7 mm SHERMAN SHORTMAG vs 7 SAUM
- Thread starter elkaholic
- Start date
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COAL with the 180 Hybrids is 2.9405 (.015 off the lands). I was using regular LR primers (CCI BR2).
That's my next powder to try.......What primers did you use?
elkaholic
Well-Known Member
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.......
cjl2010
Well-Known Member
I've had 2 6.5ss with the same issues.
dirtytough
Well-Known Member
My 7SS with the 180 ELD was right @3003 fps with RL 26. 26" Bartlein. That was Norma brass.
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.
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.
Mine shoots like that also at 2810fps. Kinda crazy.
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.
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.
Rhovee
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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?
Rardoin
Well-Known Member
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?
