Fill me in on 7.5" uppers

[shaynster]

I'm getting ready for my first sbr and want a 7.5" upper for it. I haven't seen many topics on them, mostly 10" and 11". Are they unreliable? Any brands to avoid?

Thanks,
Shayn

 

[digitalrebel80]

they can have cycling problems due to the short gas system (can be fixed with items like the noveske KX3)

 

[stoyan79]

Mine is as reliable as any other AR, but its awful loud (even suppressed) and since .223 relies so much on velocity, it won't be as lethal. I think 10.5 inches is a good compromise for this caliber. You can go short in other calibers which don't rely as much on velocity to be lethal.

 

[madeuce50]

Tim La France perfected a gas tube set up for short barrel reliability. The shorter barrel seems to create short strokes/fte/ftf and can be picky. The 10.5set up I have seen set up on a postie m16 from Model 1 Sales ran better then the DPMS 7.5 with the same ammo and the problems were short strokes and magazine issues. The DPMS had a pig tail gas tube and the 10.5 had a custom 3bend gas tube. The 7.5 got very hot very quick and 30 round mag dumps left it smoking. The 10.5 was just as awesome but more reliable.

 

[cfl4rat]

I just finished a 7.5" pistol build which will be SBR'd down the road and so far it runs like a top! I'm running a full auto carrier and a H2 buffer with NO cycling issues.

 

[JTinIN]

Had good luck with two them, always ran a #60 o-ring under the extractor and made sure to use a buffer with anti bounce (i.e. some of the shortest pistol buffers are solid).

Worked fine on handgun and the Colt M16A1 on full or semi.