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 Barrel Markings
Grey_Ghost  [Team Member]
11/30/2005 11:18:37 AM
My 20" barrel has marking as follows

C MP B

is c for colt or chrome
MP I know what that is
is B for Bushmaster

Thanks


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scottryan  [Team Member]
11/30/2005 11:46:16 AM

Originally Posted By Grey_Ghost:
My 20" barrel has marking as follows

C MP B

is c for colt or chrome
MP I know what that is
is B for Bushmaster

Thanks





C = Colt

M = Mag tested
P= Proof fired

B= Fully chrome bore and chamber
Grey_Ghost  [Team Member]
11/30/2005 12:01:14 PM

Originally Posted By scottryan:

Originally Posted By Grey_Ghost:
My 20" barrel has marking as follows

C MP B

is c for colt or chrome
MP I know what that is
is B for Bushmaster

Thanks






Thanks Scott
That's what I was told Ijust wanted to be sure



C = Colt

M = Mag tested
P= Proof fired

B= Fully chrome bore and chamber

a38337  [Member]
11/30/2005 12:04:11 PM
scottyryan is correct.

Colt proof test their barrels, barrel extensions, and bolts by firing a 75,000 psi (normal ammo generates about 50,000 psi) proof load to test these parts, discards any that don't pass, then inspects the remaining parts by Magnetic Particle testing to find any hidden defects, and dicards the ones that don't pass.

This testing process is required by uncle sugar, and is one of the things that you pay extra for when you buy a Colt, as they do it to all their AR15/M16 rifles.

Bushmaster stamps their barrels "BMP", but it doesn't mean anything.

How old is this barrel? Usually you don't see a "B" on a Colt barrel, except for the older ones.

SF


Grey_Ghost  [Team Member]
11/30/2005 12:16:12 PM
Don't really know how old it is .I bought it about 4 yrs ago.
It has The A1 upper and the lower is a PWA.

Thanks for the info.
Jelly  [Member]
11/30/2005 1:38:48 PM
The barrel was most likely made in the early 70s up to around 1972 or 1973.
WIZZO_ARAKM14  [Team Member]
11/30/2005 6:24:39 PM

Originally Posted By a38337:
scottyryan is correct.

Colt proof test their barrels, barrel extensions, and bolts by firing a 75,000 psi (normal ammo generates about 50,000 psi) proof load to test these parts, discards any that don't pass, then inspects the remaining parts by Magnetic Particle testing to find any hidden defects, and dicards the ones that don't pass.

This testing process is required by uncle sugar, and is one of the things that you pay extra for when you buy a Colt, as they do it to all their AR15/M16 rifles.

Bushmaster stamps their barrels "BMP", but it doesn't mean anything.

How old is this barrel? Usually you don't see a "B" on a Colt barrel, except for the older ones.

SF





Not true anymore according to this guy from Small Arms Review. It's on the 2nd page where he gets confirmation that Bushy tests every barrel.

HERE

WIZZO
Ekie  [Team Member]
12/4/2005 5:34:57 PM

Originally Posted By scottryan:

C = Colt

M = Mag tested
P= Proof fired

B= Fully chrome bore and chamber



That is what the markings mean on a USGI barrel. The MP marking is a required proof mark found on USGI service rifle bolts and barrels since 1967.


Originally Posted By WIZZO_ARAKM14:

Not true anymore according to this guy from Small Arms Review. It's on the 2nd page where he gets confirmation that Bushy tests every barrel.

HERE

WIZZO



a38337 is correct, the markings on Bushmaster bolts/barrels are not proof marks, they are there to simulate proof marks. Neither Bushmaster barrels or bolts are proofed, but Bushmaster has managed to fool the public with carefully worded ad campaigns in the printed media such as the SAR article cited. Note there is no mention of actually doing the proof work, but mention of the markings.

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