Shotgun Headspace

[bs32]

Just how critical is headspace to a 12 gauge shotgun with a regular, modern 2-3/4 inch chamber? Where is the headspace measured and how? I've got an 1897 which I've completely redone - but before I shoot it - the seller said I'd be best to check the headspace. Never done that on a shotgun before- sure plenty of rifles and pistols - but not a scattergun

Does it really matter - the barrel (and therefore the chamber) are brand new.

bs32

 

[Jim K]

Shotgun headspace is checked the same as for any other rimmed cartridge gun. The gauges are short and stubby, about 3/4" long. The set consists of a GO and a NO-GO; there is no Field gauge.

I am not sure what you are asking about the Model 1897. The new barrel could affect headspace if the lockup is not tight. Usually, though, excess headspace, as in a rifle, comes from a combination of worn/battered locking lug(s) and/or worn/battered lug seat(s). The barrel adjustment involves the takeup tightness, not headspace.

One area of concern with older shotguns is chamber length, but the Model 1897 was made originally with 2 3/4" chambers, so that should be no problem.

I would guess that the person you talked to was concerned because of the installation of the new barrel and whether it will be OK with the old bolt and receiver. That is certainly a potential trouble area and you should have it checked.

Jim

 

[bs32]

Jim: Thanks for the post. The gun is a takedown version and the barrel locks tight to the action when installed / removed. I know how to adjust the barrel with the adjustment collar and lock, but since it is nice and comfortably tight, I'd say it doesn't need any adjustment- but hence, because I'm not knowledgable on shotgun "headspace" - I don't really know. but the action locks up nice an tight - the bolt doesn't wiggle around with the slide/bolt in battery.

B.

 

[Jim K]

You might try an old trick that sort of works, though not very precise. Cut out some round pieces of printer label paper (sticky back) a bit smaller than the diameter of the shotshell head, and stick first one, then two, then three, etc. to the back of a new unfired shell and close the action. It should close on one layer, maybe on 2 and should not close on 3. If it closes on 4 or more you have a serious headspace problem.

P.S. For safety reasons, I suggest cutting the shell to remove the charge and powder before trying this, or do it in a safe location.

Jim

 

[SRG]

If I may add to what Mr. Keenan said, the headspace in the '97 is regulated by the carrier/lifter locking behind the breach bolt. I have seen many cowboy action shooters ruin headspace by polishing the life out of the carrier and any other part that looks like it needs polishing.
The fix is to build up that area of contact between the carrier/lifter and bolt.