Let's be honest, the 300aac/"blackout" is not really a sub-moa cartridge. You can scour the interwebs and find anectdotes about "my sub-moa 300blk group" but mostly people are squeezing out around 1.5 moa, at closeish distances. Really, they are designed for a heavy subsonic FMJ, out of an AR style platform. Not exactly the most valuable traits down-under...
Nevertheless, shooting only light supers, I like the blackout for two main reasons, 1] they are cheap to run (~18grs of slow pistol powder under any budget 125gr 308 pill) 2] I can reanimate my dead 223 comp brass to 300blk. There are other reasons also, but are moot points compared against other calibers.
I have a Ruger American Ranch rifle in 300blk which I've shot quite a bit. There are whole threads on here dedicated to that gun. Long and short of it; whilst it's great for what it is, I found that while it was almost sub-moa at 50m, it was not sub-moa at 100m and beyond. Furthermore it was not consistent under match-like conditions, and tended to drift when hot, which is becomes bleedingly obvious at moderate ranges. I had the hankering to get it to shoot better.
My theory of the shortcomings of the factory 300 blackout are as follows:
a) The tight 1:7" twist barrel was over-stabilising the light 125gr supersonics, meaning any "wobble" was exaggerated once the pill moved beyond 50m.
b) The long throat designed to handle up to a 220gr monster meant the 125gr pill was jumping well over 100thou to engage with the lands.
c) Tight neck tension seemed paramount in achieving consistency; an undersized collet-die mandrel and crimp was required for peak accuracy. Perhaps this is because of the long jump, i.e. point b).
Given those observations, I decided to reconfigure my blackout to suite specifically a 125gr supersonic load. Looking at the specs for the AK-47; it sports a 1:9.45" twist with 16" barrel shooting roughly a 122gr pill. I thought the Ruskies were probably on to something.
So I ordered a custom barrel from Lothar-Walther to match the existing contour, only with a slower 1:10" twist, and a custom short-throat reamer from Pacific Tool & Gauge to match the 125gr pill.
10 months later (thanks COVID), the project is now complete:
- Retrofitted, 1:10" twist 30 cal barrel. Short throated for 2.1" COAL.
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I took it out on Saturday and I shot crimpless FLS handloads on the 100m mound, off the bags, with an INSANE 30-40km/h fishtailing tail-wind (the hardest kind of windage) and here's the result:
- Typical 100m group, shot quickly to combat 30-40km/h fishtailing tail-wind
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Now that my friends, is a true sub-moa 300 blackout. This little girl will be accompanying me more often to the Telescopic matches, and is my go-to hunting rifle (at 3.7kg fully kitted including sling).
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