Tumbling 8MM Max

[SharpsShooter]

I'd like the opinion of you guys on an item or two. Buckshot and I have been batting this one around and decided to throw it out for your intellectual analysis. I'm currently shooting the 8MM Max in my K98 and I'm having good and bad out of it. Loads of around 1160fps and a bit higher shoot pretty well, but if I try to go higher to say 1450 I get tumbling at 50yds. I am sizing to .324, but am forced to seat to a short OAL due to a very abrupt short throat. The boolits engrave lightly upon closing the bolt. I know I could get another size and lube die of .3225 and size the nose down to allow longer seating, but I'm not sure that is the problem. It seems that a longer bearing surface would produce better accuracy??

That said:

1. Is OAL causing some of my problems or

2. Do I need to crank up my MV to stabilize that long boolit.


My seating depth is 2 lube grooves and the gas check below the case neck. (eyeball measurement) (2.715" OAL actual ) There are differing opinions on that topic as some have better luck than others. I have always been a straight wall case shooter when it came to cast boolits, so it never entered the arena as a potential problem.

if it is a velocity issue and we need to dispense with the Unique loads, I do not have any surplus powder(s). However, I do have 2400, 4350, 4198, 4064. 4350 is a slow powder and looks promising for midrange to real thumper loads if the stability issue can be resolved. Of course no data exists for the 8mm with a 250gr boolit. I do have data for 225gr J-Boolits that I found recently and suspect the minimum loads could provide a starting point for work up.

Comments, suggestions welcome

[swheeler]

SharpsShooter; I have shot this boolit some and have had no problems with tumbling, although I haven't shot it as slow as you show. I seat to an overall length of 2.955" which puts the gas check and a lube grooves below the neck with no adverse problems that I see. The most accurate load I show in my notes was 55.0 grs Wc872(faster of lots of 872 I have) @1919fps-.871" 5@50, leave these loads set a day and the powder is so heavily compressed thast it pushes the boolits out of the cases far enough you can't close on them. Looking back tghru data I recorded velocities from 1490 to 2143 fps all flying nose first, actually a pretty easy boolit to find a load for. I settled on a hunting load with a 12 bhn boolit at 1882 fps, not the fastest or even the most accurate but a way to use some WC846 powder with cast. I haven't had time to try a lot of loads with this boolit, but 860,872,7383,H4350,N165,5010,846,5744,4831,748,489 5 all worked.
Pull out your Barnes Reloading Manual #one, page 101, 8X57 250 gr original, they have load data for RL15,AA2520,I4350,I4320,H414,H4895.

[Frank46]

SharpsShooter, in the current issue of the fouling shot one shooter did what might be the answer to your problem. Since you have to short seat due to the short throat what you could do is size your boolit down to bore diameter up to and including the first driving band. The rest of the boolit from the first driving band down would be sized to whatever diameter you'd require for your rifle. I believe he sized the nose and either first or second driving band so as to allow the boolit to be seated out further. Course you'd have to size the boolit twice, first the nose and whatever driving band you'd need to allow longer seating, then the second time to size the remaining body. Just a suggestion, Frank

[swheeler]

SS; I think I would give 20-22 gr 4198 a try, should get you close to 1600 and see if works better
Barnes#1 250 gr jacketed
IMR4350-43.0-46.0,2015-2247fps

[SharpsShooter]

SS; I think I would give 20-22 gr 4198 a try, should get you close to 1600 and see if works better
Barnes#1 250 gr jacketed
IMR4350-43.0-46.0,2015-2247fps


I appreciate the load data. I don't have a Barnes book and had planned to ask you for the information:mrgreen:

I'm going to take the advice of both responders and have Buckshot make a nose sizer so that I can get half of the boolit out of the case and also use the data you provided to get the velocity up into a decent energy range for hunting purposes.

Thanks guys. I'll report results as soon as i get the die and get some loads worked up.

:coffee: