AR15 gaas port specs

S

SSLIGH

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Does anyone have a list of the ar15 gas port size specs for the various barrel lengths and any differences for the differnt calibers if there is any? port locations for various lengths? I am also looking for blueprints for the ar15 barrels which would include some of this major and minor specs for rebarrekling ar's.
Thanks
 
Al,

I am perfectly capable of apoligizing for myself - and there isn't a need for doing so for my first post.

The book I linked to in my earlier post has a full set of specs for an AR-15 barrel. That and the other info on building an AR makes it an invaluable resource for anyone contemplating doing all their own work. It may well be written by someone you don't know, Al. Then again, there's a LOT you don't know, so here's a hint: He's one of the top AR-15 armorers in the nation.
 
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the problem is that std 20" a2 specs exisit. i have not seen specs on the a3/a4 16" guns.

and if you build longer like 26" plus most move the port forward 2"....

i do not know if the answer is published.

your alternative is to go ask on ar15.com...but i had no luck thier when i asked true technical bbl chambering questions...maybe on the mfg forums there.


not too many benchrest guns built on ar's.....(i have three)

good luck, let us know what you find.

mike in co
 
Al,

I am perfectly capable of apoligizing for myself - and there isn't a need for doing so for my first post.

The book I linked to in my earlier post has a full set of specs for an AR-15 barrel. That and the other info on building an AR makes it an invaluable resource for anyone contemplating doing all their own work. It may well be written by someone you don't know, Al. Then again, there's a LOT you don't know, so here's a hint: He's one of the top AR-15 armorers in the nation.

I've got no problem with the book or the author.

My problem lies with ........"Posted yesterday - might want to try the "Search" feature next time. ".........

What does this mean?

al
 
It means the same answer was posted yesterday.

So what. Obviously SSLIGH wasn't here yesterday.

Mr SSLIGH comes onto a new board about which he probably knows little and the first answer to his first post is "Posted yesterday - might want to try the "Search" feature next time. "

Now I don't know about you Asa but when I venture into a strange room and ask a question I HOPE that the folks are friendly and helpful. And welcoming.

SSLIGH, I again apologize for Mr Yam. I hope that your stay here is fun and informative. And YES, the book that Asa suggests is a good source of information. And YES, Asa often offers good info....... perhaps I overreacted.

al
 
Does anyone have a list of the ar15 gas port size specs for the various barrel lengths and any differences for the differnt calibers if there is any? port locations for various lengths? I am also looking for blueprints for the ar15 barrels which would include some of this major and minor specs for rebarrekling ar's.
Thanks

Considering that AR-15s are commercially chambered for over two dozen different cartridge, five standard or semi-standard gas port positions, and five semi-standard barrel diameters at the gas port location you're going
have a very long list. That's not considering that often the gas port size is taylored for different loads and bullets used in a particular cartidge. A good example of that is the 300 Whisper where two gas port locations and diameters are offered by the same manufacturere specifically for subsoinc and supersonic loads. Some manufactueres offer adjustable gas block for such rifles.

There is some information along the lines you want at http://www.ar15barrels.com and htttp://www.ar15.com but I doubt you ever find the list you're seeking. You'll only find an occasional mention of the gas port size used on a specific barrel. That's a variable many manufacturers use to tune the rifles they build, and gnerally not something to be specified in a procurement contract even for "standard" military rifles.

You have several choices if you're building a rifle for a special load or wildcat cartridge. You can get an adjustable gas block or gas tube, or use a "numbered drill set and tune your barrel to the load your using. If you then bulid a second rifle for the same cartidge and load then you know what to use. If you can find a rifle someone already has which matches what you want they they may let you measure the port diameter. Beware, the barrel cartidge and load need to be identical.

There are discussions on tuning barrels to loads on sites which deal with subsoinic cartridges. It's mostly a matter of guessing the gas port location from studying pressure curves as calculated by programs like Quickload then adjusting the port sizes and some asking others what they've found works with similar cartridges. It's not an exact science.

I "built" a pair of matched left and right hand 300-221 pistols where I specified the barrel length and asked the barrel manufactuer only put an index mark at my specified gas port location. I worked up the port size with a number drill set using my handloads until I was happy with the cycling in the first barrel, then drilled the second barrel the same. That worked well taking only eight test shots. The barrels are identical even though the upper receivers are not.
300-221_L-R.jpg
 
I dont have the info you are looking for but if you call John Holliger at White Oak Armament 309-376-2288 I bet he can help, has always been willing to answer questions for me.

Larry
 
You can start at .078 and work your way up to .0895 for port size. Standard port size is around .092 for the 20" bbls, but I usually start smaller and test fire to see how the function is. Or, you could just drill to the larger size and utilize the JP adjustable gas block and not worry too much about the port diameter.
 
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Thanks for the help guys. I figured it would be tough to get this information. I appreciate your help.
SSLIGH
 
Shilen drills .093 for port size on their drop in barrels.
 
Gas port sizes

Shilen drills .093 for port size on their drop in barrels.

Is that for the 223 Rem barrel? I'd be surprised if the same gas port size is right for the 204 Ruger and 17 Remington AR-15 barrels which Shilen also sells. I didn't measure the port diameter when I put my 17 Rem together. I just assumed Shilen determined the right size which is the barrel maker's job. It can't be a "trade secret" since anyone can measure it if they have a barrel in their hands, but thers is no reason to give away hard work by publishing it.
 
Just measured a shilen drop in gas port on a drop in 204 and it is also .093. It seems like alot is talked of different port sizes due to pressure differences in various calibers.However those same pressure differences can be exprerienced in any caliber with changing the powder and or bullet.Main concern its to get enough gas to reliably cycle the action.A little extra gas will still make it cylce with almost any load,If you want to have just enough to make it cylce and no more , then use an adjustable gas block and soften it up.
 
I can tell you from experience the 17 Remington does NOT have to be .092.

Start small on that one at .075 and work up to what works. On 18" bbls with mid-length tubes I had perfect function at .078 I believe. The one 204 I built I don't remember what I ended up at.
 
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