Full Length Resize vs Controlled Full Length Resize

[QED]

Since you said you measure the case shoulder lengths after sizing each case, what's your SD?
Post your raw data.
It must be in an excel sheet since you are so sure of what you are doing.
What method are you using to set the shoulders all the same length?
Are you stopping a shellholder hard against the die to eliminate press frame stretch or are so sizing with air between the shellholder and the die?

Get over yourself. You do you and I'll do me. But the concensus view in benchrest and PR shooting is on my side. And my groups are fine, thank you very much.

[pacrat]

Wow, this went from helping OP understand varying terminology in an overall helpful manner. To a pissing contest over a .001", difference of opinion pretty quick.

What the hell, do it MY WAY, and there is no need to measure the shoulder set back. I neck size only, and not only don't mind camming the bolt closed. I prefer it.

[tabascoz28]

For neck sizing 3x fired Lapua brass I had a 308 that was very hard to cam on a fresh round. Lifting was also so hard that I was having a hard time keeping the gun in one place. That's when I started down the shoulder bump journey. Still didn't stop me from stretching some expensive .338LM nosler brass. All lessons learned.

[divingin]

Trying to wrap my head around this.. have been watching Erik Cortana youtube videos and was watching his F/L resize last night. He was demonstrating how to bump the shoulder back and additional .002".

Additional implies there was starting point. Where was that starting point that he moved the shoulder an "additional" 2 thou?

Is this additional .002 shoulder bump more than a factory 308 cartridge would have? I assume a F/L resize die would it set it back to the standard measurements, so why is it necessary to bump it back even more?

Dies are adjustable. You can generally adjust them to not move the shoulder at all, or set it to move it way too much.

Will a factory gun (in my case, MRAD) have any trouble chambering a round that was just full length resized without additional .002, or is this for custom guns with tight chambers?

Try this: Take a fired case, and see if it chambers without problems. If it does, you only *need* to squeeze the neck down to hold the new bullet. That said, most people will do something a bit more involved.

I just noticed that Forster sells a 308 Win NM which automatically bumps shoulder .003" for target rifles.

Define "automatically". I think what they're saying is moves the shoulder by a max of 3 thousandths, depending on die adjustment.

Back to my original question, should someone with a factory gun just use a standard F/L and not be concerned with the additional setback, or should you always go straight to the extra setback of the shoulder?

I think there's a misunderstanding in what resizing does, and how (and why) it is accomplished:

Factory ammo is sized to somewhere within SAAMI maximum and minimum specs for a given cartridge (usually towards minimum.) this is to ensure it works in a great majority of rifles out there.

When fired, the expands radially, and the shoulder [possibly] moves forward a bit, and the case mouth expands; all due to pressure, but limited by the chamber.

Resizing is returning those increased dimensions to something that will hold the bullet (resizing the neck), and will fit easily in the chamber (squeezing down the body diameter and possibly pushing the shoulder back slightly.)

Most sizing dies have a shape that resembles a tight chamber: At full insertion, a case will have the body reduced in diameter, and the base to shoulder measurement will be reduced by some amount (depends on the die cut as to how much.)

The problem is that if you simply size to the max effect (i.e screw the die down so it contacts the shell holder/plate when brass in inserted; which, BTW, is how many die manufacturers direct you to set up the die), you will push the shoulders back too far. While the case will chamber easily, and (usually) fire OK, you will run into problems with case stretch (and eventual case failure.)

So the "correct" way to set up the die is a balancing act: measure the length of the case from base to shoulder (commonly, but incorrectly called "headspace"), and adjust the die to reduce that measurement by a couple of thousandths for a bolt gun, or 3-5 thousandths for a semi-auto. This does reduce the amount of body sizing applied; so you should verify the setting works in your rifle (ensure the sized case chambers without resistance.) The balancing act is getting enough body sizing without moving the shoulder more than required.

Short(ish) version: You want to size to alter brass as little as possible while restoring fit in your chamber, but will be limited in doing that by your particular die. So you adjust to get as close to that ideal as possible.

[ar15barrels]

Wow, this went from helping OP understand varying terminology in an overall helpful manner.
To a pissing contest over a .001", difference of opinion pretty quick.

He probably measures a couple of his case shoulders with some caliper attachment and assumes that there is no variation in shoulder length and thinks that because a couple of them measured a specific length that all the others do too.
He probably even thinks that calipers are accurate to 0.001" in his hands.
He's probably using an air gap between his shellholder and sizing die too and unaware of press frame stretch.
There is no data because there are no measurements like he states.

Dude needs to stay in OT where he usually crawls.

[cgseanp1]

Additional implies there was starting point. Where was that starting point that he moved the shoulder an "additional" 2 thou?




Dies are adjustable. You can generally adjust them to not move the shoulder at all, or set it to move it way too much.



Try this: Take a fired case, and see if it chambers without problems. If it does, you only *need* to squeeze the neck down to hold the new bullet. That said, most people will do something a bit more involved.



Define "automatically". I think what they're saying is moves the shoulder by a max of 3 thousandths, depending on die adjustment.



I think there's a misunderstanding in what resizing does, and how (and why) it is accomplished:

Factory ammo is sized to somewhere within SAAMI maximum and minimum specs for a given cartridge (usually towards minimum.) this is to ensure it works in a great majority of rifles out there.

When fired, the expands radially, and the shoulder [possibly] moves forward a bit, and the case mouth expands; all due to pressure, but limited by the chamber.

Resizing is returning those increased dimensions to something that will hold the bullet (resizing the neck), and will fit easily in the chamber (squeezing down the body diameter and possibly pushing the shoulder back slightly.)

Most sizing dies have a shape that resembles a tight chamber: At full insertion, a case will have the body reduced in diameter, and the base to shoulder measurement will be reduced by some amount (depends on the die cut as to how much.)

The problem is that if you simply size to the max effect (i.e screw the die down so it contacts the shell holder/plate when brass in inserted; which, BTW, is how many die manufacturers direct you to set up the die), you will push the shoulders back too far. While the case will chamber easily, and (usually) fire OK, you will run into problems with case stretch (and eventual case failure.)

So the "correct" way to set up the die is a balancing act: measure the length of the case from base to shoulder (commonly, but incorrectly called "headspace"), and adjust the die to reduce that measurement by a couple of thousandths for a bolt gun, or 3-5 thousandths for a semi-auto. This does reduce the amount of body sizing applied; so you should verify the setting works in your rifle (ensure the sized case chambers without resistance.) The balancing act is getting enough body sizing without moving the shoulder more than required.

Short(ish) version: You want to size to alter brass as little as possible while restoring fit in your chamber, but will be limited in doing that by your particular die. So you adjust to get as close to that ideal as possible.

[pacrat]

OP said;

Trying to wrap my head around this.. have been watching Erik Cortana youtube videos and was watching his F/L resize last night.

One thing to keep in mind when doing such. Erik Cortina is a rich guy with a very expensive hobby. Which is "F Class" competitive shooting. And vast majority of his videos are tailored to match. Other than generalizations of terms. Which you discovered in this thread.

Nothing he does is geared to the average guy, with a factory rifle, with a generous factory chamber. Or off the shelf dies, and reloading equipment. Which requires a whole different set of reloading procedures to get best case accuracy from available "average guy" equipment.

ETA ..... Example of Cortina's equipment. Look at post #1 of this thread. https://www.calguns.net/calgunforum/...3#post26136763

See that electronic powder measure "PROMETHEUS".

Here is a pricing guide. https://prometheustoolcorp.com/pricing STARTING at $5,100

[divingin]

Any die has a max amount that it will size/bump (depending on what you're measuring): That occurs when a case is run into the die such that, at full insertion, the die is in hard contact with the shellholder. You can screw the die in further, but you're not going affect the brass in any meaningful way.

At the other end, any die has a minimum amount it will size/bump: Zero. Screw the die out such that you don't touch the brass, and when you run it into the die, nothing happens.

In the middle, you have, depending on die position, an infinite number of settings that will work the brass to varying degrees. Those settings are the ones that you use to set the shoulder where you want it.

Note that with a standard die (machined with a neck, shoulder, and body) one setting affects all the others. So the amount of body sizing you do depends on where you want to get the shoulder. That's the balancing act. Luckily, nearly all dies will get you to a point where the brass comes out within a usable range. If you want to be more precise about certain measurements, you get (more expensive) dies that will do what you want, or pony up and have a custom sizing die made to your specs.

[LynnJr]

Original Poster
The confusion came in when you thought he adjusted his dies an additional 0.002 from the national match dies.
The national match dies are setup to bump the shoulder 0.003 and Eric is only bumping his shoulders 0.002 which is less bump not more.

A common mistake most new reloaders make is they bump the shoulders back on once fired brass to some internet determined number.

Your brass needs to be fired until it fully fits the chamber before you even know the correct shoulder length then you bump it back from that distance.