Reaction of Luger barrel to torque of firing?

sheepherder · 09-25-2010, 07:17 PM

I had an interesting email today...

Rich -

A Luger collector told me that one theory regarding Lugers is that over long periods of time the barrel can unscrew slightly due to the physics of the bullet going down the barrel.

In other words, if you fire one enough, it will start to unscrew the barrel from the receiver. And supposedly this accounts for the witness marks on the barrels and receivers which often do not line up properly.

In your experience, have you ever heard of such a thing - on a Luger or any other gun with a rifled barrel that is screwed into a receiver?

Sounds a little far fetched to me, but I thought in your experience you might have heard of such a thing.

I had never thought about it...but since I had a bare receiver and a loose barrel sitting on my bench, I tried a little experiment. I oiled the threads, screwed the barrel in 2 threads, and ran a cleaning rod with 2" square patch folded twice on it down the barrel from the rear (as a bullet would be traveling). I held the rod steady so it wouldn't turn. It actually screwed the barrel *in* a quarter turn, not out.

The Luger barrel is threaded 20tpi with a right-hand thread, like a bolt you might find in your local Ace Hardware store. It screws in in a clockwise motion.

I suppose if the barrel was loose to begin with, the vibration of shooting *might* unscrew it...

Looking from the rear, the Luger rifling seems to twist clockwise. I'm guessing this is what is called a "right hand twist" in the specs...I don't have a book detailing a lot of barrels, just Nonte's 'Pistolsmithing', and it lists 18 pistols (mostly revolvers) all having right hand twist (the Luger is one of them).

It is interesting that although I was applying pressure down the barrel (rear to front; direction of bullet travel), the barrel actually turned in *against* the pressure...

Comments on the collectors theory are welcomed...Flames welcomed...cries of "burn the heretic!" welcomed...

09-25-2010, 07:17 PM	#1
sheepherder Lifer Lifetime Forum Patron Join Date: Feb 2009 Location: ...on the 'ol Erie Canal... Posts: 8,197 Thanks: 1,416 Thanked 4,462 Times in 2,336 Posts	Reaction of Luger barrel to torque of firing? I had an interesting email today... Rich - A Luger collector told me that one theory regarding Lugers is that over long periods of time the barrel can unscrew slightly due to the physics of the bullet going down the barrel. In other words, if you fire one enough, it will start to unscrew the barrel from the receiver. And supposedly this accounts for the witness marks on the barrels and receivers which often do not line up properly. In your experience, have you ever heard of such a thing - on a Luger or any other gun with a rifled barrel that is screwed into a receiver? Sounds a little far fetched to me, but I thought in your experience you might have heard of such a thing. I had never thought about it...but since I had a bare receiver and a loose barrel sitting on my bench, I tried a little experiment. I oiled the threads, screwed the barrel in 2 threads, and ran a cleaning rod with 2" square patch folded twice on it down the barrel from the rear (as a bullet would be traveling). I held the rod steady so it wouldn't turn. It actually screwed the barrel *in* a quarter turn, not out. The Luger barrel is threaded 20tpi with a right-hand thread, like a bolt you might find in your local Ace Hardware store. It screws in in a clockwise motion. I suppose if the barrel was loose to begin with, the vibration of shooting might unscrew it... Looking from the rear, the Luger rifling seems to twist clockwise. I'm guessing this is what is called a "right hand twist" in the specs...I don't have a book detailing a lot of barrels, just Nonte's 'Pistolsmithing', and it lists 18 pistols (mostly revolvers) all having right hand twist (the Luger is one of them). It is interesting that although I was applying pressure down the barrel (rear to front; direction of bullet travel), the barrel actually turned in against the pressure... Comments on the collectors theory are welcomed...Flames welcomed...cries of "burn the heretic!" welcomed... Attached Thumbnails __________________ I like my coffee the way I like my women... ...Cold and bitter...