6GT load development

[Kspence49]

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!

 

[LRDD]

Your barrel gonna speed up and undo everything anyway. Put some rounds on it till speed stabilizes then do load development.

 

[Kspence49]

10-4, I’ve had some people tell me the barrel speeding up won’t affect the load but I’ve also heard the opposite lol. I’ll go back to 40 thou, stop grouping and put 100 rounds through it. Another thing I could try is to put H4350 behind it

 

[Csafisher]

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?

 

[Kspence49]

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?

Def horizontal stringing that’s why I was thinking back off to 40 again or take it further up to 80. Doesn’t seem like it’s happy at 60. Bipod and bag yes

 

[Hickswr]

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.

 

[diggler1833]

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.

 

[Kspence49]

The horizontal stringing is most likely you and not the load. Group dispersion should be circular with good fundamentals.

Load “development” is a myth.

I’ve read that, but that’s a pretty dramatic change from one group to the other.

So every powder and ever seating depth works for every rifle?

 

[Kspence49]

I've never had to tweak a load found during development more than 1% when the barrel speeds up, or from going front 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.

Cheap rear bags are a great way to get vertical stringing too.

Thanks man. Maybe I’ll try 80 thou also. If that doesn’t run I’ll drop back to the 40 and mess with powders and fundamentals

 

[Hickswr]

I’ve read that, but that’s a pretty dramatic change from one group to the other.

So every powder and ever seating depth works for every rifle?

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.

 

[diggler1833]

Thanks man. Maybe I’ll try 80 thou also. If that doesn’t run I’ll drop back to the 40 and mess with powders and fundamentals

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.

 

[Kspence49]

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.

 

[Landon4]

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.

 

[762 ULTRAMAGA]

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

 

[lockroller]

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.

 

[drifter308]

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.

I use 34 grains of Varget .20 off the lands with 105's.