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I just started working up a load for my new barrel. Its a 1:10 twist McGowen 22" varmint. Been trying 168 matchkings and the 168 harnady match with varget and BL-C2 with CCI large rifle primers. anybody have suggestions? My powder weights, and C.O.A.L. is VARY uniform. Only using for target so how far should i be from the lands?
Wood
SMKs normally like to be off the lands so I'd try loads set about .010" OTL. I don't have experience with the Hornady's so don't know if the like to be jammed or jumped. You didn't mention what kind of accuracy you've been getting, brass used and whether it's fully prepped and weighed so it hard to judge what course of action to take. Are you chronographing loads? I would try the CCI BR-2 primer instead of 200s, they may help tighten up groups. Varget is a good powder that normally works well in the 308.
The design behind the 168 has been a point of debate for a long time. Some say it's a dynamically unstable design, some say it was a different 168 that was dynamically unstable, and some say the 168 was never unstable. I don't know either way but since you are shooting a 10 twist barrel I would try some heavier bullets. I know the Berger 185 VLD's shoot very well in a 1in10 twist. IMO Berger's like to jam the lands. I'm still up in air on the SMK's I've seen them shoot good jammed and jumping; I've seen them shoot bad jammed and jumping. So I don't know exactly how I feel about the SMK's just yet. I've been blessed with a lot of good groups using Berger's, so Berger is my main bullet. Brian Brown.
I load the 175 SMK's and in MY gun, my best groups are at .01" off. When I loaded the Horn-head bullets you talk about, I found that 0.03125" was the ticket.
The 168SMKs have (still) a problem with transonic stability. Not an issue until downrange. They start to tumble coming back through the sound barrier regardless of barrel rate of twist.
My 1:10 shoots 155 Nosler CC, 168 SMK and 175 SMK all quite well. The 155s were my reloads with Varget with several of the developmental groups having all 5 holes touching at 100yds. The 168s were a combination of my reloads and SSA factory loads. A 10 shot group (the only group I shot) of the SSA was sub MOA. When zeroing the 175s @ 200 yds, the first 3 were a nice cloverleaf (such that we really couldn't tell where the 2nd and 3rd rounds went and had to assume until we went downrange) and the next two (after scope adjustments) were also pretty well stacked on top of each other.
Read up on the OCW load development method. Find the range of charges that exhibit min/no POI drift and then play with seating depth from there to tighten the groups.
And unless you have a whole lot of the BL-(c)2, try a different powder. Varget and 8208XBR are good choices.
44-45 grs of Varget or rl15 seem to be the area where most find a load. I like to jump the bullet. I have a harder time seating out to the lands. 2.8" If you cant find a load with these 2 powders and seated at 2.8" then you have other problems.