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Scott5182
09-27-2011, 6:31 PM
Ok, My 10" pistol upper works great. I built a 7" with pistol gas tube and the shell doesnt extract all the way and the new round feeds. They come together as a V into the chamber and the bolt dents them into a jam sandwich....I have a standard carbine buffer and spring. Can any expert tell me if I need a heavier buffer, buffer spring or extractor spring to solve the problem?
I am also using a Levang compensator.
Anyone???

GMG
09-27-2011, 6:38 PM
Scott,
I had that problem before with a rifle length, this kit took care of it. If you have more than one AR, they also offer a kit for three rifles.

http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm%20extractor%20spring%20upgrade.htm

Scott5182
09-27-2011, 6:44 PM
Right on! thanks. I will try that. I suspected that there were better exratraction springs available. Seems that it just isnt quite quick enough with the 7"

FeuerFrei
09-27-2011, 10:03 PM
You should try to slow up the trouble shooting first.
Swap uppers with your 10" pistol (asuming it is also 223/556) and test again.
If no go then swap just the complete bcg and test.
If you are having a failure to extract then you can check the extractor for irregularities. (compare to 10" pistol bolt).

Adding a heavier weight buffer usually solves the FTE double feed. BCG needs to slow down and allow time to fully remove fired case. Very common on short barrel AR DI uppers.

Scott5182
09-27-2011, 10:29 PM
I tried two different BCG and got the same results...I will try the spring tune up kit and maybe a heavier buffer....$4 then $40..maybe a 4oz? or more??

FeuerFrei
09-27-2011, 10:43 PM
If you got the same results with the bcg swap then it's the buffer. H or H2 should do the trick.
BTW
Look at the first post here and keep for future reference. http://texaspredatorposse.ipbhost.com/index.php?showtopic=10001
Good luck with it.

krazy
09-27-2011, 11:03 PM
When I built my ar pistol it was 7.5 inch barrel, I had to drill out the gas port. I found the info on another forum, it was only slightly bigger and I never had any fte issues.

Found it:

http://www.ar15.com/archive/topic.html?b=3&f=122&t=505773

FeuerFrei
09-28-2011, 7:14 AM
^^ If the buffer swap doesn't work then I agree.
Open up the port to the next size. My first DI 7.5" was origionally .063 and went to a .077 to fix it.
It's just a good idea to try the easy stuff first.

krazy
09-28-2011, 7:52 AM
^^ If the buffer swap doesn't work then I agree.
Open up the port to the next size. My first DI 7.5" was origionally .063 and went to a .077 to fix it.
It's just a good idea to try the easy stuff first.

Very true. Another thing you can look into is a full auto m16 bcg. It is lighter than a regular semi-auto bcg and legal to have. You can find them cheaper as well. Best of luck!

shadow65
09-28-2011, 8:25 AM
First, load one round in the mag. Fire it and see if the bolt locks back on the empty mag. Do it a few times. If the bolt locks back every time, you know it's not a under gas problem.
If it does not lock back, try a lighter buffer.
I always use the extractor spring upgrade.

My set up is a 7.5" Ranier barrel
H2 buffer/carbine spring
M16 BCG
Extractor spring/black insert upgrade
Kies Linear Comp
It will run Wolf.

Also for break in, make sure the chamber is scrubbed and the BCG is well lubed.
I hand cycle my new builds 100-200 times before I ever take them to the range. It helps mate the BCG to the chamber lugs.
Dave N

AR-15 Rep
09-28-2011, 8:46 AM
First... the M-16 bolt carrier is heavier than the AR-15 bolt carrier. Second, when boring out the gas port, remember the pressure generated is: .223 around 55k psi, 5.56mm 62k psi chamber pressures. You then have your gas tube which may take ? psi... with the compensator, gas pressure may be on the high side. This would cause an extractor failure and an upgraded extractor spring, heavier bolt carrier, and or a heavier buffer should slow it down a bit to help. You may want to really look at the brass to see if it is short stroking ( larger gas port needed ) or FTE due to over pressure and extractor failure ( extractor upgrade, heavier buffer, etc ).

krazy
09-28-2011, 9:01 AM
First... the M-16 bolt carrier is heavier than the AR-15 bolt carrier. Second, when boring out the gas port, remember the pressure generated is: .223 around 55k psi, 5.56mm 62k psi chamber pressures. You then have your gas tube which may take ? psi... with the compensator, gas pressure may be on the high side. This would cause an extractor failure and an upgraded extractor spring, heavier bolt carrier, and or a heavier buffer should slow it down a bit to help. You may want to really look at the brass to see if it is short stroking ( larger gas port needed ) or FTE due to over pressure and extractor failure ( extractor upgrade, heavier buffer, etc ).

Hmm always thought the M16 bcg was lighter due to the less material and cuts. My mistake.

triggs75
09-28-2011, 9:48 AM
Hmm always thought the M16 bcg was lighter due to the less material and cuts. My mistake.

http://i6.photobucket.com/albums/y209/AFreeMan/BoltCarriersM16vsAR15.jpg

krazy
09-28-2011, 10:24 AM
Yea I went and looked it up after I made the last post. I think I got it mixed up. When I was building my pistol, I figured if it's reliable enough for a military issued m16, then its reliable enough for me. Never had a problem with my kitty kat barrel and set up. Zero FTE and zero FTF, wolf ammo was okay, as well as 556.

http://images52.fotki.com/v737/photos/4/83114/7841240/IMG_4011-vi.jpg

Agent Tikki
09-28-2011, 10:31 AM
RRA 9mm buffer $25 a tad heavier than the H3 buffer, check out Riflegear. Should slow things down nicely.

triggs75
09-28-2011, 11:15 AM
http://images52.fotki.com/v737/photos/4/83114/7841240/IMG_4011-vi.jpg

That is the rail/muzzle set up I am looking at when I complete/start my pistol build. Looks great!

Chad