I put together an AR upper with a barrel chambered for 6mm x 223. When I loaded up these rounds I used the maximum powder charge listed in my reloading manual. It ejects the fired case okay but the bolt will not go back far enough to feed a new round. I am thinking of opening up the gas port or taking a few coils off of the action spring. Any info would be welcome. Thanks, Jim

Areas to check:

First, insert an empty mag, pull t-handle back.  Does the bolt easily lock open?  If so, you do not need to cut the spring due to binding.  If it does not lock, check for spring coil bind , or too long a buffer screw thru the butstock into the buffer tube.

If this is not the cause of the short stroke, try a wolf "light" buffer spring.  It is a little lighter than standard, and may eliminate your problem without drilling.

If that doesn't work, I'll let someone more familiar with gas port adjustments take it from here.

ar-wrench,

Thanks for the reply, the lighter spring is a good idea. The lower I am using had an M4 upper on it and worked fine. I am wondering if the larger diameter bullet needs a little more gas flow to operate the bolt.