FNG with a new M-4

[PaulnPats M-4]

Hello everybody, New guy with a question about his new home built M-4. I been reloading for a long time, and put together a M-4 using an Aries upper, it shoots military and commercial ammo just fine, but my hand loads are a different story? I found some IMR-4198 and have used 22 grains with a 55 gr. FMJ bullet and military cases and a 41 CCI primer, and I am getting a failure to feed (short stroking) very frustrating. I changed out the buffer to an H-2, still failure to feed. Should I try to find a different powder? I have a little IMR-3031 and 4895, any help would be appreciated, I am no newby to the weapon as I carried one in Viet Nam years and years ago. Thank for any help

[markm]

20.4 is shown as MAX with a 55 gr Soft Point. That's odd. Is this a piston upper?

Also... does it FEEL like it's cycling soft or weak? I'm wondering if the bolt isn't running too fast and causing bolt over failures.

[PaulnPats M-4]

No sir, no piston upper

[markm]

Exactly what failure to feed condition are you seeing? Is the bolt missing the back of the next cartridge? (bolt over)

Also... read your brass and primers. Are the primers flattening out pretty good? Are there any shiny swipe marks on the head stamp? Since your load is over max, I'm thinking it may be excessive bolt speed that's causing your feed issues.

[Rascally]

Does the bolt lock open after firing the last round? If so, it could be a bolt over condition. If not, it could be a short stroking condition. Or it could just be a bad magazine spring.

[markm]

Failure to lock back can be from a few things. Short stroking OR Over gas/excess bolt speed to where the carrier is out running the bolt catch....

I doubt he's got bolt catch or mag issues since the gun functions on other ammo.

[PaulnPats M-4]

Thank you for the replies, the P-mags all work with the military ammo (Federal 55gr.) there is no marks on the rim, but the primers are flat, I'm using a H-2 buffer, and a 10 1/2 carbine spring. The bolt will NOT pick the new round in the mag. The upper is 5.56 with a 1 in 7 twist, thinking about reducing the load to 19 grs. and see what happens? Have used a reduced power spring, and a Dave Tubbs spring, still did not function with my hand loads???

[markm]

That is strange. Is the factory ammo the is working Black box AE223? or Tan box XM193? IMR-4198 is a pretty fast burning powder. If you want to really change it up, try the 4895. 4895 is a bit slower burn and may give you a better gas flow in the gun.

You know what?... that fast powder and those hot #41 primers might be giving you and early peak pressure that your gas system doesn't like. One of our members here was using H322 which is almost as fast as your 4198, and when he switched primers from #41 to a milder WOLF SRM primer, his short strokes went away. Without going out to buy a bunch of different primers, I'd say run the 4895 for a test load.

[PaulnPats M-4]

Scott, it's the tan box XM-193, I'll switch to the 4895 maybe about 24 gr. and try it out next week at the range, thanks a lot. Paulie

[PaulnPats M-4]

I just wanted to take the time to thank you all for your replies, Markm you hit it, went to the range yesterday with some rounds loaded with IMR-4895,
BINGO! weapon functioned flawlessly using 50, 55, 65, grain bullets. Not bad accuracy too, thank you very much, I owe you all an adult beverage.

[Maddmax]

I've been using IMR4895 for years (since the mid ? 70's) and have always had great results with it. Measures great and I like the burn rate.