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Today, 7/8/15 The temp was 70 degrees. I fired three groups at 100 yards with the 6.5SLR. The bullet was the Nosler ABLR 129 about .020" from the lands. I used 68.0 grains of IMR7828. The velocity averaged 3,376 feet per second.

It does surprise me (why I'm surprised I don't know) the difference a primer can make. Was there much of a velocity difference?

Wow! that's a pretty convincing argument for comparing primers after you've found your best load. Which primer did you use for load development?

prm,

I didn't get to check the velocity today. I used yesterday's numbers for the CCI250 Magnum.

JeffG,

The Federal 215 Magnum is the one I normally use to start with. They averaged 3,389 feet per second.

When I worked up a load for the .223 the difference was this dramatic. The best primer was CCI BR-4 with half dozen five shot groups averaged .464" with the worst measuring .494"! The Federal small rifle primer averaged 1 1/2"! I stopped trying them after the third group.

Ringman,

What's your order of eliminating variables?

What I mean is, if You pick a bullet first, then a likely powder, then do variations of powder volume, then do seating depth, then do primer trials...and you're still getting two inch groups, what do you change first? (I know most people's answer would be, 'the rifle')

I usually change to a different powder, then another, doing a range of charge weight tests for each. When I've decided I have the best combo of powder choice and charge weight, then I go to bullet seating depth. It's usually after all these variables are tweaked that I go to primer variations.

How about You? Which do you change first, next, etc?

It's not really surprising that a mag primer would give more consistent results with a slow powder in an overbore case.

It is interesting that the spread would be that significant at 100 yards though.

JeffG,

First I love velocity so I work toward that first. Last year this rifle was a .25 caliber. I wanted a sleeker bullet so I had it rebarreled and chambered with this case that matches a .264 Win Mag. I knew I wanted to use GSCustom 106 HV bullets. I figured I could get 3,750 feet per second. I looked in several manuals and came up with H4831 giving the highest velocity with 100 grain bullets. That established the powder. Normally I start with Federal 215 Magnum primers so that's what I started with. In the past I get the highest velocities and the best groups with GSCustoms. Not this time. The average for twenty-six shots was an acceptable 3,693 feet per second. Certainly good enough. Groups were terrible.

I switched to the ABLR 129's and used the same powder and primers and established a load that would work through the action like a factory load. (I wanted 3,400 feet per second.) H4831 maxed out about 3,300 fps, so I switched to IMR7828. Again I ran a few shots through the action till I found what I accepted as the max that would go through the action like a factory load: 3,376 fps. Then I loaded up a few cases with only the primer being the variable. All the groups up until today were about 1 1/2" - 1 3/4" or worse. Normally I do this two days in a row. I figured I would take the one that grouped the best and start adjusting the length. The CCI250 worked yesterday and today.

I guess adjusting the length was not necessary. The 129'a are only about .020" from the lands.

So You had tried this same load with the fed 215M? and still cut your group size this much by going with CCI250.

I'm loading for a wildcat now, and I'm in the same boat 1.5 MOA groups and bigger, no matter what. I switched bullets...same. I switched powders, same and worse. This weekend I'm finally trying different primers. I've been frustrated because this has been the most work I've ever had to put into load development. I'm all in on this one, it's a custom Lilja barrel, so I won't be content until it's consistently sub-MOA.

JeffG,

I sure wish you success your next time out. After firing over 300 GSCustoms, I gave up on that bullet. Since there are still over sixty I may revisit them later.

If you don't have lots of different primers, give me a private message I will give you a few different brands to try.