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“Wildcatting” cartridges is nothing new. Ever since the invention of standard cartridges, people have been making non-standard cartridges out of them. The motivations for these home-brewed concoctions vary widely.

Everything from eking a little more performance — like the .30-06 Ackley Improved — to making an entirely new cartridge for a specific purpose, like the 6.5 Creedmoor, to matching the performance of a caliber made for one type of firearm to another, such as the .300 Blackout. Then, there are those that are made just because they can.

That final category is at least partly the reason for one of the newest intermediate calibers, tentatively dubbed the .25 SPC. Like me and a lot of other pig hunters I know, the good folks at Precision Rifle Ordinance in Carthage Mississippi have been long-time fans of the 6.8 SPC.

P.R.O. had a lot of trouble getting a 6.8 SPC subsonic load to cycle reliably in an AR-15 (I gave up on that project years ago). They suspected, however, that they could wring more velocity out of the round while still maintaining almost all for the weight by dropping down to the 117gr .257 bullet.

P.R.O. started with the 6.8 Special Purpose Cartridge case, a modified .25 Remington case. They necked it down to accept a .257 caliber round. They worked with both Hillbilly Brass out of Angleton, Texas for the brass and Dave Manson of Manson Precision as a technical advisor for the gauges and reamers.

The big technical challenge was, not surprisingly, getting just the right shoulder angle for the difference between the .277 and .257 rounds from the 6.8 SPC to the .25 SPC.

The cartridge was developed with the Hornady 117gr SST round in mind. Packed with a compressed charged of H322, that round should have a muzzle velocity of 2,800 fps.

The combination will deliver just over 2,000 ft-lbs of energy at the muzzle, remaining supersonic all the way out just past 800 yards, and still delivering 600 ft-lbs of energy at 600 yards.

That would make one heck of a varmint and antelope round, as well as being plenty of bullet for the white tail deer we have around here in Texas’s hill country.

A few of you may be putting together that this round is almost identical to the .257 Roberts of long-time fame, the cartridge that Jack O’Connor himself said was a more versatile cartridge than even the .243 Winchester. And this one will load in an AR platform rifle using 6.8SPC magazines.

The .25 SPC will be submitted for SAMMI approval later this month. I’m looking forward to it, and foresee a new 18-inch upper in my future.

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  1. “And this one will load in an AR platform rifle using 6.8SPC ammunition.” This sentence doesn’t make too much sense

  2. .257 roberts is a rimless cartridge and tapered nicely too… any reason it couldn’t work in a semi-auto rifle without needing to reinvent another wheel?

    • Oh, I get it: it’s the magazine/receiver dimensions that are the problem. You’re trying to avoid having to build a gun completely from scratch… never mind.

    • Unlike it’s Mauser cousins, the .257 Roberts has a COL short enough to be chambered in an AR10, although I’ve never heard of it being done before.

    • More people have AR15 than AR10 rifles, so a round that could be used by switching AR15 uppers would have more potential users than a .257 Roberts used by switching AR10 uppers.

  3. SAAMI. Sporting Arms and Ammunition Manufacturer’s Institute. Someone seriously needs to edit these things.

  4. Having interacted with the 6.8 SPC development team, I know this was tested over a decade ago. I remember handling samples of the SPC cartridge with 6.5mm and 7mm projectiles. I recall one person telling me that the 6.5 was an excellent performer in the tests, even though the 6.8 won out.

    • In talking to MSG Holland, I remember the .264, .277, and .284 bullets were all tried, but not the .257. Do you specifically remember trying that one as well?

    • From what I can find the 25-45 has an 87 grain loading at 3000 FPS from a 20″ barrel and their 100 grain “swine smasher” at 2650 FPS. This cat is proposing a possible 2800 FPS with a 117 grain bullet. That means you can stuff it with 110-120gr hunting bullets like the Nosler Accubond and Partition and go after deer and yes, even elk.

      • I have shot my own .25×6.8 spc. for several years, it performs beautifully in an 18″ AR. Compared to the .25-45 with a 24″ barrel the numbers are nearly identical. So the same basic ballistics with a full 6″ shorter barrel it’s hard to beat.

    • TFB published a piece comparing the .25-45 Sharps to other intermediate calibers, and came away with a very pessimistic view of the cartridge.

      I’d like to see them do the same for the .25 SPC. Not that I have any way to know if what they say is accurate, but it’s the best I can do. 🙂

  5. I’m assuming this cartridge has a higher maximum allowable pressure than 6.8SPC because necking down a case always leads to less case capacity not more, and this new cartridge has significantly more muzzle energy.

    • E=(1/2)mass*velocity^2

      You can drop weight and gain speed in equal amounts, but since the velocity value is squared where as the mass value is not, the energy will still increase even though your momentum (mass*velocity) would remain the same or even slightly lower.

      • Yes, if you double the weight you double the energy but if you double the velocity you quadruple the energy. However, doubling the velocity requires 4 times the powder, not double. This requires more case capacity and by necking a case down you are making the capacity less. Look at the .308 derived cartridges. From .243 to .338 Federal you get a steady increase in muzzle energy across the board with the latter having nearly double the energy. If they’re running the same pressure this would produce around 1500 ft/lbs not 2000.

    • It’s a thought, but also maybe it stays closer to peak pressure longer. Just a thought, I can’t tell from the data.

  6. Interesting. Any way to know length of that barrel (supposedly spitting 117gr SST at 2800 fps)? The whole idea seems promising (6.8 SPC simply was not born for longer distances, and this may be a nice fix), but there is inevitable comparison with 123gr Grendel. I wonder if that muzzle velocity might beat the better bullet here.

    • Definitely inevitable; as soon as he said he was necking down a 6.8 SPC to .25, I though “why not just go for a 6.5 Grendel? Does it HAVE to be .25 rather than .26?” The answer is right there: because you can, I guess.

      Looking at a 120gr Grendel loading, it gets better energy, heavier bullet on top, and, I suspect, better BC (though probably rather close), so probably better range. Maybe mag capacity? SPC would hold the standard 30 instead of 26 in a STANAG sized mag, I think.

      Edited: 120 gr Grendel doesn’t get better than 2800 fps velocity; lighter loads do, but that isn’t what I was comparing.

      • I take it back, I found a BC calculator, and it looks like a .25 117gr bullet will have a decently higher BC than a .26 120gr bullet. Since velocity and BC are the biggest factors for range, it should have better range than the Grendel.

        • The Grendel is a smaller case (similar diameter to the 6.8 but much shorter to allow the longer 6.5mm bullets) and requires a 20-24″ barrel to get anywhere close to published velocities. Some modern powders are changing this slightly but it still needs a longer barrel than the 6.8 to get similar velocities.

        • Should really use the 123gr Hornady bullet, since that seems to be far & away the most popular Grendel bullet (.510 BC IIRC).

          So, if the only difference in bullet diameter is .004″, and the bullet weight of SPC is ~20% less, and its powder capacity also less (narrower case), then it’s either operating at much higher pressures (i.e. throat erosion), or notably less powerful than Grendel. Not necessarily a bad thing, since it’s at least different, unlike 6.8spc that’s nearly identical in every way except inferior bullet BC.

          The demand for a round yet another division between 223 and 6.5G is the real question. If the velocity of SPC is higher but ultimate range shorter, it could be an even better optimization for the <400yd combat or hunting that the average rifleman engages in. 6.5G mainly stands out at longer ranges where the reduced drop, drift, & energy loss from that high BC bullet make all the difference, but where most shooters fear to tread. If the bullet's lighter and the velocity/ballistics are the same or less than Grendel, I don't really see the point.

          Once again, the real barrier to optimization based on data-driven requirements for a cartridge (i.e. a true 'clean sheet' design) is the AR platform's small bolt head and magazine well…

      • We do need real-world muzzle velocity with known bullet types to compare.

        As specified on Hornady’s site, .257 117gr SST’s on-paper G1 BC is 0.39, while .264 120gr A-MAX is 0.465, and 123gr SST goes beyond 0.5. So Grendel wins this part of pissing contest. But then muzzle velocity of AR-compatible Hornady’s loading is moderate – they claim just 2350 fps out of 16″ barrel. It would be hard to compare rounds without knowing that MV.

        The other thing is PRO HMFIC’s comment about “not developed with the -15 platform from the get go”. I am in no way knowledgeable about loading 6.5 Grendel for bolt gun, but certainly it can be loaded “long”, exceeding AR-imposed OAL, and this might result in some interesting results. The only problem is few people will care about idea – why bother with Grendel when .260 etc. fits short actions?

  7. I made this wildcat out of interest in using the 6.8 case (since it fits well in both a 700 short action & the -15 platform) and the equal love of the 25 WSSM cartridge. While it was not developed with the -15 platform from the get go, it has been adapted for it out of necessity and a lot of begging by the author of this article.

    We didn’t opt for the 6.5G casing for two reasons: 1) the 25 Raptor already exists, & 2) we didn’t want to have to use the -10 platform [we’re subsequently working on a barrel conversion for the SCAR-16 platform].

    • 6.5 Grendel is an AR-15 platform caliber… why would you have needed to move to the ar-10 platform? Are you thinking of 6.5 Creedmore?

      Also; looks like the 257 Raptor is based on the .223 case, not Grendel case. ( Is that the 25 Raptor you’re talking about?

      • Grendel or Creedmoor or both need to tweak their numbers to not be the same (264 Grendel or 25 Creedmoor or something). People get them confused *constantly* and the result is nonsensical comparisons between Grendel and 260, or Creedmoor and 5.56, and so on.

    • Can you provide more detail about muzzle velocity/barrel/OAL used? I also wonder if you might try 25 cal Noslers or Bergers – they do seem to beat relatively low BC of 117gr SST.

  8. Great wildcat idea! The 6.8 was just too large of diameter for case capacity. The 25-45 Sharps fails because case length is too long for heavy .25s.

    This is a great idea. Should produce good ballistics. Don’t choke this out by keeping it private.

    Would make an awesome little brother cartridge to the 25-06 but for AR-15s.

    • Unless really overdriven, I’d think it would sit right below Grendel on the power scale, which would suggest a recoil response very similar to 5.56 i.e. very controllable. Grendel isn’t unpleasant or anything, but there is definitely more ‘there’ there than on a 5.56 platform. I’d think this 25SPC would be a great Grendel-like round for ultra-short barrel rifles, like 7″ or so, that simply can’t exploit the extra powder of the wider Grendel case. Even so, my understanding is Grendel is better from such platforms than many think due its popularity as a long-barrel long-range cartridge.

      • Grendel case diameter too large – poor magazine capacity, requires thin AR-15 bolt head. Shoulder not ideal for auto-loader. Requires long barrel for optimal performance.

  9. This looks pretty freaking awesome! 2800fps in a 117gr class bullet is nice. Is it similar to the 6.8 in that it attains this in ~16″ barrels? The need for 20+” barrels is what kills a lot of the AR15 wunder calibers for me and the precise reason why my next gas gun was going to be a 6.8. This (potentially) changes that assuming I can get my hands on a barrel with relative ease.

  10. I’ve had one of these wildcats for almost 3 years. It’s called a 25 DTI and has been built buy the company Dedicated Technologies for a long time. 87 gr bullet pushing 3,000 fps in an 18″ barrel. It’s an awesome round. 87gr TNT HP is enough to destroy both front shoulders on a whitetail.

  11. Because we don’t have enough calibers now, the world was waiting for a new caliber!

    Or not.

  12. 6mm grendel is what u want. Way better bullet selection. 6.8spc case is made for short light, low bc bullets. Luv the grendel hate. You need a 32 inch barrel and the bolts break, um 2004 called and they want there fake news back.

  13. Very interesting cartridge. Will have to see more details on it. AR15 performance has a 6.8 based wild cat I’ve been considering called the six5. Gets 123 gr bullets to 2400-2500 fps and 100 gr bullets 2700-2800fps out of a 16″ barrel. This cartridge could make me reconsider. SAAMI approval would be cool. If performance is right out of shorter barrels I think I would do it. Or just be a true American and get both!

  14. “P.R.O. had a lot of trouble getting a 6.8 SPC subsonic load to cycle reliably in an AR-15 (I gave up on that project years ago). They suspected, however, that they could wring more velocity out of the round while still maintaining almost all for the weight by dropping down to the 117gr .257 bullet.”

    Wait, what? So they think the solution to subsonic load cycling issues is to go to a lighter bullet and going supersonic?

  15. I thought the 6.8 was made from the 30 Remington cartridge. So basically they are remaking the 25 Remington? With a stronger case and at a higher pressure…25 Remington ++P++!

  16. This is very close to the 25X6.8 reamer and cartridge I designed in 2013 that was later adopted by Black Hole Weaponry who has been selling barrels since then. I used a full length case and did not move/change the shoulder. A large amount of data has been amassed on it over the past few years.

    It is a fine little deer cartridge and will handle the 117’s SST or a RN. They run out of energy because of the weight but with the SST the speed does stay up nicely. I’ve worked with the 100’s from Hornady a bit and out of a 22″ I was getting 2770 or so. I have a bit more room to play there. I felt that it was the best balanced for the case. I’ll have to try the 117’s in the next week or so.

    I’m looking forward to watching the SAAMI process on this one.

  17. I’ve been using 25-223 for a few years. In a 20″ AR it can easy hit 3,000 fps with 90gr Sierra GKings over the chronograph. I admit a certain satisfaction getting .250 Savage performance from an AR15 with only a simple barrel swap.

    I see zero advantage to needing specific magazines and an entirely new bolt to get approximately the same practical results. Even the new .22 Nosler can’t demonstrate enough practical advantage to get me interested. I certainly have no qualms about others trying something different since I’m not a “we have enough cartridges already” type.

    FWIW- The 25-223 has a shorter neck than the 25-45 Sharps which enables it to use heavier bullets than the Sharps version. I put very little credence into opinions on TFB.

    • Where can you get barrels and dies? I see that C&H make dies, but there are 3 versions and the first is listed as 25-223 aka 25 Sharps. I want the shorter version like yours!

      • Contact 320pf on the AR Variants section at He’s the go-to guy for barrels in 25-223 and case gauges.

  18. Dedicated Technology in Bemidji, MN has been building uppers chambered in a “25SPC” for years. Dtech calls them 25DTI. It’s a wonderful cartridge that’s laser accurate. 3000 fps with a 90gn sierra flat base out of an 18″ barrel. Devastating on white tails.

  19. Yes, this is nothing new, and another indication that the author did not do his proper due diligence before writing this piece. This bugs me about the gun/media folk. A simple Google search would have revealed the fact that this new cartridge is not new, and that it is clearly not news. Not newsworthy anyway. How about doing an article about Mile Milli at Dedicated Technology in Bemidji, MN – the guy that developed this cartridge more than 7 years ago and has sold literally thousands of them? Hmm…

  20. Wow! A blast from the past! I started the “25 DTI” back in ’09 and have chambered piles of them. It is just a great round for tha AR in a 16″ or 18″ barrel. I like the 90 Gr Sierras as well, and have taken many Northern Whitetails with it. Right now it is probably my biggest seller.

  21. I also have had a 25 DTi which is the same round it sounds like. Got mine in 2011 and have been loading 75-90 gr bullets from an 18 inch barrel running 3000fps for coyotes and pigs deer etc.
    In fact it was the AR round used when we were filming predator hunts for the Sportsman Channel 4 years ago.
    Fact is Dedicated Technology has done the 6.8 SPC in 22(now 22 Nosler) 6mm / 25/ 6.5

  22. This sounds like an awesome ar round combine s to of my favs to the 257 and the 6.8 were can i get barrels and dies need to build a new ar so this would be great to do

  23. I sent P.R.O. in inquiry about the cartridge and barrel availability. John Stewart (Not THAT one!) their ordnance engineer sent me a reply today. I see good things from these guys as they replied so quickly!

    Thanks for the message. Most of the info you’re looking for is still proprietary until we get SAAMI approval. However, I can tell you that the cartridge will fit in a standard .223 magazine — but the preferred magazine for the AR platform will be the 6.8 mags from PRI since they have the correct follower installed whereas others (e.g. MAGPUL, etc) do not.
    And yes, once we complete the testing phase (another 2-3 months) we will start making barrels available on an as needed/ordered basis. We’re currently waiting on the blanks to get here so that we can do the testing on lengths, etc.
    John Stewart
    Ordnance Engineer
    Precision Rifle Ordnance

  24. I have been shooting the 25 SPC in a 20 inch AR15 for over two years. It is a fantastic and accurate round. Barrel by John Hollinger with upper built by Roy Winnett. Ogive and mag length are the limitations of this caliber. I have not shot 117gr pills but I currently prefer 90 gr hpbt at 3k because of listed limitations above. This bullet is the most accurate hunting bullet for my rifle. I highly recommend this rifle for deer and predator hunting. It is truly amazing. I have lots of load data for this rifle and can answer some questions about it. Hope it helps!


    Nick K

  25. has any one ever considered the 25 copperhead(25-222) in a ar 15 platform i just had one build on a cz527 american and am think about it on the ar platform because i will be able to shot balliastic tip bullets and not have to seat the bullets to deep

  26. I like the 6.8 SPC, works well with a 16″ barrel as intended. However falls short beyond 400 yards, necking it down to .25″ would require a 20″ barrel min to make it worth doing. Even 22″ for hunting and just loose the muzzle device, you don’t need it for hunting.

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