Well, DANG! I have about 400+ rounds of my pet 223 load loaded: 21.5 grains IMR4198, CCI #41 primer, and A 55 grain FMJBT bullet. I had used this load since the 80s with a SP1 AR15 16" Carbine. More recently, I had been using it in a 16" barrel M4gery. Accurate and reliable load, with same POI as M193 from the 16" barrel.

The problem is that I switched to a 20" barreled platform with a rifle length gas system. Guess what? It apparently 4198 is too quick a burn for the 20". It will not lock the bolt to rear after the last round, and about 1 out of 3 times, it won't cycle far enough to pick up the next round. In a 16" system, you can't tell the difference between M193 and this load as far as noise and recoil. In the 20" system, the reload is definitely not as hot.

I don't want to pull 400 bullets of plinking ammo, so I picked up a spare rifle length buffer spring for $10. I thought I would clip about 10% off the spring, and just use it with the plinking ammo.
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