No Go Gauge GOs!!

[garra]

Early last month I picked up a NO1 MKIII from a gun shop about 30 miles from here. It was made in 1942, looked cleanish but the wood was not finished to a high quality. Had a Crown with GR below, on the line below the crown a single bottom portion of an L, then no other marks except model info. Bolt does not match serial which starts with an N119XX. No serial on bolt at all except for some hard to distinquish proof marks and an S on the piece that flips aside to remove the bolt. Bolt is in really nice looking condition. As the post is headed the new Forster no-go gauge that I just received from Numrich fits really nicely and closes.

Should I invest in a field gauge or just look up a gunsmith to headspace this baby.

Information

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[Edward Horton]

Place a empty unfired .303 case in your chamber (NO live rounds) and try to stick a .017 (seventeen thousandths) feeler gauge between the right locking lug and the receiver. If the .017 feeler gauge fits you are very close to or over the maximum of .074 head space.





If you have a set of vernier calipers you can get a very accurate head space reading by measuring an empty unfired .303 case.



Next insert a fired spent primer into the primer pocket.





Now chamber this cartridge, close the bolt and "seat" the primer, remove the case and remeasure its length. Subtract you first case measurement from the second case measurement and this will give you "head gap" clearance or the "air gap" between the rear of the case and the bolt face.

Now measure the cartridge case rim thickness and add it to the difference you have in case length measurements.

Example:

2.236 - 2.222 = .014 (head gap clearance or air gap)
.014 + .058 = .072 actual head space.

Trust me, it works and I have Enfield head pace gauges to cross reference.



The following message was brought to you by the cheap bastards head space club. "We don't need no stinkin' gauges".

[jona]

Get the field gauge.

[Parashooter]

If the Forster gauge is .070", just cut a 1/2" circular shim from an aluminum beverage can, measure it carefully (many are pretty close to .004"), stick it to the gauge with a tiny dab of sticky grease, and you have a ~.074" gauge at no added cost. If you want to get really fancy, get a cheap feeler gauge ($3 at Harbor Freight) and cut a shim from the .004" feeler.

If you have the bolt head stripped, take advantage of a learning opportunity and try feeling the end-play with the bolt closed on the gauge. Given enough practice, most humans with normal manual sensitivity can learn to make very close estimates down to about .001" just feeling the "slop" in the bolt when there's no interference from extractor or main spring.

If you're planning to handload, ask yourself why you're worried about headspace when you can easily control cartridge end-play by fireforming with a spacer and subsequent neck or partial sizing.



Some like O-rings for this job, but I could never see buying something when a no-cost improvisation from stuff I already have sitting around works just as well for me.

[garra]

Gentlemen,

Thanks for the advise. All may be well after all. What I perceived as the bolt closing wasn't all the way home with the locking lug. I did find I had some plastic shim stock, so I cut out squares that would fit on the back of the gauge, a little spit and they stuck just fine to try the action. My gauge is a .067 and would just not close, with the addition of .002 it only got half way down the ramp.

Now if anyone could help determine where the rifle was made....Correction on serial top line N, 2nd line L (has tail going left on top) 4988

thanks and regards.

[Steve H. in N.Y.]

Garra, from your description I'd say you've got a "dispersal" rifle. The "bottom half of an L" stamp is a poorly struck B for BSA where it was assembled. The N serial number prefix is right for 1942.