260 Remington AI Build

OK Folks. Im wanting to get into PRS style of shooting. I shot long range while I was in the Navy at Camp Perry back in the late 90s early 2000s with a 300 Win Mag. Won several Sec Nav Trophy Rifles. Now PRS sounds like fun so I built a 260 Remington AI with 30 degree shoulders. Using Peterson brass to fireform. Blue printed Remington SA with a PT&G one piece bolt. Krieger 1-7.5 barrel with a Remington Varmint contour. XLR Classis, Timney Trigger. It is topped with a Vortex Viper PST Gen II scope with 5x25x50 FFP. What I'm looking for is some recommended loads for this rifle. I'm looking at using Sierra 142 SMK HPBT bullets. The below picture is my new rig.

Ackley Improved is 40deg for 260 right?
Why would you go 30deg?

Mikecr said:

Ackley Improved is 40deg for 260 right?
Why would you go 30deg?

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I used a reamer print from a friend. It has .0080 free bore

30° also feeds a bit better/smoother than 40° shoulders.

If you are fire formed, look at .260 Rem load data, start about that halfway point and work up.

What powder are you intending to use? I would look at stability and accuracy over pure raw speed. H4350 would be/is my personal choice. I have used H4350 in about a dozen different 6.5CM, .260 Rem, and a 6.5SLR. RL16, RL26, Superformance might give better speeds however if that is the way you want to go.

I have run a 28" 1:8" heavy 6.5SLR for years and it is similar to .260AI 30°. I ran 142 SMKs a lot. Also, 140 Hybrids. From 2820 for my light target loads to 2940 for my hunting loads. I have up to 8 firings on some of my R-P brass. Some pockets are starting to get loose on my hunting loads though.
After 2800 rounds, the rifle barrel was done, so it got a total rework. New barrel, stock, scope. Shed 5 full pounds and 6" of barrel length down to 22". I am now running a 130 Berger Hybrid OTM. And this barrel LOVES them over H4350.

A good buddy is running a very similar combo, running 140 ELD's at 2950 with ~44gr of H4350. It's a friggin hammer on steel.

When you used a friend's reamer, you departed from common standards.
It's not an Ackley Improved cartridge, but a wildcat. How can anyone guess about the load without reviewing the reamer print and/or knowing the H20 capacity?

Mikecr said:

When you used a friend's reamer, you departed from common standards.
It's not an Ackley Improved cartridge, but a wildcat. How can anyone guess about the load without reviewing the reamer print and/or knowing the H20 capacity?

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Correct, a .260 Imp 30*. Not an AI. Great call.

What else is changed with that shoulder angle from standard 260?
Was neck-shoulder junction moved down, or body-shoulder junction moved up?
Neck length, case length, body size, body taper?

Without knowing this stuff, or simply it's fired H20 capacity, you could probably split the difference between 260 loads and 260AI loads and work up. H4350 or IMR4350 with ~140gr bullets.

I am satisfied with the velocity (2930 fps) and group consistency of H4831SC pushing 139 g Scenars in my 26-inch 8.5 twist heavy palma mated to a surgeon 591 action in a 260 AI.

I stand corrected on the AI. What I'm looking at is keeping the speed below 3000 fps. I have learned when speeds are above 3000 fps. Throat erosion happens faster. I usually set the barrel back once before it becomes a tent stake. I have had good dealing with Varget, H 4350, IMR 4350 and 4895. I am leaning toward the IMR 4350 with a 142 SMK, Fed 210 GM primer and Peterson Brass. I also have a BUNCH of L C M-852 brass in thought about down sizing and fireforming. That is a lot of work!

Why the 142 Sierra??
Its hard to beat the 147 ELD-M. That would be cooking out of the 260 30* imp

I run h4831sc in my ai (25" barrel) pushes a 140vld to 2850 with a moderate load. It had a nice wide node at 47.2-47.8gr, I ended up at 47.5. Fwiw I can run up to 48.8 before I see any signs of pressure. I am also seated long as I run a wyatt mag box and a bdl floor plate, gives me a bit more capacity as well. I wouldn't discount some slower powders from an improved case.
I can get a 147 just over 2900 with no pressure signs, but my rifle didnt like them as much.

What specific cartridge are you talking about LongBomber?

Mikecr said:

What specific cartridge are you talking about LongBomber?

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Mines a 260ai, 40deg shoulder.

I would think the op's improved with a 30deg would be somewhere between the regular 260 and 260ai. If the body is blown out straight it would be very close to the ai. I think you gain more seating bullets so they don't sit below the neck than the improved case, but its nice to have both.