What did I do wrong?

[watchingtrace]

http://www.amazon.com/gp/aw/d/B000P...pace+gauge&dpPl=1&dpID=31bsWRmt3rL&ref=plSrch

you can not build quality anything ,including ammunition, WITHOUT measuring!!!!!!!!!

 

[watchingtrace]

measure fired case, subtract .002 , thats your target spec. easy peasy.

also, inconsistent lube application, multiple fireings without annealing, and varied time that the brass sits fully seated into the die can all contribute to inconsistent headspace measurement. this is why people have some that will chamber and some that dont in their same "lot" of brass

once fired factory brass is what you should be getting your baseline measurement from. i was going to link you to a youtube vid but unfortunately the (insert title here) on y tube overcomplicate it.

 

[ltfirhunter]

I'm taking that the rounds want chamber are the ones fired from a different rifle.
If this is the correct, then your are going to have to bump the shoulders back,(head space), so turn your dies down to the shell holder, with cam over and thy hopefully will chamber then.
And get the tool that Pro, recommended, it will help you adjust your dies afterwards

 

[3clicks_Off]

sounds like the shoulder is to big from fire forming in the loose chamber of your buddies rifle if OAL of case is correct.

 

[Twitch2120]

look at the cases that wont chamber and the ones that will. see if the shoulder angle is different or if there is a sharp edge to the body/shoulder junction. my friends SCAR had a burr during chamber reaming and his cases are useless as that little lip will not resize. the gun had to be sent back. Also examine the neck/shoulder junction as some chambers are ramped there and others arent. if his is ramped and yours isnt it can cause issues. also, take your gun to a smith and have him look at your chamber, you may have gotten a burr and certain brass sticks.

 

[bearpugh]

also check for any slight bulges. could be too much lube.

 

[3clicks_Off]

also check for any slight bulges. could be too much lube.

 

[Flashover16]

I can't see it being anything except incorrectly resized brass.
IF factory and some used cases work then the problem child is the resizing operation.

 

[Jackie Graham]

It's a redding die all I could find during the panic years.

Double check to make sure the die is a Full Length resizing die and not a Neck Sizing die.

 

[watchingtrace]

the hs gauges will tell the answer. then you can watch your process and the results it yields.

anything else is best guest speculation circle.

JG also had a good point on making sure they are FL dies and not NK sizing dies.small base dies are un necessary.