A Minor Controversy Over Cartridges

We’re having a bit of a friendly disagreement over cartridges here, and I’m curious to hear some unbiased (or at least differently biased) opinions from you guys.

Suppose you were putting together a new, cool military style rifle – not for production, but just for your own use and for the fun of building and having it. Semi-auto, detachable 20-30 round magazines, good iron sights, provision for optics, etc. The design is easily capable of handling full-power rifle cartridges, but it doesn’t necessarily need to use any particular cartridge. The question is:

Given that you are not encumbered by a pre-existing magazine design or OAL requirement, what cartridge would you use in a general-purpose individual shoulder rifle?

One school of thought here is leaning towards 8mm Mauser, because it is still relatively cheaply available (and we have a lot of it stashed away) and the gun could be built around cheap and high-quality MG13 magazines. Also, there is a general lack of semiauto, detachable-mag 8mm rifles (G43, Hakim, Yugo M76 – and none of them were issued with >10-round mags…there are also the G41 and FN49, but those relied on stripper clips). The 8×57 cartridge is a good design, and being rimless would not present any particular difficulties in rifle design.

The other side of the debate is to use an intermediate cartridge along the lines of .276 Pedersen or .280/30 (but something for which brass is still easily available, so probably one of the 6.5mm or 7mm commercial hunting rounds). The ammo would have to be handloaded, but it would allow the best balance of firepower and handling/recoil for a shoulder rifle. Any of the common .308 magazines could be used, and with some strategic lightening the gun could be in practical terms a recreation of the intermediate caliber prototypes of the 1950s like the light FAL or early CETME. The specific cartridge to be used remains undecided, though – perhaps 7mm-08, or .260 Remington – or something more esoteric.

What do you think?


  1. Personally, I like the idea of the FN FAL in 7mm Livano (7×49) cartridge, which can be easily duplicated with 7mm-08 or any other similar cartridge based on .308win case
    It would be easier on the shoulder than 8mm Mauser or 7,62×51, yet would have sufficient power for most applications in semi-auto rifle

  2. I would lean towards the 7.62x39mm Russian round for all of the reasons that you mentioned for the 7.92x57mm round plus:
    1) Shorter action length required resulting in lower final weapon weight and cost.
    2) Lower recoil with a light weapon resulting in a rifle that’s more pleasant to shoot.
    3) Numerous low cost components available (barrels, magazines, etc.)
    4) Reasonable effective range – I’m assuming you’re thinking of a “hunting” weapon, not a “sniper” weapon.

  3. I would be inclined to agree with the 8mm argument, citing the reasons you gave. It is certainly lighter than 30.06, but still packs a more serious punch than .308 Win. But the intermediate cartridge argument also has some serious chops. Recoil is obviously much reduced, making it more fun for long-range plinking (is that a thing?), and smaller size of weapon. That opens up more opportunities for shorter folks like me (I’m a stout 5’3″).

    Heck, I might recommend going even smaller into something like .218 bee (or a rimless equivalent that I simply can’t think of at the moment). That way you could hot it up like crazy, and still deal with very light recoil.

    Either that or we could just throw rocks downrange. That’s the cheapest solution of which I can imagine. But they would probably have to be explosive. So let’s make them out of lithium. Ka-BOOOOOOOOM!!!

  4. I agree with the earlier poster. I would go for 7.62×39. However, 8mm kurz would also be very interesting. For a high capacity rifle I would want a true intermediate round, something with a large/heavy enough bullet but not punishing to shoot for extended periods/quickly. .458 socom could also be interesting.

  5. This will no doubt cause some conflict, but I would avoid anything in 8mm mauser. For the life of me, almost every semiauto rifle chambered in that cartridge that I can think of seems to have some sort of problem with overgassing or cartridge case failures. Every variety of surplus ammo out there has different loading and pressure, and the rifles simply aren’t tuned to interchange the stuff. You’ll end up with a rifle that says “don’t use Romanian ammo” or “don’t use 1950s Yugo ammo” or “change your gas port adapter when using Turkish ammo,” etc. This is a hassle, and its why I avoid the caliber when I can.

    I would lean with 7.62x39mm, or perhaps something in 6.5 if you are looking for a longer and hotter round. Although, .30 caliber carbine could be fun as a plinker, and the magazines are out there in quantity.

  6. Assuming the rifle would be sized around the cartridge, I’d like to suggest one of two. First up would be the 7.62x45mm Czech. It seems to fit in between the 7.62x39mm and the 7.62x51mm. On paper it looks like it would provide better capability than the 7.62 russian but not require the rifle weight of the 7.62 Nato. Other suggestion would be th .300 Savage, good performance, moderate pressures, reasonable cartridge size and weight.

    Since it was stated that cartridge length was not an issue then how about 7mm Mauser? Great performance in FMJ, moderate recoil. If that is to much, there is also the 6.5×55 Swede. Work up a Fn FAL style action for them and be good to go.

  7. My vote would be a FAL in 280 Enfield or 7mm Liviano . A couple of folks on the FAL FILES have built venezuelan clones in 7-08

  8. I would like something in 7.5×55 Swiss. I love the round in my K31. A semi auto capable of firing some of my stockpile of surplus GP11 would be awesome. If someone made one in a AR10 type rifle and it was available in the US I would make it my next firearm purchase as soon as I could.

      • Friend of mine had one of those for many years. When he finally traded it, he traded it for a BAR.

        You would like this guy. You can’t get a signal on your cell phone in his office because there’s too much ordnance in there, it creates a Faraday cage. I know a few guys with mortars, but he’s the only one with a 4.2″.

      • Yes, Luvo Arms has an catalogue. They products are aimed at a very specific market niche, but they seem to fill it quite well. I never saw any of their rifles ‘in the flesh’, and I would be grateful to hear any first hand impressions. Did you saw/handled any Max?

  9. The 7.62×45 would be pretty tempting, but would be pretty hard to reload for – I’m not aware of any available brass. The surplus ammo I’ve seen is all steel-cased.

    I do like the 7.62×39 (and 8×33), but I think it’s a but underpowered for the project in mind. Plus, I just feel like a good AK does just about everything you can do with the cartridge, and that makes a new project with it a bit less exciting.

    7mm Mauser would be a fine idea (heck, we could build the gun in both 7×57 and 8×57 with the only different part being the barrel – the bolt and magazine would be the same for both rounds). Of course, I’m not sure compromise is the goal here. 🙂

    250 Savage and 6,5 Swede would both be fine rounds, IMO (okay, you caught me – I’m the one behind the intermediate cartridge side of the debate).

    I think the idea of a short-range Cooper “Thumper” carbine is also pretty interesting, with .458 SOCOM or another short cartridge with a large and heavy bullet. But that would be a different gun entirely.

  10. I would be looking for a tapered (conical) cartridge body, such as the 7.62x39mm or .22-250. Rusted chambers and extraction failures seem to be the most prevalent problem in automatic rifles and machineguns. Soldiers’ memoirs from all sides in WW II, Korea, and Vietnam mention stuck cartridge case jams in their automatic weapons at critical junctures. Tapered case bodies extract easily, although you wind up with a severely curved magazine.

    The 6.8mm Remington SPC II is a nicely balanced cartridge for all around use, even though it is not tapered. Perhaps a 6.5mm or 6.8mm wildcat cartridge on a 7.62x39mm case would be the optimum.

  11. Hmmm… Interesting question. Personally, I’d leave 8mm Mauser alone and opt instead for 7×57 Mauser or even 6,5×55 Suede. On a slightly more esoteric note, I am with Max regarding idea of a FAL in 7×49.

  12. For a nice light rifle, low noise and light recoil, one of the “fireball” based rounds, .223 brass is easily converted, and STANAG mags work for some versions. The small head diameter also makes for reduced bolt back thrust and allows greatly reduced weight compared to a .471″ diam case head. The more I look at 1.4″ long fireball cases, the more I think they were inspired by the .22 Hornet.

    For the larger rounds (if you’re wanting to shoot long range, say 1,200 yards), 7mm cal offers bullets with the same ballistic coefficients as the best available in .30 cal, but significantly lighter.

    If you want to go hunting, the 7mm bullets are much less prone to bending on impact than the 140 and 160 grain 6.5mm bullets are

  13. In a perfect world, I’d say the 7mm Mauser. That said, I’d be in the intermediate camp. The 7mm-08 is as close to the classic .280/30 British that exists and would be a reasonable compromise. It’s still bigger and more powerful than is really needed in soldiers rifle.

    Really, thinking about it a bit, the best would be to take a .308 case, neck it down to to 7mm or 6.5mm and then shorten it even further back to the OAL of the 7.92 Kurz while pushing a 120 to 140 gr bullet. That would be, to my mind, the best of all worlds.

    But then, all I really want is a .223 FAL… 😉

  14. 7.62X39 is the best choice.
    But for something unique, how about .35 Remington? Slightly shorter than 7.62X51, but packing a while lot more punch than 7.62X39 at most combat ranges. 180gr .358 bullets going just over 2100fps or 200gr bullets at just under 2100 fps.

  15. 6.5×55 Swedish was the first that came to mind. The 8mm Mauser would be a good choice if you think you really need that power. In the end, I think I would prefer an intermediate round for any “GI” style gun. The 6.8 SPC seems like a near perfect choice, although the 6.5 Grendel is better in some respects. But there’s nothing much wrong with the early British .280 either, except for the availability of components. The good old 7.62×39 is nothing but reliable, but would benefit from bullet development. I wouldn’t even look past something like .35 Remington, if you want to make a big hole.

  16. First thing in my mind, 6.5×55 Swede or a mimic; 6.5×47 Lapua or .260 Remington.
    .260 the easy brass, x47 the esoteric, x55 the classic.
    They all bring the same performance, something in-between an intermidiary and a full-rifle at everything from reloading-price to recoil. But with match grade accuracy out to 800 yards. Long barrel life. That 120 year old swede hit the sweet-spot din’t it?

    Then again, 8mm Mauser makes a beutiful sound…

  17. It depends: if I just need the best general purpose rifle I can make within reason, the good old 7.62×39 is really hard to argue with. If I need more power or range, I’d go with the 7.62x54r, though the 8×57 has its attractions. If money does not matter much, the 6.5×55 is my choice. I love that round! If money is no object, I’d make my own wildcat by necking the 7.62×39 down to 6.5mm.

    I do like the mention of 7.62×45 an .35 Rem, they are very good rounds.

  18. Additional thought:

    FJ42 bullpup, move the mag well underneath, semi-auto only, chambered in 7mm-08… 😉

  19. 1. 7.62mm x 39

    2. 7.62mm x 51 NATO / .308 Winchester

    3. 7.62mm x 54R

    I based my choices on the overall balance of criteria that usually pertain to the selection of a military battlefield cartridge — ballistic performance, reliability under adverse battlefield conditions, accuracy, recoil ( acceleration and torque ), availability of different ammunition types ( different bullet weights, ball, tracer, incendiary, AP, AP-T, API-T, etc. ), commonality with other available weapons, man-portability ( bulk and weight issues ), cost-effectiveness and pricing.

    I must admit that I was very intrigued with Matt’s suggestions concerning the 7.62mm x 45 Czech and .300 Savage cartridges, though. The only problem with the former is relative scarcity, otherwise it would be a virtually ideal cartridge for the purpose in hand ; the latter has excellent ballistic performance, abundant availability on the civilian market and a proven track record in the field, but is somewhat expensive and more limited with regard to the range of ammunition types.

  20. 5.56×45 using Galil magazines or 5.45×39 using AK-74 magazines.

    Either of those cartridges (contrary to Internet Wisdom) will reach out about as far as you can see with iron sights, they are both lightweight, low recoil, and have widely available magazines.

    If you don’t care about ammunition availability, maybe do something like a 6mm Russian (.220 Russian necked up), but I honestly wouldn’t use anything larger caliber than that for general purpose use.

  21. Unless you’re talking about using this for hunting (it doesn’t sound like it), in which case I’d suggest something you could reliably take whitetail at whatever the furthest range you think you’d ever see one is, maybe something like .243 Winchester.

  22. Honestly, I always thought the both .243, and .270 Winchester would make great AR round. In military calibers. 6.5×55 Mauser in a handy, 20 round AR would be amazing. YMMV…

  23. .284 Winchester that very nice caliber with the performance near the 280 Rem. or 7×64 Brennecke but with the same size of the French 7.5×54 MAS or .308 Remington

    The .284 Winchester coule be unse in Mechanism of the MAS36 or MAS49/56 Mechanism for exmple.

  24. Well my turn to comment. The original start of this conversation with Ian was due to the fact that while we have a number of 8×57 semi auto rifles we really do not have true main battle rifle in that caliber. Now normally this is no big deal but, we are working on a 7.62×51 rifle and it would not take much to convert it to 8×57. And the real reason is that we have a large quantity on 8×57 (60 or so cases) and a limited amount of 7.62×51 (20 or so cases). And the real reason is that I just want to do it.
    As for interesting calibers I would have to go with the 7.62×45. I think there is a great deal of possibilities with this cartridge. If I could find a source of brass I would do a 7×45. This could be the next great cartridge.
    So the project is a sheet metal stamped, gas operated, multi lug bolt, folding stock rifle.
    It will be FUN.

  25. I personally think 7.62mm x 45 Czech would be interesting.
    However I’ve always wondered what 8mm Kurz necked down to a 7mm
    would be like. Hmm…

  26. I think most of you guys missing the point. They want to make a one of a kind rifle using older ammo or custom ammo similar to experimental ammo in the past or current commercial ammo that also is similar to designs in the past.

    I vote for 6.5 Jap ( or something similar like 260 Remington).

    As in the 6.5 Grendal I think the 6.5 offers the best compromise between lightness/ control /wounding power and range.

  27. Right now, the market seems to be showing an interest in what I think of as inter-intermediate cartridges; ones that fill the gap between 7.62mm and 5.56mm NATO.

    The two most popular contenders appear to be 6.5mm Grendel and 6.8mm SPC.

    Personally, I’d roll with 6.5mm G, because it has a ballistic trajectory almost equal to 7.62x51mm NATO, as opposed to 6.8mm which drops like a rock (although not as bad as 7.62x39mm).

  28. 6.5 Swedish, because I’m a bit recoil-sensitive and I tend to resent things that hurt me. Apparently there were several thousand Swedish BARs chambered for it, so there must be some 20-rnd mags around somewhere.

  29. I would want a 7.62×39 for commonality. Otherwise 7.62×45 or British .280 EXP if we’re just making up cartridges with no regard to supply.

  30. the japanese army after ww 2 used a 7,62 x 51 round with less powder dan the standard 7,62 nato. with that in mind, you could build a light battle rifle around it. a light weapon, simple operating system, easy to get brass and with a good bullet.

  31. I’m inclined to go for .308 Winchester for North American terrain. The cartridge should have the needed reach and stopping power. A compensator like the one on the Seig automatic rifle might be pretty neat, allowing quick follow-up shots because of the reduced recoil. Although it’s bolt action, I think the Ruger Gunsite scout rifle proves part of the concept.

  32. Interesting thoughts.
    Where I live there is a serious problem with feral hog. Something light, handy, good knockdown, flat shooting from 25 to 300M, add integral glass (light, handy, goes in truck and knocks around)add IR sights, illumination, IR laser and goggles…
    Bullpup for bbl length, ambi controls and ejection (unless eject down) as I shoot leftie. Around 30 cal with subsonic option? .308? I just don’t know the other ones but 6.5 Swede sounds interesting.

  33. I actually wrote a paper on the latest generation of intermediate cartridges for a writing seminar my freshman year of college. It pretty much went over everyone else’s heads, but I enjoyed the research. Between 300 Blackout, 6.5 Grendel and 6.8 SPC I would choose the Grendel round for pure performance or 300 Blackout for convenience and economy. That said, square-charged magnum rounds, like the Wincester Super Short Magnums, have always intrigued me, as far as their military/defense application goes.

    • My objection to the Blackout, Grendel, and SPC cartridges is that they’re artificially limited by the AR-15 magazine length. I recognize that practical consideration make that necessary, but if I’m not starting with that restriction I know I can do better, by having the option for a longer case or projectile. IIRC, the 6.5 and 6.8 are specifically hindered by not being able to use as long/heavy a projectile as would be optimal.

      • sorry for banging in here late. The 6.5 G and 6.8 were made for different purposes. 6.5 was aiming at, as you say, optimum exterior ballistic performance in the AR-15 platform. 6.8 was developed (mostly in-house by 5th SFG(A) guys) aimed at optimum terminal ballistics in the AR-15. The .various .300 whisper/blackout/ etc. were made for subsonic performance in the same platform.

        If you take away the AR limitation, new horizons open up. AR is hard to beat for ergonomics, convertibility, etc.

        Also, be careful not to lock into the technology of yesterday for terminal ballistics. We’re looking at sintered bullets and their terminal ballistics are otherworldly. However, they impose velocity (both linear and rotational) limitations. You’re probably aware of the varmint bullet disintegration problems with some of the very fast rounds.

        I thought the various short magnums were interesting, but they don’t have enough case taper to play well in a magazine-fed auto rifle.

        Maybe the answer is to start to work from general principles, then optimize. But most round selection decisions are not optimizing decisions, but satisficing ones (meaning, you choose the first or handiest “good-enough” option, rather than pursue “the best” down the asymptotic curve. By general principles, you know you want a rimless case, and about the caliber, and about the case volume, you need. From there it’s a matter of shaping.

        A lot of research conducted in the last century pointed towards 6.5 to 7mm (.265-280) as the sweet spot, but that was for early full-metal-jacketed, lead core bullets. And yet, the major powers mostly went to 7.5-8mm (even the Japanese, who went all in for 6.5 starting in 1902 or so, reverted to 7.7 mm).

        Finally, it’s possible today to make consistent ammo and a reliable auto weapon with a steeper-shouldered cartridge that was possible in the first half of the 20th Century. More powder (and velocity) for less OAL. Progress.

  34. While my heart would say 7×57, brain would go 7-08. Same ballistics, and unlimited magazine supply as it should fit into any 308 weapon.

  35. I am a fan of “BOB” 257 rpberts a round based on the 7×57, a very soft shooting round and it has hitting power and distance in its favor. All my deer kills with this round have been one shot kills. Longest range was 250 yards. As a mam vet this round would have been far better than the 223. Bullets are 75 g to 120g, can be loaded P+, brass is no problem.

  36. I have always wanted a 6mm based on the 762×39 case, something like those used in some BR comp. Short cartridge (smaller gun) good ballistics choices, fair velocity available and easily done. Lots of mags available. I would probably want to remove some but not all of the taper but that ruins mag selection so no go there. A “coffin” style quad row mag would give lots of capacity without being too tall.

  37. I’d throw my vote in for 6.5×55 Swede. Just a beautiful cartridge in pretty much all aspects.

    There is one thing I’d like to throw out there to those thinking of the “Short Magnum” and “Ultra Short Magnum” calibers is…well, those rounds are fat, which is rather detrimental to making a large capacity magazine. Length of the magazine is a bit less of a concern, but width and length are the problematic factors.

  38. an 8x33k necked to 5.45 (using the extremely long bullets from 5.45×39 Russian head-stamp “10 87”) with a shoulder angle like that of .300wsm.

  39. Personally, I would like the take the g43, put a 15 round magazine on it, US military style peep sights, and on the side mount throw a ACOG style scope or a variable power 1.5/2-10x scope on it, and load it up with 90’s vintage Serbian 196 grn DMR 8mm mauser ammo or modern ppu FMJs

    Though if Im going of an intermediate rifle, I would build a 6.5 grendel SPR AR with a 20 inch heavy fluted barrel, a bipod, variable power 1-5x scope on it and a match trigger

  40. A magal carbine (galil Mar in 30 carbine) only the mags are a bit fatter and have 9mm Dillon based cartridge using cut down 6.8 brass ( for pressure) to 10mm mag length and .358 diamter bullets.

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