Calgary AR15 headspace check

[arcticcathonda]

Shot in the dark but I figure I would ask.

I can buy the gauges from Brownells, but perhaps there is someone in Calgary that could quickly drop their gauges into my barrel with bolt and double check for me. Of course there is beer/ coffee payment!

 

[Suputin]

What makes you think your chamber is out of spec?

 

[arcticcathonda]

What makes you think your chamber is out of spec?

I understand that a properly manufactured part should be in spec. But rather than assemble and experience a failure of any sorts, it just seems like a little extra peace of mind. Call me paranoid maybe?

 

[hbean]

Any gunsmith in town should be able to check it for you in 2 minutes.

 

[toomanyhobbies]

I would suggest that it's always a good question to ask if you're assembling a Franken-AR. Mixing parts from different vendors can lead to an out-of-spec condition. I'm in a similar boat, I put an S&J barrel on a Spike's upper with a Daniel Defence bolt & carrier that won't chamber .223 snap caps. A set of gauges would be most helpful.

 

[arcticcathonda]

I would suggest that it's always a good question to ask if you're assembling a Franken-AR. Mixing parts from different vendors can lead to an out-of-spec condition. I'm in a similar boat, I put an S&J barrel on a Spike's upper with a Daniel Defence bolt & carrier that won't chamber .223 snap caps. A set of gauges would be most helpful.

I have an aero upper and an S&J barrel in the mail currently. Just wanted to double check like you.

 

[Suputin]

I understand that a properly manufactured part should be in spec. But rather than assemble and experience a failure of any sorts, it just seems like a little extra peace of mind. Call me paranoid maybe?

You are paranoid. Assemble your rifle and shoot it ... all will be fine. I can't begin to tell you how many various bolt - barrel combinations I have put together and never had a headspace issue.

What kind of failure do you think would come from a headspace problem? Do you reload or shoot factory ammo?

I put an S&J barrel on a Spike's upper with a Daniel Defence bolt & carrier that won't chamber .223 snap caps. A set of gauges would be most helpful.

Just to be clear, the upper makes no difference. The only two parts that have any effect on the headspace are the bolt and barrel. Does your rifle chamber factory ammo? Maybe the snap caps are out of spec. Are they true snap caps, or like the last guy who complained about headspace issues, home made dummy rounds?

 

[arcticcathonda]

You are paranoid. Assemble your rifle and shoot it ... all will be fine. I can't begin to tell you how many various bolt - barrel combinations I have put together and never had a headspace issue.

What kind of failure do you think would come from a headspace problem? Do you reload or shoot factory ammo?




Just to be clear, the upper makes no difference. The only two parts that have any effect on the headspace are the bolt and barrel. Does your rifle chamber factory ammo? Maybe the snap caps are out of spec. Are they true snap caps, or like the last guy who complained about headspace issues, home made dummy rounds?

Fair enough, this is my first assembly so just want to get all of the facts. I thought if you had a upper receiver barrel extension out of spec you could also have HS issues? Though rare, bad QC happens. Glad to hear you have never had any issues! I shoot both factory and reloads with a heavy emphasis on surplus.

 

[Suputin]

Fair enough, this is my first assembly so just want to get all of the facts. I thought if you had a upper receiver barrel extension out of spec you could also have HS issues? Though rare, bad QC happens. Glad to hear you have never had any issues! I shoot both factory and reloads with a heavy emphasis on surplus.

The barrel extension is part of the barrel. The bolt locks into the extension. Nothing else matters.

The potential problems that can occur from incorrect headspace are:

Headspace too short - ammo won't chamber. Not so much an issue as a gun that isn't properly locked won't shoot. The solution is to ream the chamber deeper. Annoying but certainly possible to do as long as the bbl isn't chrome lined.

Headspace too long - It really depends on just how long the headspace is but at the extreme end this can result in cracked, split or separated case heads. THIS does present some danger as high pressure gas will leak out the rear end of the chamber and into the shooter's face. A separated case body will also need to be removed. If the headspace is only a bit too long this is not really a big deal as the military has a thing called a Field gauge which is longer than a No Go gauge and until a rifle fails the field gauge it is considered safe to shoot. The chances of you having a new barrel that fails the Field gauge is VERY low.

An AR bbl that fails the field gauge is garbage. There is no way to fix this condition ... at least none that any self respecting gunsmith would consider.

Note: If you reload the entire concept of headspace is rendered moot because you can adjust your sizing die to fit the chamber and thus end up with the correct headspace relationship between chamber and ammo. Headspace is really only relevant when shooting factory ammo.

 

[arcticcathonda]

Thanks very much for taking the time to explain this further. Appreciate it.

The barrel extension is part of the barrel. The bolt locks into the extension. Nothing else matters.

The potential problems that can occur from incorrect headspace are:

Headspace too short - ammo won't chamber. Not so much an issue as a gun that isn't properly locked won't shoot. The solution is to ream the chamber deeper. Annoying but certainly possible to do as long as the bbl isn't chrome lined.

Headspace too long - It really depends on just how long the headspace is but at the extreme end this can result in cracked, split or separated case heads. THIS does present some danger as high pressure gas will leak out the rear end of the chamber and into the shooter's face. A separated case body will also need to be removed. If the headspace is only a bit too long this is not really a big deal as the military has a thing called a Field gauge which is longer than a No Go gauge and until a rifle fails the field gauge it is considered safe to shoot. The chances of you having a new barrel that fails the Field gauge is VERY low.

An AR bbl that fails the field gauge is garbage. There is no way to fix this condition ... at least none that any self respecting gunsmith would consider.

Note: If you reload the entire concept of headspace is rendered moot because you can adjust your sizing die to fit the chamber and thus end up with the correct headspace relationship between chamber and ammo. Headspace is really only relevant when shooting factory ammo.

 

[sunray]

Headspace isn't a spec, it's a rifle manufacturing tolerance only. It has nothing to do with factory or reloaded ammo. That makes no difference. However, a snap cap, aside from being unnecessary with a cf rifle, will tell you exactly nothing. Neither will a DP cartridge, but those are more useful than a snap cap.
In any case, if you installed a barrel without headspace guages(Go and No-Go) it very possibly has bad headspace. If you're assembling rifles, you need a set. Brownell's is a retailer. You can buy guages direct from Clymer or Forster with no border issues.
Advising that you don't need headspace guages is irresponsible. Stateside, you'd be liable if something bad happened too.

 

[Suputin]

Headspace isn't a spec, it's a rifle manufacturing tolerance only. It has nothing to do with factory or reloaded ammo.

BULL! If you go to the SAAMI website they use the word "specification" front and centre on the page. If you look a the URL below it even includes the word "specifications." Are you telling us that SAAMI doesn't know what it is talking about? Because after all they are the ones that make the rules we are currently discussing.

http://saami.org/specifications_and_information/index.cfm

The SAAMI spec includes a tolerance for the headspace dimension. The entire point of the SAAMI specification for headspace is so a rifle made in Buttplug North Assholia will safely fit and fire ammo made in East Northernistan. So yes, headspace has everything to do with factory ammo.

However, a snap cap, aside from being unnecessary with a cf rifle, will tell you exactly nothing. Neither will a DP cartridge, but those are more useful than a snap cap.
In any case, if you installed a barrel without headspace guages(Go and No-Go) it very possibly has bad headspace. If you're assembling rifles, you need a set. Brownell's is a retailer. You can buy guages direct from Clymer or Forster with no border issues.
Advising that you don't need headspace guages is irresponsible. Stateside, you'd be liable if something bad happened too.

When was the last time you ran across a factory AR barrel that had incorrect headspace? I'm not saying it can't happen but it is a very rare occurrence, not a condition I would categorize as "very possible" to occur when assembling a rifle. I assemble uppers from a miriad of sources and use all kinds of different bolts in my test rifles and have not yet run into a combination that created a serious headspace problem.

I'm not saying someone shouldn't have the gauges or that it is a bad idea to use them because that would be silly. What I'm saying is that the chances of running in to a headspace problem when assembling an AR from factory produced parts is highly unlikely.