Chronographed a string of ten rounds today with an average of 2232 fps, stAndard deviation was 18.41 ( whatever that means) which I was told was good. A little on the warm side today and barrel was hot. Groupings were $hit as far as I'm concerned, about 1.25 to 1.75 inches. New trigger is a beauty though, caught off guard for the first few rounds. Back to range mid week to bang a few more.
My first build, whatcha think! (RANGE REPORT POST 32)
- Thread starter Lt John McClane
- Start date
ultimate_monkey
CGN Ultra frequent flyer
- Location
- victoria BC
Standard deviation is the average difference in velocity , extreme spread is the slowest and the fastest
Thank, good to know. The extreme spread was 59.71. First time chrono rounds today so as green as they come. Lol
rnbra-shooter
CGN Ultra frequent flyer
- Location
- New Brunswick
Was this 39 grains of IMR 3031 and a Sierra 175? Or something else?
An SD of 18 is OK. That's about what Federal Gold Medal Match factory ammo will give.
Your m.v. of 2232fps is on the slow side. Chances are that you can safely work up your load. As you get hotter, there's a good chance you'll see your grouping improve, and your velocity consistency also improve.
By the way, it is usually the case that the Extreme Spread of a group will be roughly 3X the Standard Deviation of a group (multiply 18 by 3 and you'll see how it's pretty close to 59..!)
If you're shooting at 600 yards or closer, it's quite unlikely that ammo with an SD of 18fps will give you any accuracy degradation from your 100y group size. If you are shooting at 1000 yards, you'll notice some vertical spread in your groups. For 1000 yard ammo, it is worth trying to get your SDs into the low teens (and if you get it into the single digits that's incredible, but it's not always possible).
That was the hornady match 168 gr, 39 gr of IMR 3031. The grouping on this round is very good, it was just me today. I have worked up the load already and groups were opening up with the 168s. I do have a load with 175 gr sierra mk with the 3031 & 4064 which shoot just as well, if not better. I just stuck with the 168s as I have an easier time finding them/priced accordingly than the 175s.I think I'll load up some of those 175 loads and chrono those rounds to see how fast. Now when I say "I'll load" (I mean a friend/saviour does if for me) but just learning the way before I buy a kit. I wont be shooting past 100 for about another two months (CFB Petawawa), their range is 600 so its good to hear that you don't think the accuracy of the round will change at that distance. This is great info guys, keep it coming.
