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Old December 2, 2019, 12:19 AM   #1
smleno1mkIII
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Not getting the velocity I should? 8mm mauser

Loading for 8mm trying to duplicate the German S round, using pulled Turkish 154 gr bullets loaded 50 grains of Imr4895, I’m getting 2780fps over the crony which would be correct according to my load book out of a 23.6in 98k barrel,problem is I’m using my m38 Turk with a 29.1 inch barrel so that extra 5.5 inches of barrel nets no gain what gives my load book lists 50.4 gr max load should get 2800 FPS out of a 23.6 in barrel with a 150 gr Hornady Sp help me out what am I not getting.
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Old December 2, 2019, 12:53 AM   #2
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It's not all that unusual for an actual production gun to get less velocity than what is published for test loads. Test loads are fired in special guns with minimum chamber tolerances and only after carefully getting the powder in the case to fall back over the primer, and those factors maximize pressure and velocity. I would say a 50 fps difference from the published number is pretty normal, and occasionally you see over 100 fps difference. I would expect your 5.5 inches to add around 80 fps, so if the chamber is loose enough to be low by that amount in a shorter barrel, then that's all that is going on. Luck of the draw in production tolerances or wear.
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Old December 2, 2019, 01:35 AM   #3
smleno1mkIII
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Yeah 80fps was about what I was expecting since 75-100 was what I was getting with other loads I’ve tested, I was expecting to get like 2850-80 as 2880 is my goal as the German S round is 2880fps out of a 29.1 Gewehr 98 barrel ,I tested some fed arm what turned out to be Russian reloaded German SME 177.5 gr bullets loaded for 2526 FPS out of a k98 what they said on the box my m38 Turk clocked 2625 FPS so that’s why I was a little flustered ,any suggestions like trying a slower powder like Reloader 15 or IMR 4320?
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Old December 2, 2019, 10:05 AM   #4
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Hodgdon's 8×57 data shows CFE223 powder producing the most velocity. About 200 fps more with a 150-grain bullet, so that's where I would go next.
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Old December 2, 2019, 11:32 AM   #5
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50 grains of IMR4895 is .5 over current Max of 49.5 for a 150 grain bullet in an 8 x 57. Max velocity out of a 24" test barrel was 2847 FPS. So something isn't right, possibly with the chronograph.
In any case, the 'S' load ran at 43,511 PSI. Look for a load that gives around that. It'll be somewhere in Mid range. It will not be with 50 grains of IMR4895. Hodgdon used CUP for their 8mm Mauser test too. There is no mathematically converting CUP to PSI.
Manuals give averages of all the loads tested, using the exact components, environment and firearm, on the day of the tests.
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Old December 2, 2019, 12:07 PM   #6
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The OP is using a 154-grain FMJ military surplus bullet, Hodgdon data used a 150-grain Hornady softpoint. There is bound to be a difference in velocity. Hodgdon used a different lot of powder than the OP used, another reason for a different velocity. The OP’s rifle is a well-used military arm, Hodgdon used a pressure barrel built to SAAMI minimum dimensions. Hodgdon tested at standard temperature, at what temp did the OP test? The big surprise here would be if the two velocities actually were the same.....


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Old December 2, 2019, 12:38 PM   #7
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Simple solution to the problem. Get rid of the chronograph and claim your getting what ever you want. Any animal you shoot is not going to know the difference. Imagine an 1800's mountain man worrying about the ballistics's of his Hawken as much as modern man worries about his modern cartridge!
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Old December 2, 2019, 01:48 PM   #8
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How does it group? That is what counts.
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Old December 2, 2019, 08:46 PM   #9
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1 inch at 50 2 1/2 in at 100 yards
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Old December 2, 2019, 09:14 PM   #10
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Mine is the 23" barrel and I am right were you are, but mine will group 1.1/2 at 100yrs with a bout anything you put in it !!!
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Old December 2, 2019, 11:00 PM   #11
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Ironically it shoots cast really well like one ragged hole at 50 same with Romanian surplus the weak stuff that only does 2650-75 FPS in my gun I’ve heard that stuff barely breaks 2500 in a k98 and it smells weird,it also did really well with my surplus Turk bullets and 47.5 gr of imr4895 at 2650 FPS it likes that velocity for some reason when I try to push velocity higher than about 2700 accuracy suffers it also shoots those SME rounds well the real annoying thing is with all those loads from 50 yards and under it prints dead center just ever so slightly to the right with the sight in the 100meter setting but I have to set it to3 or 400meter setting to hit center at 100yards or it hits 4 or 4.5 inches low and for some reason that drives me bat crap nuts why can’t I just be happy and accept that my Rifle won’t shoot top tier loads well sigh.
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Old December 3, 2019, 07:03 AM   #12
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I had a Vz24 that had a badly pitted barrel.
It would shoot slow.
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Old December 3, 2019, 03:12 PM   #13
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Quote:
help me out what am I not getting
what you're not getting is that some rifles shoot slower than others. Usually the difference is small, but sometimes, its not. It's rare for the difference to be large but it does sometimes happen.

had a friend who was in love with his .257 Wby, until he got a chronograph and found out he had a "slow" rifle, and his .270 WIn with 4" less barrel was actually doing 20-30fps faster then the Wby with the same bullet.

It's rare, but it happens.

You need to compare your load velocity through other (at least one, 2 -3 is even better) 29" 8mms and see what they get. If they are all close to each other and different from yours, the problem is your barrel is just "slow"

Also possible the stated specs came from a test rifle that just happened to have a "fast" barrel. Many things are possible.
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Old December 3, 2019, 05:04 PM   #14
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In addition PV test barrels are "tight" with chamber and barrel not more than .0005" over minimum spec.
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Old December 3, 2019, 05:45 PM   #15
reynolds357
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Quote:
Originally Posted by smleno1mkIII View Post
Loading for 8mm trying to duplicate the German S round, using pulled Turkish 154 gr bullets loaded 50 grains of Imr4895, I’m getting 2780fps over the crony which would be correct according to my load book out of a 23.6in 98k barrel,problem is I’m using my m38 Turk with a 29.1 inch barrel so that extra 5.5 inches of barrel nets no gain what gives my load book lists 50.4 gr max load should get 2800 FPS out of a 23.6 in barrel with a 150 gr Hornady Sp help me out what am I not getting.
The barrel dia is not terribly consistent in those rifles. Get one a touch oversize and velocity goes way down.
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