Most bolts are close and will not pose a problem but CMT/Stag are known to be on the large side, LMTs are known to be on the small side. If you use a Stag bolt in a LMT barrel most will be tight headspace, use a LMT bolt in a Stag/CMT barrel and there will more than likely be too much headspace. I have no idea who BCM buys their bolts and carriers from.
Also swapping back and forth is not a good idea because the lugs of the bolt get mated to the lugs of the extension, they should be flat but nothing is perfect. I would buy a bolt for each barrel and keep them together.