FYI-6.5 Sherman, 156 & Retumbo

[Bruce Hanson]

Ooops big fingers on small phone created post accidentally.

 

[Bruce Hanson]

I have been reading information on this site for a couple of years. As a matter of fact because of some information on here I switched from R17 to Retumbo in my 6.5x284. I gained only about 50fos, but it cut my group from .6 to .25 which is great.
I don't know what I bumped to make the last post, but I suppose that made everyone curiouse so I may as well join the conversation.

 

[dok7mm]

UPDATE : I was short of time today, but I did shoot a reduced charge of 59.0 gr Retumbo with the 156 eol @ 100, just to check out seating depth on 6.5 Sherman.

Doesn't seem to be much change with this bullet up close when you factor in conditions and shooter error. I wanted to find a bit tighter
seating depth, prior to shooting groups up to max velocity. Hope to get to that on Friday.

Fifteen to twenty thou jump seems to be sweet (for now).

Did the same seating test with 156 in the 6.5 SS and .030" jump was as small as I can shoot.

 

[reeldawg]

tagging in

 

[dok7mm]

Finally got around to jumping the Retumbo charges in my 6.5 Sherman & 156 EOL in 26" 3B.

CBTO-2.894", COAL-3.586", .020"
jump changed from 10 to 20 thou
( not sure if this was smart). New
Retumbo lot # of 16 pounds. I also moved to 200 yd, 3 shot groups. I don't know if the groups were my fault, the conditions ( wind was 3-7 mph and from 9:00 to a 12 mph head wind) or my seating depth change. Take your pick! Temperature varied from 68* to 76* over session.

I'm now going to load up 5 shot groups from 63.2 up to 64 grains and try them at 400-600 yds and see what happens.

Also, I ran a one shot pressure test in my 6.5 SS with my new 10# of N-565. Loaded 58 to 62.5 grs with 156 EOL in my 24" Bart 2b. My only pressure sign was a slight smear @ 62.5 w/temp at 80* to 84*. 61,61.5 and 62 went in same hole @ 100.

6.5 Sherman & 156 pictures below.

 

[dok7mm]

I like my first outing with the new N-565, it looks to average 20 fps increase per 1/2 gr over 10 loads in the 6.5 SS. Rich was spot on in suggesting this powder for this cartridge. I'm impressed, at least for now.

 

[Bro Dave]

Finally got around to jumping the Retumbo charges in my 6.5 Sherman & 156 EOL in 26" 3B.

CBTO-2.894", COAL-3.586", .020"
jump changed from 10 to 20 thou
( not sure if this was smart). New
Retumbo lot # of 16 pounds. I also moved to 200 yd, 3 shot groups. I don't know if the groups were my fault, the conditions ( wind was 3-7 mph and from 9:00 to a 12 mph head wind) or my seating depth change. Take your pick! Temperature varied from 68* to 76* over session.

I'm now going to load up 5 shot groups from 63.2 up to 64 grains and try them at 400-600 yds and see what happens.

Also, I ran a one shot pressure test in my 6.5 SS with my new 10# of N-565. Loaded 58 to 62.5 grs with 156 EOL in my 24" Bart 2b. My only pressure sign was a slight smear @ 62.5 w/temp at 80* to 84*. 61,61.5 and 62 went in same hole @ 100.

6.5 Sherman & 156 pictures below. View attachment 152069
View attachment 152074

What do you mean if the groups were your fault? I hope when I grow up I can shoot 200 yd groups like those

 

[dok7mm]

What do you mean if the groups were your fault? I hope when I grow up I can shoot 200 yd groups like those

It's one thing to have groups increase in size when you have high ES, but groups with low ES that shoot about the same...........
they are usually my fault.

 

[dok7mm]

My final dope with 6.5 Sherman is done. 156 EOL, 63.8 gr Retumbo, CBTO - 2.904", jump .010", 26" 5R 3b, 200 yd zero @ 1575' elevation,
70*, 28.40 Hg, 50 % humidity.

My Labradar was showing 3,127 fps average, but drops @ 600 yds were calibrated to show 3,050 for my accuracy load.

 

[rockwallraider]

My final dope with 6.5 Sherman is done. 156 EOL, 63.8 gr Retumbo, CBTO - 2.904", jump .010", 26" 5R 3b, 200 yd zero @ 1575' elevation,
70*, 28.40 Hg, 50 % humidity.

My Labradar was showing 3,127 fps average, but drops @ 600 yds were calibrated to show 3,050 for my accuracy load.

I had the same thing happen with my lab radar @ my 500 yd drops and finally realized it was my scope dials being off by a little

 

[Capt RB]

I had the same thing happen with my lab radar @ my 500 yd drops and finally realized it was my scope dials being off by a little

One of the biggest reasons for the discrepancies for speed or bc is that fact. If more did a tall target test they would see it and then you can change your per click adj amount to make it line up. It's not always the reason but it is more common that talked about

 

[elkaholic]

One of the biggest reasons for the discrepancies for speed or bc is that fact. If more did a tall target test they would see it and then you can change your per click adj amount to make it line up. It's not always the reason but it is more common that talked about

First thing I do when I mount a new scope is calibrate it. I usually measure at least 20 moa at about 50 yards

 

[dok7mm]

I did a tall target test when I bedded a new rail, changed rings and put a new barrel on. The March is good to go.

It's more likely the result of the 5-7 mph headwind.

 

[ssinrdg]

Thinking about trying Retumbo and the 156 also. Do you happen know how full the case is at your final dope? If any of the test loads were compressed, about what grain did it start.
Thanks