Rifle failing to feed on 75 gr ammo

[farmhard]

169 resized.jpg168 resized.jpgI have an upper with 16 match grade stainless barrel from a reputable manufacturer that has been reliable for almost 1000 rounds. lately it has had problems feeding the primary ammo that I feed it(hornady 75gr superformance), the round will hang-up in the barrel extension lugs just above the feed ramps. it will also fail to feed 75gr hornady from a bolt locked to the rear. I have mounted it on multiple lowers and used different magazines with the same results. it will feed 55gr fmj with no apparent issues. Any info or advice would be appreciated.

[Iraqgunz]

Pics would obviously be beneficial.

[farmhard]

I will try to post some tomorrow.

[ColtSeavers]

Does the barrel extension have m4 feed ramps? Does your upper receiver have m4 feed ramps? Check to see if somehow the ramps no longer line up or if there's any other problem with them. Is it always the same side that fails to feed? Start looking at that ramp first.

[farmhard]

The upper and barrel have feed ramps the cartridge gets stuck where the feed ramps transitions to the extention lugs.

[Singlestack Wonder]

The upper and barrel have feed ramps the cartridge gets stuck where the feed ramps transitions to the extention lugs.

Can you post a picture with the bolt open without a round and zoom in where the receiver feed ramps meet the barrel extension feed ramps?

[farmhard]

171 resized.jpg here is a unobstructed view of the ramps

[cbx]

Which side hangs up? Are the ramps smooth? Have you swapped buffer spring from another rifle to see if that fixes it?

Reread op. Do you have another carrier you can try?

[MegademiC]

Looks like a shortstroke. Has your 55gr ammo been 5.56 and the 75gr .223?

[farmhard]

Which side hangs up? Are the ramps smooth? Have you swapped buffer spring from another rifle to see if that fixes it?

Reread op. Do you have another carrier you can try?

seems to happen more on the right side. I've had the same results with a new bcm carrier.