I built my first stripped lower and just returned from the range. I need expert advice.
My 450 Bushmaster 18" complete upper from Bear Creek Arsenal is short cycling. Shooting Hornady 250grn FTX, the casing ejects, but the next ammunition will not load. I have had this upper for a few years and used to shoot it on an M&P15 without modifications to the buffer or spring.
To troubleshoot, I put the 450 BM upper onto my Black Rain Ordinance lower, and the next ammunition loaded and action cycled correctly. I then put the 5.56 Black Rain Ordinance onto my built lower, and the 5.56 also cycled correctly.
Because of this, I am assuming my carbine buffer and spring in my built lower (adjustable buttstock) is not adequate for the 450 BM action. I do not see any markings on the buffer or spring. Do I need to replace the buffer (heavier?), spring (stiffer?), or both? I am also up for any other recommendations or ideas.
Thanks in advance.
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