Do I need to watch for stretching and bump the shoulder if I FL resize?

[mljdeckard]

I have accumulated enough .223 and .243 brass to start reloading them for my AR rifles. I am going to start with small-base dies, just to eliminate the guesswork of whether or not I need them.

I have not yet reloaded rifle cases enough that they have stretched enough to need to trim or bump the shoulders, I am just getting into that fun.

So I am reading up on when and how to bump the shoulders, and from what I can tell, if you just over-cam the sizing die, this does it anyway. I will get a gauge to check them, but is it not enough to just do it this way every time and not worry about it?

 

[xphunter]

Hopefully this helps

 

[mljdeckard]

So, with that die set, how he runs them, he bumps the shoulder with the sizing die every time.

I do plan to use the .243 for distance, at least 1000 meters, but I still want to at least start with a small-base die, because I'm running through an AR-10. If I were using a bolt rifle, I might lean more towards a dedicated competition die set just to do everything the same way every time.

 

[xphunter]

Yes, we both shoulder bump every time

 

[Blue68f100]

Shoulder bump is a sizing technique used for bolt rifle not simi-autos. It has nothing to do with press cam-over. It's all about adjusting your sizing die so it moves the shoulder back to your desired position. On bolts it's normally 0.001"-0.002" of the chamber, with simi's it needs to meet SAAMI spec so it will fit your chamber every time. All guns are different when it comes to gas operated guns. I have one AR (6.5CM) that is so well controlled that I only need to move the shoulder 0.002" for it to be sized properly. Then I have another that requires 0.005". I anneal my brass every cycle to keep from splitting necks out. The use of a case gauge will help in determining if you moved the shoulder back enough.

You also need to be aware of your OAL. I have minimum spec chambers in all my AR's. This makes some bullets contact the lands if I use recommended length published i some manuals. The first thing I do with all my bullets is determine at what length I'm into the lands. I then back off 0.020"-0.030". I have found over the years that Sierra Bullets normally have there published recommended OAL at around 0.030". In most all cases I find that I don't have to adj the length more than 0.005".

You also need to run 0.002-0.004" neck tension so the bullet does not move when it's slammed home by the BCG. The recoil spring have enough energy to move the shoulder back several 1/1000's when closing. So a overly long improperly sized brass can get the shoulder bumped, doing so makes the bolt hard to retract.

 

[Slamfire]

I have not yet reloaded rifle cases enough that they have stretched enough to need to trim or bump the shoulders, I am just getting into that fun.

The trim issue does not seem to have been addressed yet. But I have never had an occasion where once fired brass was not over length after sizing. I don't know what is going on, but brass length is always the longest, and exceeds OAL trim lengths on first sizing. And I trim the heck out the case necks.

I used to use manual trimmers and spent entire Baseball World series trimming hundreds of cases. It was slow, luckily baseball is boring and nothing happens so I did not miss much looking away from the television. I experimented and experimented with hardware, and finally ended up with a Gracey trimmer.

Trimming is tedious.