Hey Zac, Tom Kaye did a study on barrel length, it's effect on range and such, and I believe PGI featured it when it came out. Anyway, the results for blowbacks was ten to twelve inches. Dang, why did he do research on blowbacks? Okay, maybe it wasn't Mr. Kaye, but this was definitely in PGI in the last five years (and Tom Kaye DID do a study like this). Any more than twelve and you have to begin fighting drag. Which means you have to turn your velocity up, which leads to more gas consumption, which is more fills, and less dough in your wallet. Also, if you put a good quality barrel on your gun, you will notice improved accuracy. There is a gent on this forum named Manike who can explain this more in depth, and lead you to Tom Kayes' results if you're interested. You could probably get his attention in the techroom if you really wanted to. I'm also sure that there are plenty more fella's on here that can help you just as well. You should seriously consider posting in the techroom if it's worth it to you. You may get more "help" than you want though
. Good luck, I hope that was helpful in some way.