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Are you trimming all your cases uniformly to spec after resizing? When seating your bullets, if one neck is longer than the neck you set your die to, the shoulder will deform.
 
As stated earlier you need to flare the case mouth when seating lead bullets, but sometimes you need to do so with jacketed too.

Some brass has thick enough necks combined with enough spring back that seating a flat-based bullet will cause several problems, one of which is buckling the case. Even if you are not crushing the shoulder you are probably shaving the heel of the bullet a bit which will reduce accuracy.

Get a Lee universal case expanding die, and then you have what you need when you see this condition, regardless of the case you are loading. And you have it handy when you load lead projectiles too.


I load flat-based bullets for my Garand on a Dillon 550C. Since I prime rifle off the press, I put this die in station 1 and flare (tiny bit is all that is needed, if the bullet can easily set on the mouth your there) every case. It makes seating so much smoother and does not impact case life in the least. The case will wear out from other things first. My accuracy "seems" to be better too. I can't say for sure since these are Garands so they don't drive tacks ... and if there is an improvement it's slight.

I hope this helps.
 
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the expander button button measured just over .219, I ordered some boat tails and will see if that resolves the issue, if it is still not working I will start messing with the dies.
I bet your seater die is not aligning the bullets well enough. Either that or the die is too far down and you're applying excessive crimp. If you're not crimping, then it's bullet misalignment.

Where are you located? Close to Portland?
 
Are you trimming all your cases uniformly to spec after resizing? When seating your bullets, if one neck is longer than the neck you set your die to, the shoulder will deform.
What is your thinking on this as far as neck length? If he's not crimping, I'd be shocked a little longer neck would cause this.
 
1: replace expander ball. It's on the small size, RCBS replaced mine at .218" as out of spec and wore from burnt carbon wearing it down.

2: What Bullets are you seating? Flat base I assume. This means more caution.

3: You do NOT flare a rifle case mouth. No, no, no.

4: I'm guessing your seater die is down too far and you are trying to "crimp" and seat at the same time. Not all dies do this, yours probably doesn't and it's why you are crushing the shoulders. Raise the die a couple turns and then try to seat again using the bullet seating screw to dial it in. Let me know how that works.


Edit:

Now that I'm not typing on my mobile. About three years back I had the same issue with my .300BLK cases and a new Hornady die set. After crushing a dozen cases trying to find out how/why it was doing it and what I was not doing, I called Hornady. After a brief discussion with the guy on the phone, the solution was simple. The 'crimp' window was so narrow and it required exact trimmed cases with the proper bullet that had a cannalure, any case longer than acceptable or any bullet that didn't seat right to the crimp spot was crushing the case. The solution was simple: don't use the crimp and seat in the same operation.

I had the same issue with some .223 cases as you described but my problem was from a different die being seated too far down in the press. The powder expander for the Lee Pro drop was doing the same thing, turns out I had the powder drop screwed down too far in the press. 1 turn up, everything was fine, powder dropped perfectly and the cases still got charged. (no, it does not flare the case mouth, it's a misnomer for their rifle cases).



You aren't alone, there are also similar issues when running a charging die:
 
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You don't need to use an expander button at all.. you can use a Lyman M die to just allow the bullet to be seated without deformation instead, very often you must use a like die as when using plain base lead projectiles and the like.
 
You don't need to use an expander button at all.. you can use a Lyman M die to just allow the bullet to be seated without deformation instead, very often you must use a like die as when using plain base lead projectiles and the like.

Agreed on the lead projectiles, this is why the M-die exists.

I'm going to push back on Dyjital comment about flaring rifle case mouths. Sometimes, with jacketed-flat based bullets and certain lots of brass it IS necessary to flare rifle case mouths and this will not cause problems in any regard. This tiny bit of flare is removed during the seating process as the case is pushed up into the die, even if you don't crimp in a later step.

This statement assumes you are just flaring only a thousandth or so, so that the heel of the flat-based bullet will just sit entirely inside the case mouth. If the bullet is resting in any fashion on the case mouth you will have shearing on the base of the bullet. Typically this tiny bit of shearing will have no effect on performance, unless you are shooting bench rest quality rifles and components (which is why some bench rest shooters do flare the case mouth as I'm suggesting). I should also add that you would need to have the skills necessary to shoot bench rest to note a difference. Few shooters do. I for one do not and I'm a classified rifle competitor of many years.

Have you ever noticed "brass dust" building up on the press while loading? Many times these are tiny flecks of jacket material sheared off the base of the bullet while seating. Sometimes they are tiny flecks of "wire burr" coming off of a poorly chambered case mouth, and there are other reasons. But when seating flat based bullets this "dust" is most likely coming from the heel of the bullet.

But ...

In this case you are buckling cases and you have stated you are not crimping while seating. So, if the suggestion of backing off the seating die (to be sure the crimp shoulder in the die is not at play) does not solve the problem and your expander ball is the correct size (which while on the small side is within spec) there is really nothing else that will cause this other than the brass lot / die combo. So give the case mouth a touch of flare with an M-die or other tool and I'll bet your problem will disappear.

I hope this helps!
 
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You know @DLS, like my wife said... "we can't both be right, so one of us wrong and it isn't me..."

lol. I'm sure there are reasons with cast projectiles to help it seat but I don't shoot cast projectiles in a .223 hence the need to flare isn't there.

Maybe I should have prefaced my statement above?

:s0005::s0104:
 
I had same problem using RCBS dies for 223 and using flat based bullits.
RCBS sent me a new expander ball at no charge....no improvement.

I switched to boat tails and have not had issue since.
 
I have RCBS dies and have loaded lots and lots of flat base bullets with out problems. Me and about a million + others. That company makes good products and they stand behind them.

The first thing i would have done is call the RCBS tech line and talk to a professional.

Chamfer your neck a touch more than you would with boat tails. Don't use overly work hardened brass that has been fired to many times.

Set it up as per the manufactures instructions.

Try a different brand of brass. Try a different type of bullet.

All easy stuff.
 
I have RCBS dies and have loaded lots and lots of flat base bullets with out problems. Me and about a million + others. That company makes good products and they stand behind them.

The first thing i would have done is call the RCBS tech line and talk to a professional.

Chamfer your neck a touch more than you would with boat tails. Don't use overly work hardened brass that has been fired to many times.

Set it up as per the manufactures instructions.

Try a different brand of brass. Try a different type of bullet.

All easy stuff.

All very easy stuff to do. IF you know how, and you would be surprised at how many really don't. I too would have contacted RCBS. They will get the OP straightened out. To me, it sounds like a bad die or it's set up improperly. Dies need to be adjusted and set up properly for function and for best accuracy.
 
One and done.

 
One and done.

You can't use those for compressed loads so it'd suck for crushing loads.
:s0056:
 

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