Bought the forearm in July, haven't been able to install it yet.
Took it to a gunsmith in South Jersey today.
He said I'm missing parts.
Before I get to his diagnosis, I have some questions:
Has anyone installed a YHM freefloat 4 rail forearm on an AR?
If so, did you remove the whole barrel or did you remove the front sight only?
The DPMS rimfire upper has no gas tube, so would you say one way is easier than the other?
The YHM directions say to remove the front sight.
The directions also talk about a "barrel nut" and "jam nut."
Here's what I have:
In summation, I'm not sure what to do next.
Arright, NASCAR's on. Gonna boogie.
Your gunsmith is wrong. Most "gunsmiths" I've met are nothing more than gunshop commandos who have access to some punches, screwdrivers and a drill press.
As far as your gun, all the parts are there. That's all the parts that the YHM FF tube has. The barrel being "recessed" inside the upper has nothing to do with the tube. Its held on by the barrel nut, which will be replaced by the thick fat threaded barrel nut of the YHM tube. The jam nut is there to "jam" the ff tube tight (think using two nuts on a threaded rod, by cranking them in opposite directions, you can make it really tight).
Now, I hope you have access to a upper receiver block and a barrel wrench, because its what you will need to do this job. Refer to FALARAK's link for instructions on how to disassemble a regular upper. FALARAK's FF tube install thread shows you how to install a float tube. As far as the barrel starting a bit behind the ejection port, its fine. Just imagine that your barrel has a longer extension Remove and reinstall in the same manner.
Oh, before and after pics are mandantory
ETA: Make sure you can remove the muzzle device, if one is present because you will have to remove the FSB. Read up on punching out the FSB taper pins here.