Advice on an M1 Garand Headspacing

[ol' scratch]

Hello,
I have all the parts to build an M1. What I was thinking about doing was going to the CMP and picking out a Service Grade reciever and barrel. Can I just install my bolt and the rest of the parts and be ready to go? The other option I had considered was going to the CMP (I live near a store) with bolt in hand and trying to find a Garand that has the correct headspacing with my bolt. Any advice would be appreciated.

 

[61chalk]

I think its going to be hard finding anything Service Grade at the CMP stores right now. They have been out except for mail orders for months.

 

[FlyinBryan]

most of the time, the bolts can be swapped.

headspace gauges are used to findout if they can or cant.

you should never just swap bolts like you can with an ar15, without checking the headspace. (really should do it anytime a bolt or barrel are changed, regardless of the type rifle)

headspace gauges arent that expensive, and are as easy to use as dropping a round in the chamber, and then see if the bolt will close or not.

 

[FlyinBryan]

the thing to do is buy a set of headspace gauges.

i would start with a "go gauge" and a "no go gauge"

remove ythe extractor and put the "go gauge" in the chamber. this one measures min. headspace. if the bolt closes easily and normally, all the way, your good.

then put the "no go" in the chamber, and same as above, except the bolt should not be able to be closed.

if the go gauge wont pass, make sure the bolt face and chamber are clean.

if it fails either, see a smith.

EDIT: DO NOT TRY TO FORCE THE BOLT IF IT WONT CLOSE ON EITHER GAUGE. IT SHOULD CLOSE VERY EASILY WITH THE GO, AND NOT AT ALL ON THE NO GO.

 

[Jeremy2171]

The only gages you would need are the GO and FIELD...the NOGO is "only" used when installing a NEW barrel.

Bolt MUST close on the GO
Bolt MUST NOT close on the FIELD

(FIELD is the max allowable length before it's considered unsafe to shoot) Most times a different bolt can correct excess headspace issues.

 

[FlyinBryan]

If the bolt closes on a "No-Go" gauge but does not close on the "Field" gauge this means you have a rifle that has excessive headspace but is safe to shoot. Basically it will stretch the heck out of brass and good luck trying to reload.

 

[Jeremy2171]

FlyinBryan If the bolt closes on a "No-Go" gauge but does not close on the "Field" gauge this means you have a rifle that has excessive headspace but is safe to shoot. Basically it will stretch the heck out of brass and good luck trying to reload.

That statement doesn't hold water...excess headspace is an UNSAFE condition..period.

Brass stretching? Not really, I've never had any issues using brass from different M1s (with different headspace) and getting them reloaded. If you are real finicky then X-dies are an excellent choice..

Excess headspace is determined by the FIELD gage not the NOGO. Remember NOGO is used only to finish ream a new barrel. If you installed a new USGI M1/03 barrel in the service and your "new" barrel closed on a NOGO it was rejected as that is not what the criteria for a new barreled rifle was. Once the rifle was in the hands of troops the only headspace gage that ever went into the rifle was the FIELD gage which determined if the rifle had excessive headspace and was unsafe to shoot.

 

[FlyinBryan]

That statement doesn't hold water...excess headspace is an UNSAFE condition..period.

Here's what the names seem to really mean on military ammunition like the .30-06:

GO — Should be called GOOD, this means that you have a chamber that is large enough to take a shell and for the bolt to close as required.
NO-GO — Should be called ACCEPTABLE, there is more headspace than the GO (GOOD), but it is still safe to use on military arms like an M1 Garand.
FIELD — Should be called NO or FAILED. If you can close the bolt on a FIELD gage, then there is too much headspace and the barrel should be replaced. Maybe this is an old barrel that has been shot out. Or maybe you just ruined your barrel by reaming out too much metal.
The SAAMI specification for .30-06 is:
Datum Diameter at Shoulder = 0.375"
2.0487" Minimum headspace
2.0587" Maximum headspace

We used Forster gages, which Forster describes as:
Datum Diameter at Shoulder = 0.375"
2.049" GO
2.055" NO-GO
2.058" FIELD


it is safe however to use the following rule of thumb.
if it closes on the go, and will not on the no go, its good to go.

its really pretty simple

 

[briansmithwins]

you should never just swap bolts like you can with an ar15, without checking the headspace

According to the TM you shouldn't be swapping bolts on M16s w/o checking headspace either.

BSW

 

[FlyinBryan]

ya, it should have been worded

"you should never just swap bolts like everyone and their dog does with an ar15, without checking headspace"

 

[FlyinBryan]

Excess headspace is determined by the FIELD gage not the NOGO.

this is wrong, but please dont get upset. im trying to help you understand this.

the field gauge is a tool to determine if you are over absolute max.

and no, a little extra headspace beyond the no-go is not an "UNSAFE condition period"

it is perfectly acceptable for some rifles like the garand to close on a no-go, but not on the field, and be perfectly safe to shoot.

however.

i prefer to see a chamber that will close up and click like glass on a go, and stick the lugs on a no-go.

its just a little more youthful.

here is the method use by a fairly respected garand armorer. it is from John Mclean, he is the head armorer at the cmp.
the cmp stands for civilian marksmanship program, they deal almost exclusivly in m1 garands and carbines.

this is a copy and paste straight from the horses mouth.

The three gauges you will encounter are the “GO”, “NO GO” and “FIELD”. CMP only uses “GO” and “NO GO” gauges but I will describe all three.

The “GO” gauge- is most commonly used when installing a new barrel and reaming the chamber to size. The bolt should fully close on the “GO” gauge; if it fully closes you can be sure you have enough room in the chamber to prevent the cartridge from being crushed during chambering. The “GO” gauge can also be thought of as a minimum safe headspace gauge and the rifles bolt must be able fully close with it in the chamber.

The “NO GO” gauge- is used to make sure a firearm does not have excessive headspace. The bolt should NOT fully close on the “NO GO” gauge; if the bolt cannot be closed on the “NO GO” gauge then you know your rifle does not have headspace that is excessive. The “NO GO” gauge can be thought of as a maximum headspace gauge and should not be able to fit in the rifles chamber with the bolt fully closed. If the bolt DOES close on the “NO GO” gauge, it does not necessarily mean that the rifle is unsafe; it does however show that a further check with the “FIELD” gauge would be necessary to determine if it is safe to shoot.

The “FIELD” gauge- is used to check absolute maximum headspace. If the bolt closes fully on the “FIELD” gauge the rifle IS NOT to be fired and should be considered unsafe to shoot. CMP does not use this gauge because rifles that pass the “FIELD” check but fail the “NO GO” are approaching the point where they will be unsafe to shoot. Our standard for maximum headspace is the “NO GO” gauge to ensure our customers will be able to shoot safely for many years.

 

[Jeremy2171]

Quote:
Excess headspace is determined by the FIELD gage not the NOGO.

this is wrong, but please dont get upset. im trying to help you understand this.

the field gauge is a tool to determine if you are over absolute max.

Not upset but I understand this completely and have been doing this for a number of years... My above statement is correct, Excess headspace is determined by the FIELD gage...period. If the bolt doesn't close on the FIELD it's safe to shoot..period. The FIELD gage is the REJECT gage...at the point the bolt closes the rifle is to be considered UNSAFE and should not be fired until the headspace issue has been corrected.

it is perfectly acceptable for some rifles like the garand to close on a no-go, but not on the field, and be perfectly safe to shoot.

however.

i prefer to see a chamber that will close up and click like glass on a go, and stick the lugs on a no-go.

its just a little more youthful.

Thats fine and its your "preference" however TM-9-1275 (Ordnance Maintenance Manual for the M1 rifle) states otherwise.

Our standard for maximum headspace is the “NO GO” gauge to ensure our customers will be able to shoot safely for many years.

Notice that is the CMP's call on how to gage....not the Army's who wrote the TM for the rifle. They are doing that so as to not have to answer all the questions on "why my rifle closes on a NOGO" they would get by uninformed people who don't know the difference and actual requirements to use the 3 different gages.

TM-9-1275 specifically states that the FIELD gage is the one to use in all cases "except" for rifles to be put into storage...those rifles will then have an "as new" appearance.

SO basically the Army says if the rifle is going into storage it will be be AS NEW and not fail the NO GO check. However once issued the only gage to use is the FIELD gage. THAT gage determines servicability.

Take a look the TM is online...
http://www.fulton-armory.com/tea/tm9-1275.htm

Servicability chart here....
http://www.fulton-armory.com/tea/tm-fig23.htm

 

[30Cal]

Garand bolts do vary a fair amount. I'd bring it and a FIELD gage to the store when you pick out your barreled receiver.

 

[ol' scratch]

Thank you very much for the help

Thanks everyone for the good advice. I will pick up a few gauges before I go.

 

[30Cal]

I'd give them a call first. They may have them there and might help you out.

 

[Stumedic]

Hi Guys, I'm new to the forum but I've used it as a good reference for quite some time. This place is a wealth of info.
I always thought the go and no-go gauges were used to set the initial headspace. A freshly barreled receiver may close on a go and miss closing by .001 on a no-go. This would be in spec, however shoot a few rounds, the bolt shoulders set back, and the bolt will now close on the no-go. I have to agree, although I may be wrong, that the field gauge should be used to determine serviceability. Stu

 

[FlyinBryan]

what if the o.p. goes to the cmp, and checks his bolt with a barreled receiver which of course, have never been fired together, and misses closing on the field gauge by a thousandth or two?

then he takes it out and fires a few hundred rounds through it?

do you guys think it still wont close on the field by a thousandth or two?

there is a reason that the cmp wont use field gauges.

i think it would be a different story if we were talking about checking a rifle that had a bolt and chamber that had met and at least fired together.

it is only my opinion, but i think the thread starter has been given bad, if not dangerous advice. (probably not dangerous, but certainly not as good as it would be if it passed with the no go.)

http://www.youtube.com/watch?v=cxSU2zBQvM8

 

[Jeremy2171]

Simple answer......if the right hand lug is very close to touching the rail (like maybe a thousandth or so) then find another reciever or bolt combo that the lug isn't that close to the rail.

If you have an issue with anything I've said don't blame me...just blame the Army which has used that TM for maintenance of the M1 for nearly 40 years.....

You tube links, random web sites or any other "blogs" don't mean anything to me other than what is in black and white in an official Ordnance Technical Manual. Follow the TM and you will be fine....

 

[FlyinBryan]

Simple answer......if the right hand lug is very close to touching the rail (like maybe a thousandth or so) then find another reciever or bolt combo that the lug isn't that close to the rail.

ya, what he said.

so just take a field gauge and a micrometer or caliper, and if it wont close, only by .001-.002 as measured on rotational allowance put it back and keep looking. being that its a bolt and receiver that dont know each other, there will be minimal setback after a few hundred rounds, and if a field wont close only by .001-.002 when you check them in the store, trust me, it will close up on that field and click like glass after 500 rounds. then you have a problem.

or use a nogo, and if it closes keep looking, if it dont, go shoot it.

now after that rifle has been fired a reasonable amount, and you feel the need to check it, use the field (if needed)

jeremy, im not saying the field gauge should not be used, im just saying it aint a bad idea to use the nogo when checking bolt, barrel, and receiver that HAVE NEVER been fit and fired together.

with respect.