In the aftermath of World War II, the United States spent 12 years looking for a successor to the M1 Garand rifle. The new standard infantry arm was expected to be select-fire, lightweight, accurate, controllable, and fire a heavy .30-caliber projectile. It would replace not just the M1, but also the BAR and perhaps the M1 Carbine as well – a true universal weapon. Of course, these requirements were complete fantasy, unachievable in the real world – but that did not prevent Remington, Springfield Arsenal, and Winchester from trying to meet them.
This rifle is a Winchester prototype, which has been substantially lightened from the M1 it began life as. A pistol grip has been added, along with a fire selector lever and a box magazine system. A detachable lightweight bipod allows it to be used for supporting fire. I do not know exactly when it was made, but it is chambered for the T65 or 7.62 NATO cartridge, which dates it as definitely post-WWII.
Thanks to the Cody Firearms Museum for allowing me access to film it!
That big flash cone on the bipod doesn’t block the front sight?
The cone flash hider on the M1 carbine sure does… Designed for the M3 infrared sniper intended for use during Coronet and Olympus in fall/winter 1945 on Kyushu and the Kanto plain of Honshu…
There is lot of common sense touches on this design (namely straighter operating rod and mag over-travel). The progress from M1 is clearly evident.
Location of magazine latch seems amazing. Wonder who thought it.
” Of course, these requirements were complete fantasy, unachievable in the real world â but that did not prevent Remington, Springfield Arsenal, and Winchester from trying to meet them.”
I can only wonder how much of a role politics must have played in the military’s decision to turn a blind eye to the whole assualt-rifle concept in the post WWII period — until being basically forced to adopt it due to the hard-learned lessons of upcoming battlefield realities. As the big firearms manufacturers were already heavily invested in and tooled up for producing traditional battlefield rifles, they no doubt would have argued adamantly that these traditional ‘full-power’ rifles were still the ideal choice for the future. The M14 boondoggle was therefore just more money for their pockets.
“I do not know exactly when it was made, but it is chambered for the T65 or 7.62 NATO cartridge, which dates it as definitely post-WWII.”
Would it be fair to say that it was probably designed and built the mid 1950s?
“As the big firearms manufacturers were already heavily invested in and tooled up for producing traditional battlefield rifles, they no doubt would have argued adamantly that these traditional âfull-powerâ rifles were still the ideal choice for the future. The M14 boondoggle was therefore just more money for their pockets.”
Still, it should be possible to make rifle for smaller cartridge, but manufacturing with usage of known technologies and machines.
Something externally similar to Ruger Mini-14 (which of course, would need true intermediate cartridge developed first).
After some thinking: there was .25 Remington Auto-Loading hunting-cartridge which should work well as inter-mediate cartridge.
Ha! Great post… Of course, this was another unsung Soviet designer’s point: That an “ideal infantry rifle cartridge” already existed… In the .25 Remington! Let us see: a 6.54mm/ .2575-in. 7g/100-gr. bullet going 2330/2400fps/710ms and developing something like 36k PSI chamber pressure, and with 1 turn in 8-in. rifling…
Bring on the 6mm SAW cartridge! đ
“That an âideal infantry rifle cartridgeâ already existed⊠In the .25 Remington!”
No, it was not considering unconditionally ideal, but closest to ideal from existing cartridges.
http://www.bratishka.ru/archiv/2011/11/2011_11_6.php states that:
Đ ĐĄĐŸĐČĐ”ŃŃĐșĐŸĐŒ ĐĄĐŸŃĐ·Đ” ŃДлДŃĐŸĐŸĐ±ŃĐ°Đ·ĐœĐŸŃŃŃ ĐżĐ”ŃĐ”Ń ĐŸĐŽĐ° ŃŃŃĐœĐŸĐłĐŸ Đ°ĐČŃĐŸĐŒĐ°ŃĐžŃĐ”ŃĐșĐŸĐłĐŸ ĐŸŃŃĐ¶ĐžŃ ĐœĐ° ĐŒĐ”ĐœŃŃĐžĐč, ŃĐ”ĐŒ ŃŃŃĐ”ŃŃĐČŃŃŃĐžĐč 7,62 ĐŒĐŒ, ĐșĐ°Đ»ĐžĐ±Ń Đ±Ńла ĐœĐ°ŃŃĐœĐŸ ĐŸĐ±ĐŸŃĐœĐŸĐČĐ°ĐœĐ° Đ.âĐ.âĐ€Đ”ĐŽĐŸŃĐŸĐČŃĐŒ ŃжД ĐČ 1939 ĐłĐŸĐŽŃ, ĐșĐŸĐłĐŽĐ° ĐŸĐœ пОŃĐ°Đ», ŃŃĐŸ ĐŽĐ°Đ»ŃĐœĐŸŃŃŃ ĐżŃŃĐŒĐŸĐłĐŸ ĐČŃŃŃŃДла «пŃĐŸĐŒĐ”Đ¶ŃŃĐŸŃĐœĐŸĐłĐŸÂ» паŃŃĐŸĐœĐ° ĐŽĐŸĐ»Đ¶ĐœĐ° бŃŃŃ ĐœĐ” ĐŒĐ”ĐœŃŃĐ”, ŃĐ”ĐŒ Ń ŃŃĐ°ŃĐœĐŸĐłĐŸ ĐČĐžĐœŃĐŸĐČĐŸŃĐœĐŸĐłĐŸ паŃŃĐŸĐœĐ°. ĐĐ»Ń ŃĐœĐžĐ¶Đ”ĐœĐžŃ ĐŒĐ°ŃŃĐŸ-габаŃĐžŃĐœŃŃ Ń Đ°ŃĐ°ĐșŃĐ”ŃĐžŃŃĐžĐș паŃŃĐŸĐœĐŸĐČ ĐŸĐœ ĐżŃДЎлагал ŃĐŒĐ”ĐœŃŃĐžŃŃ ĐžŃ ĐșĐ°Đ»ĐžĐ±Ń ĐŽĐŸ 6â6,25 ĐŒĐŒ. ĐŃĐ” ĐČ 1945 ĐłĐŸĐŽŃ Đ.âĐ.âĐ€Đ”ĐŽĐŸŃĐŸĐČ ĐČ ŃĐČĐŸĐ”Đč ŃĐ°Đ±ĐŸŃĐ” «ĐŃŃĐ»Đ”ĐŽĐŸĐČĐ°ĐœĐžĐ” ĐŽĐ°Đ»ŃĐœĐ”ĐčŃĐžŃ ĐżŃŃĐ”Đč ĐżĐŸĐČŃŃĐ”ĐœĐžŃ ŃŃŃĐ”ĐșŃĐžĐČĐœĐŸŃŃĐž ŃŃŃДлŃĐ±Ń ĐžĐ· ŃŃŃДлĐșĐŸĐČĐŸĐłĐŸ ĐŸŃŃжОŃ» ĐŽĐŸĐșĐ°Đ·ŃĐČĐ°Đ», ŃŃĐŸ ĐœĐ°ĐžĐ±ĐŸĐ»Đ”Đ” пДŃŃпДĐșŃĐžĐČĐœŃĐŒ ŃĐ°Đ·ĐČĐžŃОД Đ°ĐČŃĐŸĐŒĐ°ŃĐžŃĐ”ŃĐșĐŸĐłĐŸ ŃŃŃДлĐșĐŸĐČĐŸĐłĐŸ ĐŸŃŃĐ¶ĐžŃ ŃŃĐ°ĐœĐ”Ń ŃĐŸĐ»ŃĐșĐŸ ĐČ ŃĐŸĐŒ ŃĐ»ŃŃĐ°Đ”, Đ”ŃлО бŃĐŽĐ”Ń ŃĐ°Đ·ĐČĐžĐČĐ°ŃŃŃŃ ĐČ ŃŃĐŸŃĐŸĐœŃ ŃĐŒĐ”ĐœŃŃĐ”ĐœĐžŃ ĐșалОбŃĐ° паŃŃĐŸĐœĐŸĐČ.
–
In Soviet Union reasonability of changing caliber of hand automatic weapon to smaller one, that current 7,62-mm, was based on scientific research by V.G.Fyodorov as early as 1939 year – he wrote that ĐŽĐ°Đ»ŃĐœĐŸŃŃŃ ĐżŃŃĐŒĐŸĐłĐŸ ĐČŃŃŃŃДла* of “intermediate” cartridge should be no less that rifle cartridge [7.62x54R]. For lowering mass-dimensions characteristics they should be of 6-6,25mm caliber**. In 1945 V.G.Fyodorov in «ĐŃŃĐ»Đ”ĐŽĐŸĐČĐ°ĐœĐžĐ” ĐŽĐ°Đ»ŃĐœĐ”ĐčŃĐžŃ ĐżŃŃĐ”Đč ĐżĐŸĐČŃŃĐ”ĐœĐžŃ ŃŃŃĐ”ĐșŃĐžĐČĐœĐŸŃŃĐž ŃŃŃДлŃĐ±Ń ĐžĐ· ŃŃŃДлĐșĐŸĐČĐŸĐłĐŸ ĐŸŃŃжОŃ» argued that, most perspective development of machine fire-arms will be attained if and only if, it would be developed in direction of reduction of caliber.
* – I don’t know American parlance, generally that mean it should shot as least as flat
** – that is in Russian style, that is referencing inner barrel diameter lands.
“Bring on the 6mm SAW cartridge!”
Development of intermediate Soviet cartridge in 1940s several proposed were tested, you can read about some here:
http://tverskiepartizani.ru/index.php/articles/109-puma
In early ĐĐĐ-44 got few orders for research in area of intermediate cartridges.
2nd image from top: various experimental Soviet inter-mediate cartridge between 7.62x54R Mosin (1) and 7.92 Kurz (10) and 7.62×25 Tokarev (11)
In bit of correspondence from йХ ĐĐĐ [Technical Commission of People’s Commissariat of Armaments] to director of ĐĐĐ-44 (April 1945) there is mention 6,75-mm cartridge designed by Blagonravov and described 6,75-mm cartridge designed by Fyodorov, which has ballistic as follows:
caliber 6,75-mm
bullet mass 7 g
muzzle velocity 790 m/s
ĐŽĐ°Đ»ŃĐœĐŸŃŃŃ ĐżŃŃĐŒĐŸĐłĐŸ ĐČŃŃŃŃДла (ĐĐĐ) 380 m
average maximal pressure 2800 kg/cm2
barrel length 620 mm
In October 1945 there was decision to do ballistic research with cartridge in table and to send blueprints of cartridges and chambers to ĐĐ-2 for evaluation of its suitability for carbine, avtomat, hand-held machine gun which would fulfill ййй ĐĐĐŁ (Technical Tactical Requirements [of] Main Artillery Directorate) from 05.12.1945
Table:
Main cartridge characteristics:
Columns from left: “rifle” [7.62x54R], 8 x various experimental cartridges
Rows from top:
Caliber, mm
Average bullet mass, g
Average cartridge mass, g
Case base diameter, mm [two rows]
Cartridge length, mm
Barrel length, mm
Muzzle velocity, m/s
Maximal average pressure, kg/cm2
Bullet energy, kgm:
-muzzle
-at distance 1000m
ĐĐĐ, m [bigger=better]
Recoil impulse, kgs.s [less=better]
Notes: all cartridge have bimetallic cases, bullets with steel cores (excluding “rifle” and Đ5). Characteristic of 7.62x54R are only for comparison. Recoil impulse was calculated retroactively – such index was not used in 1945. ĐĐĐ for target height 0,4
Notes from 8.07.1947 considering cartridge seen in table:
Đ1: lighter bullet that 7.62x54R, equal ĐĐĐ, but also similar size
Đ2: equal ĐĐĐ, lighter and smaller thanks to smaller caliber
Đ3: worse ĐĐĐ than Mosin rifle but better than model 1944 carbine, smaller that Mosin cartridge, bigger that pattern 1943
Đ4: ĐĐĐ similar to model 1944 carbine, shorter and lighter than rifle cartridge
Đ5: same as Đ4 but with lead-core bullet of bit different shape (hence bit longer)
Đ6: created for blow-back weapons, smaller and lighter than pattern 1943. ĐĐĐŁ [Main Artillery Directorate] consider that building such weapon, which would be accurate enough to be impossible
Đ7: variant of pattern 1943, different bullet shape, iron core instead of lead core. Dimensions, mass and ballistic without alterations
[pattern 1943 should be considering as 7.62 pattern 1943 cartridge here]
Đ8: light bullet trial for short distance, was not allowed into proving ground tests due to lack of bullet fly stability.
First three were proposed by Fydorov.
They were testing at proving ground, but not from automatic weapons, so lighter cartridge don’t shows fully their advantages.
All were fired from 520 mm barrels. Most accurate were: Đ2, Đ3, Đ7.
Proving ground conclusions:
Đ1 is similar to current rifle cartridge [7.62x54R] and has gives no advantages
Đ4 and Đ5 are bigger than pattern 1943 without ballistic advantages, they have no perspective
In area of reducing caliber there are several things not tested deeply enough (killing ability, special bullets and others) so it must noted that ballistic-enhancement-via-caliber-reduction might have perspective, but need more further serious experimental research. Without said research cartridges Đ2, Đ3, Đ6 can not be adopted. Considering that pattern 1943 should be adopted and further refined.
[In this context “special bullets” mean armor-piercing-incendiary, tracer or incendiary]
is: “(…)ĐĐĐ for target height 0,4(…)”
should be: “(…)ĐĐĐ for target height 0,4 m(…)”
Very interesting! Hopefully a translation will be forthcoming… Maybe a book on Russian/Soviet developments and research that is more widely available and less expensive than D.N. Bolotin’s.
I refer to Anthony G. Williams’ description of one V. E. Markevich, possibly a minion or mentee of FĂ«derov who made the assertion in 1930 that the .25 Remington possessed the necessary attributed of lighter weight, flat trajectory, lower recoil, and so on for an “ideal” individual infantry weapon cartridge. Spacibo for the insights!
One could make the argument that the US Army was an early adopter of the assault rifle, and as early adopters sometimes go, a bad first taste turns them off for a while. The M1 Carbine fits most definitions of what an assault rifle is. Light, compact, cartridge bigger than a pistol but smaller than a battle rifle, full-auto capable (fielded before WWII ended), detachable box magazine, and even folding stock variations. But what “everyone” said about the M1 Carbine was that it had poor stopping power.
In reality, not everyone said that, and a few war heroes and experienced shooters (e.g., Audy Murphy and Col. Charles Askins) liked it. Col. Askins liked killing people, so if he liked it then it must have gotten the job done. But the negative reports drowned out the positive and the experience with the M1 Carbine confirmed the original idea that it was to replace pistols for non-infantry roles, and it was not meant to be a front line weapon.
So the US Army insisted on retaining the power of the .30 caliber. The .308 delivered the same power as the .30 caliber by using better propellant in a smaller case. What held back post-war rifle design was the insistence in keeping the rifle power at .30 caliber levels. If one insists on battle-rifle power cartridges then all one can really accomplish is a marginal improvement of battle-rifles, hence the M-14 (and FAL).
If the M1 Carbine had been specified to use a true intermediate cartridge (and not what is basically a magnum pistol cartridge) then history may have turned out differently.
Battle rifles are generally NOT supposed to be used in close quarters battles (trenches, forests of all possible climates, and worst of all, city-scape) where assault rifles, SMG’s, and melee weapons dominate. The US Army wanted to retain “stopping power” in order to out-range and simultaneously overpower whatever the other team carried. To ask for a selectively automatic weapon of such a caliber also asks a bit much of the individual rifleman’s upper body muscles! Unless your enemies are charging carelessly across open plains in tight formations of 100 man squares, forget plinking and call in the artillery!
Did I mess up?
” M1 Carbine fits most definitions of what an assault rifle is.”
I would rather say that M1 Carbine in its full-auto-capable version is in fact sub-machine gun, with exception that it don’t use default automatic pistol used at that time. But more importantly it was not supposed to replace M1 Garand as main infantry rifle.
is: “(…)automatic pistol used(…)”
should be: “(…)automatic pistol cartridge used(…)”
Single best “hand gun” fielded by any combatant of the Second World War…:) đ
No real “replacement” ever occurred, however. Just one more caliber, cartridge and weapon to increase the already prodigious logistics train of the U.S. Armed forces…
At the end of WWII, the only American “big firearms manufacturers” tooled up for large-scale production of full-size semi-auto military riles were Winchester and the government Springfield Arsenal. The M1 Garand required a lot of special tooling and know-how (e.g., the op-rod as mentioned by Ian). If anything, a less-complicated design would have been more popular with the manufacturers and it would have been irrelevant if that design was big or small. Many more companies made M1 Carbines during the war, so if anything, an enhanced carbine would have had more industry support.
The reality was that whatever was adopted, it was a given that arms companies would have contracts to make them and the government paid for the tooling. Post-war there was the concern that a single nuclear bomb could take out important areas (like Springfield Armory), so there was a push to spread out the procurement of arms to different parts of the country. When the FAL was almost adopted, private arms companies were preparing to gear up for it and they were less concerned about the design as they were that the plans were originally in metric.,
aa,
“Would it be fair to say that it was probably designed and built the mid 1950s?”
The flash hider and bipod is the one patented here by Harry Sefried:
https://www.google.com/patents/US2420267
Filed in 1945, so designed sometime before that. Not sure when the conversion to .308 Winchester might have happened. It would be interesting to know if the shortening of the .30-06 might have been prompted by the need for extra dwell time in a full auto M1 Garand. ^__^
[i]âI do not know exactly when it was made, but it is chambered for the T65 or 7.62 NATO cartridge, which dates it as definitely post-WWII.â
Would it be fair to say that it was probably designed and built the mid 1950s?[/i]
In 1954 Beretta started producing M1 rifles using the ex-Winchester tooling, so Wincester had no more the capacity, nor the will, to build them.
“But what âeveryoneâ said about the M1 Carbine was that it had poor stopping power.”
Perhaps it’s quite a coincidence –or maybe not– that the latest evolution of Soviet assault-rifle development, the 5.45x39mm, has almost exactly the same energy as the .30 Carbine.
“What held back post-war rifle design was the insistence in keeping the rifle power at .30 caliber levels.”
The same could have been said a century earlier — just replace “.30 caliber” with “muzzle loader” because it was a similar situation: the U.S. military, in both the 19th and 20th centuries, when it came to arming regular infantry and cavalry, apparently put a much higher priority on “knockdown power” and range than on rapid-fire performance, and as new arms technology developed, tended to steadfastly hold on to their traditional ideals rather than adjust them to fit the new realities of the era.
So when fixed cartridges emerged, single shot breechloaders were chosen over (reduced-power) repeaters. Then many decades later, full-power cartridges in full-auto rifles –awkward as they were– were chosen over reduced-power cartridges.
Just as the post-Civil War Army never sought to develop the repeating rifle into a weapon with better range for front-line troops, neither did the post WWII military with the .30 carbine.
Well, that’s just a possibly-gross simplification of a complex issue.
Alas, in both cases, the old order tried to force its way into being permanent.
Rationalization for powerful single-shot weapons: lots of punching power and range (Minie balls were pretty nasty), saving money by using conversions of well-known weapons as templates for future use (Trapdoor Springfield rifles), and saving on ammunition procurement (to say nothing of the bitter taste left by the prone-to-harming-user Colt cap-lock revolving rifle). The training of the day? “One shot per soldier, one kill per soldier.”
Rationalization for powerful battle rifle: lots of punching power and range (compared to the PPSh-41 used in close-quarters spray attacks), supposed tactical flexibility, using familiar design (M1 rifle action) and waiving development of new ammunition. And the top brass in America and in Britain dismissed the STG-44 as a “stupidly-easy-to-bend-out-of-shape piece of crap requiring a less-than-lethal-at-battle-range cartridge.” 8×33 Kurz isn’t intended for half-mile one-shot-kills, you know.
In other words, the US Army had an obsession with wanting Magnum force compared to anything from the other team.
Did I mess up? SAY SOMETHING!!!!
I’d say it’s a concept that probably goes all the way back to the musket era, when guns took so long to reload that there was really no advantage in having anything less than “full power” caliber and loadings, so long guns were designed to pack as much wallop as possible from a shoulder-fired weapon.
Phychological factors can’t be dismissed either, as there’s a certain amount of chest-thumping machismo involved in shooting a very powerful round. Just look at the popularity of the .500 S&W Magnum revolver, a purely macho status symbol without any valid reason to even exist otherwise.
I badly need to check my spelling before hitting ‘post’. đ
There’s also the human tendency of linear thinking, especially among the most educated and experienced in the subject. Just as most everyone (middle-age and up) once said “the car will never replace the horse” and most every computer professional swore that “the PC will never replace the mainframe” — the same was probably said about intermediate rifle cartridges.
Just inertia of thinking.
“500 S&W Magnum revolver”
I consider it as marketing gimmick – 2nd most powerful production revolver in world (after Đ Đš-12)
There is one practical reason for the.500. The one it was ostensibly developed for: Grizzlies.
Is the .500 S&W really significantly more effective grizzly bear gun than the .460 S&W or even its predecessor, the .454 Casull?
Perhaps for a highly practiced shooter, of large stature, and with experience shooting in high-stress situations — and someone who rarely misses– the .500 S&W might work fine.
But for other people, that flinch-inducing magnum might be among the worst choice when suddenly facing an angry bear within pouncing range. People who tend to get shaky hands when forced to fire a gun under extreme stress (and real-world evidence shows that’s a rather high percentage of us) might do better with something with more manageable recoil that might better allow follow-up shots.
Of course, it’s all just pure speculation, without suitable statistics that might help gauge the overall effectiveness of one gun relative to another in actual bear vs. man situations, perhaps similar to the way that the FBI recently judged the .40S&W against the 9mm luger, and decided that bigger does not mean better.
What about .500 S&W vs .475 Linebaugh or .480 Ruger?
“There is one practical reason for the.500. The one it was ostensibly developed for: Grizzlies.”
After some thinking I must admit it might be useful as double purpose rifle/carbine and revolver cartridge. Preferably in rifle/carbine, but in dire need in revolver.
“And the top brass in America and in Britain dismissed the STG-44 as a âstupidly-easy-to-bend-out-of-shape piece of crap requiring a less-than-lethal-at-battle-range cartridge.â 8Ă33 Kurz isnât intended for half-mile one-shot-kills, you know.”
However, it must be noted that in Great Britain concept of intermediate cartridge was considered as worth further developing, so .280 British was developed.
Believe it or not, it was merely dismissed as a sub-machine gun variant! It was heavy…
There were cartridges made from “rocket paper” that could be introduced into the muzzle of the .58-cal. rifle-musket of the Civil War, and it would drop to the bottom, possibly with the aid of knocking the butt against something solid to seat it. These were privately purchased by a handful of Union units, and proved devastating in allowing the omission of the use of the ramrod to force the undersized, lubricated MiniĂ© ball down on the charge. I strongly suspect that once fouling got in the way, after just a few shots, that the ramrod was still required, but at least biting the end off was omitted. U.S. Ordnance steadfastly refused to consider it, even thought it was within the means of various cartridge manufacturers! So quite apart from “conservatism” against repeaters, the organization stymied “add on” technologies that might have proved detrimental to the guys in butternut brown organized in rebellion against the national government!
How come the Allin conversion of the Civil War musket peters out… So that the .50-70 becomes, briefly, the standard U.S. cartridge (down from .58), to the post 1873 Trapdoor Springfield in .45-70… “At least it can use the older Civil War bayonets…” until the 1880s when the rod bayonet is a cheap alternative to the final supplies of CW bayonets. Cue the Bundeswehr that retains the excellent DDR Nationale VolksarmĂ©e bayonet, useful as a field knife and pair of insulated wire cutters! Now that is parsimony!
Post-WWII: John C. Garand developed the machinery and manufacturing plant for his rifle, which gave it the needed edge over its competitors. The problem was that the same manufacturing plant and tooling had to be used for whatever rifle replaced the Garand… With the result of the great M14 boondoggle of sorts.
Enter the M16, in the words of C.J. Chivers, “the accidental rifle,” which is now the longest-serving U.S. long arm, and serves as basis for most of the more recent service rifles, at least in terms of ergonomics, even though 30-round magazines were an afterthought…
“Enter the M16, in the words of C.J. Chivers, âthe accidental rifle,â which is now the longest-serving U.S. long arm”
So far I know M16 was “stop-gap” solution which would be removed as fast as SALVO project firearm would enter service.
Daweo,
Could you point to your source for the idea that the M16 was a “stop-gap” solution waiting on the development of a SALVO weapon? Thanks!
“Perhaps itâs quite a coincidence âor maybe notâ that the latest evolution of Soviet assault-rifle development, the 5.45x39mm, has almost exactly the same energy as the .30 Carbine.”
No, these are much different: 5.45 use Spitzer bullets as default as well it is barely stable in flight, so if it hit something it deals damage by tumbling. However these have some in common: as one .30 Carbine was lighter than .30-06, one 5.45×39 was lighter than 7.62×39.
I was thinking of muzzle energy numbers specifically, as both the 5.45 and .30 carbine are listed at close to 1000 ft·lbf. Energy is not the same as destructive power, of course.
That is pure coincidence, even if muzzle energy similar, I think bigger distance bigger difference.
Saw this or something like it at 44:55 on this film of Vietnam
https://youtu.be/y3AIUQtGaDA