7 mm SHERMAN SHORTMAG vs 7 SAUM

[elkaholic]

Has anyone hooked up an RSI PressureTrace system to a barrel in this chambering? Might be interesting...

People often ask what pressure we're running and the truth is, I don't know! The question I get a lot is "how can you shorten a parent case and make it shoot faster"? Glad you asked! ,
(1)There is no loss of capacity in the SS case vs the saum. Even though it is considerably shorter, with the taper blown out and the shoulder sharpened, the capacity is nearly identical. (2)Because it is far shorter, the bullet can be seated out into the neck so that useable capacity is MORE that the Saum. (3) the shorter burning column and 40 degree shoulder make the SS more efficient getting more out of the charge. (4) with low body taper, the pressure is distributed better throughout the chamber (less bolt thrust) this allows higher operating pressure without destroying brass. SS shooters will vouch that brass lasts longer at higher velocities than the Saum will reach
All these things are exactly why the SS was developed. To be the best performing cartridge available under 3" coal. You can get close to SS velocity with a saum, but you have to have a 3.1" coal to do it, and even then, you will likely come up a little short. I'm sure there are people who load hot, as with any cartridge, but the 7ss isn't running 3000' with a 180 vld by running dangerous pressure when the brass is lasting double digit loading! The skeptics should try it and see for themselves!

 

[Ackley Kid]

Rich neat little cartridge for sure ! I shoot a 300 WSM out of a Rem 700 SA and can defiantly agree with you on the OAL situation that exists with the short mags , I believe it even has a Whyatt box ( BDL set up ) and still isn't quite enough there . As you have explained above , the case design holds pressure better as do the AI . Lots don't believe it because it is hard to measure without $$$$$ gauges , or they need some scientific result to verify . Case heads don't lie , but quick load might if you don't know how to run the inputs well ( I'm in that camp ) If you look what the BR guys have done with the 6BRA it's hard to debate but ....they still do ? I'm certain that I will try one out at some point . Clever idea for sure if you have a short action kicking around . Best of luck to you !

 

[milanuk]

hard to measure without $$$$$ gauges

RSI PressureTrace isn't that expensive... especially compared to brass, reamers, dies & barrels for a wildcat.

or they need some scientific result to verify

Yeah that's just crazy, isn't it?

Case heads don't lie

Actually, they can and do. Ackley case designs are, if I'm not mistaken, pretty well known for gripping the chamber walls more (due to the lack of body taper) and reducing bolt thrust - which in turn tends to 'mask' the traditional pressure signs that people 'read' on the case head. That doesn't mean that the pressure isn't there, just that you can't see it until its *really* high...

If you look what the BR guys have done with the 6BRA it's hard to debate

Last I checked I don't see the guys running BRAs *faster* than the Dasher, and claiming it's because it's more 'efficient'...

Not saying that I'm not intrigued by the whole cartridge - quite the opposite. I simply asked a question. No need to get your knickers in a twist

 

[elkaholic]

RSI PressureTrace isn't that expensive... especially compared to brass, reamers, dies & barrels for a wildcat.



Yeah that's just crazy, isn't it?



Actually, they can and do. Ackley case designs are, if I'm not mistaken, pretty well known for gripping the chamber walls more (due to the lack of body taper) and reducing bolt thrust - which in turn tends to 'mask' the traditional pressure signs that people 'read' on the case head. That doesn't mean that the pressure isn't there, just that you can't see it until its *really* high...



Last I checked I don't see the guys running BRAs *faster* than the Dasher, and claiming it's because it's more 'efficient'...

Not saying that I'm not intrigued by the whole cartridge - quite the opposite. I simply asked a question. No need to get your knickers in a twist

Good post and pretty accurate. I don't mind people commenting who know what they are talking about. Ive had a few follow me around making statents that make my head hurt!

 

[Capt RB]

RSI PressureTrace isn't that expensive... especially compared to brass, reamers, dies & barrels for a wildcat.



Yeah that's just crazy, isn't it?



Actually, they can and do. Ackley case designs are, if I'm not mistaken, pretty well known for gripping the chamber walls more (due to the lack of body taper) and reducing bolt thrust - which in turn tends to 'mask' the traditional pressure signs that people 'read' on the case head. That doesn't mean that the pressure isn't there, just that you can't see it until its *really* high...



Last I checked I don't see the guys running BRAs *faster* than the Dasher, and claiming it's because it's more 'efficient'...

Not saying that I'm not intrigued by the whole cartridge - quite the opposite. I simply asked a question. No need to get your knickers in a twist

You should chamber a 7ss run the 180 or 195 and get bette barrel life than the 7saum guys in F-class. I hear you might have an idea how to do that

 

[milanuk]

You should chamber a 7ss run the 180 or 195 and get bette barrel life than the 7saum guys in F-class. I hear you might have an idea how to do that

The question is... how the barrel life stacks up against the .284 Winchester in a competitive format? Relatively few guys actually run the SAUM, unless it's a dedicated 1k-only gun or they shoot at *really* windy ranges - but those that do seem to really like it.

Seeing as our 'local' range has a bit of a rep for wind, it's been crossing my mind. That brass cost though... holy schnikey. 50 pcs for a hunter isn't that bad... but when you start looking in terms of 200-300+ pieces for a multi-day event... ouch. Not even remotely the biggest expense in the sport, but still enough to give a person pause.

I've been thinking pretty hard about getting a couple extra bolt heads for the Bighorn Origin action I have on order... considering either a 7 SAUM or a 7 SS or SST for the occasional hunting, maybe some of the extended LR field / PRS matches.

 

[elkaholic]

The question is... how the barrel life stacks up against the .284 Winchester in a competitive format? Relatively few guys actually run the SAUM, unless it's a dedicated 1k-only gun or they shoot at *really* windy ranges - but those that do seem to really like it.

Seeing as our 'local' range has a bit of a rep for wind, it's been crossing my mind. That brass cost though... holy schnikey. 50 pcs for a hunter isn't that bad... but when you start looking in terms of 200-300+ pieces for a multi-day event... ouch. Not even remotely the biggest expense in the sport, but still enough to give a person pause.

I've been thinking pretty hard about getting a couple extra bolt heads for the Bighorn Origin action I have on order... considering either a 7 SAUM or a 7 SS or SST for the occasional hunting, maybe some of the extended LR field / PRS matches.

The brass is a little spendy right now but consider that it lasted 20 firings with a stiff load in my sst and was still going strong, it's a bargain! Also, capacity variation of h20 was .1 gr.
I expect the brass price to drop as the volume orders pick up.
I just got off the phone with ADG and they have the new thin walled brass figured out and ready to run at .014" in 7mm.

 

[Capt RB]

The question is... how the barrel life stacks up against the .284 Winchester in a competitive format? Relatively few guys actually run the SAUM, unless it's a dedicated 1k-only gun or they shoot at *really* windy ranges - but those that do seem to really like it.

Seeing as our 'local' range has a bit of a rep for wind, it's been crossing my mind. That brass cost though... holy schnikey. 50 pcs for a hunter isn't that bad... but when you start looking in terms of 200-300+ pieces for a multi-day event... ouch. Not even remotely the biggest expense in the sport, but still enough to give a person pause.

I've been thinking pretty hard about getting a couple extra bolt heads for the Bighorn Origin action I have on order... considering either a 7 SAUM or a 7 SS or SST for the occasional hunting, maybe some of the extended LR field / PRS matches.

His 6.5 ss pushing the 150smk's at 31-3200 for the longer matches would be a real tough combination also. Load the 147's or the matrix 160's for hunting till the Bergers get released. All will have sd over 3 and they fly well in the wind with more speed/bc than the 180/7mm outside of the eldm's

 

[JOM74]

Following

 

[kingston]

Are you guys who are shooting the 195EOL doing it in 1:7 twist or 1:8 twist barrels? Length?

 

[BlackHillsSD]

Are you guys who are shooting the 195EOL doing it in 1:7 twist or 1:8 twist barrels? Length?

I'm running a 1:8 twist barrel at 26", with the 195's running 2925 FPS.

 

[elkaholic]

I'm running a 1:8 twist barrel at 26", with the 195's running 2925 FPS.

Most I'm aware of are running 8 twist

 

[Ah1356]

I'm just getting started, by my 7SS is an 8 twist. Fireforming loads are sub 1/2MOA at 100 and show great promise at 1,000. Can't wait for dies so I can really see what she can do...

 

[elkaholic]

Dies should be here this month