Field Gauge - Bolt Almost Closes

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09-06-2011, 17:30
Pancho Villa

Field Gauge - Bolt Almost Closes

Hey,

I bought a sporterized Arisaka in 8mm mauser recently. While I was waiting for the background check at the store/gunsmith shop (it was a transfer from a place out of state,) the gunsmith on site offered to take a look at it for free.

First, he sighted it in via one of those laser bore sighting things that inserts into the muzzle, without asking me first. Ugh.

Then he checked the headspacing. He told me it closed on the GO and NO-GO gauges and "almost" closed on the field gauge. I didn't watch him do this. I have a strong suspicion that he tried to force it shut on the field gauge, but can't tell for sure.

He then told me that the gun was unsafe to fire and I should return it and place the money down on a new rifle from his shop.

I told him I'd contact the seller, collected my weapon and left. Since then I've been trying to get a second opinion and doing research online all afternoon. My impression is that he's full of crap, and so long as it doesn't close fully on the field gauge its safe to fire. Is that incorrect?

(He also insisted it was a Type 99, when it was clearly a type 38, and couldn't tell me what the bore diameter was.)
09-06-2011, 17:48
BPTactical

I don't feel the GS was full of it.

The bolt should not close on a NO-GO gauge under normal circumstances! It should close on a GO with only the weight of the bolt or moderate (4# or so) thumb pressure. The FIELD gauge is used to check after the bolt closes on a NO-GO gauge. Under NO CIRCUMSTANCES should the bolt even come close to closing on a FIELD gauge. If it does DO NOT FIRE THE WEAPON!
The headspace is excessive and to do so would be an unwise move.
He used the correct procedure. I won't even chance it-if it will close on a NO-GO, well I guess that's why they call it a NO-GO.
If you are planning on shooting it I would:
Make sure you have good insurance.
Keep a FIELD gauge handy.

I think I would relegate it to a wall hanger.
09-06-2011, 18:28
sniper7

take it to someone else but I wouldn't fire it until you do.

If you decide to do so, let it be known that I am your legal heir to all remaining firearms and related toys[Tooth]
09-06-2011, 18:51
4gunfun

It is my understanding that if it will not close on the field gauge you are safe to shoot it. That is the guage I checked my old Mausers with. I have one out of the ten I bought that it closes on. I have shot the other 9. But I just play a gunsmith on TV. [AR15]
09-06-2011, 18:52
Pancho Villa

Quote:

Originally Posted by BPTactical

I don't feel the GS was full of it.

The bolt should not close on a NO-GO gauge under normal circumstances! It should close on a GO with only the weight of the bolt or moderate (4# or so) thumb pressure. The FIELD gauge is used to check after the bolt closes on a NO-GO gauge. Under NO CIRCUMSTANCES should the bolt even come close to closing on a FIELD gauge. If it does DO NOT FIRE THE WEAPON!
The headspace is excessive and to do so would be an unwise move.
He used the correct procedure. I won't even chance it-if it will close on a NO-GO, well I guess that's why they call it a NO-GO.
If you are planning on shooting it I would:
Make sure you have good insurance.
Keep a FIELD gauge handy.

I think I would relegate it to a wall hanger.

BTP,

What would you say to the researches at, for example, The (now Defunct) Small Arms Test Unit at the University of Arkansas at Little Rock, the former director of which said:

Quote:

While not accepted by all, the use of a field gauge to indicate a "safe to fire" firearm WAS used by all the major military forces during the lifetime of a surplus firearm, and was accepted practice. Is your surplus firearm safe if it "won't close on a field gauge"? It was "safe enough" for use by GIs for the M1 rifle, the British for the Lee-Enfield, etc..., and may have come to you unchanged since that use (as far as headspace). YOU determine what you feel is safe for your useage. IF A FIREARM CLOSES ON A FIELD GAUGE, I recommend that you NOT FIRE that arm. According to acceptable practice, that arm is out of spec, and has excessive headspace, and may be dangerous if fired.

Basically, unless you are installing new barrels, you don't need a "go", and even then, a factory cartridge can provide that (some would flame me on that one!)... no go is nice to verify the condition of the firearm (hey, it passed a no go!)... field is likely the more useful for many surplus arms. I have all three for several calibers, and I have never needed or used the "go", but often use the field and no go...

Source: http://hybrid.ualr.edu/satu/headspace.html

SATU did some apparent study into suppressors that didn't go anywhere, but they did have some sophisticated equipment to measure chamber pressure, and I assume if closing on a NO-GO gauge was dangerous he would be able to report that.

Have you seen any actual incidents of catastrophic structural failures / kBs with firearms that passed the "field gauge" and closed on the "no-go" gauge? All I have been able to find have been related to ridiculous handloads, and the worst I have seen (on milsurps that closed on FIELD gauges) is case separation with no injury to the operator. I have pics of an old enfield that had a paper rubber banded over the action and fired, powder was blown into the paper - but didn't even tear or burn away any of the paper.

I have read some people saying its unsafe, but no substantiated instances of issues that damage the firearm or injure the shooter. If you have any resources confirming these I would be really interested in them.

I'm obviously not going to rush into anything, but I'm also wary of just taking someone's word for it, in either direction.
09-06-2011, 19:04
Fist_gonzo

A Arisaka in 8mm? Never seen that before
09-06-2011, 19:11
Pancho Villa

Quote:

Originally Posted by Fist_gonzo

A Arisaka in 8mm? Never seen that before

It was apparently a bubba chop job done way back in the day. Rechambered and then stuck a mauser barrel (supposedly) on it.

This was back when Arisakas were dirt cheap, so it wasn't that big a deal at the time.

It has a set of Lyman adjustable sights on it, which is what got me interested in the first place. Been on an iron sight kick lately.
09-06-2011, 19:59
BPTactical

Pancho- unless it is the second Monday of the week I believe I came close to saying basically the same thing. So I would say the study you quoted is on the money but then again what do I know?
Close on GO-safe to fire.
Close on NO-GO- should be checked with FIELD.
Close to close or close on FIELD-Do not fire.
FIELD gauges (to my understanding) are just that-a quick and dirty military Armorers chamber testing tool to see if a weapon is serviceable in battlefield conditions. If the bolt closes or comes close to closing on a FIELD gauge the weapon is removed from service.

I personally defer to the safe side of the equation and if the bolt closes on a NO-GO gauge I recommend to the owner not to fire it.

I have seen caseheads blow out and necks split but not a Kaboom. The fact that this is an old military rifle that has been Bubbafied should be reason to approach with caution.
The 6.5 Jap was a pretty low powered cartridge and although the Arisaka is a strong action no sure if I would be willing to chance it.
09-06-2011, 20:05
Pancho Villa

Quote:

Originally Posted by BPTactical

Pancho- unless it is the second Monday of the week I believe I came close to saying basically the same thing. So I would say the study you quoted is on the money but then again what do I know?
Close on GO-safe to fire.
Close on NO-GO- should be checked with FIELD.
Close to close or close on FIELD-Do not fire.
FIELD gauges (to my understanding) are just that-a quick and dirty military Armorers chamber testing tool to see if a weapon is serviceable in battlefield conditions. If the bolt closes or comes close to closing on a FIELD gauge the weapon is removed from service.

I personally defer to the safe side of the equation and if the bolt closes on a NO-GO gauge I recommend to the owner not to fire it.

I have seen caseheads blow out and necks split but not a Kaboom. The fact that this is an old military rifle that has been Bubbafied should be reason to approach with caution.
The 6.5 Jap was a pretty low powered cartridge and although the Arisaka is a strong action no sure if I would be willing to chance it.

That's the other thing. There's those vent holes in the top of the receiver / the bottom of the bolt, and there's this:

Quote:

Well known graduate engineer and gunsmith, Parker O. Ackley decided to find out once and for all how strong our various military actions were. Rounding up an assortment of Springfield, Mauser, Enfield P-14 and No 1 MkIII, Krag and Arisaka M38 and M99 actions, be barreled and chambered each action type for the .270 Ackley Magnum or .30-40 Ackley Improved cartridge.

Each action was then fired with a series of progressively hotter loads until the action was wrecked. The only action that survived these tests was the M38 Arisaka. The 1 3/16 inch bull barrels fitted to the M38 actions were split or blown off, but the actions remained serviceable and intact. The machined M99 Arisaka action proved to be the second strongest action of the group tested.

Shortly thereafter, the NRA reported testing a M38 in 6.5x50 caliber that had been rechambered for the .30-'06 cartridge by its enterprising owner who indeed hunted with this insane combination. Just imagine firing a .308" diameter bullet down a .264" bore at the pressures generated by the .30-'06 cartridge. The Arisaka digested the load without a hitch although the owner complained that the rifle kicked a lot!

Sending one of the M38 actions to a leading beat treating firm for analysis, Ackley received the following reports:

"The design of the receiver appears to be in some respects superior to the Springfield and Mauser from the standpoint of simplicity of machining and inletting. The receiver was not only carefully but even elaborately heat treated. Its heat treatment appears to be superior to the average Mauser, Springfield and Enfield."

The results surprised everyone involved, and the Arisaka action earned a bit of well-deserved respect.

Source: http://findarticles.com/p/articles/m.../ai_114283920/

This leads me to be a little more adventurous than I might with, say, a modern sporter with no vent holes in the receiver or bolt. Forcing a .308" bullet down a .264" bore sounds flatly insane.

Edit: I forgot: apologies for apparently misunderstanding what you were saying.
09-06-2011, 20:13
BPTactical

You asked a question-I tossed my .02 your way.
Your firearm.
Your choice.