not somthing I routinely have done. 'If it ain't broke don't fix it' generally works a guiding principle for me.

Agree with Small Bore. Bell's tests report some reduction in pressure when cones are lengthened. But like SB, I doubt I'd bother unless the cones are short and steeply angled--which they sometimes are, on older guns.

Brister reported a reduction in felt recoil (with no velocity loss) on a gun that had both steep cones and was underbored, after barrel "surgery". However, he not only had the cones done but also had it overbored, so it's hard to tell what caused the change.

Like Dig and Larry, I don't routinely modify my barrels with a long cone even though I own two reamers and all the hones. In fact, I haven't lengthened a forcing cone in more than ten years and that was on some Citori's and the BSS test gun. Virtually all of my vintage guns have been left alone. I just don't see the big, big improvement in either doing it or not. If I were a serious clay competitor, I'd probably insist my gun have long forcing cones, overbore, and long cone chokes. But, I'm not.

PS, I take that back, I did lengthen a barrels cones on that 410 nitro special Lefever a few years back, because the chambers had been lengthened poorly. I had to have my friend custom grind a taper pin reamer to match the chamber diameter. The end result was that the chambers ended up at 3" long and long cones. And yes, I do indeed routinely shoot 3" 410's in that gun.

How long are the cones on a Becker Fox?

Mark

There is so much of this which is purely speculative, but would like a few "Explanations" of certain points. Let's examine a bit what happens inside a shotgun bbl. Upon firing the pressure rises very fast, reaching it's peak inside the chamber & then begins to fall, rapidly at first & then in a lessening curve as the shot progresses down the bbl, increasing the volume the gas has to expand in. Changing the forcing cone angle (lengthening) would give a very "Slight" increase of volume in the area, which would tend to slightly decrease pressure. A "Slight" change in friction could also accomplish the same purpose. Either would affect recoil, to the same extent & in the same direction, it affects velocity, ie increase velocity, increase recoil etc. "If" the same load is fired & achieves the same velocity, but has lowered pressure in the cone area, then it has to off-set in elsewhere. I can see no possible affect lengthening a cone can have on a thin bbl in the forward portion. If you have a bbl with good chamber wall thickness but thin forward & want to "Favor" them, shoot light loads put up with the fastest burning powder which will stay within allowable chamber pressures & forget the cones. The faster & "Less Progressive" the powder used the lower will be bbl pressure while the slower & "Most Progressive" powder used will result in higher bbl pressures. This assuming equal shot wt @ equal velocities. Chamber pressures will be the opposite. One simply needs to study the bbls in question & decide which is the most important low chamber presure or low bbl pressures. If both the only option is "Light" loads overall.

If you are going to shoot ammunition with plastic wads it is less an issue with longer cones. However, it may still be possible to get an ocassional 'blooper' due to a poor seal in cold weather or with certain less pliant synthetic wad materials.

The older abrupt or steep forcing cones pre-dated plastic wads by almost 100 years and work well with any of the card or fiber wad ammunition. If you are going to use or load card, cork or felt wadded ammunition you will be 100% better off to leave the cones alone.

I can see no reason ever for having a cone over 1.5" in length, ever. Chuck's comments mirror what the old flyer shooters figured out way back when .. a slight improvement in the pattern quality due to less pellet deformation. Remember that for the most part flyer loads at that time used card wadding and did not generally have the shot protected.

FWIW, Kreighoff's have almost no cone to begin with or about that length [1.5"]and many sporting clay type guns now sport similar long cones in their oversized bbls.

Generally speaking, your money would be many times better spent on lessons with a qualified shooting instructor. That is actually the best money one can spend on shooting, if we are to be perfectly honest about it.

775,

32", less the 3" chamber length ;-)

While I'm not of the crowd that touts long cones reduces recoil, I do believe there is more to how a person percieves recoil than the simplistic calculation using velocity, mass and gun weight. That calculation doesn't consider the nuances of time/acceleration of the mass within the barrel. Most of you here agree that the gun begins to recoil at least as soon as the load mass begins to move. I think many of you agree that different burn rates of powder will accomplish the same velocity with different peak pressure. I will go a bit further out on a limb and say many of you recognize that it takes the same total energy (a.k.a. "energy under the curve") to push a load to the same velocity no matter the time/distance to accelerate it.

So, if two loads of the very same velocity and weight of shot, using different powders, that have different peak pressures, the total energy expended has to be the same after all is done. That means the powder is exerting higher pressure further down the barrel on the lower peak pressure load. Some of us may not be able to feel that difference, some may. It's simply the inverse of how a hydrocoil "lowers" recoil. It spreads it over a longer time.

Don't make me come over there tw!

There are I know many out there with more mathamatical abilities than I. However it is my understanding a normal bbl time for a shotgun is on the order of .003 sec. Assume a 1 1/8oz charge with a combined shot & wad weight of 60 grains, fired from a 7lb gun. During that .003 second while the charge travels the length of a 218" bbl the gun will have moved (If in Free Recoil) approx 5/16" & attained it's recoil velocity. The rest of it's movement is from inertia. Personaly, I am extremely thankful that I am so totally insensitive, that from the same gun acheiving the same ballistics I can't tell if it's using Pink dot, Purple dot, & has ½" or 5½" cones.
I simply do not have the means of proving it one way or the other, but am extremely confident that such things as recoil pads, hydro-coils, gas operated autos etc which acheive lower "Felt Recoil" do so by spreading it out over a longer time frame than that .003 sec, or they are still working in the "Inertia Stage".

A longer forcing cone will reduce stress concentration at the transition from chamber diameter to bore size. From this perspective longer forcing cones are a plus.