gatnerd

Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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NGSW Phase 2 Consolidation and info   Small Arms <20mm

Started 30/8/19 by gatnerd; 578659 views.
stancrist

From: stancrist

3/11/21

Is there a useful purpose for the "specific energy" comparison?  Because I  sure don't see a logical reason for it.  Nobody shoots a kilogram of ammo into one enemy soldier.

  • Edited 04 November 2021 0:13  by  stancrist
renatohm

From: renatohm

3/11/21

In practice theory is different.

Or

Even parrots can talk, doing is another thing altogether.

Common phrases in Brazil, mine aren't perfect translations but stress your point: until it's proven it's only an idea, no matter how good it seems to be.

I must say that even when proven you can still debate whether the testing was adequate, the world is full of stuff that worked like a charm during testing but failed miserably in the real world (eg the Soviet tank busting dogs).

gatnerd

From: gatnerd

4/11/21

nincomp said:

The US, in particular has been designing cartridges that do not permit long ogives for decades.

I think probably the best thing to come out 6.5 Creedmoor's meteoric rise to popularity is that broad swathes of the US Consumer and Military market has finally realized the value of long, streamlined bullets and cartridges that allow longer ogive spaces. We're finally seeing an understanding that projectile BC is just as / even more important than the muzzle velocity and energy specs of the cartridge. 

And we're seeing this now with NGSW, where a nice, pretty shapely EPR is being used as the General Purpose projectile.

Could things be better? Of course. But overall things are trending in a positive direction in regards to BC's.

Now if we could just get US bullet manufacturers to abandon using G1 bc's for their rifle bullets...

gatnerd

From: gatnerd

4/11/21

stancrist said:

Is there a useful purpose for the "specific energy" comparison?

I think it's just a handy shorthand for measuring both long range effectiveness compared to cartridge weight. I actually like it - easier to grasp at a glance then a series of ballistics charts. 

gatnerd

From: gatnerd

4/11/21

In terms of judging future equipment capabilities, I think there is a sliding scale between 'what currently exists' and 'what could exist.' 

I dont think we have to stick strictly with 'what exists' but also think we should be cautious about basing out analysis too far into the 'what could exist' level. 

For example, replacing the current M4A1 carbine:

Exists and Military tested: URG-I upper receiver as used by SOCOM. This thing has a NSN # and we can buy it right now online for testing and analysis. 

Exists in components but not tested, but should work fine: URG-I Upper w/ 416 barrel plus compensator, hydraulic buffer for FA controllability, 40rd mags (My M4A2 concept). All these parts exist now, and said rifle could be assembled 2 weeks from now and tested if any of us had a Class III FFL for testing automatic weapons.

Exists, in experimental form, not sure how well it works: The current NGSW guns and ammo. They all exist, but we're not really sure if all the bugs have been worked out, or how well they really will work. Could go either way. 

Does not exist, but little reason to believe it couldnt be built if $ was enough: An 'AR12' intermediate rifle for a 2.5" COL 6mm HAGAR rifle firing 85gr VLD's based on off the shelf projectile designs. This rifle doesn't exist, but based on the existence of the Six8 LWRCi rifle, as well as some of the hybrid lightweight AR10's that use some ar15 components, theres little reason to think any of the major firearms companies would not be able to build an AR12 if the government had laid out a big $ program to build one (like NGSW for 6mm GPC.) Fundamentally, no new technology needs to be pioneered to make the AR12; likely biggest development hurdle is having Magpul make a 30rd 6mm Hagar mag. 

Does not exists, may or may not work depending on prototype technology: The above AR12 6mm Hagar rifle - but using polymer TV neckless cases at 80kpsi. Now we're entering experimental but as yet not fully proven technology (high pressure cases) plus were talking about creating a brand new rifle design based on firing high pressure, likely requiring a new bolt design and possible other strengthening. 

Does not exist, relies entirely on ambitious simulated future technology: This would be the some of the 4-5lb FEA designed rifles firing high pressure cartridges with ultra low drag projectiles. These would be totally awesome and best choice if they did exist, but its also the weapon we have the least proof to rely on that its actually possible. 

Does not exist, sci-fi: We need to replace the M4 with a PDW firing caseless neurotoxic flechettes. Here we're relying essentially on something cool from Neuromancer. 

Personally, I lean towards the more conservative side for designs. A weapon doesn't have to exist, but for me they need to be grounded in what does exist and have a high probability of working. 

EmericD

From: EmericD

4/11/21

roguetechie said:

Would you happen to have the ff of the 62 grain mk318 mod 1 on hand?

According to Bryan Litz, the Mk318 Mod0 C7 is 0.126 so the i7 is 1.40.

This bullet is closer to a soft point hunting bullet than anything else.

Gr1ff1th

From: Gr1ff1th

4/11/21

That is a hilariously bad form factor, even for a 5.56 bullet 

EmericD

From: EmericD

4/11/21

stancrist said:

Is there a useful purpose for the "specific energy" comparison?

Well, for a given bullet construction, terminal effects are all linked to the bullet terminal energy.

That's one of the conclusion of the Small Arms Ammunition Configuration (SAAC) Study.

You can design more or less effective bullet structures, but for a given bullet design the one with the more KE will be the more effective.

That's also a conclusion of fielding the M80A1 along the M855A1, the former being able to defeat intermediate barriers at a much longer range than the later.

Even the volume of a bullet cavity in soil (and hence the visual effect of a near miss), is linked to bullet KE.

So, bullets are delivering KE to the target, and soldiers are carrying kilograms of ammo to perform their duty, so dividing kJ of target energy by cartridge weight is a "quick & dirty" indicator of the ammo capability.

You just need to multiply this specific energy with a hit probability to compare the effectiveness of different cartridges.

stancrist

From: stancrist

4/11/21

EmericD said:

Well, for a given bullet construction, terminal effects are all linked to the bullet terminal energy.

That's one of the conclusion of the Small Arms Ammunition Configuration (SAAC) Study.

You can design more or less effective bullet structures, but for a given bullet design the one with the more KE will be the more effective.

Granted, but you compared cartridges that have bullets of different configurations and construction.  IMO, that alone makes the comparison of questionable value.

EmericD said:

So, bullets are delivering KE to the target, and soldiers are carrying kilograms of ammo to perform their duty, so dividing kJ of target energy by cartridge weight is a "quick & dirty" indicator of the ammo capability.

The trouble is, soldiers do not carry a specified weight of ammo.  They carry a specified number of rounds of ammo.

And when they shoot, they fire the number of cartridges deemed necessary, not an arbitrary amount of ammo weight.

If the same number of rounds is compared, there is negligible difference in the downrange energy of M855A1 and 7N6.

EmericD said:

You just need to multiply this specific energy with a hit probability to compare the effectiveness of different cartridges.

Disagree.  First, effectiveness depends as much on bullet configuration and construction, as on impact energy,

Second, using a purely arbitrary (1.0 kg) weight of ammo produces a completely unrealistic ammo comparison.

stancrist

From: stancrist

4/11/21

gatnerd said:

I think it's just a handy shorthand for measuring both long range effectiveness compared to cartridge weight. I actually like it - easier to grasp at a glance then a series of ballistics charts.

First, it tells nothing about effectiveness, which depends more on bullet configuration and construction, than energy.

Second, it is very misleading because it compares the retained energy of the bullets from one kilogram of cartridges.

Soldiers shoot whatever number of rounds they think is needed, regardless of cartridge weight.

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