7 mm SHERMAN SHORTMAG vs 7 SAUM

Mine is a 23" and shoots the 190s at 2810. I didn't build it to beat my old 7mm Rem Mag. I built it to be real close but in a short action, shorter barrel. With a 26" barrel and the 180s I'd expect you to be ~2925-2950. I shoot N565 with the 190s and am loading 64.1gr. COAL is 2.960. I also used to shoot RL23 and my load was 60.2gr @ also shot 2810fps.

What's your COAL? Are you using a standard LR primer or magnum? I use Federal 210Ms. Seems you're pressuring out early to me...
COAL with the 180 Hybrids is 2.9405 (.015 off the lands). I was using regular LR primers (CCI BR2).
 
Mine is a 23" and shoots the 190s at 2810. I didn't build it to beat my old 7mm Rem Mag. I built it to be real close but in a short action, shorter barrel. With a 26" barrel and the 180s I'd expect you to be ~2925-2950. I shoot N565 with the 190s and am loading 64.1gr. COAL is 2.960. I also used to shoot RL23 and my load was 60.2gr @ also shot 2810fps.

What's your COAL? Are you using a standard LR primer or magnum? I use Federal 210Ms. Seems you're pressuring out early to me...
The fact that he's pressuring at 62.5 grains with a 180 and you run a 190 at 64 tells me all I need to know, regardless of speed.
 
The fact that he's pressuring at 62.5 grains with a 180 and you run a 190 at 64 tells me all I need to know, regardless of speed.
Yep......I bought a 750.00 paper weight. Kind of defeats the whole purpose of the cartridge.......
 
That's my next powder to try.......What primers did you use?
I used CCI250's but like Rich says, I wouldn't waste any more components chasing. Only home remedy possibly is to lap your barrel with bore bright paste and polish…… load 6 or so of one of your documented load- couple to foul the others for data and see if you speeds increase. If not call manufacturer.
 
Just want to know if anyone else has a barrel as slow as mine.........

Just had a 7SS put together with Impact 737R action and Bartlein Carbon Fiber, Sendero Contour, 8 twist at 26" finished length.

I have 88 rounds down this gun and it doesn't seem to be getting any faster. Most Bartleins I've had speed up after 50-60 rounds.

I'm using BR2 primers and 180 Hybrids with a .020 jump. I started with N565 (59-62.5 in half grain increments) and hit pressure at 62.5 grains (2871 fps). 62.0 grains was 2859 fps but terrible grouping at .920" with SD of 13 and ES of 26. 61.0 grains (2800 fps) shot into a .368 group.....Again not great and terrible SD and ES.

Next powder was RL23 (54-58.5 in half grain increments) and hit pressure at 58.5 grains (2854 fps).

Finally tried 168 VLD Hunters with H4831SC (59-60.5 in half grain increments) and hit pressure at 60 grains (2889 fps). Shot under a quarter inch with the starting load of 59 grains and SD of 7 but velocity was only 2850.

Very frustrating to see all these people hit in the 3000s with no pressure while I get these results.......
I shot a 7 Saum but is basically the same as your 7SS, using 61.7 grains of Retumbo with 180 Hybrid, BR 2 Primers, the same barrel as yours, except 7.5 twist, FPS is 3050 SD 6. Retumbo is about 92% case fill in Nosler brass, on a good day for me .3 group. You might try the Retumbo or N570 to get your FPS up there. I have about 50 rounds down the tube to date after load development.
 
I have had my 24" 1:8.4" 7SSfor about a month now. Mine REALLY loves the 184 Hyb. N565 at 100% case fill (62.5gr) is netting me 2838fps so far with 48 rounds down the barrel and no pressure signs. RL23 maxed out at 2798fps with a full case. No pressure again.

2811fps
View attachment 315095
2838fps
View attachment 315096
2861fps
View attachment 315097

Shot a 10 shot group over 2 hours on Friday in the .4s.

Trying some 165 TGKs tomorrow with it too.
Mine shoots like that also at 2810fps. Kinda crazy.
 
The fact that he's pressuring at 62.5 grains with a 180 and you run a 190 at 64 tells me all I need to know, regardless of speed.
Mine is also throated out a little. I don't remember how much but I think it's either 80 or 100 though. I did it to shoot the 147gr Badlands at mag length. My COAL to the lands with the 190s is 3.045. I load to 2.960.
 
Yep......I bought a 750.00 paper weight. Kind of defeats the whole purpose of the cartridge.......
Another option, you could either get your gunsmith to do it or buy a PTG unithroater, and cut a little more freebore into it to where you're jumping 40 Thou at 2.96 if your mag will accommodate it. Your pressure will come down from both the increased freebore and you'll be able to load a little longer increasing case volume. You'd then be able to get a little more powder in the case. With that, you might not get all you're hoping for, but my guess is you'd get a bunch of it.
 
Have you checked neck clearance? I have never had a slow Bartlein. Anything is possible. I am sure if you sent it back they could slug it and see if it meets spec. All the Barts I have owned actually took more pressure and powder than other barrels. I am shooting a 7 Saum with RL23 and 59.5 is 2910 in 26" barrel. Went all the way to 61..7 before pressure. Case volumes are close. Is it bolt lift or ejector marks your seeing?
 
I'm on my 5th 7 SS barrel (four 8.25tw Bartlein and one 8tw Schneider) shooting 190 A-tips mostly, some 190 and 184 hybrids. The ADG brass is very tough but if you hit it hard on the first firing and expand the body at the .200" line, just above the web, your sizing die may not be able bring the diameter down enough to prevent heavy extraction which will be manifested by a heavy bolt lift and a definite "click" at the top of bolt lift when the extraction cam breaks the case free. This is often confused with excessive pressure. I've had this happen. Two solutions, short of starting over with new brass, is either having a small based die made or, the easy way, having the lower 1/4 of the chamber opened up with emery cloth of an appropriate sized wood dowel with the barrel spun in a lathe. I'll repeat @Rhovee question….what are you seeing that suggests excessive pressure?
 

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