Marine Batallion goes silent....

[JJ_BPK]

Originally Posted by 35NCO

A vented Gemtech Bolt carrier assembly and a Gemtech threaded, not fast attach, Trek-T (Titanium) (SN 44875) Suppressor , with a PRI gas buster charging handle.

You, My friend have very good eyes. I had to zoom in 350% to get the serial..

or have you fondled said bang stick??

Originally Posted by miclo18d

Am I mistaken? I always thought that a 5.56 round (55 and 62gr) needed upwards of 2700fps to fragment correctly (and somewhere around 2500fps for the 77gr). That guys 10.5 out of the barrel is only 2300fps and people wonder why the 5.56 isn't killing the bad guys.

Same observation,, I thought that the ported carrier may be why,,
but I see 10.5 inch barrels all over the place??

[35NCO]

I mentioned the visible serial incase someone wanted to get one from the same run to test. ( JJ, No...eyes getting worse. BIG HD monitor! )

I do own a MK18 MOD 0/COLT M4CQBR and a DD MK18 MOD 1. I have ran a LOT of tests with different port sizes, ammo, and various suppressors. For my needs, an adjustable gas block was the answer. (Govnah 3 port by micro MOA) Both are range toys and not arms room deployment weapons.

I think another reason for the 10.3/10.5 is that when it is outfitted with a suppressor it is not longer than a conventional M4. 14.5 inch M4 barrels with a suppressor might be getting too long for urban operations.

As far as lethality goes, yes, with 5.56 there are quite a few issues with short barrels! Good catch! (If going short and wanting some nasty topple, I would consider 5.45!)

The 10.5 and the VSBRs were talked about on PS here:

http://www.professionalsoldiers.com/...ighlight=dater

Choose wisely!

[sfshooter]

Ran security in Iraq with my own 10.5 upper on M4 lower signed out from an ODA. The big bonus was operating in and out of a vehicle. It made deployment a lot quicker when coming out of an up armored Excursion, even Humvees. It maintained its accuracy very well out to 300 meters. I had an ACOG with attached J-Point red dot.
I haven't seen actual bodies shot by this configuration (we run from fights with the clients while slinging lead if and when necessary to get out of an hot AO) but it did just fine on the wild dog population

[miclo18d]

Turning someone's head into a canoe, you don't need the round to tumble, but when you're stabbing someone with an ice pick in the heart.... well, I've heard enough anecdotally that when I built mine, it was a 16 inch barrel with polygonal rifling to get a little extra speed. I wondered if I should have gone to 18"...

When I was in, I wanted to be part of the 10in crew, but WTF did I know? I was an 18D. It took me several years of research after retirement to understand internal, external, and terminal ballistics (I knew the effects of terminal). I get the vehicle thing, but the second you step out with your high speed maneuverability, you have pigeonholed yourself. The 77gr BH was designed originally for the SPR, but was found to work well with shorter barrels and leaves the barrel right at around 2500fps out of a 14" barrel, probably will tumble only out to 50-100m.

The accuracy of short barrels is not in question. Barrel length has little do do with accuracy but muzzle velocity has a lot to do with external and terminal ballistics. When using standard supplied ammunition, the main factor is barrel length and then it's the law of diminishing returns as you go past 20"-22". Heavy barrels tighter twist rates better BC projectiles, accuracy hand loads.... it goes on forever.

[frostfire]

Originally Posted by 35NCO

Based on the video, it looks like the gas system is balanced by dropping that brass at 3 o clock.

After trying to educate myself on it, I have learned that understanding overgassed/undergassed is more complex than truing at distance with consideration to coriolis effect and spin drift!

So is brass deflection a true empirical evidence of a rifle gas' level?
My OBR sends it to 1 o'clock and I have wondered if between being overgassed and tiiiight chamber design lead to the known kaboom cases

Originally Posted by 35NCO

(If going short and wanting some nasty topple, I would consider 5.45!)

I have moved on from 5.45 option to 10.5" 7.62 with 8M3 "effect" rounds. These precuts rounds live up to the hype. Not tight standard deviation with muzzle velocity though (and not suppressor friendly either), but any hit in torso and one is done.

[35NCO]

I think brass ejection direction and it's violence of action is a good general determination of what's going on with the rifle. If you shoot alot, the recoil impulse can also give you a feel of if something is off.

What makes it do that depends on a large number of variables. Some of which I talked about earlier in this thread. Since you are dealing with a percentage of diminishing force traveling a constant distance and volume from gas volume of the cartridges expanded powder burn, your ammo and it's load, powder type, can greatly offset the weapons gas balance.

I dont know if you tinkered with the OBRs parts or not, but it may be designed to be tailored to very specific loadings if it's a factory setup. Once you start changing things it will get more complicated.

Again, being over gassed is not always terrible either as far as reliability is concerned. It will have stronger affects on parts wear and follow up shot times. It really only becomes a big concern with suppressors and no where for that gas to be vectored but in the shooters face.

[sfshooter]

Originally Posted by miclo18d

Turning someone's head into a canoe, you don't need the round to tumble, but when you're stabbing someone with an ice pick in the heart.... well, I've heard enough anecdotally that when I built mine, it was a 16 inch barrel with polygonal rifling to get a little extra speed. I wondered if I should have gone to 18"...

When I was in, I wanted to be part of the 10in crew, but WTF did I know? I was an 18D. It took me several years of research after retirement to understand internal, external, and terminal ballistics (I knew the effects of terminal). I get the vehicle thing, but the second you step out with your high speed maneuverability, you have pigeonholed yourself. The 77gr BH was designed originally for the SPR, but was found to work well with shorter barrels and leaves the barrel right at around 2500fps out of a 14" barrel, probably will tumble only out to 50-100m.

The accuracy of short barrels is not in question. Barrel length has little do do with accuracy but muzzle velocity has a lot to do with external and terminal ballistics. When using standard supplied ammunition, the main factor is barrel length and then it's the law of diminishing returns as you go past 20"-22". Heavy barrels tighter twist rates better BC projectiles, accuracy hand loads.... it goes on forever.

Yes, I agree with you on the pigeonholing thing..... was in a couple of situations that made me think of the practicality of the short barrel. External and terminal ballistics are very important. I was quite impressed with the SMK 77 gr that was made for the SPR......Years later my build and carry is now an 18" .223 Wylde chamber, which is what the SPR was. Not only do you have the accuracy but you also have the ballistics to go with it.

[Dive08]

nt

[frostfire]

hey 35NCO, this slow mo suppressor vid makes me appreciate just how much go to the baffle shape design

https://www.youtube.com/watch?v=7pOXunRYJIw

[Tuukka]

Originally Posted by 35NCO

Yes. DI weapon systems are the worst weapon systems to suppress in modern weapon design and suppressor design.

The weapon has a natural balance of careful reciprocating mass, kinetic energies, and very specific dwell times. All tailored to various barrel lengths and gas port sizes. Some cartridges can affect the overall pressures as well. The issue is that the suppressors changes the dwell time which results in increased back pressure porting an increased quantity of carbon back into the action. This also increasing cyclic speed with the changed duration pressure curve. The increased back pressure with certain blast baffle geometries is so intensive it can be blinding and difficult to deal with on rapid fire.

This dramatically also increases the need for cleaning the weapon. It gets overwhelmed with carbon quite quickly. Worn out M4s with fairly loose, to border line tolerance can function longer but newer weapons tend to not deal with it well. Running dryer on oils and some coatings help here (NP3), but it does not address fixing why it happens in the first place.

For it to work with a Stoner designed DI weapon efficiently, it must have little to no back pressure. There are significant engineering problems with that. It is not as simple as the command may like brand X so all brand X suppressors that are 7.62 go on all the various 7.62 weapons. This is also true for barrel lengths with the various gas port sizes and buffer mass differences. Ideally each weapon would have a unique suppressor device.

Piston guns are a little better, but you are trading some problems for another.

There are also harmonic stability problems in relation to bore with suppressor application. We are starting to free float more weapons today, which is great, but the harmonic stability can be influenced by increased mass and dwell imposed by a suppressor. Especially devices with a dissimilar resonance that are not sympathetic to the weapons natural oscillations. So there is durability and accuracy problems associated there for long term barrel life and consistency. Especially in hard use and especially in regards to frequent follow on shots.

As far as mad minutes go, that is a tremendous problem with this proposal. There needs to be a vast relook at how we apply metallurgical science to the first few baffles in the stacks. Erosion will be quick in conventional infantry forces of these devices as in the optempo of early IRQ and AFG. Very few devices can hold up to the consistent abuse you reference of 12-14 magazines continuously.

Again, it would be better as some sort of integral device that is similar to barrel life that PFC Snuffy can’t lose or mess up.

We can use off the shelf stuff now. But we will have what I describe here. It is going to be very expensive with massive tradeoffs that may not make it appropriate at this time. Or perhaps for only short duration fieldlings with very specific applications to weapons that have been tested with the device by various reputable weapons engineers.

Hi,

How is it possible that SOF units across the globe have utilized suppressors quite a lot on DI operated carbines ( M4, M4A1, C8 SFW etc ) for 20+ years now.

Units that by nature shoot much more round than a typical infantry etc. unit.

Yes, there is a varying degree of back pressure on many current/traditional suppressor types.

Usually a quality DI operated 5.56 carbine will still work very reliably when suppressed, although more frequent cleaning is of course required.

Yes, you will have a POI shift whether the rifle is free floated or not.

It is not a free lunch by no means but easily doable and has more positives and negatives.

The U.S Army has had a Family of Small Arms Suppressor project for 10+ years now, with no suppressors adopted for M4 carbines for GPF.

I believe the recent RFI from the USMC will actually lead to a contract phase quicker than for the Army.

Other smaller countries also have suppressor trials/evals running right now, as they cannot afford to spend 10+ years on research.

There has been quite a lot of discussion/RFIs/ requirements for next generation suppressors etc, yes the suppressors now are evolving with designs from different manufacturers with lesser back pressure etc.

But, if you have an accessory that brings certain level of capability now, do you wait 3-5 years for the next gen?

Sort of like optics/weapons etc not being bought because there will a a better one in a few years?