7 RUM w/150ET & 160AB

[Richracer1]

Here's what my 7mm RUM did with the 150ET. First, here's the specifics:
Brass: Remington, trimmed to 2.83"
Powder/Charge: 91gn of Retumbo (tried +/- .2 gn)
Primer: GM215M
OAL: 3.655 (tried various OAL once the charge was determined)

Here's the target:

 

[JD338]

Nicely done Rich!
Thats a .5xx" group! How far off the lands?

JD338

 

[Guest]

Very nice work, Richracer1. I'm looking at your COL, and wondering how that compares to the range of potential COL's for your rifle? Are you close to the lands, or are you short on the COL for the E-Tips? I'm asking because I've had two rifles so far need very short COL's for the E-Tips, and JD338 has experienced similar COL requirements for top accuracy for his rifle. Again, great shooting, and congrats on the load.

 

[Richracer1]

Sorry guys, I do not know how far from the lands as I found that I can't exceed 3.67" COL and utilize the magazine. So I don't check for that on my RUMS. My starting COL to find the preferred powder charge was 3.665". That COL and 91gn got me about an inch MOA. I then loaded some up with different COLs, 3.65 3.655, 3.66, 3.67. I went out to chrono the 30-06 180ET, 270WSM 130 ET, this one and my CA 338RUM 225TSX-FB loads. I'll chrono this stuff at a later date, when the wind isn't moving the skyscreens around.

 

[Richracer1]

You got me curious on the COL measurement. I checked the 7RUM and came up 4+" COL to touch the lands, but then the bullet is barely seated in the brass.

 

[Richracer1]

5 shot average velocity is 3200fps

 

[FOTIS]

5 shot average velocity is 3200fps

Not too shabby

 

[Richracer1]

Finally got the motivation to go out Saturday to test the 160AB rounds I loaded up. Here's the specifics:
Brass: Rem trimmed to 2.83"
Primer: GM215M
Powder: 91gn of Retumbo
COL: 3.635"
Velocity: ????? Forgot the chrono - will get it later
Group size: see picture (sorry about the blurriness)

Forgot to add that this is the secondary bullet for my RUM. I plan on using the the 150ET primarily. It's good to have a back up plan or load.

 

[DrMike]

That is a shooter, for sure. The loads look very good.

 

[JD338]

Rich,

You are set to go, two nice loads for sure.

JD338

 

[Richracer1]

Thanks guys. Interesting enough, 91.5gn of Retumbo made a slightly larger group than 91gns, but I'll still use the 91gn recipe.

 

[DrMike]

Isn't it interesting how that "little tich" more can open up a group. A surprising number of my most accurate groups are below max charge. Accuracy is not strictly correlated to velocity. Most game is not impressed by that extra velocity.

 

[JD338]

Isn't it interesting how that "little tich" more can open up a group. A surprising number of my most accurate groups are below max charge. Accuracy is not strictly correlated to velocity. Most game is not impressed by that extra velocity.

+1
Same here. Several loads are 1-2 grains below listed MAX.

JD338

 

[Greg Nolan]

Rich
Thanks for all the info.
I've just bought some 150 ETs for my 7RUM. Now I have a load to work with. :grin:
Greg

 

[Richracer1]

Isn't it interesting how that "little tich" more can open up a group. A surprising number of my most accurate groups are below max charge. Accuracy is not strictly correlated to velocity. Most game is not impressed by that extra velocity.

The 91.5gn group size would've been a keeper, but the 91gn group was just a hair smaller. I'll post up the 91.5gn target when I get home, I'm at work now.

 

[DrMike]

RR,

I'm with you on choosing the most accurate group. Few animals are impressed by velocity, but accuracy sure seems to get their attention.

 

[Richracer1]

Here's a pic of the group using 91.5gn of Retumbo. Everything else is the same as the 91gn 160AB load info.