Shoulder Bump Advice

Just after some advice for shoulder bumping brass.

I'm shooting 7mm Rem Mag, which after firing measures around 2.1200" with a headspace comparator.

I also tried some various lengths of brass in my chamber (firing pin out of bolt):
2.1200 inches chambers fine, bolt handle falls down
2.1215 inches chambers fine, bolt handle falls down
2.1230 inches chambers fine, bolt handle has slight resistance
2.1235 inches won't chamber

After resizing, my shoulder is growing out to 2.1230" - which still technically chambers, but is close to not.
I assume this will also cause an issue with the brass moving back and forth a lot.

So, I'm after advice:
What length should I be aiming my shoulder bump to be? 2 thou less than the fired length (2.1200") or the size that won't chamber (2.1235)?
I assumed screwing my die down would help move the shoulder back (rather than make it longer), but I'm already hard on the shell holder. Help?

Hopefully that's enough info! Can provide more as needed.
Cheers

there is an entire thread on this already ......... do a search bud

Screw the die down further & bump it back a couple thou shorter than your measured fired case.

Go off the size that won't chamber as that is what is important.
If its new brass it may take a few firings until you are actually doing much sizing.

Eric Cortina has a video on YouTube I'd recommend watching that. Simple and easy to understand.

If you want to get it spot on its a fairly fine adjustment on die.

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Originally Posted by 6.5 CRD

Screw the die down further & bump it back a couple thou shorter than your measured fired case.

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Didnt he say he was on the shell holder already?

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Originally Posted by Fisherman

Didnt he say he was on the shell holder already?

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You can still wind the die down further so it loads into the shellholder slightly when the press is at full stroke and thus bump the shoulder back further.

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Originally Posted by Sonicjoe

Just after some advice for shoulder bumping brass.

I'm shooting 7mm Rem Mag, which after firing measures around 2.1200" with a headspace comparator.

I also tried some various lengths of brass in my chamber (firing pin out of bolt):
2.1200 inches chambers fine, bolt handle falls down
2.1215 inches chambers fine, bolt handle falls down
2.1230 inches chambers fine, bolt handle has slight resistance
2.1235 inches won't chamber

After resizing, my shoulder is growing out to 2.1230" - which still technically chambers, but is close to not.
I assume this will also cause an issue with the brass moving back and forth a lot.

So, I'm after advice:
What length should I be aiming my shoulder bump to be? 2 thou less than the fired length (2.1200") or the size that won't chamber (2.1235)?
I assumed screwing my die down would help move the shoulder back (rather than make it longer), but I'm already hard on the shell holder. Help?

Hopefully that's enough info! Can provide more as needed.
Cheers

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I don't know what the issue is bud but I do know the rem mag with that belt can be problematic. Mine has a really loose chamber and my Redding body die would really struggle with resizing the brass while my Lee die was obviously a bit looser and was better, maybe excess brass is flowing into length.
Very soon the brass developed a bulge in front of the belt which made chambering difficult...sounds like you are doing some good measuring son that's not the issue.

From your notes 2.1230 sounds like it’s on the money, size to the that

If you brass is growing After resizing it’s likely that you are not lubing the inside of the case neck. This cases your brass to lengthen on the up stroke of the ram.


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Thanks for all the helpful replies.

I guess my main confusion is around what to size to. Seems pointless to bump the shoulder back further when its still chambering at the fired length.
Brass is around 3x fired, so not brand new.

Have been doing a lot of watching and reading (pretty much everything that has been suggested), but can never seem to find what to do if your fired brass size still has a whole lotta length that it will chamber with.

As I say, thanks again and I'll give some more things a try and see how I get on!

Remove the expander then size a fired case and measure to the shoulder , if the case has grown its the die that's the problem . The problem is caused by the case body being sized and the shoulder not engaging the die .
If it only occurs with the expander fitted , lube the inside of the neck .

The former is the more difficult to correct , with rimless cases it's possible to have someone machine a few thou' off the bottom of the die , with rimmed magnums it would depend on the rim clearance within the die . Otherwise, its time to buy ,beg or borrow.
Don't try to reduce the shellholder, it may weaken it to the point of failure , leading to a stuck case .

Greetings,
The tight spot on the shoulder in the chamber may not be where your comparator is measuring so go with the measurement where the case chambers freely. There is one thing to watch on belted cases is a tight spot developing on the body of the case just in front of the belt. This is due to loose tolerances for chambers and dies. The case can chamber with resistance but the shoulder is well short of the chamber. From your description you don't have a problem. Be thankful, others are not so lucky. Check your cases each load for signs of head separation as this can be a problem with belted cases. Cases grow in length when FL resized. The diameter of the case is reduced and with the press ram hard up its bum there is nowhere else for the brass to go, don't worry about it. Just trim to the right length. There are a number of reasons for cleaning and lubricating the inside of the case necks including keeping the necks concentric. Cases stretching due to a lack of lube is an old fable that refuses to die. Frequent tests have disproved this fable but it lives on.
Being an OCD type of chap I do decapping, case sizing and neck expansion as three different operations. De capping the case with a punch set allows the primer grit to be kept away from the die. Expanding the neck from the outside in with the standard button keeps the neck straighter than some standard dies. John Barsness did a test on this a while back. Keep asking questions and developing your skills. There are no stupid questions.
Regards Grandpamac.

Quote:

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Originally Posted by Sonicjoe

Thanks for all the helpful replies.

I guess my main confusion is around what to size to. Seems pointless to bump the shoulder back further when its still chambering at the fired length.
Brass is around 3x fired, so not brand new.

Have been doing a lot of watching and reading (pretty much everything that has been suggested), but can never seem to find what to do if your fired brass size still has a whole lotta length that it will chamber with.

As I say, thanks again and I'll give some more things a try and see how I get on!

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If they are clambering without issue after 3 firings then I'd just stick with what you have.
You only need to size them enough that they chamber and eject without issue, excess sizing will just shorten the brass life unnecessarily.

Quote:

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Originally Posted by Sonicjoe

Just after some advice for shoulder bumping brass.

I'm shooting 7mm Rem Mag, which after firing measures around 2.1200" with a headspace comparator.

I also tried some various lengths of brass in my chamber (firing pin out of bolt):
2.1200 inches chambers fine, bolt handle falls down
2.1215 inches chambers fine, bolt handle falls down
2.1230 inches chambers fine, bolt handle has slight resistance
2.1235 inches won't chamber

After resizing, my shoulder is growing out to 2.1230" - which still technically chambers, but is close to not.
I assume this will also cause an issue with the brass moving back and forth a lot.

So, I'm after advice:
What length should I be aiming my shoulder bump to be? 2 thou less than the fired length (2.1200") or the size that won't chamber (2.1235)?
I assumed screwing my die down would help move the shoulder back (rather than make it longer), but I'm already hard on the shell holder. Help?

Hopefully that's enough info! Can provide more as needed.
Cheers

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Sounds to me you are resizing too much.


Say,,,2.1227 inches. Just enough for the bolt to close, no more.

Quote:

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Originally Posted by grandpamac

Greetings,
The tight spot on the shoulder in the chamber may not be where your comparator is measuring so go with the measurement where the case chambers freely. There is one thing to watch on belted cases is a tight spot developing on the body of the case just in front of the belt. This is due to loose tolerances for chambers and dies. The case can chamber with resistance but the shoulder is well short of the chamber. From your description you don't have a problem. Be thankful, others are not so lucky. Check your cases each load for signs of head separation as this can be a problem with belted cases. Cases grow in length when FL resized. The diameter of the case is reduced and with the press ram hard up its bum there is nowhere else for the brass to go, don't worry about it. Just trim to the right length. There are a number of reasons for cleaning and lubricating the inside of the case necks including keeping the necks concentric. Cases stretching due to a lack of lube is an old fable that refuses to die. Frequent tests have disproved this fable but it lives on.
Being an OCD type of chap I do decapping, case sizing and neck expansion as three different operations. De capping the case with a punch set allows the primer grit to be kept away from the die. Expanding the neck from the outside in with the standard button keeps the neck straighter than some standard dies. John Barsness did a test on this a while back. Keep asking questions and developing your skills. There are no stupid questions.
Regards Grandpamac.

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"The old fable " thing may occur , I don't like to discount any possibility but not to the degree often quoted . Hence , my advice regarding sizing with the expander removed to eliminate that as the cause . It's often easier to appease the doubters than battle with them and I don't like to give the impression of being a know it all , I'm not .
I started a thread on the subject , even with a visual demonstration on YouTube some still thought it witchcraft .

I agree with the above, my experience differs. It easy to try and discount if no improvement.


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Quote:

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Originally Posted by PipIstrelle

"The old fable " thing may occur , I don't like to discount any possibility but not to the degree often quoted . Hence , my advice regarding sizing with the expander removed to eliminate that as the cause . It's often easier to appease the doubters than battle with them and I don't like to give the impression of being a know it all , I'm not .
I started a thread on the subject , even with a visual demonstration on YouTube some still thought it witchcraft .

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Greetings @Piplstrelle,
Mostly for my own benefit a short test was carried out. Two once fired .308 cases, previously fired in the .308 were selected and deprimed with a punch set. Case lengths were measured with one at 50.9mm and the other 50.92. Both measured 42.17mm on the comparator with the .375 inch chamber (I don't have a .400 inch one). Case 1 was sized with the expander assembly removed and a +0.006" shell holder. Case length grew to 51.18mm. The second case was sized with a dry expander replaced. It measured 51.15mm. This was without any neck lube and took quite a bit of force. Last the first case was neck expanded with the expander button, just in and out. Case length was now 51.5mm same as the second case. Both cases measured 42.22mm with the comparator and chambered snug.
This test pretty well agreed with what I had read elsewhere ie: Case stretching takes place when the case is sized and not when the neck is expanded. Expanding the neck shortens the neck and case slightly. Case shoulder length in the comparator was slightly longer after sizing so the shoulder was not set back. The Winchester cases had previously been fired in a test on powder speeds done a few years back. They had produced low single digit velocity variation and excellent accuracy. QED.
Regards Grandpamac.

.2 of a mm give or take..so a flyshit more than a zigzag rice paper......

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Originally Posted by Micky Duck

.2 of a mm give or take..so a flyshit more than a zigzag rice paper......

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A gnats whisker indeed Micky. Still 0.2mm works out to 8 thou in the old money or most of the tolerance between max and trim to length for cartridge cases. Those of us that use light loads and neck sizing in cartridges like the .222 or .303 never have to worry about it. Regards Grandpamac.

But had the brass been fired multiple times without annealing?

With old hardened brass it makes a huge difference if you’re short on lube inside the neck.

Maybe on softer brass not so much


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2.1230 sounds like the one, no need to resize smaller than you need to.

Quote:

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Originally Posted by Dicko

But had the brass been fired multiple times without annealing?

With old hardened brass it makes a huge difference if you’re short on lube inside the neck.

Maybe on softer brass not so much


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Greetings @Dicko,
The brass was once fired and Winchester brass. This is some of the thinnest brass and it was not FL sized before loading. its only prep was to chamfer the inside of the mouth. Any case mouths with dings have the expander button run in and out of the mouth. My brass is annealed after every third firing, after every firing for target brass. The test cases were not annealed to remove one more variable. To me the evidence is clear.
Regards Grandpamac.

Clear but perhaps not relevant GPM if the OP has brass that has been used several times, and is brittle.

You size it down based on individual rifle chamber specs and then alter the specs as you almost flip the bench over trying to get the case out of the fls die. The brass is now over size. A bit of lube and some annealing fixes this.

I’ve had it happen with both .270 and .257 AI brass.


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Around the third firing, no annealing as of yet.
Interesting to see some suggestion to size to 2.1230" to avoid working the brass, when this is quite a big change compared to post firing at 2.1200".
Cheers for all the suggestions, I am reading them!

Quote:

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Originally Posted by Sonicjoe

Around the third firing, no annealing as of yet.
Interesting to see some suggestion to size to 2.1230" to avoid working the brass, when this is quite a big change compared to post firing at 2.1200".
Cheers for all the suggestions, I am reading them!

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It may be worth annealing 2 or 3 cases and fire forming to get a better picture of your chamber dimensions . Unlike rimless cases that stretch from the shoulder backwards to the boltface, rimmed magnums stretch forwards from the rim first .
Not all brass comes from the factory annealed , some are annealed mid' forming .