Gearing up to shoot my carbines again and have some questions.....

[ChipS]

I might have to look up the forster gauges. How much are they?

Headspace Gauge Field 30 Carbine HG0030F | eBay

Here ya' go. $27.90 apiece and he sells all three on e-bay. Again, I recommend you get 'go' and 'field'. The 'No go' is kind of gilding the lilly unless you are finish reaming a short chamber. Shipping is quoted $5.00 but if I recall this guy is a pretty straight shooter and I'll bet he will discount the postage on two gauges purchased if you ask. HTH

Ha. I just read the bottom of the ebay ad. $5.00 flat rate shipping no matter how many gauges you buy. Not bad.

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[ABPOS]

Headspace Gauge Field 30 Carbine HG0030F | eBay

Here ya' go. $27.90 apiece and he sells all three on e-bay. Again, I recommend you get 'go' and 'field'. The 'No go' is kind of gilding the lilly unless you are finish reaming a short chamber. Shipping is quoted $5.00 but if I recall this guy is a pretty straight shooter and I'll bet he will discount the postage on two gauges purchased if you ask. HTH

Ha. I just read the bottom of the ebay ad. $5.00 flat rate shipping no matter how many gauges you buy. Not bad.

Darn, midway just has no-go right now in stock. I'm not really sure what you mean by that. Do you mean it's likely to close on it but still be safe to fire? That's only .03" difference.

---------- Post added at 11:42 PM ---------- Previous post was at 11:40 PM ----------

Oh wait, brownells has a field in stock. Hmmmmm.....

[DaveHH]

You use the GO gauge to make sure there is ENOUGH headspace and the Field to see if the weapon has stretched or worn beyond what is safe. You want it to close on a go and NOT close on a field. The most unsafe condition in a carbine is not excessive headspace, it is too little headspace. Also remove the slide/spring and manually close the bolt on the gauge with little pressure. The Forster gauges do not require removing bolt parts.

[Patrick Chadwick]

The most unsafe condition in a carbine is not excessive headspace, it is too little headspace.

Well said Dave, let's hear it again!

The most unsafe condition in a carbine is not excessive headspace, it is too little headspace.

Kuhnhausen's book "The U.S: .30 Caliber Gas Operated Carbines", Vol. 3 has a detailed explanation of safety aspects starting around P.29.

Simply put, excessive headspace is bad for brass if you are reloading. I have fired rifles with a headspace up to 1/20".*** The only result was that the case shoulders were noticeably shifted forwards, and ignition was irregular, presumably only happening at all because the case was being held back by the extractor. Not that I am recommending this situation, but the danger with
too little headspace - maybe even a negative head clearance - is that it may provoke a slam-fire, which is far more dangerous than a stretched case!

BTW, protruding primers have the same effect. Rather set primers a couple of thou" below the base level than risk any protrusion.

Another cause of this hazard can be a misguided desire to set the bullet as close as possible to the transition cone, a.k.a. lead or leade. I cringe to read of people claiming they set the bullets to be 0.003" or less off the lands. Have they ever heard of tolerances, which exist in both bullet ogives and their reloading equipment? If a bullet is seated too long in the case, then the cartridge is effectively "headspacing" on the bullet!

I wish that more attention would be paid to such aspects, rather than placing a blind faith in gauges, which are NOT a safety guarantee.

***On my own rifles I check such matters before the first firing. In this case, the rifle was handed to me for a test firing at the range, by someone who I would regard as very knowledgeable. Motto: do not trust anything or anyone when it comes to your personal safety!

And since this post is, of course, basic, even superficial, read Kuhnhausen on the M1.

[DaveHH]

or Andy's in Petaluma where I grew up. He was a real genuine gunsmith and could do anything (usually while you waited). Any other "gunsmiths" I've met I wouldn't let wash my car. Yet people always say "take it to a gunsmith". Most have absolutely no idea about this blow up issue with carbines. The government forced 100% ammo case checks at the ammo plants because they were having so many failures from slam fires. The reason that this is so important is the carbine DOES stretch cases and you could gauge a gun all you want and an overly long case could blow it up. So if you reload, checking case length is a whole lot more important than headspace.