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voonman

Turning down the Gas on an AR gains more Velocity behind the bullet?

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Hi Eveyone

Ok so i figured out that my 8" SBR in 338fed was over gassed..and i turned the gas selector 3/4 way to the close position and now my AR10 is shooting much smoother and kicking the brass at a 4 oclock direction..I did another chronograph test after i did this and i am gaining about 100fps faster at 2310fps out of my barrel using the same 185gr American Eagle. The weather today was cooler than before ..temps were around 87F. Any thoughts?The updated video is below

 

https://www.youtube.com/watch?v=VdF8LLjB4ck

 

post-16872-0-86651800-1444013078_thumb.jpg

 

Edited by voonman
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Keep reducing the gas until the gun stops.  Then go back a little bit.  If nothing else it might increase service life.  My old Belgium FN LAR ran on setting #7 (or was it setting number 3 ?  Forgot.  Too long ago)  and plopped out the brass only about 2 feet right by the rifle.  It also seemed to somewhat reduce recoil but I can not remember clearly.  35 years ago.  Yep ... you knew this was coming ... have you talked to Elite Iron yet about a custom .338 short barrel can?  Mission Impossible!  They might want to re thread your barrel.  We love our Elite Irons.  HB :)

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Keep reducing the gas until the gun stops.  Then go back a little bit.  If nothing else it might increase service life.  My old Belgium FN LAR ran on setting #7 (or was it setting number 3 ?  Forgot.  Too long ago)  and plopped out the brass only about 2 feet right by the rifle.  It also seemed to somewhat reduce recoil but I can not remember clearly.  35 years ago.  Yep ... you knew this was coming ... have you talked to Elite Iron yet about a custom .338 short barrel can?  Mission Impossible!  They might want to re thread your barrel.  We love our Elite Irons.  HB smile.png

Yes i actually turned the gas all the way off and started from there until i found the sweet spot.. But i was very curious on how this could effect the velocity ..and that is what prompted me to do this test..I havent called Elite Iron yet but i am about to obtain some 230gr subsonic loads and i will be using my friends sound suppressor to see how quiet she will be ..i will post a video of this as soon as i get everything together

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You ought to be able to do a lot better than 230 grain subs. That"s only 300BO energy. With the fatter bullet, you might be able to get something near 300 grains at 1120 FPS or so!

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You ought to be able to do a lot better than 230 grain subs. That"s only 300BO energy. With the fatter bullet, you might be able to get something near 300 grains at 1120 FPS or so!

you are probably right..i am just testing what was offered..i will suggest to him and see if he has any 300gr that he can load for me..

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So I have a few questions please. 1st sweat SBR, this is the first time I heard of 338 "federal", when I saw 338 I thought DAMMMMM he has a Short Barrel Canon!!!!big_smile.gif  ....

 

I had a question a while back about gas blocks and their purpose, the site I posted on stated that in a AR application you should only install adjustable gas blocks on a CAR legnth gas system, the gas block is supposed to control the amount of kick that a CAR style weapon has.       Is this correct?

 

Velocities on a 338 Fed, according to Hogdon, is in between 2350 - 2600 for standard loads and 2500 - 2700 max, then I would say the answer is, when you opened the gas block it reduced the pressures which in turn reduced the velocity, this would also leave behind unburned powder in the barrel Did the kick change? It looked like you had it benched.

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So I have a few questions please. 1st sweat SBR, this is the first time I heard of 338 "federal", when I saw 338 I thought DAMMMMM he has a Short Barrel Canon!!!!big_smile.gif  ....

 

I had a question a while back about gas blocks and their purpose, the site I posted on stated that in a AR application you should only install adjustable gas blocks on a CAR legnth gas system, the gas block is supposed to control the amount of kick that a CAR style weapon has.       Is this correct?

 

Velocities on a 338 Fed, according to Hogdon, is in between 2350 - 2600 for standard loads and 2500 - 2700 max, then I would say the answer is, when you opened the gas block it reduced the pressures which in turn reduced the velocity, this would also leave behind unburned powder in the barrel Did the kick change? It looked like you had it benched.

 

thanx for commenting ..yes the kick did change and i did not have it benched..it feels lighter after closing the gas block off at 3/4... Federal is loading there factory 180gr Noslers at 2830fps http://www.ableammo.com/catalog/ammo_charts/Federal_Ammunition_Ballistic_Chart.pdf��� and the loading chart for there 160gr Barnes TSX flying at 2920fps http://reloadersnest.com/frontpage.asp?CaliberID=552 ..The factory ammo that i used in the test above was there American eagle 185gr with a muzzle velocity of 2750fps and 3105 ft lbs of energy out of a 20" barrel as listed on the box..I am averaging about 2172 ft lbs of energy from the muzzle and an average loss of 480fps  out of my little 8" barrel

Edited by voonman

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