6.5mm Terminal Effectiveness

[stanc]

It has often been said that historical tests like those conducted by the "Pig Board" have shown the "ideal" caliber range for infantry rifles/carbines to be 6.5-7mm. Yet, every country that adopted 6.5mm or 7mm eventually abandoned them in favor of 7.62mm or larger calibers. In most instances, economics and/or politics played a major role. However, those don't seem to have been factors in the decision by Imperial Japan to switch from 6.5mm to 7.7mm.

The only published reason that I've ever seen is that combat experience resulted in dissatisfaction with the terminal effectiveness of 6.5 Jap. This is a bit puzzling to me, inasmuch as the standard, 139gr ball projectile has a configuration and rearward weight bias which should produce fairly rapid onset of yaw in soft tissue.

Can anybody:

1. Cite authoritative source(s) of the actual reason(s) for the switch from 6.5mm to 7.7mm?
2. Cite anecdotal reports of incapacitation effect of 6.5 Jap ball ammo, either by shooters or shootees?
3. Post the ballistic gelatin wound profile of WWII 6.5 Jap ball ammo?

[tolson68]

The switch from 6.5 was brought on by reports coming from Japanese infantry that when they shot someone they just kept coming (sound familiar).  I believe part of the actual quote mentioned Hollywood.  Apparently they were expecting an approaching soldier to fly backwards and bounce off a bar room wall after being shot, but it didn't happen.  I believe the original bullet was 160gr round nose projectile and they later switched to the 139gr bullet to get greater velocity and effectiveness at shooting through heavy bamboo brush in the pacific theater.  I might be confusing the 6.5J with the 6.5 Carcano on the 160gr issue, I'm too tire to look it up.

Most of the European and Scandy countries adopted the 7.62 simply for NATO, even some of the countries that didn't participate in NATO.  The 6.5x55 Swede is a fantastic hunting round used all around the world, though most of the loads are at far less than capacity, simply because the older weapons the round was designed for cannot handle higher pressures.

[stanc]

The switch from 6.5 was brought on by reports coming from Japanese infantry that when they shot someone they just kept coming (sound familiar).  I believe part of the actual quote mentioned Hollywood.  Apparently they were expecting an approaching soldier to fly backwards and bounce off a bar room wall after being shot, but it didn't happen.  I believe the original bullet was 160gr round nose projectile and they later switched to the 139gr bullet to get greater velocity and effectiveness at shooting through heavy bamboo brush in the pacific theater.  I might be confusing the 6.5J with the 6.5 Carcano on the 160gr issue, I'm too tire to look it up.

Thanks for the feedback. I doubt that movies were a factor, as Hollywood didn't get into the "knocked 20 feet backwards" silliness until well after WWII.

You're correct about 6.5 Jap originally having a heavy, round nose bullet (as did every other military rifle cartridge when smokeless powder came into use in the late 19th century). But, the spitzer bullet was adopted a few years before the First World War.

[dont_tread_on_me]

  Stan I think you may find this article very interesting.I know I did.It touches on the 6.5 Arisaka but takes on development of several other military cartridges during the 20th century.
http://www.quarry.nildram.co.uk/256brit.htm

[marinewmu911]

This is just my opinion, but the military was set to transition to a 6.5-7mm cartridge when the Garand was developed, they didn't because we had 30-06 coming out our asses so the Garand was chambered for that. And every weapon since has been either 7.62 or 5.56ish across the world, because of the ease and inexpense of the two cartridges. Now trying to transition to 6.5 grendel, creedmoor (a precision round), or 6.8 SPC because they are better performing is still not happening due to the ease of keeping the current 'does the job, sorta' 5.56 and venerable 7.62x51. Its not because they don't 'meet standards' its because top brass and thus major ammo manufacturers like the way things are. This seems to be changing slowly as people with more progressive and 'the best for the cost, not the lowest cost' attitudes slowly make an impression. Still slow as all get out, but I have hopes for the army and marines adopting the ACR in the coming years and that opens the door for cheap caliber conversion as opposed to the entire rearmament of the force.

[Tinman]

i think if the LSAT program proves to be a success, then we may finally see a bullet in the 6.5 to 7 mm range adopted by the military for both the individual soldier as well as a light to medium machine gun cartridge. if this happens, then kiss the stoner design goodbye as well as SCAR or any other conventional design out there today. IMHO

[marrandy]

This is also a good article with links to other places.

http://www.historyofwar.org/articles/weapons_SA80.html#_ednref40

[stanc]

  Stan I think you may find this article very interesting.I know I did.It touches on the 6.5 Arisaka but takes on development of several other military cartridges during the 20th century.
http://www.quarry.nildram.co.uk/256brit.htm

Yeah, Tony has some informative articles and good photos on his site.

Here are a couple of items I came across, on the 6.5 Jap specifically:




I still haven't found anything authoritative as to reasons why they initiated a switch from 6.5mm to 7.7mm, though.