...so dont start tearing anything apart till you have checked the headspace, and also length of your brass can cause this, as well as foreign matter in the chamber or throat. First thing I would do is take a bore brush and clean the throat with a good solvent, 'Outers,Breakfree,etc'...then repeat this process with an oversize brush (.45 or something larger than the case) and thouroughly clean the chamber.
Next, check your ammo. Remove the barrel and insert a round into it. It should drop easily into the chamber so that it is perfectly flush without forcing it in. If it dosent, either the shoulder is not headspaced properly, or the brass is too long, or the bullet is seated to long. All of these are easily fixed without tearing up your gun.
If it dosent go in easily, try some different ammo. Use a name brand like Remington or such, I have had cheap .223 ammo that would not chamber, I ran them through my die and they worked fine.
If you want to check your brass, run a spent shell through your press, but do not load it, check the length of the brass and if neccesary trim it, then try it in the chamber. If it goes in flush, it should work in your gun, you can even put a primer in and try it.
Remember, it is not enough to neck-size brass with a Contender, you need to full length re-size brass to bump the shoulder back. To do this you need to set your die in your press so that the shell holder comes all the way up to the bottom of the die and 'CAMS OVER' (you should feel a slight pressure at the top of the stroke, your instructions with your dies shoud tell you how to do this)
Once you have checked these things, and it still dosent work....THEN you might have to worry about your locking lug height, and that can sometimes be adjusted on your receiver. Someone else mentioned that information on this process is available on Mike Bellm's website. Dont start grinding on your locking lug.
