this is my first post, sorry if this has been asked before.
I have a bushmaster with around 500 rounds down range and I am going to replace the BCG. Sounds like LMT is the way to go so my question is do I need to check the head space with the new bolt or should I be fine just putting it in. I have done a lot of reading in here and you all seem to be very knowledgeable but just couldn’t find the answer .
Thanks
Was the BCG new when you first got it? If so, then there should be no reason to replace the BCG after only 500 rounds. Hell, you’ve probably just now broken it in.
yes it is new but I am going to be using it is some 3 gun and need to get a back up bolt so I figure on putting the better bolt in the gun and using the bushy bolt for back up
IMO you should always check the headspace when swapping parts even if the parts are new. Of course, not everyone has the correct gauges and the ability. As a rule of thumb I check every single weapon when I rebarrel or swap out bolts.
What are the correct gauges and are they available through brownells? 
Thanks!
+1 Links please
post #6 on this thread should help…
Without getting into all the 5,56 vs. .223 debate when I work on military weapons I use their gauges. When I work on the company weapons I use the gauge listed above. A Colt rep sent me that gauge along with some other stuff and told me that according to the engineers it will serve its’ purpose.
On my personal AR I keep a round count of how many rounds I fire. I won’t even think about headspace until at least 5K rounds. If you swap bolts, check it with the appropriate gauge and keep a round count you should have no issues. I do an annual inspection of my gun just like any other, I check the headspace, and firing pin protrusion. I would check the bore erosion but have been unable to locate a correct bore erosion gauge.
In a CATM shop, we fire a lot of rounds through our training guns and in a lot of cases, we are still using old chrome bolts from the old M-16 series rifles. We are using new barrels, new bolts; new barrels, old bolts; and in some cases when a bolt breaks we may even use a new bolt in an older A2 barrel. In every case we make sure we check the headspace to ensure that it’s within spec just to be safe. Woe to he who gives out a rifle that explodes in a students hands because he changed out a bolt and didn’t check that headspace!
That being said though, I have yet to see an M-16 that didn’t headspace within spec with any combination of bolt and barrel. Still though, even with my own rifles, I’m going to recheck the headspace any time I change a barrel or bolt. The price of the headspace guage is VERY cheap insurance and piece of mind. I mean think about it, what’s more expensive, your AR or a headspace guage?
thanks for all the good info…is it possible to put in 2 different bolts and one check good and one check out of specs? Then what would you do? I wouldn’t think that around 500 round would make your head space out of specs. But I am new to this platform, as far as doing my own maintenance. All I am really looking to do is get a bolt that is tested . Thanks