7mm Mashburn and IMR7977

[Leslil]

Have any of you tried this combo?
I loaded up a couple today to check fps. Starting with a 7mm wby min of 72.5grs clocked at 3148fps with a 160gr. Nosler PT. 73grs. gave me 3217fps. with no signs of pressure. I can not wait to load some more to see how they shoot.
For reference H1000 and a 162gr. AMax I need 75.5grs to hit my 3200fps mark.

 

[joelkdouglas]

Thanks for posting. I have a keg of IMR7977 and a Mashburn that's at Pac Nor right now. She will be chambered in Mashburn again, just a new barrel. I'm moving again next summer but this spring I should get a chance to try the combo out.

The down side is spring doesn't come to North Dakota until late in the year!

 

[Leslil]

I hear ya Joel. I'm in Minnesota so I know how long it takes spring to roll around. Good thing is, I hate bugs that bite and waiting for barrels to cool off. So the colder it gets the more I shoot. Another bonus is I have never had to deal with others at the range when it's below zero.

 

[BF375]

Have any of you tried this combo?
I loaded up a couple today to check fps. Starting with a 7mm wby min of 72.5grs clocked at 3148fps with a 160gr. Nosler PT. 73grs. gave me 3217fps. with no signs of pressure. I can not wait to load some more to see how they shoot.
For reference H1000 and a 162gr. AMax I need 75.5grs to hit my 3200fps mark.

Nice thing about the Mashburn is that you don't have to push it to the floorboards to get good velocity.

I worked up to that 75.5 gr H1000 load when I built mine a few years ago. It works great with the 162 Amax,160 NPT,160 AB, and 160 BBC,all at around 3200 fps.

 

[SJB358]

That sounds really good.

I'd think 7977 should be really good with the MSM. Then again a slew of slow burners work really well.

3200 with a 160 is exactly what I got from 75.5 of my old LOT of H1000. With my newer bunch I use 75.5 with the 175's at 3030 or so.

 

[Leslil]

I think I like the 7977. It seams to be easy to work with. It took 2 rounds to find my 3200 fps mark. I loaded up 6 more and put those into a tight but wide 1.58" group.

 

[Leslil]

Loaded up 5 more seated .015" deeper. 5 shots in .9". I think I'll load up 50 more.

13 rounds total for load development ain't to bad.

 

[SJB358]

Loaded up 5 more seated .015" deeper. 5 shots in .9". I think I'll load up 50 more.

13 rounds total for load development ain't to bad.

Nope, I'd say you're done.

Now I'll have to grab an 8lb'er for the next Mashburn. My current LOT of H1000 seems a little slow.

 

[Leslil]

I have some bad news friends. I shot today in -7 degree below zero temps. In a 70 degree temp swing I lost 100fps and accuracy went way south.

Back to the drawing board

 

[SJB358]

Hmmm, that's pretty danged bad.

Ever tried the same with H1000 or Retumbo?