doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Short chambers and recoil?

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.