FMJ yaw and upset performance

[JASmith]

Thanks for the links, Joe. The next question is obviously - to what degree can these BCs be replicated in a mass-production military ball round?

Darn! you've been listening to Gene!

Longer answer is that a mass-production military ball round will probably need to be somewhat heavier to counteract the inevitable compromises. We can estimate based on current and historic experience with production rounds.

[stanc]

I have some 7x43 dummies in 7.62mm links, made by a small ammo firm in the UK. They tried out a short length of belt by manually cycling it through a GPMG, and reported that the belt and rounds fed just fine...

Despite their reported success with manual cycling, I remain skeptical that it would function reliably when fired.

The feed tray on machine guns like the M240 and M249 has a cartridge stop at the right front, which is designed to contact the shoulder of the cartridge to keep the round from going past the feed slot. With no shoulder protruding in front of the link, what will keep the cartridge from "overshooting" the slot and becoming misaligned?

IIRC, the frontmost feed pawl is also placed so that it pushes against the left side of the exposed cartridge shoulder. With no shoulder ahead of the link, what does the feed pawl push against?

[stanc]

Thanks for the links, Joe. The next question is obviously - to what degree can these BCs be replicated in a mass-production military ball round?

The only published figure readily available is that for the Norma 120gr FMJ (BC=0.428), which -- since it's roughly the same as the BC of M80 Ball -- seems inadequate to achieve the desired ballistics.

If only the mythical Wolf 110gr FMJ had materialized, we could've had more data to go on. As it is, people -- including myself -- have been doing a lot of guessing at a possible BC by looking at other bullet types (HPBT, solid, Accubond, etc), which hasn't given a definitive answer.

The only other option I can think of is if one could find out the BC of the Swedish military AP projectile, which weighs 7.3 grams (113 grains?). Nicely streamlined, but likely doesn't have early yaw in soft tissue simulant.

[stanc]

I downloaded the Barnes 110gr banded solid photo...

...and took some measurements on the screen. It is almost exactly the same length as the Swedish 113gr AP bullet, and very close to the same shape (except more sharply pointed).

Based on that, it's difficult to see getting a mass production 110gr FMJ with a 0.450 BC, although it can probably be done if weight is boosted to 120gr. Trouble is, a 120gr "unleaded" bullet will likely exceed 5.0 L/D...

[stanc]

That unsatisfactory gel test of the FMJ bullet has already been used in a British report on future small-arms ammunition to discredit the effectiveness of the 6.5mm calibre...

Aside from the yet-to-be-answered question if adequate terminal performance can be achieved with 6.5mm FMJ "green" bullets, your mention of that gel test with the 120gr Norma FMJ brings to mind a nagging thought. In regard to using a single, 6.5mm cartridge for infantry, history tells us that it's been tried before, and was found wanting.

All the countries that I know of which used a moderate-velocity 6.5mm round, also had a more powerful, .30-.32 caliber cartridge for machine guns. Also, they all instituted a switch away from 6.5mm, some (such as Sweden) for political or logistical reasons, but others (like Italy and Japan) for perceived inadequate terminal performance.

Now, Italy's change to 7.35mm can be ignored because they used obsolete round-nose bullets in 6.5mm. IMO, they would have been better served by upgrading 6.5 Carcano to a (110-130gr) spitzer bullet.

However, in the 6.5 Arisaka cartridge, Imperial Japan had what is essentially a 6.5 Grendel Magnum. Nevertheless, they still began a changeover to a full-power, 7.7mm round, reportedly as a result of combat experience.

Since you're proposing, in effect, a modernized 6.5 Arisaka cartridge -- with slightly lighter bullet at slightly higher velocity -- what reason is there to think it would fare any better?

[Tony Williams]

Stan, the Japanese 6.5mm Type 38 certainly did not suffer from "inadequate terminal performance"; I have a 1920s book which refers to it as being noted for inflicting unexpectedly severe wounds and I have also read a WW2 US Army medic's report which says the same thing. The weight distribution of the bullet promoted rapid yaw on impact and apparently it also often fragmented at short range.

The reason that the Japanese started to develop 7.7mm guns and ammunition in the late 1920s was for MGs, as you indicate - but in those days indirect MG fire was seen as being a normal tactic with sights adjustable to well over 2,000 metres. At such ranges, a bigger bullet is certainly useful (other things being equal) both for ballistic reasons and for tracer performance. Other countries also introduced powerful new 8mm rounds in the interwar period, primarily if not solely for MGs (e.g. Swedish, Solothurn and Breda rounds).

The Japanese used the 7.7mm calibre in MGs for about a decade before introducing it in rifles, which I suspect they may have done to simplify logistics (some of the new European 8mm MG rounds were introduced in rifles for the same reason - in at least one case 8mm rifles were only issued to MG units). And of course in those days of bolt-action rifles, recoil and ammo weight were a lot less significant than they are in modern automatic rifles.

If I was responsible for designing a new family of small arms around any single cartridge/loading which has seen significant military service, then I would pick the 6.5mm Type 38 without hesitation: its performance characteristics put it leagues ahead of anything else. We should be able to do even better now, though, since we can get the same performance from a smaller case.

[stanc]

Good answer, Tony. Thanks.

[warped]

Stan I am pretty sure that those Barnes 110's could be produced on high speed screw machines, in fact since our country has lost so much of its manufacturing to the Chinese there are an abundance of these machines and some sadly are going to be turned into scrap.

I know this because I live in the worlds largest manufacturing area (well at least it used to be) The Chicago to Rockford area was home to nealry all types of Manufacturing, you should see how many vacant factories we have now. Some of these are in the half million sq ft range.

[warped]

Despite their reported success with manual cycling, I remain skeptical that it would function reliably when fired.

The feed tray on machine guns like the M240 and M249 has a cartridge stop at the right front, which is designed to contact the shoulder of the cartridge to keep the round from going past the feed slot. With no shoulder protruding in front of the link, what will keep the cartridge from "overshooting" the slot and becoming misaligned?

IIRC, the frontmost feed pawl is also placed so that it pushes against the left side of the exposed cartridge shoulder. With no shoulder ahead of the link, what does the feed pawl push against?

If the demand was there it would certainly be addressed and worked out in a speed like you have never seen.

Personally I am of the opinion a high melting temperature polymer link could be made, that or good old fashioned steel, although a polymer would be far lighter.

[JASmith]

Tony,

Thanks! You put a nice historical perspective on the question.

The answer scratches an itch but kind of opens the question of what we really want the new cartridge to do. I haven't yet found a way to properly articulate my thoughts about the MG, but when we think about the notion of dismounted infantry per New Cartridge Developments and Implications for Dismounted Infantry Soldiers introduced by LRRPF52, it may be easier.

Should we upgrade the cartridge from the 5.56 NATO to e.g., the Grendel, the LMG will be far more capable. Experience with its use by the infantry would likely result in it supplanting the GPMG in dismounted operations.

Back to the thread topic: I've seen mentions of the wounding potential of the Arisaka. I just found references in one of Stan's posts in another forum: http://history.amedd.army.mil/booksdocs/...gure45.jpg that helps illuminate the weight balance. (Ref: http://xcrforum.com/index.php?action=pri...pic=4981.0).

Attaining the implied weight distribution with a single material may prove to be challenging...

[Tony Williams]

By the way - this is a bit off-topic but it might amuse you.

I was puzzled for a long time as to why the Italians necked-up their 6.5mm Mannlicher case to 7.35mm when they planned the switch to pointed bullets (which of course they had to step back from when WW2 started).

An Italian military historian told me the reason: they were desperately short of money, and had allowed their 6.5mm weapons to get into a bad shape with many having shot-out barrels. They could not afford to replace all those barrels, so they decided it would be cheaper to just ream out the whole lot to a larger calibre and cut new rifling grooves. So that explains the increase, and also the selection of the very odd calibre of 7.35mm...

[warped]

By the way - this is a bit off-topic but it might amuse you.

I was puzzled for a long time as to why the Italians necked-up their 6.5mm Mannlicher case to 7.35mm when they planned the switch to pointed bullets (which of course they had to step back from when WW2 started).

An Italian military historian told me the reason: they were desperately short of money, and had allowed their 6.5mm weapons to get into a bad shape with many having shot-out barrels. They could not afford to replace all those barrels, so they decided it would be cheaper to just ream out the whole lot to a larger calibre and cut new rifling grooves. So that explains the increase, and also the selection of the very odd calibre of 7.35mm...

Wow, what a monumental error, good thing for our guys though.

[stanc]

Stan I am pretty sure that those Barnes 110's could be produced on high speed screw machines...

You may be right. But even if they could, there is still the question of terminal effects. It's likely that the Barnes bullet would produce a wound pattern in gelatin much like that of the Norma FMJ: undesirably deep penetration before yawing. Would need testing to be sure, though.

...in fact since our country has lost so much of its manufacturing to the Chinese there are an abundance of these machines and some sadly are going to be turned into scrap.

I know this because I live in the worlds largest manufacturing area (well at least it used to be) The Chicago to Rockford area was home to nealry all types of Manufacturing, you should see how many vacant factories we have now.

Yeah, that's been a gripe of mine for many years. I've long thought that "outsourcing" so much of our manufacturing is very bad long term strategy for this country, even if good for short term tactics of US corporations.

Oh, well. No nation stays #1 forever...

[stanc]

Personally I am of the opinion a high melting temperature polymer link could be made, that or good old fashioned steel, although a polymer would be far lighter.

The ability to manufacture links is not in doubt. What I question is the ability to design links to properly interface cartridges like 6.5 Grendel with the feed mechanisms of existing 5.56mm LMGs.

Understand, I'm not saying it can't be done. I'm only saying that I don't see how it could be accomplished.

[bwaites]

You may be right. But even if they could, there is still the question of terminal effects. It's likely that the Barnes bullet would produce a wound pattern in gelatin much like that of the Norma FMJ: undesirably deep penetration before yawing. Would need testing to be sure, though.

I agree on the outsourcing of machine work and industry, its no doubt a bad idea in the long run.

As for 110 Barnes terminal ballistics, I've shot them into wood, and most of them, if recovered, look like they could be reloaded and fired again. They aren't capable of penetrating 1/2" steel, at least from the Grendel, though.

They punch a very nice hole through wood, though. I do intend to shoot some into some type of gel, but I seriously doubt they would tumble or upset in their current configuration. I've talked with coyote hunters who use them specifically because they make a small hole entering and leaving, saving the pelt. Doesn't sound like what you want.

I'm sure they could be redesigned to tumble, but suspect they'd lose some of their BC advantage for such a light bullet in the process, though.

[stanc]

Should we upgrade the cartridge from the 5.56 NATO to e.g., the Grendel, the LMG will be far more capable. Experience with its use by the infantry would likely result in it supplanting the GPMG in dismounted operations.

I agree. IMO, that's far more likely to occur than actually replacing 7.62 NATO in the system.

Back to the thread topic: I've seen mentions of the wounding potential of the Arisaka. I just found references in one of Stan's posts in another forum: http://history.amedd.army.mil/booksdocs/...gure45.jpg that helps illuminate the weight balance.

Thanks, John. I was trying to remember what book that was in.

Attaining the implied weight distribution with a single material may prove to be challenging...

Indeed. For Tony's interest -- the UK and Europe -- I suspect it will require an FMJ with a two-piece core, as in M855/SS109, although a one-piece core design similar to 5.45 M74 might possibly give the desired results.

[bwaites]

Is it frustrating to anyone else that we can do this easily with hollowpoint bullets, but that we have to intentionally design a compromise? A bullet that meets the Hague criteria in name only? Where the intent is to do exactly what the Hague DOESN'T want it to do, (wound more effectively than a round nose, solid bullet), but not because it was actually designed that way, but because it does it as a function of its accuracy?

Weird business we are discussing!

[stanc]

Well, the British are wierd people...

It's human nature, Bill. Most individuals say they want law and order...until a law interferes with doing something they want. Then they seek a loophole in the law, a legal technicality to enable them to do as they wish.

Same with the Hague prohibition of expanding bullets. Tony (and presumably others in the UK and Europe) wants to remain in technical compliance with Hague, but willfully violate the spirit of the agreement.

The US has gone even further, with the JAG approving expanding bullets like TSX and SOST (which clearly violate the Hague) on flimsy legal arguments like they were selected for "barrier blind" performance, not for expanding in soft tissue.

Myself, I find it rather amusing. As I've long said, humans are not rational beings; they are rationalizing ones.

[bwaites]

Well, the British are wierd people...

It's human nature, Bill. Most individuals say they want law and order...until a law interferes with doing something they want. Then they seek a loophole in the law, a legal technicality to enable them to do as they wish.

Same with the Hague prohibition of expanding bullets. Tony (and presumably others in the UK and Europe) wants to remain in technical compliance with Hague, but willfully violate the spirit of the agreement.

The US has gone even further, with the JAG approving expanding bullets like TSX and SOST (which clearly violate the Hague) on flimsy legal arguments like they were selected for "barrier blind" performance, not for expanding in soft tissue.

Myself, I find it rather amusing. As I've long said, humans are not rational beings; they are rationalizing ones.

Trust me, I agree on all of these points!

However, the other piece of the US puzzle is that we AREN'T Hague signatories, so it really doesn't matter. I think its ludicrous that the 100 year old Hague outlaws expanding bullets, but then says nothing about fragmentation mines, grenades, smart munitions that expand, etc. I understand that the smart munitions weren't available, but the guys who wrote the Hague guidelines did know about the others.

[LRRPF52]

"Ok, our civilizations want to wipe each other out, as we conflict on every ideological landscape in human relations. Let's declare war on each other...but we must agree on how we will be doing the killing, bombing, gassing, etc....do all the diplomatic representatives present concur?

LRRPF52