Feeding difficulty with a Rock River upper

[LRRiflemanSNJ]

About 12 years ago, I purchased a Rock River barreled upper to build a space gun. Like a fool, I replaced the forearm to accommodate an adjustable hand stop as part of my space gun project before test firing the upper. . After a 5+ year interruption in the project, I am back on task.

The problem I have encountered, is that when I feed rounds from the magazine, my ammo is not feeding, but catching on the HPBT tips and jamming. The feed ramp collar is properly aligned, due to the alignment pin. As it stands, this rifle can't be used in rapid fire stages.

Can anyone help shed some light on what might be the problem?

Thanks!

 

[EWaugh]

Have you tried other brands of mags.
I Would also polish the feed ramps.

 

[Dusty Stevens]

Cratex on a dremel will fix it

 

[Ggmac]

Do you have m-4 feed ramps on your lower and not on your barrel ( extension ) .
It'll happen most of the time .
Pm me if needed.

 

[Stumpy1]

I missed beating GGMac by 'this much'

Hope this helps.

Frank

 

[Ggmac]

Hey Stumpy at least you know how to post pics ! A pictures worth a million of my words .
Gary
Ps I guess we should know what cal and what mag and lower .

 

[LRRiflemanSNJ]

This is a "pieces" project.
Lower is a Bushmaster XM15 acquired somewhere around 2000.
Caliber is 223.
The magazines that I used were the Colt 20s that I used with my service rifle.
The complete upper is a Rock River Varmint, 24", 1:8".

 

[pdhntr]

IF the hollow point is catching the back of the barrel, just under the chamber opening, the easiest way to solve the problem is to seat the bullets in .005 more until they do feed.

If for some reason you can't do that, then Dusty is the man with the plan.

Jim

 

[Ggmac]

Do you have a m-4 lower and a std barrel extension ? The pic tht Stumpy posted will determine if that's your problem !