It doesn't have the capacity of the 28. I think it's down 6-9 grains, 10-12 grains in a straight 7-300 if I remember right. I looked at these pretty hard a few years ago. I think it's really close to the ideal 7mm though, the 7mm LRM was really close as well but no one made good brass for it.
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7-300 win mag AI
- Thread starter RockZ
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tomcat818
Well-Known Member
I looked up H2O case capacities for the both 83.2 gr with a 190gr seated at 3.330" COAL for 300WM and 88.7 with a 185gr seated at 3.340" for the 28 N. I call that a 4gr difference given the .308 vs .284 bullet diameter and the .284 being seated .010 longer. The OP said he got an extra 3gr capacity with the improved case so that puts it at around 1gr difference.
I did have a thought after posting my question and the answer is the 28 Nosler was SAAMI approved in early 2015 and rifles hit the market later that year. So when the OP was doing this wildcat there was only the 7 STW and maybe one other operating at this performance level.
I did have a thought after posting my question and the answer is the 28 Nosler was SAAMI approved in early 2015 and rifles hit the market later that year. So when the OP was doing this wildcat there was only the 7 STW and maybe one other operating at this performance level.
That's why I love the 7STW
ADG makes 7LRM now through gunwerks. I think a 7/300prc is around 93-94gr powder. 10-11 gr less than 28N. If I was after a fast 7mm, 28N with 225-250fb, use Retumbo or N568, I know 3100 is very doable with 180s from a 26". My 7lrn will run 180hyb at 3100 with N570 from a 24". Why do through the work of improving a belted case, that's gonna be prone to sizing issues above the belt. There will be a 3-4 step process for proper sizing using a Willis collet die, then a FL die. Just too much a headache in my opinion. The 7stw was replaced by 28N, it does the same thing performance wise maybe a bit faster, but modern case design, easy sizing, quality dies and brass available, oh and you don't need a 4" mag box to run the heavies out on the neck where they are supposed to be. Just my 2¢, moving on.......
Great info, I will look into a 7LRM again now that I know there is good brass, no way I was touching it with Hornady brass. It seems like just about perfect for a 7mm to me. I have (2) 28N and both are 26", 175/180's at 3100 is easy, very easy. Retumbo, 568, 570, RL26 and RL33 all get there in my rifles. Both mine load longer than 3.6" though, never messed with one at 3.34" and no idea why anyone would handicap it by doing so. My belted magnum experience is primarily 300WM and I haven't ever had issues with the belt or sizing, pushing it hard enough to open up primer pockets in 4 loadings, I think stretching the shoulder forward on the first fire form is the key but I have been wrong before. Having had no issues with it I thought the 7-300 made sense, and having hundreds of extra 300WM brass makes me think about it even harder. I wouldn't mind having another few hundred rounds of barrel life over the 28's.
The 7-300 is something I would really like to do.
I know that I could get close to STW speed but the availability of brass makes it a very good choice
I have a couple 7 rougue reamers( 7/300 aI 37° shoulder. I make my own dies for the reamer design. Shoot 190 atips high 3100s with great results. Pressured out around 3270 but accuracy was awesome lower down. 180 eld's I was over 3300 before pressure but that's a barrel burner. I love the 7/300AI chambering.
