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Posted: 9/24/2004 11:13:53 AM EDT
[Last Edit: 9/24/2004 11:14:52 AM EDT by AssaultRifler]
What does the "CMP" stamped on the bbl stand for?

owner of:
Colt AR15A2 Sporter II
Colt AR15A2 HBAR
Colt Sporter Lightweight
Link Posted: 9/24/2004 11:16:33 AM EDT
"C" = Colt
"MP" = mag particle tested
Link Posted: 9/24/2004 11:20:39 AM EDT
Link Posted: 9/24/2004 11:21:27 AM EDT

Originally Posted By mongo001:
"C" = Colt
"MP" = mag particle tested

what's this "mag particle tested"?
don't know what that is
Link Posted: 9/24/2004 2:13:34 PM EDT
[Last Edit: 9/24/2004 2:13:51 PM EDT by Troy]
Link Posted: 9/24/2004 2:17:58 PM EDT
[Last Edit: 9/24/2004 2:18:42 PM EDT by mongo001]

Originally Posted By Troy:
C = Colt (B here = Bushmaster, FN = FN Manufacturing, K = SACO, etc.)

M = Magnetic Particle Inspected
P = Proof-load tested


Learn something new every day. Thanks for the correction.
Link Posted: 9/24/2004 2:48:19 PM EDT
According to this site, MP only stands for magnetic partical tested. Whose correct? Beats the hell out of me.
Link Posted: 9/24/2004 3:01:37 PM EDT

Originally Posted By Big-Bore:
According to this site, MP only stands for magnetic partical tested. Whose correct? Beats the hell out of me.

Bigger Hammer is so far out of date, I quit going there for info. They may have been up to date in 1990 or so, but not now. I would take Troy's word on this one until I saw Colt letterhead that stated something different.
Link Posted: 9/24/2004 3:03:42 PM EDT
Troy knows his stuff.
Link Posted: 9/25/2004 12:49:27 AM EDT
Troy is saying exactly what was said in the Colt courses, I would certainly cosnider it as true.
Link Posted: 9/25/2004 4:40:13 AM EDT
[Last Edit: 9/25/2004 4:43:56 AM EDT by Chuck]
Link Posted: 9/25/2004 5:04:06 AM EDT
[Last Edit: 9/27/2004 12:35:21 AM EDT by Tweak]
Link Posted: 9/25/2004 6:03:42 AM EDT

Originally Posted By Chuck:
This is semantic as the MP mark, magnetic particle inspected, or magnetic particle inspected and proofed -- take your choice, is put on all at one time after both procedures are conducted. Procedure starts with proof firing but there is no mark for just proof fired only for the complete procedure of firing and inspection.

A case could be made either way and the milspec is non-specific. Logically since proof firing is done before MP inspection the mark should be P MP or PM if it was intended to mean proofed & inspected. Regardlesss MP is the final inspection mark for a barrel or bolt which has withstood proof firing and a subsequent magnetic particle inspection.

This is from the M4A1 spec:

3.4.4 Hiqh pressure resistance. Each barrel assembly and bolt shall withstand the firing of one Government standard M197, 5.56mm high pressure test cartridge conforming to MIL-C-46936. After proof firing, parts shall be free of cracks, seams and other injurious defects as evidenced by visual and magnetic particle inspection. Proof markings. Proof marks and magnetic particle inspection marks shall be applied on barrel assemblies and bolts that have passed this test.

-- Chuck

Ok, Chuck, here's a question for you:

I personally owned and have seen other "FNMI MP 5.56 NATO 1/7" barrels - the infamous "FN" barrels that aren't supposed to be in the civilian world. Some theorized that since I actually had this FN barrel, it must have been some type of factory reject that slipped through the disposal process, but using your explanation above, which makes perfect sense to me, I'm thinking that the FN barrel I had wasn't a reject at all, as it was "MP" stamped. Now FN and Colt are two different companies, obviously, but they are making barrels to the same milspec, so I'm thinking the testing would be pretty close. Am I thinking way off base here?
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