Shoulder bumping factory ammo

[CA_Shooter]

I'm wondering if what I'm seeing makes sense.

I have some Hornady SSTs that I shot, and have resized the brass a few times.

I was comparing the SST brass with some other brass I've shot 5x times and annealed a few times.

I found that 3x fired brass from the SSTs (original firing plus reloaded twice) is shorter than the brass that I have shot 5x.

After getting confused and measuring a bunch of times, what I found is the following headpace measurements for the brass:

SSTs (unfired, factory loads) = 1.5555
SSTs (fired 3x, reloaded 2x) = 1.5610 to 1.5615
Brass resized and shot 5x and annealed twice = 1.5640

So it seems that the factory loaded headspace has a lot to go to meet chamber specs. Even after 3 firings it still has room to grow.

Just thought this was interesting. Any red flags here?

 

[piie]

Nothing weird here. All brass are not created equal.

 

[milboltnut]

Factory ammo is sized/headspaced to make sure it chambers in any firearm. So it is a waste of time to size at all.

 

[243winxb]

When there is a crush fit when closing the bolt, then you get a true measurement of head to datum of the brass.

 

[jelenko]

My take is the Factory SST is much shorter than than your chamber - how would bumping the shoulder help?
Assuming the measurements on the 3X fired SST and the 5X fired brass are after they have been resized - it would seem that the factory ammo is more than 9 thousandths shorter than your chamber.
To confirm, how much shoulder bump is your die set up for?

 

[CA_Shooter]

To update, I measure virgin Lapua brass and its equal to the unfired SST: 1.5555

I am measuring using the Hornady headspace gague, using the .375 size as recommended by them.

My take is the Factory SST is much shorter than than your chamber - how would bumping the shoulder help?
Assuming the measurements on the 3X fired SST and the 5X fired brass are after they have been resized - it would seem that the factory ammo is more than 9 thousandths shorter than your chamber.
To confirm, how much shoulder bump is your die set up for?

I think my title is confusing, sorry about that. I am only bumping after firing. Not before.

I thought I was set up to bump .002. When my brass was at 1.563, I resized my brass to 1.561.

Then after the most recent resizing, I'm at 1.564 so I'm a bit confused. I did anneal this brass and had not previously.

 

[milboltnut]

zeroing your calipers and keeping the blades clean as well as the comparator. And the case shoulder as well as the case head surface.

 

[Richard Coody]

To update, I measure virgin Lapua brass and its equal to the unfired SST: 1.5555

I am measuring using the Hornady headspace gague, using the .375 size as recommended by them.

I think my title is confusing, sorry about that. I am only bumping after firing. Not before.

I thought I was set up to bump .002. When my brass was at 1.563, I resized my brass to 1.561.

Then after the most recent resizing, I'm at 1.564 so I'm a bit confused. I did anneal this brass and had not previously.

Setting up a die to bump the shoulder after the first firing is a common mistake. You should only be sizing the neck until that brass chambers tight (quits.growing). At that point then you can set up a 1 to 2 thousands shoulder bump. I think it goes right by most people until, like you, something makes that little light bulb come on.

 

[K22]

Your rifle chamber is the ultimate gauge to determine the need to and degree of shoulder bump.

It's common that new cases require one or more firings before fully fire formed depending the rifle and brand of cases and thus shoulder bumping may not necessary.

However I full size every time but if a fired cases chambers easily then I FL size with zero shoulder bump the first reloading. Normally, in my rifles, I see some increase in case head space after the first firing. The case also expand radially in addition to lengthwise thus my desire to FL to assure easy chambering.

During case prep of new unfired cases I always FL size to uniform the cases and necks but I size with zero shoulder bump. When setting up the FL die for zero shoulder bump some cam over may be necessary to avoid extruding (lengthening) the case. So I measure the new case and set the FL die for zero bump.

One thing I noticed with a friend of mine's Hornady tool is that because inserts are required and fit into the body of the tool there is an interface and at least with his tool, if you rotated the insert you could get different readings. I solved that problem for him by placing match marks on the insert and body so that he aligned the insert with the body the same way each time.

I use the Whidden bump gauge which is caliber specific and requires no inserts thus no interfaces. I'm not implying that the Hornady tool is inferior, only that by placing match marks to assure consistent alignment it may enhance the repeatability of measurements. Also, the Hornady anvil attachment was not square to the jaws of the caliper and caused erratic readings. In his case, the tool worked more precisely without the anvil.

 

[CA_Shooter]

Setting up a die to bump the shoulder after the first firing is a common mistake. You should only be sizing the neck until that brass chambers tight (quits.growing). At that point then you can set up a 1 to 2 thousands shoulder bump. I think it goes right by most people until, like you, something makes that little light bulb come on.

Thanks for the tip! My last sizing sized to 1.564 but I didn't measure what it was before sizing (realize now I should have). I'll do this next time to see how much it grows after firing.

I guess I'm also very surprised by the amount of growth from virgin brass to a later firing.

I took a piece of brass and used the scotch tape method to see how long it will take to get the brass tight.

Using a piece of brass that is 1.562:
1 piece of tape (1.564) - seems fine
2 pieces of tape (1.566) - pretty tight but still closed muscling it down.
3 pieces of tape (1.568) - super tight and can't drop the bolt at all without extreme muscling but didn't even want to try.

If my last sizing ended up with brass at 1.564, then does that mean I haven't actually been bump sizing? I think I need to really pay attention to the before and after of my sizing!

I think what I've done is measure brass at different stages which clearly was wrong. Thabks for the advice, guys. I need to be more diligent with my data collection

 

[milboltnut]

Your rifle chamber is the ultimate gauge to determine the need to and degree of shoulder bump.

It's common that new cases require one or more firings before fully fire formed depending the rifle and brand of cases and thus shoulder bumping may not necessary.

However I full size every time but if a fired cases chambers easily then I FL size with zero shoulder bump the first reloading. Normally, in my rifles, I see some increase in case head space after the first firing. The case also expand radially in addition to lengthwise thus my desire to FL to assure easy chambering.

During case prep of new unfired cases I always FL size to uniform the cases and necks but I size with zero shoulder bump. When setting up the FL die for zero shoulder bump some cam over may be necessary to avoid extruding (lengthening) the case. So I measure the new case and set the FL die for zero bump.

One thing I noticed with a friend of mine's Hornady tool is that because inserts are required and fit into the body of the tool there is an interface and at least with his tool, if you rotated the insert you could get different readings. I solved that problem for him by placing match marks on the insert and body so that he aligned the insert with the body the same way each time.

I use the Whidden bump gauge which is caliber specific and requires no inserts thus no interfaces. I'm not implying that the Hornady tool is inferior, only that by placing match marks to assure consistent alignment it may enhance the repeatability of measurements. Also, the Hornady anvil attachment was not square to the jaws of the caliper and caused erratic readings. In his case, the tool worked more precisely without the anvil.

Your rifle chamber is the ultimate gauge to determine the need to and degree of shoulder bump.

bad advice.... going by feel is not a good way to gauge in this situation. Gauging with a gauge is. Hornady gives a good way of determining what H&S busing to use if they don't list a particular cartridge. Measure the top diameter of the top of the shoulder and the bottom of the neck, add them, and divide by 2.

 

[CA_Shooter]

Your rifle chamber is the ultimate gauge to determine the need to and degree of shoulder bump.

It's common that new cases require one or more firings before fully fire formed depending the rifle and brand of cases and thus shoulder bumping may not necessary.

However I full size every time but if a fired cases chambers easily then I FL size with zero shoulder bump the first reloading. Normally, in my rifles, I see some increase in case head space after the first firing. The case also expand radially in addition to lengthwise thus my desire to FL to assure easy chambering.

During case prep of new unfired cases I always FL size to uniform the cases and necks but I size with zero shoulder bump. When setting up the FL die for zero shoulder bump some cam over may be necessary to avoid extruding (lengthening) the case. So I measure the new case and set the FL die for zero bump.

One thing I noticed with a friend of mine's Hornady tool is that because inserts are required and fit into the body of the tool there is an interface and at least with his tool, if you rotated the insert you could get different readings. I solved that problem for him by placing match marks on the insert and body so that he aligned the insert with the body the same way each time.

I use the Whidden bump gauge which is caliber specific and requires no inserts thus no interfaces. I'm not implying that the Hornady tool is inferior, only that by placing match marks to assure consistent alignment it may enhance the repeatability of measurements. Also, the Hornady anvil attachment was not square to the jaws of the caliper and caused erratic readings. In his case, the tool worked more precisely without the anvil.

Since I know that my new brass will need to grow about .009, should I resize the brass before loading just to get it to grow a bit prior to firing it?

 

[jelenko]

I probably wouldn't make a difference

 

[K22]

Your rifle chamber is the ultimate gauge to determine the need to and degree of shoulder bump.

bad advice.... going by feel is not a good way to gauge in this situation. Gauging with a gauge is. Hornady gives a good way of determining what H&S busing to use if they don't list a particular cartridge. Measure the top diameter of the top of the shoulder and the bottom of the neck, add them, and divide by 2.

I will agree to disagree - before there were gauges this is the way it was done to set the FL die for optimum sizing and it worked quite well. That's not to say that you should substitute this method for measuring set back - you shouldn't. That's not to say that this method is superior to measuring set back - it's not.

It is to say the the rifle chamber is the ultimate test to whether a sized case properly fits the rifle chamber because that is the goal of sizing without over sizing. You may find that the conventional .001 to .002" measured set back is not enough for a given rifle / brand of cases combo. In other words, assessing the sized case fit in the rifle chamber is simply a check on die set up and bump measurements you're using.

By removing the fire pin assembly you can get a fairly accurate "feel" indication of the case fit in the chamber. True it takes a little experience to judge the optimum fit but it isn't difficult. I don't check every case, just one or two to verify that the initial FL die setup for a group of dedicated case for a given rifle provides the proper case fit.

 

[milboltnut]

I hope you don't rely on feel when you have chamber another round on a big buck.

"I don't check every case, just one or two to verify that the initial FL die setup for a group of dedicated case for a given rifle provides the proper case fit."

Annnnd all brass doesn't behave the same... they all should be checked, so yes feel isn't the best way to go. I rely on my die and case gauge when loading my M-1, and I drop below the high step enough to make up for a margin of brass flexing.... but for my hunting bolt gun, I check each case.

 

[K22]

Since I know that my new brass will need to grow about .009, should I resize the brass before loading just to get it to grow a bit prior to firing it?

Does the case chamber without resistance in the rifle?

Most new cases I've encountered will chamber easily without any sizing. Like I said, I FL new case with zero shoulder bump to uniform the case and neck provided the new cases chamber without resistance. If a new case doesn't fit the chamber then I set the shoulder back but this is rare.

I've only encounter one lot of case, Hornady 223 Rem's where the new cases were a little over sized for one of my rifles that has a Douglas match barrel. I had to set the shoulder back to get the cases to chamber without excessive resistance. Rifle chambers, dies, and case lots can vary that's why I always check my initial die setup (sized case) against the chamber of the rifle.

 

[K22]

I hope you don't rely on feel when you have chamber another round on a big buck

The only time I ever had a problem with chambering is when I was a novice reloader many many years ago using neck sizing. Since then I adopted proper full sizing methods I never had a reload fail to chamber.

If the full sizing die is set up for the proper shoulder set back, generally .001 to .002" then you shouldn't have any chambering difficulties. However it's always prudent to check the initial die set up by spot checking a sized case in the rifle chamber. If a set of cases are dedicated to a specific rifle and firing is rotated creating uniform wear on the cases then you shouldn't have any chambering problems with properly full length sizing.

If I'm reading your assertion correctly, relying solely on measurements without verifying actual fit in the rifle chamber does not give me the assurance I need. To be clear, I set up my FL dies to produce a .001 to .002" shoulder bump using a bump gauge and caliper. But I also verify the die setup by checking one or two sized cases in the rifle chamber. Isn't that the goal - to size the case for optimum fit in the rifle chamber?

Since I'm primarily a hunter, i.e. varmints, predators and deer, functionality is critically important to me. It's the main reason I abandon neck sizing many years ago.

 

[potatojudge]

So, given a rifle that requires modest force to close the bolt on once fired brass (fired in this rifle) , am I

A) not setting the shoulder back still so long as I can make it chamber
B) setting the shoulder back a certain amount, or
c) setting the shoulder back until a stripped bolt will just close easily on the round?

This would be loads shooting for groups and longer range steel. Hunting rounds I know how to make- they chamber easily.

 

[JFrank]

I would size - .002 from C

 

[Richard Coody]

So, given a rifle that requires modest force to close the bolt on once fired brass (fired in this rifle) , am I

A) not setting the shoulder back still so long as I can make it chamber
B) setting the shoulder back a certain amount, or
c) setting the shoulder back until a stripped bolt will just close easily on the round?

This would be loads shooting for groups and longer range steel. Hunting rounds I know how to make- they chamber easily.

So, given a rifle that requires modest force to close the bolt on once fired brass (fired in this rifle) , am I

A) not setting the shoulder back still so long as I can make it chamber
B) setting the shoulder back a certain amount, or
c) setting the shoulder back until a stripped bolt will just close easily on the round?

This would be loads shooting for groups and longer range steel. Hunting rounds I know how to make- they chamber easily.

There are no rules here. Whatever works for you.

For me when that case chambers tight that is when I set up my shoulder bump. For me that sized case should chamber easily. You can do it by feel or by measuring base to shoulder datum. After sizing I always check a few for easy chambering. If you use the feel method to set up your bump I recommend measuring the first few times you do it. Once that die reaches the shoulder just a tiny amount of die adjustment creates a lot of shoulder set back. Easy to overdo it.