What's more Important case weight or shoulder bump?

[Karlandco]

Shoulder bump. If your cases weigh differently, how would you know where that + or - weight is distributed. Could be in the case head or elsewhere. If it is, your culling a case that doesn't need to be separated. If you really feel the need, sort them by velocity...and that likely isn't worth the time. However, some do this and feel if "x" case provided "y" velocity then the case is good. If it's outside their parameters of desired velocity it is culled for foulers.

Case volume is another metric than can be employed and after dripping water/alcohol into your 4th or 5th case that too becomes a futile effort. Especially as it changes upon each firing.

Shoulder bump will keep your pressures more consistent, vastly extend the life of your cases and it promotes safety. By only bumping 1 to 2 thou your ensuring significantly less stretch during firing. Leaving minimal space between your shoulder and chamber often will result in better accuracy. If your not getting consistent bump your cases may need to be fired again or perhaps your lube needs to change. Imperial does the best job imo. Resizing should be smooth and steady not grinding or bumpy. Strip your bolt and size a piece of brass long...loaded into the chamber the bolt is hard to close. As you ever so slightly screw the die in the bolt begins to drop with the case sized right. Just a gentle touch of your finger to close the bolt. Measure that one...that's your base to shoulder to model the others after. Quality lube, just touching the bottom stroke of the press handle and a few seconds of dwell time with the case in the die should yield case to case consistency. Also, if your bumps aren't consistent neither is your seating depth. The two are relative in a very meaningful way.

Brass cases of the same lot are not all the same. Small metallurgical variations make sizing and neck tension vary. The amp press is a nice tool that shows you inconsistency in the seating process. This demonstrates brass that's inconsistent with the rest of the crowd. Expensive darn tool at that. A hydro seater with an online seater or even a seasoned reloader with a single stage can "feel" differences while sizing and seating. While doing so the cases that exhibit pressures out of the norm would be culled for foulers. 21st Century hydro press and an online seater should tell you what you need to know. They're also portable and for me make seating depth tests at the range easy. Load long and seat deeper as you test. Hope this helps and good luck

 

[williepete]

me thinks you are mixing apples and oranges...both count do both right, not one or the other...were the cases annealled ?

I do both case weight and shoulder bump sorting and I do anneal after every firing

 

[williepete]

How much variance in your cartridge base-to-shoulder measurements are we talking about? That is usually a pretty consistent case measurement following the re-sizing process. If you're observing more than about .001" to .002" or so variance at the shoulder after re-sizing, I'd be looking for the cause. It may be something as simple as re-setting the sizing die per the manufacturer's instructions, or perhaps obtaining a set of shims. You can sort cases by weight (or not) any time you choose, so I'd focus my attention on getting the re-sizing process as consistent as possible.

I am seeing 001 to 002 variance and I use a set of Redding competition shell holders.
just woundering I just read guys say that only get 0005 difference
that would be great I haven't got there as of yet

 

[williepete]

They are both minor variables in most disciplines. Bump is easier to fix. Case weight is something to explore after the shooter/ rifle system has developed to a much better than average level.

Suggestion - seating depth and neck tension are more important.

can't do much about seating depth other than use a barrel tuner and I am working on consistent neck tension at this time.

 

[williepete]

Maybe I'm reading more into OP's question than intended, but I believe the correct answer is shoulder bump.
That is, if a case is taking bump differently, it's character is different, and the shoulder is only one area that character comes into play. That case could be expanding to chamber differently, affecting peak pressure curve.

It's easy enough to dip anneal to mid case body and reset it's character. I do this with all new cases to begin with. But if one or two size differently than the batch, I toss em. If I get any flyer from a case, I toss the witch.

I've had other shooters tell me this also if they get a odd ball case it goes into the fouler case box

 

[williepete]

Case weight, and even actual capacity does not directly lead to final result. It's not over right there.
There is also brass hardness and chamber clearances contributing to the pressure peak you developed as best. Given this, it would be difficult to predict results case to case.
-A weight of case can be any capacity.
-A capacity can be any weight.
-A case could be hard/soft.
-A chambered clearance bigger/smaller.
-Your clearance can be different from downsizing the sum of these.
-Your pressure peak shaped by upsizing the sum of these.

But, you can shoot a result across a good chronograph.
Don't forget that part of it.

I am getting ready next week to go do some crono work with a better process to get more info than I've had before I am still new to this only been doing it a little over two years and have only reloaded a little over 2k cases thanks.

 

[williepete]

Shoulder bump. If your cases weigh differently, how would you know where that + or - weight is distributed. Could be in the case head or elsewhere. If it is, your culling a case that doesn't need to be separated. If you really feel the need, sort them by velocity...and that likely isn't worth the time. However, some do this and feel if "x" case provided "y" velocity then the case is good. If it's outside their parameters of desired velocity it is culled for foulers.

Case volume is another metric than can be employed and after dripping water/alcohol into your 4th or 5th case that too becomes a futile effort. Especially as it changes upon each firing.

Shoulder bump will keep your pressures more consistent, vastly extend the life of your cases and it promotes safety. By only bumping 1 to 2 thou your ensuring significantly less stretch during firing. Leaving minimal space between your shoulder and chamber often will result in better accuracy. If your not getting consistent bump your cases may need to be fired again or perhaps your lube needs to change. Imperial does the best job imo. Resizing should be smooth and steady not grinding or bumpy. Strip your bolt and size a piece of brass long...loaded into the chamber the bolt is hard to close. As you ever so slightly screw the die in the bolt begins to drop with the case sized right. Just a gentle touch of your finger to close the bolt. Measure that one...that's your base to shoulder to model the others after. Quality lube, just touching the bottom stroke of the press handle and a few seconds of dwell time with the case in the die should yield case to case consistency. Also, if your bumps aren't consistent neither is your seating depth. The two are relative in a very meaningful way.

Brass cases of the same lot are not all the same. Small metallurgical variations make sizing and neck tension vary. The amp press is a nice tool that shows you inconsistency in the seating process. This demonstrates brass that's inconsistent with the rest of the crowd. Expensive darn tool at that. A hydro seater with an online seater or even a seasoned reloader with a single stage can "feel" differences while sizing and seating. While doing so the cases that exhibit pressures out of the norm would be culled for foulers. 21st Century hydro press and an online seater should tell you what you need to know. They're also portable and for me make seating depth tests at the range easy. Load long and seat deeper as you test. Hope this helps and good luck

Yes verry helpful thanks for your time and effort.

 

[JEFFPPC]

Popcorn please.

 

[BowWow]

Shoulder bump, I wouldn't worry about sorting cases by weight unless there was a LARGE weight variance. In this video, Emil explains that most of the weight variance comes from machining the extractor groove.

 

[BowWow]

Oh yeah, it may have been mentioned already, but Inconsistent shoulder bump could come from shooting different loads.... ex.

I made 100 rounds for load development , starting with a lighter charge working my way up to a heavier charge. I measured the fired brass to find the smaller measurement (there was a variance in the measurement from the base of the cartridge and the shoulder) and set the die to bump the smallest case back .002. After sizing I still had some variance in the base to shoulder length. I'm guessing it was from some cases having a lighter lower pressure charge and some having the heavier higher pressure charge. The difference in charges may also affect spring back... not sure but I'm guessing that might be some of it.

The dimension from base to shoulder seems to be more consistent when all the ammo is loaded the same. It confused me a bit at first, because the die didn't change.......

Oh yeah, and anneal the brass every time for consistency.

 

[williepete]

Popcorn please.

do you want butter on that

 

[JEFFPPC]

do you want butter on that

Just a small dab. Thank you for asking.

 

[JFrank]

I am getting ready next week to go do some crono work with a better process to get more info than I've had before I am still new to this only been doing it a little over two years and have only reloaded a little over 2k cases thanks.

I don’t find weighing cases all that informative, on the other hand using a chronograph is a very good way to sort brass by performance/ fps.

Calipers and comparators are what I use but depending on what your goal is you may want to look into more accurate tools when measuring cases, like this digital gage from Larry Willis.

Innovative Technologies - Reloading Equipment

Our patented resizing die can reload Winchester, Remington and Weatherby belted magnums up to 20 times, instead of just 2 or 3 times and the top of the die is a chamber width gauge.

www.larrywillis.com

 

[mgunderson]

can't do much about seating depth other than use a barrel tuner and I am working on consistent neck tension at this time.

You always have seating depth as an adjustment. Unless you shoot br jammed in the lands. Can always shoot shorter that mag length or longer if you single load. Seating depth is more important than powder..... in my opinion.

 

[williepete]

You always have seating depth as an adjustment. Unless you shoot br jammed in the lands. Can always shoot shorter that mag length or longer if you single load. Seating depth is more important than powder..... in my opinion.

I use a cannelure bullet I have a gas gun
use a tuner for harmonics.

 

[INTJ]

Somebody took a case, weighed it, then machined a grain or two off the case head. It was very noticeable, such to the point that you'd see that large a variation in an extractor groove.

If I had time I would do that test myself and post it here.

 

[Ned Ludd]

I am seeing 001 to 002 variance and I use a set of Redding competition shell holders.
just woundering I just read guys say that only get 0005 difference
that would be great I haven't got there as of yet

Keep after it, you'll get there. Perhaps if the brass is fired a couple more times it might settle down. Alternatively, it may require tweaking the die setup slightly. Even though there is a tiny bit of room for improvement (i.e. getting down to only .0005" shoulder variance), I don't think having .001" to .002" is going to hurt much. That's a pretty small increment in terms of the effect on internal case volume, movement in the chamber after the firing pin strike, etc.

 

[Rat Rifle]

I use a cannelure bullet I have a gas gun
use a tuner for harmonics.

Then don’t worry about sorting cases…JMO

 

[INTJ]

I am seeing 001 to 002 variance and I use a set of Redding competition shell holders.
just woundering I just read guys say that only get 0005 difference
that would be great I haven't got there as of yet

It takes a very precise, zero deflection press like a Prazipress or a Zero Press, along with consistency of lube application. Even with that you will get occasional variance due to variations in spring back. And like I said earlier, I don't know that just because my Mitituyo calipers read to .0005" that they all the cases are really within .0005", but they are as consistent as I can get them.

Before you spend $1200 on a press, make sure all your other sizing techniques are sorted out. With most pressed, if you are sizing with cam
over--which will probably require trimming of the die, sanding if the shell holder, or the Redding shell holders that come in various thicknesses--you can get good consistency.