Gewehr 88 Low Pressure -- What Should I Bump It To?

[Joshua M. Smith]

Hello,

My load for the Gewehr 88 with a bore that slugs 0.318" is as follows:

Winchester case formed from .30-06 Winchester case

0.318" 150 grain spitzer bullet

46.5 grains Varget

Federal large rifle primer

Now, I'm having signs of gas leakage around the neck. I'd like to bump it up a little bit to make that stop, but it's probably due to the "S" rethroating.

I don't remember the upper limit for the 7,92x57J cartridge, or for the rifle. I was thinking 40,000PSI, but am not sure.  Could be 45,000 PSI.  One is CUP.

I do believe I'll stick with 40,000 PSI though.

I was going to start bumping it a grain at a time, but I'm really not sure when to stop. I know that by the time it shows pressure signs I'll be dangerously exceeding the action design.

I'd love me a pressure gun, but since I don't have one, I'll have to take educated approximations from you all.

So, where do you suppose I should stop?  What load would max at 40,000 PSI?

Thanks,

Josh

[Mikey]

Where did you get your load data from?  Where is your load in relation to minimum and maximum for that weight bullet?  What do the notes in your load manual suggest for loads for your rifle?  What do you mean when you mention the 'S' throat - was this a rifle in .318 bore you believe was simply throated to allow firing of the .323 bullet?  If so, you probably do not have any pressure concerns and may need to increase your load to get the case to seal in the chamber and reduce blowback.  Just a thought.

[mauserand9mm]

I was under the impression that the empirical pressure signs are the same irrespective of the pressure limits. I could be wrong (or have more to learn) but I thought that extraction would get harder as the pressure approached the upper limits of the design pressure values, as a resut of the compression, or spring, in the action - lower pressure actions reaching this point earlier than a higher pressure action.
 
I think the 303Brit is also limited to 40,000psi, but there is more spring in the SMLE rear locking action than the front lockers.

[Mikey]

mausserand9mm:  I believe you are correct about empirical pressure signs being the same.  I checked my reloading data from VihtaVoury which shows the older 8x58jrs pressures to 42,000 psi but the 8x57 js goes up to 49,300 psi, so it seems the op can go a bit higher if he wants if this is a rifle that had a throat opened to handle the .323 bullet.