7mm-08 Sub-sonic Load

[JMRhino]

I realize that this may be a solution for a problem that doesn’t exist but I thought I would post in case it helps someone.

I was in search of a sub-sonic 7mm-08 load and couldn’t find what I needed. I used the Hodgdon data base that gave great info for 308 and 243. I have personally used the data for the 308 and have had great success with Hodgdon tight group and 168gn Sierra GMHP.

I tested 6, 6.5 and 7 gns in my Tikka 7-08 w/ a 16” barrel and observed the following:

7mm-08 (Fed Brass)
Ginex LR primer
Speer 145 Grand Slam

6.0 grains Tight Group (Average 800fps)
1. 857 fps
2. 802 fps
3. 741 fps

6.5 grains Tight Group (Average 886)
1. 850 fps
2. 886 fps
3. 921 fps

7.0 grains Tight Group (1047 fps)
1. 1070 fps
2. 1038 fps
3. 1034 fps

The ES and SD came down significantly on the highest load to 35 fps and 19.4 respectively. I have not been shooting for groups yet but all seem adequate. I realize that this a small sample size.

The rifle is capable of sub-MOA groups with super loads in CFE223 and Barnes 120gn TTSX for mid-Atlantic Whitetails….

Hope it helps someone if they are looking for a sub-sonic 7-08 load in a bolt action rifle.

 

[frankm]

Thx for sharing…. Guessing a 150 gr bullet with 6.5-7.5 grs of tight group would be safe?

Could use my chrono to see when velocity was 1000-1050 ish …

Are the loads fairly quiet and assuming no hang fires with the minimal amt of powder in the case?

 

[JMRhino]

I believe so but would start on the lower end. I have also loaded some Nosler 160 BT with tight group but I am not sure if 1/9.5 will stabilize that weight projectile. I will probably test without the suppressor first…

 

[JMRhino]

Missed the question. They are very quiet. Sounds like a pneumatic nail gun…

 

[frankm]

Thanks for info. Pls share your results as you progress… I m interested in doing this same deal for my 20” Howa SL in 7-08.

 

[Hunter26]

Very cool. Titegroup is pretty position insensitive but I've never tried it in a case that big. I've done some mouse fart loads with Titegroup in the 44 mag and never had ignition issues though.

 

[frankm]

Is tightgroup a flattened ball powder or flake? I don’t have any yet?

 

[JMRhino]

It appears to be a flake type powder with a little more body than standard ball powder.

 

[JMRhino]

I may hijack my own thread. I originally wanted to create a sub load for the 7-08 using some bulk 160 Nos BT that I have but I have never loaded those as super sonic rounds in my rifle. My tikka is a 9.5 twist and I think they can stabilize those but I thought that starting with the 145 Speer GS, for subs, would be a safer place to start. More to follow…

 

[Hunter26]

Some websites have twist calculators like Berger to see if those 160gr BT's would stabilize or not.

 

[JMRhino]

Perfect. According to the Berger calculator they are marginally stable at 1000 FPS and comfortably stable at 2500 FPS.

Thank you.

 

[JMRhino]

I realize that this may be a solution for a problem that doesn’t exist but I thought I would post in case it helps someone.

I was in search of a sub-sonic 7mm-08 load and couldn’t find what I needed. I used the Hodgdon data base that gave great info for 308 and 243. I have personally used the data for the 308 and have had great success with Hodgdon tight group and 168gn Sierra GMHP.

I tested 6, 6.5 and 7 gns in my Tikka 7-08 w/ a 16” barrel and observed the following:

7mm-08 (Fed Brass)
Ginex LR primer
Speer 145 Grand Slam

6.0 grains Tight Group (Average 800fps)
1. 857 fps
2. 802 fps
3. 741 fps

6.5 grains Tight Group (Average 886)
1. 850 fps
2. 886 fps
3. 921 fps

7.0 grains Tight Group (1047 fps)
1. 1070 fps
2. 1038 fps
3. 1034 fps

The ES and SD came down significantly on the highest load to 35 fps and 19.4 respectively. I have not been shooting for groups yet but all seem adequate. I realize that this a small sample size.

The rifle is capable of sub-MOA groups with super loads in CFE223 and Barnes 120gn TTSX for mid-Atlantic Whitetails….

Hope it helps someone if they are looking for a sub-sonic 7-08 load in a bolt action rifle.

Just a follow-up from my original posting using Nosler 160gn BTs and Tight Group. This test was mostly for velocities, but groups were all relatively consistent at half inch groups @ 50 yards. I think that the 7.5 - 7.7 range is the sweet spot for subsonic speeds out of my barrel.

Rifle: Tikka Lite 7mm-08 w/ 16" barrel and 9.5 twist
Brass: Norma
Primer: Ginex LR
Projectile: NOS 160gn BT

Load #1
7 gns Tight Group
Low: 882
High: 921
Ave: 897

Load #2
7.5 gns Tight Group
Low: 970
High: 975
Ave: 970

Load #3
7.6 gns Tight Group
Low: 946
High: 1050
Ave: 983

Load #4
8 gns Tight Group
Low: 1069
High: 1091
Ave: 1070