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PDW Sabot: Suppressors and Accuracy   Small Arms <20mm

Started 20-Aug by nincomp; 4308 views.
nincomp

From: nincomp

20-Aug

Since the PDW dead horse has again been resurrected, I thought that I would bring up saboted rounds.  In this thread, I want to focus more on compact carbines rather than overgrown pistol worn on the hip.  The primary users would be drivers and others who would come into harm's way while in a vehicle.  They would need to rapidly escape from the vehicle (with a weapon) or shoot from within the vehicle.  The non-folding stock of the M4 is one of the reasons for this thread, although I know that solutions like SIG's Rattler now exist.   Another reason stems from objections to short-barreled M4's due to excessive blast and sub-optimal utilization of the standard 5.56x45's propellant*. 

One possible solution is to increase swept volume with a relatively large diameter bore and a saboted projectile.  I just don't know if this idea makes any sense since I don't know the system accuracy.  It would be most useful if armor penetration at relatively short range is critical, but would poor accuracy reduce its practicality at longer distance?  Would the sabots themselves endanger friendly forces?  

The only accuracy information that I have seen is three targets on the CBJ Tech site.  Does anyone have more accuracy data on saboted rounds?  Does the accuracy vary with the thickness of the sabot walls, limiting the ratio of bore-to-projectile diameters?

Lastly, has anyone seen information on sound suppressors designed specifically for use with saboted projectiles?

Thanks

edited to add:

* The "engineer" part of my brain is really annoyed by inefficiency

  • Edited 20 August 2020 19:56  by  nincomp
roguetechie

From: roguetechie

20-Aug

So here's the thing about the "inefficient use of propellant in short barrel 5.56's"...

That genuinely WAS a problem at one point, kinda.

Modern rounds like m855a1 etc though are designed around a 14.5" barrel length assumption. Same with mk318 and etc.

It's like lots of other objections to the m16 and 5.56 in general, at one point they were actually issues but they're not anymore. So people are arguing against things that are no longer issues (unless you or your country bought hk416's, in that case you either accept that you're locked out of ammunition advances and designs that happened on or after 2008 or so or you accept insane breakage and replacement rates. But that's a problem with that gun not 5.56 guns in general)

It's kinda like how people still talk about m855a1 being too high pressure and expensive to produce. Both things were true at one point but they're not now.

As far as the "blast issue" goes, in addition to above there's the advances in suppressor and muzzle device technology like the smuzzle which can actually turn some of that excess muzzle pressure into a net positive.

As much as I'm actually a huge fan of the cbjtech sabot technology it's still a hard sell when you get down to it because it's not actually all that necessary. 

stancrist

From: stancrist

20-Aug

nincomp said:

Would the sabots themselves endanger friendly forces?

Uh, the sabot goes the same direction as the projectile...

nincomp said:

Does anyone have more accuracy data on saboted rounds?

Remington .30-30 Accelerator @ 100 yards:  https://youtu.be/kD6niXoUvwM?t=388

nincomp

From: nincomp

20-Aug

roguetechie said...

Modern rounds like m855a1 etc though are designed around a 14.5" barrel length assumption. Same with mk318 and etc.

That is true.  These days, I consider something with a 14.5" barrel to be a normal carbine, rather than a "short carbine".  I should have stated that I am more interested in a VERY compact carbine, something with a barrel shorter than that used for a standard M4.  Greg(9N9WO) had mentioned the blast from barrels roughly 12" long, and many short AR's use 10.5" barrels.  He also mentioned using the weapon from INSIDE a vehicle, which exacerbates the situation. 

nincomp

From: nincomp

20-Aug

stancrist said...

Uh, the sabot goes the same direction as the projectile...

There ARE occasions when one has to shoot over or past friendly forces.  I would think that this would be more likely in cases when support troops need to join in a battle, for example, when their compound has been overrun and they are taking cover behind whatever is available.

stancrist said...

Remington .30-30 Accelerator @ 100 yards:  https://youtu.be/kD6niXoUvwM?t=388

In the clip, Paul Harrell notes that he has seen variability in the accuracy from the Remington Accelerator sabot rounds.  That is pretty much what I have read from numerous sources.  One poster on the IAA forums recently commented that some rifles seem to shoot them particularly well.  It is possible that a weapon designed specifically to shoot saboted rounds could be more consistent, but I don't know if that is actually the case.

graylion

From: graylion

21-Aug

I agree. I'll mention this

https://www.sigsauer.com/store/sig-mcx-rattler-sbr.html

not because I think that it is a good idea, but I think this is on the short end for the kind of weapon we need to look at.

What kind of combat range are we thinking about?

stancrist

From: stancrist

21-Aug

nincomp said:

There ARE occasions when one has to shoot over or past friendly forces.  I would think that this would be more likely in cases when support troops need to join in a battle, for example, when their compound has been overrun and they are taking cover behind whatever is available.

That's possible.  However, I'm still not seeing how the featherweight plastic sabot -- which initially is traveling along pretty much the same trajectory as the projectile -- endangers friendly forces if the projectile itself does not.  For hostage rescue this might be a valid concern, but for infantry combat, it seems to me like a non-issue.

nincomp said:

In the clip, Paul Harrell notes that he has seen variability in the accuracy from the Remington Accelerator sabot rounds.  That is pretty much what I have read from numerous sources.  One poster on the IAA forums recently commented that some rifles seem to shoot them particularly well.  It is possible that a weapon designed specifically to shoot saboted rounds could be more consistent, but I don't know if that is actually the case.

I suspect that the poor groupings seen with some rifles is likely due to incompatible (too slow/too fast) rifling twist.

You could evaluate your concept by acquiring a .300 BLK SBR, loading up some sabot rounds, and test firing them.

nincomp

From: nincomp

21-Aug

graylion said...

What kind of combat range are we thinking about?

The useable range partly depends upon accuracy, but certainly less than the 300 meters that is often mentioned for the ideal PDW.   If a saboted cartridge is used, the projectile may be lethal well beyond the range at which it can be expected to hit the adversary.  It would need to provide a reasonable standoff distance of at least 100 meters, but I am not certain if 200m could be expected.  That is one reason that I began this thread in the first place.  For example, the M1 Carbine, had a sight labeled 300 yards, but many say that such a range was overly optimistic.

nincomp

From: nincomp

21-Aug

stancrist said...

However, I'm still not seeing how the featherweight plastic sabot -- which initially is traveling along pretty much the same trajectory as the projectile -- endangers friendly forces if the projectile itself does not.  For hostage rescue this might be a valid concern, but for infantry combat, it seems to me like a non-issue.

That may well be true.  That is another of the reasons I started this thread.  I simply do not know.

stancrist said...

You could evaluate your concept by acquiring a .300 BLK SBR, loading up some sabot rounds, and test firing them.

It has been a while since I have done much shooting.  If I were to load up some sabots and shoot them, the best that I would be able to tell you is: "They went over there ... somewhere..."  :(

In reply toRe: msg 9
nincomp

From: nincomp

21-Aug

While I am busy asking questions, I might as well bring up projectile diameter.  This goes along with the question about the bore-to-projectile diameter ratio.  Although the SCHV concept has been proven effective, what happens as the velocity drops.  In other words, instead of a saboted 5.56 projectile at moderate velocity, would it make more sense to use a larger projectile, say something in the 6.5-7mm range.  It is entirely possible that the .300 BO (7.62x35) ends up being a better choice, even though I admit that it is not one of my favorite cartridges. (too many compromises, dagnab it!)

  • Edited 21 August 2020 2:19  by  nincomp
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