A modern .257 to make the most of today’s medium length actions.

Genesis

As all of you who follow the goings on at WTO already know, we’ve been intrigued by .25 caliber rifles for a long time. In the very early days of this business, we built an unmistakable pair of .257 Weatherby Magnum antelope rifles for two brothers that became long time customers and great friends. These rifles were lights out accurate, relatively mild on recoil, and flat out fast. The owners put them to great use on some trophy speed goats, and through the years we’ve continued to love not only the .257 Weatherby, but other great cartridges such as the .257 Roberts, .25-06(both the classic and it’s Ackley Improved sibling), .25 Creedmoor, and our very own .25 SAW. These later two, as well as a host of other quarter bore wildcats, were really brought about thanks to some major advancements in bullet design for this bore size spawned by Blackjack Bullets. What they did with with 131gr ACE projectile caused a sizeable shift in .25 caliber performance, and created a space for the development of some incredible new bullets and cartridges to launch them. During Blackjack’s operation, one of their side projects was a cartridge called the .257 Blackbird, which was a necked down version of the 7mm Blaser magnum cartridge. It promised .257 Weatherby case volume and velocities in a beltless, modern case design. We chambered a barrel for this cartridge and were very impressed by it’s performance, but in the end the Blackbird was hamstrung by a lack of brass availability. The parent 7mm Blaser Mag had very limited popularity in the United States, and the only brass manufacturer for the case discontinued it’s production.

Fast forward to 2022, and Hornady’s release of the outstanding 7mm PRC. The engineering team in Grand Island chose to the give the 7mm PRC its own unique case design rather than simply necking down the existing .300 PRC, and their design produced a tremendous balance of performance and efficiency. For those of us who just can’t leave a good thing alone, this new case design immediately got our wheels turning with thoughts of what it could do when paired with the new crop of high BC .25 caliber bullets. As soon as the 7mm PRC print dimensions were released by SAAMI, we began work on a .257 caliber variant. We expected that the case volume had the potential to rival the Weatherby for velocity, and the beltless design guaranteed that we could feed it flawlessly from a host of magazine styles. We’re big fans of the Hunter magazines from Hawkins Precision, so having a magnum .25 that fed well in them would be great news. Also, the PRC’s 2.280″ case length gave us something else that the classic .257 Weatherby couldn’t: compatibility of long bullets seated at optimal length with the current crop of medium length actions. Being able to produce Weatherby Magnum speeds with high BC bullets in a lighter weight action could make this the pinnacle of performance for those shooters looking for an easy to carry, fun to shoot, extremely accurate medium game rifle.

 

Reamer and test rifle design

We took our idea to JGS Precision Tool and had the chamber reamer ground. Having gained a good bit of knowledge through development of the .25 SAW, we used a very similar .140″ freebore length to give optimal positioning of the 130+ grain .25 caliber bullets now on the market. The current reamer has a neck diameter of .289″ and was designed around Hornady 7mm PRC brass, and we do foresee the possibility of doing a revision to a .291 or .292″ neck as some of the other high quality US brass manufacturers take up 7mm PRC brass production. We’re lazy wildcatters, so the existing body and shoulder dimensions were left alone. Certain things that aren’t broken don’t actually need to be fixed, it turns out.

The old .257 Blackbird test barrel never left the shop, so as soon as the reamer arrived we cut off the Blackbird chamber and cut a fresh chamber for .25-7PRC. This tube is a 7.25″ twist 5R cut rifled M40 contour produced for us by Bartlein Barrels, and had already proven to be a shooter when initially built. We had fired around 120 rounds on it as the Blackbird, so the barrel was already well seasoned for testing. After the cut down and re-chambering, our test barrel was exactly 24″ inches in length. Given that our primary business is hunting rifles and the majority of them are now used with a suppressor, we felt that 24″ would be perfect to give a true representation of the performance that customers can expect in the majority of rifles. Like all other magnum cartridges, there is certainly some velocity that could be gained by running a longer barrel.

The fresh .25-7PRC test barrel was installed on Caprock action #CTX0080, which is one of our medium length magnum actions and is bedded into the excellent Manners Composite Stocks PRS1 competition rifle stock. We’re running the Hawkins Precision medium length Hunter DBM on this rifle as well, which gives an internal magazine box length of 3.210″. Weighing in at 15.0lbs fully loaded with a Kahles K525i scope, AB Raptor 8 suppressor, and an Atlas BT10 bipod, this rifle is well under weight requirements for both NRL Hunter Heavy division and Hunter class at the annual Nightforce ELR Steel Challenge! It’s more than a bit tubby for a mountain gun, but for wringing out what this cartridge can do it is ideal.

Case forming and load work

The first order of business before doing any real testing is to come up with an effective method to properly form cases. We used the chamber reamer to cut a simple case form die from a Newlon Precision die blank for the initial neck down from 7mm as we were itching to get going with the test. An alternative that’s available off the shelf is to use an RCBS .25 WSSM sizer die, adjusted up high enough to clear the longer case body of the PRC. The 25WSSM shares the same shoulder angle as the PRC, but has a larger body diameter and therefore has no effect on the case other than the neck. This makes the neck-down of new brass a simple and painless process, and unlike using a 7mm PRC bushing die for forming it doesn’t leave an unsized portion at the neck shoulder junction. After initial case forming, we used a Hornady Match Grade 7mm PRC full length bushing sizer die with a .281″ neck bushing and a Hornady #5 expander for case sizing. For bullet seating, we bought a Forster Products .257 Weatherby Magnum Ultra Micrometer seater die and reamed out the sliding sleeve with the .25-7PRC chamber reamer. This is a simple and inexpensive process, easily achieved in conjunction with the regular work of a rifle build.

  All of our load testing was performed on once fired Hornady 7mm PRC brass, which we body sized in a standard Hornady 7mm PRC full length sizer die and then necked down to .257 caliber. We bumped the headspace back .003″ to 1.897″ at the .420″ datum point, which matches the measured headspace of an unfired 7mm PRC brass case out of the box. Prior to testing, we measured and recorded the following maximum cartridge OAL’s and CBTO measurements for various bullets that might be used in this chamber. All CBTO measurements were taken using the Forster Products Datum Dial measurement system, with the .257 cal bullet dial.

Bullet             Max COAL             Max CBTO

135 Berger LR Hybrid      3.210″                    2.530″

133 Berger Elite Hunter  3.200″                   2.532″

115 Berger Hunting VLD 3.104″                   2.510″

110 Hornady ELD-X         3.082″                  2.510″

110gr Nosler Accubond    3.058″                  2.542″

128 Hammer Hunter        3.210″                   2.533″

80gr Barnes TTSX            3.040″                  2.518″

The following powders were tested to establish a baseline for their performance in the .25-7PRC. Other than the powder and charge weight, the load data was identical and is listed below. Standard deviation numbers are for three shots, unless noted.

Test load specification: 135gr Berger LR Hybrid, 3.200″ approximate OAL/2.520″ CBTO, Winchester WLRM primer, Hornady 1x brass

63.9gr Hodgdon H1000: 3238FPS/19.0SD, .789″ group, near max pressure

66.7gr Hodgdon Retumbo: 3270FPS/14.3SD, .541″ group, near max pressure

60.6gr Alliant Reloder 26: 3124FPS/17.9SD, .435″ group, mild

59.6gr Vihtavuori N560: 3117FPS/3.7SD, .518″ group, mild

65.0gr Vihtavuori N568: 3000FPS/15.5, .507″ group, mild

67.6gr Vihtavuori N570: 3240FPS/17.0SD, .611″ group, mild

 

  After establishing some starting points, we decide to move forward with an OCW test using N560. The starting charge weight had shot well enough with a consistent velocity deviation, and it is available. Availability is a huge factor for powder selection right now, although hopefully supplies will ease up on all of our favorites before too long. Here are the complete results of the N560 OCW test with the 135 Berger LR Hybrid:

60.8gr: 3159/6.2, .467″ group

61.4gr: 3188/18.3, .680″ group

62.0gr: 3214/5.3, .472″ group

62.6gr: 3240, one shot only, MAX pressure. Fired cases from the previous three charge weight all held a steady case web measurement of .5313″. This charge weight saw the web diameter begin to increase to .5316″, and the first signs of ejector hole and primer flow.

  Knowing that the future of this cartridge in our shop is bright with lots of hunting trips, we decided to pair up the 62.0gr N560 charge weight with the Berger 133gr Elite Hunter bullet. This projectile has been well proven by our customers on everything from Coues deer to elk and aoudad, and combining it with 3200FPS+ muzzle velocity yields performance that feels like shooting a laser beam. It turned out to be a winning combo in this cartridge too, with the first test group fired measuring .316″ at 100 yards and producing a muzzle velocity of 3240FPS with an SD 2.8FPS. With 58 rounds now fired on the barrel and new chamber, we decided to give it a good cleaning and borescope inspection. The first 3 shots on the clean bore printed the .150″ group shown in the picture below. A winner indeed!

Stretching Out

  Satisfied with the short range accuracy of the new wildcat, it was time to shoot farther and confirm performance at extended ranges. Our first stop was a 12″ plate at 475 yards, which is large enough to catch an errant wind call(not that those ever happen!) and still gather good drop data. The conditions were excellent with a mild half value left to right wind, and our first shot center punched the plate. The next two clustered right with it, and produced an impressive looking group measuring around 1.8″ center to center, with barely 1″ of vertical dispersion. When developing a load for any cartridge, we don’t want to see vertical dispersion in excess of .5 MOA at distance. At 475 yards, 0.5 MOA measures approximately 2.5″, so this load performed well within our acceptance criteria. That performance was repeated at 1020 yards and 1205 yards; at both distances groups held less than .5 MOA vertical dispersion.

 

N570 Powder Test

  It’s almost unobtanium these days, but we had enough Vihtavuori N570 on the shelf to at least see how fast we could drive this quarter inch rocket launcher. N570 is well known to produce both great accuracy and peak velocities in overbore cartridges, so we’d be crazy not to try it! As expected, the speed did not disappoint. Here are our results for N570 using the 133gr Berger Elite Hunter loaded at 3.170″ COAL (.030″ off the lands), Hornady 1x fired 7mm PRC brass, and Winchester WLRM primer:

68.1gr: 3273FPS/8.0SD, .602″ 5 shot group

68.6gr: 3307FPS/10.0SD, inaccurate(over 1″)

69.2gr: 3311FPS/14.9SD, inaccurate(over 1″)

69.8gr: 3350/5.8SD, .477″ 5 shot group, approaching max pressure. No flow on case head or primer, but .5316″ case web and slight bolt click felt on 1 round.

As attractive as 3350FPS sounds, when we shot the 69.8gr load at 620 yards the accuracy didn’t rival the slower N560 load. This is not much of a surprise, although if N570 were in greater supply we would certainly have spent more time tuning a load with it. As it stands today, we’re quite happy with 3240FPS and very consistent accuracy in a 24″ barrel. Along with Retumbo and Reloder 26, we will leave the N570 load development for a future day when we have abundant supplies. Stay tuned for this, as well as additional bullet testing in the months to come. There is a 134gr ELD Match bullet from Hornady just around the corner that is just begging to be loaded up in this platform, and at some point we will go completely nuts and see how fast that little 80gr Barnes TTSX can go too!

 

Summary and final thoughts

  The .25-7 PRC achieves and even exceeds the performance of the classic .257 Weatherby Magnum, while being able to fit comfortably in a medium length action. We believe that this makes an ideal pairing for the long range medium game hunter, as well as those who just love flat trajectories and raw horsepower in a package that won’t hammer the shooter with excessive recoil. Although seriously overbore for PRS style matches, this cartridge could be very effective in lower round count hunter style matches and even extended long range competitions. During our testing from 475 to 1205 yards, the shooter could easily spot his own impacts and even watch trace on many occasions. The big 7mm and .30 cal cartridges will certainly provide an energy advantage when needed, but with the 133gr Berger the .25-7PRC will hold 1000ft.lbs of energy and impact velocity over 1800FPS to 1050 yards at our altitude of 3000 feet above sea level. This is more than enough for just about any shot an open country pronghorn or mule deer hunter could encounter, and very capable on elk sized game inside of 600 yards. The cases can be formed using off the shelf, commercially available dies which keeps operational costs low compared to some other wildcats. We will be adding this cartridge to our regular lineup, and are excited to bring more rifles chambered in this caliber to life in the near future!