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Posted: 4/2/2006 3:59:11 AM EDT
I tried a search but came up empty handed. Just wanted to know the significance of MP testing. What I am referring to is the MP stamping found on Bushmaster, Colt, etc. barrels right next to the 1/7 or 1/9 twist rate indication. What are they testing the barrel for? Thanks in advance.
Link Posted: 4/2/2006 4:23:40 AM EDT
Google "Magnetic Particle Inspecting", a procedure used to locate cracks.
Link Posted: 4/2/2006 5:57:43 AM EDT
[Last Edit: 4/2/2006 6:04:37 AM EDT by redfisher]
Magnetic Particle Testing


eta: the short story to MP testing is that it is a step in manufacturing metal parts/products that gives the best assurance possible that the part does not have stress fractures that could be the source of failure when the product is used - or used in demanding circumstances

You do not have to test, and testing does not make a product better in any way - it is just the best way to measure if the part's metallurgic integrity is intact

Call it Insurance.

Link Posted: 4/2/2006 7:14:24 AM EDT
Normal operating pressure for 5.56 is about 50k psi.

Colt uses a special proof round (75k psi) to test the barrel, barrel extension, and bolt.

They then discard any parts that fail.

Then the use MP testing to detect hidden flaws and discard those parts.

While bushy stamps their barrels BMP, this does not mean anything.

The test process is important, considering you have 50k psi going off in front of your face.

This is also part of the extra cost of a Colt - you get a higher quality product due to the testing.

Link Posted: 4/2/2006 7:26:40 AM EDT
Bushmaster tests samples of a given lot not every one individualy.I have a 16" barrel that has over 22,000 rounds through it through the years..firing at varios speeds fast slow what have you and it still groups well at 100 yds and no failure what so ever.MP testing does not mean the part should be more.Look at CMMG they MP test l;ike colt does but ther SOCCOM medium weight barrel is about $200 less and its the same steel and same testing..go figure.
Link Posted: 4/2/2006 7:48:28 AM EDT

Originally Posted By a38337:

The test process is important, considering you have 50k psi going off in front of your face.

This is also part of the extra cost of a Colt - you get a higher quality product due to the testing.





Exactly - think of all the cases of Bushmaster rifles that have failed because their barrels blew up. Given the tens of thousands of rifles that Bushmaster sells every year, their lack of MP testing is undoubtedly leading to many, many cases of such catastrophic failures.




Link Posted: 4/2/2006 8:56:44 AM EDT

Originally Posted By DK-Prof:

Originally Posted By a38337:

The test process is important, considering you have 50k psi going off in front of your face.

This is also part of the extra cost of a Colt - you get a higher quality product due to the testing.





Exactly - think of all the cases of Bushmaster rifles that have failed because their barrels blew up. Given the tens of thousands of rifles that Bushmaster sells every year, their lack of MP testing is undoubtedly leading to many, many cases of such catastrophic failures.







+1 I hate it when my Bushie/RR/Armalite barrels detonate during a trip to the range

CLOT can/will continue to charge exhorbitant prices for their firearms b/c there are enough Kool-aid drinkers that believe a horse guarantees them magikal powers
Link Posted: 4/2/2006 11:13:59 AM EDT
The USGI MP marking on bolts and barrels means that component has been fired with an M197 high pressure cartridge (proof) and has been magnetic particle inspected to spot flaws. This marking has been in use on USGI weapons since about 1966.

The MP marking on non USGI weapons varies in meaning. Typically it means that part might have been magnetic particle inspected. At least one manufacturer claims the MP marking on their barrels has the same meaning as the USGI marking even though they skip proof testing.
Link Posted: 4/2/2006 11:34:48 AM EDT
MP testing is for detecting metallurgical flaws.

Modern day fabrication and computer aided design has muted the necessity of MP and proof loads. The fact that we don’t see barrels and bolts blowing up in shooter’s faces illustrates this perfectly.

Nice to have? Yes. Little bit of insurance for the cautious? Certainly. Absolutely necessary? Not by any means, but I can understand why the military requires it
Link Posted: 4/2/2006 1:35:46 PM EDT
Thanks for the responses... Just wasn't completely sure what MP testing was all about, now I have the idea.
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