These are critical first steps to make sure your brass is sized correctly. If you are having problems with your first batch of brass, make sure you are following these directions precisely because if your brass is sized too short it will fail to fire, too long and the bolt will not lock into battery and you have a fail to fire.
Wade has described this in detail, but I thought it was worth reposting. This is his directions with a few of my photos...
"Starting with LC 5.56 once fired brass.
Resize using the mongoose size die with a .010" space between the shell holder and the die. This can be accomplished with a +.010" redding shell holder from their comp. shell holder set, or by using a shim between the die base and the top of the shell holder, or by backing off the die to create the gap (least likely to give consistent results).
Trim brass to 1.690", chamfer and de-burr and remove primer crimp if not already removed.
Try to chamber your newly formed piece of brass in your rifle.
Does it go easily into battery (see photo)?
If yes then go on ahead with your loading procedure.
If no then set this case to the side and start over with a new piece of brass and reduce the space between the shell holder and the die to .008" with whichever method you selected on the first piece of brass.
Keep reducing the space between the shell holder and die and resize with a new piece of brass until your brass closes in the chamber without effort. Always be sure to keep the trim length to 1.690" which is max case length.
The reason for using a new piece of brass each time is because the brass that you just sized will not want to move with the .002" bump that you create when reducing the bump gap. It will likely try to spring back to where it was on the first sizing. Just set it to the side and start with a new piece.
Once you have your die/shell holder set so that your brass will chamber you can now go ahead and start loading whichever bullet/powder/primer combination that you want.
Once you have some loaded the neck diameters need to be checked to make sure there will be no interference in the chamber. The maximum diameter that a loaded neck can be is .269". the chamber neck is .271" so you will need .002" minimum room in order for the bullet to release cleanly from the neck and not create a high pressure situation.
The chamber reamer dims are set around LC brass as the parent and its neck thickness. All of the LC brass that I have used clears the neck with some room to spare. Some other manufactures might not work without neck turning. Those need to be checked near the neck/shoulder jct. to be sure. I know for sure Lapua necks will need to be turned because of how thick the shoulders are on them. I also checked some TA surplus brass that was close to .269" after loading. So I turn those two manufactures brass for sure before loading them.
From all of the load data that I have seen, the published data (not data from Joe Blow off the internet) from various sources are showing max loads for 6x45 to be midrange loads for the mongoose. I have been going half way between max and min for the 6x45, start my ladders there and work up. I have been ending up around a grain or two over max listed loads for the 6x45.
As you all know, there is not a max length for it. You will have to determine where your length needs to be based on your projectile choice. We cant just load to 2.2XX" and call it good because some projectiles will be into the lands at a shorter OAL. You will need a modified case, or use some other method to determine where your projectiles hit the lands and load accordingly.
One last important thing! This is for any hand load! If you have a loaded cartridge that does not go into battery, do not force it into battery. Something is wrong with it. set it to the side and take some measurements later. It could be a thick neck, loaded too long, jacked up case. Just don't try to force it to shoot. It can bite you!"
Setting up your sizing die. (case trimed to 1.690") Start long and adjusted sizing die until the bolt locks up with little effort.
It helps to remove the ejector and extractor from your bolt for this step to get a more precise measurement, but its not all together necessary, I just feel its easier this way.
Category: 6mm Mongoose