My latest rifle build is going to be a takedown rifle using the LEO Takedown system. For this to work correctly, I need a nice smooth easy barrel to upper fit so the barrel can be easily removed. After doing some test fitting last night, the barrel to receiver fit is VERY tight. The barrel will not seat all the way. If this was a normal build, no problem, a little muscle/heat/cold/lube and I would be ok, but in my situation that's not going to work.

So, I need to remove some material to get this to fit correctly. Should I lightly sand the ID of the receiver or the OD of barrel extension or maybe a little of both? Any other ideas? Any help would be greatly appreciated.

Chris

I'd say do the barrel extension simply for the ease of doing it on the OD (outside diameter).

But, it might help to know which piece, if any, is out of tolerance.

Mark it (markon or magic marker) and look for 'tight' spot or just smooth or reduce down as suggested.

Just ram it in there a couple hundred times 'til it loosens up.

All joking aside, I'd personally prefer to smooth out the I.D. of the receiver similar to how people hand lap scope rings. Only doing a couple passes at a time before re-checking fit.

I expect that your upper is Anodized, a chemical process that produces a thin and extremely hard layer of aluminum oxide. Opening up the ID on the upper will remove that protective layer. To me the obvious answer is to reduce the OD on the barrel extension. As someone with access to a Lathe it's also the far easier choice.

One thing about your plans does concern me. That is the effect on accuracy. I have always believed that the ideal fit between upper and barrel is one that requires a bit of force to get everything "home". That way there aren't any vibrations going on between upper and barrel while a round is transiting the barrel. With no experience at all with the system that you are using I'm just speculating. Just bringing it up as a talking point. Love the idea of an easy barrel swap and don't know where the pitfalls of building one of these rifles would be.

So based on the feedback here and from additional research, it seems there was about of 50/50 split on what part I should take material from so I decided to do little from both parts. I lightly sanded the barrel extension and inside of the upper. I used 800 grit sandpaper and went very slow checking the fit frequently. With just a little bit of sanding on both parts I was able to remove just enough material to get a nice snug fit that easily slides in and out. The anodizing on the receiver is still intact. In fact you can’t even tell it was sanded. On the barrel extension it removed just a tiny bit of the finish. It should be good to go know. Thanks for all the help.

Chris