Gew88 Max Loads?

[Josh Smith]

Hello,

I've been handloading my Gewehr 88. It is "S" marked but I still prefer 0.318" bullets, and they actually seem to give superior accuracy. I'm going to slug it again, but it appears the bore is pretty tight. Came out to 0.3165" last time, but I've shot fouling out since.

Anyway, I'm using Varget. It has become my go-to powder for milsurps, especially the 7.62x54R and 7.9x57J.

Now, as I understand it, the max operating pressure for a Gewehr 88 is 45,000 CUP. According to Hodgdon, 45.5 grains, the starting load, produces around 37,500 CUP with the max load producing 49,000 CUP. This is with a 150grn bullet.

Now, I'm running 46.5 grains of Varget. I was thinking I had low pressure signs in my Remington cases. After making some cases from Winchester .30-06, I found that the tolerances in the Remington cases were not in spec, so I trashed them.

Any guesses as to the pressure I'm running?

I'd like to keep below max pressure, or, in other words, I'd like to have a new minimum and maximum to work with, maximum being maybe 44,900 CUP or thereabouts.

Data listed by Hornady has their minimum as 43.5 grains but no pressure listing.

This sounds like a good starting load for the 7,9x57J, though. What do you think?

Should I just start again at 43.5 grains and work my way up? When should I stop?

My only goal is to find maximum precision in a given range. For example, if I use 43.5 grains to start and consider 47 grains to be max, then I won't go past 47 grains.

For comparison, the original J load was a 0.318" bullet pushed by Poudre B (can't find a burn rate on that; a burn rate for this powder would help a LOT). The bullet was cupro-nickel jacketed, 227 grains, and pushed to 2100fps.

Opinions would be appreciated!

Thanks,

Josh

Information

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[Patrick Chadwick]

CIP max. pressure Pmax for the 8x57I cartridge is 3800 bar. And for the 8x57IS it is 3900 bar. So no great difference. But no century-old rifle should be pushed to the maximum. Apart from anything else, it is unlikely to help accuracy and is an unnecessary strain on the rifle and your shoulder.

My only goal is to find maximum precision in a given range. For example, if I use 43.5 grains to start and consider 47 grains to be max, then I won't go past 47 grains.

Well, you've nearly answered your own question. Take the starting load as per reloading manual and work up in 1/2gn steps until you reach the maximum in the manual OR you see signs of excessive pressure.

Do it like this:
Prepare 5-8 cartridges each with loads 43.5 / 44 / 44.5 / 45 / 45.5 / 46 / 46.5 and 47 gns. Ideally you would test-shoot all on the same day, to ensure same lighting, same wind, same temperature and so on, but that could be so tiring that eyestrain etc. might invalidate the result.
So perhaps take 4 loads in each of 2 sessions.

Put up 4 targets. Not 4 target frames, but 4 "blacks" tacked onto the same frame. Then shoot 1 shot load 1 on black 1, 1 shot of load 2 on black 2 etc, going round the cycle until you have shot all sample loads on all the blacks. try and shoot very steadily - say 1 shot very 2 minutes, deliberately resting your eyes in-between shots. It is vital to use a sandbag for the fore-end - you want to test the load, not yourself. Then take a half-hour break and continue with the second set of loads. If the weather/lighting deteriorates or eyestrain becomes noticeable, stop and do the second half on another day.

Now plot a graph with the group size against load. Since anyone can have the odd flyer, strike out the worst shot from each group and plot the graph again. There should be a clear curve showing the variation of group size with load. This may (if you are lucky) appear as a couple of peaks with a valley in between. It is difficult to determine the best load, but fairly easy to see the bad loads (the peaks). I simply take a load halfway between two peaks, and know that I then have an acceptable load that is tolerant to slight variations.

Pressure? I haven't a clue, but if you follow the method outlined above you will have a good load that is well below the maximum. Theoretically, you could do it all again, this time varying the seating depth. Quite frankly, I consider that to be ACWOTAM with a long-throat service rifle. In a Gew.88 or '98 the bullet will probably fall out of the case neck before it gets anywhere near touching the lands, so just make sure that the loaded cases have at least 1 caliber of the cylindrical portion of the bullet within the neck, to ensure adequate pressure build-up and cartridge expansion without crimping. If the chambering is so tight that the loaded bullet does touch the lands, back off at least 10 thou to ensure ballistic consistency.

Well, it works for me! Good luck with your testing!

Patrick