Shoulder Bump Range... What's Acceptable??

[gregmark24]

Good timing with your post. I've just been through this with my 243 Win. Plenty of lubrication is important on the full length die, lack thereof, and accidentally going from custom shellholder 0.004 to 0.002 instead of 0.006 is how I ended up with up to 0.005 farther than my desired 0.002" shoulder bump. In addition, my Hornady headspace comparator gives me inconsistent readings. I took 8 brass between 0.0005 and 0.005 shorter than desired bump, loaded them all with the same powder charge and bullet seating (for same overall cartridge length) and shot them with 0.020 jump. Velocities were consistent, but shoulder bumps more than 0.001" past my desired 0.002" from chamber tight were a full 1MOA worse.
I might add that my Ruger American chamber is almost 0.002" shorter than SAAMI minimum headspace spec.
I think it is essential to have a Go Gauge, which is very accurate, like to +/- 0.00015". I drop this into the round bored headspace gauge and use a LE Wilson caliper gauge above the cartridge base to measure the depth from top. In my instance, 0.002 below top. Since my chamber is 0.0015 smaller than this non chambering Go Gauge, a sized brass measuring 0.0035 gives me an ever so slight resistance on the bolt handle drop with firing pin removed (see the Erik Cortina video about using scotch tape 0.002 thick to help determine chamber headspace). I then full length size looking for 0.0055 to 0.0060
Also, I use the Redding Competition shellholder set. With the 0.010 installed, bring press shaft to top, and screw die down for a slight camover. Start with long brass and shorten the headspace in 0.002 increments with the remaining shellholders (0.008, 0.006, etc). If you need 0.001 between those choices, increase your camover

 

[L.Sherm]

While I agree with you using a pin gauge for measuring inside neck, this guy is shooting mostly for field use. I suspect your inside neck variences are caused by variability in the brass manufacturing process. Thats why some turn their necks. BR is a whole other animal. BR shooters have their gear tolerances so tightly machined, they can process their brass differently. I suspect the op is not as concerned with going completely all the way to the bottom of the rabbit hole. Just a few steps will do. (As if that's possible)

My LR brass is necked turned, there isn't a rabbit hole to speak its all about testing it for yourself and another opinion.
I was in the anneal camp untill I tried it for myself, I still do on my small sage rat stuff. When you say field what does that mean, these forums are all about learning but to tell people there is only one way is wrong, I listen to people who I know test things then if I'm interested I test it for myself and come to my own conclusion.
Accuracy is accuracy this is a LR hunting forum, and there's alot of things BR shooters do thst help me and others to get our handloads better and more accurate. Just because you do something for a long time doesn't mean its the only or better way.
Its hard to get LR rifles down to that .25-.3 m.o.a at long distance, it takes the small things like NK tension, making sure your bump is not all over the place. It does you no good to do a seating depth test going .003 at a time and then have your bump vary .002 or load ammo and CBTO varies .002. Tolerances stack up and thats what makes a difference at LR. Good tuned load that are all pretty much the same thing. What I found is brass prep is a HUGE factor in LR

 

[parshal]

Is there a sizing die that allows adjusting the shoulder bump independent of the body, where you don't have to screw the whole die in or out to achieve the desired bump?

Whidden makes a 'click' die that allows you to move the die in .001" increments without loosening the lock ring. The 'click' is built into the ring and the threading on the die body had detents in it.

 

[Full Curl]

Did you measure the cases before bumping? If there was a variance to begin with then your shoulder bump will not be consistent.

Yes, I did. Not much variance at all... less than 0.001".

 

[Full Curl]

What kind of case lube are you using?

Redding Imperial Sizing Die Wax

 

[Full Curl]

This ^^^ along with how are lubing them? Usually inconsistent bumps are lube related if brass is from the same lot.

I just use my fingers to apply a small film of wax/lube to the case before sizing. I'm sure there are some slight differences from case to case on how much or how little lube is applied but I try to be as consistent as I can.

 

[C-130 Dude]

My LR brass is necked turned, there isn't a rabbit hole to speak its all about testing it for yourself and another opinion.
I was in the anneal camp untill I tried it for myself, I still do on my small sage rat stuff. When you say field what does that mean, these forums are all about learning but to tell people there is only one way is wrong, I listen to people who I know test things then if I'm interested I test it for myself and come to my own conclusion.
Accuracy is accuracy this is a LR hunting forum, and there's alot of things BR shooters do thst help me and others to get our handloads better and more accurate. Just because you do something for a long time doesn't mean its the only or better way.
Its hard to get LR rifles down to that .25-.3 m.o.a at long distance, it takes the small things like NK tension, making sure your bump is not all over the place. It does you no good to do a seating depth test going .003 at a time and then have your bump vary .002 or load ammo and CBTO varies .002. Tolerances stack up and thats what makes a difference at LR. Good tuned load that are all pretty much the same thing. What I found is brass prep is a HUGE factor in LR

The bump I use, as stated, is for MY guns. Using a "standard bump" is a crap shoot. I measured my chambers and cases and arrived at what I posted. The op stated his majority of shooting was for field use (hunting). As opposed to target shooting. Having extreme accuracy for both would be nice, but is it a requirement?Something tells me he wants better accuracy, but at what cost? He did not state what his shooting ranges were. Thers lots of things you can get away with if you are shooting at 100-400 yds that you absolutely can't do at longer ranges. We all want accuracy, no matter the range. But at some point, the individual must come to grips with that reality. Extreme accuracy comes with great time and component cost. No one I've ever spoke to argues with that. The op is the only one that can determine just how far he wants to go chasing accuracy. And how much he is willing to invest. This forum does have a multitude of great info for the journey. Even though I have been reloading for 46+ years, I learn new stuff every day. And this forum provides this. To each, their own.

 

[Full Curl]

If you have not bumped shoulders back until now, how have you established that it needs it and where this position is?

KEC and Cajun make good points. During load development I usually get a couple cases that are difficult to close on after firing. I will strip the bolt and find the point it closes freely at and then go another .0015" - .002. I believe Alex Wheeler has a great video demonstration of this.

Alot of variables at this point. Isolate them one by one until you find that sweet spot.

I didn't bump the cases when they were new for the 1st firing. I did bump them .002" (goal) for the 2nd and 3rd firing and now again for the 4th.

I have my maximum case size shoulder measurement 2.4680" and bump back .002" from there.

 

[L.Sherm]

I agree when you stop learning your done, its why I know some who test constantly.
Theres a " process" Alex posted on LRO about tuning for LR and mine is about exactly the steps he talks about, why I do it that way because I know one of his shooters and shot 1 winter with him saw what he was doing and ask questions so I started implementing some things he was doing and it worked wonders for me literally cut my groups in half at LR. It was a few small things like NK tension and brass prep etc.
The gentleman I'm talking about told me he tunes his Field( hunting) rifles almost exactly the same way.
My ultimate goal on every LR rifle i own is to squeeze every bit of accuracy i can out of it and the ones I do for friends and family, there all " tuned" the same way anymore im not leaving anything on the table so to speak.

 

[Full Curl]

https://redding-reloading.com/online-catalog/35-competition-shellholder-sets
When the shell holder contacts the bottom of the fl die, slop in the press is removed.

The few RCBS & Redding S fl dies i have checked, will not push the shoulder back more then .005" This is not enough shoulder set back to cause problems. Ok for a hunting rifle.

Set back of .010" or more, case separation will happen. May take a few firings.

I had that Redding competition shell holder set and sold it. I'm using a Co-Ax press and traditional shell holders don't work with the standard S-jaws. I could use an adapter plate that would accommodate traditional shell holders I believe.

I've never checked how far my die is capable of pushing the shoulder back.

 

[Full Curl]

I've certainly do "not" have the experience or knowledge of many here ….but a thought and a question!

Are you using a "neck expander" when sizing? If yes, could resistance inside the neck as the expander is withdrawn due to improper/insufficient lube or neck thickness irregularities cause the change in shoulder measurements? Just a thought! memtb

Funny you asked this, I was thinking the same thing and even started another thread on it recently. Long story short, I removed the expander ball from the die when sizing this batch.

 

[C-130 Dude]

I agree when you stop learning your done, its why I know some who test constantly.
Theres a " process" Alex posted on LRO about tuning for LR and mine is about exactly the steps he talks about, why I do it that way because I know one of his shooters and shot 1 winter with him saw what he was doing and ask questions so I started implementing some things he was doing and it worked wonders for me literally cut my groups in half at LR. It was a few small things like NK tension and brass prep etc.
The gentleman I'm talking about told me he tunes his Field( hunting) rifles almost exactly the same way.
My ultimate goal on every LR rifle i own is to squeeze every bit of accuracy i can out of it and the ones I do for friends and family, there all " tuned" the same way anymore im not leaving anything on the table so to speak.

I tune all my guns the same way. What I end having to do with each to achieve my requirements are most often different. I wish that was not the case. No such thing as a cookie cutter approach to it. As the op didn't actually say what his overall goal was for his field guns, I can only guess he wanted some degree of improvement. I hope all the info here helps.

 

[Full Curl]

You said most of your shooting is field use. But it sounds like your looking toward closer tolerances. Try for .001-.002 sholder bump. ALWAYS anneal before sizing. It will set your brass to a constant and repeatable state. This will also prolong your brass life by softening it so it will work the same way. And it will reduce neck splitting. Use and apply you case lube as directed. Watchout for excess lubing. I use wax for small case batchs and spray lube for large batchs. It works for me. Just do it the same way every time. I also use FL w/bushing die. Works well for me. For consistency, the trick is when you are running the press arm, take a 3 second pause at the bottom of the arm stroke. Then pull the arm up. This pause allows the brass to settle and reduce/eliminate brass spring back. You will find better sholder bump consistency. It allows me to achieve .001-.003 consistency every time. I will not use brass that has more than .003. Brass is expensive. After this, always check the case length and trim accordingly. I've been processing my brass like this for more years than I can count and it just plain works. Best of luck!

I always try to get the best results I can when loading even for field shooting use... hence, why I would like a consistent .002" bump. I can certainly incorporate annealing after every firing if necessary but I still have not been able to get a perfectly consistent .002" bump on freshly annealed cases. I also do the 3 second press arm down stroke as you mentioned to reduce spring back. Thanks for the .001 to .003 acceptable range that gives me a good idea to compare my results to. And yes, brass, especially for a 300rum is expensive!

 

[Full Curl]

BR is a whole other animal. BR shooters have their gear tolerances so tightly machined, they can process their brass differently. I suspect the op is not as concerned with going completely all the way to the bottom of the rabbit hole. Just a few steps will do. (As if that's possible)

HA!! Correct! But that dam rabbit hole keeps pulling at me more and more!