Thursday, February 14, 2013

Krupa's Guide to AR-15 Parts Breakage...

So a lot of folks got their AR-15 on... Might be a good idea to hunt for some spares/know what needs to be tuned if necessary.

John Krupa, Director of Training for Team Spartan and former LE Training Director for DSArms, shares years worth of wisdom below:


Parts wear & breakage will always be an issue for anyone that is regularly running their rifles thru rigorous use.
On the AR-15 / M-4 type rifles, common parts breakage / wear is a regular occurrence on extractors, bolt rings (gas rings), firing pin retaining pins and firing pins. 
We have (10) DS Arms ZM4 5.56 rifles we have been using as student loaner rifles in our classes and live-fire demos since they were issued to us in 2005. Most of those rifles have seen in excess of 25,000 rounds - easily!! 
In running these rifles - HARD - over this long a period of time, we've seen at least a 1/2 dozen extractor failures, broken / severely worn firing pin retaining pins in virtually every rifle and bolt ring failure & replacement on all rifles - 3X over! 
Surprisingly, I've experienced parts breakage on parts that don't break as often, but have been brought to light as parts to consider inspecting during regular preventive maintenance inspections and having extras on hand:
  • We've had several charging handle failures where the roll pin that holds the latch to the handle failed. The aluminum hole that holds the roll pin in place becomes elongated as a result of extensive, aggressive use, resulting in failure.
  • At least (4) buffer failures where the roll pin that holds the rubber buffer to the buffer housing comes loose, resulting in the rubber buffer fraying & shredding due to misaligned contact with the buffer spring.
  • Multiple cracked bolt catches, most likely broken from stress damage due to inexperienced students violating the rule of dropping the hammer forward while the lower receiver is separated from the upper during field stripping & cleaning.
  • We've broken 8 of 10 RRA 2-stage hammers, which all of our rifles were originally issued with! Most of these hammers broke within 5,000 rounds! I definitely DO NOT recommend competition fire control groups in serious rifles used for duty / personal defense. (As preached by John Farnam)
  • We've only had (2) firing pin issues, both of which the point of the firing pin became elongated, resulting in it dragging on the inside of the firing pin hole on the bolt, resulting in failure to fire stoppages.
Also, keep in mind that your not just counting rounds fired or cycled through the rifle as the overall reason of parts wear. Any rifle programs that have any level of dry-practice / dry manipulation of the rifle counts as wear reps as well.
It is not uncommon for rifles to see dry practice manipulations meet or exceed actual live-fire round count! ALL cycling - whether it's live-fire reps or dry-practice reps - will lead to parts wear, and eventually contribute to parts breakage.
Bottom line is, if your going to play rough with your toys, plan on breaking stuff!