We finally got a break from our frigid weather. Decided to do some bracket testing of a new load for .22-250. Had a balmy 42F (5.5C) today. Still wearing heavy coat and flannel lined jeans, and had to trudge through the still standing snow, but it was very tolerable. In fact, Very enjoyable day, even though just a short lunch break.
The setup - Sako model 85 .22-250 caliber rifle. 100 yards. Science experiment testing different handloads for velocity and accuracy. Also some factory for comparison. One "cold-bore" round was fired before testing, then small break in-between each 5 shot string to give barrel a chance to cool a bit. Shooting was off of a bench with bipod, no sandbags. Day was sporadic winds very gusty at times ~10-20mph, and yes still a bit cold.
I tested against 4 different handloads based on load data from Nosler. Same bullet shape and weight (55 grain Varmageddon), and just different amounts of gunpowder to see which the rifle liked best. A set of 5 round groups for each load was tested. **The factory loads I had to shoot 9 rounds to get a 5 shot string to register on the chrono.
The chrono used was a LabRadar Doppler system. I just love this setup. It's easy and quick to setup, Nothing hangs on the weapon to detract from accuracy, no screens to setup or try to shoot through. I also really like the instant printout on the screen and the ability to then download the entire sets with even more detail like fpe energy etc at different ranges. This also provides the velocity measured at multiple intervals, ie: muzzle, 25 yards, 50 yards, 75 yards, 100 yards, etc. Normal screen based or magneto based chronos can't do that. The one limiting factor I've found is that the LabRadar's maximum limit is 3900 fps. Given that the Hornady Superformance Factory ammo is rated at 4,000 fps, it took me 9 shots to get a 5 shot string to measure. I had similar challenges before. Not a big deal for me, as I plan to stick with my handloads which are still a couple hundred fps below that.
For the other science/shooting geeks out there, here's the specs:
For the not so technical, what we typically want to see is the least Extreme Spread and the lowest Standard Deviation. This means our loads are consistent, and should then shoot the same as others (mostly).
I think the Factory Superformance loads are giving a false sense of consistency in this report, due to some of the rounds I believe exceeding the 3,900 fps limit which would throw the numbers much further off. I actually had to shoot 9 rounds to get a 5 shot string to measure. I verified this previously with using a magnetospeed chrono on some. Regardless They certainly did not shoot as well through my weapon, not horrible, but I like tighter.
For those less technical, here's the pictures. Load 1 was 32 grains, Avg. 3,160fps.
Load 2 was 33 grains, Avg. 3,277.86 fps.
Load 3 was 34 grains, Avg. 3,411.91 fps. (This also shows the factory Hornady group at the bottom left).
Load 4 was 34.5 grains, Avg. 3,419.42 fps
and here is the nice collage.
So, which one will I go with? After detailed review of each 5-shot string, I chose Load 3. Even though the numbers weren't quite as good as number 4, it had one shot that was 30 fps lower than the other 4, which were all within 6-7fps of each other. Maybe one or two of the little grains bounced out during loading, or some other factor threw it off, but given the group size and consistency of the load other than that, I'll stick with it. (It also happened to be the most accurate load in the powder vendor's testing with different style barrel and length).
There ya have it. A day of fun science.
Now to prep for the big snowstorm coming tomorrow, 14 inches or more headed our way!
