Would you guys say that the delayed blowback is inferior to gas operation?
Now, we are just discussing the operating principle not the guns.

Can see how it could.

No holes in the barrel.
No gas tube or piston.
No bolt rotation.

In theory, there is less stuff to screw with barrel harmonics, apply torque or otherwise cause disturbance to the barrel when firing.

Also, seems there would be less moving parts that would wear and need replacement.

Nope.

In larger calibers like .308 I find that gas guns (M1A, FAL, etc.) have a smoother recoil impulse than the HK91/G3. That's really the only negative I can think of.

Where the roller lock system really shines IMO is smaller calibers like 9mm. The HK94/MP5 system has to be the smoothest shooting 9mm carbine/smg platform I've ever used.

With A buffer in the 91 it's actually nicer than my fathers M1A to shoot. IMO

Since this is the HK forum, what about the P7's gas-delayed blowback....

Thanks for the info, some guy I was arguing with tried to convince me that a delayed blow back is inferior to the a gas system.
I don't see how, if anything its more accurate and just as reliable.

Not inferior; different.

Works well.  Some will hate because they don't have any roller guns.

The MG-42 is a roller design, and I don't hear anyone saying it's a bad gun.

The G3 is like the FN FAL but simpler and easy to clean,the roller delaysed blowback uses raw force built in to a compact assembly unit,it may not be as soft in operation as a gas operated but it is simpler and cheaper (i think).

The two systems are very diferent in nature,the gas operated came at a time of evolution in firearms that needed to move out of the manual reloading to automatic and with every first,the mechanical funcion tops every other need apart from it.

The early automatic weapons came from Hiram Maxim and John M. Browning.

Hiram Maxim "Cannot this great force, at present merely an inconvenience, be harnessed to a useful purpose?"

The First Automatic Weapon Patented by Maxim. (recoil operated)



John M. Browning "when he noticed something countless other
men had seen before, but had not thought worth remembering. Every time Browning fired, the bulrushes parted from the blast for quite a distance from the muzzle. To others this phenomenon meant nothing. But to Browning's mechanical mind it revealed a wasted, perfectly timed power source which could be utilized to operate the weapon's mechanism and produce sustained fire. Just as Maxim had observed the possibilities of the kick of a gun for harnessing the recoil, Browning likewise realized the potentialities of the muzzle blast..."

Browning's First Experimental Model of a Gas-Operated Automatic Firearm. (gas operated)



The roller delayed blowback came out of need as production cost was the important factor and the need was to perfect automatic operation due to the elimination of parts.

But there is also what defines a gas operated system,the first gas operated systems used a short recoil with the gas piston in the barrel, as the gas can move the barrel piston when it comes out,as the normal gas piston that can catch the gas at the end of the barrel (or a bit to the rear).

The John M. Browning MG used gas to operate a lever to operate the rest of the mechenism.

My dealer has a standard M16 and I have an HK93 with sear, as well as a V93 and C93. All the HK style guns in .223 have a much smoother cycle than the M16. And while there are things one can do to the M16 to make it smoother, there are also things that can be done to the 93. But if you're just talking about the basic design differences, the 93 is smoother.

As far as dependability, I wouldn't compare an DI AR to the HK. My HK style guns can shoot many more rounds without having feed or extraction problems than the ARs. The delayed roller system can get fairly dirty and still work reliably. My gas piston ARs are newer and I haven't been able to put enough rounds through them to make a comparison to the HKs. I have a Ruger SR-556 and a Sig 556 10" upper for my AR SBR. They both seem to go through any ammo I've tried (including Wolf and Tula) like a hot knife through butter, but I just don't have the round count yet to really compare.

However, to the OP and original question, it's sort of retarded to ask which system is better, in such an open-ended way. They each have advantages. When asking a question like this, you'd sound less like the new kid on the block (or a 15 year old mall ninja) if you'd ask about a specific aspect of the guns. You might as well get on a computer forum and ask, "Which is better, an Apple or Windows PC?"

The AR-10 and AR-15 system (as with the johnson) have use only inertia force to extract the case,as soon as the gas moves the carrier back to cam the head to rotate to unlock,only the remaining force from the fired shot moves the all bolt assembly back to extract the case.

The roller delayed blowback uses a constant,but delayed,rear motion that moves the case back (as a piston) over the bolt,this makes for a diferent mechanical extraction as the forces may be diferent.

A normal gas system with piston keeps a constant rear motion over the bolt as soon as the gas vents to the piston as with the M1 Garand/M14/AK,the short-recoil piston gives a initial kick over the bolt so it can unlock the bolt and extract the case as from then on it uses inertia force to recoil the bolt thest of the way,the normal gas piston (or long-stroke piston) may be safer as it assists the bolt operation and case extraction as soon as gas vents in to the piston all the way to the reas as from then on it is the recoil spring tention force that moves it front to strip/chamber and lock the bolt.

The gas delayed blowback is a mix of from a delayed blowback as it does not fully lock the bolt and of the AR-10/AR-15 as when the gas vents out it uses remaining inertia force to extract the case.



Top image,Mkb 42(H),gas operated tilting bolt.

Lower image,Gerät 06(H) STG45,roller delayed blowback.

As I said before, some guy I was arguing with tried to convince me that a delayed blow back is inferior to other gas system's, I don't see how, if anything its more accurate and just as reliable.
The question I had ask was simple and explicate, do you feel that the roller lock is inferior to gas operation (gas systems) don't remember asking which was better....My argument is that a delayed blow back is just as (if not more) efficient then other operating systems (But, I'm not sure about the FAMAS, it look's even more simpler but I know very little about it).

The FAMAS uses a lever delayed blowback.

"Lever-delayed blowback utilizes leverage to delay the opening of the breech.When the cartridge pushes against the bolt face, the lever moves the bolt carrier rearward at an accelerated rate relative to the light bolt. This leverage significantly increases resistance and slows the movement of the lightweight bolt. John Pedersen patented the first known design for a lever-delay system.The mechanism was adapted by Hungarian arms designer Pál Király (a.k.a. Paul de Kiraly) in the 1930s and first used in the Danuvia 43M submachine gun. Other weapons to use this system are the TKB-517/2B-A-40 assault rifles, the AVB-7.62 battle rifle, the San Cristobal .30 carbine, the FAMAS,the BSM/9 M1 and FNAB-43 submachine guns, the Hogue Avenger and Benelli B76 pistols, the Sterling 7.62 and AA-52 machine guns."

Schematic



The roller delayed blowback is in no way inferior to a gas operated system,it is just mechanicly diferent,it makes for a simpler mechenism and we can account for it as we used it in combat in a 3 front war,the mechenism is idiot proof...



Note:it can extract the fired case with no extractor (but not manualy...).

When I had seen the weapons that were submitted to the SOCOM trials, I felt they were all more complex then the M4. IMHO, that was moving in the wrong direction, they should be simpler then the M4. We don't need gas blocks, pistons, operating rods, or gas tubes or even rotating bolts, just a delayed blow back with the ability to change barrels easily.
Stoner had envisioned a weapon system that could go from rifle to carbine to belt feed, the AR15 never really lived up to that, but the stoner 63 did. I'm not suggesting that we go back to the 63 but IMHO, a modern weapon system like the 63 would have excel the trials, less production expensive then the M4, it could also solve problems with logistics.

But this is just an opinion.

It all depends on the capital that a nation as available,the delayed roolled blowback came out in the last years of WW2 germany,when capital and material as less,and even the bolt on a STG44 is simple but the structure to cover it is more expensive as it needs a gas tube,the structure in the STG45 is chaper as the bolt needs no gas tube.
there is a difference between pice time and war time production,pice time favors more expensive equipment with more funcionalities (bedazzled) as war time favors funcionality asnd cost per unit as it as the tendacy to get more spartan.
Originalt ArmaLite used the isea of a alluminium receiver so the structure could be lighter and simpler/faster to make,this idea was based in the wior done by germany with the sue of stamped metal receivers,but cheaper as it does not need the expensive stamping machinery and expertise,in a way the M4 carbine carries the same concept idea used by the Germans in WW2.
The roller delayed blowback was easy to accept in Germany as the German firearms industrie was always adverse to the use of a gas operated weapon due to the use of the drilled barrel and the long term problems that can come from it,so a delayed blowback with a barrel that needed no gas vent drilling was fantastic,as it was cheaper.

I always hear that the M4 is good enough until we get energy weapons, although there is some truth in this statement, I'm willing to bet that if a weapon is produced at only half the cost to DOD, and also at the same time addressing some of the reliability issues, DOD would be more then interested.

At the time,the idea of using small caliber ammunition originaly came from the Department of Defense and not from ArmaLite,but it did not stop the Springfield Armory from opposing and sabotaging the early AR-15 prototypes tested,industry lobbying alfo may have something to do wit it,in som cases perhaps.
The Springfield Armory also opposed the idea of using stamped metal in firearms and rigged tests against foreign firearms tested like the FN FAL (T48) to favor the U.S. made M14 (T44),as the M14 was developed and made by the Springfield Armory it was pretty naive or on on purpose to get other weapons to be tested it.

Technically, Armalite made the AR10 and submitted it for the 57 competition. The military picked the M14, but were so impressed with the AR10 design that they directed Armalite to go off and develop a small caliber version. That became the AR15. It mostly got evaluated in Vietnam, before we "officially" got involved. I guess Ruger liked the M14 better so they went off and developed the small caliber version of it (more or less) in the Mini 14.

Back in about 1985 was when I finally started collecting military style guns. And after looking at the AK47, AR15, and Mini 14... I ended up buying a Mini 14. It just looked like it had much more quality to it than the other two. I guess I still do, but I started learning more about the other characteristics and nature of the others. So I have a ton of ARs and AKs now. As well as HK hosts. I still only have one Mini 14.

Yes,the AR-10 was tested at the Springfield Armory,it failed but ArmaLite got a good insight to what the problems with the AR-10 had in serious testing (something that the S.A. was professional) and used the info from it to furder improve it,if you take a note at the original ArmaLite Fairchild AR-10 promo film,it is basically a "suck On It" to the S.A. testing.
Originaly,the driving force behind the development of the AR-10 (apart from the new bolt system) was also the NATO behind of the new 7.62 ammo,as all NATO armies used older ammo and older small arms so the new ammo was going to force all the NATO nations to adopt new small arms for it,this was a almost fuck up as new assault rifles were in testing using ammo similar to the German intermediate but the U.S. doctrine dictated that a stronger ammo was beter and weapons like the FN FAL prototype had to change for the new NATO 7.62 as the Soviet Union adopted a intermediate cartrige and the Soviet AK came out as a assault rifle as NATO was stuck with Combat Rifles...

...but the adoption of the AR-15 with its 5.56 was almost treason against NATO as if a conventional ground war was to start in Europe with the Soviet Union taking west Germany...or the all NATO nations would have to adopt the new U.S. 5.56 and the AR-15 (M-16)...or the U.S. would have to go back to the 7.62 M-14...

...butthe same thing went on in the Soviet Union as the adoption of the 5.56 by the U.S. during the Vietnam war this made the Soviets change from the M43 cartrige to the M74 with the new AK-74,but this did not pass on to all of the Warsaw Pact as some nations stayed with the AR-47 and AKM variats and with the old M43 cartrige,so incase of war,Continental NATO nations and Warsaw Pact would fight with the 7.62 NATO and 7.62 M43 ans the U.S. and the Soviet Russia would use the 5.56 and the M74 (5.45)...

Eugene Stoner and Mikhail Kalashnikov somewhat opposed the new smaller ammo prefering the older 7.62...

...sorry for going a bit off topic,but...

...the long stroke gas operation may be a bit havier using more mass but it is much more reliable then all other automatic operation systems,gas operation came in diferent system configuration and compering a gas operation that by it self is a generic term as to a roller delayed blowback that is a specific term to a unic system is a bit...

The long stroke gas operation system (M-1 Garand/M-14/AK-47) as less parts then a short recoil (FN FAL/AR-!&/AR-18),as it does not neen the second spring for the piston/rod,but it is hevier then the D.I.system (AR-10/AR-15).



It is better with case extraction as the gas assists the bolt as soon as it vents over the gas piston all the way to the rear,mechanicly it is almost perfect but it makes for a hevier rifle using more parts,the roller delayed blowback makes for a cheaper rifle as it uses less parts and the gas needs no drilling for a gas recoil vent hole,but it is also mechanicly good (apart from the need for the exoctic fluted chamber) as it uses the same raw force used in a  long stroke gas operation system but with less parts...



There are some advantages and disadvantages of a roller delayed blow back system.

" Advantages:

  -The barrel can generally be free floated, since there aren't any moving parts up front. This is unlike a gas operated mechanism, where part of the mechanism is hanging off one side of the barrel and disturbing the natural harmonics of the barrel. Free floating the barrel increases the accuracy of the weapon.
  - Unlike the straight blowback mechanism, this one can use higher powered ammunition.
  - When used with suitable ammunition that is designed for the weapon, this is a pretty reliable design.
  - Moderately cheap to manufacture.

Disadvantages:

   -This design definitely doesn't like wide varieties of ammunition. It is sensitive to factors such as the weight of the bullet or the type of case. Therefore, the ammunition used for this weapon needs to be good quality and manufactured to uniform standards, otherwise it could cause operating issues.
  - This is a design that can get dirty very quickly while using. It is fairly easy to clean up though.
  - It is a relatively complex system compared to some other designs, such as the AK-47 mechanism.
  - The locking delay can go down as the parts begin to wear out, chamber gets dirty or clean etc.
  -Cannot be tuned by a user, unlike a gas-operated mechanism with a regulator is."

But the simplest one is still the gas delayed blowback.
The roller delayed blowback,when invented,was the one that was more in tune with the German taste as it did not needed a drilled vent hole in the barrel and made for a much cheaper rifle,but as the war progressed against the germany,the germans developed simpler designs in the "Primitiv-Waffen-Programm".
The gas delayed blowback needs a driled hole to funcion but it is mechanically much simpler,as to the complicated bolt from the roller delayed,the gas delayed uses a bolt with no moving parts (apart from the firing pin/extractor/ejector).

The gas delayed Horn prototype uses a piston/lever pice that is forced to move up to catch and hold the bolt closed and when gas psi is reduced the piston moves back in as the bolt moves back,the Horn did not pass from a test prototype as the war ended and it was captured by the Soviets.





The gas delayed in the Volkssturmgewehr had driled holes almost at the end of the barrel,the gas vented out of the barrel in to a chamber and forced the sleeve to stay closed during fire,the sleeve was conected to the bolt.The Volkssturmgewehr used by the German Volkssturm forces.







Karl Barnitzke Volkssturmgewehr:

"Testing of a captured Gustloff Volkssturmgewehr at a Soviet GAU shooting range showed that it was rather inaccurate, with 50% of the shots at 100 m landing in a circle with 10.2 cm radius and with 100% of the shots at the same distance landing in a circle with a 19.8 cm radius. At 300 m these the corresponding radii were 25 and respectively 50.3 cm. The fixed sights of the Gustloff Volkssturmgewehr made aiming difficult because the Kurz patrone raised some 29 cm above the sightline at 100 m and dropped 43 cm below it at 300 m"

Kurt Horn Grossfuss Sturmgewehr:

"One of captured Grossfuss Sturmgewehrs was tested by the GAU. It fired about 1,900 rounds without stoppages. Its accuracy was basically on par with the MP 43, even though the length of its sighting line was considerably shorter (266 vs. 418 mm)."

"The Grossfuss Sturmgewehr used the same principle of gas-delayed blowback operation, but it was somewhat more efficient in the use of gas; its bolt weighted 0.8-0.9 kg compared to 1.4 kg in the Gustloff Volkssturmgewehr."

The more eficient gas operation is the Long Stroke (M1 Garand) as it uses the raw force from gas expantion to move back the gas piston/rod and bolt as it fully assists the bolt when extracting the case and moves the all bolt assembly to the rear.



The D.I. system used in the AR-10/AR-15 uses the gas expantion only to unlock the bolt as the resulting force from firing move the bolt back and to extract the case as problems with case extraction may cum up from time to time,the same with the Melving Johnson system.

The roller delayed blowback does the same as the long stroke system,but it uses the delayed force from gas expantion to assist in case extractionand to move the bolt assembly to the rear,but in a smaller and cheaper mechenism.

The Sringfield Armory did some work with the roller concept,not as a roller delayed blowback but a roller locked short stroke piston,a copy of the Mauser Gerät 03,known as the T-28.

















"...In developing the T28 Rifle, Cyril A. Moore sought to design a weapon that could be simple and inexpensive to manufacture. Moore's T28 was made of sheet metal stampings, simplified forgings and brazed assemblies. He was following the philosophy that had dominated German arms development during WWII. The German designers assumed that a weapon could be lost or destroyed before it wore out. Therefore, to cut down the cost of replacement they decided to develop small arms which could be turned out cheaply on punch presses and screw machines. Such weapons could also be made in most small metal shops where such equipment was in use.
The genealogy of the T28 goes back to the final wartime experiments at the Mauserwerke. Several incomplete developmental weapons were discovered by a Technical Team of the Allied Combined Intelligence Objectives Subcommittee (CIOS) when they ransacked the Mauser experimental shops at Oberndorf an Neckar. Samples of these weapons were forwarded to Moore at Springfield. He incorporated elements from two of these weapons into the T28.
A roller lock and two-piece bolt was common to the two Mauser designs. The forward section (bolt-head) contained two vertically mounted roller bearings. These roller lock the bolt when forced into the locking recesser by the tapered protrusion on the rear portion of the bolt (bolt extension). In one of the Mauser rifles, a short tappet piston gave an initial impulse to the bolt extension. As this section of the bolt moved to the rear, the extension ceased its wedging effect, allowing the rollers to be cammed back into the bolt-head. The whole bolt assembly then travelled to the rear propelled partly by the residual pressures in the chamber.
The Armory proceeded with the development of the T28 on a limited scale for nearly four years. A total of 11 T28 rifles were fabricated. These rifles were favorably received by the Aberdeen testing officers. Many of the weaknesses discovered in the early prototypes were corrected in later models. The Aberdeen report concluded that "the T28 has several advantages over present standard equipment but has a number of undesirable features. Further development is necessary in order to reduce malfunctions and the breakage of parts."
Nevertheless, the T28 rifle did not survive the limited budgets. Sometime in the winter of 1950-51, Colonel Rene Studler's office terminated the project so that the development funds could be used elsewhere..."

How would you defined efficient? I don’t know if I can agree with your statement about the long stroke piston being a more efficient system. One accomplishes the same with less using a delayed blow back. With the piston operation, one needs some type of gas block, operating rod, and gas port.

Very interesting read, I wonder why Springfield had decided to use the piston operation along with the roller lock on the T-28? I’m sure Springfield was aware of the advantage of not use the piston (light weight .30cal.).  

lol..off topic, but no problem, I love history! and its so funny how history repeats it self. The British 7mm was badass, a perfect intermediate round, way ahead of its time. But we told the Brits to forget it, that it was going to be a 7.62 world......just to replace it with 5.56.....now, today, here we are, looking at the 6.8 SPC (the same thing the Brits created X amount of years ago!) as a possible replacement to the 5.56 due to the better performance..lol I don't know why the rest of the world just doesn't understand us..lol

lol..Yeah, I'm guilty of this as well...



I'll let you guess which one is mine!....

I've always wondered if the AR15 was adopted because of the fact that it was the only practical rifle in 5.56....I know that Winchester had a dog in the fight but I can't think of anyone else..

Wen i say that the long stroke may be the more efficient,i mean within the gas operated system class,as to have a good level for comparison one as to use the best in the two classes,this because the roller delayed blowback system is alone in its own class.

Lond Stroke Vs Roller Delayed Blowback

The British intermediate rifle cartridge was the .280 British,it was used in the EM-2 and with one FN FAL prototype.

.280 FN FAL





FAL Prototype .280/30

8mm Kurz prototype

The Harrington & Richardson T223 rifle was a caliber .223 roller delayed blowback made in the U.S.

At the time of the T-28,Karl Maier was working for the Springfield Armory,under the operation "Paperclip",and they had captured Gerät 06 (short stroke roller lock) as Gerät 06H (roller delayed blowback) units at their disposition,the T-28 was a short stroke roller lock.



"The man responsible for the original concept was Dr. Karl Maier, a Mauser mathematical physicist. After the war Dr. Maier was captured by the Americans and eventually came to the United States as part of 'Project Paperclip,' a program designed to keep German scientists out of the hands of the Russians. In fact, Dr. Maier spent many years working at the Springfield Armory before becoming an independent firearms consultant. Today, Dr. Maier is enjoying a quiet retirement in his native Germany."

Karl Maier-Primer Setback Analysis Springfield Armory Memorandum Report SA-MR11-1062,October 1950.

T-28 "The T28 explored,under the direction of our rifle design engineer,Cy Moore,the possibility of forming rifles from sheet metal,wherein the wooden stock would be eliminated by bolting together two sheet metal stampings.The rifle also employed a roller type lock.This rifle explored features which had been noted in the german Gerat weapon,The T28 was discontinued,primerely due to trouble with the sheet metal stock."

This is interesting..."The German designers assumed that a weapon could be lost or destroyed before it wore out. Therefore, to cut down the cost of replacement they decided to develop small arms which could be turned out cheaply on punch presses and screw machines. Such weapons could also be made in most small metal shops where such equipment was in use."

This is basically the logical reason for the german development of the roller delayed blowback.

"Notes: In developing the T28 Rifle, Cyril A. Moore sought to design a weapon that could be simple and inexpensive to manufacture. Moore's T28 was made of sheet metal stampings, simplified forgings and brazed assemblies. He was following the philosophy that had dominated German arms development during WWII. The German designers assumed that a weapon could be lost or destroyed before it wore out. Therefore, to cut down the cost of replacement they decided to develop small arms which could be turned out cheaply on punch presses and screw machines. Such weapons could also be made in most small metal shops where such equipment was in use.
The genealogy of the T28 goes back to the final wartime experiments at the Mauserwerke. Several incomplete developmental weapons were discovered by a Technical Team of the Allied Combined Intelligence Objectives Subcommittee (CIOS) when they ransacked the Mauser experimental shops at Oberndorf an Neckar. Samples of these weapons were forwarded to Moore at Springfield. He incorporated elements from two of these weapons into the T28.
A roller lock and two-piece bolt was common to the two Mauser designs. The forward section (bolt-head) contained two vertically mounted roller bearings. These roller lock the bolt when forced into the locking recesser by the tapered protrusion on the rear portion of the bolt (bolt extension). In one of the Mauser rifles, a short tappet piston gave an initial impulse to the bolt extension. As this section of the bolt moved to the rear, the extension ceased its wedging effect, allowing the rollers to be cammed back into the bolt-head. The whole bolt assembly then travelled to the rear propelled partly by the residual pressures in the chamber.
The Armory proceeded with the development of the T28 on a limited scale for nearly four years. A total of 11 T28 rifles were fabricated. These rifles were favorably received by the Aberdeen testing officers. Many of the weaknesses discovered in the early prototypes were corrected in later models. The Aberdeen report concluded that "the T28 has several advantages over present standard equipment but has a number of undesirable features. Further development is necessary in order to reduce malfunctions and the breakage of parts."
Nevertheless, the T28 rifle did not survive the limited budgets. Sometime in the winter of 1950-51, Colonel Rene Studler's office terminated the project so that the development funds could be used elsewhere."

Article from GUNS MAGAZINE MAY 1955

"THE GREAT RIFLE CONTROVERSY

WHILE BELGIAN FN SEEMS SHOO-IN FOR SELECTION AS NATO RIFLE, U.S. ARMS MAKERS SEE VITAL FLAW IN GUN DESIGNATED AS T-48: IT IS VIRTUALLY IDENTICAL WITH WEAPON ABANDONED BY RUSSIANS"

"...The FN is essentially identical to a Russian rifle abandoned by the Soviets during World War I1 as unreliable! The Belgian gun the US. is considering for adoption is of the same pattern as the Russian Tokarev, a gas-operated shoulder rifle of tipping bolt design, resembling in some principles the old Savage Model 99 lever rifle so familiar to American sportsmen. And to shoot in that rifle, which
the Army test officers presently designated the "T-48," we have adopted a cartridge which is remarkably similar to the .300 Savage, old, reliable deer killer!..."

" NOT MADE HERE"

"Choices of weapons was left as much as possible up to the tastes of the individual SEAL. The squad had to carry a balance of firepower, but that wasn't any problem to accomplish. For myself, I had taken a liking to the Harrington & Richardson T223 rifle. The H&R T223 was an imported version of the German Heckler & Koch HK33. The weapon had been available for a few years, and the Team was evaluating it in combat.
We had a lot of experimental weapons at the Team, and when I went over it was suggested that I take the T223 over and see what I thought about it. Though the weapon is slightly heavier than an M16, it fires the same ammunition, so ammo supply wouldn't be a problem. The Team had been using the AR-15/M16 rifles since its first days, but we only had the twenty-round magazines. There were some thirty-round magazines around, but they were few in number and hard to come by. One thing that immediately made the T223 appeal to me was the fact that it come with forty-round magazines.
I liked the weapon. It was a lot easier to clean and maintain than the M16 and worked well in the jungle environment. While the other men of the platoon would be just starting to clean their weapons after an op, I would already be done and moving on to something else. The T223 (HK33) was good but it was a foreign (German) weapon and suffered from the 'not made here'"

New hk's are not designed with rollers.  Scar, Knights , Tavor etc. are not using rollers so the idea that the most modern and well thought out rifle designs ever use pistons or strait blow back says a lot.
I personally think the roller guns work fine but they need personal attention to each gun to get the roller size and timing just perfect or they will not work and if this changes ever so slightly you have a rifle that will not work.  Once they do work they tend to stay working but I would pick a piston system in a rifle and blow back in a sub gun before the delayed roller.

I own an HK53 and it has always worked fine but I feel safer with a piston or even an AR.

If you want to win the argument just let your buddies read this:

http://www.geekgunman.com/USA_test_HKRifles.pdf

They had to remove parts in order to force the test rifles to fail.