Hey guys,
I read recently that one should cull brass that has been fired 4x in an M14 no matter what. I understand the theory why and therefore can accept it but just looking for second opinions. Thanks.
Normally I try not to give useful advice, or add anything of value to a thread, but a
lot of people don't understand this topic. People will say toss the brass after 4 loads, it's generally decent advice, but I can't just accept that without understanding why.
Headspace is the key here, and you have to understand how separation works before you can guesstimate how many reloads your brass can take. When there is excessive headspace, your chamber is longer than the brass going into it. When you pull the trigger, the firing pin shoots the casing forward into the chamber. The round goes off, the case walls expand into the walls of the chamber, and then there is backwards force on the casing. This causes the brass to stretch at the web (head). If you keep resizing the same piece of brass and run it through that chamber, eventually the head will come off and you'll have brass stuck in the chamber.
This will happen faster if you use 308win commercial brass in a longer chamber, say 1.638 to 1.640 but won't happen as fast if you use NATO milspec brass. Norinco cuts the chambers to accept both cartridges, they're usually half way between 1.634 and 1.6340, around 1.638 so you can shoot both. 7.62x51nato brass can be reloaded and shot probably 10 times out of a 1.638 chamber, whereas I bet you'd find 308win brass starting to crack at the web around 5 firings if you used standard M80 loads (2750fps 147g fmj imr4064 powder).
Here are ways you can get around the 4 shot rule:
1) Use nato brass
2) Check your headspace
3) Use the paperclip to feel your webbing
4) Neck size your brass. Despite what people say about this not working in semi's, this is a military battle rifle and is very sloppy. Neck sized brass simply works. I personally do a partial full length sizing with my rifle.
5) Don't load so hot
I hope this helps