Aiae 260 with Lapua 260 brass, 140 Amax, and H4350

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So, Santa (me) was nice to me this year. Picked up an almost new ATACR from another member here, then jumped on a new AI AE floder in 260 with the 26" barrel. Got lucky and found a couple of pounds of H4350 and Lapua 260 brass and currently waiting on the brown truck to bring my wilson seater and 140 Amaxs. While I wait here impatiently, I am wondering if anyone has a good starting point for me to begin with on my load development. I have read a lot of others loads and think I have a good idea where to start with the powder (as always starting low and working up especially with the Lapua brass) but not too sure about seating the Amaxs. Have yall noticed any tendencies in the AI chambers with the Amaxs (jumped or jammed)? Any suggestions would be appreciated.

 

[Gray]

42 gr H4350 with 140 seated .010" off the lands with a CCI BR2 or Federal GMM Primer, great place to start. I usually see my 1st signs of pressure at 43 grains. You could start at 41 and work your way up, but 42gr has always shot well in my rifles as well as my buddies who shoot 260 with Lapua Brass.

 

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Thanks Gray. I'll give that a shot.

 

[Barney88PDC]

Not sure on the AMAX but a 139 Scenar 0.010" off with Lapua Brass and a CCI BR2, if 42.0 - 42.5 grains of H4350 don't shoot start looking for a problem. For Rem brass increase load by 0.4 - 0.6 grains.

 

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Ever have Lapua brass with such a tight neck that you couldn't hardly seat a bullet in? I actually broka a few teeth off my arbor press seating the first bullet. I think there might have been something wrong with the press but still. I ended up pushing a bullet almost through the neck then pulling it to 25 pcs. Then neck sized, primed and loaded. Just really odd. Gonna have to give Sinclair a call tomorrow about the press.

 

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Well, I got to shoot some today. Everything shot pretty good. Got it on paper then moved back to about 250 yards. Shot from 41.5 to 43.5 grains. Only pressure signs were very slightly cratered primers at 43.5 but nothing else. I just seated them as far out as the mag would allow. At 34.5 I only had about 1/2" of vertical, so I am going to try to work around that. Across all loads I only had about 3" of vertical. Still getting use to the rifle, so hopefully I can tighten up my part.

 

[steelringer]

Im pretty sure i ran 43.6 in my 4350 .260 and 140 amax. But its in a slightly shorter chamber than an ai. 2880 fps and gets plenty of firings.

 

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I thought I would be seeing more pressure than I was so I only loaded to the 43.5. The group had the least amount of vertical there too. I am going to play with the seating depth some.

 

[Known]

I have an AI Arctic Warfare and did an OCW workup with my .260. Used Lapua brass, CCI BR2, 139 Scenars, and H4350. Accuracy nodes were at 43.2 and 42gr H4350. 43.2 gr worked well for 200 rounds and then started piercing primers. I backed off to 42gr and went 125 rounds until 1 pierced primer. I suspect I have some carbon/copper buildup that is spiking pressures because 42gr is far from being a hot load.

AI rifles are known for piercing primers so you're probably not going to get the same velocities as others who have bushed firing pins in their Remmy 700s.