medium 7mm. range day!

[africa]

Been shooting a 7x57 , using a load of 160 gr. Lyman 287641 + 36 gr. of IMR 4064 , estimated muzzle vel around 2200 fps. Good gun rest, reliable 4X scope, tight screws, clean barrel, no undue barrel heating. Six 3 shot groups at 100 yds.
measured .1.5", 3.6", .9", 3.6", 2.2", 3.0", .86".
All nice triangles. Why the variation? Should I try the 'up half-a-grain, down half-a-grain' thing? Any input will be apreciated.

[Bass Ackward]

measured .1.5", 3.6", .9", 3.6", 2.2", 3.0", .86".
All nice triangles. Why the variation? Should I try the 'up half-a-grain, down half-a-grain' thing? Any input will be apreciated.


Africa,

My guess would be erattic ignition assuming you had good quality bullets. When I go to slower powders, I usually just seat into the lands so that I can just see rifling marks. Not enough to be any danger of pulling the bullets if I extract the round. Just enough to retard forward motion from the primer until the powder pressure comes up enough to get things started.

In truth, their could be several reasons though. And the up / down thing is a necessary part along with different powders, different diameters, lubes, quantity of lube, hardnesses, primers just to name a few. Should be about 40,000 possible combinations. How many do you think you have covered so far? :grin:

[Buckshot]

..................Naturally do one at a time. FIrst check is to make sure the casenecks have a good grip on the slug. And since you have 4064 ready to go, reload the previous test but put a roll crimp on the slugs. Reshoot. If no better, I'd suggest a faster powder, keeping the crimp. If no better, or only slightly better I'd try a different primer.

Like BA said, there's only eleventy bazillion different combinations out there 8)

.................Buckshot

[mooman76]

Were your cases of different manufacture or military and all trimmed to same length? Military brass can have higher pressures. Did you clean youir gun between groups? Just a couple things to think about. Maybe try 5 shot groups next time!