Some 8x64s chrono info

sestoppelman

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Per the other thread about the Magnetospeed chrono, I got to try it today and it worked well for me, probably less fussing around than using a regular chronograph which I have had for many years. The Magneto did everything it claims to do, no complaints.

I have as some know an 8x64s Brenneke rifle, a rechambered 8x57 on a Mark X Mauser action with 24 inch bbl. Its a very good shooter and quite accurate.
My preferred bullet and powder combo thus far has been the 220 Sierra Game King boat tail with Hunter powder, which at first seems like it would be too slow but it proved today to be a good powerful powder, and is consistently accurate.

I also shot some loads with 200 gr Speer flat base over Norma URP and Winchester StaBall 6.5 powder. I grabbed a 5 pound bottle of URP a while back when Norma powder was about the only thing to be found. Its good stuff and I like it. I place its burn rate at close to but just under IMR4350, not a bad place to be. It has smaller kernels so can pack a bit better than the Lincoln Log powders.

With the 220 SGK over the Magneto today the top load with Hunter was 65 grs which gave 2730 fps for 3640 ft lbs of muzzle energy, ME. Not too bad.

Same bullet with 2 grs less of Norma URP gave the same velocity, and thus same ME.

Same bullet with IMR4350 surprised me a bit as 60 grs only produced 2590fps for 3277 ME, less than I thought it would do, and it being such a bulky powder I only have room for a couple more grains which at 45 fps per grain ( today ), would get me up over 2600 but probably not much more. Would still have me around 3300 ME. It is accurate however.

Hunter is ball powder as is the StaBall so easier to get more powder in.

Using 200 gr Speers, 64 grs of URP shows 2750 fps for 3360 ME, with the shorter bullet and more boiler room this could be upped a few grains I think.

Same bullet with 64 grs of the StaBall shows 2725, just a tad slower with the same charge so it appears that the StaBall is just a bit slower than the URP as expected.

None of the above loads showed any signs of approaching red line pressures per the usual symptoms which we all know, so am confident that in THIS rifle the loads are safe. The throat in my rifle looks typically European and I can seat bullets out a bit more than average but magazine length is a limiting factor., but I can load out to about 3.4" or so depending on the bullet.

Should you try these loads in another rifle and blow it up I never heard of you! LOL

Where possible I plan to up the charge on at least Hunter and probably URP as well to see what can be gained. About out of StaBall and IMR 4350 is just too bulky to be able to equal the Hunter without massive compression.

Fun times at the range!
 

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