Optimally it's best, but it's really not needed; unless both rifles are really worn/well used (think 8-10K rounds and up).

But if you do swap the bolts it will slightly increase the wear on the bolts as it 'mates' with the new barrel.

Then you shouldn't have any problems.  Just don't make it a habit.  

Cancel the order.

All you need is the USGI Field Gauge, the go/no go are more for guys building the barrels.

You want a USGI field gauge.  It comes in a foil wrapper with a calibration card.  The USGI can be used w/o disassembling the bolt (which is not the case with most civilian gauges).  The Field gauge will let you know when the headspace has become too long for safe operation.

Another reason to use the USGI vs the civilian Field gagues is one is done to proper 5.56 specs, the other to .223 specs.  You can fail a 5.56 barrel with a civie .223 field gauge; that same barrel will pass with the USGI gauge.

I got mine from Fulton Armory many years ago.  If they don't have them anymore then I'd with the guys selling AR parts at the gun shows (especially the guys with the older parts/cleaning kits and such).

$175?!

I think I paid $25, new in unopened wrap.  Wild that they are so pricy now.

Actually YOU are the one that incorrect.  This discussion is about AR-15 type rifles and safe headspace procedures for them, your remarks are for rifles other than AR-15s.  For this discussion we'll all have to be on the same page:

First everyone get out your copy of TM 9-1005-319-23&P  Unit and Direct Support Maintenance for the M16A1, M16A2 & M4

If you don't have a printed copy, click the link above and you can download a copy from this site.  I HIGHLY suggest anyone who is into ARs and might work on or build their rifles have a copy of this book as it covers pretty much everything including troubleshooting, tools needed (and plans to make tools that are helpful but not required), and full tear down & rebuild.

Now we all have our manuals open, please turn to page 3-47, you'll see how to check headspace on line #8, then the procedure to fix the excessive headspace problem in line #9. (note this is repated in page 3-47 1/(3-4) in change for as line #12(c)

You'll note NEVER is a 'go' gauge called for.  On page C-17-1 you'll find the complete tool list needed for maintenance of the rifle - note that only a field gauge (Gauge, Headspace NSN# 5220000707814) is called out.  The only place I've heard of a go/no gauge being used is at Depot Level and those guys can pull off barrel extensions (something no user will ever do).


People that aren't into ARs might; AR armorers and enthusiasts not so much.


Bolts may, and have, get swapped accidentally; but even if they do the only potential problem is excessive headspace, which a field gauge catches.  You'll never have a problem of too little headspace, AR bolts aren't made that way.

Do you know what the first thing you do if a rifle fails the Field Gauge?  (you do if your read 3-47) You drop in a NEW bolt and test again with a field gauge - if it passes you're good to go.  A used bolt will never be bigger than a new AR bolt so the only issue with swapping is excessive headspace (which isn't as big an issue as most think - see Hatcher's Notebook by MG Julian Hatcher for details)


In fact if you read the Military's manual you'll find they NEVER use a go gauge when swapping in a new barrel for an AR series rifle.  It's simply not needed.


And that's why guys with much M1A/m14 experience should not comment on AR procedures.  That bolt system and system of manufacture for that rifle is completely different from the AR series, with an M1A it's possible to assemble it with insufficient headspace - not so with the AR.  The FALs also need both gauges as headspace can be adjusted.

With the AR platform there is no headspace 'adjustment'.  Unless you bought a custom match barrel that some smith reamed himself the gauges aren't needed and the ARs headspace can only be adjusted by reaming a bit more.  That's not an issue with chrome lined (or other metal treatments) barrels.  Headspace is set at the factory, all new bolts will drop in and work, used bolts MAY pass, or they may have excessive headspace.  Check with a field gauge.

This is one of the great strengths of the AR system for the builder and hobbyist, and it makes it much easier on the military armorers.

If for some strange reason (that one in a billion problem) and somebody bought a bought from a bottom feeder AR parts company that was made wrong, when you go to chamber a round - it won't chamber and bolt won't lock into place.  Weapon won't fire, but you won't be blowing up either.