Long time lurker here, but finally decided to join and post.
I've got a 16" 450 with an A2 stock. I was having alot of FTFs....didnt matter what mag I used, and it did it while running factory ammo and/or my reloads. The bolt would come back and stop at the rear position and wouldnt strip a fresh round and chamber it. A quick pull on the charging handle would get me back in business, but that obviously wasnt a desirable scenario. So....
A buddy of mine ordered a .458 SOCOM upper from RRA. With the upper came 2 new buffer springs- one for carbine stocks and one for A2 stocks. Since he was running a carbine stock I snagged his A2 spring, and now my feeding issues are a thing of the past. Havent had a single FTF after 100+ rounds of factory and my reloads. The only difference I can tell in the spring is that it appears stiffer than my standard spring, and about four inches of it are painted red. (Or green for the carbine version) Either way, I figured I post this in the hopes it helps someone else out. I ordered a new set from RRA to replace the spring I swipped from my buddy....cost was $9 for both springs.