Help me figure this one out!!!!

[CZ550]

Okay I have two barrels chambered up for my PD trip in June a 20br and a 14 twist 6br.
With the 20br and a 55gr Berger my load is 33.3 rl17 @ 3700fps. I have been working on the 6br running the 58gr vmax and 34gr of Varget shoots very well but is only 3350fps. I was working some loads the other day and thought that if rl17 worked best in my 20br with a 55gr bullet then it would work well in my 6br with a bullet that is very close in weight being the 6 and .20br are same case just smaller hole. So I loaded some up and went out to the bench, rifle was zeroed @ 375 yards with the varget load. My first three shots with 32gr of rl7 were about a foot low of POA. Then 3 shots this 33gr of RL17 I was still 8 inches low. Knowing the velocity of my Varget load I didn't even bother chronoing the rl17 because it is obviously lots slower than 3350 judging by impact on the target. I am puzzled as to why I didn't get similar results in both rifles? I figured I would get at least 3500-3600fps.

Thanks Corey

 

[soldierofchrist]

RL17 is to slow of a powder for the light stuff out of the 6mm BR, My favorite powder for the 55 and 58 grain bullets is VV N133, I use 32.0 grains with a CCI 450 primer and get 3850 fps with them. If you want to stay with Alliant use RL7 and i bet it will put a smile on your face. The 22 caliber, because it has a smaller bullet diameter will do better with slower powders compared to the bigger bore of the 6 BR. Other powders that work well are N135, H335, WW748, AA2230(gets them to 3900 fps+), don't use it because it heats my barrel up very quickly and I shy away from ball powders because i find them more temperature sensitive then extruded powders. Varget shoots accurately but you run out of case capacity and it is the limiting factor there.

 

[SmokinJoe]

Soldier, I think you meant RL 15? I am assembling parts to build 2 similar rifles, so interested in this thread. Defiance actions, Jewell triggers, MacMillan Winchester Marksman pattern stocks and Krieger 1-14 barrels left over from my group shooting days. Planning to shoot something like 70 Blitz Kings in them.

Maybe I misread soldier's post, thought it said RL17, now I see it says RL7. My apologies.

 

[soldierofchrist]

RL15 is almost the same burn rate as Varget it will work well with the 70 grain bullets, but RL 7 is a great powder with the 55's, those light bullets like the faster burning powders. AA2230 got me the fastest velocity with 3950 fps using 34 grains and a CCI 450 primers with a 55 SBK, But I got the best ES and SD with N133 which got me 3850 fps and my SD was 3 fps whereas i was running a 50 fps SD with the AA2230. The load I have actually settled on is 30.5 grains of N133 with a 65 grain V-max which goes about 3575 fps for me. My rifle is is Rem 40x in 6BR 1 in 12 twist with a .266" neck that is 27.5" long.

 

[soldierofchrist]

not to say that RL15 or Varget won't work, they shoot accurate, just if your looking for more velocity jumping down to the faster burn rates helps, I topped out at 3650 fps with Varget which is plenty effective on Varmints but you can get the velocity higher.