Headspace gauges

[toro1]

I am planning on changing a bolt in my Garand and so I ordered a Forstner Go and Field Gauge. I have never checked head space before, but my understanding is if I use the field gauge instead of a no go gauge I will be OK. From what I have read, I may be close to the limit if I use the field gauge, but the field gauge is always the final check anyway. Am I understanding it correctly?
Also, I want to check the headspace with a fully assembled bolt so I am planning on notching the rear of the gauges. I will be using a lathe with the cutter in the head and use an X axis table with the gauge, but are there any things I need to be careful of? In order to accomodate the bolt rotation, should I plan on milling out a 45 degree area so everything clears?

TIA,
Jay

[Jersey Devil]

Hi Jay,
I don't know much about milling the notch, but I can tell you that I agree with your idea on the use of the GO and FIELD gages. When I assemble M1s or M14s I typically just use those gages unless I'm trying to find the exact headspace measurement. If I need the exact measurement then I use my Pacific Tool & Gage set. Each set uses multiple different gages between the respective GO and FIELD REJECT measurements plus a couple on either side just for extra precaution.
Good luck, and please let us know how your project is going!
--Brian

[toro1]

Thanks Brian, it sounds like I am on the right track. I just need to get some time in the shop and trial and error the notch until it works. I'll get some pics after the mod.

Jay

[Jersey Devil]

Sounds good, Jay. Looking forward to the updates!

[Orlando]

To get a accurate reading I strongly suggest dissasembling the bolt and not cut the notch. Its easy to do you with nothing more than your fingers and a punch or a flat bladed screwdriver
To use the gages make sure chamber is clean, remove op rod spring and follower rod ,op rod, set gage in chamber and basically let the bolt lug fall on its own. You can with very , very light finger pressure push the lug down. DO NOT push hard on lug. If there is just the slightest gap between the lug and receiver the bolt passes

[toro1]

To get a accurate reading I strongly suggest dissasembling the bolt and not cut the notch. Its easy to do you with nothing more than your fingers and a punch or a flat bladed screwdriver
To use the gages make sure chamber is clean, remove op rod spring and follower rod ,op rod, set gage in chamber and basically let the bolt lug fall on its own. You can with very , very light finger pressure push the lug down. DO NOT push hard on lug. If there is just the slightest gap between the lug and receiver the bolt passes

I will be changing on a bolt on a rifle and may need to go through a few bolts before I find one that headspaces correctly. Since it may require checking a few bolts, my thought was having a notched gauge would simplify life. What is the concern on a notched gauge not being accurate? I realize the notch would need to be properly aligned, but is there an additional issue?

[Orlando]

A bolt can be stripped in seconds, thats the only way IMO

[toro1]

A bolt can be stripped in seconds, thats the only way IMO

Thanks Bill, but some of us are not nearly as proficient as you when it comes to taking apart and reassembling pieces of these rifles. The last time I took a bolt apart and put it back together, it took quite a bit more time than it would for you. I know I will get better at it over time, but if the gauge can be modified with affecting accuracy it seems like a good idea for a person like me. It would also allow me to have a tool to take to the LGS and gun shows so I can check rifles before I buy. I do not know of many people selling M1s at gun shows that will allow a bolt disassembly by some guy that walked up to their table, but they will allow for a gauge to be inserted. That being said, if there is a technical reason for not cutting the notch because it would create a problem, I would not do it.

[Orlando]

https://www.youtube.com/watch?v=qYM8JnI2CJg

[Bulletguide]

A question of Forstner gauges... I've always used them but once took a Garand (might have been a 1903 Springfield, doesn't matter) to my gunsmith to double check my measurements and his gauges were quite different and showed different readings. He said he never trusted Forstner and used another brand. It's been too long ago for my fading memory to recall the type he used.
Has anyone ever found this to be the case, or used another brand of gauges? His go and no go were actually somewhat different in size. Wouldn't all 30-06 gauges be the same or really close to it? I find myself questioning my gauges now, though have set up several rifles with them since and not had a problem. I do think they tend to set the chamber a bit tight, most recently on a 1903/A3 if find it closes fine on the go gauge but some correctly sized and checked brass closes a bit hard on the bolt. Maybe nothing to worry about... shoots great.

[Hytekrednek]

many gunsmiths and armorers do not like Forster gages either, for the same reason you mentioned. Pacific tool and gage is one of the best, and my preferred brand of gage. But, Clymer gages are also better than Forster. Clymer and Pacific seem to be the 2 preferred most, with Pacific being best in the opinion of the guys I have talked to or read info from. I think Manson makes some too. Forster hs gages are unreliable in my experience too. the Pacific gages I have are dead on when verifying measurements.

[Orlando]

IMO Clymer is the go to gage

[Bulletguide]

Looks like I've got a nice set of used Forstner gauges for sale........