What's more Important case weight or shoulder bump?

[williepete]

So, you are sorting all your resized brass by weight and say out of 50 cases you get 65% of them the same weight.
Then you take that 65% and check for shoulder bump and find that only 70% of the same weight cases have the same shoulder bump.
My question is what do you think is most important for precision ammo case weight or shoulder bump?

 

[rwj]

No idea… my shooting skills have not yet led me to even ask the question!

 

[dgeesaman]

My brass all have the same shoulder bump measurement after about three firings. If you don’t have enough firings your brass might not be there yet.

I don’t weight sort my brass, but then I don’t shoot long range and I use only Lapua, Peterson, and Alpha. In my testing weight sorting had no measurable effect.

So what brass, what caliber, how many firings, and what application?

 

[Sandstorm]

Dont bother with weight sorting your brass...and you need to fire them a few times before your
shoulder set will stabilize from my findings. YMMV however..just my2c

 

[jepp2]

My question is what do you think is most important for precision ammo case weight or shoulder bump?

You don't say what constitutes the "same weight" or the "same bump".

Think about the importance the top shooters give to bullet seating depth. As little as 0.003" in COAL (or CBTO) can affect the tune. The bullet seating depth change, results in changing the case volume, and of course the bullet jump.

I weight sort because it costs me nothing and at least I know the 50 rounds in my box were similar weight. When I size, I typically hold the case head to datum length to less than 0.001" variation. I'm content with those actions regarding your question. But there is more I don't know about what you are asking than I do know.

 

[Sleepyhollow]

If you have time and it makes you feel good by all means weight sort brass. But for me it's a total waste of time. Number 1 reason is because you have no idea as to where the extra weight is from or lack of weight. Is in the case head , ejector ring or maybe in the neck ? Either way don't matter and quality brass like Lupua to expensive to waste.
Shoulder bump will very from light loads to heavy loads. Once you find the load the gun likes set your die for that load. But the will very ever so slightly cause of spring back. If you wanna get that particular get you some die shims and check every round and make the. All the same. Precision reloading a large rabbit hole my friend.

 

[One Eye Pete]

Sorting by case weight doesn't do much for the reasons stated above by Sleepyhollow.
What is very important to accuracy is bullet seating depth. Shoulder bump affects seating depth because the firing pin pushes the bullet forward by the amount the shoulder is pushed back before the primer ignites. Too much shoulder bump is the same as seating the bullet too long. Therefore if your shoulder bump is not consistent your seating depth will not be consistent. Annealing not only helps with consistent neck tension but also with shoulder bump since it helps keep the amount of spring back in the brass consistent. When you are sizing the brass and trying to keep shoulder bump exactly the same everything counts including too much lube on the case neck & shoulder. Its not only the bullet seating die that gives you consistent seating depth but the sizing die too.

 

[K22]

If you shoot long enough you will discover, within reason, that the most significant variable is the shooter.

I have never and never will weigh cases and separate them. For me, it has no value at all since I can achieve my accuracy standards and then some without doing this. The extent to which one goes in the reloading process to achieve needed accuracy is dictated by the discipline one shoots. For example, benchrest guys are trying to shoot into the .1's or less consistently. For most of us that is simply not practical or needed. For me, being a "precision" varmint / predator hunter, a precision level of 1/2 to 5/8" moa will meet all my needs.

Ryan Cleckner talks about "acceptable accuracy". In my opinion this make a lot of sense for a lot of us practical shooters / hunters. Determine the level you need then work towards that goal in your reloading. Once you establish that, you will achieve more dividends by working on improving your shooting skills that trying to squeeze out another .1 or .2 reduction is group size on the bench.

Sizing is a totally different issue because it can affect functionality which is supremely important for most shooters, especially hunters. Learning how to set up your sizing die to achieve the optimum sizing is crucial to producing functional ammo.

The consistency of sizing has been discussed extensively in this forum so there is no need to repeat it here. There are many approaches and theories. Just watch all the videos on this subject and you'll get a headache for sure. Select one that makes sense to you after you've done some research then test it.

 

[Doom]

If your brass is the same lot produced on the same machines at about the same time then weight sorting is probably a waste of time because odds are they are consistent. If they were produced on different machines then it's really questionable for reasons mentioned above.

As for shoulder bump, I doubt that you can show that one or two thousandth either way would show a statistically significant difference in either velocity or POI.

 

[williepete]

thank you all for the in put

 

[Murray Brook]

Can't do much as to case weight other than sort. On the other hand you can cure shoulder bump #'s in several ways.

 

[762plinker]

So, you are sorting all your resized brass by weight and say out of 50 cases you get 65% of them the same weight.
Then you take that 65% and check for shoulder bump and find that only 70% of the same weight cases have the same shoulder bump.
My question is what do you think is most important for precision ammo case weight or shoulder bump?

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

 

[Ned Ludd]

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.

 

[mgunderson]

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.

 

[Dusty Stevens]

Apples and tomatoes

 

[mikecr]

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.

 

[Turpentine]

I do weight sort but only looking for large outliers. I use Winchester, federal, RP, hornady, and LC brass depending on the rifle. Some of my brass is 55-60 years old. Most a lot less. But some companies weights range quite a bit from the old days to now. 20 grains or more. In brand new Winchester brass straight from factory if you have a piece that’s 10 grains heavier it’s best to chunk that piece. There’s a problem there. And it does happen.

Im tight on shoulder bump. I want my pieces the same in this regard.

 

[INTJ]

We want cases to be all the same internal volume, and weight is a rough correlation. Shoulders ought to be kept within .001" when sizing.

 

[mikecr]

We want cases to be all the same internal volume, and weight is a rough correlation.

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.

 

[INTJ]

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.

Again, weight sorting gives us a ROUGH correlation to case capacity. When I weigh 100 or 200 or 300 cases and find one or two that is five grains heavier or lighter, I cull them.

The best way would be to check water capacity of fired cases, but that comes with it own set of inconsistencies and issues. Weighing on an accurate scale is precise and repeatable. Filling cases with water introduces another variable, and that is getting the level of the water consistent across all the cases you weigh. Alcohol drains out of a fired case, so it isn't a good solution. I know one shooter who uses ball pistol powder.

The point is, any method we use is only a rough approximation of the internal case volume when the case is being fired. I know that my method works, because I have shot 5" and better 10-shot groups at 1000 yds in good conditions. My case sorting isn't the only factor in that, but it is part of the recipe.

The chronograph is also only a rough indicator. The target, at longer ranges, is usually our best report card.