12" GB Barrel and 129 ABLR Load Suggestions

[1075 tech]

I'm finally at a point I can try working up some loads for my 12" GB. I was able to obtain a few hundred 129 ABLRs for a great price.

Here is what I have to work with. Loads will be chrono'd with a Magnetospeed.

Brass: I have a variety to choose from. Once fired Hornady, Federal, PPU/Wolf. I also have new Lapua but this will be for hunting and I'd hate to lose that. I'm also considering pulling Wolf steel and using those cases.

Powder: I need temp stable. It will be 70's and 80's here during development but 20's and 30's during use. I have 8208 (pressure spikes understood), AR-Comp, Lvr, AA2495, 780 Supreme. I also have IMR 4895 and Varget but I don't think the velocity will be there with those.

Primers: CCI 41, CCI 450, WSR.

Looking for suggestions with these combo's.

[A5BLASTER]

Use the hornady brass, more case capacity.

Use the cci450 primer

Use the ar-comp are if possible pick up a pound of h4895.

Use cpd or ASC mags that way you can load past 2.260 coal if your chamber allows it. The longer you can load it and still feed from the mag the better it's going to work for you.

Hope this helps sir.

[Gtscotty]

^ This is what I'd do too. I've been using Starline cases, but I believe that H has a bit more capacity. I haven't tried the 129gr ABLRs, but AR-Comp and H4895 did well with 129gr ILs. I use Rem 7 1/2 for almost all of my small primer needs, but have had good luck with 450s as well.

[1075 tech]

It looks like I should be able to load out to close to 2.28. I'm limited to a 5 round mag for hunting here. My ASC that I dedicated to this NY fixed mag, top load, build measures out at 2.305. Using a Hornady modified case and gauge, I set one to 2.28 without touching the lands. If I'm measuring correctly, the 129 starts to jamb in the lands at 2.385. Does that sound right? Isn't that a huge jump? I'll load up a few dummies at 2.28 or maybe 2.275 and see if they'll feed reliably.

[A5BLASTER]

It looks like I should be able to load out to close to 2.28. I'm limited to a 5 round mag for hunting here. My ASC that I dedicated to this NY fixed mag, top load, build measures out at 2.305. Using a Hornady modified case and gauge, I set one to 2.28 without touching the lands. If I'm measuring correctly, the 129 starts to jamb in the lands at 2.385. Does that sound right? Isn't that a huge jump? I'll load up a few dummies at 2.28 or maybe 2.275 and see if they'll feed reliably.

No that jump sounds about correct.

It contacts at 2.380 and 2.387 in my short barrels as well.

2.280 should help get it going. I'm able to use 2.295 in my cpd and six8 mags.

[1075 tech]

Thanks A5. I wasn't sure how much room to leave in the mag. I'll play with a few to see how they feed under manual cycling.

[A5BLASTER]

Thanks A5. I wasn't sure how much room to leave in the mag. I'll play with a few to see how they feed under manual cycling.

Seeing as your mag set up is limited too 5 rounds, should beable too load perrty close too max allowable in the mag and it still feed.

If you can get it to feed at a coal of 2.295 that will be the same length as my handloads with this bullet.

My CZ=2.295
12 inch=2.290
12.5=2.295

[1075 tech]

2.295 works

[A5BLASTER]

2.295 works

That should work.

[1075 tech]

That should work.

What would you suggest as a starting load? Looking at some of the data in some of these threads, it looks like 26 -27gr ballpark.

[A5BLASTER]

[QUOTE=1075 tech;259459]What would you suggest as a starting load? Looking at some of the data in some of these threads, it looks like 26 -27gr ballpark.[/QUOTE

I would say 26.8 or 27 grains of ar-comp or h4895 would be a good place to start.

Have to double check my books but I think I started at 27 grains.

[1075 tech]

Thank you sir. What did you find as a max? Or where did you stop at. I'm thinking of loading 5 of several weights to see. I'll probably get one day here in a couple of weeks to get out to shoot. Probably .3 increments starting at 27

[A5BLASTER]

Never finished the ar-comp because the h4895 worked better in my rifles.

My 12 and 12.5 both hit max at 28.8 grains.