I stumbled a cross a guy developing a load for long range competition and figured if you’ve never done this, you might want a peek into the process. I enjoy reading this stuff and am going to follow it.
Here is the first post to wet whistles,
CaptainSquishface edited 2 hours ago
So for those that aren’t following along with my current fiasco; I am planning on shooting 308 Winchester in an Extended Long Range Match because…why not? Actually it’s because I have the powder and bullets to do so…and it’s also so ridiculous that it will be fun. Every step of this idea is complete idiocy and I expect complete and total failure.
The crux of this horrible terrible plan is the new 200gr Sierra MatchKing #2231. This is Sierra’s attempt at a very good FTR bullet with a claimed G1 BC of .710. (Just for reference, the BC of the 6.5mm ELD-M is .587) The new Sierra bullet is so long that it requires a 9 twist to be fully stable out of a 308 Winchester…however with a 1:10 twist it still has a 1.37-ish sg…so it might actually make it to the target with the nose facing forward, albeit with a lower BC. When I ran the numbers through the Berger Calculator it would still be .690…which is still really good.
Why not use a different bullet? Well I could, except my second choice of bullet will not fit into the case without seriously encroaching on powder space. The new 200SMK is better suited to rifles like mine that do not have extra long throats for heavy bullets.
So what are we looking at in the picture? Well we are looking at a 100 yard ladder test (I know…oxymoronic.) I don’t use the ladder to test the best powder charge, but I wanted to see where my upper limits of powder were before I decide on a load. What I don’t want to do is settle on a charge that is safe in cold weather…and then I am hammering the bolt open as soon as it warms up 20 degrees.
SUPER DUPER SPECIAL LOAD DATA NEVER USE
So I started with 39 grains of H4895, and moved up in .5 grain increments for 10 shots. I already had in my mind that around 42 grains is where I would want to be, but I wanted to go above that to make sure I have a hot-weather margin of safety.
Rifle specs. 28 inch Bartlein barrel chambered in 308 for M118LR/FGMM. Surgeon action. 3.10 Overall Length
H4895 Powder. Lapua Large Primer Brass. CCI Large Rifle Primer.
39 grains = 2477fps
39.5 grains = 2487fps
40.0 grains = 2515fps
40.5 grains = 2566fps
41.0 grains = 2574fps
41.5 grains = 2617fps
42.0 grains = 2610fps
42.5 grains = 2643fps
43.0 grains = 2660fps
43.5 grains = 2701fps
I did not experience any stiff bolt lift on any of the loads. 43.5 grains was starting to show ejector marks. In hot weather or rain I would expect 43.5 to be unsafe.
There was a drop of 7fps from 41.5 to 42.0, which if internet superstition is to be believed, is where there is a velocity node. It could also be coincidence of the Chargemaster over-throwing and then under-throwing…as well as variation in primers. However, my main goal was to verify that 2600fps was possible, and I am very happy that I should have a good safety margin if weather heats up.
I also did a seating depth test, and I think I have a pretty good idea of where to load the ammo for overall length as well. The next step is to shoot it at distance, which will be this coming weekend. I am hoping that the bullets are stable through the transonic region but I am honestly expecting them to go sideways.