Home Forums Hunting & Shooting Gunsmithing First chambering project, headspace question.

I have a commercial Mauser action, a Green Mnt. short chambered 35Whelen barrel, an Ackley Improved Clymer reamer, and Forster '06 family go gauge. For a one time project, could I reverse seat a flat base bullet in a new case for a go gauge and use the standard go gauge for my no go? My understanding is the AI version is .004 shorter to achieve a crush fit at the neck/shoulder junction.

If this won't work, why?

Thanks.

Lathe or by hand? Do you have a way to get a headspace measurement for the action, like depth mics, and a way to measure go gage depth on the barrel? If you do it’s easier/better. I’m not sure what you mean with the case and flat bullet, but you can go a lot shorter than .004 and be ok.. it’s one of those rare times when shorter is actually better. Ha!

Just buy the appropriate go/no gages and peddle them when your project is complete. Alternatively, rent them.

By hand.
Figured a bullet seated backwards would support the case better for a crush fit and not interfere with the throat.
No other depth mics or a previously mounted barrel to measure off of.

Please don't do it by hand and don't use a case for a headspace gauge.

Jim, I know gunsmiths have their preferences for finishing a chamber, and I get that it would most likely be more accurate on a lathe. I don't have access to one that is that accurate. So a slow hand it will be. If I can close the bolt with resistance on two of more brands of cases and not on the standard go gauge, how far off could I really be?

As a mechanic I understand there are right and wrong ways to do things, but there is usually more than one acceptable. It's not like I'm surfacing heads on a concrete floor or machining rotors with hand held grinder.

I do truly appreciate your advise as an established craftsman in your trade.

Thanks.

You’re good. Use feeler gages between action and barrel to give you an idea of where you are. If you go too short grind a shell holder down. Bfd. Use the go gage as your guide.

In theory, you can use the 06 "go" gauge as a reference to chamber your 35 AI Whelen but there are a couple of issues. The first issue is that the datun, that is, the point of reference, is a point on the shoulder which is of a diameter which is smaller than the neck diameter on the Whelen. The other issue is that the headspace dimensions are often indeterminate for the Ackley chambers. Even Ackley's own drawings are often incorrect due to variations in neck diameters. Since the AI cartridges headspace on the juncture of the neck and shoulder, for fire-forming, dimensions elsewhere on the angle of the shoulder will vary along with neck diameter. If one orders agauge specifically for the 35 Whelen AI, he will get a Whelen "go" gauge which is ground .004" short. While this is theoratcally correct, it may well result in a chamber which is too deep and will result in too much head clearance. All this aside, reaming of a chamber by hand is possible but quite difficult. Good luck. GD

Thanks, Greydog. My theory is this. Every '06 based cartridge I have found dimensions for are a .441 shoulder at 1.948 sloping away at 17°30' to the neck/shoulder junction of whatever diameter/point that is when it gets there. PT&G, I believe, shows the same gauge for 22, 24, 25, 26, 27, 30, 32, 33, and 35 caliber. I'll just throw in a WAG that it would work for 28 and 375 if done on a true '06 case. If a full length sized case with a short or backwards seated bullet can be closed upon without creating a bur, but requiring effort, and the go gauge can't, I should be very close.

As to hand turning. Slow? Yeah. I've got more time than money. If I booger it up, there is still 358 Norma and 35 Nosler to clean up my mess.

Thanks again .

My 35AI has a bit of excess headspace (done by West about '75) and it is no big deal (7600) to bump them up and neck them down when running new brass...

If I go far enough, Art, I'll just call it a 35 Gibbs!


ETA, It should have plenty of freebore!