Gunsmithing Headspace & Go/NoGo Gauges

[LawnMM]

Finishing a MA-Ten build in 6.5CM. Can't find anybody that has a Go Gauge in stock anywhere, bought a No Go Gauge already. Here's the question, bolt does not close on the No Go Gauge, its noticeably set back from fully seated. This would indicate we don't have excessive headspace, correct? Do I really need to stress about trying a Go Gauge? The Go Gauge is minimum chamber spec, right? So if some ammo from Copper Creek loads properly I'd think I'm good to go...

Or is the potential risk worth holding off and finding a Go Gauge? Love to hear from the Smith's on the board

 

[ORD]

Might be worth a call FIRST to confirm that these are actually in stock and ready to roll, but I've had great luck with Creedmoor Sports in the past:

https://www.creedmoorsports.com/shop/6.5_Creedmoor_Go_Gauge.html

Good luck!

 

[nicko]

I'm no gunsmith but if you unthread your barrel untill the no go gauge chambers then you check the gap between the barrel and action with feeler gauge and if there is .003-.004 gap you should be fine once you torque it on that will give you your .002 clearance.

 

[LawnMM]

Called them a few days ago ORD, they don't have em =/

Its an Mkm upper, no real way to get a feeler between the barrel and receiver on the front end and from within the bolt would be in the way.

I'm just wondering how critical the go gauge is when headspace is concerned. If the chamber is short I shouldn't get the bolt to close on loaded ammo, if its long it would close on the no go gauge and it didn't.

 

[ORD]

Called them a few days ago ORD, they don't have em =/

Its an Mkm upper, no real way to get a feeler between the barrel and receiver on the front end and from within the bolt would be in the way.

I'm just wondering how critical the go gauge is when headspace is concerned. If the chamber is short I shouldn't get the bolt to close on loaded ammo, if its long it would close on the no go gauge and it didn't.

Damn...sorry about that. I wish that CMS had real-time inventory...what a pain!

I'm not a trained gunsmith, but I have ALWAYS checked headspace with go/no-go gauges on every AR type rifle I have ever built myself. While from the sound of what you are describing, I think you'll likely be just fine...I personally like having the gauges to idiot-proof my own work and those of others whom I entrust to make barrels for me. YMMV.

If one of the resident expert smiths doesn't chime in with an alternative or a thumbs up with the info you have thus far, you could always just rent a go-gauge (usually a set with go and no-go) from reamer rentals. See here for 6.5CM reamers/gauges: 6.5mm Creedmoor

 

[LawnMM]

I may go that route if a smith chimes in with a compelling reason to go the extra mile for a gauge, which as I understand it, just tells me ammo will load. I can chamber a live round and learn the same info. I would feel better having my suspicions confirmed though.

 

[LawnMM]

No gunsmith with a take on this?

 

[EL34]

Apparently the 6.5 CM go gauges have been hard to get for the past couple of months. I've been trying to get my hands on one off and on since August. I've got e-mail notifications in at a couple of sites, and I'm going to try to get hold of PTG on Monday, (if they have any, or know when they'll have some I'll post here) other than that I'm at a loss. If anyone here has one they would be willing to loan I would be very appreciative!

 

[phxfa]

I gots some... pm me if you need to borrow them

 

[EL34]

PM inbound

 

[dinc]

Whatever brand of gauge you use, all gauges need to be the same brand. If you have a Forster gauge and a PTG you will run into problems. They both need to be Forster or PTG or whatever. Buy them in sets. You need a Go Gauge of whatever brand you already have.

 

[Wannashootit]

Why would you need to check headspace on a barrel with the extension already attached and precision built to specific headspace specs at the factory?

 

[jdulaney]

PM me if you still need to borrow the gauges.

 

[LawnMM]

Why would you need to check headspace on a barrel with the extension already attached and precision built to specific headspace specs at the factory?

To make sure they did it right and it doesn't blow up my expensive receiver and other parts I paid for with hard earned money? Maybe you take it on faith that it was done properly, I don't, especially when the receipt for the barrel says "Barrels must have headspace checked to avoid injury or death" in big red letters.

I had the good folks at Mile High check it, and I double checked with a reamer rental set after final torque and assembly... Good to go!

 

[ORD]

To make sure they did it right and it doesn't blow up my expensive receiver and other parts I paid for with hard earned money? Maybe you take it on faith that it was done properly, I don't, especially when the receipt for the barrel says "Barrels must have headspace checked to avoid injury or death" in big red letters.

I had the good folks at Mile High check it, and I double checked with a reamer rental set after final torque and assembly... Good to go!

Glad you got it squared away and that everything checked out. Look forward to seeing the "finished product" and your results with it!!

 

[LawnMM]

Waiting on washers to time the muzzle brake, the 308 crush washers are a bitch and I don't feel like twisting ny receiver to time it. Should have the washers Wednesday then I'm heading to the range Thursday to put some ammo through it, zero, chrono the ammo.

I will post pics and results along with the components used for the build!

 

[Wannashootit]

To make sure they did it right and it doesn't blow up my expensive receiver and other parts I paid for with hard earned money? Maybe you take it on faith that it was done properly, I don't, especially when the receipt for the barrel says "Barrels must have headspace checked to avoid injury or death" in big red letters.

I had the good folks at Mile High check it, and I double checked with a reamer rental set after final torque and assembly... Good to go!

I get it, but..
So, the manufacturer tells you to check the headspace, on their barrel extension- that sets the headspace- that THEY installed?

If for some reason it wasn't to spec, you can't fix it anyway- it would need to be returned.

IMO, it's no different than buying an off-the-shelf bolt gun. The headspace on it- just like the factory installed barrel extension- SHOULD be "right". I wouldn't expect Remington to require I check the headspace on their rifles before firing.

Not knocking you for checking, just saying that it shouldn't be necessary- nor should the manufacturer disclaim responsibility for same.

Bolts, and barrels/extensions for these platforms have precision tolerances that they are required to meet before leaving the factory.

Good luck with the build, looking forward to the range report.

 

[ORD]

I get it, but..
So, the manufacturer tells you to check the headspace, on their barrel extension- that sets the headspace- that THEY installed?

If for some reason it wasn't to spec, you can't fix it anyway- it would need to be returned.

IMO, it's no different than buying an off-the-shelf bolt gun. The headspace on it- just like the factory installed barrel extension- SHOULD be "right". I wouldn't expect Remington to require I check the headspace on their rifles before firing.

Not knocking you for checking, just saying that it shouldn't be necessary- nor should the manufacturer disclaim responsibility for same.

Bolts, and barrels/extensions for these platforms have precision tolerances that they are required to meet before leaving the factory.

Good luck with the build, looking forward to the range report.

If the barrel was setup on a customer-supplied bolt at the time it was mated to its extension, chambered, etc., then I agree that it SHOULD be good to go, however, many people buy AR barrels (whether AR-15 or large-frame AR in whatever caliber they might be buying) off the shelf/rack that were setup on X- or Y-bolt or specs from whatever factory/shop the barrel came from. In generally, the vast majority of all AR barrels SHOULD be ok in terms of proper headspacing, however, you get into issues of stacking tolerances which can, if on the extreme ends of the specs, get you into problems with the safe operation of any AR-type rifle. This can be particularly true nowadays with so many "one-off" offerings for bolts, barrels, coatings on them, etc. Who is to say what WILL and what WILL NOT properly headspace with x- or y-barrel and what tolerances will or will not get you into trouble with a build. Call it unnecessary or a waste of time or...whatever you want to call it...but I'll gladly take the time and effort to confirm that I'm in the appropriate operating range for headspace rather than take it on faith that "it'll be ok." Unless I have a smith setup an AR barrel for me to my own bolt that I supply for the build, then I ALWAYS check my barrels...otherwise, if I know the smith and trust his/her work, I do NOT double-check headspacing. Do as you will...

 

[LawnMM]

Correct. They didn't cut the barrel, install the extension, and headspace it with my particular bolt. This is a Kreiger barrel sold by a third party vendor. Additionally there are differences with respect to DPMS and Armalite patterns in the AR10 world. DPMS being the vastly more prevalent I was quite certain I'd be okay but I didn't want to just assume it was correct pattern and thus the correct headspace. The details on the website I bought the barrel from didn't include the pattern. So just as ORD is saying, I wanted to make sure Barrel Extension X mated up and headspaced properly with Bolt Y and didn't cause an issue.

I would say your analogy with buying an off the shelf Remington 700 is completely different. It would be the same if I built a ready to go AR10 rifle. I didn't do that though. I bought parts that I wanted from different manufacturers and pieced it altogether myself. To use your analogy it would be like buying a new PTG 1 Piece Bolt and trying to just drop it in and go with the Remington 700 in my living room. Obviously you can't do that. I can't expect all the parts to just mate up without any issue. SHOULD that work, yeah, it should! However with over $3000 dollars worth of parts toward the build, I don't want it blowing up on me so for me, its worth a little effort to double check.

Rich