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AR15.COM
8/8/2001 11:39:33 AM EDT
I have a Colt and want to replace the bolt assembly.  Do I have to buy Colt parts or will any assembly work.  Who makes the best one?  What do they cost?
8/8/2001 11:59:45 AM EDT
[#1]
If they are thoroughly "worn in" I wouldn't replace them.  I am not overly knowledgeable about this, but am answering b/c others haven't.  They are (I understand) meant to interchange, if made to mil-spec, and properly machined.  I would check the headspace whenever messing with the bolt of any firearm.  If you are referring to a complete bolt carrier assembly they cost about $115.00.  So, the answer to your questions are:  no, any [b]should[/b] work, don't know, $115.00.  
8/8/2001 12:04:24 PM EDT
[#2]
Thanks beekeeper The reason I asked is that Rock River Arms has them for around $100.  I thought it would be a good idea to have a few extra assemblies for backup.  What can wear out in the assembly?  How do you know when its time to replace?
8/8/2001 12:05:30 PM EDT
[#3]
Beekeeper pretty much nailed it.

I'll just add one thought - the WHY of NOT interchanging bolts and carriers.

Without proper headspacing, you set yourself up for the old exploding rifle, commonly known as the KABOOM.

KABOOM's are known to remove fingers, as well as key facial features.

Improper headspace causes out of battery detonation of the round. Out of battery detonation means the round is NOT properly supported by the bolt and chamber. When this happens BADLY enuf, the rifle explodes, and you visit the plastic surgeon. Or in a real bad KABOOM, the plastic bag.

A word to the wise.....
8/8/2001 12:10:16 PM EDT
[#4]
Bolt carriers are not a problem.  Replace/exchange them at will.  Good ones will have a chrome lined interior where the bolt rides (i.e. Colt, Bushmaster, Armalite and probably a few others).

Bolts CAN BE a problem.  Good news it they should only be a $40 part.  I keep a spare and check it periodically in my rifle using a USGI Field Gage (get the USGI one not the SAMMI commercial gauge).

BTW this question had come up many times in the Maintenance and Building Forums.  I'd suggest do a search there for more detailed information.
8/8/2001 12:10:35 PM EDT
[#5]
So if you are going to replace the bolt you would be best served to replace the barrel as well that way all new parts without headspace problems?
8/8/2001 12:11:53 PM EDT
[#6]
Girls, you are worrying too much.

Bushmaster even sells spare bolts.  A spare bolt is  great idea.

The barrel is headspaced, not the bolt.  So if all the parts are made correctly and not too worn, you can swap bolts w/out worrying about headspace.

8/8/2001 12:53:17 PM EDT
[#7]
Quoted:
So if you are going to replace the bolt you would be best served to replace the barrel as well that way all new parts without headspace problems?
View Quote


You only NEED to replace the bolt when it breaks or when you can chamber the Field Gauge.  If the bolt breaks (gets cracks in the locking lugs) then just get a new bolt and check the headspace with a USGI field gauge.

If you can chamber the field gauge put in your spare bolt (or buy one then put it in) and check it.  If the gauge can still chamber (doubtfull) then buy a new barrel.

Now with the New barrel installed check the head space using the OLD bolt (assuming it is not cracked or broken).  If it gauges fine then you are good to go.  If the gauge is swalled then..

Use the new bolt.  A new Bolt & barrel should headspace fine, just verify with the field gauge and you should be good to go.