Help With Shoulder Bumping

[Green_Three]

I recently bought the Hornady Lock-N-Load Headspace gauge to start bumping my fire formed .223 brass from my bolt action Savage. I read some online guides on how to set up my RCBS Full Length Sizing Die to bump the shoulders back by 0.002".

I started with one batch of brass from a plinking load I have. I lubed my brass and incrementally lowered my die to get in the area necessary to bump the shoulders. Lower and lower I went eventually getting to the light cam-over stage, then to the hard cam-over point of the ram travel. Throughout this process I was measuring the shoulder of the case with no change in shoulder measurement. Scratching my head, I moved on to another batch of brass that was fire formed from a different, higher pressure load. Following the same procedure as before I was able to bump this brass back the desired 0.002" except this time I did not reach any cam-over point. Conceptually sound in my mind. I repeated the process back again on the first plinking load batch of brass, and still no dice on bumping the shoulder back any amount. If anything my brass grew 0.001".

Some data on the plinking batch and the higher pressure load:
Plinking Batch - 21.0gr WC844 in mixed headstamp brass with a 55gr FMJ.
Average FPS - 2468
Higher Pressure Batch - 27.5gr Varget in Federal Brass with a 68gr BTHP.
Average FPS - 3012

My measurement technique:

1. Zero calipers with Hornady gauge on
2. Insert case into caliper set up, twist case ensuring good measurement, and zero the calipers
3. Size brass case
4. Remeasure case to see change
5. Adjust die accordingly to set desired bump
6. Size case
7. Remeasure
8. Repeat as necessary

Now my questions are - is my Plinking load too low pressure to fire form brass consistently? Is differences in brass brand even between "fire formed" brass enough to change the datum point where you measure shoulder bump?

Both batches of fired cases chamber just fine in my rifle without any resizing, and don't exhibit any difficult bolt lift or other pressure signs. I'm just trying to shed some light on my seemingly odd shoulder bumping experience.

[OpenSightsOnly]

I'm just trying to shed some light on my seemingly odd shoulder bumping experience.

It's not "shoulder bumping experience" since what you are doing is a "full length case sizing."

The tool that you have is not a headspace tool per se.

It's a cartridge headspace tool that measures the length of a fired or sized case from the shoulder's datum line. You should have the "A-330" gauge.

If you correctly set-up your FL size die then you can use the cartridge headspace gauge with ease. Yes, when you full size you have to experience that "cam over" feeling since that means that the die is properly set-up and there is no slack in your sizing process.

[OpenSightsOnly]

BTW, since you have two brass lots based on your two different loads, did you get an average length of the fired case? The fired case has to be decapped (not full length sized) prior to measurement.

[kcheung2]

Oh no, "datum point" rears it's ugly head again. Prepare for an endless circular argument.

[NorCalFocus]

It's not "shoulder bumping experience" since what you are doing is a "full length case sizing."

What he is referring too is know as shoulder bumping. He's trying to bump the shoulders back only .001-.002 and not the .005-.007 that a FL sizing die will do if you set it up by the instructions included with the die.



OP, yes different lots of brass can have different outcomes at the press. What I think your batteling is spring back. Thicker brass, or more work harden brass will have more spring back. How many firings on both sets of brass? Have you annealed the cases?

Also FWIW, I could never get my RCBS dies to shoulder bump well. I bought a set of Forster dies and love them.

[OpenSightsOnly]

Oh no, "datum point" rears it's ugly head again. Prepare for an endless circular argument.

lol!

It's relative for the purposes of obtaining a comparative case length before and after full length sizing.

For 30 cal/.308, I used to use a 9mm decapped case as my gauge.

Then I got fancy and went for the Hornady's cartridge headspace set

[Green_Three]

BTW, since you have two brass lots based on your two different loads, did you get an average length of the fired case? The fired case has to be decapped (not full length sized) prior to measurement.

Brass was decapped and SS tumbled prior to this. I had one piece of unfired brass of the higher pressure load. I compared fired vs unfired of the same lot and the unfired measured 0.0175" shorter than the fired. Indicating the brass formed, and my dies were set up to bump the shoulders (moreso than I intended).

OP, yes different lots of brass can have different outcomes at the press. What I think your batteling is spring back. Thicker brass, or more work harden brass will have more spring back. How many firings on both sets of brass? Have you annealed the cases?

Also FWIW, I could never get my RCBS dies to shoulder bump well. I bought a set of Forster dies and love them.

These cases have 2 firings on them. The light load was previously full length sized with cam-over. The higher pressure load was shoulder bumped with a poorman's headspace gauge. I'll compare the two (fired vs unfired) when I get home to see how much the brass is growing with this particular (light) load. I haven't annealed the cases.

Other people have reported RCBS dies don't shoulder bump well. People suggested grinding the shell holder down a few thousandths, but I used a Lee 9mm shell holder which is a few thousandths shorter, and fits the .223 case head. Still no luck bumping the shoulders back.

[NorCalFocus]

Brass was decapped and SS tumbled prior to this. I had one piece of unfired brass of the higher pressure load. I compared fired vs unfired of the same lot and the unfired measured 0.0175" shorter than the fired. Indicating the brass formed, and my dies were set up to bump the shoulders (moreso than I intended).







These cases have 2 firings on them. They were previously full length sized with cam-over. I'll compare the two (fired vs unfired) when I get home to see how much the brass is growing with this particular (light) load. I haven't annealed the cases.



Other people have reported RCBS dies don't shoulder bump well. People suggested grinding the shell holder down a few thousandths, but I used a Lee 9mm shell holder which is a few thousandths shorter, and fits the .223 case head. Still no luck bumping the shoulders back.

Redding makes shell holders with different depths. They come as a set, so all you have to do is swap the shell holder and you gain .002 of bump each time.

[OpenSightsOnly]

What he is referring too is know as shoulder bumping. He's trying to bump the shoulders back only .001-.002 and not the .005-.007 that a FL sizing die will do if you set it up by the instructions included with the die.

Forgot the smiley to indicate the sarcasm, sorry

[OpenSightsOnly]

Other people have reported RCBS dies don't shoulder bump well. People suggested grinding the shell holder down a few thousandths, but I used a Lee 9mm shell holder which is a few thousandths shorter, and fits the .223 case head. Still no luck bumping the shoulders back.

My RCBS FL dies (223/308) are from the 70s and they work just as well as my Forsters 223 FL die set.

I'd go with NorCalFocus comment on getting the Redding shellholder set, saves you time from adjusting that die.

Or, you can return the RCBS shellholder, if it aint too much of an effort, for a replacement. They are really good about that

good luck

[cavemanlrrp]

I'd go with NorCalFocus comment on getting the Redding shellholder set, saves you time from adjusting that die.


good luck

Another vote for the Redding shellholder set.

I used to use folded pieces of post it note paper in the shell holder to lift stubborn cases a little, but the Redding set is handier.

Best
caveman

[fguffey]

Another vote for the Redding shellholder set.

I used to use folded pieces of post it note paper in the shell holder to lift stubborn cases a little, but the Redding set is handier.

Reloaders have gone straight to grinding the top of the shell holder and or bottom of the die with no understanding what they were trying to accomplish. When the case has more resistance to sizing than the press can overcome reloaders thought the solution was to grind on the die and or shell holder. I have never found it necessary to grind the die and or shell holder, I have always raised the deck height of the shell holder with feeler gages. My favorite shell holder is the RCBS because they fit like a hand-me-down shirt. RCBS shell holders fit where they touch.

Grinding; how much? A feeler gage will indicate the amount of grinding. I have never found the Redding Competition shell holders necessary, with a feeler gage I can size cases for short chamber and or long chambers. I do have one Redding Compaction # 6 shell holder set. I paid $5.00 for the set. I measured the deck height of each holder and found 3 of them are off by .001" each. I do not use them but I have them JIC.

F. Guffey

[fguffey]

And I ask; if a reloader believes he can move the shoulder back why can't he prove it. I proved it was impossible, I shorten the case from the shoulder to the case head but the shoulder on the case did not move back. And then there is bump, I ask: "How do you do that?" All of my cam over presses bump. I have presses that do not bump, my presses that do not bump do not cam over.

F. Guffey

[LynnJr]

If your brass isn't too long to begin with there is no reason to bump the shoulders back.
And despite what someone posted shooters do indeed bump the shoulders back on a daily basis even if he doesn't know/understand how it is done.
I rarely find once fired brass needs the shoulder bumped.

[rsrocket1]

As Lynnjr says, you usually need to bump the shoulder back only about once in 3-4 shots.

Try shooting the cases several times and only neck size them. After each session, try chambering the empties. Once you start feeling resistance on closing the bolt, that's when you need to bump the shoulder back. For your reference, that's when you can measure with your case headspace gauge to determine both your gun's headspace and where to adjust your FL die to bump the shoulder back 20 mils.

With my low recoil .308 loads, I neck size only and have gone 10 shots never needing to bump the shoulders back. With higher power loads, I can definitely start feeling when the shoulders need bumping.