Tight threads between madbull receiver & nuprol ris

[woottonp]

Hey guys

So I've been building a custom ar15 for a few months now and finally picked up a nice receiver off here, but have run into one major issue. I can't screw the ris into the upper.

It's a mad bull stag arms receiver, and the ris is a nuprol bocca 12" rail. It went on about 2-3 full turns and became very stiff, I have since worked it back and forward and it goes about 5-6 turns now, but is maybe 2 turns of being properly seated against the barrel.

I am aware that there are different threads but the only tap I found was the mad bull one, and I would imagine running that on a mad bull receiver would be fairly pointless (unless they are different thread dimensions). I don't think it's a thread dimension issue as when inspecting the threads there is very little marking from my efforts, juat a little metal showing at the peaks of the receivers threads and some black stuff when I wipe the threads off. So basically it seems the coating on the receiver is a little too thick for the barrel nut.

Does anyone wave some tips to help free the threads up?

I've already snapped a foregrip which I was using for leverage so I don't think brute force is going to solve this one. I was thinking of running some wire wool over the area to take the tops off the thread, or just using more spacers between the barrel and the barrel nut so that it locks the barrel earlier and I don't have to worry about the tighter threads

As always, thank you!

Sent from my ONE E1003 using Tapatalk

[woottonp]

Re: Tight threads between madbull receiver & nuprol ris

in case anyone is interested I have now resolved the issue, I used a very small triangle file to work the male threads a touch, just a few times around taking a the coating off the threads, then a quick wire wool. I then ran an 800grit paper through the femal threads to take the tops of the thread down a touch.

This along with some extra washers and the Ris is fitted nicely onto the upper receiver, its still tight but goes all the way now.