Replacing BCG soon.....Headspace or No?

[jhs1969]

I've always heard to head space any firearm after replacing bolt, barrel etc. (makes sense to Me)
But I've also herd people say it isn't necessary with the AR. In fact I've herd guys admit to doing this, but I've always been a little careful about such things. It seems a trip to the gunsmith would be cheap insurance. Any 'smiths out there have advice?

[Shihan]

Its always good to headspace a new bolt. You can look in the tech forum, ar15barrels posted some good info on gauges.

[toddackerman]

I've always heard to head space any firearm after replacing bolt, barrel etc. (makes sense to Me)
But I've also herd people say it isn't necessary with the AR. In fact I've herd guys admit to doing this, but I've always been a little careful about such things. It seems a trip to the gunsmith would be cheap insurance. Any 'smiths out there have advice?

Lots of info in the Technical AR Section regarding "Preventative Maintenance", and I have just gone through the learning curve. Here is what I have learned mostly from Randall Rousch at AR15 Barrels.com (He has been most patient with teaching us about this, and I would say that he is very credible.) Hopefully he won't mind me sharing his wisdom with you.

For a "new" Bolt/ Barrel combo, you would want to check minimal head space with a "Go Gauge". This insures that the chamber is cut long enough to cycle a round into it. You could also just use a know good factory round and chamber it.

A "No-Go Gauge" is used on "new" bolt/ barrel combos to see if the head space is excessive to SAMMI standards, which I learned are tighter than Military standards. On a new Bolt/ Barrel combo, the bolt should not close on a "No-Go Gauge".

Finally, there is the "Military Field Gauge" which represents the MAXIMUM head space that is safe. Note that the Military Field Gauge is slightly longer than the commercial because the Military doesn't;t have to adhere to SAMMI specs., and they cut the chamber a little larger to accept various lots of ammo.

It is possible to swap bolts between weapons, but I wouldn't do it unless I minimally checked the combination with the "Field Gauge" to make sure excessive head space is not an issue.

Please go to the AR Technical section and look up the "Preventative Maintenance thread before asking anymore question on this thread. It's really pretty concise because we/ I have asked a lot of questions on this topic. Here is the URL... http://www.m4carbine.net/showthread.php?t=8332

Most of the discussion on head space occurs on the 2nd and 3rd page. Pay particular attention to what Randall Rousch posts, especially his links to Gauges and dimensions.

Tack