6mm-284 winchester reloading advice needed

[Shawn Shawn Carverelli]

some 15 years ago I had a Rem 700 220 swift that lost its accuracy after shooting prairie dogs until the barrel got hot.
I enlisted a gunsmith in Plains, Montana to swap the barrel for a 30" long 1 3/8" no contour Lilja with a 1-8" twist. He chambered it in 6mm-284 winchester with a tight neck. I neck turned the brass after necking down 6.5x284 Lapua brass.
During load testing with the Sierra 107 gr Match king I had several bullets disintegrate before they hit the target. I was using reloader 22. I think I came down a few grains to 54 and got decent accuracy. Later I tried some H1000 I had on the bench and shot one group at 300 yards into a cloverleaf, but velocity dropped from 3350 with 54 gr of reloader 22 to 3100 with h1000. I got busy with work and life and havent shot the rifle in probably 10 years. I'm older now, empty nester and would love to pick this project back up.
Is there any bullet/powder combos that are fairly new that sound promising?
I built the gun for long range prairie dogs and would like to get 3300 fps.
The idea with 30" barrel was to cut/rechamber after the chamber throat saw enough erosion that accuracy started to suffer. The rifle is a heavy sumbuck and I poured molten lead onto the hollow HS Precision stock to help balance out the big barrel. My idea was to make it heavy enough to see bullet impact so I could spot subsequent shots

 

[Djfergus]

Im tinkering with a 6mm prc right now. It's ballistically the same as your 6-284. Mine is 8 twist also. More than likely you have a 4 groove barrel. The 107 smk has a very thin jacket. The 4 groove combined with the thin jacketed 107 smk at ultra high velocity is probably why you are slinging the Jacket off. Try the 108 BT target Berger. This bullet has a little thicker jacket. Any of the Berger target bullets will have a little thicker jacket and resist getting the jacket slung off. As far as powder, H1000 will give you great velocity along with better barrel life. It's hard to find. Ramshot Magnum will be easier to find right now and will give you great velocity. But I'm guessing that you will be fine with R22 if you get a bullet with a little thicker jacket.

 

[longbow]

I shot a 6.5 Gibbs for 1K in mid 90's then I shot 6-284 in late 90's till I met 6 Dasher. I was at 54 gr RL-15 ? I know I finally backed it off to 3000 FPS shooting Sierra 105's. It won some Matches and alot of guys started seeing that you didnt need a 30 cal to compete. The 6-Dasher could do the same with less powder.I cooked that barrel in one season!

 

[rogina]

some 15 years ago I had a Rem 700 220 swift that lost its accuracy after shooting prairie dogs until the barrel got hot.
I enlisted a gunsmith in Plains, Montana to swap the barrel for a 30" long 1 3/8" no contour Lilja with a 1-8" twist. He chambered it in 6mm-284 winchester with a tight neck. I neck turned the brass after necking down 6.5x284 Lapua brass.
During load testing with the Sierra 107 gr Match king I had several bullets disintegrate before they hit the target. I was using reloader 22. I think I came down a few grains to 54 and got decent accuracy. Later I tried some H1000 I had on the bench and shot one group at 300 yards into a cloverleaf, but velocity dropped from 3350 with 54 gr of reloader 22 to 3100 with h1000. I got busy with work and life and havent shot the rifle in probably 10 years. I'm older now, empty nester and would love to pick this project back up.
Is there any bullet/powder combos that are fairly new that sound promising?
I built the gun for long range prairie dogs and would like to get 3300 fps.
The idea with 30" barrel was to cut/rechamber after the chamber throat saw enough erosion that accuracy started to suffer. The rifle is a heavy sumbuck and I poured molten lead onto the hollow HS Precision stock to help balance out the big barrel. My idea was to make it heavy enough to see bullet impact so I could spot subsequent shots

I had success with Retumbo and 105's.

 

[Rope2horns]

Retumbo and RL33. This cartridge is so over bore a lot of the slower powders work well.

 

[birdog]

In such a large case for caliber, why not try the 115 Berger or DTAC. Works well in 6 / 284