This is spinoff of the thread welcoming Josh but I thought it deserved a new thread.  I am waiting on my 22Sparrow for now I plan on using a .22 conversion on my M4gery until I get my Ruger threaded and get a dedicated .22 upper.  

Josh indicated that the threads on a regular AR barrel are too long and need a spacer.  I'm assuming this spacer just takes up enough space to make the exposed threads .400?

Next silencerco's website says that there are two ways to thread for a sparrow.  One way is to "engage the o-ring"  Is this o-ring internal to the can?  What are the advantages to doing this? (I assume less debris on the threads making it easier to get off)  

Finally I can't seem to get the prints for threading for the o-ring engagement to download off the site.  Is there another way I can get them?  Thanks alot.

Weird, I can't download them anymore either. Getting a 404 error.

O ring just keeps the threads cleaner.

I want my sparrow. Hurry ATF!!!

I'm sure Josh will be along shortly to answer your questions, but I believe the purpose of the o-ring, which is installed inside the can, is to stop the can from loosening during firing.

The oring is for keeping the threads of your muzzle clean and keeping the silencer tight.  Sorry about the website. We are updating it now and should have a full  new website in a month or two. In the mean time I would be happy to send you specs to your email. PM me or email and I will take care of it.

PM sent. Thanks for the response, I'm assuming that if you use regular threads you are indexing on the shoulder?

yes