We solved the problem

[i8asquirrel]

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!!! Thanks for all the help on getting the kinks worked out!

[mak91]

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.

[BWE Firearms]

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.

[i8asquirrel]

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

[SgtCottle]

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.

[i8asquirrel]

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.