doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com question on 2 3/4 16ga, shells in 2 1/2 chamber

what do you lose when you fire a 2 3/4 in shell in a 2 1/2 chamber gun.my reloader is a mec 650 and want load a 2 1/2 inch shell.

Maybe nothing. Maybe your forward hand.

Ease your mind order a 2 1/2 kit from MEC - I did.

it want mount on a progressive loader.i called them.

It depends on the gun, so you might want to be more specific with your question. Big difference between a Parker 0-Frame 16 twist or Damascus with short chambers and a Win Mod 1912 20 gauge with original chamber. If you decide not to load 2-1/2" shells, you could load low pressure 2-3/4" shells for your gun.

I have to fox sterlingworths and two parker #1 frame steel barrels.I dont want to change the chambers.I have been thinking of loading low pressure shell in 2 3/4.what would be a good pressure.my load now is about 7000 psi,and 1100 ft/s

this should be ok in them right? what will it do for my pattern.

Bell's experiments showed that the pressure rise for a 1/4" long hull is between 0% and about 15%. Many folks are having good results with 2 3/4" reloads in shorter chambers. They use generally loads listed in loading literature of 5,000 psi to 7,500 psi, light shot charges and 1100-1200 fps velocity. The low pressure is kind to the metal and the low recoil is kind to the wood and shooter.

Most patterning results from light charge, low velocity, low pressure loads pattern at least as well typical loads - no magic.

Sherman Bell's tests were with 12 gauge if I recall correctly. I wonder if smaller gauges would behave differently. A 16, 20 or 28 gauge bore or forcing cone filled with the wall thickness of the fired hull may be more critical than a 12g.

First note I am not a Ballistician but have gleaned a few things over the years.
Much experimenting was done on this matter just prior to & immediately following WWII by the British upon adoption of the "Fold Crimp" shell. The general conclusion was that if the appropriate load for the earlier Roll crimp shell was placed into the longer hull & closed with a fold crimp, giving approximately the same length to the "Loaded" shell that neither ballistics nor pressure were significantly changed. The important factors were that "The Loaded Length" of the shell remained approximately the same, thus allowing ample room for the crimp to open without interference, only lapping into the cone a small amount. Normal chamber length for a 16ga is 2 9/16" while nominal 2 3/4" cases often run as much as 1/16" short, thus only giving a lap of about 1/8". The factors involved here are that pressure rises rapidly prior to actual moving of the charge. As soon as the charge moves then the "Burning Chamber" begins to enlarge & pressure starts to decrease. Of course it takes just a Wee amount time for this to occur, but generally by the time the charge is entering the cone pressure has peaked & started the downward side of the curve. Thus essentially what one would expect is not a "Rise" in pressure, but a slight retardation of the falling side. This would not be picked up on a pressure gun which records only the Peak or Max pressure but would require one which can measure the actual curve. The important factors are that first the load itself is suitable for the gun in question, next there is a space between the end of the "Loaded" shell & the end of chamber & finally that the gun does not have one of those very early type of chambers which have either a step or very short Bevel allowing the end of the case to actually lap up into the bore, but be a normal type cone of at least 3/8" length, usually some longer. I do not believe the actual gauge is a very significant factor if these other considerations are met.

Thanks for taking the time to respond with such a detailed explanation. What you say makes a lot of sense to me.