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9/9/2016 12:34:34 PM EDT
First introduction,

This is my first post, Although I have been reading post for years.
Consider myself gun savvy. Ran Ar/M4 in the Corps among other weapons platforms.
And have been shooting for many years.

My current build is 100% reliable. Quality parts
BCM upper
Surefire brake
Fail zero bolt
Armalite lpk
Tac innovations lower.
POF trigger.


My issue is that it isn't running as smooth as other builds.
There seems to be a lot of movement,bounce during recoil.
Having difficulty with placing rapid shot to shot on target.

My original solution was a brake, then a heavy buffer. Then,
I pulled other complete lowers and placed with this upper
And it was butter. Don't want to scrap the whole lower.

Now I have ordered some buffer springs from tactical springs.
To see if springs are an issue.
I may even change out the buffer tube. (Maybe slighty out of spec)

I don't think the gun is over gassed, as ejection patterns are at about 4:30.

Any one have suggestions?
Thoughts?
9/9/2016 6:02:47 PM EDT
[#1]
Could be your buffer tube being a little on the short side.
9/9/2016 7:38:19 PM EDT
[#2]
Hard to tell without details on what is different between the lower with the issue and the one that works fine.

- inspect for a non compliant part.
Inside of buffer tube rough? Visually compare parts between the 2 lowers to see if you can determine any differences. A heavier buffer might make impulse worse.

- is one easier/smoother to manually cycle or only notice difference when firing?  

- You can try switch out parts between the 2 lowers one at a time until the problem gets transferred.  
Start with the buffer spring, then buffer, then tube, etc. Otherwise you might end up buying a lot of parts you don't need.



9/9/2016 7:58:20 PM EDT
[#3]
I have been doing the part by part bit.

Buffer had some improvement
As did the brake.

I'm starting to think its the buffer tube. Maybe not in spec.
Got some parts in mail today.... So got another excuse to head to the desert.


9/10/2016 12:44:18 AM EDT
[#4]
You can check for machine marks on the inside of the buffer.  

Have you tried some grease on the spring and buffer? I changed to a chrome silicon spring and with the grease it quieted down the action a lot.

If you changing the upper with a brake, then might look into an adjustable gas block to reduce felt impulse.    

9/10/2016 10:05:45 AM EDT
[#5]
Atom:  I recommend you replace the buffer tube with a name brand part like Vltor, then install a milspec 3 oz carbine buffer and install a standard carbine spring by a quality brand like JP Rifles.  Apply a thin coat of moly grease to the spring.  With those in place, install an adjustable gas set up, either gas block or gas key.  Personally, I like the adjustable gas keys from Rubber City Armory - easy to install, easy to adjust and inexpensive.  Adjustable gas enables you to tone down the reciprocating action to that necessary to reliably lock back the BCG on an empty mag, with no excess energy. good luck - CW
9/10/2016 1:14:57 PM EDT
[#6]
Thanks for the recs. I'll keep swapping out the parts till I find a solution.

May do the Vltor A5 buffer system.

... And even try an adjustable gas block.
9/10/2016 3:28:30 PM EDT
[#7]
I had a Vltor A5 set up on one of my rifles for a while.  I couldn't tell the difference in recoil, sound, etc., but then I don't have a lot to compare it with.  My other carbine length buffer/spring set-ups have Taccom ultralight buffers and springs to go with adjustable gas keys.  A carbine needs to be light, IMO.  

The A5 extension is a peculiar length, uses a rifle length spring and a special buffer available in several weights.  It is not compatible with milspec-sized carbine buffers, however, Vltor makes an excellent, normal-sized 5-position receiver extension.  Light, strong and very well made. - CW
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