7mm SAUM big surprise

[toddc]

.338 Edge data is with long barreled, long throated rifles just like your 7mm SAUM is setup. 99% of the book data with a 7mm SAUM is with a 700 Remington with a 22-24" barrel running at short action OAL. I'm guessing you have a 26-28" barrel and you are a whole lot longer than book specs. Thus you are gaining 200fps over book data. Same thing with a .300 Win Mag, book said 2850fps with a 24" barrel loaded at 3.4" using a 200gr bullet. I loaded mine at 3.650" and shot them through a 26" tube and got 3050fps. No excessive pressure either. Same with the 190s, everyone runs them at 2900 in a .300 WM I pushed mine to almost 3150fps before getting extractor marks. If there's no pressure signs and everything is working, roll with it.

Always been my way too, but I have never run into being over max speed at 5 gr under. Of course I never have built a short mag unless a 22-284 or 6-284 qualifies. This is my first fling with an "EFFICIENT" rig. My STW from back in the 80s didn't do a whole lot more than this thing is and it was a lot more powder in a lot bigger case. Maybe these short mags have a point. I had planned on being at least a few gr over max because of the COAL. Seeing those results backed me up a bit which is a hard thing to do for a guy who usually just loads Retumbo to the top of the case and crushes the largest for caliber pill in it and then has someone else shoot it for him.

 

[toddc]

.338 Edge data is with long barreled, long throated rifles just like your 7mm SAUM is setup. 99% of the book data with a 7mm SAUM is with a 700 Remington with a 22-24" barrel running at short action OAL. I'm guessing you have a 26-28" barrel and you are a loading a lot longer than book specs. Thus you are gaining 200fps over book data. Same thing with a .300 Win Mag, book said 2850fps with a 24" barrel loaded at 3.4" using a 200gr bullet. I loaded mine at 3.650" and shot them through a 26" tube and got 3050fps. No excessive pressure either. Same with the 190s, everyone runs them at 2900 in a .300 WM I pushed mine to almost 3150fps before getting extractor marks. If there's no pressure signs and everything is working, roll with it.

You had a heck of a 300WM. I have worked with quite a few Ultras that didn't beat that by much and had one I couldn't get over 3k with a 210 no matter what I tried.

 

[toddc]

These are the loads that surprised me. This is 7WSM load map from accurate shooter. They usually run stuff as hot as they want and run longer tubes. This is why I was figuring 2900.

7mm WSM Load Map
Powder
Grains
Primer
Bullet
Velocity
Comments
H1000
66.5
Fed 210M
180gr JLK VLD
2900
Win Brass. 1/4″ at 100 yards. Near Max. 2.312″ Base to Ogive.
H1000
66.2
Fed 215 Mag
180gr Berger VLD
2950
Win Brass. Good load (1/3 MOA) for LR precision or tactical matches
IMR 7828 ssc
63.50
Fed 215 Mag
180gr Berger VLD
3010
Slightly more Velocity than H1000.
Norma MRP
63.0
CCI 250
180gr Berger VLD
3000
Accurate Load. Charge weight varies with powder lot.
H4831sc
61.0
WLR
175gr Sierra MK
2830
R. Horst LR load. Win Brass. Ultra-accurate in 9-tw Broughton 5C barrel.
Win S780
63.0
Fed 215
175gr Speer MagTip
2850
Hodgdon Max load, .2.760″ COAL, 60.5K psi.
RL 22
62.2
Win LRM
168gr Sierra MK
2850
Sierra Accuracy Load, .2.830″ COAL.
Win S780
67.5
CCI 250
168gr Sierra MK
2940
Hodgdon Max load, .2.850″ COAL, 3200 ft/lbs.
H4831sc
64.0
WLR
162gr Horn
A-Max
2950
R. Horst hunting load. Win Brass. Accurate in 9-tw Broughton 5C barrel.
H4350
63.0
Win LRM
150gr Sierra BT
3100
Sierra Hunting Load, .2.815″ COAL, 61K psi.
RL 17
63.5
Fed 215
145gr BTSP
3166
Alliant Load Data, 2.760″ COAL.
H4350
69.0
Win LRM
120gr Sierra SPT
3400
Accurate, Low ES/SD, hunting/varmint load, .2.795″ COAL.
RL 25
66.0
Fed 215M Mag
180gr Berger VLD
3050
Norma Brass. Bottomley 7mm-300 WSM load (smaller capacity case).
VV N570
n/a
Fed 215M Mag
180gr Berger VLD
3000
Norma Brass. Bottomley 7mm-300 WSM load (smaller capacity case). Good Velocity.

 

[J E Custom]

The case design of any short fat case it to improve powder burn consistency and shorten the travel of the flame front. Most all of the leading bench rest cartridges are short fat cases for that reason.

Efficiency breeds consistency, so an efficient cartridge is normally also very accurate. The difference in velocity between a standard barrel and a premium barrel is normally 30 to 50ft/sec with all other things being equal. I have never seen/heard of a 200 ft/sec increase so there is more than a good barrel involved.

The short mags can have many different shoulder angles and still perform. The main advantage of a 40o shoulder is brass life both the 7 SAUM and the 7 WSM have 30o shoulders and perform well.

Most re loading book velocities are calculated not actually fired, so book velocities may not be as accurate as actually chronograph velocities. with all the right combinations higher velocities are possible at SAAMI pressures.

Check questionable velocities on more than one chronograph to be sure and as long as there are no pressure signs, BE HAPPY.

J E CUSTOM

 

[toddc]

The case design of any short fat case it to improve powder burn consistency and shorten the travel of the flame front. Most all of the leading bench rest cartridges are short fat cases for that reason.

Efficiency breeds consistency, so an efficient cartridge is normally also very accurate. The difference in velocity between a standard barrel and a premium barrel is normally 30 to 50ft/sec with all other things being equal. I have never seen/heard of a 200 ft/sec increase so there is more than a good barrel involved.

The short mags can have many different shoulder angles and still perform. The main advantage of a 40o shoulder is brass life both the 7 SAUM and the 7 WSM have 30o shoulders and perform well.

Most re loading book velocities are calculated not actually fired, so book velocities may not be as accurate as actually chronograph velocities. with all the right combinations higher velocities are possible at SAAMI pressures.

Check questionable velocities on more than one chronograph to be sure and as long as there are no pressure signs, BE HAPPY.

J E CUSTOM

Oh I am REAL HAPPY. I just never get this lucky. Of course I am used to people claiming 3500 FPS from a 264 WM and trying to get there. When I saw the 5 gr under max velocity I immediately put the gun down and checked chrono off of my two KNOWN rigs and then started whooping and hollering.

Question now is.....I'm .5 under max with no pressure. With the long COAL I had planned on running a few grains over max. Now that I see where I am, I would REALLY love to work up to a pressure sign but something is telling me to be HAPPY with 200 over with .5gr under and quit while I am ahead. IDK I guess I could ramp it up and see but every time I see someone running way faster than they should I ASSume something is off. Maybe not. Maybe I just got lucky. Also there isn't a ton of data floating around for the SAUM but comparing the speeds I am getting to listed RM, STW and RUM data makes me think I am out of bounds.