Shoulder Bump Issues

[copperking81]

I have a 300 WSM that after shoulder bumping fired brass back .002 inches with a FL sizing die, is still a pain to chamber. In fact, the resistance doesn't start to feel normal until I take it down .020 inches shoulder bump (fired = 1.730. Sized to comfortable chambering = 1.710). I'm measuring with a Sincliar bump gauge and digital calipers. Rifle is a Model 70 with a Bartlein barrel. Loads are on the higher end of tolerances but not out of line or showing signs of too much pressure. Die is a FL Redding.

Thoughts on why that might be? The gun will chamber with the minimal bump but it takes some effort. My biggest concern is I don't want to gal the lugs or damage the gun.

 

[LHSmith]

Is this the first time using this die? Have you checked OA cartridge length? Are the primers seated fully? Measuring bump without primer?

 

[358WCF]

With the #s you've given, it doesn't sound like shoulder bump is the problem. Could it be in the body down close to the extractor groove? Maybe color the body & shoulder with a Sharpie marker (any dark color will work, but I prefer blue as it seems to come off easier than other colors) & see where the contact is happening with your tight cases.

The smith who chambered the barrel might be a better resource than a bunch of yahoo's on the internet who cant feel or see what's going on.

 

[copperking81]

1. New die and only been used to size brass for this rifle so nothing to compare it to.
2. Yes. I'm seating well short of the lands and the issue occurs with resized but empty cases.
3. Still happens with primer removed.
4. Yes, measuring with primers removed.

 

[copperking81]

With the #s you've given, it doesn't sound like shoulder bump is the problem. Could it be in the body down close to the extractor groove? Maybe color the body & shoulder with a Sharpie marker (any dark color will work, but I prefer blue as it seems to come off easier than other colors) & see where the contact is happening with your tight cases.

The smith who chambered the barrel might be a better resource than a bunch of yahoo's on the internet who cant feel or see what's going on.

Good point. I'll shoot them an email.

 

[copperking81]

With the #s you've given, it doesn't sound like shoulder bump is the problem. Could it be in the body down close to the extractor groove? Maybe color the body & shoulder with a Sharpie marker (any dark color will work, but I prefer blue as it seems to come off easier than other colors) & see where the contact is happening with your tight cases.

The smith who chambered the barrel might be a better resource than a bunch of yahoo's on the internet who cant feel or see what's going on.

I'll give that a try. Lets say that the wear does show towards the bottom of the case... what might that indicate is the problem?

 

[LHSmith]

I should have said to check case length-not COAL. Yahoo mistake.

 

[copperking81]

I should have said to check case length-not COAL. Yahoo mistake.

Copy. The case length on all the cases has been below the specified trim to length in my manuals but maybe I'll take a case and trim it down to the nubs and see if that helps. Good thought.

 

[copperking81]

How much do new cases typically expand? The brass I'm using is Nosler and Norma. I have 50 rounds of each and I didn't measure them prior firing so can't say what they were for sure but I do have another new box of Norma that measures at 1.710 and chambers perfectly. If the fired batches were that length, that would mean they expanded .020... not sure if that is a lot or not. Even so, bumping them back .002 from their newly fired size I would think should still work.

 

[LHSmith]

Keep putting successive layers of scotch tape on the case head of a new case that chambers until you get one to just chamber- that number minus 0.002" should be your target bump dimension.

 

[quest450]

Not sure if this is going to help you
Hornady brass, first firing notes
Hornady E420 insert used to measure head space, this is my hunting rifle chambered in 300WSM SAAMI chamber

 

[Rook 6]

Do you anneal between firings? Spring back might be a factor here if I am understanding correctly…

 

[Eagle Six]

How many firings on this brass? and, what is the measurement at the 200 line of your fired brass before and after bumping the should .002"? You might also measure the new unfired brass at the 200 line for further comparison.

 

[txtaxman]

I'll give that a try. Lets say that the wear does show towards the bottom of the case... what might that indicate is the problem?

This could indicate a tight chamber or that the sizing die is too large with respect to the chamber.

What is the diameter of a sized case 0.2 inches above the cartridge base? Compare this to a new case, a fired but unsized case, and SAAMI specs.

Edited to add that Eagle Six beat me to it.

 

[JFrank]

Just sizing 270 wsm today, Redding fl sizing die only reduces the .200 to .554 and .536 at the case shoulder junction, I don’t have a headspace gage so we just knock them back to chamber freely.
Fired brass is .5545-.555 at the .200
.540 at the csj

 

[copperking81]

Ok, I think we're getting somewhere. When I measure at the 200 line (a new concept / term to me... thanks), I get the following...

• Fired brass, shoulder bumped .002 (chambers very tight) = .553
• Fired brass, shoulder bumped .020 (chambers fine) = .551
• New unfired brass (chambers fine) = .549

I'll also say that measuring a little further up from the 200 line, the disparity seems to be getting worse. It then looks to correct.

The Nosler brass has been fired 6 times. The Norma brass twice. The reloads have always been tight, I just lived with it. But its time to get to the bottom of it.

 

[copperking81]

Just sizing 270 wsm today, Redding fl sizing die only reduces the .200 to .554 and .536 at the case shoulder junction, I don’t have a headspace gage so we just knock them back to chamber freely.
Fired brass is .5545-.555 at the .200
.540 at the csj

That's consistent with what I'm seeing. The only way I get the 200 to reduce past .553-4 is to really crank the die down and max out the overcram. That unfortunately bumps my shoulder back .020 though.

I might try a different die brand.

 

[243winxb]

Sized to comfortable chambering = 1.710)

Would this be when the bottom of the fl die is in contact with the shell holder?

 

[copperking81]

Would this be when the bottom of the fl die is in contact with the shell holder?

When the die just touches / kisses the base plate, it'll bump it back to around 1.720. If I turn it down further to where it overcams then it bumps down to 1.710.

 

[wedgy]

You could get a small base die or get a cheap Lee die and cut the top off so it doesn't size the shoulder then grind the bottom until you get the size reduction you need.

who makes the smallest 300 wsm die (base size)

pretty simple who makes the smallest dia base of the current production sizing dies. my current die , a redding, is not quite small enough to get a true bolt free drop. a very minor closing is required and works but i would like to get smaller without getting shorter thanks

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