7 mm SHERMAN SHORTMAG vs 7 SAUM

[browning442]

23 is faster burn rate.... I didn't chrono my fire forming loads. 62.3 grains of RL26 is getting me 3051 with the 180 Bergers.

 

[PapaB0415]

Thanks guys!

 

[elkaholic]

Browning, how much faster is the RL26 than the RL23?

RL26 runs about 70' faster than RL23 in mine with approx the same pressure.
It takes about 3.5 grains more of 26.
Mine maxes out at 63 grains of 23 for 3065 and 66.5 grains of 26 for 3135'. This is with a 175 EH and 26" barrel.
(7 Max, not SS)

 

[RH300UM]

Ok Rich,
I'm going to rock the boat. We are friends. I respect what you have accomplished. I'm not trying to bash or hate.
Please explain to me, and others, if the 7 ss and other Sherman cartridges are sold as "more efficient case designs" how can a 7 max get 3150 fps on 66.5 grains ofRL26 with a 175 berger and a 7 saum ( mine and others) can do 3050 fps on 61.5 fps with a 180 berger ( 6th reload on same brass and load)?
I'm not trying to bash or raise drama I'm just trying to learn and expand my knowledge.
Forgot to add. My 7 saum IS a short action. COAL is 2.963 and a 26 inch barrel

 

[elkaholic]

Ok Rich,
I'm going to rock the boat. We are friends. I respect what you have accomplished. I'm not trying to bash or hate.
Please explain to me, and others, if the 7 ss and other Sherman cartridges are sold as "more efficient case designs" how can a 7 max get 3150 fps on 66.5 grains ofRL26 with a 175 berger and a 7 saum ( mine and others) can do 3050 fps on 61.5 fps with a 180 berger ( 6th reload on same brass and load)?
I'm not trying to bash or raise drama I'm just trying to learn and expand my knowledge.
Forgot to add. My 7 saum IS a short action. COAL is 2.963 and a 26 inch barrel

The Max is NOT as efficient as the SS. The SS uses about the same charge as the saum to get 3050' but it does it at 2.90"
My Max has a Rock barrel and seems to take more of a charge to pressure up than most barrels Ive used. In fact, it only holds 3-3.5 more grains than the SS but takes at least that much more powder to get the velocity?? Go figure!
I cant speak for the other Max chamberings, but thats what my rock does.
My SS has a 26" Krieger.
It will do it with different barrels too. No hand picked, and std throating.
Ive run mine up to 3080' but brass life is short at that speed!

 

[Rardoin]

First post. New 7SS Mag shooter. I decided to built an F-class rig around the long/heavy for caliber .284 offerings from Hornady (190 A-tip) and Berger (190 LRH). The latest LR F-class trend is going in the direction of .30 cal 215gr bullets using the .300 WSM cartridge; I don't want the recoil/percussion of that beast over 8 days of shooting and 350+ rounds. In discussions at our national last year a friend and I were discussing the 7 SAUM wildcat he was shooting that involved a set-back shoulder/body junction, longer neck, 40deg shoulder. He said it was easy to tune and the longer neck gave a little longer barrel accuracy life depending on powder. I had been struggling with keeping Berger 184's consistently in tune for 600/1000yd comps and found the case inadequate for the Berger 190's to perform to their best potential. John suggested not trying to reinvent the wheel and, if I wanted to pursue his cartridge, I should go with the 7 SS since it was nearly identical to his reamer design. The big advantage would be readily available reamers/brass/dies. I took his advice and chambered up a 7 SS mag using a rental reamer and throating it out with a throating reamer to accept a 190 A-tip with at least .030" of the base of the bearing surface above the neck/shoulder junction and still be at least 0.050 off the lands to give room for long jumps if that is what the load likes. The freebore ended up being a little over .300". I decided upon fireforming with the Berger 190 LRH's at 0.040" off lands/ 57.0gr H1000 based upon a fellow competitors use of 57.5gr H1000/ 184 Berger Hybrid in the same case. I shot 58/60 in under a .5" group at 100yds with the other two shots opening it up to .7"...not bad at all I figured, particularly since I had done essentially no charge development. I shot 5 charges with a 190 A-tip to get a velocity bracket then loaded up for a seat depth test from 0.010"-0.070" off the lands using a charge that was running right at 2700fps and shot it at 100yds. I repeated a fine seat depth test from 0.035-0.045" in 0.005" intervals and found 0.037" the sweet spot at 965yds. I then loaded a coarse charge weight test from 2600 fps to sweep through 2800 fps in .5gr increments using a 0.040" seat depth based on the prior test and shot it at 965yds. The charge of 60.0gr looks like the middle of a node at 2690 fps. I loaded up a fine charge test in .2gr intervals from 59.7-60.3gr. I had a brain fart and confused the first 3 shots of each group by grabbing from the wrong row so I ended up with 3 shot groups for the 4 test charges instead of 6 shots as planned. Being I had a 1000yd match the next day and no time to test further I chose 60.2gr and loaded up 90rds. Over the complete match I had all of my 89 shots (60 record/29 sighters) at or under 10" of vertical which is pas bon but the windage on the A-tips was nothing short of phenomenal. I won the match with a 591-20X which is the second highest score at this very difficult range (Long Range Alley near Shreveport, LA). The second and third place guns were .300 WSM's running 215 Bergers around 2850 fps. The waterline of the WSM's were at/just over 5", which is excellent and where one strives to be for F-class and I think I can close the gap since I have only scratched the surface on load development. If this combination of bullet and very forgiving cartridge to tune pans out like I think it will I will have a rig that will have a ballistic advantage over the most common .300 WSM loads in wind hold as well as reduce recoil/percussion fatigue.

Robin

BTW... This set-up is with an 8.25 Bartlein 5-R 30" barrel. The BC of the 190 A-tip is accurate if not a bit conservative. My truing based on 1000yd and 865yd dial-ups under prevailing atmospheric conditions/velocity suggested a G7 closer to .43 vs published .422.

edited seating depth for the Atip to -0.037"....the 190 hybrid like -0.043"

 

[elkaholic]

First post. New 7SS Mag shooter. I decided to built an F-class rig around the long/heavy for caliber .284 offerings from Hornady (190 A-tip) and Berger (190 LRH). The latest LR F-class trend is going in the direction of .30 cal 215gr bullets using the .300 WSM cartridge; I don't want the recoil/percussion of that beast over 8 days of shooting and 350+ rounds. In discussions at our national last year a friend and I were discussing the 7 SAUM wildcat he was shooting that involved a set-back shoulder/body junction, longer neck, 40deg shoulder. He said it was easy to tune and the longer neck gave a little longer barrel accuracy life depending on powder. I had been struggling with keeping Berger 184's consistently in tune for 600/1000yd comps and found the case inadequate for the Berger 190's to perform to their best potential. John suggested not trying to reinvent the wheel and, if I wanted to pursue his cartridge, I should go with the 7 SS since it was nearly identical to his reamer design. The big advantage would be readily available reamers/brass/dies. I took his advice and chambered up a 7 SS mag using a rental reamer and throating it out with a throating reamer to accept a 190 A-tip with at least .030" of the base of the bearing surface above the neck/shoulder junction and still be at least 0.050 off the lands to give room for long jumps if that is what the load likes. The freebore ended up being a little over .300". I decided upon fireforming with the Berger 190 LRH's at 0.040" off lands/ 57.0gr H1000 based upon a fellow competitors use of 57.5gr H1000/ 184 Berger Hybrid in the same case. I shot 58/60 in under a .5" group at 100yds with the other two shots opening it up to .7"...not bad at all I figured, particularly since I had done essentially no charge development. I shot 5 charges with a 190 A-tip to get a velocity bracket then loaded up for a seat depth test from 0.010"-0.070" off the lands using a charge that was running right at 2700fps and shot it at 100yds. I repeated a fine seat depth test from 0.035-0.045" in 0.005" intervals and found 0.043" the sweet spot at 965yds. I then loaded a coarse charge weight test from 2600 fps to sweep through 2800 fps in .5gr increments using a 0.040" seat depth based on the prior test and shot it at 965yds. The charge of 60.0gr looks like the middle of a node at 2690 fps. I loaded up a fine charge test in .2gr intervals from 59.7-60.3gr. I had a brain fart and confused the first 3 shots of each group by grabbing from the wrong row so I ended up with 3 shot groups for the 4 test charges instead of 6 shots as planned. Being I had a 1000yd match the next day and no time to test further I chose 60.2gr and loaded up 90rds. Over the complete match I had all of my 89 shots (60 record/29 sighters) at or under 10" of vertical which is pas bon but the windage on the A-tips was nothing short of phenomenal. I won the match with a 591-20X which is the second highest score at this very difficult range (Long Range Alley near Shreveport, LA). The second and third place guns were .300 WSM's running 215 Bergers around 2850 fps. The waterline of the WSM's were at/just over 5", which is excellent and where one strives to be for F-class and I think I can close the gap since I have only scratched the surface on load development. If this combination of bullet and very forgiving cartridge to tune pans out like I think it will I will have a rig that will have a ballistic advantage over the most common .300 WSM loads in wind hold as well as reduce recoil/percussion fatigue.

Robin

BTW... This set-up is with an 8.25 Bartlein 5-R 30" barrel. The BC of the 190 A-tip is accurate if not a bit conservative. My truing based on 1000yd and 865yd dial-ups under prevailing atmospheric conditions/velocity suggested a G7 closer to .43 vs published .422.

Great job Robin!
Congrats on a big win. It can only get better since your barrel is barely broken in.

 

[dok7mm]

First post. New 7SS Mag shooter. I decided to built an F-class rig around the long/heavy for caliber .284 offerings from Hornady (190 A-tip) and Berger (190 LRH). The latest LR F-class trend is going in the direction of .30 cal 215gr bullets using the .300 WSM cartridge; I don't want the recoil/percussion of that beast over 8 days of shooting and 350+ rounds. In discussions at our national last year a friend and I were discussing the 7 SAUM wildcat he was shooting that involved a set-back shoulder/body junction, longer neck, 40deg shoulder. He said it was easy to tune and the longer neck gave a little longer barrel accuracy life depending on powder. I had been struggling with keeping Berger 184's consistently in tune for 600/1000yd comps and found the case inadequate for the Berger 190's to perform to their best potential. John suggested not trying to reinvent the wheel and, if I wanted to pursue his cartridge, I should go with the 7 SS since it was nearly identical to his reamer design. The big advantage would be readily available reamers/brass/dies. I took his advice and chambered up a 7 SS mag using a rental reamer and throating it out with a throating reamer to accept a 190 A-tip with at least .030" of the base of the bearing surface above the neck/shoulder junction and still be at least 0.050 off the lands to give room for long jumps if that is what the load likes. The freebore ended up being a little over .300". I decided upon fireforming with the Berger 190 LRH's at 0.040" off lands/ 57.0gr H1000 based upon a fellow competitors use of 57.5gr H1000/ 184 Berger Hybrid in the same case. I shot 58/60 in under a .5" group at 100yds with the other two shots opening it up to .7"...not bad at all I figured, particularly since I had done essentially no charge development. I shot 5 charges with a 190 A-tip to get a velocity bracket then loaded up for a seat depth test from 0.010"-0.070" off the lands using a charge that was running right at 2700fps and shot it at 100yds. I repeated a fine seat depth test from 0.035-0.045" in 0.005" intervals and found 0.043" the sweet spot at 965yds. I then loaded a coarse charge weight test from 2600 fps to sweep through 2800 fps in .5gr increments using a 0.040" seat depth based on the prior test and shot it at 965yds. The charge of 60.0gr looks like the middle of a node at 2690 fps. I loaded up a fine charge test in .2gr intervals from 59.7-60.3gr. I had a brain fart and confused the first 3 shots of each group by grabbing from the wrong row so I ended up with 3 shot groups for the 4 test charges instead of 6 shots as planned. Being I had a 1000yd match the next day and no time to test further I chose 60.2gr and loaded up 90rds. Over the complete match I had all of my 89 shots (60 record/29 sighters) at or under 10" of vertical which is pas bon but the windage on the A-tips was nothing short of phenomenal. I won the match with a 591-20X which is the second highest score at this very difficult range (Long Range Alley near Shreveport, LA). The second and third place guns were .300 WSM's running 215 Bergers around 2850 fps. The waterline of the WSM's were at/just over 5", which is excellent and where one strives to be for F-class and I think I can close the gap since I have only scratched the surface on load development. If this combination of bullet and very forgiving cartridge to tune pans out like I think it will I will have a rig that will have a ballistic advantage over the most common .300 WSM loads in wind hold as well as reduce recoil/percussion fatigue.

Robin

BTW... This set-up is with an 8.25 Bartlein 5-R 30" barrel. The BC of the 190 A-tip is accurate if not a bit conservative. My truing based on 1000yd and 865yd dial-ups under prevailing atmospheric conditions/velocity suggested a G7 closer to .43 vs published .422.

Welcome and thank you for your informative review. It's great to see knowledgeable shooters show up here.

 

[Rardoin]

Welcome and thank you for your informative review. It's great to see knowledgeable shooters show up here.

There would be those that debate the term knowledgeable in regard to my contributions but I try.. I will keep this thread abreast of my load work with the 7SS and the heavies. Again, I am excited as I am only in the very early stages of load development and already seeing very good signs.

I also edited the seating depth for the Atip as I incorrectly put the Berger depth in the write-up.

 

[elkaholic]

Welcome and thank you for your informative review. It's great to see knowledgeable shooters show up here.

Robin is being a bit modest here but he beat out two recent national champs to win the match and had his new barrel not sped up, he very likely would have set the all time course record!

 

[Rardoin]

Rich, just a plug for this forum but I hold the record for a 20 shot/1000yd match at this range- 200-10X -I shot with a cartridge I learned about here. I was using the 6.5 x55 BJAI with 142gr Precision Ballistics VLD's at 2940fps. Bob designed a great AI version of the venerable Swede cartridge.

 

[Rardoin]

I sat down to load up another charge test to attempt to improve on the unacceptable vertical dispersion I had at the 1000yd match. I realized two major screw ups in my match loads. Due to having my neck expander die still set for the .284 I was only sizing the upper 1/2 of the neck leaving the lower 1/2 0.006" too tight. I suspected something funky with my seating pressures but was out of time to investigate. Another screw up was looking at my 190 Berger LRH cbto number and using it on the A tips (.030" closer to the lands than ideal). It's a wonder I didn't place 10/10! Retested today with prepped cases and proper seating depths but only went out to 300yds because of the breeze. Still very encouraging and picked up a little velocity with the proper neck tension.
190 A-tips at 2770:

190 Berger LRH fire forming at 2670 fps:

I still need to test fine charges on each side of these nodes and revisit finer seating depth increments. The 7 SS is certainly holding its reputation as being and easy cartridge to tune. I'll shoot a 600yd match this weekend and we'll see what happens. I'm very encouraged.

 

[elkaholic]

I sat down to load up another charge test to attempt to improve on the unacceptable vertical dispersion I had at the 1000yd match. I realized two major screw ups in my match loads. Due to having my neck expander die still set for the .284 I was only sizing the upper 1/2 of the neck leaving the lower 1/2 0.006" too tight. I suspected something funky with my seating pressures but was out of time to investigate. Another screw up was looking at my 190 Berger LRH cbto number and using it on the A tips (.030" closer to the lands than ideal). It's a wonder I didn't place 10/10! Retested today with prepped cases and proper seating depths but only went out to 300yds because of the breeze. Still very encouraging and picked up a little velocity with the proper neck tension.
190 A-tips at 2770:


View attachment 205547
190 Berger LRH fire forming at 2670 fps:

View attachment 205550


I still need to test fine charges on each side of these nodes and revisit finer seating depth increments. The 7 SS is certainly holding its reputation as being and easy cartridge to tune. I'll shoot a 600yd match this weekend and we'll see what happens. I'm very encouraged.

Looking forward to a big win

 

[Rardoin]

Thanks Rich.