Just got a call from a friend who is training officer for a mid-sized agency that issues M4 carbines. They are trying to shoot steel targets with the Federal frangible rounds and having problems with reliability. Seems there is a lot of blow-back into the locking lug area from only 2-3 shots, then either the case gets stuck, or the next round won't completely chamber. They also have some of the Precision frangible ammo, but it is doing about the same thing so far.

Yes, they are making certain the rifle is clean and properly lubed when they start...2-3 rounds and that's it...no workee no more. Gas tube & bolt seem to be fairly clean after the shots...just crud in the lug area and chamber. Some cases are stuck pretty good...enough that they cannot be extracted by working the charging handle by hand.

These are Colt M4's with 14 1/2" barrels...factory new.

Anyone here have any observations, experiences or opinions on what is happening?

Troy;

This is second / third hand info at this time...I am going to get a box or two from him and see for myself...but his description is that it includes both brass shavings and powder residue for sure. He is uncertain about bullet residue...IIRC these are powdered zinc alloy bullets...but seems to feel it, too, is there.

I wonder if the decreased weight (29gr. I believe) and increased velocity (I have no idea what it would be) are combining to unlock the action somehow before the bullet has left the barrel? But would that account for brass shavings? Maybe the shavings are coming from the extractor pulling through the case when it sticks in the chamber?

I shot a few rounds of this stuff years ago when Federal first released it, but none since, and I an completely unfamilar with the round that Precision is making.

Your friends department needs to get ahold of the ammo companies they are dealing with.  Did they have the same problem when they T&E'd the ammo?  When I ran .223/ 5.56 frangible reliability tests I had zero problems with any.  I believe the company would be interested, and I have always found the reps to be very helpful, even if it means recalling and replacing large amounts.

We had similar problems with another company. I got ahold of the company and they fixed the problem. We've have good luck with TTI Armory ammo.