I’m currently having failure to feed issues due to what I assume is short stroking.
Rifle specs:
Rainier Arms match barrel 18” mid length gas, .223 Wylde
BCM full-auto BCG
LMT defender 2000 lower with stock spring and CAR buffer
All mags used are 30 round windowed gen 2 P-Mags.
My rifle had about 900 rounds on it shooting mostly Hornady .223 55 grain soft points, and black hills remanufacture .223 55grain soft points before I had any issues.
On the first range trip I had issues I was shooting Fiocchi 69 grain SMKs for the first time and had switched out my CAR buffer with an H buffer. About half way through my first mag it failed to feed. I cleared the round and two rounds later the same thing happened. I then removed the rounds from my mag and reinserted the empty mag into my gun. For the next 30 rounds I fed one round at a time to see if it would lock back and it did every time. I assumed the issues were from low power ammo, too heavy of a buffer and the fact my gun hadn’t been lubed in a while.
On the second range trip I had gone back to a CAR buffer shooting the same ammo and re-lubed my BCG. This time I got through one mag and half way through the next one before I had a failure to feed. I cleared the round added lube to my BCG and made it about five rounds before the same thing happened. For the next eight rounds or so I kept an empty mag in my rifle treating it like a single shot and seeing if it would lock back, and it failed to lock back once.
I have checked my gas rings, I seen no chips, dings or scores on them and they passed the “drop” test.
My gas key is tight.
I removed my gas block to check alignment; it was perfect.
My buffer spring measures 10 3/8 inches.
I did see evidence of some slight gas leakage were the gas tube goes into the upper but it didn’t look excessive or abnormal.
Where the gas tube seals in the gas block however, I do have a very dark patch that’s about 3 ½ inches long, telling me there might be excessive gas leakage.
I also noted that the Fiocchi 69 grains SMKs are only doing about 2735fps. Compared to federal and Winchester with the same bullet doing 2950fps and 3060fps.
I would like to know if there is anything I could do to get my rifle to reliably cycle the Fiocchi SMKs, or if I missed something to help further trouble shoot what is wrong.



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