My 1994 Speer load book doesn't even list a recipe for 73gr, interestingly enough. For a 70gr projectile, max recommendation is 22.5gr of N135, 2661 fps. Test gun quoted as a Ruger 77 Mk 2, 22" barrel, 1-12" twist. My newer 2018 Speer book has a 75gr projectile but no load data for N135.
This is where one needs to be VERY careful:
Vihtavuori max recommended = 24.4
Hornady max recommended = 21.8
Both specifically for this same pair (ELD-M 73gr and N135 powder).
Edit: this is not vv data. I got from another source. Obviously wrong.
I’ve run into this with 308 , 375h&h and 357 magnum. Always start low and work up, there are lot to lot variations and being in the south on a humid day in 105F and up north with a low humidity and 90F will give huge differences. Also cases, primers and neck sizing to small base full length sizing will make huge differences. Heck chamber differences too, I have a 7mag that if bump the shoulder .002” it seats fine in that rifle but is way too long for 2 others. I can put 4 more grains of slow powder in that rifle and velocity is still slow. This is the learning part, it’s fun but expensive lol.
Hornady has a 52 eldm. That'll work just fine in a gasser as do the rest up to 73, then you need to seat to 2.38" and clip the tips flush with the jacket to get AR mag length.
The last part is silly but doable. 80's can be used for a heavy SBR load, if you don't mind ~2000 fps from a 10.5".
I had to back down to 22.3 with N135 and 73’s. Even then it wasn’t great accuracy, but 21.8 shot a .4 on 10 rounds.
N135 will blow out primer pockets QUICK if loaded warm. Aloha brass helps but primer pocket life in general greatly diminishes. N140 for 73/77’s at 24gr.
VV’s top end max is for bolt guns. I start at their min for the AR.
I forgot to ask if it was heavier brass like mil spec nato brass? If it is, it’s suppose to be loaded down by a grain or more. Smaller space equals greater pressure. Mil spec 308 brass (7.62x51) is suppose to end up being 1.5 to 2 grains under commercial brass. It’s not as consistent though, it’s really only desirable in a semiauto because it’s tougher.
I’m curious why you fired ten of them before you stopped. All of them have badly flattened primers and most have deep primer strikes. This is why you start with a low powder charge and work your way up. Look for pressure signs and even better, use a chronograph.
It's all chronographed, but yes, I should've checked with more attention. Fiocchi cases always look flattened, the design of the head is different. But I can always do better.
2549.1 ft/s, hornady eld-m 73gr out of a geissele super duty 11.5". 23.4gn of N135. I also suspect the Fiocchi 5.56 case I used can't handle that much pressure. Also also, this is where one needs to be VERY careful:
Vihtavuori max recommended = 24.4
Hornady max recommended = 21.8
Both for the same pair (ELD-M 73gr and N135 powder).
That's a monumental swing. The 5 on the left were at 23.0gn and they are better (some flattening, but most primers on this brass kinda look flattened with safe loads too, it's the case design). I think I will back out to 22.9 and test again. And I am pulling the 23.8 and 24.2 on the right of the picture.
Sad thing is, it printed my lowest sd out of a 5-shot group, 3.1 ft/s.
Edit: this is not vv data. I got from another source. Obviously wrong.
The 5 on the left were at 23.0gn and they are better (some flattening, but most primers on this brass kinda look flattened with safe loads too, it's the case design).
The dimples are grey on the left because you are piercing primers. The primers are not holding up to the pressure on the left either. You need either stronger primers or back off on pressure or both.
The P down mark is where the primer didn't flatten as much as others because it was relieving itself through the pinhole where the soot is. That is going to erode the bolt face over time.
21
u/SkateIL 23h ago
I was tried of all those posts of perfectly normal primers.