Difference Between Shoulder bump and Full Length resize
- Thread starter harry_x1
- Start date
Difference is the body diameter. FL sizes the body, SB doesn’t. Yes, the FL also bumps the shoulder.
Several videos out there on this one.
I have never not done full length resizing so my knowledge of other people's methods are limited.
That said imagine if you had a die that never touched the walls of the case except for just at the head and neck area. You can screw the die in or out to control how much you bump the shoulder back.
With a regular full length die though it squeezes the body of the die down to X diameter while also bumping the shoulder back.
One of them does one thing and the other one does that one thing plus another one.
There are tons of schools of thought on this subject. When you fire a round the brass expands outward in all directions until it gets squished into the walls of the chamber on the gun. That means around as well as long wise.
A lot of people go to great lengths to make sure the space between the shoulder and the chamber is minimal.
Factory ammo on the other hand is built to length so that it will fit in almost any random chamber of that caliber.
The way I see it, and from what I have read, with a shoulder bump, your also FL sizing as well. A bushing die will size the neck, bump the shoulder and put the case back into spec, so in my eyes, your FL sizing. Some people see that different than I, but to each their own on that.
Different types of dies.
Neck die sizes only the neck and can use a bushing or not.
A full length die sizes the neck, shoulder and body. Doesn't matter if it's a bushing die or not.
A body die sizes only the shoulder and the body leaving the neck untouched.
A small base die is usually a full length die that is smaller around the base to enable better feeding in semi auto rifles and those with chambers that tend to be on the small side in the base area.
There will be a test tomorrow morning at 8:15.
Please be sure to bring scrap paper and a pair of pre-sharpened #2 pencils.
Neck die sizes only the neck and can use a bushing or not.
A full length die sizes the neck, shoulder and body. Doesn't matter if it's a bushing die or not.
A body die sizes only the shoulder and the body leaving the neck untouched.
A small base die is usually a full length die that is smaller around the base to enable better feeding in semi auto rifles and those with chambers that tend to be on the small side in the base area.
There will be a test tomorrow morning at 8:15.
Please be sure to bring scrap paper and a pair of pre-sharpened #2 pencils.
Forster makes a bump die, maybe others. I've not used one.
Most of the time when people talk about bumping the shoulder they're talking about using a full length die properly (sizing enough to reduce cart headspace to chamber vs sizing to whatever degree the die is capable of).
Most of the time when people talk about bumping the shoulder they're talking about using a full length die properly (sizing enough to reduce cart headspace to chamber vs sizing to whatever degree the die is capable of).
No-one makes a die designed to size only the shoulder leaving the body unsupported and un-sized.
^^^That’s not true.
You are missing the type of die the op is asking about. There are shoulder bump dies. Forster makes them, others might also.
You are missing the type of die the op is asking about. There are shoulder bump dies. Forster makes them, others might also.
What I said was:
Body unsupported AND unsized...
The Forester die supports the body preventing the shoulder/body junction from expanding.
Seems like an extra unnecessary step to make ammunition function in your firearm.
People get wrapped around the axle trying to complicate a simple process.
Set your FL die to bump the shoulder a couple thousands and rock on.
If you want to use bushings to control neck tension, have at it.
You want to take it further and go with mandrel expansion to set neck tension even closer, great, have fun.
At what point are you just making work without seeing any return?
Can you shoot the difference?
BTW,
If your brass is getting too fat at the web where you need to occasionally use a SB die, you're probably over pressure and your primer pockets will announce that to you.
I've come full circle on this stuff and have reverted back to the basics that still work.
It's a lot more fun shooting than sitting at the bench going through steps that don't gain enough to justify doing them.
ETA:
@jakelly I did miss the die the OP mentioned.
10 extra points on your test for catching my error.
Sadly, I was trying to prepare dinner and respond at the same time. That's what I get for trying to multitask...☹
Shoulder bump dies exist because guys who were trying to neck size only (back in the day) found out that after three or so firings the brass wouldn’t chamber or were very tight. That created a demand for a better neck die that also bumped the shoulder, and thus the bump die was born. The thought being if the case body is the same OD, the case will still be held concentric to the bore.
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