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Old September 17, 2011, 05:37 AM   #1
Josh Smith
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Gew88 Max Loads?

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
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Old September 17, 2011, 06:36 AM   #2
chack
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Why are you using 30-06 cases instead of boxer primed 8 mauser?

Have you chrono'd your loads?
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Old September 17, 2011, 06:42 AM   #3
Josh Smith
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Much easier to get and can find them locally. Very easy to form to 7,92x57.

I've not gotten ahold of the friend's chrono yet. I only see him now and again. Keep meaning to get one myself and keep forgetting until I need it!

Josh
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Old September 17, 2011, 10:43 AM   #4
Jim Watson
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You could apply the old rule of thumb that for small changes, a change in powder charge will give twice as much change in pressure; 5% more powder = 10% more pressure.

You could use the Lee Reduced Load formula. Sorry, I no longer have the book, maybe somebody will post it.

You could ask somebody to run it through Quickload.
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Old September 17, 2011, 11:12 AM   #5
Josh Smith
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Hi Jim,

I had no idea that there was a rule of thumb like that. In my shooting career, I've only been handloading for a couple years, and handloading rifles for maybe a year now.

I know better than to apply rules of thumb as strict rules, but that does help a LOT!

Thanks!

Josh
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Old September 17, 2011, 12:01 PM   #6
Jim Watson
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The rest of that rule of thumb is that +5% powder = +5% velocity but +10% pressure.

Do not use any such rule of thumb or even a more precise formula to extrapolate beyond tested limits. OK to interpolate between tested high and low.
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Old September 17, 2011, 06:29 PM   #7
James K
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One thing to note is that the reason the Germans went to the larger bullet was because they wanted to deepen the grooves. The bore diameter of the J and JS is the same, .311". They did not rebarrel the 88's, they just ran a new reamer into the chamber to ream out the neck of the chamber and allow the larger case neck to expand. That prevented high pressure that would result if the case neck could not expand to release the bullet.

FWIW, I have fired a fair number of WWII 7.9 in my "S" marked '88, and nothing happened, but that does not mean something couldn't.

Jim
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Old September 17, 2011, 06:39 PM   #8
Ideal Tool
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Hello, Josh. That is a pretty old rifle you have there. If it were mine, I would work up slow from start loads and quite at the point I acheived accuracy..well under any maximum load. What is to gain with more velocity? The steel used, and it's heat treatment were not up to a Mod. 98standard...Just think how bad you would feel if a primer or case let go..and the escaping gas happened to crack the stock?...Or WORSE!
Are you planning on hunting with it? It sure doesn't take alot of foot lbs. to punch a hole in target paper!
Any more, I am using cast bullets in my vintage militaries..kinder, gentler to bore & action..and shoulder! Plus it's FUN! I can sometimes get better accuracy by fine tuning bullet fit with a cast lead bullet than with jacketed.
Best of luck..and respect the age of these old timers.
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Old September 17, 2011, 06:49 PM   #9
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I have a Bubbafied* Gew. 88 JS that I load for... I use 170 gr RNSP ... and though the books call for a max of 36 gr IMR 4064.... anything less than 40 grains leaves the cases sooty (not enough pressure to expand them and seal the chamber) .... I have found that best accuracy is at 42 gr. ...... I get about 2150 f/sec .....




* Barrel jacket removed, and barrel cut down to 18" ...... stock (very beautiful wood!) sporterized......
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Old September 17, 2011, 07:45 PM   #10
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This might help:

http://www.gew88.com/gew_88_forum/
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Old September 18, 2011, 12:30 PM   #11
jimbob86
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150 gr bullets?

The original loading was a long 227gr ..... 150's would ginve quite a lot of freebore, no?
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Old September 25, 2011, 08:16 PM   #12
adrians
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i have some ,318, norma rn bullets 220grn and they do o.k but i mostly shoot 165---175 grns 32-40 plain base with the savage load data ,, very mild loads and a pleasure to shoot .
my go to powders are ,,unique 13grn.
2400 16.5 grns.
and trail boss fill case to shoulder, empty out and weigh and x it by .7 and you have a good starting point for the gew 88.
shoot all day with no bruisers,,,
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