7 mm SHERMAN SHORTMAG vs 7 SAUM

[elkaholic]

Hi Rich, Ive been looking at the 280ai vs 7ss. You said the 7ss is more efficient. Just curious how much less grains will the 7ss use to reach a given velocity than the 280ai? For example, 180 vlds at 2900 fps?

About 58 grains but its not necessarily a straight up comparison. IMO, case design changes how powder burns and where/when peak pressure occurs with a given charge. I know this because my 280 Sherman (similar to an A. I.) will not outrun the SS even though capacity is a little more. I think the ss and A. I. are very close to the same capacity but an A. I. will not keep up even though they are both low body taper cases with a 40 degree shoulder.

 

[wapitiaddict]

60g of rl26 in the 7SS case gets me 3k.
No need to run 2900.... just sayin

I guess that was the other side of my question. What would the velocity of 60g of rl 26 be in a 280ai (assuming you can run 60g in 280ai...I'm not familiar), all else being equal (barrel length, etc). That's where the efficiency question comes into play that I'm looking for. Granted, maybe they are running at different pressures, but mainly just looking at grains to velocity, all else being equal.

 

[Broncoguy]

"All else being equal" is not even plausible.
Structure of a round is the case.... and Rich going to ADG - my opinion- is far superior to any 280 case offerings. Granted the 280ai is a great round, I've had a couple fabulous shooters, SS covers it all and some.

 

[elkaholic]

"All else being equal" is not even plausible.
Structure of a round is the case.... and Rich going to ADG - my opinion- is far superior to any 280 case offerings. Granted the 280ai is a great round, I've had a couple fabulous shooters, SS covers it all and some.

The A.I. is a great case for sure! If you run Norma brass in both, the A.I. will still not run with the SS.

 

[5RWill]

This is going to be a dumb question but for peace of mind i'm going to ask it. Just getting to fire forming. This semester has sucked. So got a little time. I've got some 150gr ballistic tips and H1000. I'm thinking 56gr of H1000 and those to fire form.

As far as resizing. Just barely touch the shoulder? I would think i'd want as little shoulder bump as possible considering i'm blowing it out? Or proceed to .002 bump per usual?

Also Rich do we have a place to get bump gauges if we went with forster?

 

[elkaholic]

This is going to be a dumb question but for peace of mind i'm going to ask it. Just getting to fire forming. This semester has sucked. So got a little time. I've got some 150gr ballistic tips and H1000. I'm thinking 56gr of H1000 and those to fire form.

As far as resizing. Just barely touch the shoulder? I would think i'd want as little shoulder bump as possible considering i'm blowing it out? Or proceed to .002 bump per usual?

Also Rich do we have a place to get bump gauges if we went with forster?

With the 150's I would use 58-59 grains of H1000. I probably wouldnt bump the shoulder until after the second firing.
I have some bump gauges.

 

[5RWill]

With the 150's I would use 58-59 grains of H1000. I probably wouldnt bump the shoulder until after the second firing.
I have some bump gauges.

Awesome, i'm going to get on it. The gauges on the site? Also thanks for the quick reply Rich, especially considering it's thanksgiving.

 

[jsthntn247]

This is going to be a dumb question but for peace of mind i'm going to ask it. Just getting to fire forming. This semester has sucked. So got a little time. I've got some 150gr ballistic tips and H1000. I'm thinking 56gr of H1000 and those to fire form.

As far as resizing. Just barely touch the shoulder? I would think i'd want as little shoulder bump as possible considering i'm blowing it out? Or proceed to .002 bump per usual?

Also Rich do we have a place to get bump gauges if we went with forster?

Leave the shoulder as tight as possible and jam bullets .010

 

[elkaholic]

Awesome, i'm going to get on it. The gauges on the site? Also thanks for the quick reply Rich, especially considering it's thanksgiving.

No, ill just send you one. Happy Thanksgiving
pm me your address

 

[Seandradamus]

My buddy had a 280AI last year it was 150-200 FPS slower than my 7ss
Now he has a 7ss and couldn't be happier.

 

[5RWill]

curious about the 180 ELDM in this caliber...what COAL are you using? Assume a short action was used?

Wonder if I can get it to move at 2800+ in a SA 2.950 COAL with a 22" barrel? if so I will be building one myself

I'll be able to update in two weeks soon as i can get home on the 13th. The 180 is a looonnng bugger. I didn't really look at COAL without the comparator but even at my lands it fit in my Alpha 7rd WSM mag which is 2.970 IIRC. Have a feeling because of the sheer length possibly dipping into powder capacity and the bearing surface of this bullet that 3000fps in my 24" proof is going to be hard to achieve realistically. As far as fitting it at 2.950" and achieving 2800-2850 out of a 22" barrel i think that should be doable.

I could be wrong on the COAL as i meant to repeat the process of getting my distance to lands with a fireformed case but upon trying to resize felt some significant resistance and went back to loading fireformed loads. Figured even a non fireformed case would give me some starting measurements though to ballpark it when i do fine the COAL with a fire formed case.

 

[5RWill]

Finally got them all fireformed. Wanted to see how 60gr of RL26 settled with this long pill. Not crunching can still hear powder moving despite being below the shoulder a bit. Which is great. Should be able to start shooting groups tomorrow.

 

[elkaholic]

Finally got them all fireformed. Wanted to see how 60gr of RL26 settled with this long pill. Not crunching can still hear powder moving despite being below the shoulder a bit. Which is great. Should be able to start shooting groups tomorrow.
View attachment 164927
View attachment 164928

Looking good!

 

[5RWill]

Pic next to dads 6.5 saum with a 143gr eld X at 2.970 roughly. First shot with 59.6gr of RL26 is getting me near target velocity already. Though moving to 59.8gr I've got an elector imprint. Should i have waited and fireformed a second time?