Headspacing a new bolt in AR15???

[Wyzrd]

Alright guys, this may seem very elementary to many here, but I have just never done this in the past with any of my AR’s. So, I just recently got a nice AR in 223 wylde from a guy here on the Hide with a Rainier Arms Ultramatch barrel, and I’m also getting a JP FMOS BCG with JP enhanced bolt.

Now, with all my other AR’s, I’ve either bought whole rifles, or complete uppers with bolts already headspaced to the barrel, so I’m ignorant when it comes to this. My question is:

With a quality barrel and bolt, is it a must to make sure the JP bolt headspaces to the Rainier UM barrel? I don’t have the go/no go gauges to do it myself, but I’ve also read lots of conflicting stories on if it’s even necessary or not. So, I’d like to hear from the guys here that have come across this issue. What route would you go? Should I just wait to shoot it and bring it to a local gunsmith to have them check headspace first? Or, just load it up and go shoot...? Thanks!

 

[VegasHKShooter]

You are likely to get many different answers. I have always been told, and for my own part seen, when using quality parts, it’s not an issue. That said, I have interchanged bolts and different barrels many times. I have added NP3 bolts and bolt carriers to various rifles with zero negative results. I have done it to BCM/Noveske/Colt rifles, using NP3 bolts from Sionics. Never an issue.

 

[CANTHITSH!T]

Alright guys, this may seem very elementary to many here, but I have just never done this in the past with any of my AR’s. So, I just recently got a nice AR in 223 wylde from a guy here on the Hide with a Rainier Arms Ultramatch barrel, and I’m also getting a JP FMOS BCG with JP enhanced bolt.

Now, with all my other AR’s, I’ve either bought whole rifles, or complete uppers with bolts already headspaced to the barrel, so I’m ignorant when it comes to this. My question is:

With a quality barrel and bolt, is it a must to make sure the JP bolt headspaces to the Rainier UM barrel? I don’t have the go/no go gauges to do it myself, but I’ve also read lots of conflicting stories on if it’s even necessary or not. So, I’d like to hear from the guys here that have come across this issue. What route would you go? Should I just wait to shoot it and bring it to a local gunsmith to have them check headspace first? Or, just load it up and go shoot...? Thanks!

There isn't a thing in the world you can do about "headspace" in an AR and the rifle, bolt and barrel extension are specifically designed to "sidestep" the whole "headspacing" thing. Put it together and shoot it.

 

[Wyzrd]

I appreciate your guys replies/input so far. So far both answers are mirroring what I’ve heard from most folks. I know there’s always the possibility of things going sideways, and there being a catastrophic failure, but it seems like each instance I’ve heard of something like that happening, it was always with some “lesser quality components”... I know JP and Rainier make top notch gear, but there’s still that sliver of doubt in the back of mind telling me that I should just fork out the $ to have a smith check headspace. Anyways, thanks again guys!

 

[supercorndogs]

There isn't a thing in the world you can do about "headspace" in an AR and the rifle, bolt and barrel extension are specifically designed to "sidestep" the whole "headspacing" thing. Put it together and shoot it.

"""""""""""""""""""Bull shit, you find if the bolt is cut too deep or the chamber, and contact whom ever made which part."""""""""""""""""""""""""""""""

 

[EXTREMEPREJUDICE]

but there’s still that sliver of doubt in the back of mind telling me that I should just fork out the $ to have a smith check headspace.

Or you could just fork out $30 for a field/maximum headspace gauge and use it every time you change a barrel, bolt, etc.

 

[dinmax82]

Last ar10 I built wouldn’t close on gauges. Chambers round fine. Shoots fine, but ymmv

 

[Wyzrd]

Or you could just fork out $30 for a field/maximum headspace gauge and use it every time you change a barrel, bolt, etc.

Is a field gauge a better option than going with go/no go gauges? Or do they both accomplish the same thing pretty much? I’m genuinely curious as I’ve never had to deal with either.... does sound like a good thing to have though because I can see myself ordering more barrels for these rifles in the future. Again, thanks for the replies guys!

 

[EXTREMEPREJUDICE]

The go/no go are the best for setting headspace. The field is maximum for safety. it could close on a no go and still be safe to shoot. Since AR components (in theory) are built to spec, I just use a field gauge.

 

[Rerun7]

The go/no go are the best for setting headspace. The field is maximum for safety. it could close on a no go and still be safe to shoot. Since AR components (in theory) are built to spec, I just use a field gauge.

This. I use a field gauge just to ensure it’s safe and then go shoot. As mentioned, if it’s quality parts there shouldn’t be an issue but I like the piece of mind that a quick field gauge check provides.

 

[MtnCreek]

What I do. Not saying it's what you should do. I fire a rd and drop the case in a dillon gage to see how it looks. All so far have looked fine (not too high in the gage). Repeat and call it good.

 

[Wyzrd]

Ok, so I put in an email to Rainier in regards to this, and Scott replied that I should be good to go as they base their chamber specs on the JP bolts. Yes, they do recommend checking headspace when changing barrels and bolts from different manufacturers. But, as others have stated, he said that when using quality components, it’s not 100% necessary. I guess I lucked out going with this barrel/Bolt combo, as I had no idea that they based the spec on their UM barrels with JP bolts..... So, thanks again for all the replies guys!!!

 

[spife7980]

Its still really easy to buy a $30 go gauge and check and not worry about he said-she saids. A piece of scotch tape on the back makes it a nogo. Another piece makes it a field.

Then you can check all your buddies as well and look like not-an-idiot to them. And if youre spending as much as rainier commands to go with likely a .800 proprietary gas block too boot in addition to all the jp stuff a gauge really isnt going to break your bank anymore.

 

[Greg Langelius *]

Couldn't a' said it better.

Trust, but verify...

Greg

 

[sandwarrior]

Is a field gauge a better option than going with go/no go gauges? Or do they both accomplish the same thing pretty much? I’m genuinely curious as I’ve never had to deal with either.... does sound like a good thing to have though because I can see myself ordering more barrels for these rifles in the future. Again, thanks for the replies guys!

Just so you know. A go gauge is supposed to let the bolt close completely as it's the minimum chamber spec. A no-go is not supposed to let the bolt close as it's just oversize the chamber depth spec. A field gauge is supposed to be the maximum length of the chamber and it should close. It may not. But as long as it closes on the go, then you rifle is good to go.

Here's a good read:
https://www.brownells.com/aspx/learn/learndetail.aspx?lid=12555

Added: What I read in that Brownells is a bit different than how I understand it. Which in my last line of the first paragraph is stated backwards. A field gauge should not close. It's the last line of "still safe" past a no-go.

 

[FishinGuns]

Proof Research .223 and 6.5G barrels are headspaced off JP Enhanced bolts as well. I spoke with them on the phone about this.

I assume their other barrels are as well, but I did not ask specifically.

 

[spaniel]

You're probably going to assemble more than one 223 in your life and a GO gauge is $25-30. You can make it a NO-GO by applying 2 layers of scotch tape to the rear. An explosion is going off inches from your face. Is your face worth $30?

I know lots of people who don't check and have no issues. However one of them blew their rifle on my range after replacing the bolt because the headspace was too long...we believe it was a case of tolerance stacking. Not going to mention names but it was not a chincy part.

 

[WarbirdWeaponry]

For reliability, it is more important to check a go-gauge. As far as safety, an extra .005-.010" of headspace is not going to "blow up" a rifle. There is plenty of factory ammo that comes up that short of a go-gauge. Compare new brass to fired brass sometime, you may be surprised.

FWIW, I fireform 6mm BRX brass in an AR-15, it has .100" excess headspace.

 

[flyer]

.223 bolts are a pretty safe bet because there are bolt specs and barrel makers chamber to work with those specs.

I'm not a gambling man so I check any way.

Where it gets dicey is different chamberings. I seem to remember there being two "standards" for 7.62*39 AR bolts. Not good.

In large frame ARs I think the LR308 and AR10 bolts are different. I stick with LR308 stuff and check headspace every time.

Field gauges are used to identify guns that might blow up. If your gun closes on a field, don't shoot it.

I don't own any field gauges because I'm not desperate to keep my rifle in the fight (I've got spares). Close on a No-Go is my rejection point.

 

[Greg Langelius *]

This is why I prefer to buy complete Uppers. The one Upper I did build (assemble?) was done as an experiment in personal abilities and made up from Milspec parts, which are supposed to all work together acceptably; mainly because they are maintained by high school graduates (like me) without specific machinist/engineering training.

I would be surprised if they were not trained on chamber gauges, but the entire headspacing process seems to depend on a properly spec'd and assembled barrel/barrel extension assembly working with a properly spec's and assembled bolt, so parts from different suppliers could be incorporated.

Since my build, I have listened and read here diligently for evidence that there is cause for worry in all cases, and that has not been my reading experience. Since I'm not qualified to give reliable advice or to do anything about altering headspace on an AR, I now leave that stuff up to the manufacturers, and buy Uppers as complete units.

But I'm still going to buy a NO GO gauge and use it according to instructions as a precaution against a very unlikely issue; trust, but verify.

Greg

 

[Frankly]

It’s fine

 

[flyer]

This is why I prefer to buy complete Uppers.

I got over that pretty quick. The companies making uppers that I wanted were charging very high prices. Most companies were not making what I want. Lastly, the process is easy, it doesn't require a lot of tooling and doing it gives you a better understanding of the system.

Now I build exactly what I want (can afford), I ignore mil specs when better options are available and occasionally I make "incompatible" parts work together by modifying them.

I wouldn't have felt terribly comfortable building a 6.5 Creedmoor LR308 type rifle from parts if I hadn't done AR15 builds before then. I was mixing and matching and did have to modify several parts but now I've got a large frame AR that runs like a top, the action is very smooth and it is a legitimate 1,000 yard rifle that holds 1/2 MOA at 100 yards and would probably do that at 1,000 if I didn't have to deal with wind on the range.

I could probably do it cheaper and better today...

 

[sandwarrior]

A complete upper makes no difference if you swap a bolt into your BCG and it's out of spec. The problem isn't the upper it's the relationship of the bolt to the barrel/barrel extension. If the *new* bolt is out of spec, or a new barrel/barrel extension is out of spec is where you get the problem.

FWIW, you have, as noted above, about a .006" window to be in for the barrel/barrel extension fit. The lugs of the bolt have to be inside that window to fit and not have excessive headspace.

One thing I've noted over the years is I've often picked up .223/5.56 brass off the range. I noticed when sizing it, that I have to oversize all of it, I get it down to minimums. Because of various chamber depths. I also have to trim it all, as I note slightly different lengths. That means that not all chambers are in spec. yet they still fire and seem to function.

The real problem is if you minimum size and one rifle doesn't oversize them, but another one does, you really stand a good chance of incipient case head separation. Because the brass is sizing up and down too much, if going between the different rifles. Obviously, this only applies to reloading this. Those who do not reload, don't take on nearly as many issues as those of us who do reload for an AR in volume. I find it best to use sets of brass for one rifle. Whether it be an AR or bolt gun.

So, you can fire .223/5.56 at the maximum (or even slightly longer) chamber length and maximum dimensions of the headspace relationship. But, knowing what happens to the brass later says that you should not fire brass multiple times from different rifles and you should know where your headspace is when you change a bolt or barrel.

 

[flyer]

Headspace and reloading are two different issues.

Of course, I would not trust any brass that had been fired in a rifle with excessive headspace, the resizing would stress it a lot and that's just once fired, reload like that 2-3 times and your brass would be very suspect.

The solution is to reload for rifles individually and keep the headspace tight so your brass isn't getting worked as much. Then reload for semi-auto, it's not the same as reloading for a bolt action.

It's not hard to make sure your headspace is going to be good. A good barrel manufacturer is going to keep their chambers pretty consistent and if you ask them, they will tell you what bolt it should work with. Then double check with headspace gauges.

 

[Bradu]

"""""""""""""""""""Bull shit, you find if the bolt is cut too deep or the chamber, and contact whom ever made which part."""""""""""""""""""""""""""""""

I think his comment should go into the "what's the most stupid thing you've been told" thread lol.

 

[sandwarrior]

Headspace and reloading are two different issues.

Of course, I would not trust any brass that had been fired in a rifle with excessive headspace, the resizing would stress it a lot and that's just once fired, reload like that 2-3 times and your brass would be very suspect.

The solution is to reload for rifles individually and keep the headspace tight so your brass isn't getting worked as much. Then reload for semi-auto, it's not the same as reloading for a bolt action.

It's not hard to make sure your headspace is going to be good. A good barrel manufacturer is going to keep their chambers pretty consistent and if you ask them, they will tell you what bolt it should work with. Then double check with headspace gauges.

Good headspacing is critical to good reloading. Maximum allowable differences in headspacing between two different rifles does not make for good, or even safe, reloading. You can resize to a different rifle one time only after the first firing, IMO, and not have issues.

I concur that reloading for rifles individually is the best and safest way to go. I have had a few different rifles cause incipient headspace separation, i.e. .223, .243 Win., .257 Rbts, 7x57, and .300WM. I was told one time I was full of shit for saying, "Don't mix brass between rifles." Turns out he could do it because he had two rifle barrels cut for the same chamber, with the same reamer by the same guy, at the same time. So, his stance was, I ought to never tell someone one not to mix brass between rifles. I maintain, "Do not mix brass between rifles, unless you have a situation like his."

 

[supercorndogs]

Good headspacing is critical to good reloading. Maximum allowable differences in headspacing between two different rifles does not make for good reloading.

I concur that reloading for rifles individually is the best and safest way to go. I have had a few different rifles cause incipient headspace separation, i.e. .223, .243 Win., .257 Rbts, 7x57, and .300WM. I was told one time I was full of shit for saying, "Don't mix brass between rifles." Turns out he could do it because he had two rifle barrels cut for the same chamber, with the same reamer by the same guy, at the same time. So, his stance was, I ought to never tell someone one not to mix brass between rifles. I maintain, "Do not mix brass between rifles, unless you have a situation like his."

With .006 allowance and bumping the should .002. You could end up up bumping shoulders .008 for one chamber and .002 for the other. Brass does not last long at .008 bump.

 

[sandwarrior]

With .006 allowance and bumping the should .002. You could defiantly end up up bumping shoulders .008 for one chamber and .002 for the other. Brass does not last long at .008 bump.

I should also mention, I got away lucky as I didn't know that was a big issue. All of the cases were found during inspection or sizing. I had to throw away whole batches of brass.

 

[NukeMMC]

Take a set of calipers and measure the distance from the front face of your bolts to the rear of the lugs. Normally about 0.278" but dwg 8448510 says .278 +/- .002". I have found this dimension to be held pretty well. Now measure the distance from the front face to the face where the firing pin hole is ( I have found this dimension to vary up to 0.005" but is around 0.123") and subtract it from the first dimension. The face where the firing pin hole is dimension is based on the center of the bolt cam pin hole and has a +/-0.004" tolerance. The drawing has the dimension from the back of the lug to the face where the firing pin hole is 0.156-.003". This is where headspace can be affected by the bolt.

I would trust some of the higher end bolt manufacturers to hold the tolerance that actually sets headspace in an assembled rifle a bit tighter than .003" but when I have swapped bolts in a rifle before, I have measured to ensure I stayed within a couple thousandth's. But I will also verify with a GO gauge and some .001" shim stock.