An old Texas Whitetail taken at 491 yards with the 25-7PRC and 134 Hornady ELD-M.

Velocity testing with a 22″ barrel

As I write this, it’s been exactly since we released our initial test data on the 25-7PRC! We chambered a bunch of barrels for this new wildcat in the past 12 months, and a recurring theme across many of those builds was a 22″ barrel length. This has been a trend across many calibers this year, as suppressors have truly become a mainstream item for hunters and shooters, and overall portability of rifles for backpacking hunts continues to drive build design criteria. In between customer builds, we were able to spin up a 22″ 1-7.5 twist carbon fiber Bartlein barrel blank for some testing, to see how much velocity our quarter bore hot rod would loose. To put it succinctly, the 25-7PRC is still a hot rod even in a short barrel. 

Test Rifle Specifications

• Caprock Medium Length Action #CTX0142

• WTO SwitchLug

• Bartlein 7.5T #13 Rem. Varmint CFW barrel, 22″ length

• MDT HNT26 folding chassis

• TriggerTech Diamond trigger

• Vortex Razor LHT 4.5-22×50 FFP MRAD scope

• Hawkins Precision Ultralight Tactical Rings

• AB Suppressor Raptor 8 silencer with 5/8-24TPI flush mount

• Total Build weight: 9lbs 4oz

With the HNT26 chassis, a field ready rifle with optic and suppressor under 10 lbs is easily achievable.

133 Grain Berger Elite Hunter, New ADG Brass, 2.510″ CBTO, Rem 9 1/2M primer

69.8gr Vihtavuori N570, CCI 34 primer:

3213FPS/7.8SD. This load produced a case web OD of .5317″, easy bolt lift, and excellent accuracy. In a fairly variable full value wind, the backpacker cannon stacked 3 shots into a nice 2″ cluster at 475 yards. We also shot this charge weight with the 134gr Hornady ELD-M, which produced a .208″ three shot group at 100 yards and MV of 3208FPS/12.7SD.  On 1x Fired brass, accuracy remained stellar and velocity slightly increased to 3239FPS/9.0SD over 6 shots. This charge weight produced 3350FPS in the 24″ test barrel.

62.0gr Vihtavuori N560, Rem 9 1/2M primer:

3107FPS/6.2SD, .362″ group at 100 yards. This load was well established from the original 24″ test barrel, and was used as a break-in load on this shorter carbon barrel. This load produces 3204 FPS in the longer barrel.

The 128 grain Hammer Hunter!

Hammer Bullets have achieved almost cult like status with many hunters for their accuracy, knock-down power, and a famous ‘smoke trail’ that they often produce when their trajectory is watched over longer distances. While we do our best to not be Kool-aid drinkers for any product, we have developed loads for multiple customer builds using Hammer Hunter bullets and have found them to be very accurate and consistent. Long-range shooters will wish for higher BC’s(and Hammer has now produced a tipped version to address this), but the design has been well proven in the hunting world and the good reputation is earned. I happened to have a box of .257 cal 128gr Hammer Hunters on the test room shelf, and couldn’t resist loading some up for this project. With N570, 69.8grs was found to be our established maximum. Bolt lift remained easy on all shots, but we saw case web growth above .5325″ and the beginnings of a very slight ejector mark. Accuracy was outstanding, with bughole groups shot back to back at 69.1 and 69.8. Muzzle velocities were 3250FPS/14.9SD and 3278FPS/14.0SD, respectively. We stretched the 69.1gr load out to 720 yards, and comfortably stayed under .5 MOA of vertical dispersion.

NOTE: Hammer recommends a minimum 1-7″ twist rate for the 128gr Hunter bullet, and if you are building a barrel purposefully for this bullet we recommend you follow their guidelines. We ran stability calculations for our altitude and atmosphere and came up with a 1.45 stability factor in our 1-7.5″ twist barrel, and decided to try it at our own risk. I would not run this load at sea level, but here on the Llano Estacado or out in the western states I believe it would do just fine. Hammer’s published G7 BC of .244 lined up fairly well in our very limited testing.

Caprock .25-7PRC with 22″ Proof Research barrel, WTO Mk2ST brake, and Manners Pro Hunter stock. Just over 6lbs before optics.

Summary

  As expected, the 25-7PRC continues to be incredibly accurate across a wide variety of rifle build styles and barrel types. We found a velocity loss of about 100 FPS from a 24″ to a 22″ barrel, which is not entirely unexpected for a high volume, relatively overbore cartridge. That velocity gap may shrink somewhat given that the 22″ barrel we tested has less than 100 rounds through it at time of writing, and our original test barrel was much more seasoned. A major standout to be mentioned is the quality of the Atlas Development Group 7mm PRC brass. We used Hornady, Redding, and Forster 7mm PRC full length sizing dies to resize all of the cases fired with established maximum loads (all with web diameters stretched to at least .532″ on the first firing). Regardless of the sizing die used, all of these pieces of brass were able to be loaded back to our established max charges, fired again, and then sized and fired for a 3rd firing without hard bolt lift or the ‘clicking’ problem that plagued early 6.5 PRC reloaders. In the near future, we will conduct a failure test on several pieces of brass to see just how many firings they can take before loss of primer pocket tension.