Quoted:
Quoted:
Quoted: Date code, more on this later
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The extra letter in the MPC was a date code from September 95 till November 2001 Colt used the letter system to indicate the month and year of manufacture. No C was used to avoid confusion A thru Z then A thru Z with a line below the letter code then cycle three was A thru Z with a line below the Date code letter
The math is a pain in the ass, wish someone had a chart for this shit
For what it's worth, most bolts I've seen like this have used the letter G
September of 95 ---- MPAC October of 97 -------MPAC November 2001 ---MPZC with a line above the Z
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thanks YardDogOne! anybody has a complete chart?
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Yes
From Black Rifle II
The date codes were used from 9/95 to 11/2001 with a letter between the P and C to indicate the month manufactured.
They (colt) initially cycled through the entire alphabet ending with the use of MPZC for bolts made during September 1997 (to avoid confusion, the letter C was not used in the month code system)
Colt then went through the alphabet again differentiating the second cycle of the alphabet with a line under the month code letter.
Cycle 2 thus began MPAC in October and MPZC for November 1999.
A 3rd cycle began December 1999, once again beginning with MPAC only this time the line was above the month date code letter.
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Therefore, it is possible to determine the month and year a bolt assembly was manufactured as long as it was made between 1995 and 2001.
other Bolt Code information (also quoted from Black Rifle II)
MP - Magnetic Particle Inspected and Proof Tested - Manufactured by Colt
MPC - Magnetic Particle Inspected and Proof Tested - Manufactured by Colt
MPD - Magnetic Particle Inspected and Proof Tested - Manufactured by Diemaco*
MPF - Magnetic Particle Inspected and Proof Tested - Manufactured by FNMI
MPF - Magnetic Particle Inspected and Proof Tested - Manufactured by FNMI (subcontracted)
MPF - Magnetic Particle Inspected and Proof Tested - Manufactured by FNMI (subcontracted)
MPN - Magnetic Particle Inspected and Proof Tested - Manufactured by National Aerospace
MPR - Magnetic Particle Inspected and Proof Tested - Manufactured by Rock Island Arsenal
* Diemaco also marks a 5-digit batch number on each bolt beneath the MPD markings
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That is good stuff, thanks for posting it.
I suppose that if your bolt has the extra letter you can tell when it was made, to the month, but just because a bolt was made during that time frame does not mean it will be marked like that. For example, the 2000/2001 batch of RO921HB's that went to SFG's did not have four letter coded bolts, they were marked MPC.
On the other end, all the 1995 bolts I have seen are marked:
MP C
or:
MP
C
But none with the four letters.
What does it mean?