Hi guys! I am having a minor issue with one of my M4's and was wondering if anyone could help. This rifle is a Bushmaster Lower that I put on a Colt Upper.
The rifle is occassionally jamming with 55 Grain Wolf and 55 Grain PMC ammo. I just replaced the mag follwers with green followers in my clips. Until today I have had no significant jamming problems at all but I have not fired the rifle much until today. Since it was jamming with Wolf and PMC I decided to try some Israeli Surplus M855 62 Grain penetrator green tip in it. I had my sister in law rapid fire 10 rounds of the M855 Ammo through it and it never jammed once. It does jam with the 55 grain wolf and 55 grain PMC however. Now this rifle has a 1/7 twist in it which I understand is more for the heavier ammo. Could this be the problem? I think i've fired Wolf and PMC through it before without it jamming though.
When it jams it ejects the spent cartridge and its like it tried to feed two rounds in at once or something. Anyone have any thoughts, ideas or suggestions? Thanks!

Sounds like a double feed wich is usually a magazine problem.The fact that it jammed with brass case as well as steel kinda points in that direction.The israeli stuuf that didnt jam however is loaded to higher pressure as the wolf and PMC is loaded a little lighter this may be a factor as well.Try some 855 62 grain and some XM193 and see how it goes.Is the colt upper for small pin or has it been shimmed to take a small pin?

I found the problem. It is those new mag followers that i've installed. I tried a stand OKay Industries mag with normal black follower and it works with all ammo. Is there anything special that I should do when installing green followers? I thought these were suppose to prevent jamms better? :-(

The followers could be out of spec,whenre did you get em and is there and number marks on the bottom of it?

nope there are no number marks on em...i'm thinking of putting my black followers back in asap