We solved the problem
 

I was having trouble with feeding on the 300 whisper upper we built for my AR15. it shot great but didnt feed. well i just came in from the range and problems are solved!! We wound up with a 16" barrel,carbine length gas tube, .116" gas port, rifle length buffer spring with carbine buffer inside a rifle stock, functions great!!!:twoguns: Thanks for all the help on getting the kinks worked out!

I think you could have issues running a carbine buffer inside a full length rifle buffer tube. I believe this combination will allow the bolt carrier to travel to far back allowing the gas key to hit the upper part of the lower receiver. You might want to post your setup on the build it yourself forum on www.ar15.com and see what they say. Better safe than sorry.

You could make or have made a Delron spacer that will slide in the buffer tube then the spring and buffer to make up for the shorter buffer. Put a head on the spacer so the spring will hold it to the back of the tube.

Thats a good idea..... I will try it

Yes definately need a spacer on the buffer or your gonna rip the gas key off. If your trying to keep your spring tension down - you can make a Delron buffer assembly cap that extends the additional length needed. On normal carbine buffer assemblies the cap has a roll pin that keeps it secured to the buffer assembly. You can remove that cap and then add a lengthened one that will slide inside (this is the key) the spring with the buffer assembly. That way you do not increase your spring tension and possibly stop the rifle from cycling reliably.

ok I thought about it and instead of making an delron spring guide I weighed the carbine buffer (1305gr) and then disassembled a rifle buffer and removed some of the counter weights to mach the weight of the carbine buffer. I have no acces to a lathe and figured a rifle buffer was cheaper than machine time.

The weights that you are removing are in there to keep the bolt from bouncing back after it slams shut. You might want to make sure the bolt is completely closed before you fire each round with these weights removed from the buffer.

As mak91 said if you take the weights out make sure the bolt is closed before firing the next round. Bolt bounce can be a real pain and you really don't want a round to fire out of battery.

Bolt bounce is generally more of a problem in a full auto gun.I have never seen it be a problem on semi auto. What happens is the bolt actually moves back slightly on full auto (bounces) as the sear is being tripped causing a misfire. The same action happens on semi but its not a problem as the bolt has time to be reseated by the recoil spring before the hammer falls again. The AR is designed such that it will not fire if the bolt is not rotated fully into battery as the firing pin protrusion is insufficient to fire the round. This is a suilt in safety feature so that full auto weapons will not fire out of battery if bolt bounce occurs. I have fixed several select fire weapons that were being run with light buffers and misfiring simply by replacing the buffer with an H2 buffer to prevent bolt bounce.

Yep ... one of the beautiful features of the AR. It is impossible for the firing pin to strike the primer unless the bolt is completely closed. The rotation of the bolt allows the carrier to move forward and close the "safety" gab so that the firing pin can protrude past the bolt head. Unless the cam nut is sheered off there should never be any problems ... if the forementioned occurs then your gonna know immediately.

Sarg