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260 Ackley Improved Load data and velocity information

Cedarcreek

I am looking at a 260 AI project, I am having a hard time finding load data to determine what the velocity advantages are over the 260 remington.

I will be shooting a Shilen barrel, 27" long with a 1-8 twist.

I Plan on trying 142 SMK's, 123 SMK's, 139 Scenar and 123 Scenar in that order.

Any info would be appreciated.
 
Search for 260 Ackley on this forum, there's quite a bit comes up, but as far as I can see, I'm not sure it is worth all the bother. I've had std 260 Remingtons since '99 and I've read a bit on both the 30 degree and 40 degree improved options, but the benefits appear to be marginal.

Have fun. JCS
 
I loved my 260AI, won several relays and matches with it (have since sold due to medical issues). Typical vel for its sweet spot load was 2930FPS w/ H4831SC and 139gr Lapua. Very accurate. I could get higher velocities w/ RL17 but in my set up it wasnt as accurate and flyers increased for some reason.
Fireforming was a pain, but once you do it, the cases never need trimmed w/ the 40deg shoulder and straight case walls. I fireformed using the COW method.
Love the round. Mine did what a 6.5x284 does w/ less powder, and hopefully more barrel life.
 
I am working with my new 260AI rifle also. The velocity I'm getting is not up there with what Terry Cross reported. So far I've been able to reach 2900fps using 48.5grs of H4831sc,210M, norma .243 cases (weighs 3.0grs more than RP260) (neck turned,with donut removed)and the 142smk. However the temperature has been an avg of 47° and I'm hoping by the time it gets to 85° or so the velocity will increase to 2925 or so. This is a blueprinted rem 700 action , Kreiger 8.5T, 30"long barrel. I love the accuracy and the small increase in velocity. Right now I have 270 rounds down the tube.
pdog2225
 
My velocites were only that high w/ the Lapua 139's. The load it liked w/ SMK 142's were 2887fps.
I had a 28" Shilen Sel. Match on mine. I had it long throated for the 140's. I sent 2 dummy rounds with my order to Shilen. I was fortunate that the load it liked best w/ the Lapua's was 2930 ish fps. It wasn't quite there till it broke in though.
Once I added a good rear rest and a better scope- Nightforce 12-42x so I could aim more precisely at 1000yds I went from about the middle of the pack w/ the group of guys I shot with to the upper tier- sometimes winning.
I had 2 neck surgeries and the prone position w/ anything was brutal. I ended up switching to a 6brx right at 21lbs and that has helped neck issue. I have found the 6brx to be a little more accurate but the 260AI will shoot inside of it in the wind. The 260AI is a great round! I will build another one some day. The rem. brass wasn't that great and really needed to be sorted. I had good success w/ Win 7-08 brass necked down and fireformed. The Lapua 308 brass necked down didn't quite give the velocities of the Win.
 
Here's some results from my Rem action & 26" Krieger bbl 260AI. They are not in any special order.
140 SST - 47.1 gr Rel 22 = 2801
- 47.6 gr. Rel 22 = 2836
140 A max - 47.6 gr Rel 22 = 2842
140 Sierra - 47.9 gr. Rel 22 = 2949
129 SST 49.0 gr H 4831SC = 2996
129 SST 49.0 Rel. 22 = 2969
140 Sierra 45.8 gr. Hunter = 2911
140 Berger 48.5 gr. 4831SC = 2892

That's enough. I have literally a full book of test results and now about 960 rds. through the barrel.

LOSER...Mine is not very accurate with anything and I have tried most everything. Two other friends also have the same caliber and each of them is disappointed. To put it in perspective I'm still hoping to get 1/2 moa groups and have essentially given up. The junk has been sitting in my safe the last 6 months essentially untouched. If I get motivated again it will be motivation with a new barrel but doubt I would do 260 AI again.

Hope you have better results.
 
You should be able to reach a little over 3000fps (or close to it) with the .260AI and 140grain-class bullets safely and without too much trouble. I run mine at 3020fps, although I have 30" barrel. Take a look at RL-17. RL-19 or 22 will be too slow. On mine, accuracy improved *greatly* once I reached the node at 3020fps.
 
The .260 Ackley is one of my favorite calibers. It is the ultimate combination of lethality, long range capability and efficiency in my opinion. The last few I have built have been running between 43-44.5gr of H4350 with 140gr Bergers right around the 2950 fps mark with half moa or better accuracy. I have used Peterson, Lapua, Norma and Starline brass all have performed very well. I am running Starline brass in my wifes rifle and I have been very pleasantly surprised with the quality and performance we have been getting with the cost.
 
I too am a fan of the 260AI due to the ease of finding accuracy with H-4350 and H-4831. I recently had ODCR (WSMNUT) build me a hunting custom 700 and a BR custom 40X and fell for the caliber like a rock. I have not sit down at my bench with either one of the rifles yet and went away without feeling good about the accuracy of both of them. I shoot the 700 from a Harris BR bipod and rear bag while the BR actually does get to lay on a G E front rest and rear bag as well. I have Peterson, Lapua, Nosler, & Starline brass and the Berger 140 gr L R Target and Nosler A B & B T s are my go to bullets with groups @ 1/4 MOA most of the time however both rifles shoot very well with a few other bullets I've tried.
 
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