Sizing questions

[Wildstreak]

At the risk of sounding like an idiot I have a couple of questions both sizing. How important is consistent shoulder bump to accuracy? How important is dwell time? Do you give it a couple of seconds inside the die or do you extract it as soon as you hit the top of the stroke? I've also heard some folks size their brass, spin it halfway and size again. Necessary?

I have messed with and played with this process until I'm blue in the face. Probably made too many adjustments to fast before getting enough hard data but here we are. Figured some of you might have more data and experience in this area.

 

[MagnumManiac]

Getting consistent shoulder bump is solely relying on stable, fully formed brass. Trying to do so on brass that is yet not stable is a waste of time.
All brass should be fired at least 3 times with neck sizing only to be at chamber dimension BEFORE any sizing is done, and then only that brass should be measured and sizing numbers taken from 5 pieces to average them out.
Also, annealing AFTER every FIRING is also critical.

These steps are the only way I have ever been able to get consistent shoulder bump that is a TRUE measurement. If you size once fired brass, it may end up at .005" bump because the case is most likely still .003" smaller than chamber, this is excessive sizing.

Cheers.

 

[FireFlyFishing]

Getting consistent shoulder bump is solely relying on stable, fully formed brass. Trying to do so on brass that is yet not stable is a waste of time.
All brass should be fired at least 3 times with neck sizing only to be at chamber dimension BEFORE any sizing is done, and then only that brass should be measured and sizing numbers taken from 5 pieces to average them out.
Also, annealing AFTER every FIRING is also critical.

These steps are the only way I have ever been able to get consistent shoulder bump that is a TRUE measurement. If you size once fired brass, it may end up at .005" bump because the case is most likely still .003" smaller than chamber, this is excessive sizing.

Cheers.

This.

I would add, buy the best brass you can afford.

 

[MagnumManiac]

This.

I would add, buy the best brass you can afford.

Even the best brass money can buy needs the same diligence.
I have had to cull Lapua brass due to inconsistent sizing, it still functioned, but was screwy after sizing and firing.

Cheers.

 

[tigerrose01]

Even the best brass money can buy needs the same diligence.
I have had to cull Lapua brass due to inconsistent sizing, it still functioned, but was screwy after sizing and firing.

Cheers.

I definitely agree with you, it just makes it mentally a bit more difficult to put in the "plinkers box"! Thankfully I don't have many of the higher end brass there, but it still happens occasionally.

 

[nksmfamjp]

I would tell you to test all of those with a measuring tool and/or on target before you buy into all that hype.

I've heard it all. I basically run my single stage press as basic as possible. I do make sure I get to stroke end. I have found inconsistent lube and/or dirty dies affect bump and concentricity. That's about it for me. …..and my shocker….bushing dies have more runout!

 

[Doom2]

At the risk of sounding like an idiot I have a couple of questions both sizing. How important is consistent shoulder bump to accuracy? How important is dwell time? Do you give it a couple of seconds inside the die or do you extract it as soon as you hit the top of the stroke? I've also heard some folks size their brass, spin it halfway and size again. Necessary?

I have messed with and played with this process until I'm blue in the face. Probably made too many adjustments to fast before getting enough hard data but here we are. Figured some of you might have more data and experience in this area.

Before you go down the primrose path it is important to have realistic expectations for what your reloads need to achieve. This gives you a defined metric to judge your reloading process. This is important because if your goal is to achieve the smallest group possible you will be searching forever and never meeting that exception.

All are good questions and not stupid. But the answers are not clear cut. What it boils down to is trying to have the case be as consistent as possible from round to round in terms of achieving accuracy. Does the bump matter? Probably but depending on how much it only matters if you can shoot the difference. Does dwell time matter. It probably depends on how quick or how slow you are. You can also double size. It really is trying to limit springback.

There are all sorts of recommendations on the internet, some great, some good, and some quite frankly suck. The recommendations are often based on anecdotal evidence and can be totally wrong.

So what is a guy to do? First and foremost recognize that you must have consistency for repeatability. In the case of sizing, base your consistency on actual measurements not on perception. If you find inconsistency then look at ways to correct those inconsistencies. For instance, if the issue is shoulder setback, then consider that the brass may need annealing or that you need more dwell time since springback is probably the cause.

Remember the Internet can be you friend but it can also be a source of great confusion and incorrect information.

 

[wilehunting]

An RCBS precision mic is a good tool to use to measure the shoulder.

 

[MagnumManiac]

bushing dies have more runout!

So very true.
Number one in removing runout…move your brass the smallest amount possible.
I know many are happy running standard dies from Redding, RCBS, Lyman etc, but when you use honed neck dies that match your brass, you will never want to go back to a standard die in a custom rifle.
The precision is seeable and unquestionable.

Cheers.

 

[MarkInPA]

I have been liking my honed Forster dies myself. Not real big on the bushing dies.

 

[243winxb]

How important is consistent shoulder bump to accuracy?

A bad primer didnt fire in my 223 Savage Axis.
First thing i measured was head to datum.
The firing pin strike set the shoulder back .006"
After pulling bullet, removing powder, the 2nd pin strike set the shoulder back more.

Brass was not annealed.

Makes me wonder how important should bump control is?

Needs tested in guns with different types of extractors & bigger cartridges.

When the cartridge fires, does the pressure keep the shoulder from being pushed back?

Or does shoulder get pushed back & then expanded to the chamber, On firing.

Some one test this, i am to old & lazy.

 

[Koda_]

How important is consistent shoulder bump to accuracy? How important is dwell time? Do you give it a couple of seconds inside the die or do you extract it as soon as you hit the top of the stroke? I've also heard some folks size their brass, spin it halfway and size again. Necessary?

I have not experienced any accuracy differences with various shoulder bump dimensions, my understanding is minimal shoulder bumping is done exclusively to maximize brass life.
I anneal after every firing so I get consistent shoulder bumps, mostly. Occasionally perhaps due to varying case weight extremes some shoulders vary more than my tolerance... I usually just adjust my die a thou up or down but I will try holding a longer dwell time and see what happens.

 

[FEENIX]

Getting consistent shoulder bump is solely relying on stable, fully formed brass. Trying to do so on brass that is yet not stable is a waste of time.
All brass should be fired at least 3 times with neck sizing only to be at chamber dimension BEFORE any sizing is done, and then only that brass should be measured and sizing numbers taken from 5 pieces to average them out.
Also, annealing AFTER every FIRING is also critical.

These steps are the only way I have ever been able to get consistent shoulder bump that is a TRUE measurement. If you size once fired brass, it may end up at .005" bump because the case is most likely still .003" smaller than chamber, this is excessive sizing.

Cheers.

This.

I would add, buy the best brass you can afford.

X2!

 

[Mikecr]

A bad primer didnt fire in my 223 Savage Axis.
First thing i measured was head to datum.
The firing pin strike set the shoulder back .006"
After pulling bullet, removing powder, the 2nd pin strike set the shoulder back more.

Help me understand how you did this testing.
On 1st pin strike, did you strike a new primer, but it did not ignite the powder?
On 2nd pin strike, was this with another new primer?