7 SAUM initial charge weight.

I'm after some input about a starting charge weight for a 7 SAUM that was recently put together.

It's been chambered to allow for seating projectiles further out of the case.
When seating 162 eldm's -0.030" off the jam point, the COAL is 3.045" and the BTO is 2.263".

I've got some ADI 2217 & 2213sc.
I'm looking to start with the 2217, and I'm just not sure what charge weight to start off at, given that the case volume is larger due to seating out projectiles as far as I am.
Barrel length is 20".

Greetings @Tacitus,
I would just use the Hodgdon start loads of 64 grains of AR2217 and 56.5 grains of AR2213SC and chronograph them to see how they compare with the Hodgdons velocities. You will lose around 120 fps for the shorter barrel. Your LOA is only about 3mm longer than I measured in my SAUM so the change in velocity will be minimal. Once you have your velocities you can make an informed estimate of where to start with your load development. You will likely top out at around 2,750 to 2,780 fps at standard pressures.
GPM.

Gidday, mines reamed for 175-180 projectiles and I’m running the 162s as long as possible with start of boat tail at neck to shoulder junction. Worked up in 1 grain increments from 65-67 grains 2217.
67gr (book max) reasonably snuck but not too bad. Zero issues with pressure and speed seems to line up with most people’s results.

Quote:

---

Originally Posted by grandpamac

Greetings @Tacitus,
I would just use the Hodgdon start loads of 64 grains of AR2217 and 56.5 grains of AR2213SC and chronograph them to see how they compare with the Hodgdons velocities. You will lose around 120 fps for the shorter barrel. Your LOA is only about 3mm longer than I measured in my SAUM so the change in velocity will be minimal. Once you have your velocities you can make an informed estimate of where to start with your load development. You will likely top out at around 2,750 to 2,780 fps at standard pressures.
GPM.

---

Thanks for the reply, Mac.
Fired some of the loads today, and the average velocity has been decent.
What has concerned me a bit is the ES & SD's aren't very good, and I'm not exactly sure as to why that is.

Powder charge is definitely consistent, primers are Fed GM210M's seated to the same depth (around 0.002" crush), necks were mandreled with dry neck lube and bullet seating depth has been consistent.

Perhaps the powder charge is low given the increased case volume, leading to an inconsistent burn?
Probably something else I'm overlooking.
I'll need to mess around a bit to see where the issue lies, but I'm happy with the avg velocity.

As it's a new barrel I'm not trying to do any super precise load development to perfect a load, but it'd be nice to at least get the ES & SD's down.

2217 is very bulky. I doubt you could get enough in to go over pressure. Im running 65g with 180g ELDM. This is a compressed load for me at 2.960” OAL. Theres plenty of data showing the large rifle primer gives better ES and SD than magnum with slightly lower velocity in the 7SAUM. I’d suggest trying that.
Edit; sorry I thought you were running magnum primers. 210 are standard iirc.

What kind of SD over how many shots

Didn't get too much time time today, so I couldn't shoot as much as I would have liked.
I actually ended up going with 65gr of 2217 in the end.

Braked
Rounds: 10
Avg: 2810.1 fps
ES: 36.8 fps
SD: 12 fps

Suppressed
Rounds: 10
Avg: 2818.5 fps
ES: 30.5 fps
SD: 10.1 fps

Results were measured using a Garmin Xero C1 Pro Chronograph.
The numbers aren't horrible, but I'd like to get them down a bit, especially since this isn't a very large sample size to go off of, so they'd likely worsen once more shots are taken into consideration.

An SD of 10-12 is pretty good. SD doesn't necessarily increase with more shots but hovers up and down around the true value.

Quote:

---

Originally Posted by gimp

An SD of 10-12 is pretty good. SD doesn't necessarily increase with more shots but hovers up and down around the true value.

---

I'd ideally like to get it further down, if at all possible.
I'm not the most unhappy with the SD, more the ES.
I've got another cartridge that I loaded the other day where the SD was 10.5, but the ES was 41.3 (over 23 shots).
I'll need to try a few different things out.

What do you think the "ES" is telling you that the SD doesn't?

https://www.nzhuntingandshooting.co....ead-es-111291/