Bought a SEI socom 16 threaded gas cylinder lock so I could replace the stock muzzle device.

The original one came off no problem.  However the new one won't thread. It starts to thread and within 10 degrees it acts like it's going to cross thread. I swapped back to the oem and it threads on no problem. I can't see any issues with the threads on either.

Assuming I'm going to have to send it back to fulton. But here's a link to what I bought. I shouldn't have compatibility issues putting this on a stock socom 16 should I?

SEI gas cylinder lock

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Should have no issue threading it on. I definitely wouldn't force it either. Should thread on easily.

Fulton emailed me back and said the SEI locks have always been very consistent but that they've seen the Socom 16 threads vary slightly. He said he's willing to bet its my rifles threads and not the lock.

He said I could return it if I want.

Not sure how to confirm that. And if my rifle threads are off I'm not sure how to go about getting one of these on. I imagine you'd have to find a tap or die that's the correct size.

When I was messing with it last night it didn't feel like it was crossthreading. It almost felt like the threads were just slightly large. I was able to get about 1 rotation with oil by hand but I wasn't going to force it and wreck threads.

Edit: I called SEI. He said they no go gauge every single one, but it's well known that springfields socoms have been having issues with varying threads. He said he's installed alot of them and it's a coin toss whether it'll thread on. He said it's a non standard pitch and getting the right die is expensive.

However he said he has never failed getting one on by lightly taking down the barrel threads with emery cloth. So I suppose that's the route I'm taking.

Boys over at Smith were correct that seemed to work well.

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Nice! Glad there was an easy resolution, and now in the future hopefully it helps others as well.