Switch- Barrel headspace requirements

[eddybo]

I never shoot for zero headspace. I do not want even a slight crush fit on a go gauge. I actually want the bolt handle to fall freely with a go gauge in the chamber. But I also want the bolt to stop very near the top when I put a single piece of tape on the back of the go gauge. I am thinking your rifle must have been chambered very tight to begin with.

Zero headspace is of no advantage, except maybe on a belted case and I would not even want it then. Just my opinion. If you can control the sizing of your brass you can recreate zero headspace even if you had really excessive headspace. I do minimally resize all of my ackley rounds for a slight crush fit but other wise size my brass enough to be at least .001 short of a crush fit. If you are sizing your brass acurately and not shooting factory ammo I do not see a problem with having headspace in excess of .020 over.
I ran a 223 with .018 excessive headspace for over 1K rounds without a problem. The excess headspace was created when I bushed the firing pin and realized that the bolt face was extremely out of square....then had a comedy of errors that necessitated removing more material than I liked.
I was too lazy and busy to ever get around to pulling the barrel and setting it back, so I just shot it as is, being very careful with my reloading. It was basically just a truck gun until I bought a PTG bolt to replace the one I mangled and rechamberd it to .300 whisper.

If you truely had zero headspace any wear would cause the problem. Zero minus anything equals a negative. If you had .002 headspace I do not think you would be seeing any problems. Maybe the fact that I do not run a recoil lug would explain a lack of wear on mine.

Thanks for your input eddybo. I am thinking that the kind of clearance you have should be considered minimum clearance in a switch-barrel rifle. Apparently mine was set to zero or very close to it, which I firmly do not believe is practical in a switch-barrel.
Of course fine gunsmiths like to set headspace as close as possible for increased accuracy,and take great pains to do so. I just do not believe this is a prudent practice in a switch-barrel.
Tight headspace in a switch-barrel ends up being a problem when FL resized cases will not fit back into the gun.

 

[NesikaChad]

Chad thanks for the Rockwell info on receivers and barrels that was interesting.
I totally agree with your dissertation on thread wear not effecting headspace.
What my experience does not agree with is your explation of how headspace could change.
Tha gun is chambered for the large Weatherby cartridges. Barrels are torqued to 50 ft.lbs., which I do not consider the force of Apollo. Thread lube is used each time. The barrel was changed 4 times last year and 3 times this year. Now the bolt will not close on the proper "GO" gauge for the respective barrel.
Obviously between barrel shoulder/ Lug wear and/or barrel tennon/receiver stretching something has changed.
My origional question was should the gun be set up with "special " loose headspace to delay /avoid this eventuallity?
Bullets could be jammed into the rifling to "fire form" cases.Sizing dies could be backed off to fit the larger chamber then cranked down as headspace is reduced, for whatever reason.
My own experience closely parallels that of JE Custom.
I am starting to think switch-barrels are not worth the trouble.

Well bud you got me there. From all outward appearances it seems like your head is on straight and your doing everything right. Obviously something is moving and I like you am at a bit of a loss to explain exactly what it is.

Annoying when that happens.

I'll shut up before I sound like a real dork now.

Hope the solution reveals itself.

C