View Full Version : Even Known Good Companies Can Produce Garbage
I found an FN barrel on sale at Midway for $188. Looked like a screaming deal on a known good barrel, so I snagged one. I posted it in the good deals thread and when I tried to post a link, it was gone.
This is the sticker on the box, it came in a sealed Metal-Guard plastic sleeve.
https://uploads.tapatalk-cdn.com/20220415/4cafe8e0e0534564ff9e1e9a3066ef99.jpg
When I went to install the gas tube it was short. I had a carbine length tube in stock and it didn’t even make it to the hole in the upper.
This raised some red flags as it is clearly marked carbine gas, yet when I measured, sure enough it’s a mid length. No issue for me as either will work when properly gassed.
Next step was to gauge the gas port. Turns out it was smaller than my smallest pin gauge of .061, no way that would cycle a mid length gas system.
What to do? I figured if I return it I won’t get another barrel and I had already dimpled the side opposite the gas port, so I decided to try and carefully drill out the gas port to .077 which is the closest I could get with a bit I own.
https://uploads.tapatalk-cdn.com/20220415/b618aa06aa194f5d43072c1cce6a6999.jpg
I went slowly, with a new bit, using my Bosch hand drill. (I don't have a drill press at this house, but I have several at another.) It went perfectly, I was able to stop before punching through and hitting the inside of the barrel. I scoped the inside of the barrel and the inside of the hole is extremely clean and free of any burrs.
Guaged it again and it measured .077 which should cycle perfectly once my mid-length gas tubes arrive.
Bottom line here is to have the tools on hand to check and fix your shit. Even the best companies can produce garbage, at times.
Button rifled means it was not CHF, so aftermarket? What are the markings?
Button rifled means it was not CHF, so aftermarket? What are the markings?
https://uploads.tapatalk-cdn.com/20220415/681bf68d42fc33821e5ff7f7e55d4d3f.jpg
The button rifling doesn’t bother me much as I already have a bunch.
The only other marking is 556 NATO stamped near the muzzle.
You had a good opportunity to get the perfect port size and you hogged it out with a hand drill.
Way to go.
You had a good opportunity to get the perfect port size and you hogged it out with a hand drill.
Way to go.
.077" isn't bad for a middy at all assuming no suppressor attached. Even then it wouldn't be terrible.
I am curious. Why would you enlarge the gas port size before assembling and shooting the weapon?
.061" would be very lean for a middy. That said, I would not be using a hand drill. And I would have started with a reamer around .073" or so. But the known port size for middy is .076-.080"
I am curious. Why would you enlarge the gas port size before assembling and shooting the weapon?
Because .061 wasn’t close to fitting, so that port was probably .057ish and I saw no good reason to assemble it in that state.
No way it would have cycled properly at that size.
Because .061 wasn’t close to fitting, so that port was probably .057ish and I saw no good reason to assemble it in that state.
No way it would have cycled properly at that size.
Interesting. Might have been some special run they did for someone exclusively for suppressor use.
With the mislabel and wrong tube? I think they just are suffering from what many companies are these days.... Imbecile employees.
I am curious. Why would you enlarge the gas port size before assembling and shooting the weapon?
THIS.
The proper port size is not determined by barrel length alone.
THIS.
The proper port size is not determined by barrel length alone.
But there is known port sizes for given lengths and gas systems. It's not like manufacturers custom tune every port for every barrel.
Every Colt M4 port is the SAME SIZE. They don't test fire it and tear it down to give it a little more umph.
Five_Point_Five_Six
04-15-22, 17:58
Hand drill? Lmao this is why I'd never buy a home build.
I’d be shocked had it run before modification. That sounds way outa range for a unsuppressed middy. Would have liked to see it, though.
OP, next time chuck it on the EE with full disclosure.
@Clint , you have any thoughts?
Because .061 wasn’t close to fitting, so that port was probably .057ish and I saw no good reason to assemble it in that state.
No way it would have cycled properly at that size.
Roger that. I am of the opinion that you won't know for certain if the weapon will cycle unless you try.
It is easier to remove material than to replace it. If for no other reason, I would have tried shooting the weapon with the smaller gas port and collected data about failures and successful operation for a variety of cartridges with varying bullet weights. You can always open the gas port up later, but find it difficult to make it smaller if you went too far.
Charts are for reference, results are for finality.
Let us know how this turns out with ammunition in the 55 g to 77g range and if you feel the weapon is overgassed or properly gassed.
Hand drill? Lmao this is why I'd never buy a home build.
You want to see video of the gas port from the bore side?
I wouldn’t sell you anything regardless.
You can be an asshole, just try not to be a SMUG asshole in my thread. You add no value here. Punk.
Roger that. I am of the opinion that you won't know for certain if the weapon will cycle unless you try.
It is easier to remove material than to replace it. If for no other reason, I would have tried shooting the weapon with the smaller gas port and collected data about failures and successful operation for a variety of cartridges with varying bullet weights. You can always open the gas port up later, but find it difficult to make it smaller if you went too far.
Charts are for reference, results are for finality.
Let us know how this turns out with ammunition in the 55 g to 77g range and if you feel the weapon is overgassed or properly gassed.
I don’t necessarily disagree with you.
However I was in the process of assembling and figured I would try to put it together right the first time and I don’t think I went too far with the port size, even though I can’t reverse it.
If you ever have to drill another port, put a cleaning rod in the bore and drill away.
If you ever have to drill another port, put a cleaning rod in the bore and drill away.
Good tip, thanks!
Mysteryman
04-16-22, 01:06
You want to see video of the gas port from the bore side?
I wouldn’t sell you anything regardless.
You can be an asshole, just try not to be a SMUG asshole in my thread. You add no value here. Punk.
Your thread? What, you own M4C.net now? You STARTED a thread where you admitted to doing some rather stupid things to an otherwise factory barrel. Can't take the criticism don't post your story for all to read.
Leonidas24
04-16-22, 01:32
.077" isn't bad for a middy at all assuming no suppressor attached. Even then it wouldn't be terrible.
It's not "bad" but it is on the larger side. Most mfrs of repute are sizing their 16" mid ports at .076, while Colt at one point had .071 on the 6960 CCU. I have a Centurion 16" mid choked down to .071 with a BRT gas block insert and it runs everything in all temps with an A5H1, and with considerably less felt recoil than "factory" offerings.
OP: Good job on the fix. I personally would have went with a #49 or even #50 bit, or better yet step-drilled it up in size with reamers. But, considering what you had on hand not a bad job.
I’m just curious because it relates to the OP’s situation. During the barrel manufacturing process (like at FN) are the gas port holes drilled first and then it gets chrome lined, or the opposite? I ask this because I read enlarging the gas port at home can chip parts of the chrome lining off inside the barrel if you don’t have the exact machining for it & should only be done at the factory etc., but then again that might not be the case. Does anyone know? Thanks.
Five_Point_Five_Six
04-16-22, 08:33
You want to see video of the gas port from the bore side?
I wouldn’t sell you anything regardless.
You can be an asshole, just try not to be a SMUG asshole in my thread. You add no value here. Punk.
You sound like the lefties melting down over Elon buying Twitter.
I don’t necessarily disagree with you.
However I was in the process of assembling and figured I would try to put it together right the first time and I don’t think I went too far with the port size, even though I can’t reverse it.
Let us know how it functions with a variety of ammunition. If it functions, but appears to be slightly over gassed, please share that as well.
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