Problem with belt cartridge

[Bart B]

Derrick, use a magnifying glass to look at a fired belted case body right in front of the belt. You'll see a ridge/step of brass a few thousandths wide and high. That's what I'm talking about.

It interferes with the chamber at that point.

If it's not the case you don't understand about, I'll explain more about the die.

 

[Mada]

I see what you're saying now. From the belt theres a little slope, Kinda like that took the case and crimped it inward to fit the belt onto the case... Thats were my case DOES grow fatter and therefore the die wont fit.

Is this because the case as formed itself to the size of my chamber?

 

[Bart B]

I see what you're saying now. From the belt theres a little slope, Kinda like that took the case and crimped it inward to fit the belt onto the case... Thats were my case DOES grow fatter and therefore the die wont fit.

Is this because the case as formed itself to the size of my chamber?

Yes, that's what's happening.

When the firing pin strikes the primer, the case gets driven hard forward and stops someplace....

If a new case is fired, it stops when the front of the belt contacts the headspace ridge in the chamber, then as pressure builds and the case expands, the case head gets pushed back against the bolt face leaving a small gap between the front of the belt and where it headspaces in the chamber. Body brass expands in this tiny area making the step.

If a previously fired case is used, it may stop when the shoulder impacts the chamber shoulder if the shoulder's not set back when sized. So there's already a space between the front of the belt and the chamber headspace ridge so even more body expansion can happen. If the fired case shoulder's set back too far, that step/ridge will interfere with the chamber at that point and the back of the case won't be at the same place for each shot.

That darned ridge interfering with the chamber at different places around the case causes the barrel to whip differently while the bullet's going down the bore. The end result is the muzzle axis ain't always pointing at the same place relative to the aiming point on the target for each shot.

All this is why top competitive shooters using belted cases have always got best accuracy with new cases or cases double sized to get rid of that step infront of the belt. A recent 1000 yard benchrest record was set using brand new, unfired .300 Wby. Mag. cases. My own 1000-yard magnum when last tested, shot two, 15-shot groups at 1000 of about 6 inches; one group with new cases and the other with double-sized ones. I've never put 15 or more rounds in under 15 inches at 1000 using neck only, partial full length sizing or just a conventional full length sizing die by itself.

 

[Mada]

I see what you're saying, but I'm not trying to buy new brass or I'd just buy factory ammo. If it helps, the cartridges I'm using is for one rifle only. What can I do to potentially get the best accuracy out of what I have?

What makes sense to me to do is neck sizing since the brass is already formed to my action.

Correct me if I'm wrong, please.

 

[Bart B]

What can I do to potentially get the best accuracy out of what I have?

Buy a Redding or RCBS full length sizing die that uses bushings to set the shoulder back and with a diameter about 3 thousandths smaller than a loaded round's neck diameter. Buy an RCBS Precision Mic for your cartridge to use for measuring how far you set the fired case shoulder back when full length sizing; set the shoulder back only 2 to 3 thousandths. This will be your best single die purchase.

The only thing better is just to add a colled die from Innovation mentioned earlier. This will improve accuracy by getting rid of that step/ridge in front of the belt on resized cases.

 

[Tikkamike]

Here is your problem! My dad read this and instantly knew the problem and after he said it I knew he was right. Your decapping pin is down too far. the sizing button is hitting the other side of your primer pocket... pull loosen your stem and back it all the way out. and run your brass throught the die. should go in no problem. then take a piece of fired brass with the primer still and push it all the way in the die and leave the handle on your press in the down position. screw your depriming pin down until you feel it make contact. then pull the handle of the press back up and screw the pin in 2-3 turns and see if the primer comes out. if not give it a half turn and try again. keep going till it deprimes. then tighten the stem back up so it doesnt move. you should be good to go from there and no need to buy any dies.

 

[Mada]

Here is your problem! My dad read this and instantly knew the problem and after he said it I knew he was right. Your decapping pin is down too far. the sizing button is hitting the other side of your primer pocket... pull loosen your stem and back it all the way out. and run your brass throught the die. should go in no problem. then take a piece of fired brass with the primer still and push it all the way in the die and leave the handle on your press in the down position. screw your depriming pin down until you feel it make contact. then pull the handle of the press back up and screw the pin in 2-3 turns and see if the primer comes out. if not give it a half turn and try again. keep going till it deprimes. then tighten the stem back up so it doesnt move. you should be good to go from there and no need to buy any dies.

This is what I did first. I thought this was solving my issue until i realized that all I'm doing is pushing the primer out, but I'm not resizing the neck/shoulder/ and case bulge.

 

[jimbires]

Mada , did you get your case lube ? did you get the case to go in the die completely ? just wondering how your doing with this . Jim

 

[Mada]

Mada , did you get your case lube ? did you get the case to go in the die completely ? just wondering how your doing with this . Jim

I ordered lube and it was supposed to come friday, but its not here until monday

 

[Loner]

This is what I did first. I thought this was solving my issue until i realized that all I'm doing is pushing the primer out, but I'm not resizing the neck/shoulder/ and case bulge.

The decapper and neck ball position have nothing to do with the case sizing and shoulder
bump. I'm not sure if you understood his post correctly?

 

[Mada]

I understood

 

[Mada]

Woo, Finally got to reload some ammo. I used extra lube and it slid in nicely. Going to try and shoot now

Would C.O.A.L. differ by .003 +/- be a great deal to my accuracy ?

 

[jimbires]

Woo, Finally got to reload some ammo. I used extra lube and it slid in nicely. Going to try and shoot now

Would C.O.A.L. differ by .003 +/- be a great deal to my accuracy ?

FANTASTIC !! . it's funny what a little lube will do .

I'm guessing you are measuring of the tip of the bullet ? if so +/- .003 is nothing to worry about . Jim

 

[Mada]

yea its from the tip on a soft point BT bullet, guessing because its SP its not an accurate read anyways.