7 Sherman Short Mag

[Drahthaar]

Anyone running their SS in a bdl? Just curious on how they feed. The 7ss is on the short list of cartridges for my current build, but I need solid feeding from a bdl as this is a hunting rig that will spend considerable time a long way from replacement mags (I'm certain to figure out how to lose one in the field).

 

[Beeman]

Hopefully it feeds good out of a BDL. I’m building a 6SST and a 7SST on a BDL.

 

[Drahthaar]

My smith is really trying to discourage me from going with the 7ss BDL combo. I'd love to build as described, but sure dont want to end up with a very expensive rifle that doesn't feed worth a darn. I have heard the GAP has a BDL that is designed to address the feeding problems commonly associated with these types of cases. Hopefully someone with experience with that bottom metal will chime in!

 

[Sniper338]

Ouch. May have to do the SST. The shoulder angle is a hard one to get around for feeding.

Numbers they posted for the rounds are impressive. I did a lot of reading up on it a few weeks ago. Hard to go wrong with any of them for something different. The 6.5SS was probably the most impressive

 

[Beeman]

Yeah the SST is suppose to feed better. That’s why I decided to go that route over the SS. Rich told me the SS only gets about 50 fps more than the SST. Guess I’ll see in a couple months when my manners is done. I also thought about going with the HS BM/Clip system but kind of pricey! Curtis custom makes a nice one as well. But again $$$$.

 

[ShootDots]

When I first heard of the Sherman Short Mags, I had to have a look for myself. I found the web-site and laid my eyes on the 7mm Short Mag. The minute I saw it, I knew Mr. Sherman had hit a home run! I started reading as much as I could about it, then finally spoke at length to Rich. After much contemplation, I decided to embark on a build for 1000 yard and 600 yard F-Open competition. I ordered a special reamer from Rich as well as 250 pieces of brass and a competition die set. The components are still a few months away. I also ordered a Defiance Deviant action and a McMillan Kestros stock for it. The stock is still "more than a few" months away. Hopefully, by October, or thereabouts, I will have the rifle in hand. I plan on shooting the Berger 184 Hybrid out of it. I surely hope that it does as well as I believe it will.. The rifle is still so far off that the "suspense" isn't even having an effect quite yet! LOL!!!

 

[RampedRaptor]

I have about 700 rounds down mine. Primarily 180 hybrids. I have a thousand 184s on the shelf but the weather has been poor in Ohio so I haven’t done any load workup yet with them.

I could not get the 180s to shoot over 3000 FPS well. They would do great at short range but fall apart at 1k. I don’t know why, at 2970 or so they shoot wonderfully. There’s more in the tank to go faster but with my barrel the accuracy was not there.

I was able to “tune” the feed lips of the ARC mags to feed perfectly but it took some time but no issues since the original feed lip bending.

Rethinking the 7SS, I don’t know if I’d do it again. It’s a great cartridge but not being able to push the 180s faster kind of makes me think a straight 7 saum with the ADG brass is a win win. If accuracy is your goal and ease of loading is appreciated I’d lean towards the saum.

If you like wild catting and playing with something new that not everyone has (as I do) then the SS will not disappoint.

 

[pinoykillaz]

I have one 7ss 26" coming next week..anyone here wants to share pet loads???
Ty in advanxe

 

[RampedRaptor]

Old Competition load:
300 Norma brass
BR2
180gr Hybrid
3.687 grams of RL23
High 2900s FPS

Will obtain 184gr/ADG load data hopefully next weekend.

 

[RampedRaptor]

Weather was terrible today for working up a load but I do have some velocities to report. I will try again tomorrow as long as the weather cooperates.

I always recommend finding seating depth first then finding your optimal charge but today I decided to ignore my own advice. I had hoped the 184s liked the same jam as the 180s but this proved to be incorrect. All groups were terrible, hovering around .35 moa or greater.

Load:
30" 1:8 brux
184gr berger
.006 jammed
CCI Br2
ADG brass, 1x fired
RL 23
Magnetospeed

Charge weights are to the .001 grams for me. However, I did the rough conversions to the tenth of a grain in this post for reader convenience.

56.4gr=2954 FPS
56.7gr=2971
57.0gr=2976
57.3gr=2986
57.6gr=2998

I also fired formed some new brass with 55.0gr for RL23 and it formed nicely as one would expect.

I know, nothing ground breaking but I'll continue to update this thread as I work with the Berger 184gr more.

 

[RampedRaptor]

Update:

Different barrel:
125 rounds down it before testing.
7SS
160 Freebore
32" Bartlein
1:8.7 5R

All loads:
COAL= 3.082~
0.010" in the lands
184gr Berger hybrids. Unsorted
ADG brass. Fired twice. Annealed every time. Neck turned
CCI BR2's



Fire forming load:

120gr Hornady Vmax
Jammed in the lands.
59.0gr RL23
3200ish FPS
No pressure signs. Sharp shoulders.

With a formed case you can get these V-max's easily to 3630 FPS with H4350.
DO NOT SHOOT AR500 steel at 100yds.




Velocity testing only.
2 rounds fired at each charge and averaged
Magnetospeed


H1000
62gr = 2975 FPS
62.5 = 2996
63 = 3006
63.5 = 3039
64.0 = 3059


H4350
52.5 = 2823
53 = 2834
53.5 = 2856
54 = 2877
54.5 = 2897

RL23
57.9 = 2989
58.2 = 2986
58.5 = 3002
58.8 = 3015
59.1 = 3026

No real pressure signs with H1000, max charge before compressing.

H4350 had a stiff bolt lift on one of the two rounds fired at 54.5.

The higher charges of RL23 resulted in a stiffer bolt lift. RL23 was a more narrow window because I've worked with it in the past.





Hope this helps someone in the future.

 

[ShootDots]

^^^^^^^Thank You for this report! It is appreciated..

 

[JPS338LM]

Update:

Different barrel:
125 rounds down it before testing.
7SS
150 Freebore
32" Bartlein
1:8.7 5R

All loads:
COAL= 3.082~
0.010" in the lands
184gr Berger hybrids. Unsorted
ADG brass. Fired twice. Annealed every time. Neck turned
CCI BR2's



Fire forming load:

120gr Hornady Vmax
Jammed in the lands.
59.0gr RL23
3200ish FPS
No pressure signs. Sharp shoulders.

With a formed case you can get these V-max's easily to 3630 FPS with H4350.
DO NOT SHOOT AR500 steel at 100yds.




Velocity testing only.
2 rounds fired at each charge and averaged
Magnetospeed


H1000
62gr = 2975 FPS
62.5 = 2996
63 = 3006
63.5 = 3039
64.0 = 3059


H4350
52.5 = 2823
53 = 2834
53.5 = 2856
54 = 2877
54.5 = 2897

RL23
57.9 = 2989
58.2 = 2986
58.5 = 3002
58.8 = 3015
59.1 = 3026

No real pressure signs with H1000, max charge before compressing.

H4350 had a stiff bolt lift on one of the two rounds fired at 54.5.

The higher charges of RL23 resulted in a stiffer bolt lift. RL23 was a more narrow window because I've worked with it in the past.

Hope this helps someone in the future.

Hi,
Busy putting together a 7ss for f open.

Would .220 freebore be better suited for the 184’s in single shot configuration?

Would also appreciate your further findings with H1000 as this is pretty much (and H4831SC) what we have available. No reloaded powder in our country.

Regards

 

[Winny94]

Just a quick chime in for the 7ss. Here are fireforming rounds 31-49 w/ a 162gr ELDM and a moderate charge of 4831. The bottom right shot was the first shot/cold bore (not sure i buy the idea of 'cold bore' being that different, i think its me just being reminded about fundamentals after the first shot). The top most shot I broke before settling in, and the other hole next to it was evidently just a bad shot or flyer. so 15/18 landed in a .56 center-to center group. May not be impressive to most on here (and may be downright bad to some), but for me, this cartridge is proving to be as accurate as any other ive fired. Got my 100 rounds down the tube (rounds 50-80 produced very similar results, and 81-100 were shot in 5 rounds groups that averaged out to .5 as well), 2x fired ADG brass, and ready to start to load dev now.

 

[RampedRaptor]

Hi,
Busy putting together a 7ss for f open.

Would .220 freebore be better suited for the 184’s in single shot configuration?

Would also appreciate your further findings with H1000 as this is pretty much (and H4831SC) what we have available. No reloaded powder in our country.

Regards

With regards to freebore. Kinda depends if you like jumping/jamming. I shoot almost entirely jammed so a 160 FB is okay. A 200 would be about perfect for me.

H4831sc is just ever so slightly slower than RL23 in my testing. You will most likely be a few FPS slower than if you used Rl23 but I have no doubt, you will find a superbly accurate load.

RL23 is actually probably a hair too fast but I’ve had such good luck with it I don’t plan on changing.

 

[ShootDots]

With regards to freebore. Kinda depends if you like jumping/jamming. I shoot almost entirely jammed so a 150 FB is okay. A 200 would be about perfect for me.

H4831sc is just ever so slightly slower in my testing. You will most likely be a few FPS slower but I have no doubt, you will find a superbly accurate load.

RL23 is actually probably a hair too fast but I’ve had such good luck with it I don’t plan on changing.

I just finished my 7 SS about 1 month ago. Testing H4350 proved it is TOO FAST , I found RL-23 a bit fast too, but it shot poorly in mine anyhow. H4831sc shot well but produced "unexplained vertical" (way too much) at 1000 yards. I finally tried H1000 out of desperation and found it to be very accurate with a W-I-D-E accuracy window, 6/10th of a grain, and velocity with the 184s is right at 2945-2954. I will shoot a match to see how this holds up towards the end of this month. But it sure works on paper!

 

[boltfluter]

Ben,

We need to see some of your small groups fired! Looking forward to the pics.

Paul

 

[ShootDots]

Ben,

We need to see some of your small groups fired! Looking forward to the pics.

Paul

Hello Paul! Myself, I can't post pics. I have a flip phone w/o a way to down load. My daughter comes over when I need to take pics of scopes or rifles etc.. But I can tell you that of the best loads @330 yards (300 meters) with H1000 were as follows: first load 60.7 had a straight horizontal load right at 1". It was exactly 1 bullet hole high. There was NO PAPER between each shot. Second group was 61.0 even and perfectly round at about 3/4". No paper between the shots, it was just a "small blob" of bullet holes. The third group, 61.3, was exactly like the second but right at 1". There was paper between the holes but it was pretty. So I chose 60.9grs to try out at a 500 yard match at Rio on the 4th Saturday this month. It is a tough range with very tricky winds. We shall see how it goes. NOTE: My daughter gets somewhat "pissed" at me for not getting a better phone! LOL!!!

 

[ShootDots]

From 60.7 to 61.3 there was only a 15f.p.s increase in velocity. From 61.0 to 61.3 was exactly 2945 to 2954!. I have never had a load with this wide of an accuracy window with that small of a spread in velocity! This should prove to be very interesting indeed! BUT like I said, we shall see how it shoots at a match! But what I see on paper and the chrono, it should be great! The 184s are seated 25 thousandths off and I have a 225 freebore that is now at about .240!

 

[JPS338LM]

Thank yous,

Shooting dots, please let us know how the load performed in the match.