280AI vs 7MM Rem Mag - 160gr Nosler Accubonds

[ChrisAU]

So I shoot the factory Nosler 160gr Accubond 280AI rounds in my Cooper M92 280AI. They shoot great, and have killed my only elk and a pile of whitetail deer with perfect performance.

Last summer when that load came out I was excited to try it out because while the factory 160gr Nosler Partition loads shot great, I had some issues at close range on our small deer with penciling if they didn’t catch a bone, which I’d rather it not anyway, that’s another topic.

When I got my hands on a few boxes I spent a day at the range. My Cooper has a 24” barrel plus a muzzle brake. I was surprised at the speeds I was getting. I shot 40 rounds that day from 100 to 400 yards and chrono’d every one. I got 3018-3041 FPS on every round, with most being 3025-3035. The box says 2950, which I know not to go by but I was surprised to see real world on the high side. I corrected the speed in my charts and voila, high hits at 300 and 400 came down a bit with the proper adjustments.

So, knowing that, I went shooting with a buddy this past weekend who wanted to try Federal Premium 160gr Accubond loads - in his 7mm Rem Mag, 24” barrel, no brake. I was surprised to see 2900 on the box, and we both shot at 300 yard with 1 MIL adjustment (not dialing to hit bull, just dialing to see the difference at 300 yards with the same adjustment with same POA) and my 280AI was almost 2” higher (we both were zeroed dead on at 100). That would seem to indicate that my chrono average of 3030 for my rifle and the Federal rating of 2900 for his are pretty close looking at the numbers.

Is that just a product of the powder Nosler uses or what? I haven’t googled anything yet, figured I’d consult the gurus here.

 

[Dcrafton]

Velocity: myths vs. facts: chronographing factory ammo. - Free Online Library

Free Online Library: Velocity: myths vs. facts: chronographing factory ammo. by "Guns Magazine"; Sports, sporting goods and toys industry Sport, sporting goods and toys industry

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[6mm Remington]

I would not be surprised at your velocity you were obtaining. I load 140 gr. Partitions for my 280AI and I get 3230 fps with them. 140 gr. Accubonds same powder and charge are going 3186 fps. That's from a custom Shilen match grade barrel 24" long.

We had 4 Remington 700 heavy barrel rifles and one Savage' all in 308 which were used as sniper rifles on our team. Shooting the same lot of ammunition which was 168 gr. boat-tail bullets, the chronograph speeds were extremely revealing. Barrels even of the same length and same make can vary so much. Chamber dimensions can vary, how smooth the barrel is, just a variety of things to take into account.

Shortest barrel was 22" and longest was 26" on the Savage. I'm recalling this from memory, but there was over a 200 fps difference between the fastest of the rifles/barrels and the slowest. The 22" barrel was not the slowest barrel shooting the same ammunition from the same exact lot. The 26" barrel on the Savage was also not the fastest. One of the 24" barreled rifles chronographed the fastest out of the 5 rifles all in 308 Winchester.

In looking at the my Nosler reloading book #7, it shows the 160 gr. Accubond that it can be loaded up in the 3040 fps range or so. Factory stuff is typically slower than what they state on the box, but again that test barrel is nothing like the barrel you shot your factory loads in. Maybe a little surprising that it was faster, but not really and that it's completely possible.

 

[Slugz]

Thats why I got a good Chronograph. Manufacturing tolerances these days are so big, data ranges so wide.....etc etc. Sound basics of reloading, knowing pressure signs and lastly data collection of reloads and factory ammo will tighten up the groups.

This is another good reason to keep a barrel log. Many little nuggets come out of having one.