I need to get a barrel to someone with a lathe for some very minor head spacing.  The barrel is an 1893 Mauser and it currently almost closes on a field gauge.  I want to trim back a shoulder just enough to get it back to barely closing on a No Go or better.  I live in Ankeny.

Not sure if you wrote your post correctly or not. It should close on a go but not close on a no go. If it doesn't close on the no go now I would just call it good especially if you will reload for it. Then you just have to adjust the resize die to fit the case to the chamber. If not then it isn't really an issue like many think.

Get in touch with CCA

Only downside to Septic is wait time, but there's a reason for that.

If it closes on a field gauge it will swallow a no go.  He said he would like it to partially close on a no go or better, either would be safe.  You can not fix headspace that bad with reloading, too much case will be unsupported.

Like was said CCA is your best local bet.  It won't be a simple as just taking the shoulder back, the sights will still have to be indexed at 12:00 which will require a full turn, which means your chamber will need finish reamed because a full turn will set the headspace back about 1/12 of an inch, which will take it from failing a field  gauge to not closing on a go gauge at all.

Actually you can. I did it with a Swede. Expand the neck and resize to fit chamber. This creates a shoulder to headspace on the cartridge. This allows you to fire form the case to the chamber w/o stretching the case. The stretching is what causes the majority of the failures in rifle cases. There is a lot more web in a rifle case than a pistol case and you can do it safely. This is an old technique. It is also best to do it with either cases once fired in a properly headspaced rifle or new cases eliminating cases that are already stretched too much. This is an old wildcatters technique to establish correct headspace. Most field gages are only about .010". That is the thickness of 2 1/2 sheets of standard notebook paper (.004" nominal thickness).

I'd prefer to contain the 50k PSI of hot gas with an actual chamber, not case web.  I'm aware of the technique.  But closing on a field gauge is excessive headspace that is dangerous.

Believe as you will. I have done it successfully with hundreds of rounds and would do it again.

I'm not replacing the sights.  I want to set it up like a Scout rifle.  The 93 receiver has a stripper clip guide and I want to keep that feature.  I have several 7x57's and one of my other rifles also comes close to closing on a field gauge. (my father got it for me in 1968)   It really stretches the brass and since I reload the brass I don't like to see the brass get that stretched.  This particular rifle I picked up in a pawn shop and wanted to convert it to a scout rifle.   I don't have my gauges in front of me but there is 10thousands of an inch between the dimensions of the GO gauge to the Field gauge.   I know it doesn't sound like much but the barrel has a lot of rifling in it doesn't seem to be eaten up from shooting corrosive ammo.

There is a smith in Osceola that seems to specialize in older firearms and was going to take the drive to him and see what he could do for me.  Although, I could drive up to Baxter and check with CCA.  It's not a long drive from me.