Developing Loads for the .25-6.5PRC

Sheltowee

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I think my addiction to the quarterbore has been well-established on this forum. Started with a sweetheart little .257 Roberts Ackley Improved built on a CZ 550 FS, then this spring had a 25-7PRC built. Shortly after the 25-7 came home, I set about gathering components for a shorter barrel .25-6.5PRC intended for whitetail stand hunting and mountain hunting out here in the West. The components for this build were:
  • Tikka T3X action;
  • 20" Carbon Six barrel, Sendero contour, 1:7.5 twist;
  • Pure Precision Altitude stock;
  • Mountain Tactical knurled bolt knob;
  • Mountain Tactical bottom metal;
  • Hells Canyon Armory Tikka mags;
  • Sportsmatch 30mm, medium height scope rings;
  • Trijicon CredoHX 2.5-15x42 scope; and
  • DeadAir Nomad 30 with .264 endcap installed.
Richie at High Tech Customs in Colorado Springs cut the chamber and built the rifle for me. He does incredible work-- this is the fourth rifle he's built for me and I complain to him that his rifles are so boringly accurate that load development is no fun. I'd strongly recommend him to anyone wanting a well-built custom rifle.

Finished product:
IMG_4414.jpeg

It handles like a wand without the suppressor attached but is a touch on the muzzle-heavy side with the Nomad on board. I might eventually talk myself into putting a titanium suppressor on it but the sound suppression of the Nomad has been hard to beat on this and other rifles.

This is going to be purely a hunting rifle, so I've focused load development on Hammer HHTs. The 127gr. HHTs shoot wonderfully out of the 25-7PRC's 24-inch tube at 3327fps. I was aiming for 3000fps from the .25-6.5 and its 20-inch barrel. Being a true wildcat, there is no real published load data for the .25-6.5 (other than Hammer, which according to Steve are more estimates using load software rather than tested and verified loads). Hammer's data did not list any powders that really interested me but, fortunately, the case capacity of the .25-6.5 is near identical to that of the venerable .25-06. I settled on H4831sc as I strongly lean toward temp stability, even if I am leaving some potential speed on the table that could be attainable using VV powders. I chose ADG 6.5PRC brass after positive results in my 25-7 and my usual CCI BR-2 primers.

I ran the brass through a 25WSSM neck-sizing die for the initial neckdown using Imperial Sizing Die Wax. I then ran the brass through full-length Hornady 6.5 PRC Custom Grade dies with a .287 bushing installed. I then cleaned the necked down brass using my Hornady Ultrasonic case cleaner, then chamfered and deburred each case mouth. I did not initially trim to length but will have to before I load this brass for a third time. I loaded a 50-round ladder starting with a moderate charge of H4831sc and worked my way up. Results were... fine, but not exactly what I was aiming for. Averages, ES and SDs are for 10-shots.

25-6.5 PRC, 127gr. HHT, H4831sc, ADG brass, 2.830" COAL, 2.283" CBOL
Average Velocity(fps)Extreme Spread(fps)Standard Deviation(fps)Best 5-shot/3-shot group
Load 127094621--
Load 22735258.9--
Load 3Chrono Failed------
Load 427925114.9.805/.159
Load 528256015.6.755/332

The first three loads were so slow that I didn't both shooting for accuracy. I was nowhere near pressure, so loaded a second 40-round ladder in order to pour more gas on the HHTs. Hammers tend to shoot best for me toward the top of a cartridge's pressure window. The second batch were only run through the full-length sizing die with the bushing. It did not give me the neck tension that I really wanted. The bullets were being held in the neck but a handful slipped a bit as I installed the HHT's polymer tip. I've since ordered and installed a .284 neck bushing, which I think will give more consistent neck tension. Regardless, today's results were encouraging:

25-6.5 PRC, 127gr. HHT, H4831sc, ADG brass, 2.830" COAL, 2.283" CBOL
Average Velocity(fps)Extreme Spread(fps)Standard Deviation(fps)Best 5-shot/3-shot group
Load 628874514.11.064"/.468"
Load 729376220.6.573"/.342"
Load 82977289.2.487"/.284"
Load 929933611.9.810"/.389"

I think the light neck tension wasn't doing my any favors as far as accuracy but it is hard to be too upset with a sub half-MOA 5-shot group. Load 8 ought to do just fine for me but I'll be interested to see if I can shrink ES, SD and group size with the .284 neck bushing.

IMG_4506.jpeg

Just for S&Gs, I also threw six 95gr. HHTs that I use in my .257Ackley on top of a ladder test of H4350 just to see if I hit pressure. This is actually Hammer's recommended load development practice (rather than tediously shooting groups with 50-round batches of $2 bullets): load 2-3 rounds at increasing charge weights until you hit pressure, then back off a touch. I barely touched pressure signs (very slightly flattened primer, shiny but faint ring on the case head) but hit a smooth 3502fps. I'm going to load 10 or 15 to establish average velocity, SD and ES, then probably take the 95s with me to laser some Alabama whitetails. The 127s will be perfect for longer range western hunting in a stiff wind.

Anyone else messed with a .25-6.5PRC? I'm fairly happy with the H4831sc velocity but, if the SD and ES don't shrink after going to a tighter bushing, what temp-stable powders would you recommend I try? Hammers tend to like faster burning powders than the normal profile for a cartridge, so H4350 is a possibility. Still fairly new to the wildcat game and developing my own loads. Any other thoughts or feedback?

**Please work up your own load with this cartridge. My data may not work for your rifle and vice versa. Use at your own risk***
 
what temp-stable powders would you recommend I try? Hammers tend to like faster burning powders than the normal profile for a cartridge, so H4350 is a possibility. Still fairly new to the wildcat game and developing my own loads. Any other thoughts or feedback?
N555 is a very good H4350 substitute. It’s got the magic of RL26 but for lighter bullets. I use it in my 260ai. I am able to get PRC speeds from the 127g LRX out of the smaller case.
 

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