6.8 SPC upper on a 5.56 Lower

[EdLaver]

I swapped a friends 6.8 upper onto one of my AR lowers (Spikes) and I am having trouble seating the mags without a little forceable push. also it is jamming after 2 shots.

If I remember correctly, isn't it ok to put a 6.8 upper onto a 5.56 lower? What could be the problem?

Thanks,
-Ed

 

[Zerodefect]

Were you useing 6.8spc specific mags?

 

[EdLaver]

Yes sir...C Products.

 

[Tirod]

If you're seating the magazines with the bolt held back, the mag catch is probably right on the edge of being too high. File the holes in the mag, or file the catch. Neither is a popular choice.

Jamming after two shots - interesting. The mag follower may not be moving up, and the round is then held too loosely to properly feed. The follower may be binding up on something in the mag, such as a burr or spot weld.

 

[EdLaver]

Tried both Barrett and PRI mags, works fine now. The C Products mags must not like my lower, they work fine in my buddy's though.

 

[Zerodefect]

That is possible.

 

[Welding Rod]

I was going to say.... C Products mags woud be my first suspicion.