doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 2 3/4 inch to reduce pressure or not

I have gotten some very kind advice getting into this hobby of collecting vintage doubles. One piece of advice I want to follow up on: in a 2 3/4 inch chambered 12 gauge double of say 75-100 year old vintage, assuming a gunsmith says yes to firing at all, would you try to reduce chamber pressures, if so by how much, and if so, are there any factory shell offerings that would meet the reduced pressure requirements?

Many of our vintage double gun manufacturers followed a policy of holding their chambers 1/8-inch shorter than the intended shell -- in 12-gauge 2 5/8-inch chamber for the 2 3/4-inch shell, in 16-gauge 2 7/16-inch chamber for the 2 9/16-inch shell and in 20-gauge 2 3/8-inch chamber for the 2 1/2-inch shell. Parker Bros. and A.H. Fox Gun Co. for sure followed this policy. The Remington specification sheets for their Parker doubles were reproduced in the two-volume book The Parker Story show this. Here is one of the pages --



What may have been done to a chamber in the 100 +/- years since a given gun was made is impossible to know. I for one, can't see any benefit of removing metal from a critical area of a shotgun barrel.

The heaviest 12-gauge loads our North American ammunition manufacturers offered back in the day in 2 3/4-inch or longer shells were 3 1/2-drams of bulk smokeless powder or 28-grains of dense smokeless powder, such as Infallible or Ballistite, pushing 1 1/4-ounce of shot. These loads were actually a bit higher pressure than our current SAAMI specs for 2 3/4-inch 12-gauges.







After the Great War our ammunition manufacturers went to work applying the progressive burning smokeless powders developed during the war to shotgun shells. First on the market was the Western Cartridge Co.'s Super-X in 1922 with Peters High Velocity and Remington's Heavy Duck Load (soon morphing into the Nitro Express and later Remington Express) following quickly. These progressive burning powders moved out that 1 1/4-ounces of shot at higher velocity but actually lower pressures than the old bulk or dense smokeless powders. That 1 1/4-ounce of shot at higher velocity meant greater recoil forces being applied to the head of the stock. That wood is now 60 years older than when I started playing in this vintage doubles game.

This is a link to an older thread of mine asking a similar thing back in 2014. Advice was specific to the cartridges and pressures that I should be using for my vintage British shotgun, 12 gauge, 2 3/4 in. chambering.

Birmingham Proof Pressures 1904-1925

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TC

Fortunately today we have very good data as to the pressures of loads used at the turn-of-the-century forward, the loads recommended by U.S. double gun makers, and the proof pressures used by the makers
https://docs.google.com/document/d/1F2sQuPm05IE4VWYYnCkvuXmYEzQoWd_SQgaAfUOZEFU/edit

A.H. Fox recommendations courtesy of Researcher



Scroll down about 3/4 way here for more information
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit

IMHO, after an evaluation by a double gun specialist with the interest, equipment (wall thickness gauge and bore scope), and expertise to properly do so, limiting recoil in guns with 100 year old wood is more important than limiting pressure, if the pressure of the load matches the pressure of the loads for which the gun was designed. In general, lighter recoiling loads in the same gauge do generate less pressure, recognizing that pressure is not part of the recoil equation.

Agreed.

Tonight I shot some Red Dot and American Select loads. Both were 7/8 oz, both were about 1250 fps. The latter had considerably less recoil, or so it seemed, than the former.

When I got home, I looked at burn rates and RD is faster than AS. Is it safe to say that recoil correlates highly with burn rates when load weight and velocity are the same? It would make sense to me that they would. I suspect that the latter would also have lower max pressure as well.

i hear shooting 2 3/4" shells in 3" chambered guns, with forcing cones lengthened, reduces felt recoil...

makes sense....

opinions?

Neil Winston did not think burn rate influenced our perception of recoil Brent
Fast vs. slow powder pattern study
https://www.trapshooters.com/threads/a-test-of-fast-vs-slower-powders-winston.68141/

Interesting! Thanks for that. But Roman, what's up with him?

I'd rather have seen this done on a scale of some sort. Some sort of repeatable, objective measure. He has the right experimental design until he gets to the measurement of the actual recoil.

I'm pretty sure we all agree that different loads DO have different recoils. A quail load vs. a heavy 3" goose load have to be different in recoil given different payloads and velocities such that, if we put a scale behind the gun, we could objectively measure differences in recoil. Surely someone has done that.

But that said, the difference between the burn rates of RD and GD are greater than between RD and AS, I believe, so perhaps the effect would be very small and too small to "feel" regardless of what I thought I felt.

The late British shotgun guru Gough Thomas disagrees that the burn rate of powder does not influence our perception of recoil (which we typically refer to as "felt recoil".) He does so based on experiments conducted in the UK by British powder company IMI. The following quote comes from Thomas' book "Shotguns and Cartridges", chapter entitled "Weight and Recoil": (Note that Thomas uses the term "sensible recoil" rather than "felt recoil.):

"To demonstrate the influence of rate of burning on sensible recoil requires a prolonged course of scientifically controlled experiments, such as those carried out by IMI when they were developing their modern range of powders and ammunition . . . They involved the firing of many thousands of cartridges by a team of nine experienced shots of varying build, shooting under a wide variety of conditions with guns of different types, weight and boring. The cartridges were all loaded to give the same velocity to the same shot charge, though by powders of various rates of burning. The shooters did not know what they were firing but were merely required to give marks for recoil. They were unanimous in assigning the lowest recoil to the cartridges loaded with the fastest burning powder, the dynamical effect of which was checked throughout by electric accelerometers built into the stocks of the guns, and their conclusions have since been widely confirmed."

Thank Larry. ;Rate of burn has to have some effect, noticeable or not. But I'm surprised that fastest is leastest. Think of accelerating from 0-60 in a economy car vs pedal-to-the-metal in a Lamborghini. B