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Posted: 4/23/2017 8:07:12 AM EDT
[#1]
Carbide tipped will do it.
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Posted: 4/23/2017 8:23:57 AM EDT
[#2]
Are you 100% sure the port size is the problem ?
I've done a few on a mill the way I set it up would work on a drill press. Find a drill bit that fits tight in the existing port backwards. Chuck that in the drill press chuck and clamp the barrel so the bit will slide in and out freely . Looking at my numbered and lettered drill bits I was able to find a bit a few thousands larger . Put a wood dowel down the bore to protect the other side and set the drill press stop for depth and start drilling slowly . Watch to see if the bit cuts 360 degrees without pushing side ways first. |
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Posted: 4/23/2017 8:35:31 AM EDT
[#3]
This isn't a issue. I'm looking to do a 300 blackout 7.5" or 8" build. I'm not planning on suppressing it at all. It would be nice to run subs if I wanted to. Most gas ports need to be at .100 in order for subs and supers to work. Most 300 barrels are only at .080 or so.
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Posted: 4/23/2017 10:26:55 AM EDT
[#4]
Quote HistoryQuoted:
Carbide tipped will do it. |
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Posted: 4/23/2017 11:13:24 AM EDT
[#5]
As long as the port alignment is squared up, shouldn't need to do any of that. Have a 7.5in bbl I run subs and supers with w/o a can. Troy PDW stock.
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Posted: 4/23/2017 11:25:04 AM EDT
[#6]
Quote HistoryQuoted:
As long as the port alignment is squared up, shouldn't need to do any of that. Have a 7.5in bbl I run subs and supers with w/o a can. Troy PDW stock. |
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Posted: 4/23/2017 12:13:10 PM EDT
[#7]
My barrel has a .0935 sized hole and wouldn't lock bolt open on last round firing 220gr subsonics unsuppressed with a standard carbine buffer and spring. I switched to a Tubb flatwire lightweight version spring and no problems anymore. I was also able to switch to an H2 buffer and subsonic still cycle fine.
Standard milspec spring is 7lbs in battery and 16lbs compressed Tubb lightweight is 7lbs in battery and 14lbs compressed The lighter compressed weight allows it to cycle correctly and achieve last round bolt hold open on lighter pressure rounds unsuppressed. A suppressor will add backpressure and port size is usually not an issue |
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Posted: 4/23/2017 12:20:40 PM EDT
[#8]
I would not make port changes on any barrel until such time as I know it is needed, put it together, and shoot it with the various ammo you expect to be using before you modify it.
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Posted: 4/23/2017 12:36:45 PM EDT
[#9]
Quoted:
I'm having trouble searching and finding information. Has anyone opened up a gas port by using a hand drill? If so what type of drill bit is recommended for a 4150 barrel? I may have access to a drill press but still need to know what type of bit to use. It is pretty easy to just clamp it in a vise and drill by hand I may try that. |
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Posted: 4/23/2017 1:09:40 PM EDT
[#10]
Quote HistoryQuoted:
My barrel has a .0935 sized hole and wouldn't lock bolt open on last round firing 220gr subsonics unsuppressed with a standard carbine buffer and spring. I switched to a Tubb flatwire lightweight version spring and no problems anymore. I was also able to switch to an H2 buffer and subsonic still cycle fine. Standard milspec spring is 7lbs in battery and 16lbs compressed Tubb lightweight is 7lbs in battery and 14lbs compressed The lighter compressed weight allows it to cycle correctly and achieve last round bolt hold open on lighter pressure rounds unsuppressed. A suppressor will add backpressure and port size is usually not an issue |
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Posted: 4/23/2017 11:10:40 PM EDT
[#11]
My experience is an HSS bit drills them fine. You want to follow this in very small steps like one number to the next which is still a several thousand jump. A hand drill will align itself just fine; small bits will easy self align if you're close.
Shove a dowel in the bore to give you a stop to protect the rifling. It a very quick thing and easy if you just spend a minute or two getting things together. |
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Posted: 4/25/2017 9:07:33 AM EDT
[#12]
If you rule out other issues and conclude the port really needs to be opened, the key is a new sharp bit. HSS is fine.
It needs to be sharp. A drop or two of cutting oil will help prevent chatter when making contact and will keep the bit cool. Center in the hole with a bit the same size as the hole. Then move up. Go slow. Set rpm fast, about 3,000. Set stop for depth and insert a dowel to protect the bore. If making major change use progressively larger bits. |
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Posted: 4/25/2017 9:21:32 AM EDT
[#13]
A standard HSS bit works fine. They open up VERY easily. You're only taking a few thou off, so you'll be surprised at just how soft and easy it feels when running the new bit through.
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