Howdy. The Firing Line Chinese post-ban to Firing Line AK-104 conversion is rolling along. I have the barrel turned down so that the new -104 block will fit and am getting ready to cut the barrel to 14" and thread it for the permanent attachment of the Global Trades Krinkov brake. The barrel I'm using has no gas block hole and I'm wondering what sized hole to drill? I could just measure the old gas port from the old barrel but I'd like to get it right the first time.

Thanks.

Port size is dependant on the distance from the chamber and the remaining length of barrel beyond the port.

Do not take port dimensions from another barrel unless the barrel was made exactly the same at the factory as the one you are working on now to try and make it like that one.

Thanks for the info.  I would ideally like to use a hole just large enough to get the gun to cycle reliably with factory ammo.  I'll try drilling the hole progressively larger until I get it running good.

My advice would be to email troy at inrange.

He could give you a good starting number and proabally give you the proper diameter off the bat anyway.  The info is out there, I would not start getting experimental just yet.

Remember, that is a chrome lined barrel.

You want the bit spinning very fast and you want to advance it slowly thru that last littel bit where the plating is so that it cuts it clean and does not strip it and leave rough edges.

I'll have to remember to stop and not drill down through the barrel and out the other side!

Thanks, HM.