What 2 years of load development taught me about my precision rifle

[Cosmos]

That rifle has a preference. It shoots one load consistently well and everything else adequately. Finding that load took 40 different test groups over two years. The process was most of the fun but the result was a sub-half-MOA load I developed myself and that is something I'm genuinely proud of.

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[Mike6158]

When I started looking for a good load for my 6.5PRC I started with N560 because that's what a lot of online sources said to use. I did 5 tests, 5 shot groups. I built the rifle on an Aero Solus Short Action magnum action and a prefit barrel. I got acceptable (non-competition)100 yard groups with N560, .75" to one .296" 3 shot group. But ES/SD weren't quite what I wanted there were no nodes.

An F-Class shooter suggested that I switch to N555 because (A) N560 is hard on barrels because it runs hot and (B) N555 is the easy button for 6.5PRC. He was right. Test 1 was with Fed 215M primers, prior testing was with Fed210M primers. I tested 555 with Fed110M's but the results were much less consistent. Here's test 1 (3 shot groups). All pertinent data is in the sheet. First thing to notice is the very wide powder node. 100 yard group size deviations are all on the shooter at this point.

The next thing I did was 2 tuner tests. Still 3 shot groups. Test 2 was the only one I recorded group size. Not sure why. Pay attention to the average velocity.

The downside to this kind of consistency is that barring bad conditions, a bad group is likely to be the shooter.

Next step (3) is stretch it out a little. Group size is in inches. Divide it by 3.141 for MOA. This is a 300 yard test to ensure that the load really is a good load (I shot it later at 1,000 yards and had a 4" group on a 10" plate)

I haven't done Step 4 yet. I'll shoot 10 rounds at 300 to see how the numbers hold up, how well it groups, and how consistent I am.

BTW - I don't compete. I just like to shoot. I made the spreadsheet these screenshots came from. Each rifle I shoot has a spreadsheet. Each sheet has a tab for each test. Some rifles have a sheet for each bullet that I test, like my 6.8 SPCII. AR and bolt guns. 105, 120, and 175gr MKZ's from Cavity back. The rifles I consider to be precision generally run the same bullet (Berger's)

 

[Matt Childers]

Mike. That is damn good work and very thorough work. Very impressive. Would you be willing to share that spreadsheet with an old man?
Thanks, Matt. I can’t wait till you do round 4

 

[Mike6158]

Mike. That is damn good work and very thorough work. Very impressive. Would you be willing to share that spreadsheet with an old man?
Thanks, Matt. I can’t wait till you do round 4

One old man (almost 68) to another - It's been tuned up over the last couple of years and I'm more than happy to share the spreadsheet. It's in numbers (mac program) but I think I can convert it to Excel. Whichever version you prefer. If it's allowed I'll just attached it to a post.

 

[Matt Childers]

Sent you a DM Mike.

 

[Mike6158]

Ok, I think they sent. It looks like I can attach. Once you verify they made it I'll attach them to a dedicated post.

 

[Matt Childers]

Thanks sir

 

[Matt Childers]

In case you didn't get the DM. They work fine and appreciate them.

 

[BrotherHubb]

I’m like you, I don’t compete but like to shoot. I have a 6.5x55AI, Pierce single shot and Obermeyer 28” 1-8 Palma contour with a Jewel Benchrest trigger in a custom F-Class type stock. I’m thinking of buying a Sightron S6 10-60 and put that on it.

 

[Mike6158]

In case you didn't get the DM. They work fine and appreciate them.

I sort of got it I didn't have much time to read it. The lead up to the weekend was pretty hectic. I had to get loads worked up for my bosses 300 Win Mag. I offered so I can't complain about it. I can however complain about the rifle. It's a Tikka with a skinny little fluted barrel with a the smallest muzzle brake I've ever seen on the end of it. It has a variable power scope, 10x max. It's using the old Weaver mount, not Picatinny. I shot the first tests with it yesterday, H1000 and 4831SC. H1000 was a much better choice. Brand new, never been shot, it made 3/4" groups at 100, and that's with me holding in the center of a 3" dot that looked like a 1" dot with that scope. I texted him that he needs to give his kids back the scope for their BB gun and buy a real scope It shot good, heated up fast but cooled down fast. I ended up putting most of the test on steel at 300 yards. I was just looking for (and found) a wide velocity node that I'll explore in the future. I also shot my two 6.8SPC II's. One 16" barrel and one 24" barrel. Both 1:7. I used the same load for both. Both seated .050 off but not the same COAL Both new rifles. The longer barrel was about 15fps per inch of barrel difference faster with H322.