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1/12/2012 4:45:33 AM EDT
I hear some fellows say that carrying a spare bolt is a good idea for quick replacement of failed extractors, ejectors, and so on, while others say headspace could be an issue in doing so. Still others have said that headspace only becomes an issue with a bolt swap in a gun with a high round count, where the bolt and barrel extension have really mated up well with each other. Given all this talk, at what point in round count does it become unwise to swap out a bolt in an AR 15 without checking headspace beforehand?

MM
1/12/2012 5:53:30 AM EDT
[#1]
A used bolt in a used barrel is  a potentially bad thing.

But a new bolt in a used barrel will be ok in almost all cases except the extremes.

I have seen barrels that have had their throats shot out but still headspaced fine.

Chances are good that your used barrel will gage just fine with a new bolt.
1/12/2012 6:09:58 AM EDT
[#2]
Check the headspace and be done with it, 20 minutes if you take your time...  
I check my headspace on my high round rifles every 3 tins of rounds, so thats a little over 1200 rounds, then I go through the rifle clean out the lower, completely breakdown the bolt, check headspace, replace a hand full of parts and be done with it, I do keep a spare bolt, its a chrome rock river that I keep in my bench bag, probably has 200 rounds through it, when my spare bolts get around 1000 rounds, Ill use them in a build and get another new spare....
1/12/2012 6:38:12 AM EDT
[#3]
Check the headspace.
It can be right any number of times. It only has to be wrong once.
1/12/2012 7:27:27 AM EDT
[#4]
Quoted:
Check the headspace and be done with it, 20 minutes if you take your time...  
I check my headspace on my high round rifles every 3 tins of rounds, so thats a little over 1200 rounds, then I go through the rifle clean out the lower, completely breakdown the bolt, check headspace, replace a hand full of parts and be done with it, I do keep a spare bolt, its a chrome rock river that I keep in my bench bag, probably has 200 rounds through it, when my spare bolts get around 1000 rounds, Ill use them in a build and get another new spare....


Curious as to what parts you replace after 1200 rounds?
1/12/2012 7:37:13 AM EDT
[#5]
your supply of ammo
1/12/2012 7:58:54 AM EDT
[#6]
Quoted:
Quoted:
Check the headspace and be done with it, 20 minutes if you take your time...  
I check my headspace on my high round rifles every 3 tins of rounds, so thats a little over 1200 rounds, then I go through the rifle clean out the lower, completely breakdown the bolt, check headspace, replace a hand full of parts and be done with it, I do keep a spare bolt, its a chrome rock river that I keep in my bench bag, probably has 200 rounds through it, when my spare bolts get around 1000 rounds, Ill use them in a build and get another new spare....


Curious as to what parts you replace after 1200 rounds?


Only thing I change often is my firing pin retainer..... First signs of excess wear or looks like it is getting weak I swap it because they are so cheap.  Just my .02 but it is just to cheap to neglect.
1/12/2012 10:46:15 AM EDT
[#7]
Thank you all very much. Appreciate it.

MM
1/12/2012 12:45:49 PM EDT
[#8]
I don't think headspace will be a problem in a fairly new quality made firearm. They are made to have some give. I don't think I would buy one of those used older Colt bolts you see on the EE and throw it in a barrel that has about 5000 rds through it. I would however not think twice about putting a new bolt in a rifle with a 1000rds or less shot through it. I worry much more about this mil surplus ammo that we get so cheap being too hot and blowing everything up. Most failures involve ammo. Actually almost all failures involve ammo. However, if you get careless you can have serious problems. If I were building a gun to target shoot I would probably go ahead and get the go nogo guages just to be on the safe side. However, in a SHTF situation I wouldn't hesitate to put those parts together to defend myself.
1/12/2012 12:52:57 PM EDT
[#9]
Since we are talking about headspace.. what would happen if you used parts the headspace was very far off? Like worst case scenario?
1/12/2012 12:59:18 PM EDT
[#10]
blowout of the gases. The chamber is kept closed when you have the correct headspace. If it's off too much gases can escape. In some cases it may not even chamber a round. If gases escape the chamber, other than the muzzle or gas port, you get kaboom.
1/12/2012 12:59:34 PM EDT
[#11]
Um, Kaboom...
1/12/2012 1:01:38 PM EDT
[#12]
Quoted:
A used bolt in a used barrel is  a potentially bad thing.

But a new bolt in a used barrel will be ok in almost all cases except the extremes.

I have seen barrels that have had their throats shot out but still headspaced fine.

Chances are good that your used barrel will gage just fine with a new bolt.


QFT
There is only so much tolerance between a bolt and chamber in lock up.
When you mix worn bolts with different worn barrels, you can get out of spec with too much headspace.
It's not a bad idea to check them every so often.
Usually the throat is shot out way before the head space gets past acceptable specs.
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