Developing a load for my new 6GT build. Proof 1:7.5 comp contour barrel, terminus Zeus action, MDT ACC, triggertech Diamond, TBAC Zeus. Have 30 rounds down it so far, posted the second two groups of 10. Berger 108 elite hunters and hornady brads. First group is 32.4gn varget and 40 thou off the lands. Second is 32.4gn varget and 60 thou off the lands. Group 1 I didn’t run the brass through my sizing die just took it straight to chamfer/deburr. Second I ran through my bushing die and expander button. Also used (I thought) better powder discipline, though I got a SD of ~13 on all 3 groups. I’m thinking from here I go back to 40 thou and try maybe bumping up 0.2gn powder. Or is it worth seeing what happens at an 80 thou jump? From what I’ve read with 6GT it’s best to go with big jumps during development. Any help is greatly appreciated!
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6GT load development
- Thread starter Kspence49
- Start date
Your barrel gonna speed up and undo everything anyway. Put some rounds on it till speed stabilizes then do load development.
I use varget and alpha brass. Berger 105s. Seems like you have some horizontal stringing in those groups? For sure in that last group. Shooting off bipod and bag?
The horizontal stringing is most likely you and not the load. Group dispersion should be circular with good fundamentals.
Load “development” is a myth.
6GT New Hart barrel, less than 50 rounds on barrel. 4x fired Hornady brass never annealed, never trimmed, Varget, 4 random loads, random jumps, with 4 different bullets @ 236 yards. Berger 105 hybrid is the best group followed by 109 hybrids.
Load “development” is a myth.
6GT New Hart barrel, less than 50 rounds on barrel. 4x fired Hornady brass never annealed, never trimmed, Varget, 4 random loads, random jumps, with 4 different bullets @ 236 yards. Berger 105 hybrid is the best group followed by 109 hybrids.
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I've never had to tweak a load found during development more than 1% when the barrel speeds up, or from going from virgin to once fired brass. Doing development now is a great way to find combinations to explore further down the road.
6GT is a pretty easy cartridge to get to shoot well...so bigger jumps might be faster in getting to the middle of your sweet spot. I like doing .010 - .015 increments, others have their own preferences. I still think that 1% charge weight increments are decent too...so .3 - .4gr for your cartridge.
6GT is a pretty easy cartridge to get to shoot well...so bigger jumps might be faster in getting to the middle of your sweet spot. I like doing .010 - .015 increments, others have their own preferences. I still think that 1% charge weight increments are decent too...so .3 - .4gr for your cartridge.
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Powder type can make a difference but .2 grains of the same powder won’t nor will increasing jump by .005. Horizontal stringing is caused by the shooter or the wind.
If a barrel won’t shoot with 40 rounds through it, it won’t shoot much better with 400 rounds through it.
Again, group dispersion will be circular omitting wind, shooter error and faulty equipment.
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Shit...just saw you were having horizontal stringing and not vertical. Disregard my last sentence, and I'm going to edit that out.
There are some combinations that work fantastic from the start. You might not be with the right bullet/powder combo yet. My 6GT hammers with 105 hybrids, 108 ELD is decent, and 107 SMK wants to kick the occasional shot out regardless of what I do.
Thanks for your help man. Might try speeding up the 40s and maybe throwing some 80s down it.
What’s your muzzle velocity, I’m running an impact with a 26” hawk hill barrel same twist as you and have great groups with 34 gr of varget, so I’m sure you can speed yours up a bit. That’s with 108 Berger vld’s.
You might try moving this thread to the load depot forum..
I'm following along, I have the same barrel on order but will be shooting 112 match burners over H4350
I'm following along, I have the same barrel on order but will be shooting 112 match burners over H4350
With the same barrel on an Impact action I went with Berger 108’s and 34.3 of Varget which gave me an ES of 9fps and SD of 3fps with an average of 3015fps on once fired Alpha brass approximately .040” off of jam. For my abilities and novice reloading knowledge I was pretty happy with the results.
