ORIGINAL: oldwun
I have used both primers and to tell you the truth I cannot tell any difference. As a matter of fact I cannot tell the diff between them and the reg 209 primer. Having said that I use the Win T7. Why I don't know. Some think they are better and they may be correct while some think it is a marketing tool to increase profits.
If your shooting BP or Sub that is true, however if your shooting smokeless the 777 AND the Kleenbore do not have enough flame to start the smokeless powder. Basically I believe any 209 will work on ignition, however some are longer than other making some guns hard to close, or once fire they expand so much that they are difficult to remove. My recommendation is find one that works for you (easy to put in and take out) and use that all the time. Another thing is that some of the primers put out a lot of carbon and fill up breech plugs fast, it happens on my Savage, and you have to clean them after only 10 shot, which is quite a pain. So buy all you can at $2.00 cuase they are like $7, but stay with them if they shoot well in your MLer. Chap