.280AI Kimber Montana 84L

jakfrost

jakfrost

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Just finished my first round of experimenting with a new caliber for me, the .280AI. I only have one powder ( so far...) to use and thus the trial and error period was fairly short...
Using H4831sc and Federal Match Primers I tried the 3 loads given in the Nosler book for the 140gr. Accubonds in new Nosler brass. The 'middle' load, 60.5 gave the results shown below. Both the 58.5 ( Nosler indicated this was the 'most accurate' load, for them anyway...), and 62.5 loads were considerably less consistent. Next time I get out I'll try the same load at the longer ranges, and also like to try the 120 and 160gr projectiles.

I was seating these at the Nosler spec of 3.330", which 'just' fit into the Kimber blind magazine...anyone have a length they like better? Not sure how much of a 'jump' the Accubonds tolerate...
 
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IMHO, keeping the COL short enough so the cartridge will cycle through your magazine without hanging up more important than any advantage you might get from seating out to the lands if your magazine is too short to allow it. Seating out to the lands is primarily a way for target shooters to uniform bullet pull weight, so if you choose bullets with cannelures, like the 140 or 150 gr Barnes TTSX, and crimp, you will achieve the same effect without creating a feeding issue. Lots of people say that crimping is not worth the trouble except when recoil might drive a bullet deeper into the case neck or when a tubular magazine is used, but I think it makes my ammo just a bit better. To get the best results though it must be done correctly, which means crimping should be done as a separate step from bullet seating, and in some cases its best to leave the seating die loose so that it can be properly adjusted for each cartridge to allow for variations in neck length. With the loaded cartridge in the shell holder, raise the ram to the top of its travel, you can then crimp in one of two ways; you can turn the die down till you feel contact with the case neck, lower the ram slightly, and turn the die in about an eighth of a turn then raise the ram to crimp the cartridge, or you can just turn the die down on the cartridge till refusal. In the latter case, moderation is the key to success, and its a trial and error thing to discover how far to turn in the die for the best results with that brand of case and that particular style of bullet. I use both methods, and both can provide uniform results.

I think you've found your 140 gr load, and it would seem to me that there is no advantage to further load development with H-4831. You might find though that you can better performance slightly by switching to a slightly faster powder such as R-19 or H100V. A pal of mine was having difficulty getting his .280 Remington to shoot well, so I gave him a bit of H-100V to try and using 168 gr Bergers and 160 gr Lapua Naturalis, he's never looked back. YMMV, but it might be worth a look.
 
Boomer said:
IMHO, keeping the COL short enough so the cartridge will cycle through your magazine without hanging up more important than any advantage you might get from seating out to the lands if your magazine is too short to allow it. Seating out to the lands is primarily a way for target shooters to uniform bullet pull weight, so if you choose bullets with cannelures, like the 140 or 150 gr Barnes TTSX, and crimp, you will achieve the same effect without creating a feeding issue. Lots of people say that crimping is not worth the trouble except when recoil might drive a bullet deeper into the case neck or when a tubular magazine is used, but I think it makes my ammo just a bit better. To get the best results though it must be done correctly, which means crimping should be done as a separate step from bullet seating, and in some cases its best to leave the seating die loose so that it can be properly adjusted for each cartridge to allow for variations in neck length. With the loaded cartridge in the shell holder, raise the ram to the top of its travel, you can then crimp in one of two ways; you can turn the die down till you feel contact with the case neck, lower the ram slightly, and turn the die in about an eighth of a turn then raise the ram to crimp the cartridge, or you can just turn the die down on the cartridge till refusal. In the latter case, moderation is the key to success, and its a trial and error thing to discover how far to turn in the die for the best results with that brand of case and that particular style of bullet. I use both methods, and both can provide uniform results.

I think you've found your 140 gr load, and it would seem to me that there is no advantage to further load development with H-4831. You might find though that you can better performance slightly by switching to a slightly faster powder such as R-19 or H100V. A pal of mine was having difficulty getting his .280 Remington to shoot well, so I gave him a bit of H-100V to try and using 168 gr Bergers and 160 gr Lapua Naturalis, he's never looked back. YMMV, but it might be worth a look.
Click to expand...

WOW, great reply, thanks for all the good information, I hadn't considered using a cannelure bullet but since I'll be able to visit a Bass Pro Shop while in Toronto mid-week, I should be able to pick up some Barnes TTSX and give them a try. They might even have a 'crimping die' for the 280AI...? I assume that is what is needed to put the correct 'roll' crimp on the case mouth? Or do you just use the regular seating die as you described.

My shopping list is growing, LOL.

Jim
 
The crimping feature in your seating die should work perfectly. You could pick up a Lee factory crimp die if you prefer, that is if they make one for the .280 AI. They are relatively inexpensive, work pretty well, and they are one of the few Lee products I'll endorse.
 
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