doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com gap between barrel flats and water table?

I have often wondered how much stress occurs on firing. My factory M-21 pamphlet page 6 shows a M-21 being fired without a locking bolt "the barrels held down only by hand leverage as shown in the above illustration." Reading further..."holds the breech of the barrels down firnly on the water table of the frame."

Take a look at the length of the M-21 action and compare that to the average double gun. If the action was a couple of inches longer it could be held closed by a rubber band.

Mike not bad service for a couple of lowly "hardware Store" guns.

"Mike,Your great pictures show it all. Bobby"

Thanks, Bobby. I sure wish you'd take up Fox photography!



I agree! I've shot the heck out of 5 Foxes and can brag on them a lot.

My M-21 water table is about 2.5 in. and my Fox is about 2.125 in..3/8 in. must make a huge difference.

Either there is quite a bit of difference in action bending force and barrel opening force, or the gap is not needed. IMO, it is the former.

DDA

It is noted here that both Dan Lefever & W W Greener stated their guns could be held shut by the thumb without the bolt.
My Lefever frame from breech face to approximate center of the
Ball screw hinge is 2 3/4", however as most Greeners were box locks I believe they would have for the most part have been shorter frames.
In my opinion I suspect the force needed to keep the gun closed on firing is much less than most folks tend to think & the Bending force applied to the frame is likely much Greater.
A short bar may be stiffer & actually better re frame bending unless it has too much metal removed for the lock work, not sure.

I have heard these tales told many time ,fingers , apiece of string etc. etc .
I wonder if in the example given either Messer's Lefever or Greener ever actualy did so ?
Worth keeping in mind these claims were made in the days of black powder .

The advice I got from an old craftsman at Cogswells when they were in Piccadilly is that the flats should clear the smoke.

Re the forces generated and how a double shotgun receiver reacts to them, it seems that the phenomena are a little more complex than the old notion of the cartridge acting on the breech face.

1-There is no mention of the Poisson effect on thick walled cylinders, and the chamber end of a barrel is definitely a thick walled cylinder.

2- Slamfire DIY shotguns are a totally unlocked system. In these the barrel and "breech" tend to recoil as one unit. It seems that the cartridge adhesion to chamber walls is strong enough to make both act as one unit in recoil.

3- Judging by barrel imprints on breech faces the above seems to be a factor we have yet to analyse.

4- Small Bore has written about firing a double totally unlocked, with no ill effects. Gough Thomas writes about a double firing with nothing but two layers of scotch tape holding it shut. If you measure the locking bolt of a pump or auto it is puny by comparison to the locking system of a double. As far as I know autos and pumps do not suffer from loose lock up or coming off the face. That should tell us something about the forces acting on the bolt.

This topic of forces needed to hold a SxS closed is pretty intriguing. I would think some of the more technical minded folks here may be persuaded to experiment with this notion of something-less-than-a-fastener holding it shut. Not that it would need to be measured in an empirical way or anything, but maybe a zip tie? Glass filament tape? Obviously not a hand.

I was once told by a trapshooter that he removed the barrel from his Model 12, affixed a live shell onto the end of the breechbolt and fired the thing inside a paper bag. Since the cartridge was not confined it did not build up pressure and the shot just dropped harmlessly into the bag. Urban legend or.....?

Craig Libhart