Ideal rifle for ww2?

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Well, as some of the people on this forum know because I have blathered on about it before, I have had two rifles built with custom 6.5mm cartridges.
The first was the 6.5mm X 308, this cartridge does date from the 1950s so I certainly didn't invent it. Remington finally commercialized it in 1997, about 6 years after I had mine built. I shot out one barrel in about 5,000 rounds. I also had a 6.5mm Remington Benchrest (cartridge) rifle built. .308 case shortened by about 0.5 inches. First gun uses a 1-9 twist and will fire at least 140 Grain Serria's with accuracy to 1000 yds. Most of my shooting was with 120 grain Sierras at shorter distances. The Short cartridge rifle uses a 1-10 twist and was used mainly with 120 grain Serrias. One attempt to use 140s had bullets sideways at 100yds. Reason for the first rifle was I got tired of firing 168 grain Serrias from a heavy barreled .30-06 bolt gun. I was competing in a local league and we fired 40 rounds prone at 300yds (plus 4 sighters) in the morning with iron sights and another 44 rounds in the afternoon with anysight (mostly scopes). I found that at round 36 or so I was looking over at the ammo block and thinking "only 4 rounds left" which is certainly not the way to win matches

The 6.5 certainly was more comfortable to shoot. It didn't have any more trouble with wind than the .30 cal rifles had.

as to recoil my experience with muzzle breaks is non-existent. You couldn't use them in competition at the time. I once was next to guy using a .300 magnum and the muzzle blast from his rifle (no muzzle brake) was bad enough that I waited to fire until after he did after the first time I was squeezing the trigger and got hit with the blast wave. Effective Muzzle brakes are not friendly to squad mates

Recoil is proportional to the weight of the rifle. Double the rifle's weight and the felt recoil will be cut in half, not practical for a military rifle.
Most military rofles are going to wind up close to each other in weight unless you can really change the materials (aluminum receivers/plastic stocks).
You are correct about the effects of the powder charge adding to recoil, however most people figure the escaping gases as a constant ( the same for all rifles, not quite true but trying to measure the average velocity of the escaping gases is almost impossible) and for most military cartridges the weight of propellent isn't that far apart until you get to the either the 5.56mm or 7.62 x 39mm class cartridges.

My 6.5 X 308 used charges between 36-40 grains depending on exact type of propellent and bullet I was using and I used 46.5 grains in my Palma gun (308 with 155 grain bullets ) DO NOT USE in semi autos. Granted the .30-06 will use a bit more. The older 1906 loading and the 172 grian M1 loading using about 50 grains (exact amount depended on the lot of powder). However cutting 10 grains of powder from the charge isn't going to really change the recoil as much as cutting 30-50 grains from the weight of the bullet.
 
There is plenty of youtube videos where the 6.5mm Creedmore and .224 Valkyre show excellent results beyoond 1000 yds. The ammo of Valkyre fits the Ar-15 receiver as-is.
There was automatic rifle in 6.5mm Arisaka calibre in use 100 years ago, granted by ww2 people will be able to come out with even better rifle.
 
The Arisaka case (or Carcano) would be good starting points in the 1930s, different powders that some people use now. I have used IMR 4895 which is a pre WW II powder. I didn't use them (or the 6.5 Swede) because of the higher cost of Brass ( I had over 500 rounds of the 6.5 X 308 which I actually made by necking up .243 cases.) and the non standard rim diameters. I didn't want to pay for modifying extractors on one-off rifles.

The main problem with both the small 6.5 rounds were the bullets, and by extension the rifling. All of the old 6.5mm military cartridges (including 6.5 Greek, 6.5 Dutch and Romanian, and 6.5 Portuguese) started with 155-160 grain round nosed bullets at around 2000-2400fps and needed a quick twist in the rifling to stabilize the long bullets. Please note that the .30-03 cartridge in the first Springfields used a 220 grain round nose and that is why the .30-06 used a 1-10 twist, legacy.
Going to lighter but just as long bullets with pointy ends means you can use a bit less twist in the rifling and still get the needed spin on the bullets because of the higher velocity.
If you seperate your rifles and squad/company machine guns from your battalion/AFV machine guns you don't need the power/size of the larger rifle rounds but can still have much more range than the 7.92 x 33 Kurtz and the 7.62 X 39 which were also victims of legacy tooling (both barrel making tooling and bullet making tooling), which have short, squatty bullets of relatively poor ballistic shape. Please note the Russians kept 7.62 X 54 machine guns at the company level.
 
Not aware of a 6.5mm Japanese auto rifle in 1918 period. A machine gun but not a rifle. Please advise.
 
Good show.
The Fedorov used 6.5mm Japanese. I thought you meant a Japanese rifle.
So me got confused
 
I would also note that many of the countries that changed from the round nosed bullets to spitzers were somewhat constrained by existing chamber dimensions, make the bullet too light and it is too short and has a long jump before it hits the rifling which can affect accuracy.

No 5 being the closest to the original military bullet. You can't seat the bullets out too far for military ammo or you may not get a good grip on the bullet (soldiers have an amazing ability to dent, damage, bend all sorts of things) and the magazine will only handle cartridges of a certain length.
As the barrel wore on my 6.5 X 308 I seated the bullets out longer and longer to keep them close to the rifling. At one point they were 0.050 (1.27mm) too long to fit in the magazine. Not a problem in rifle matches that required single loading and gave you one minute per shot
 
Hello Shortround6,
After your last post, I decided to do some poking around to see what was already out there.
It turns out that the 6.5 mm x 47 Lapua case is pretty close though I was thinking of even smaller than that.
Also, it seems that the 6.5 mm Creedmoor also has the 30 degree shoulder I was originally proposing and appears to have no issue running in a semi auto rifle.

Regarding the issue with a muzzle brake:
There are two issues with recoil that would affect full auto fire: Actual Recoil and Muzzle Climb.
Either can be greatly affected with a well designed and ergonomic rifle, perhaps one with a straight line stock as on the FG42 and maybe even incorporating a buffer system as the FG42 did.
A practical muzzle brake can also affect both the recoil impulse and muzzle climb. An example of this can be found on the AK-74.
Full sized rifle versions can be found on many of the pre-war Russian semi autos. It doesn't have to be quite as severe as on the McMillan.


Is there something inherently wrong with fast twist rifling?
In the field of Benchrest shooting, an overly fast twist over stabilizes the bullet so that it takes longer to "go to sleep" but that really only makes a difference of tenths of an inch in group size. With military rifles, it makes no difference, not even in lethality if the bullet is designed properly.
Regarding .30-06 and 1-10 inch twist, I do not see any better twist rate for the cartridge.
Typical twist rate for the .308 Winchester is 1-12 inch but when I was shopping for match grade replacement barrels, I was actually finding that the better manufacturers were making 1-10 inch. It has been a few years since I replaced a barrel, so I don't know if there is a different standard today.
With very finely made bullets, you can get away with less rifling twist. When bullets are less precise such as for military ammunition, a bit faster rifling may be needed to keep the bullets stable.

Shortround6 said:
Going to lighter but just as long bullets with pointy ends means you can use a bit less twist in the rifling and still get the needed spin on the bullets because of the higher velocity.
Click to expand...

While what you stated here is technically correct, it may not be the best advice.
If a bullet is not spinning fast enough to be stable at a certain velocity, then pushing it faster MAY make it stable but only very marginally so and it may not stay stable for very long.
Another factor worth pointing (no pun intended) is that round nose bullets are fairly short for their weight while equivalent weight spitzers (I had to correct the autocorrect that time), are longer for the same weight and require faster rifling twists to remain stable.
That is because they have less rotational inertia because more of their mass is at a closer radius to the centerline of the bullet and apparently it is the rotational momentum of the bullet that is important.

- Ivan.
 

see 6.5×47mm Lapua - Wikipedia

The 6.5 Lapua may be a very fine cartridge indeed but most of it's features are not needed in a military rifle, especially one of WW II vintage.

It seems to be a .308 with a small primer and the shoulder and neck pushed back 4mm and the shoulder changed to 30 degrees. Main advantage over the 6.5 x 308 is that when loaded to the same overall length the bullet, since it sticks out further, doesn't stick back into the case as much, this may help accuracy, and helps the case be reloaded many more times. Not a factor in military ammunition. It is also using modern powders and is being loaded to rather high pressures. Higher than either .308 commercial (unless some sort of "magnum" load") or 7.62 NATO. Target shooters can flirt with pressures a bit above normal, military cartridges should not. In fact military cartridges should err on the side of caution, especially in the WW II and before era when climate testing was either not done or done in a rather sketchy fashion.


Some sort of muzzle brake could probably be used, given the small powder charges it shouldn't be that much of a problem, Even the Thompson gun had one for a while, however it was deleted due to manufacturing costs.

Might have worked better if the slots were angled rearward. Also the gas volume and velocity from a .45ACP powder charge wasn't that large, especially from a long submachine gun barrel.




A too fast rifling twist is better than a too slow one but a fast one tends to raise pressure a bit. Not as much as some people have claimed but a bit. It also places more stress on the bullet/jacket. take a bullet doing 2600fps with a 1-12 twist, the bullet is spinning at 156,000 revolutions per minute. with a 1-10 twist it is spinning at 187,200rpm. I would note that many Palma rifles are built with 1-13 twist or even 1-13.5 but then they are never intended to shoot bullets heavier than 155 grains and with their long barrels and often higher than factory pressures could get the rate of spin needed. Some M-14/M1-A shooters would use 175-190 grain bullets in the 600 yd stage (and 168s at the shorter stages) and were somewhat pressure limited to avoid damage to the gas system (bent op rod) so they may have prefered a quicker twist for the heavy bullets. Just what I heard a number of years ago.

One of the claims to fame for the .30-06 as a hunting cartridge was, back in the days when the average man could only afford a very few rifles, was that the .30-06 could be used for practically anything on the North American continent. It may not have been ideal but it was useable, factory loads came with bullets from 110 grains to 220 grains. Using a slower twist might have meant giving up the long heavy bullets beloved by moose, elk and large bear hunters.




Most of the old military round nose bullets from the 1890s were very heavy, 220 grains for the .30 Krag and .30-03, 215 grains for the British .303, 175 grains for most of the 7mm and the already mentioned 155-160 for the 6.5mms. Yes a modern 140 grain 6.5mm match bullet is longer than the old round nose but then you can drive it several hundred FPS faster. Please note that the really long spitzer boat tails only date from the 1990s or so. Like Serrias 107 being longer than the 120 or the 142 being longer than the discontinued (?) 155.
The shorter 120 grain HSBT and 140 HSBTs have shorter boat tails and less pointy ogives and perhaps less empty space in the nose. In any case a military SBT of WW II vintage would have the lead inserted from the rear and would have no hollow cavity (or perhaps a filler) in the nose.
While not ideal from a 2018 point of view Such bullets were an advance over plain base spitzers and would work perfectly well out to any distance a regular rifleman or even bipod machine gun would be expected to work at.
The art of bullet making has advanced an awful lot in the last century or more. More uniform jacket thickness, more uniformity in weight (old match shooters in the 1930s would weigh their bullets and sort them, weighing modern match bullets is an exercise in futility) and more uniform shape.
A slight excess in twist helped make up for some of those differences.
Most military ammunition of WW II was doing very good if it could shoot 2 minutes of angle, some of it couldn't hold 3 minutes of angle, mostly due to the bullets, tricks like 30 degree shoulders, small primers and the like are not going help poor bullets.
They could have made ammunition with better ballistics without new technology, but they also needed to able to produce the cartridge cases, primers and bullets with existing knowledge and tooling ability and make them by the 10s of millions.
 

The only intended common features with the 6.5 Lapua would be the shape and approximate length of the cartridge case.
Primer sizes and pressures would be more common with something along the lines of a 7.92 x 57 or .308 Winchester.
Cartridge OAL would be considerably less than the .308W considering that a conventional spitzer bullet design would be used instead of a modern VLD design.


The kind of muzzle brake I had in mind would be along the lines of the AVS-36 or AK-74 which might have some effect on recoil
The Cutts Compensator on the Thompson and various shotguns isn't very sophisticated and really only addresses muzzle climb which is quite appropriate considering that the typical M1927 Thompson weighs around 18 pounds with a loaded 50 round magazine.
Many items were deleted with mass production. Among them were the Blish lock, cooling fins, drum magazines, and top mounted operating handle, but those older guns were beautiful if not efficient.


There was a fellow who did a test many years back with faster and faster rifling and how it affected pressures.
The general conclusion was that for all practical purposes, the pressure differences due to rifling twist were less than the shot to shot variation in chamber pressures. I have never worked out the exact numbers, but the amount of rotational energy in a bullet is extremely small in relation to the translational energy.
Your comparison between a Palma match gun and a M14 service rifle is entirely unfair. The Palma gun typically has a 30 inch barrel and as you noted operates over the SAAMI specification for the .308 Winchester. The M14 is gas operated and uses a 22 inch barrel.

Also, the 600 yard slow fire stage is not a reasonable example of ammunition suitable for a M14 because most of the time that ammunition will not even fit into the magazine and will not cycle through the gun in semi auto. To me that is pure game and regardless of what it is called has nothing to do with a military rifle. Heck, one could get away with a lot of Benchrest techniques such as very fragile ammunition and indexing cases if you know the ammunition will be fired that way! I actually have played around quite a lot with the M14 type platform and would be glad to discuss, but it seems off topic here. I will warn you in advance that my philosophy is quite different from the typical High Power shooter.

Since you picked the .30-06 as an example, do you see any advantage to having a 1-12 inch twist in that caliber as opposed to 1-10 inch twist that is standard these days?

As for a "fast" rifling twist, there are quite a few calibers / platforms that use a fairly fast twist and are quite successful.
The AR-15 / M16 series started with 1-14 inch in prototypes which actually exhibited rather poor accuracy and then went to 1-12 inch with the M16 / M16A1 and went to an even faster 1-7 inch twist with the M16A2. My own experience is that the 1-7 inch twist is the best among those choices for accuracy though for pure target use, I would probably go with 1-9 inch.
The 6.5 mm Swedish Mauser typically is rifled at 1-8 inch or 1-8.5 inch and has a great reputation for accuracy.


Much of what you are describing is relevant only on the target range. At this point in time, there was no JAG to determine that a HPBT bullet does not violate the terms of the Hague Convention. Bullets would be full patch open base spitzers.
The idea of a bullet that was long for its caliber was already done by the British by putting an aluminium spacer in the front of their bullets and later by the Russians by placing the core in such a manner as to leave an air space at the nose.

As for a basic rifle cartridge design, this was intended to be a ballistic clone of the 6.5 mm Swede but with a few "modern" changes.
The case would be shorter, have a sharper shoulder, and use spitzer bullets. While I agree that a sharp case shoulder may not improve the accuracy of military ball ammunition, it also does not cost anything in performance either, so why not build in the potential for better accuracy using the same cartridge in something like a sniper rifle and long range potential for a similar LMG?

- Ivan.
 
A lot of the bench rest stuff in case design only comes into play when you get the accuracy well under 1 minute of angle to begin with. When I had the short case rifle built I asked the gunsmith about turning the case necks and getting a chambering reamer to suit. He told me it was unnecessary unless you looking at under 1/2 minute of angle. So it was built to take 6mm BR cases necked up with no case turning. The gun is stunningly accurate and you can pick what part of the X ring you want to shoot up at 300yds (MR-63 target 2.85in X ring) and then give the sight a couple of clicks and shoot up another part of the X ring. Personal best was 26 consecutive Xs.
26 in Barrel, 30.5 grains of 4895 (thrown charges) behind the 120 Grain Sierra. MV was just about 2600fps. So yes you don't need the big cases unless you are looking for high performance.

The 260 Remington will shoot 120 bullets at about 2900fps and 140s at around 2700-2750fps.

Boat tail bullets date back to before the turn of the century and there is no reason not to use at least a modest boat tail on an "ideal" rifle round.
 
Hello Shortround6,
I suspect that in general we would be more in agreement regarding rifle accuracy that it appears from this discussion.

When folks started shooting the M14 in service rifle competition in place of the M1 Garand, they gradually noticed that the scores were higher on average than they were back in the days of the Garand. Some folks thought it was because the M14 was an inherently more accurate rifle (when tuned). Other folks were noted that the Navy was shooting just as high scores with re chambered M1s, so their conclusion was that it was a difference in inherent accuracy of the new cartridge.
This is a story I have heard a couple times. I obviously was not around during the period in discussion and proving it would be difficult, but I tend to believe it.

We all know there are some cartridges that develop a reputation for accuracy and others that do not. I also believe there are very few cartridges that absolutely prohibit excellent accuracy, so given just about any cartridge, someone is bound to find an example of a gun that shoots amazingly well. I see no point in not designing in all the advantages we can from the start if we are starting on a brand new design.

The process of neck turning cases does not really fall into Benchrest case design but more into case preparation. I would tend to agree with your gunsmith regarding chambering to fit ONLY neck turned cases, though there is nothing actually stopping you from neck turning your cases anyway. I actually do quite a few of the one-time Benchrest case prep even for semi autos. It is also part of my initial case inspection.

How well does your 6.5 mm target gun actually do from a MOA standpoint at close range? Obviously it is sub-MOA out to 300 yards or more.
Now keep in mind that as a target shooter that reloads, you have the luxury of loading down a bit for short range while the military cartridge we are discussing is a single standard rifle load for all ranges. You are also probably using VLD bullets which fly a bit better than the boat tail spitzers of the pre war era. I had been figuring about 35 grains of powder pushing a 140 grain bullet to around 2600 fps to 2650 fps from perhaps a 22 inch barrel.
Perhaps we should really take this into another thread?
My own loads for the M14 / M1A are just about anyone's 168 grain HPBT Match (I used a lot of Hornady's because I got them cheap) with either IMR 4064, W748, or IMR 4895 and match or BR primer. Exact powder charge varies slightly but runs about 43.5 grains or 42.5 grains or so depending on lot of powder to push bullets to around 2625-2640 fps for 7 foot instrumental velocity.
My basic idea is to duplicate the Federal .308 Match load or M852 and this combination seems to do it pretty reliably.
The only big gotcha is NOT to use standard Federal rifle primers. It doesn't seem to matter so much with the M1A / M14, but with other semi autos, they will cause slam fires. The same thing does not seem to happen with Federal Match primers.

- Ivan.
 
Well, trying to back on track, you can duplicate (or come darn close) the ballistics = trajectory/wind drift of the .308 NM Load with a 6.5 using a BT bullet of between 120-130 grains and not a VLD either.
You can certainly duplicate the 7.62 NATO with it's 147-150 grain bullet and skimpy BT. Original goal of the .308 was to duplicate the .30-06 M2 load which used a 150 grain flat base bullet.

Now going back to our "Ideal" rifle we would be smart to ask what we want it to do. Unlike the US which asked for a rifle of the power of the M-1 Garand with the M2 ball, weighing 2lbs less than the M-1 and firing full auto to boot (and with 20 round magazine), an obvious recipe for disaster

Most people consider the German StG 44 and AK 47 as too short ranged to be "ideal" even though they were a good compromise. They did a number of studies and found that about 50% or rifle use was at 200yds or under and something like 95-98% was under 400 yds (could be meters?). The problems come in when the same/similar studies came up with 50% of machine gun use being over 400yds/meters so you can't use the short range rifle cartridge in the squad/company machineguns. You also have to be careful about designing to "averages" as that means you are going to be at a varying degree of disadvantage 50% of the time. How far you tip to one side or the other is the big question.

Giving every trooper a 1000yd rifle isn't a really good answer as very few troops can really make any use of such a rifle at that distance or indeed hundreds of yards short of that distance. However the StG 44, AK 47 and M-16 can leave the troops with little in the way of effective return fire should the ranges open out to 400 yds or beyond.
We could try to define a 'danger' space, like a distance above and below the line of sight that our "soldier" could hit without changing the sight (battlesight range), we could also see what might be an acceptable amount of wind drift at a given range.
We may find that 500-600yd effective range is all that is needed or perhaps all that is obtainable without sacrificing something else.
By going to the 6.5mm caliber and adding about 300fps to the 7.62x39 we can get much better long range ballistics without a major increase in recoil or even a major increase in raw materials for the cartridges.
In a 10lb (empty) rifle we may even get somewhat useable full auto fire with a modest muzzle brake.
 

The 6.5mm Grendel is basically the Russian cartridge with new, fast bullet.
Gossips have it that Serbians are moving to the Grendel for their new rifle. Makes plenty of sense - for a slight change of tooling they will get a far more accurate rifle, especially past 300 m. Less susceptible to the wind drift, too.
 
The 6.5 Grendel is interesting, I may build one day as I have a mini-mauser in 7.62x 39 and the old barrel from the 6.5 x308 that can be cut off and rechambered.
However the 6.5 Grendel and 6.9 x43 SPC show the limitations of legacy weapons development.

Because both cartridges are limited in overall length so as to fit AR-15 magazines and magazine wells they are limited in bullet length (ballistic coefficient) or long bullets suck up powder space.
With a clean sheet of paper gun both cartridges could use high ballistic coefficient bullets and have more volume for powder.
 
The 6.5mm 'lineup' picture: link
6.5mm Creedmoor offers ~20% greater muzzle energy than the 6.5mm Grendel, quirk being that your national miltary rifle factory will indeed have to came out with a brand new rifle & tooling for that rifle to use the 6.5mm Creedmoor.
An interesting round for 'our' rifle might've been the .25-3000 Savage, but using a heavier (110-120 gr) bullet rather than the light & fast one (75-90 gr).
 
The .250 Savage is a nice hunting round and is rather underappreciated now. However as a military cartridge, especially for a large capacity magazine is has more taper in the body than may be desired. Not as bad as the .303 or the 7.62 X 54 rimmed rounds.
It also uses the same rim/body diameter as the 30-06 and 8mm mauser.
Using a skinnier body may allow you to fit 11 rounds in the space of 10 or even a bit more in a double column magazine or make your 20 round magazine a bit smaller. Whether this is of any practical difference I don't know
The .250 Savage is one of the cartridges that made P O Ackley's reputation. When he modified it he not only changed the shoulder angle he took out a lot of the body taper and gained most of the increase in powder capacity that way. With the available powders of the time he came pretty close to the max ballistics you could get in a .25 cal bore. The Bigger .257 Roberts and .25-06 used a lot more powder for very little increase in velocity. Post-war the story changed with the greater availability of slower burning powders.
 
Hello Gentlemen,
I don't mind a discussion of the merits of rifle cartridges but neither the 6.5 Creedmoor or the .250-3000 really fit in with the available technology or the proper parameters of a general issue military rifle cartridge in my opinion.
Shortround6, your comment about the excessive taper of the .250-3000 is interesting because there have obviously been much more tapered rounds that have been quite successful in military rifles and automatics: the .303 British and 7.62 mm x 39 being very prominent examples.

As I see it, a cartridge with the powder capacity of the .250-3000 would just about guarantee a fairly short barrel life especially for a full automatic.
The 6.5 Creedmoor also seems to me to be too much case capacity and pressure and overall length for the caliber, especially considering that VLD bullets would have been a pretty radical departure in technology for the time.

Hello Shortround6,
I believe in general, we are pretty close in agreement but for about 100 fps muzzle velocity and 10-20 grains of bullet weight.
I was getting pretty specific about cartridge shape but realistically these are features that can be added to anything without changes to the basic performance parameters.

I agree that there is no reason to ensure that every infantry rifle be capable of 1000 yard accuracy, but there is also no reason to ensure that the standard infantry rifle be incapable of effective fire at 1000 yards either.
My basic reason for selecting a 140 grain 6.5 mm bullet was for terminal effect on the target. Although a lighter bullet may still be accurate at a distance, there needs to be some minimal bullet mass for wounding effect because the retained velocity will be fairly low.
I was hoping for an effective range of at least 600 yards and closer to 800 yards if possible.
The main reason for wanting 2600-2650 fps muzzle velocity was to ensure a relatively flat trajectory that was at least comparable to the .30-06 M2 Ball.
The M1903 Springfield had a battle sight zero of 275 yards (?) for a maximum point blank range of 550 yards and I would hope that its replacement could achieve similar results. I do not have a ballistics program to check, but the velocity should be sufficient so that the midrange trajectory out to 550 yards with a 140 grain bullet should be no more than 30 inches but with a flat base bullet.
The reason for checking ballistics with a flat base bullet is that computer programs tend to be somewhat optimistic and real world ballistics tend to be not quite as good. When this is combined with less than match grade barrels and military production bullets, things may get a bit worse than expected.

Now with a higher recoil round, the controllability of full automatic fire might be a bit worse, but keep in mind that full auto fire from a rifle is not really a long range proposition. Also, there are other factors that can compensate for recoil to an extent: muzzle brakes, straight line stocks, and even a reduction in cyclic rate. Given a choice between effective range and lethality versus easily controlled full auto fire, I believe range and lethality are more important but it is really a balance and subject to opinion.

Regarding lethality: As I have heard from folks and found in articles, the AK-47 round is really somewhat inadequate for stopping power; There are a lot of guys who have been shot with AK's and are still walking around. My own experience on the firing ranges suggests that the AK-47 bullet (125 grains at 2350 fps) really doesn't penetrate all that well. It is the only common rifle bullet besides black powder and .22 rimfire that can be found on the surface of the backstop after it has rained. Other rifle bullets dig themselves much deeper.
Bottom line is that although the 7.62 x 39 functions well in an assault rifle, it really is a bit under powered.

- Ivan.
 
If you love 6.5mm Japanese but want a handy rifle then the Arisaka Type 44 with folding bayonet is your poison.
Better than a AK for 600 metres.
 
In regards to cartridge taper, the thread title does say "ideal".

The .303 was a legacy cartridge (like the 8mm Lebel and the 7.62X 54 Russian) the .303 was originally loaded with black powder in 1888 was only 9 years out from the rolled brass foil and iron head .450/.577 Martini–Henry Ammo that famously jammed if looked at wrong.
The science/technology of drawn cartridge cases advanced quite a bit from the 1890s to the 1930s and even more today. Likewise propellants (British had problems with cordite causing higher pressures in hot climates than nitrocellulose powders) which meant the "ideal" cartridge shape of 1890-95 may very well be not the same "ideal" cartridge shape of 1938-39 let alone today. Brass in general, has more 'spring' that steel. That is to say it will expand more and shrink back more than the soft steel used in military cases (this assumes good quality brass, not always the case in war time ammo). The taper used on the 7.92 X 33 and 7.62 X 39 may be due to the planned use of steel cases and the desire to minimize extraction problems in hot guns (full auto) using such cases. Or not, it may have been due to the conservative members of the selection committee.

Tapered cases have been used, doesn't mean they are "ideal" but then really straight cases may present a few problems of their own.

The .250-3000 has somewhat less powder capacity than the .308 Remington and in fact is about 1/2 way between the 6.5 Grendel and the .308.
My short 6.5 had about 10% more capacity than the Grendel.

Here is picture of some bullets.

Scrapping the VLD form for the WW II era we can see that the 6.5mm 120 has about the same or better sectional density that 147-150 grain .30 cal bullets and should have similar penetration (at least in soft stuff). The 140 doesn't give enough recoil reduction and needs a quicker twist and has more bullet length in contact with the bore (more friction). If we want full auto, even as a sometimes option, dropping bullet weight 10 grains (6-7%) isn't going to do it even with a muzzle brake.
The 120 will give a 20% reduction and will hit at any practical range (including 1000 yds) with about 75-80% energy of the .30-06 150 grain load.
At some ranges (700-800yds) it will hit with twice the energy of the 7.62 X 39.

Yes the 140 will do even better but what are you giving up to get it?
 
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