Why not more DI guns?

**RetroRevolver77** · 04-13-18, 09:23

The AUG was ahead of it's time. Here's a video showing an AR18 based system using a short stroke piston in a fine sand test. Downside to the AUG is that it isn't a sealed system but it works very well overall.

**crusader377** · 04-13-18, 09:53

Originally Posted by 7n6

Long stroke piston is master race.

The video highlights three variations of modern gas systems; Tavor short stroke piston, AR direct gas impingement, and Kalashnikov long stroke piston.

This is why Ted Marshall, myself, and Arsenal Bulgaria gave you the SLR 106/107- a long stroke piston in common 5.56 NATO along with readily available 7.62x39 cal.

7n6

I would argue that all three types of gas systems are highly reliable if the firearm is designed properly. DI guns like the M16/M4 and the much older French MAS 49 have excellent reputations for reliability even under adverse conditions. Short stroke gas piston guns like the SCAR, HK 416, etc.. are extremely reliable but their are also duds like the British SA-80 and the WWII German G41 and G43. Long stroke guns like the AK can be extremely reliable as well.

I find though that you are cherry picking facts to argue the AK and piston system superiority while overlooking many advantages that DI guns have over piston systems. The first one is weight, your basic AR15 is a pound or two lighter than comparable piston rifles (15-25% lighter). This weight difference is one or two extra magazines in combat. A soldier can only carry so much weight and furthermore is lighter gun is far more conducive to carrying a weapon in a ready position for extended periods of time.

Second accuracy and shootability, DI guns on average are more accurate than piston guns. This combined with better recoil characteristics gives DI guns an advantage in effective range for an average soldier. Furthermore the better recoil characteristics gives you a higher percentage of second shot hits with a AR.

I would put money on that if we ran a test of a Colt 6920 vs your pet rifle the 5.56 AK with equal shooters, the Colt 6920 would have at least a 50M-100M effective range advantage if not more over the SLR106. Furthermore, if we ran a test engaging multiple targets at multiple distances with equal shooters, I bet the Colt would post better times due to its better recoil characteristics and ability to get on target quicker. This stuff is a big deal in combat and far more important than minutia you were mentioning in previous posts.

Given a choice for the same weight I would much rather take a M4 with 210rds into combat rather than your SLR107 with 150rds into combat. Oh and by the way 50-100M of extra engagement range is really nice to have along with a higher hit probability. I don't think that I would sweat not having the ability to beat my charging handle against trees or stuffing a ham sandwich in my weapons action.

**RetroRevolver77** · 04-13-18, 14:05

Originally Posted by crusader377

I would argue that all three types of gas systems are highly reliable if the firearm is designed properly. DI guns like the M16/M4 and the much older French MAS 49 have excellent reputations for reliability even under adverse conditions. Short stroke gas piston guns like the SCAR, HK 416, etc.. are extremely reliable but their are also duds like the British SA-80 and the WWII German G41 and G43. Long stroke guns like the AK can be extremely reliable as well.

I find though that you are cherry picking facts to argue the AK and piston system superiority while overlooking many advantages that DI guns have over piston systems. The first one is weight, your basic AR15 is a pound or two lighter than comparable piston rifles (15-25% lighter). This weight difference is one or two extra magazines in combat. A soldier can only carry so much weight and furthermore is lighter gun is far more conducive to carrying a weapon in a ready position for extended periods of time.

Second accuracy and shootability, DI guns on average are more accurate than piston guns. This combined with better recoil characteristics gives DI guns an advantage in effective range for an average soldier. Furthermore the better recoil characteristics gives you a higher percentage of second shot hits with a AR.

I would put money on that if we ran a test of a Colt 6920 vs your pet rifle the 5.56 AK with equal shooters, the Colt 6920 would have at least a 50M-100M effective range advantage if not more over the SLR106. Furthermore, if we ran a test engaging multiple targets at multiple distances with equal shooters, I bet the Colt would post better times due to its better recoil characteristics and ability to get on target quicker. This stuff is a big deal in combat and far more important than minutia you were mentioning in previous posts.

Given a choice for the same weight I would much rather take a M4 with 210rds into combat rather than your SLR107 with 150rds into combat. Oh and by the way 50-100M of extra engagement range is really nice to have along with a higher hit probability. I don't think that I would sweat not having the ability to beat my charging handle against trees or stuffing a ham sandwich in my weapons action.

If your position is that a stock LE6920 is more accurate than a stock SLR 106, I can honestly say they shoot about the same. As far as your personal preferences are concerned, that's fine. Everyone has their opinions. I like all kinds of rifles, I have several Colt's here along with 106's and AUG's even. There's pro's and cons of each. Weapons are evolving over time, constantly updating, constantly moving forward. These newer generation weapons coming out are exciting. I've thought about selling all my stuff off and just going straight FN, B&T, Steyr, CZ etc. All of those are modernized AR18 designs which when discussing gas systems and weapon designs as a whole- are my personal preference.

7n6

**ABNAK** · 04-13-18, 18:41

The French MAS 49/56 is often called a DI system, and I guess it is, but it is not the same type of "DI" that an AR is. The MAS gas tube blows gas into a "blind" hole (meaning it is empty, like a Mini-14's gas nozzle blows into an empty hole) and does not act to cycle the action like an AR does. The MAS has a massive, heavy bolt carrier and the gas from the tube just serves to blow the damn thing back out of battery.

How do I know? I used to have one years ago that had been converted to .308 and to take FN-FAL mags.

**Moose-Knuckle** · 04-13-18, 20:52

When the AR-180B came out I had high hopes that finally someone was bringing a viable affordable AR-18 variant to market.

Sigh....

**eodinert** · 04-15-18, 02:13

Originally Posted by 7n6

I want a rifle to fire suppressed, unsuppressed all without having to do squat to the gas system.

That rules out the AK and the 416.

**RetroRevolver77** · 04-15-18, 09:40

Originally Posted by eodinert

That rules out the AK and the 416.

AK's suppress fine without having to do anything to the gas system. Why? Because they level the gas off at the block or gas tube depending on model. Gas is only used to push the carrier group back about a 1/2" to unlock the bolt and after that the action uses inertia for the remainder of the cycle. In fact the rifle can run even without a gas tube, Vicker's did a video on that if I remember correctly. Here's a bone stock 106UR running a Gemtech HALO with a Vltor adapter.

7n6

**RetroRevolver77** · 04-15-18, 10:03

In reference to the above post, here's a 74 long stroke piston running without gas tube- skip to the 2:00 mark to watch it function.

**Clint** · 04-15-18, 11:06

Originally Posted by ABNAK

The French MAS 49/56 is often called a DI system, and I guess it is, but it is not the same type of "DI" that an AR is. The MAS gas tube blows gas into a "blind" hole (meaning it is empty, like a Mini-14's gas nozzle blows into an empty hole) and does not act to cycle the action like an AR does. The MAS has a massive, heavy bolt carrier and the gas from the tube just serves to blow the damn thing back out of battery.

How do I know? I used to have one years ago that had been converted to .308 and to take FN-FAL mags.

Yes,

The wiki article on direct impingement actually sums it up nicely.

Originally Posted by WIKI

Direct impingement is a type of gas operation for a firearm that directs gas from a fired cartridge directly into the bolt carrier or slide assembly to cycle the action.

Unlike conventional gas-operated firearms, direct impingement does away with a separate gas cylinder, piston, and operating rod assembly.

High-pressure gas acts directly upon the bolt and carrier thereby saving weight, lowering manufacturing costs, and reducing the mass of the operating parts, and thereby the wear on mechanical parts due to movement.

The main disadvantage of direct impingement is that the breech of the firearm's firing mechanism becomes fouled more quickly due to being exposed to the residues of the burned cartridge propellant.

This is caused by particles suspended in high-temperature gas condensing on the bolt face and primary operating mechanism.

Both the French and Swedish rifles use a simple system whereby the gas tube acts as a piston with a cylinder recess in the bolt carrier.

The two best known examples of true DI are the French MAS-49/56 and the Swedish Ag m/42

These are actually quite similar to the AK system except the piston and cylinder are at the action end rather than the barrel end.

The AK is the fixed cylinder / moving piston version.

The MAS 49 is the moving cylinder / fixed piston version.

======] -> muzzle - AK
[====== -> muzzle - MAS 49

The forces are direct acting to separate the bolt carrier and the barrel, but are offset from the bore axis.

Originally Posted by WIKI

The original AR-10 action (later developed into the ArmaLite AR-15 and M16 rifle) designed by Eugene Stoner is commonly called a direct impingement system, but it does not utilize a conventional direct impingement system.

In U.S. Patent 2,951,424, the designer states:

″This invention is a true expanding gas system instead of the conventional impinging gas system.″

Gas is routed from a port in the barrel through a gas tube, directly to a chamber inside the bolt carrier.

The bolt within the bolt carrier is fitted with piston rings to contain the gas.

In effect, the bolt and carrier act as a gas piston and cylinder.

The AR system can almost be thought of as a hybrid.

It does not have a separate piston; it is integrated into the bolt.

It does not have a separate cylinder; it is integrated into the carrier.

The forces separate the bolt carrier and the bolt, and are inline with the bore axis.

In the end, it's all just semantics.

There are about 6 different arrangements for gas to cycle the action.

It comes down to the positives and negatives attributes of any particular implementation.