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Posted: 8/20/2024 5:25:12 PM EST
Is there a book on gas port size vs gas system and barrel length?
For example, what would be a soft shooting gas port for a mid-length gas system 13.7" barrel that has an adjustable gas block and would be shot suppressed and non suppressed? Thanks in advance! |
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MN, USA
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Posted: 8/20/2024 5:40:54 PM EST
[Last Edit: s4s4u]
[#1]
There is no book, lots of opinions but no book. You have an AGB so it really doesn't matter, as long as the port is large enough. I had to open the port on a 14.5" with mid gas because it was too small. You will have to make changes going from can to no can if you want peak performance, there is no magic. Same as with optics, if suppressed also means sub's.
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Posted: 8/20/2024 7:24:45 PM EST
[#2]
Quote HistoryOriginally Posted By s4s4u: There is no book, lots of opinions but no book. You have an AGB so it really doesn't matter, as long as the port is large enough. I had to open the port on a 14.5" with mid gas because it was too small. You will have to make changes going from can to no can if you want peak performance, there is no magic. Same as with optics, if suppressed also means sub's. Should I look at other manufacturers as a starting point? |
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Posted: 8/20/2024 8:07:33 PM EST
[#3]
If you already have an adjustable gas block, port size isn't really relevant. Being able to tune the amount of gas is the whole point of the AGB. You can adjust it to run your weakest ammo reliably unsuppressed and still use a van with no adjustment or you can tune for both with and without the can and adjust accordingly. Up to you
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Posted: 8/20/2024 9:13:56 PM EST
[#4]
Port size in the barrel when using an AGB is most certainly relevant. An AGB cannot increase gas to the system, it can only restrict it. If ther gas port in your barrel is too small and your rifle is under gassed, no amount of adjusting your AGB is going to increase gas flow. As one poster sort of mentioned above, you must drill out the gas port in the barrel to be slightly over sized and over gassed and then use the AGB to turn down the gas to fine tune your system. If your rifle is not getting enough gas, an adjustable gas block does nothing to solve the issue.
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Posted: 8/20/2024 9:20:16 PM EST
[#5]
Quote HistoryOriginally Posted By Big-Bore: Port size in the barrel when using an AGB is most certainly relevant. An AGB cannot increase gas to the system, it can only restrict it. If ther gas port in your barrel is too small and your rifle is under gassed, no amount of adjusting your AGB is going to increase gas flow. As one poster sort of mentioned above, you must drill out the gas port in the barrel to be slightly over sized and over gassed and then use the AGB to turn down the gas to fine tune your system. If your rifle is not getting enough gas, an adjustable gas block does nothing to solve the issue. Absolutely true, but too small of a gas port isn't nearly as common as overly large. I read it as he wanted to decrease it. I may have interpreted it wrong though. |
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MN, USA
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Posted: 8/20/2024 9:48:06 PM EST
[#6]
Quote HistoryOriginally Posted By Stowe: Absolutely true, but too small of a gas port isn't nearly as common as overly large. I read it as he wanted to decrease it. I may have interpreted it wrong though. You're good. We all knew what you meant 
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Posted: 8/20/2024 9:56:45 PM EST
[#7]
Yep, my problem is that I'm not getting the blot to lock on the last round on a 13.7 middy that was cut down from a 16. I know the port is too small so the question is what would it have been on a 13.7 middy from the factory.
Looks like .077 is about right from what I was able to dig up. I might try that. |
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Posted: 8/21/2024 3:25:15 AM EST
[#8]
Quote HistoryOriginally Posted By Voland: Yep, my problem is that I'm not getting the blot to lock on the last round on a 13.7 middy that was cut down from a 16. I know the port is too small so the question is what would it have been on a 13.7 middy from the factory. Looks like .077 is about right from what I was able to dig up. I might try that. |
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MN, USA
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Posted: 8/21/2024 9:03:02 AM EST
[#9]
Quote HistoryOriginally Posted By Voland: Yep, my problem is that I'm not getting the blot to lock on the last round on a 13.7 middy that was cut down from a 16. I know the port is too small so the question is what would it have been on a 13.7 middy from the factory. Looks like .077 is about right from what I was able to dig up. I might try that. Not surprised with a mid 13.7 barrel. Since you have an AGB you can undo if you do too much. Before you open the hole, try with an empty buffer. Pop the pin and dump the weights out. If it runs on empty, you can get aluminum weights to mix with the steel weights for tuning. If it still won't lock back, open the hole a few thou's at a time and test as you go. |
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MT, USA
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Posted: 8/21/2024 9:09:32 AM EST
[#10]
.078 seems to be a popular size. What ammo are you not locking back with?
https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/edit?gid=766121382#gid=766121382 |
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