How do I make sure...

[Chiquita]

By now I know that brass may not form to the chamber on the first firing. So, when reloading for semi auto (AR) how do I know if my virgin fired brass measurements are the chamber measurement or not?

I guess I can measure base to datum on factory ammo and check post firing and record that number. Be safe and assume it is the chamber measurement and bump it and check shoulder movement on the 2nd firing and see if the movement is the same as it was on the first firing.

I hope I am making sense?

 

[Dusty Stevens]

Why bump it after the first firing if you dont need to? Check it in the chamber

 

[Chiquita]

Why bump it after the first firing if you dont need to? Check it in the chamber

With the bolt closing with force, how would I make sure that it fits properly or it is the closing of the bolt that makes it fit forcefuly?

 

[joshb]

I measure a bunch of factory ammo and use the average length to shoulder for resizing for my semi-autos. I’m probably overworking my brass. Oh well.

 

[Rsadams]

Get a headspace comparator and measure your brass fired out of that Rifle... Now measure some factory to get an average of were loaded ammo starts... Then full length size your fired brass .003 or whatever you want , I normally shoot for .003 but sometimes end up .004 because I load for more than one automatic.. This is still WAY less than a die setup per instructions... And all chambers are not created equal...

Since the AR platform is very hard on brass and unless you're using a brass catcher you will lose a few in the grass etc normally before the brass is used up especially if you're not annealing... I don't anneal necks on 5.56 so I honestly don't worry about it... I do the brass prep everytime I reload them... Resize , trim , deburr etc...