Newbie reloading qns

[Duke878]

Okay, I wont be home consistantly to reload for probably another year, so right now im just doing my homework. So if I ask a stupid/obvious qn (in the relaoding world) dont worry, I wont blow myself up....yet

Ill be reloading .308 for my Norc M305, 9mm for my G17 and .223 for my Norc M4.

Ive been watching the reloading videos created by "iraqveteran8888" on youtube and they've taught me alot! But I still have afew elementary qns. The following are based on reloading .308 (if it matters)

1) whats the difference between full length sizing and neck sizing?

2) When prepping your brass, and you're trimming it to "size" how do you know what size its supposed to be? And are there gauges that work with the trimmers to ensure a uniform length?

Many thanks reloading gurus! Try not to flame this thread too harshly. Thanks!

 

[ajarmst]

When you fire a cartridge, the brass expands inside the chamber and conforms to the size and shape of that particular firearm's chamber. When the pressure releases, the brass relaxes enough to extract.

At that point, the casing has been "fire formed" to your particular chamber. It will fit it very well, which has a positive impact on accuracy. However, depending on your chamber, the brass might not properly chamber in another rifle, and certainly you would get no accuracy benefit from using it in another rifle.

If you are going to use that case for the same rifle, simply "neck-sizing" it only resizes the neck so that it has the proper tension to hold another bullet. You then have a reloaded cartridge that has been fire-formed to your particular rifle.

Over time, if you you neck-size only, the cartridge will gradually get a bit larger (and, on bottle-neck cases, the shoulder will move forward) and work-harden from the expansion. After a while, it will no longer chamber properly. This is when you need to full-length resize it if you want to continue reloading it.

Full-length sizing resizes the entire case, including (for example) bumping the shoulder back. It should return the case to specifications, so that it will chamber in any rifle of that calibre. However, you will not see any accuracy advantage to the fire forming any more (until after the next firing, anyway).

Over time, brass will work harden (get stiffer due to bending or expansion). Eventually, it may become so hard as to become brittle and no longer be useful for reloading. Neck-sizing works the brass less, so brass will last longer (withstand more reloadings) if you don't full-length resize often. Work-hardening can be relieved by annealing -- reheating the brass -- especially around the neck and shoulder.

For magazine-fed weapons, you may need to full-length resize as a fire-formed cartridge may not feed properly from the magazine.

 

[ajarmst]

2) When prepping your brass, and you're trimming it to "size" how do you know what size its supposed to be? And are there gauges that work with the trimmers to ensure a uniform length?

There are SAAMI specifications for cartridges of all calibers that specify things like overall length, and this is what you trim to. Some more hardcore guys will work within the acceptable range to get a specified seating depth of the bullet and overall length that works well for their firearm.

Some trimmers (for example, the Lee trimmer) come with a gauge for each caliber (sold separately, of course) that is set to the specific length. Other trimmers have manual adjustments (such as verniers) that allow you to specify what length you want to trim to.