11-27-2022, 04:33 PM
It was a good day at the range yesterday. All testing was completed and I still had time to ring some steal and print a 5 shot group at 600 yards with my normal loads using 112 gr Matchburners over 27.1 gr of Win748 powder. The results were strong enough for RL15.5 that it will definitely warrant more thorough testing to see how accurate I can make it in my rifle. Anyways, I’ll get to the good part, the data! To save typing I’m just going to provide the best performers as follows based on three shot groups at a mild 52 degrees:
Hornady 6ARC brass/BR4 Primers
27.1 gr = Avg 2445 fps, ES = 11, SD = 3.5
27.4 gr = 2469 fps, 19, 5
27.6 gr = 2496 fps, 19, 5.5
27.8 gr = 2505 fps, 16, 5
28 gr = 2522 fps, 18, 5
28.2 gr = 2544 fps, 13, 4
Starline 6.5 Grend. brass resized and Winchester 41 primers
27.1 gr = Avg 2460 fps, ES = 18, SD = 5
27.2 gr = 2475 fps, 22, 6
27.8 gr = 2518 fps, 13, 3
28 gr = 2537 fps, 16, 4
28.2 gr = 2555 fps, 17, 4.5
The groups were shot at 300 yards and seemed to back up the numbers above. My best group was with the Starline brass and 27.8 grains. It hammered out a .24 MOA group at 300 yards. It seems like it likes the 27.8-28.2 range and all of those groups were around .5-.75 MOA. This should be a very useful powder if more testing keeps backing up this data.
The next range trip will be doing 5 shot groups as well as putting Win 748 head to head with it. It’s not unusual for me to get .5 MOA accuracy using 27.1 grains and the Barnes bullets. I’m really excited for the potential of RL15.5 seeing that it appears to be offering some accurate loads that are also about 50 fps faster than W748 and did I mention TEMPERATURE STABLE! At this point it’s all coming down to ES and SD’s and I think I’ll be settling down on one of these two powders.
In the prior post of mine above I stated that the 28.2 gr would most definitely be at or over max. I’m going to walk that back slightly. With no official load data for 15.5 yet it’s really anybodies guess as to where the max truly is but here’s what changed my mind. Based off of the load data at the bottom of the page in this link https://www.handloadermagazine.com/6mm-arc where it has a max charge for Reloader 15 of 27.5 with 110 gr A Tips as well as published Lyman data that I was provided at my local reloading store saying max charge for RL15 is 28.2 using 107 gr bullets. Surely if you can use 27.5-28.2 of RL15 than the slower burning 15.5 should be safe in those ranges as well.
I should mention that when working up the reported loads I wanted to see how much 15.5 would simply fit in the case. It’s a very bulky stick powder which is it’s downside for this tiny cartridge. I couldn’t get much more than 29 gr in before it topped off the opening. I’m going to push a load up to 28.4-.6 and see what happens. They’ll be getting heavily compressed at that point but NONE of the rounds tested so far have shown high pressure signs.
Hornady 6ARC brass/BR4 Primers
27.1 gr = Avg 2445 fps, ES = 11, SD = 3.5
27.4 gr = 2469 fps, 19, 5
27.6 gr = 2496 fps, 19, 5.5
27.8 gr = 2505 fps, 16, 5
28 gr = 2522 fps, 18, 5
28.2 gr = 2544 fps, 13, 4
Starline 6.5 Grend. brass resized and Winchester 41 primers
27.1 gr = Avg 2460 fps, ES = 18, SD = 5
27.2 gr = 2475 fps, 22, 6
27.8 gr = 2518 fps, 13, 3
28 gr = 2537 fps, 16, 4
28.2 gr = 2555 fps, 17, 4.5
The groups were shot at 300 yards and seemed to back up the numbers above. My best group was with the Starline brass and 27.8 grains. It hammered out a .24 MOA group at 300 yards. It seems like it likes the 27.8-28.2 range and all of those groups were around .5-.75 MOA. This should be a very useful powder if more testing keeps backing up this data.
The next range trip will be doing 5 shot groups as well as putting Win 748 head to head with it. It’s not unusual for me to get .5 MOA accuracy using 27.1 grains and the Barnes bullets. I’m really excited for the potential of RL15.5 seeing that it appears to be offering some accurate loads that are also about 50 fps faster than W748 and did I mention TEMPERATURE STABLE! At this point it’s all coming down to ES and SD’s and I think I’ll be settling down on one of these two powders.
In the prior post of mine above I stated that the 28.2 gr would most definitely be at or over max. I’m going to walk that back slightly. With no official load data for 15.5 yet it’s really anybodies guess as to where the max truly is but here’s what changed my mind. Based off of the load data at the bottom of the page in this link https://www.handloadermagazine.com/6mm-arc where it has a max charge for Reloader 15 of 27.5 with 110 gr A Tips as well as published Lyman data that I was provided at my local reloading store saying max charge for RL15 is 28.2 using 107 gr bullets. Surely if you can use 27.5-28.2 of RL15 than the slower burning 15.5 should be safe in those ranges as well.
I should mention that when working up the reported loads I wanted to see how much 15.5 would simply fit in the case. It’s a very bulky stick powder which is it’s downside for this tiny cartridge. I couldn’t get much more than 29 gr in before it topped off the opening. I’m going to push a load up to 28.4-.6 and see what happens. They’ll be getting heavily compressed at that point but NONE of the rounds tested so far have shown high pressure signs.