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Hello, I'm mtdawg169 and I'm a parts snob.
- Thread starter mtdawg169
- Start date
Now, you done gone too far!
You can't go wrong with Colt. Up until recently, my only complaint against them was that they didn't offer a midlength gas system. Now they do, along with a solid rail from Centurion Arms.
Great, now we'll have to wash this thread with clorox...
Something that we haven't touched on in the thread is gas ports. First, it's important to point out that there is only a "spec" for barrel lengths in military use. So that means, 10.3/10.5, 14.5, 18 & 20" barrels. (speaking only about 5.56 NATO and carbine or rifle length gas systems)
16 carbine gassed barrels generally run well with the M4 / 14.5 port size.
Generally speaking, whatever port size Colt uses in their commercial equivalent (10.5, 14.5, 16 & 20") is the correct size gas port. Further, Colt port sizes would be rightly considered the correct port size for any barrel length and gas system combination they offer. Why? Because no one has spent the time and money they have, to find the sweet spot between too much and too little gas, as Colt has. End of discussion.
Midlength is a commercial gas system length. There is no spec. HOWEVER, there is an optimum size for 14.5/16 midlengths that has been found through a great deal of R&D by companies like Noveske, BCM, etc over the years.
The spec for the 18" rifle gassed SPR barrel is specific to the Mk12 series of rifles.
Now here's where it gets interesting. If there are clear examples of companies that have it figured out within the industry, why is it so stinking hard for everyone else to get right? All it would take is to buy a few samples and a good pin guage set on Amazon. But they don't.
Part of the reason has always been that some companies don't want to deal with complaints or returns when the customer shoots weak, underpowered ammunition. This has always been the case, all the way back to armalite, bushmaster, dpms, RRA in the 80's and 90's. Overgassing was and still is typical of these brands and many others. These days, it's many many more.
Another reason is simple. Tooling costs. It's one of cost effectiveness, tooling costs, production efficiency and quality control. Huh? So this is how it works. The port is drilled in the barrel, down to a thousandth of an inch in tolerance. This requires very precise drilling and reaming. These tools wear out. Well, if you're a high QC shop that adheres to the Idea that Overgassing is a bad thing (it is by the way), that means that you're going to be changing tooling much more often. It also means that you will spend much more time performing QC in order to monitor the end product and be sure it meets your strict tolerance for port size. It's just flat out more expensive.
The budget shop takes a different approach. They start larger. This allows the tools to wear longer, cutting a smaller hole as the tools wear out. And they swap them out when ports near the minimum acceptable port size. A wider acceptance criteria, results in less down time, higher efficiency and lower production cost. They do the same thing with chamber reamers. Ever wonder how a barrel marked 5.56 NATO could actually NOT be? Easy, they change chamber reamers less often. As it wears out, the chamber is cut undersized. (I'm looking at you bushmaster, dpms and RRA).
The third reason that so many shops don't get port sizes right, is that they are either lazy or they just have no idea what they are doing in the first place. I've literally had companies be dumbstruck when you asked them about their gas port size. As if, they never gave much thought to it. Many of these new budget manufacturers simply beleive that AR's really are Legos. They buy parts in bulk, accepting whatever the supplier is willing to sell them, and they just slap it together. Some of them actually give it a C- effort and try to reverse engineer their specs. But they apparently don't know what a pin guage is or how to measure a hole. So they throw some harbor freight calipers on there and WECSOG that sucker. What they don't understand, is that a two or three thousandths difference in port size, is an exponential increase in gas flow.
These are the people you're buying from. And I don't really want to start naming names and insulting your brand favorite. So let's just say that very few get it right. Heck, sometimes even the good guys get it wrong.
For example, Daniel Defense, who I hold in very high regard, completely screwed the pooch on the civilian Mk18. It's a completely different port size than the contract guns they make for the military. And it's huge compared to the spec port size. They did this for one simple reason, even if it was the wrong reason. 10.5" AR's are freaking picky eaters. Especially when you suppress them. For the contract guns, the spec had already been determined by CRANE. It was a known good for running M855 and other NATO spec ammunition in a 10.5" barrel, both suppressed and unsuppressed. However, civilians have a plethora of ammunition to choose from. So, DD opened the port size to ensure the guns would run, no matter what. Personally, I think that was a bad decision. But at least DD understood what they were doing and why. Most of the manufacturers out there can't say the same.
Just another case in point, to explain why AR's are NOT Legos. Yes, the parts may all fit together, but the quality of those parts can have a dramatic effect on performance and reliability.
16 carbine gassed barrels generally run well with the M4 / 14.5 port size.
Generally speaking, whatever port size Colt uses in their commercial equivalent (10.5, 14.5, 16 & 20") is the correct size gas port. Further, Colt port sizes would be rightly considered the correct port size for any barrel length and gas system combination they offer. Why? Because no one has spent the time and money they have, to find the sweet spot between too much and too little gas, as Colt has. End of discussion.
Midlength is a commercial gas system length. There is no spec. HOWEVER, there is an optimum size for 14.5/16 midlengths that has been found through a great deal of R&D by companies like Noveske, BCM, etc over the years.
The spec for the 18" rifle gassed SPR barrel is specific to the Mk12 series of rifles.
Now here's where it gets interesting. If there are clear examples of companies that have it figured out within the industry, why is it so stinking hard for everyone else to get right? All it would take is to buy a few samples and a good pin guage set on Amazon. But they don't.
Part of the reason has always been that some companies don't want to deal with complaints or returns when the customer shoots weak, underpowered ammunition. This has always been the case, all the way back to armalite, bushmaster, dpms, RRA in the 80's and 90's. Overgassing was and still is typical of these brands and many others. These days, it's many many more.
Another reason is simple. Tooling costs. It's one of cost effectiveness, tooling costs, production efficiency and quality control. Huh? So this is how it works. The port is drilled in the barrel, down to a thousandth of an inch in tolerance. This requires very precise drilling and reaming. These tools wear out. Well, if you're a high QC shop that adheres to the Idea that Overgassing is a bad thing (it is by the way), that means that you're going to be changing tooling much more often. It also means that you will spend much more time performing QC in order to monitor the end product and be sure it meets your strict tolerance for port size. It's just flat out more expensive.
The budget shop takes a different approach. They start larger. This allows the tools to wear longer, cutting a smaller hole as the tools wear out. And they swap them out when ports near the minimum acceptable port size. A wider acceptance criteria, results in less down time, higher efficiency and lower production cost. They do the same thing with chamber reamers. Ever wonder how a barrel marked 5.56 NATO could actually NOT be? Easy, they change chamber reamers less often. As it wears out, the chamber is cut undersized. (I'm looking at you bushmaster, dpms and RRA).
The third reason that so many shops don't get port sizes right, is that they are either lazy or they just have no idea what they are doing in the first place. I've literally had companies be dumbstruck when you asked them about their gas port size. As if, they never gave much thought to it. Many of these new budget manufacturers simply beleive that AR's really are Legos. They buy parts in bulk, accepting whatever the supplier is willing to sell them, and they just slap it together. Some of them actually give it a C- effort and try to reverse engineer their specs. But they apparently don't know what a pin guage is or how to measure a hole. So they throw some harbor freight calipers on there and WECSOG that sucker. What they don't understand, is that a two or three thousandths difference in port size, is an exponential increase in gas flow.
These are the people you're buying from. And I don't really want to start naming names and insulting your brand favorite. So let's just say that very few get it right. Heck, sometimes even the good guys get it wrong.
For example, Daniel Defense, who I hold in very high regard, completely screwed the pooch on the civilian Mk18. It's a completely different port size than the contract guns they make for the military. And it's huge compared to the spec port size. They did this for one simple reason, even if it was the wrong reason. 10.5" AR's are freaking picky eaters. Especially when you suppress them. For the contract guns, the spec had already been determined by CRANE. It was a known good for running M855 and other NATO spec ammunition in a 10.5" barrel, both suppressed and unsuppressed. However, civilians have a plethora of ammunition to choose from. So, DD opened the port size to ensure the guns would run, no matter what. Personally, I think that was a bad decision. But at least DD understood what they were doing and why. Most of the manufacturers out there can't say the same.
Just another case in point, to explain why AR's are NOT Legos. Yes, the parts may all fit together, but the quality of those parts can have a dramatic effect on performance and reliability.
I have to make that wait all the time. I hate it. Lol.Waiting for dollars and desire to align.
You think P&S would be irritated if you posted a screen shot of that gas port size table they have started?
I'll ask to see if it's shareable outside of the group.
