doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Is this considered off face?

You have a Sterlingsworth with top rotary bolt & when the gun is held up against a bright light you see a Very thin uniform gap 'tween the back end of the barrels & the breech face. You open the gun & put a post it note- thin paper measuring 4 thousands, against the breech faces & the gun will close but the paper can't be removed without tearing. There is no free play or wobble at all when the fore end's off & gun is shaken & when you try to wiggle the barrels. Lever is slightly to the right of center. In other words the barrels lock up tight but the back ends of barrels do not contact the breech faces by a couple thousands of an inch. Is this gun off face?

From your description the gun is off face , but on bolt. If you remove the forend, and shake the receiver, side to side, you may feel the barrels move.

Must ask, in the context of C-bomb's question, what causes a non-uniform gap; i.e, barrels clearly gapped away from breech wall at 3 o'clock right barrel and 9 o'clock left but in contact breach wall elsewhere? Have seen on early NID. Is permanent distortion of breech wall possible (particularly in case of gun with central rotary bolt slot)?

jack

Rabbit,

An SxS that is properly on face may well have a gap at the base of the standing breach. The top and the mid of the standing breach should be firmly engaged. There should also be a .001-.002 gap between the barrel flats and the water table. This is refered to as the spring space. Gap at the top right and the bottom left, of the standing breach, suggests that something is out of order.

Phil

I'll agree with both Rabbit & Phil something is not right on the standing breach. A Sterlingworth is one SxS that you very seldom see "shot loose".

Best regards, George

An interesting topic. After reading this post and the other one re: "off face" I set up a precision vernier caliper to read .000". Holding it up to a light, I can't see any gap. Then I set the caliper to read .001" and I can see a very distinct gap, parallel between the reading faces of the caliper. A gap of .002" looks pretty big when held up to a strong light.

Back to double guns, the barrels would have to be absolutely PERFECTLY fitted in order not to see a gap somewhere. Actually it would have to be an "uniform contact fit" as the term is used by machinists, and there would have to be a gap between the barrel flats and water table to allow that contact fit to be maintained over time as you open and close the gun. If absolutely no light could be seen between the back end of the barrels and the breech faces when the gun was new, it would likely show some light at the bottom when the gun was used a while.

LIkewise, if the machining and fitting were just a thou or two off when the gun was assembled, you'd probably see a gap here and there. Wear of the hinge pin or hook would have nothing to do with it.

Mr. Cherrybomb says the gun will close on a thin sheet of paper. That paper will compress when the gun is closed. I wonder if the gun will close and lock up if a .004" precision steel shim is inserted instead of the paper? If the gap was as thin as he described, I doubt it. Silvers

Silvers,

Some new guns will show a .001 gap between the base of the standing breach and the breach of the barrels. The gap is there to allow for clearance between the top of the standing breach and the bottom of the breach end of the barrels, upon closing. BTW, the standing breach is not 90 degrees to the watertable. If it was the gun would never close.

Phil

Phil, thanks for your reply. Yes I know the breech faces are not exactly perpendicular (90-degrees) to the water table. What the angle is really doesn't matter. What I'm saying is, if the back end of the barrels and the breech faces were exactly fitted when the gun was new, showing no light, they would probably show a slight gap at the bottom when the gun gets worn. Also saying that I really doubt every double gun ever made was so closely fitted when new that the barrels would show no light as written up by Cherrybomb. Surely there were better and lesser skilled barrel fitters. Also, I wonder if fitters in the days of yore may have had other things going on Monday mornings or late Friday afternoons, same as modern workmen. Silvers

Not all breech walls are transversely true either. Straitedge placed across near firing pins sometimes detects a rocker condition with the high pt. next to rotary bolt slot on the usual American suspects. It is absolutely amazing how thin an opening light can penetrate. Also amazing how thin a coat of nail polish will stop light from penetrating. Don't try this at home!

jack

I looked at a redone Parker one time that had a nice tight action, but there was a gap between the watertable and the barrel flats near the standing breech that you could see light through, a lot of light. I thought perhaps during the recase coloring process the frame warped or something. It was not noticable until you looked closely at the engraving on the side of the frame.