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This is my first ar build. Some guys say do the head spacing others say don’t worry about it….
I have a hodge podge of parts. Aero upper, cmmg barrel, and a Grendel hunter bolt.
Coming from the bolt world headspace is 100% especially for accuracy.
I’m not building a 1000 yard ar but accurate round on target (coyotes,fox bobcat ) are a must
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A quality barrel will answer 99.99% of any headspace questions, that plus a bolt with the 0.136" face depth. There are some mostly earlier models of 6.5 Grendel that are set up for a 0.125" face depth but I have not heard of any 6Arc ones like that. I would measure the face depth of that grendel hunter bolt.
Cmmg, Faxon, the Monster ones on here... all of the 6Arc barrels I've seen (and I have 3 myself) have all been fine. If you want to satisfy your itch sure, go ahead and do the head spacing, provided you have some 6Arc go/no-go gauges.
My opinion, your time is better spent making sure the barrel/upper assembly fit is square and snug.
Take your time building, doing the build is half the fun.
After assembled you will want to use a headspace comparator and measure the COAL and seating depth for the bullets you have. Not all of them will spec out/default to a 2.260" OAL - that is an important thing to do.
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....Brownell's has the 6ARC GO/NO GO kits in stock, $66, well worth the minimal cost, especially if you plan to build more or swap barrels or bolts/BCG's in the future.
...when doing a "mix & match" of parts, I would suggest getting the gauges and check your headspacing.
...when buying a barrel, if that vendor also offers a bolt/BCG, I would suggest getting what they offer...one would assume they have checked that it's compatible with the barrels they are selling and it implies it is covered by whatever warranty the vendor offers...
...even if you are not building a precision rig, the headspacing has more to do with safety...
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Dave... What r.tenorio says! With the mix of parts you have, I'd do the head space check. Anyway, to me, it's all part of the build; Especially a Franken-gun like yours. I want to be sure the bolt, chamber & extension all match up well.
The trick is growing up without growing old. -- Casey Stengal
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If your going to be using factory ammo and not familiar with reloading it would be best to check with a headspace gauge.
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01-06-2022, 01:29 AM
(This post was last modified: 01-06-2022, 01:31 AM by r.tenorio671.)
....FWIW, the GO/NO GO kit from Brownell's are Clymer's, come in individual tubes that are "screw" type and the tube is rather rigid and firm, i.e., won't collapse over time. Me personally, I always get gauges for any caliber I build, both GO & NO GO. I don't use FIELD gauges as a FIELD gauge just indicates its borderline too loose already, but still serviceable...at least until it wears after using for X amount of firings. I had a situation when helping a friend install a barrel and we had to swap bolts around in order to find a bolt that would pass both gauges...it happens.
....I also gauge the barrel BEFORE installing it, makes it much easier. YMMV
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01-07-2022, 08:33 PM
(This post was last modified: 01-07-2022, 08:43 PM by r.tenorio671.)
.... a while back in a conversation with an acquaintance, he was of the opinion that with AR15's being "standardized" gauges were an unnecessary expense. My response was that for the avg cost of $30-$45 per gauge, it was cheaper than the cost of a new bolt, or worse yet a complete BCG or barrel extension, especially when you factor in the shipping, labor and time costs. Factor in ammo or component costs used during testing and that amount increases. For a person that is fortunate enough to be able to afford swapping barrels or complete BCG's it's another tool for problem mitigation.
...when asked, especially by someone less mechanically inclined or lacking the proper tools, I typically recommend that when a vendor offers a barrel with a headspaced bolt or complete BCG, that the combo be purchased as it implies that whatever warranty the barrel vendor offers would be honored if issues are found. If the barrel vendor has a specific MOA guarantee, proper headspacing does have an effect on attainable accuracy even if "match grade" shelf ammo is used for that accuracy testing.
...just my $0.02
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For anyone going with a Proof CF barrel, they're headspaced for JP enhanced bolts so they make a good match.
