300 win mag new reload
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Scrubbit
Well-Known Member
Hi Jeff. I'm using CCI250 primers in my 300 WM loads and get 2 or 3 out of every 10 shots with up to 100 fps divergence while the rest are within 20 to 30 fps. I am very finicky with my brass prep, weighing of charges etc so am starting to think that it's the primers. Have you (or anyone else) had similar experiences?
Scrubbit
Well-Known Member
Another thought, I'm using Win brass, and have noticed that they have very deep primer pockets with some sort of a ridge that I have to overcome with my hand primer to fully seat them. Almost a 2 stage thing. Is it worth changing to Lapua brass?
Broz
Well-Known Member
Lapua 300 win brass was discontinued years ago. So will be hard to find. I would stick with WW (same case volume as Lapua) and seat the primers to the bottom of the pocket.
As for the velocity swings. I will call BS on the Chronograph. The only two I trust are the Oehler 35 and the Magneto Speed.
Shoot a few to 800 and measure your group vertical. The proof is in the pudding.
Jeff
Scrubbit
Well-Known Member
Answered my own question... Switching to Norma brass. Still curious about the primers.
RTK
Well-Known Member
I must be looking in all the wrong places because I can't seem to find any 300wm brass anywhere.
Scrubbit
Well-Known Member
Thanks Jeff. Have taken 3 chronys and tested them back to back, and they are all different. Frustrating. Already bought a new one and gave the old one to my brother... Should have gotten the good one to start with.
Scrubbit
Well-Known Member
Does the Magneto Speed work with Muzzle brakes like I have on my XCR? A pic is on page 4 of "Moose Down 778m". Really appreciate the input you and others have contributed.
Broz
Well-Known Member
Yes, I use similar brakes and shoot way more braked rifles than not. It has worked very well for me.
Jeff
Scrubbit
Well-Known Member
Thanks Jeff. Ordered. Now I just have to find Retumbo and 215s. Like hens teeth to find in Canada.
Scrubbit
Well-Known Member
Found Retumbo at Cabelas Canada (thanks for the tip ATRS). They had 19 lbs. Now they have 12... Prob the only Retumbo left available in Can unless Higginson powder gets some in on their next order.
Curious...
At what point in your load development are you testing primers? Powder charge first, primers second, seating depth last???
For those looking for 300 Win Mag brass, check the once fired brass market until they are more available.
At what point in your load development are you testing primers? Powder charge first, primers second, seating depth last???
For those looking for 300 Win Mag brass, check the once fired brass market until they are more available.
Scrubbit
Well-Known Member
I've been doing some thinking. Use CCI large rifle primers in my 308 with Lapua brass and have very little velocity variance (avg 10-15 fps). Checked with Alberta Tactical Rifle Supply in Calgary (they do all my gunsmithing and are very experienced shooters) and they said that there is quite a variance in case capacity in Win brass that can cause a significant velocity shift. This correlates with my experience in that when I prepped the Win brass I found a very significant deviation in thickness and length. Add to that my negative experience with the primer pocket wall variation on the Win brass and I think that's the most likely cause of my muzzle velocity fluctuations. The switch to Retumbo and 215 hybrids is to get more velocity and improve the terminal performance in animals at long range. My seating depth is dead easy. Put the bullet in an empty case with a relatively loose neck and chamber it in the rifle so the lands push the bullet into the case. Measure the COAL and then subtract 5 to 10 thou. I know lots of people have had trouble with seating depth, but this has worked for me. Crude but effective. After that it's step testing. Never really messed with primers, but will try the federal ones when I get some in.
