7 mm SHERMAN SHORTMAG vs 7 SAUM

[Hunters Luck]

My 6.5SSs all feed flawlessly from a DBM mag or BDL with box magazine. A blind mag should be no different than a BDL style magazine box.

Excellent! Great to know sir! Thank you.

 

[Short Case]

I'm wanting to build a model 70 CRF SA into a 7SS or 7SST, and leaving it as a blind floor plate. Anyone done something similar, and does the SS feed ok from a mag or no bueno?

Hi luck, I have a Winchester model 70 6.5/270 WSM, it is the New Haven Ct. model
This is the one with the bottom of the bolt is open up and the round jump into it and
it feed ok with know problem, the round is in the bolt and then you put it in the chamber
What bullet are you going to use

 

[ormandj]

1:8 or 1:8.5 twist for a 7SS in a 20" barrel? I'll be using temperature stable powder, so no RL26 (have VV N565 to start with). I have no idea what bullet(s) I will be using. My range is out to 1760 yards, and I will also be hunting. I will be feeding from binderless box magazines (max COAL of 2.960", but I'd prefer to keep it 2.940" or less for reliable feeding). If the 190s/etc don't make sense in a 20" w/ the 7SS with this COAL limitation, then it's easy, I'll just go with the 1:8.5. The reamer is a standard reamer, as well. If they do, then read on!

I've asked everyone (thanks for the feedback @elkaholic !) and am just looking for a few more opinions since the barrel mfg, the gunsmith, and the cartridge designer all have slightly different opinions. They're all in the 1:8 to 1:8.5 range, and if I knew what bullet(s) I wanted it'd be easy. I'd just do a 1:8 if I knew I'd only shoot the 190+ or solids, but I don't know if that will be the case - I'll be shooting whatever my barrel likes best.

I've read SGs above 2 can cause some issues, and depending on the bullet and the temperature (I shoot in TX and in New England, so 100F+ down to 0F+), the 180s will be slightly above 2 SG in higher temperatures in TX, which makes it a bit tricker. That said, 1:8.5 drops the SG below 1.5 in colder temperatures with the 190-195s and some solids at the lower muzzle velocities I'm expecting due to the shorter barrel. I'm calculating based on ~2800fps with the 180-class and ~2700fps with the 190-class, which are hopefully somewhat reasonable for an _accuracy_ load in the 20" barrel (not max velocity) using temperature stable powders (no RL26, again).

Any tips will be helpful. I don't intend to shoot the really light bullets, I'd switch to another caliber for that kind of stuff (I have an 8 twist 6.5 Creedmoor if I want to shoot smaller critters), so it'll all be 170 and up for traditional bullets (monolithic might be different).

 

[Rhovee]

With a 7ss or 7 Saum, I wouldn't shoot anything over a 184 Berger. Not a big enough case. 180's are really good. But honestly in a 20" barrel I would look hard at 168 Berger's. They break even on performance at around 700 yards.

 

[ormandj]

That makes it easy (if there is consensus). I do shoot target too, and my personal range is out to 1760yds, so I will definitely be stretching this out there. I don't mind going transonic as most of the newer bullets handle that reasonably well, and I greatly prefer the shorter barrel when not at the range and out hunting since I shoot 100% suppressed.

 

[Short Case]

With your 2.940 COAL and 7SS case that leave you .990 of bullet out of the case
So if you use 195 Berger you will have .658 of bullet in the case, 180 Berger .516 in the case,
175 Berger .510 in the case, 168 Berger .443 in the case, the 168 might be the best bullet to use.

 

[elkaholic]

With your 2.940 COAL and 7SS case that leave you .990 of bullet out of the case
So if you use 195 Berger you will have .658 of bullet in the case, 180 Berger .516 in the case,
175 Berger .510 in the case, 168 Berger .443 in the case, the 168 might be the best bullet to use.

With the std .110" FB reamer, the 175 and 180 bergers have only most of the boattail in the case below the neck.
The bearing surface is ALL above the base of neck.
The 180 Hybrid is approx 2.920" to the lands

 

[DENRIK89]

TONS of good info on here, and its going to cost me money! I've got a 22" proof blank i've decided will be cut for 7SS but in 20+ pages nobody mentioned running 162 grain pills (i have 1200 Eld-m) and I have piles of h4350 H1000 and imr8133. Can someone help point me in the right direction and what to expect, are the 162s too short to run well the way the throats are setup?

 

[jsthntn247]

TONS of good info on here, and its going to cost me money! I've got a 22" proof blank i've decided will be cut for 7SS but in 20+ pages nobody mentioned running 162 grain pills (i have 1200 Eld-m) and I have piles of h4350 H1000 and imr8133. Can someone help point me in the right direction and what to expect, are the 162s too short to run well the way the throats are setup?

162's will be fine. Use the H4350 you have and you should be able to get them to 3k FPS. I'm running a 175 at 3k with a 24" barrel with R26. I used the 162's in a 7 mag and 7-08 for years and they did great on game and targets.

 

[Gstew1930]

TONS of good info on here, and its going to cost me money! I've got a 22" proof blank i've decided will be cut for 7SS but in 20+ pages nobody mentioned running 162 grain pills (i have 1200 Eld-m) and I have piles of h4350 H1000 and imr8133. Can someone help point me in the right direction and what to expect, are the 162s too short to run well the way the throats are setup?

I shoot 168's in mine. N560 has given me the best velocity

 

[WiscGunner]

That makes it easy (if there is consensus). I do shoot target too, and my personal range is out to 1760yds, so I will definitely be stretching this out there. I don't mind going transonic as most of the newer bullets handle that reasonably well, and I greatly prefer the shorter barrel when not at the range and out hunting since I shoot 100% suppressed.

I went with a 1:8 26" proof. Works great with both 180gr ELDM (60.1gr H1000 @ 2843) and 155Hammer Hunters (57gr H4350 @ 3067fps). Using an ARC aics style magazine with a Bighorn TL3 short action. Lighter solids don't mind extra spin as they won't come apart like a light weight jackets bullet with too much spin.

 

[ormandj]

How are 175 Extreme Hunters and 180 Hybrids with the 1:8?

I can also do a 1:8.25" since it's a custom.

@elkaholic would the 184 Berger Hybrids work well at 2.94" COAL or less with the standard reamer?

 

[Shooter264]

The 180 hybrid shot ok with a 1 in 8 . 22" 7 SS.

 

[ormandj]

Yeah, that doesn't seem too bad. Haha. If the 175 EHs shoot the same way then it sounds like 1:8 is a good bet.