Inland 2 Rivet to 4 Rivet Handguard Changeover

From memory, NPM used (at different times in production) a P proof only, a P and punch and a punch only.

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Originally Posted by W5USMC

I would bet that there is a NPM Punch mark also on that barrel, Marlin used there own "P", agree decent price so far. I also love NPM's!

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Mine has an IBM barrel and it has the P (probably from IBM) with the NPM punch mark near the P.

It has always seemed weird to me to screw a new barrel onto a test receiver and then without chambering the new barrel, fire a proof round and mark said barrel with a P before unscrewing it and packaging it for shipment. Was that the way they did them Wayne?

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Originally Posted by DaveHH

It has always seemed weird to me to screw a new barrel onto a test receiver and then without chambering the new barrel, fire a proof round and mark said barrel with a P before unscrewing it and packaging it for shipment. Was that the way they did them Wayne?

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No Idea how the barrel manufacturers proof fired barrels. (vise, goggles, gloves, hammer and nail? :)) CCNL's 199, 371, 336 and 384 all have good info on the barrel proof marks. Apparently from a Carbine Inspectors meeting held on 21 Sept 1942 it was stated that every barrel manufactured on a prime contract must be proof fired at the point of manufacture, these barrels were proof marked again by the prime when they test fired the completed carbine. This requirement was eased up a bit sometime in 1943 where only barrels made for spares would need to be proofed by the barrel maker at the point of manufacture and the barrels going to prime contractors would only need to be proofed by the prime when the carbine was assembled.