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Number of Ports and Size of Ports


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I've currently got my bolt, carrier, and FCG sent to Pauly and I'm fixing to take my gun to have the barrel shortened and the JTE comp brake permanently attached. My gun has 3 ports and while it's at the gunsmith I was considering having the ports sized, etc.

 

My question is should I stay with 3 ports, if so what is the optimal size? Or should I have a 4th port drilled, and if so what is the optimal size? If you need any specifics about my gun please let me know and I can provide the details. Thanks.

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3 ports at 3/32" (0.093") works pretty good for me. I have 3 at 0.093" and a 4th at 5/64" and it never fails to eject. I have a MD arms gas adjustment Plug and if I turn the gas all the way up it will throw the winchester universal loads almost 10 ft.

Edited by mordamer
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I lied. I took my gas block off and I have 4 ports at .070". My barrel will be 14.2" and muzzle brake 4". I'm gonna go ahead and drill out to .078". Also think I'm going to try out the TAC47 autoplug in place of the MD Arms that is on it. My gun runs anything and everything through stick mags currently but FTEs are common when I try the Winchester Universal with the MD Arms Drum. Honestly feel like it would run after the profile and polish but I want to go ahead and enlarge the ports and try the autoplug. My gun is one of the 2011 models with 4 ports and no side rail, etc.

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Will do. Here's the before, except for a few minor things like Krebs Ghost Ring sights and an extended mag release. Unfortunately can't take any now because it's stripped down to nothing but the receiver, barrel, and gas block. I'm getting a very reasonably price IMO on the gunsmithing, looking at about $80 which is a good bit cheaper than other places I checked and is by a more qualified gunsmith with quite a bit of Saiga experience.

 

172C1FF7-5E68-442B-B6F9-4C5878F29EDD-116

Edited by swimbikerun247
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Your going to need to go up to probably 4ports at .093" minimum due to chopping 4" off. Even though youre going to perm attach a muzzle break, it will not act like an 19" barrel due to the ports and such. 4 ports at .078" is what gets most factory guns running reliably.



Actually, I would look into adding a 5th port at .078" and go from there.

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Your going to need to go up to probably 4ports at .093" minimum due to chopping 4" off. Even though youre going to perm attach a muzzle break, it will not act like an 19" barrel due to the ports and such. 4 ports at .078" is what gets most factory guns running reliably.

 

Actually, I would look into adding a 5th port at .078" and go from there.

No 5th port. More ports let more fouling thru.

 

Ideally you want 3 ports. 4 factory ports are "ok" but the problem with drilling them bigger is that the diamond shaped piece that is left in the middle can break off. So if you have 4, the absolute right way to increase them is, to not drill them, but mill them so that you are taking material off of the outside of the holes away from this center area.

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By milling, you can open the hole to the outside of the pattern, and not take off material to the sides. This keeps the interior section as strong as possible so it doesn't crack and blow out. Drilling enlarges the entire hole and weakens the interior section.

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5 @ .078-.080"ish

 

Assuming everything else is ideal, this should easily make the weapon eject light bulk at 15" while using factory springs and a factory puck. Add the 5th to the left or right rear and relieve gas block only if the shadow of the gas block orifice on the barrel looks like there will be a flow issue where the 5th port is going. The shadow tells you where to put additional ports and whether or not work needs to be done to the gas block. The gas does not have to be allowed a completely clear shot into the interior of gas block. The pressure merely needs to enter the system and as long as the port is not directly covered at the surface, it will do that. Do not disturb the interior of the gas block and do not add ports to the front or relieve the gas block forward of the ports. The relieving happens on the surface where the gas block interfaces the barrel and increases the shadow.

 

Debris....

Large ports allow larger debris and tend to foul the gas block quicker than more small ports will

Smaller ports (.070"ish) tend to clog easily when running Federal bulk loads

.078"-.080"ish seems to be the ideal size, from my experience, but the fact that I angle them a little more than factory could be a contributor.

 

 

ETA: When I say "running" it usually means "raising absolute hell and trying to break some shit", by most people's standards ;)

Edited by evlblkwpnz
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Your going to need to go up to probably 4ports at .093" minimum due to chopping 4" off. Even though youre going to perm attach a muzzle break, it will not act like an 19" barrel due to the ports and such. 4 ports at .078" is what gets most factory guns running reliably.Actually, I would look into adding a 5th port at .078" and go from there.
No 5th port. More ports let more fouling thru. Ideally you want 3 ports. 4 factory ports are "ok" but the problem with drilling them bigger is that the diamond shaped piece that is left in the middle can break off. So if you have 4, the absolute right way to increase them is, to not drill them, but mill them so that you are taking material off of the outside of the holes away from this center area.
Negative. Its not having more ports that's letting in more debris, its the size of the ports. So 5 ports at .078" is going to run cleaner than 4 ports at .093", and definitely cleaner than 3 ports at over .1".

 

Don't forget that the OP chopped his barrel, so the normal recommended port sizes listed for 19" guns won't apply and gas will need to be added either by increasing the 4 ports he has now, or add an additional port to compensate.

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Your going to need to go up to probably 4ports at .093" minimum due to chopping 4" off. Even though youre going to perm attach a muzzle break, it will not act like an 19" barrel due to the ports and such. 4 ports at .078" is what gets most factory guns running reliably.Actually, I would look into adding a 5th port at .078" and go from there.

No 5th port. More ports let more fouling thru. Ideally you want 3 ports. 4 factory ports are "ok" but the problem with drilling them bigger is that the diamond shaped piece that is left in the middle can break off. So if you have 4, the absolute right way to increase them is, to not drill them, but mill them so that you are taking material off of the outside of the holes away from this center area.

 

Negative. Its not having more ports that's letting in more debris, its the size of the ports. So 5 ports at .078" is going to run cleaner than 4 ports at .093", and definitely cleaner than 3 ports at over .1".

 

Don't forget that the OP chopped his barrel, so the normal recommended port sizes listed for 19" guns won't apply and gas will need to be added either by increasing the 4 ports he has now, or add an additional port to compensate.

We agree on the fact that "ports is bad," cause fouling but are necessary. The problem of creating a weak spot in the barrel favors fewer ports. Taking everything into account, I would rather minimize the number of them.

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Just an update, but tonight I removed the gas block, drilled out the 4 ports to .078" and added a 5th port at .078" as well, and reinstalled everything. All the ports are visible through the hole in the gas block. Actually have room for a 6th port on the other side. Surprisingly, the pin removal, gas block removal, and reinstallation wasn't near as bad as I was expecting. Taking it tomorrow to have the barrel shortened, and muzzle brake attached. I'll update when I get it back.

 

843C20DF-5044-4441-997D-4162F6DA420D-219

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  • 4 weeks later...

If you add a 5th port does it necessarily need to be the same as the original 4?

I ask because I'm planning on cutting 3.125" off my barrel and perm a muzzle brake for an OAL 18.125. my gun runs great now with 4 @ .093" but if it needs a little more with the 3" chop could a small 5th be added or would that work against itself?

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I just pulled my gas block and opened my ports today. I had 4 ports, but the one furthest forward was not drilled through into the bore. The whole thing came apart and went together very easily, but deburring the inside of the bore was a bit of a challenge. I opened them all up to .078" as recommended here, but after reading this thread it looks like I may need to pull the block again in the future since my plans are to include shortening the barrel and perming a long brake. Before this thread I was unaware that the holes needed to be enlarged more with a shorter barrel, so thanks for enlightening me guys! While it was apart I fully polished all friction surfaces in the gun, profiled and polished the bolt, etc. I haven't been to the range yet, but it cycles as smooth as glass now, and loading a full mag is no problem on a closed bolt, so I'm really happy with how it turned out. Still haven't converted yet, but will be collecting parts for that as my next phase. I wanted to perfect the cycling first before adding other factors like trigger group modification. I'm just pissed that I have to run a thumbhole stock here in the People's Republic of MA.wet_eyes.gif

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COBRA, I can't update yet. I've got the ports done and the barrel shortened and all, but Pauly's got most of my parts that make it go BANG.

You should have sent it to Cobra.

You'll probably be waiting for 6+ months to shoot your gun now!

Edited by dubya
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I will be doing the same thing but, I also have my parts sent in to pauly to get work done.

My barrel is stock at 19 inches.

Jte reliability kit, tromix recoil spring. 6 position gas adjustment, and css gas puc.

 

Say after I get my parts back from Pauly and i still have a light ammo cycling issue. That I should go with 4 ports at .078 yes?

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