When Philip Sharpe and Richard Hart developed the 7x61 S&H cartridge in 1953, they reportedly were doing so with IMR 4350 powder in mind--one of two powders at the time with an appropriate burn rate. However, today there are many new powders that offer some gains with the 7x61 S&H over what was previously achieved with IMR 4350.
I’ve been experimenting lately with QuickLoad for a number of cartridges I load, including the 7x61 S&H, and have determined maximum loads with IMR 4350. In all my test trials with QuickLoad and the 7x61 S&H, I’ve used the following: (a) a 24” barrel, (b) cases headstamped “Norma Super 7x61” (not the earlier lesser-capacity 7x61 cases), and (c) a COAL of 3.35”, a length that works well in my Schultz & Larsen M68DL with its 3.40” magazine. And I’ve looked at two bullets: (a) the Nosler 150-gr Partition bullet and (b) the Nosler 160-gr. Partition. With IMR 4350, QuickLoad indicates a maximum charge producing 2950 fps for the 150-gr. bullet and 2875 fps with the 160-gr. bullet. I should note that the other suitable powder available in 1953, H4831, produced velocities within 25 fps of IMR 4350.
So I set about testing 12 modern powders via QuickLoad that fall within the appropriate burn-rate range with both bullets to find maximum loads for each powder with these bullets. I've defined a maximum load as one that (a) generated 61,500 PSI (Piezo CIP) pressure or less and (b) didn’t result in more than 105% load density (QuickLoad computes this), the latter to avoid the need for excessive powder compression. This is the same standard I applied with IMR 4350.
Edit. I should add that all the QuickLoad calculations are based on a rifle with no free-bore. I've used a .030" jump into the lands in all calculations. Velocities will change with bullets seated more deeply than that, although the velocity differences will tend to be relatively small. I don't expect that the comparative maximum velocities--among the various powders--will change with varying seating depths. In other words, if Powder X produces 50 fps more than Powder Y with .030" bullet jump, then I believe we can expect that Powder X will produce greater velocity than Powder Y with a different seating depth.
Here’s what I found:
With the 150-gr Partition, the following seven powders produced the highest-velocities:
Vihtavuori N570: a muzzle velocity of 3140 fps,
Re26, Re25, Re33, and Vihtavuori N560: a MV of about 3100 fps,
IMR 7828, Accurate MAGPRO: a MV of about 3050 fps.
With the 160-gr Partition, the following eight powders produced the highest-velocities:
Vihtavuori N570 and Re33: a MV of about 3050 fps,
Re26 and Re25: a MV of about 3000 fps,
Vihtavuori N560, IMR 7828, Accurate MAGPRO, and H1000: a MV of about 2975 fps.
As noted, these are for a 24” barrel. For a 26” barrel (found on many Schultz & Larsen rifles), add about 50 fps to these figures. So, with a 26” barrel, close to 3200 fps is possible with the 150-gr bullet and about 3100 fps with the 160-gr. bullet. These were the modern powders that did best in these trials with the 7x61 S&H. As can be seen, close to 200 fps can be gained with these powders over what’s possible with IMR 4350. Keep in mind that these results are based on the QuickLoad algorithms and are not the result of actual chronographed velocities. They represent what QuickLoad predicts that you should be able to get with the powders and bullets mentioned.
I’m reluctant to list the actual maximum powder charges that produced these velocities (something we’re strongly cautioned against doing on internet gun forums—liability issues, I assume), but, given that there is next-to-no published data for the cartridge with modern powders, perhaps knowing what can be achieved with the 7x61 S&H (and Norma Super 7x61 cases) and these bullets will prove helpful and motivate some to work up loads using one or more of these powders. Of course, as always, one should start low (well below maximum) and increase the powder charge in small increments, checking for any signs of high pressure. I think if I had to choose just one modern powder now for this cartridge, it would be Vihtavuori N570, which at maximum levels has a load density of 102%-104% requiring only slight compression and which is available these days in Canada. In another thread, or perhaps later in this one, I’ll discuss some things I’ve discovered regarding load development with this cartridge. If anyone has worked up some loads with their 7x61 S&H and modern powders and obtained chronographed results, it would be great if they would share this information. Finally, I’m assuming here (perhaps wrongly) that there is still some interest in the 7x61 S&H, and I’d like to work towards developing some real-world loading data and techniques for this cartridge.
I’ve been experimenting lately with QuickLoad for a number of cartridges I load, including the 7x61 S&H, and have determined maximum loads with IMR 4350. In all my test trials with QuickLoad and the 7x61 S&H, I’ve used the following: (a) a 24” barrel, (b) cases headstamped “Norma Super 7x61” (not the earlier lesser-capacity 7x61 cases), and (c) a COAL of 3.35”, a length that works well in my Schultz & Larsen M68DL with its 3.40” magazine. And I’ve looked at two bullets: (a) the Nosler 150-gr Partition bullet and (b) the Nosler 160-gr. Partition. With IMR 4350, QuickLoad indicates a maximum charge producing 2950 fps for the 150-gr. bullet and 2875 fps with the 160-gr. bullet. I should note that the other suitable powder available in 1953, H4831, produced velocities within 25 fps of IMR 4350.
So I set about testing 12 modern powders via QuickLoad that fall within the appropriate burn-rate range with both bullets to find maximum loads for each powder with these bullets. I've defined a maximum load as one that (a) generated 61,500 PSI (Piezo CIP) pressure or less and (b) didn’t result in more than 105% load density (QuickLoad computes this), the latter to avoid the need for excessive powder compression. This is the same standard I applied with IMR 4350.
Edit. I should add that all the QuickLoad calculations are based on a rifle with no free-bore. I've used a .030" jump into the lands in all calculations. Velocities will change with bullets seated more deeply than that, although the velocity differences will tend to be relatively small. I don't expect that the comparative maximum velocities--among the various powders--will change with varying seating depths. In other words, if Powder X produces 50 fps more than Powder Y with .030" bullet jump, then I believe we can expect that Powder X will produce greater velocity than Powder Y with a different seating depth.
Here’s what I found:
With the 150-gr Partition, the following seven powders produced the highest-velocities:
Vihtavuori N570: a muzzle velocity of 3140 fps,
Re26, Re25, Re33, and Vihtavuori N560: a MV of about 3100 fps,
IMR 7828, Accurate MAGPRO: a MV of about 3050 fps.
With the 160-gr Partition, the following eight powders produced the highest-velocities:
Vihtavuori N570 and Re33: a MV of about 3050 fps,
Re26 and Re25: a MV of about 3000 fps,
Vihtavuori N560, IMR 7828, Accurate MAGPRO, and H1000: a MV of about 2975 fps.
As noted, these are for a 24” barrel. For a 26” barrel (found on many Schultz & Larsen rifles), add about 50 fps to these figures. So, with a 26” barrel, close to 3200 fps is possible with the 150-gr bullet and about 3100 fps with the 160-gr. bullet. These were the modern powders that did best in these trials with the 7x61 S&H. As can be seen, close to 200 fps can be gained with these powders over what’s possible with IMR 4350. Keep in mind that these results are based on the QuickLoad algorithms and are not the result of actual chronographed velocities. They represent what QuickLoad predicts that you should be able to get with the powders and bullets mentioned.
I’m reluctant to list the actual maximum powder charges that produced these velocities (something we’re strongly cautioned against doing on internet gun forums—liability issues, I assume), but, given that there is next-to-no published data for the cartridge with modern powders, perhaps knowing what can be achieved with the 7x61 S&H (and Norma Super 7x61 cases) and these bullets will prove helpful and motivate some to work up loads using one or more of these powders. Of course, as always, one should start low (well below maximum) and increase the powder charge in small increments, checking for any signs of high pressure. I think if I had to choose just one modern powder now for this cartridge, it would be Vihtavuori N570, which at maximum levels has a load density of 102%-104% requiring only slight compression and which is available these days in Canada. In another thread, or perhaps later in this one, I’ll discuss some things I’ve discovered regarding load development with this cartridge. If anyone has worked up some loads with their 7x61 S&H and modern powders and obtained chronographed results, it would be great if they would share this information. Finally, I’m assuming here (perhaps wrongly) that there is still some interest in the 7x61 S&H, and I’d like to work towards developing some real-world loading data and techniques for this cartridge.
Last edited:
