AR COMP users need some advice, 28 grains too much fill

[Jakal]

I am starting to create my charge ladder using Hornady brass(already fire formed). I've learned in the past to dump a max charge to see how the case fill looks.

The issue I have is that 28 grains of AR COMP comes right to the base of the neck. At the depth that the 123 grn SST needs to be seated, the base of the bullet is about 1/8th of an inch below the shoulder and this is going to create a compressed load.

I had this problem with another Alliant powder. I was setting up for my 9mm and the charge listed in the Sierra guide came right to the mouth of the case, no way in hell was that going to happen. I called Sierra and asked them about the data and they stated that Alliant had changed their formula and it was taking up more volume.

I called Alliant and they stated that they did not change Unique in quite some time.

So what gives here? I think I will need to reduce the charge by about 2 grains so the powder level comes up to the shoulder. If normal min/max is 27-28 grains, then that would be a min of 25 and a max of 26.

Has anyone else ran across this with Alliant powders? IF you can dump a 28 grain load into Hornady brass, I would appreciate the feedback, because at this point it will be trial and error and that makes me a little nervous.

Lot number is ce0519 35094z012414; purchased May of 2014.

I have TAC that I use in my .223 and .308 and can switch too but bought 5 pounds of AR COMP specifically for this caliber.

Thanks in advanced.

[shooter545]

Search for Drifter's load data. He has done a bunch of work with that powder. Based on his and some others work I bought some and have loaded some but not done a lot of work with it yet. I think I was in the 27gr range with 123gr Lapuas.

[wheelguner]

Try using a drop tube type funnel like this one:

http://www.midwayusa.com/product/842036/rcbs-quick-change-powder-funnel-kit?cm_vc=ProductFinding

[Jakal]

I am using a RCBS Chargemaster to measure out the powder and then I drop it by hand into the case. Even after tapping the case, the best I can get this to settle down is right at the base of the neck. Really don't see how the bullet is going to be fully seated without it being forced back up due to case fill. I'll PM Drifter and see what advice he has.

[tackdriver]

I am thinking he said 28.0 grn under a 123 scenars as a 1k yd recipe. Don't quote me on that but I am very I treated to see what you come up with as I have a couple pounds of that to burn up as well.

[Drifter]

27.7gr of AR Comp is what I typically use with a 123gr bullet.

Haven't loaded any lately, but I think it is indeed a compressed load, which hasn't caused any issues for me.

[txgunner00]

I have found almost all my best loads for the Grendel have been at least a little compressed.

[COTNTOP]

Got my load from Drifter, bumped up to 28gr AR-comp and had no problems. Really good at extended range.

[Jakal]

So I started on the low side and loaded up 6 rounds only. Charge weights from 25.5 to 28 in 1/2 grain increments. Could hear slight crunching as I was seating the last two. Will shoot those as a test run, looking for pressure signs and failures. Will report back in a few days.

[Jakal]

I was able to shoot the 6 proofing rounds I had made up. 25.5 to 28 grains of AR Comp in 1/2 grain increments, Left to Right. I do see ejector/extractor marks on the 27.5 and 28 rounds. The 28 primer still as some roundness but is right on the ragged edge of being flat. I would have to say that 28 grains of AR Comp is max in my rifle. Definitely a compressed load. Will start my charge ladder at 26.5 and run it up to 28 in .3 grain increments. Now I just need some decent weather, so I can get them over the chrony and shoot for accuracy.

What do you guys think?

[Jakal]

Bump

[Michael]

DISCLAIMER = I haven't used AR Comp. Primers look OK to me - even 28g - similar to loads I have used with other powders. Put them on a chrony and determine your chamber pressure to be sure.