Gas piston question

ChromeLined · #1 08-02-06, 02:02

So what do you guys think is the closest piston system for the AR available to us thats like or operates like the H&K 416 system?

K.L. Davis · #2 08-02-06, 02:05

The HK does nothing more than push back on a modified bolt key with an oprod, just like any of the half dozen other systems out there... where they are unique is in how the piston is regulated and the gas vented -- it is the G36 design and protected by patent.

Steel_Weasel · #3 08-02-06, 11:41

Quote:

Originally Posted by ChromeLined

So what do you guys think is the closest piston system for the AR available to us thats like or operates like the H&K 416 system?

The closest one is from a company that many people wouldn't buy from right now.

K.L. Davis · #4 08-02-06, 14:28

Quote:

Originally Posted by Steel_Weasel

The closest one is from a company that many people wouldn't buy from right now.

Actually the LW entry does not use a true piston per se... it uses a "cup and spigot" design made popular years ago by rifles such as the AR18/180 -- it is simple design and regulates itself well.

POF uses a cartridge piston design... naturally there were some early growing pains and learning, but Frank has stayed true to continued improvment and has a really nice system.

The HK system has the piston set rather high above the bore axis... this is the reason behind some of modifications that are peculiar to the design.

All of the systems suffer the same problems -- back about 20 years ago the systems would shear bolt keys with frightening predictability, today's systems have beefed up and modified keys... now we are seeing that "bolt tilt" is becoming a concern.

The concept is still in genisus... whereas in the past, designers simply gave up when presented with problems, people today are putting some clever thought into overcoming these issues. I would speculate to say that the future will see a design that is not a retrofit to the existing platform and bares little resemblance to what is out there now.

ChromeLined · #5 08-03-06, 23:41

Thanks guys..im gonna give the POF a shot

Nitrox · #6 08-04-06, 00:19

.....

**VA_Dinger** · #7 08-04-06, 00:30

Quote:

Originally Posted by ChromeLined

Thanks guys..im gonna give the POF a shot

Good decision

JLM · #8 08-04-06, 02:38

KL, can you talk about the Colt guns just for comparison purposes?

mtdawg169 · #9 08-04-06, 09:31

I have heard about concerns over bolt tilt also. What is it & what concerns does it create exactly?

TigerStripe · #10 08-05-06, 21:17

Quote:

Originally Posted by mtdawg169

I have heard about concerns over bolt tilt also. What is it & what concerns does it create exactly?

I'd like to know that too. For now, I'd go with a POF or Colt.

TS

Steel_Weasel · #11 08-07-06, 12:57

Quote:

Originally Posted by mtdawg169

I have heard about concerns over bolt tilt also. What is it & what concerns does it create exactly?

Let me preface this by saying that I'm not an engineer and don't know alot of the technical terms related to 'bolt tilt' so I will try and describe it, as much as I know, in laymans terms.

In DI, the gas enters the bolt carrier key inline with the direction of bolt movement. With piston systems (416, LW, ?) the momentum imparted to the 'piston' strikes the bolt carrier 'head' (there is no longer a traditional key) is transferred at an angle. From what I know, this is mostly because the front gas port is lower than the entry port in the upper receiver resulting in the back of the bolt carrier tilting downward when the piston strikes the bolt carrier head.

Bolt tilt is mitigated/eliminated in the before mention systems by the use of a special bolt carrier with a slightly larger profile at the rear to phyiscally prevent the bolt from tipping.

I don't know if the POF system has bolt tilt issues as it's bolts do not have this 'thickened' rear. I'm speculating that POF doesn't have bolt tilt because it's front gas port is higher and allows the piston to impart momentum along the same axis as a DI system.

Did I get it right ?

K.L. Davis · #12 08-07-06, 13:34

Quote:

Originally Posted by Steel_Weasel

Let me preface this by saying that I'm not an engineer and don't know alot of the technical terms related to 'bolt tilt' so I will try and describe it, as much as I know, in laymans terms.

In DI, the gas enters the bolt carrier key inline with the direction of bolt movement. With piston systems (416, LW, ?) the momentum imparted to the 'piston' strikes the bolt carrier 'head' (there is no longer a traditional key) is transferred at an angle. From what I know, this is mostly because the front gas port is lower than the entry port in the upper receiver resulting in the back of the bolt carrier tilting downward when the piston strikes the bolt carrier head.

Bolt tilt is mitigated/eliminated in the before mention systems by the use of a special bolt carrier with a slightly larger profile at the rear to phyiscally prevent the bolt from tipping.

I don't know if the POF system has bolt tilt issues as it's bolts do not have this 'thickened' rear. I'm speculating that POF doesn't have bolt tilt because it's front gas port is higher and allows the piston to impart momentum along the same axis as a DI system.

Did I get it right ?

Pretty close... I have to say that I am not avoiding this topic, but a lot of the research and design work done by a manufacturer to eliminate the problem needs to be treated as trade secret for now -- But I can say that a lot of work is being done to eliminate the problem. Guess what I am is saying is that there are potential answers out there, but they have come at the investment of the time and money of a couple of good people... so let's let them do with that info what they will.

Couple of things: It does not matter where the front of the oprod is, the length of the arm at the bolt is the same for all the designs (actually, one company is a little longer) -- no design that uses a modified AR bolt carrier is exempt from the problem.

Certain type of "pistons" are worse than others, as some designs push in a rather steady, slow way... while others push with a sudden, snappy force.

Redesigned bolts do not prevent the problem, they simply take a little onger to wear down...

mtdawg169 · #13 08-07-06, 14:22

Quote:

Originally Posted by K.L. Davis

Pretty close... I have to say that I am not avoiding this topic, but a lot of the research and design work done by a manufacturer to eliminate the problem needs to be treated as trade secret for now -- But I can say that a lot of work is being done to eliminate the problem. Guess what I am is saying is that there are potential answers out there, but they have come at the investment of the time and money of a couple of good people... so let's let them do with that info what they will.

Couple of things: It does not matter where the front of the oprod is, the length of the arm at the bolt is the same for all the designs (actually, one company is a little longer) -- no design that uses a modified AR bolt carrier is exempt from the problem.

Certain type of "pistons" are worse than others, as some designs push in a rather steady, slow way... while others push with a sudden, snappy force.

Redesigned bolts do not prevent the problem, they simply take a little onger to wear down...

OK, so other than obvious potential problems with wear on the upper receiver & bolt carrier, what are the other "side effects" of bolt tilt? Is it a wear issue or does it affect extraction, reliability, etc.?

l2e · #14 08-07-06, 15:56

Not to turn this into this system is better than that system, but I have a shorty POF gas piston upper and have around 3k-5k rounds through it (Wolf mainly) and have yet to clean it. It still runs perfect. I have a buddy who just got a LW and if their QC is any indication of their piston design, then they can keep their rifle. The rifle came with surface rust all over the rifle...not acceptable. I have bought and sold many a rifle and never seen that bad of QC or lack thereof.

SuicideHz · #15 08-07-06, 16:23

Quote:

Originally Posted by l2e

Not to turn this into this system is better than that system, but I have a shorty POF gas piston upper and have around 3k-5k rounds through it (Wolf mainly) and have yet to clean it. It still runs perfect. I have a buddy who just got a LW and if their QC is any indication of their piston design, then they can keep their rifle. The rifle came with surface rust all over the rifle...not acceptable. I have bought and sold many a rifle and never seen that bad of QC or lack thereof.

You definitely made the better choice.

ChromeLined · #16 08-07-06, 22:56

Surface rust evevn on the upper and lower? god where was it kept before shipping.

l2e · #17 08-08-06, 13:06

Just off the top of my head, there was an enormous amount of surface rust on the bolt catch and ejection door. Then there was some minor on the FSB. Just unacceptable.

variablebinary · #18 08-08-06, 14:12

Quote:

Originally Posted by ChromeLined

So what do you guys think is the closest piston system for the AR available to us thats like or operates like the H&K 416 system?

In terms of operation I cant say which is more like the HK, but I do like the POF system. For the price they give you the world in terms of features.

Also POF is as close as we have to a piston standard currently, with both Bushmaster and DSA choosing them which should make for easier parts buying and competition.

On top of that the POF guys are top notch and of good character as far as I can see.

ChromeLined · #19 08-09-06, 22:26

Thanks Variablebinary...im a norotic like that..with Bushy and DSA using it that makes it kind of the standard in piston systems.What does POF charge for an upper and can they do it on any barrel legnth.I emaile Bushy and they said they only do it on a 16" M4 profile..I want a 14.5/phantom HBAR A2 upper and can it be done with a standard FSB in place?...thanks...Dave

variablebinary · #20 08-10-06, 01:30

Quote:

Originally Posted by ChromeLined

Thanks Variablebinary...im a norotic like that..with Bushy and DSA using it that makes it kind of the standard in piston systems.What does POF charge for an upper and can they do it on any barrel legnth.I emaile Bushy and they said they only do it on a 16" M4 profile..I want a 14.5/phantom HBAR A2 upper and can it be done with a standard FSB in place?...thanks...Dave

Contact POF. They seem to build almost any config. AFAIK they have a 14.5" version here is a small pic