AR-15 Bolt carrier group and charging handle question?

[DalesCarpentry]

At some point I am going to take the leap and buy an AR-15 some day. There are many variations of these rifles now and you can just switch uppers to a different configuration. My question is since you can buy uppers with out the bolt and charging handle can you just keep swapping them from one upper to another or do they need to break in and get used to just one upper? The reason I say this is because it is much cheaper to just swap them instead of buying them for each upper. Now I do understand if you change calibers you need a different bolt and carrier group. Thanks Dale

[Savage]

No problem on a properly installed barreled upper of the same caliber. I have a tendency to buy complete rifles rather than swap uppers. If I were to go that route, I'd buy a bolt and carrier for each one. I like a complete unit not one that requires me to swap parts back and forth.
Savage

[shvlhead.45]

Dale,

Physically you can change bolt carrier groups (BCG) between different uppers of the same caliber but it's not advisable due to headspace issues.  The bolt and barrel begin to develop a wear pattern and swapping a  BCG between barrels will cause accelerated wear.  Also, each bolt should be headspaced to the barrel it is mated with to ensure safe proper function. 

To change calibers requires a complete upper with matched barrel and BCG of the desired caliber; for example changing from 5.56 to 6.8 or 6.5.

v/r
Shvlhead.45

[DalesCarpentry]

Dale,

Physically you can change bolt carrier groups (BCG) between different uppers of the same caliber but it's not advisable due to headspace issues.  The bolt and barrel begin to develop a wear pattern and swapping a  BCG between barrels will cause accelerated wear.  Also, each bolt should be headspaced to the barrel it is mated with to ensure safe proper function. 

To change calibers requires a complete upper with matched barrel and BCG of the desired caliber; for example changing from 5.56 to 6.8 or 6.5.

v/r
Shvlhead.45

Thank you. I kind of figured that they would berak in together and then be mated. Thats the answer I was looking for. Dale

[cjclemens]

I know this is an old thread, but I just did some reading on this, and I thought it might be useful info.

On AR barrels, headspace is set when the barrel and barrel extension are made.  This is usually done by the gunsmith/manufacturer/barrel maker.  In some cases, high end shops will match bolt heads to barrel extensions for an exact fit.

However,  AR bolt and carrier groups can be swapped out without worrying about headspace.  They were designed to be interchangeable and easy to replace in the field in case of failure.  If you have a low-mileage AR, and you want to put a new bolt/carrier group in it, you can do so without worrying about headspace.  If you are concerned, a quick check with a go/no-go gauge can tell you if there is a problem.

On the flip side, if you have a high mileage piece, and things are getting sloppy due to bolt lug wear, its highly advisable to do a check with the go/no-go gauges prior to returning to the range.

Unless its a permanent swap, switching bolt/carrier groups from one upper to another is not recommended.  Most wear on bolt/carrier groups occurs on the rear of the locking lugs, where they meet the front of the barrel extension locking lugs.  if constantly swapped, they will never wear evenly.