buffer tube help needed

[ZeroDistortionNow]

Is there a difference in thread pitch between mil-spec tubes and commercial tubes?

My delema is this...

I have 3 DSA buffer tubes and 2 different castle nuts and neither nut will go on any of the three tubes

I have cleared the threads a few times on the nuts but they thread on about 2 or 3 turns then stop...

[Fireglock]

Not supposed to be any difference you would notice. I just used a RRA castle nut on a BCM milspec receiver extension and it went on fine and tightened fine on my Sun Devil lower. And conversely I installed a Vltor milspec RE on my RRA 18 months ago and it worked fine as well.

[ZeroDistortionNow]

Oh, forgot to tell you that it threads into the RRA receiver just fine

[Quib]

Unless the threads were not cut to spec on either the Castel Nut or the Receiver Extension, the Castel Nut should spin on fairly freely.

Are you using grease on the threads? The -23&P calls out for grease on the threads of the Receiver Extension. Grease will help prevent galling between the Receiver Extension and Lower Receiver during installation.

Perhaps a bit of grease as lubrication is all that’s needed to get the Castel Nut to thread onto the Receiver Extension? New Castel Nut, mated with freshly cut and anodized threads of a new Receiver Extension, may be causing a tight fit.

I personally would try a bit of grease first. If things still felt extremely tight and it seemed like galling was about to take place, I’d stop there and request a return/exchange from the dealer where the parts were purchased.