Fixing old Colt AR Lower to new RRA Upper

[Tarkus]

I would like to know if anyone is having this problem:

I have an old Colt AR-15 with the large hole/screw to attach the lower receiver to the upper receiver (not a pin).

I bought a "modern" RRA upper, and an adapter for the difference in size of the hole, but it is never well "fixed", i.e. the screw gets loose after I shoot a few rounds, so the upper and lower receivers are not well fit together.

Also, when I clean the rifle, I have the opposite problem, I can't open more than 40 degrees of angle.

Anyone has a solution for that ?


Thanks in advance.

 

[Gunnerlove]

Changing to a big hole upper or a small hole lower would fix the problem.

 

[Grizzlypeg]

I have an old colt lower with a modern upper, and an offset adapter at the hinge. The only way to tighten the screw is by turning the nut, not the screw itself, which because of the offset will only turn slightly. Hope this helps.

 

[Tarkus]

Thanks for the tip. I'll try that.

 

[Farmboy]

We have the Daniel Defense Big hole uppers in stock.

Located here on the website.