Trying to figure out a new load. 123 SST and AR-comp

[CXRs]

So after finding disappointing amounts of drop with Benchmark, I tried loading up a similar load with AR-comp, and the accuracy was good at first with lower charges, but as I worked up towards 28gr it spread out to about an inch larger grouping.

Something I noticed while loading the rounds was that I was getting some very minor compression at 27gr, and enough to noticeably effect the seating depth at 27.5gr. I didn't adjust my seating die, but I did end up with about .005" extra length on the OAL. Could that depth be causing my accuracy problems? Or should I start looking at a different powder?

[CXRs]

I almost forgot to mention, using the Benchmark I was able to pull extremely good groups(<.3-.4"), and I really want to retain that kind of accuracy but with the higher velocity from q slower powder.
Thank you for any advice!

[1Shot]

Any change in a load can effect accuracy. I tried factory Hornady 123 SST ammo and handloads using IMR 8208, CFE 223, H 335 and IMR 4895 using different primers, COAL, and I just could not get the 123 SST to shoot under 1 1/2" out of both of my rifles. One has a BCA and the other Oden Works barrels. Both will shoot sub MOA with 120 Sierra PH and Speer GD with IMR 8208.

[CXRs]

I have some IMR4895, but I figured I would work on the AR-comp first. My initial thoughts are that the bullet being pushed out a bit is causing it to meet the lands a bit too soon and degrading accuracy. I'm concerned about pushing it in further with my seating die, but I think I will try to tonight and test them the next time I can get to the range.

[Wafavre2]

Just My 2cents, follow the details of the load data and work up in charge weight. Compressed loads should have that warning if in a loading Manuel. Load data off the internet may or may not. If your compressing a powder load it should be a warning sign and you may want to select a different powder.

[A5BLASTER]

Just My 2cents, follow the details of the load data and work up in charge weight. Compressed loads should have that warning if in a loading Manuel. Load data off the internet may or may not. If your compressing a powder load it should be a warning sign and you may want to select a different powder.

Nothing wrong are unsafe about a compressed load. Just have too watch it closely.

OP. What did your ladder look like? What's the chrongraph telling you?

[CXRs]

I dont have a chronograph, but I'm saving up for one. There were no major pressure signs on the brass and the primers were fine. My main goal was to find an accurate load and work off that.

[CXRs]

I figured out part of my issue was the crimp on the bullets. I made a couple loads without any crimp and a hair more seating depth, and they came in much closer to an inch. I had a couple different types of brass in the load(star line and hornady) so I'm thinking I'll try to load up a few from identically prepped brass.

Also did a few loads with CFE-223, and had similar results, but at seemingly greater velocities(based off POI) I'm hunting down a good load for game and want the best balance of speed and accuracy I can find.

[Mitdr774]

Sort your brass by brand. I have Hornady and Starline brass and I do NOT run the same load in both brands of brass. The case capacity is not the same between them.

[Popeye212]

I figured out part of my issue was the crimp on the bullets. I made a couple loads without any crimp and a hair more seating depth, and they came in much closer to an inch. I had a couple different types of brass in the load(star line and hornady) so I'm thinking I'll try to load up a few from identically prepped brass.

Also did a few loads with CFE-223, and had similar results, but at seemingly greater velocities(based off POI) I'm hunting down a good load for game and want the best balance of speed and accuracy I can find.

I have yet to crimp a Grendel. Changing seating depth can yield good results but readjust powder also. Deeper seating can yield higher pressure conversely longer depth you may find you may need to add a touch more. Seems like that bullet liked it around 2.245