doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Would You Buy an Out of Proof British Shotgun?

Condor, to be completely on the safe side, you don't want to use ANY American factory load in a 2 3/4" British double unless that double has passed magnum/superior proof--and your gun has not. Pressures generated, even by "light" loads (in terms of shot weight) and even with moderate velocities, can still approach the 11,500 psi SAAMI pressure ceiling. Anything that reduces recoil--lighter shot charge, lower velocity--is a better choice for vintage guns. But it doesn't get you off the pressure hook.

One reason many of us reload is because we can produce low pressure loads with light shot charges at moderate velocity, all of which are good for vintage guns. If you don't do that and you want to minimize risk to your vintage gun, then you're pretty much stuck with shooting factory low pressure loads from RST and others.

Thanks L. Brown, that is as straight forward as one can get and gives the layman the " yes" or " no" answer with the questions I had in one brief paragraph addressing all the issues....perfect for me....thank you again and to the the others who posted advise as well. The effort by all who explained reminded me of a T. R. Quote..." Nobody cares how much you know, until they know how much you care."

Thank you to all who participated in the very informative discussion about chamber lengths and proof markings and the very important discussion about manufactured shells and their ballistic properties.
The better we understand what we put in our guns the better we can take care of them and avoid costly and exasperating damage

Justin, that's what this place is all about. I think all of us who've been around pretty much since the beginning have learned a lot. In many cases, we're passing on what we picked up from participants who are no longer with us, like Larry Barnes, Bill Wise, and too many others.

I recently purchased an 1894 vintage Greener Emperor. The gun has only one proofmark on each barrel, which is the provisional black powder proof. Graham Greener figures the gun was kept in-house as a platform for development of numerous single trigger mechanisms. The barrels are immaculate and measure .045" at 15" from the breech. I use very light RST loads for ruffed grouse. The lack of other proofmarks probably had a significant bearing on the low price I paid for the gun.

Condor;
Realize that a light load does not necessarily have a higher pressure than a heavy one, its just that the actual shot weight &/or velocity does not guarantee a certain pressure level. The thing to remember is when we talk about the pressure we are generally talking about the "Maximum" chamber pressure. There is of course pressure behind the wads all the way down the barrel. Once ignited the pressure rises very rapidly to its maximum within the chamber itself, then begins to fall as the shot moves down the barrel. With either a heavier load of shot or a higher velocity or both, the total average pressure over the full length of the barrel will be "Greater", But the "Maximum" may not be. The burn rate of the powder plays an important role in this. The two example I cited from Alliant the heavy load was with Blue Dot, a slow progressive burning powder, while the light load used Red Dot, a very quick burning powder. Thus while it did peak very quickly to a higher pressure it would have also fallen quite fast & had a lower pressure for the rest of the travel down the barrel. Too many time we tend to think of pressure only in terms of that maximum peak & totally ignore the rest of it. That peak of course is important, but we also need the "Rest of the Story" as Paul Harvey used to say.

Miller... That is also a great summary....the types of powders and burn rates I now see are key...this was mentioned before in other threads but with formulas that made my eyes cross...thanks...I have copied this thread to save.

Pressure curves do vary depending on powder, shot charge, etc. However, they all--including even black powder--have one characteristic in common: They all drop very rapidly once the shot charge is outside the chamber. Unless your gun has a pretty thin spot in the barrel somewhere not very far in front of the chamber--and that's one reason we check barrel wall thickness--it's highly unlikely that pressure will result in a burst anywhere further down the barrel.

I saw a pressure curve for a 20 ga load using Green Dot that indicated peak pressure @ around 0.5 Milliseconds after ignition. The example used was to show the impact on pressure of various crimp lengths & wads but basically showed peak pressure @ 0.5 milliseconds with variance of about .0075 milliseconds depending on the changes made (obviously changes in pressure resulted also but I don't remember what they were & it's not relevant).

Does anyone know how 0.5 Milliseconds translates to inches down the bbl for peak pressure?

To ask the question another way, does peak pressure actually occur in the chamber or is it farther down the bbl like in the forcing cone area?

There was once a poster here who was doing experimental work and trying to sell the results to the government. I forget his name. I think this was in the original format days MANY years ago. He has devised a duplex load (according to him) which got 8000 fps in a Garand and 10,000 fps in a Browning 50. The theory was to keep a nearly constant pressure until the bullet (or pleshette) leaves the barrel. This required a bull barrel as thick as the chamber area. It was a mixture of a $1200 powder and a $32,000 powder. The trick was for the pressure to increase as the volume increased behind the projectile resulting in a constant pressure behind the projectile. That way, the chamber pressure was as constant as possible. Neat idea it would make a Garand or Browning 50 a tank killer. Many it was real, maybe it was hooey, but the idea was interesting.