i as well own a TC encore in the 300 mag.i bought the barrel used and the previous owner gave me two boxes of brass ,that i mite reload .inspection of the brass showed a lot of stretched, i then checked the head space and found it to be .005 to deep .sent it in to tc ,they sent a new one ,it was .005 to deep. then with a stern letter insisting that they send me a good one i finely got a good one.i all so know of a 7 mag that has the same problem. if your chamber is to deep ,your firring pin could be having a hard time reaching the primer and if the primer is a hard one it will be that much harder to set it off .
don't use the hammer extensionthe hammer is made to lite and will brake off.when that happens you go home talking to your self. ya been there done that.

I had the same problem also,this extension work's the best...

http://www.strattoncustom.com/pages-main/category-15/hammer-extensions.html?zenid=ca2cee4d32ff549d0533e6d27c0c 5ce1

Cat, how do you measure headspace on an encore. Just curious. The world of breakopens are all new to me. If you did it using a stony point head and shoulders gauge, you can get lies, I found out. And if you only neck size your brass, you can end up in trouble.

Yep, that’s the one I have. I had purchased it from Virgin Valley at the time...

I would check the headspace. Mike Bellm has an article about this here.....

http://www.bellmtcs.com/FAQ/Experiment.htm

He also sells a headspace indicator here.....

http://www.bellmtcs.com/store/index.php?cid=38

whatever you do don't blow the whole gun apart, it's fatal

I had a similar problem with my slug barrel. I also have the hammer extension on my Encore and when I called T/C, they said that the hammer extension will void your warranty. This is something to think about. If they see the screw marks, they could cancel your warranty. I still have mine on because I use so many different barrels and some make it hard to reach the hammer.

Now about the misfires. I installed a Bellm oversize hinge pin and heavier locking springs. These solved my problem. I am going to look into the heavier hammer spring also. Keep us posted on your results.

I had a similar problem with my slug barrel. I also have the hammer extension on my Encore and when I called T/C, they said that the hammer extension will void your warranty. This is something to think about. If they see the screw marks, they could cancel your warranty. I still have mine on because I use so many different barrels and some make it hard to reach the hammer.

Now about the misfires. I installed a Bellm oversize hinge pin and heavier locking springs. These solved my problem. I am going to look into the heavier hammer spring also. Keep us posted on your results.