6GT & H4350

Discussion in '6mm, 6.5mm, and .25 Cal (Not 6BR)' started by MikeMcCasland, Apr 23, 2020.

  1. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Gents,

    I'm tossing around the idea of spinning up a 'fun' barrel for a Panda action, and I don't currently have any 6mms in the arsenal. I'll probably just use this barrel for informal paper punching, and may run it in a 300/600 yard F-Class match if I'm feeling froggy.

    I've been researching all the various 6mms, and the 6GT has caught my eye. I know that caliber has more adoption on other forums, but I generally don't trust the reloading info posted there, so here we are.

    My smith already has a 'standard' JGS 6GT reamer on hand, and I was wondering for those of you playing with the GT, does it have enough case capacity to run 105s-115s using H4350 (into decent velocity node) without compressing the heck out of powder charges?

    I've got a LOT of H4350 on hand, and only one other rifle that uses it, so the 6GT is appealing if I can get it to work. The 6CM is the other obvious choice, but I like the idea of a lower capacity/more efficient case that the GT offers.

    Thanks in advance!
    Mike
     
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  2. ShootDots

    ShootDots Gold $$ Contributor

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    Mike, I would talk to Tim Vaught. He has a 6mmGT he uses for PRS. His shoots awesome! I believe he is shooting the "new(er)" VV N550. H4650 is just a tad bit slower. Tim should give you some good advice..
     
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  3. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Good to know! I'll ask him next time I see him.
     
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  4. Ponderosa Arms

    Ponderosa Arms Silver $$ Contributor

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    I think this cartridge was developed to use Varget s the go to powder.
     
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  5. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Welp, I've received some PMs about this and it sounds like H4350 will work. I went ahead and ordered a 31" 1.250" .237 1:7.5T blank, and a Whidden FL bushing die set for the 6GT.

    I've got two identically built FTR rifles Panda/XITs now, and the intent is to use this as a play barrel for now. I'll probably build a PRS/hunting rig off the 6GT assuming I don't hate something about it. Planning to finish out at 30", and with bipod should put me under 22lbs if I ever wanted to shoot it in F-Open.

    Like I said, I've got a LOT of H4350 saved up, and given I'm not planning to shoot any H4350-centric cartridges in competition anytime soon, it's effectively a lifetime supply, so I'll be starting with that. If H4350 doesn't work, I've got some Varget and Shooters World Precision I can mess around with; I'm just trying to save that for actual FTR competition.

    I'll post up some load data once I get it built up. Should be next weekish.
     
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  6. xswanted

    xswanted Gold $$ Contributor

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    I use H4350 in my dasher and a 22br wth great results. Also in a 6x47 so I don't see any reason it wouldn't work in there.
     
  7. RonS

    RonS

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    I tried H4350 in my 6x47L, 22 BR and 6 GT with unsuccessful results. When I tried RL-16 it all came together. With all cases 90-95% filled I see no signs of pressure. My accuracy on average is approximately .25MOA and velocity is faster then H4350. I hope this helps...
     
  8. ToddKS

    ToddKS Gold $$ Contributor

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    H4350 will work with the 6GT.
     
  9. SEMO Shooter

    SEMO Shooter

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    I have used Varget and H4350 with 105 Bergers. My rifle has a Bartlein 7 twist 5R at 26". It is setup for steel matches.

    33.0 to 34.5 of Varget gave me good results. 33.0 produced 2900 MV and 34.5 produced 3000 MV. My Varget loads shoot tighter groups than the H4350. I think H4350 can do better with more testing.

    My first test with H4350 was with 34.0 gr and it was slow at 2650 MV. My second test was 37.5 to 38.1 with MV of 2920 to 2970.
     
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  10. Hoodoo

    Hoodoo Site $$ Sponsor

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    Did you ever try H4350 in your GT?
     
  11. ShootDots

    ShootDots Gold $$ Contributor

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    I do not have a 6GT.. My friend Tim Vaught has one. Exactly all the powders he has tried, I would not know... Sorry..
     
  12. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    I tried H4350 in mine (30" 7.5 Bartlein). All in Alpha brass, behind a 107 SMK, with a GM205M:

    37.3 - 2964 FPS
    37.5 - 2995 FPS
    37.7 - 3004 FPS
    37.9 - 3010 FPS
    38.1 - 3035 FPS

    I settled on 37.8 as my powder charge node for the 107s.

    I've also run that charge weight with a 105 Hybrid, and Got ~3025 FPS.

    Anyone tried N140 or N150 in this cartridge?
     
    Last edited: May 21, 2020
  13. kyreloader

    kyreloader Gold $$ Contributor

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    Were you not happy with the results with H4350?

    N140 should be very similar to Varget in this caliber, so around 34.5g is where a lot of shooters find a sweet spot with Varget. Start at 33 and work up to 35g?
     
  14. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    I tried H4350 with the 107 and 105 Hybrid. I also did depth testing with both, and the groups weren't bad, but they weren't what I would call stellar.

    So far out of the 100 rounds I've put through the gun, all groups combined are averaging .49 MOA at 215 yards. Again, not terrible, but I went into this with fairly high expectations.

    That said, I've only tried Shooters World Precision and H4350. I know the GT was created for Varget, so I'll be trying it next along with N140.

    I did find a guy out of South Africa on the 6GT facebook page that claims to be using it. He said he was getting 2950 with 32.9gr of N140 and a 105 Hybrid. I'll probably start there and work up in .2 gr increments.
     
    Last edited: May 20, 2020
  15. Hoodoo

    Hoodoo Site $$ Sponsor

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    I'm going to try N140. I have a good friend that swears by it in his 6.5x47, no reason it shouldn't work in this. I want to stay away from Varget, I don't want to have to rely on a powder that literally everyone has to have right now. I'll try N140 and H4895 in my GT. Should have it chambered tomorrow, I'll start breaking in my barrel this weekend. Plan on starting around 32.5 grains of N140 and working up in ,1 grain increments until I hit pressure while I break in the barrel. I'll report my findings.
     
  16. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Nice! If it's any help, here's some load data off my new build. 30" 1:7.5 Bart hanging off a Panda. .120fb reamer used to chamber it.

    I'll be shooting my N140 & Varget loads this weekend. If neither of those pan out the way I'd like, I'm probably going to swap to a CCI primer to see if it doesn't prefer that.

    6GT Data.PNG
     
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  17. Hoodoo

    Hoodoo Site $$ Sponsor

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    That's a great chart. Any velocities for the N140?
     
  18. Spook

    Spook Captured too late to be fully domesticated.

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    fwiw , Had the 6GT at the range t'day shooting 107smks over 40+ grains of Staball , new Alpha brass.... pretty wide velocity swings.
    I'm thinking Staball wont be my go to powder for this cartridge.
     
  19. MikeMcCasland

    MikeMcCasland Gold $$ Contributor

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    Just got back from the range; here you go.

    Datatodate.PNG
     
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  20. Hoodoo

    Hoodoo Site $$ Sponsor

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    Thanks! I've now got 7 rounds through my barrel. I'll post when I've done my powder ladder with n140.
     

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