Expander not pushing out donut

[Kyle Schultz]

I have donuts in my 3X fired 6.5x47 Lapua brass. Even though my chamber is set up for no turn neck, I reasoned it wouldn't hurt to run the necks over an expander die and outside neck turn the donut out. I'm using K&M tools with the non-cutting pilot mandrel.

Even after turning, the donut is still present. A bullet will "bottom out" when I slide it in the case by hand. If I put the turned case back into the press holding the expander die, I can still feel a point of slight resistance prior to the press fully cycling. If I remove the die from the press the donut is still prevalent enough to prevent me from fully sliding the neck over the mandrel by hand.

I don't understand why the mandrel isn't pushing the donut out to be outside trimmed. Do you think perhaps the brass has become work hardened and needs to be annealed before expanding and turning? I was going to anneal after neck turning.

The only other alternative, which isn't necessarily the worst solution, is to seat the bullet above the donut. That's assuming, of course, I have sufficient free bore in the chamber.

Any advice is welcomed. Thanks!

 

[Patch700]

If you are absolutely certain that you are running the necks all the way up onto the mandrel (not short stroking it or leaving the mandrel die too high up in the press) then you may have to get an oversized mandrel ... Having said that be sure to also get an oversized and matched mandrel for your neck turner so as to not wind up with a sloppy fit to the turner once they have been expanded.

Call K&M or have a competent machinist cut you a couple new mandrels , one for the die and one for the cutter.

Good luck

 

[ShootDots]

Good Afternoon Kyle. I had the EXACT same phenomenon happen with the NEW Norma .284 brass. Mine are neck turned to 12K neck wall thickness. After 1 firing, I could feel the doughnut begin to form. At firing #3, I could not get the mandrel past the doughnut. So I purchased a cutting mandrel from K&M.. I started cutting out all the doughnuts. That not only has worked, the doughnuts have never returned! Do not ask me WHY they have not>>>I will just report>>you decide.

I believe you may end up doing that very thing. It is time consuming and you will need "turning mandrel lube" however, the cost is only time spent!

 

[Mozella]

..... snip............... Do you think perhaps the brass has become work hardened and needs to be annealed before expanding and turning? I was going to anneal after neck turning.......... snip........... Any advice is welcomed. Thanks!

That's my first thought. There's one quick way to find out; anneal a few cases, expand them again, and see what happens.

 

[bobinpa]

..... snip............... Do you think perhaps the brass has become work hardened and needs to be annealed before expanding and turning? I was going to anneal after neck turning.......... snip........... Any advice is welcomed. Thanks!

That's my first thought. There's one quick way to find out; anneal a few cases, expand them again, and see what happens.

+1, and maybe try pausing for a second while the expander is in the neck to prevent any spring back.

 

[Joe R]

ShootDots

Good Afternoon Kyle. I had the EXACT same phenomenon happen with the NEW Norma .284 brass. Mine are neck turned to 12K neck wall thickness. After 1 firing, I could feel the doughnut begin to form. At firing #3, I could not get the mandrel past the doughnut. So I purchased a cutting mandrel from K&M.. I started cutting out all the doughnuts. That not only has worked, the doughnuts have never returned! Do not ask me WHY they have not>>>I will just report>>you decide.

I believe you may end up doing that very thing. It is time consuming and you will need "turning mandrel lube" however, the cost is only time spent!

+1

I anneal after each firing, and I can see how that would prevent a doughnut from forming, but I fail to see how annealing is going to make the doughnut go away once it has developed. Here's the bottom line: now that you have it if you don't want it to interfere and cause some deleterious effect on you precision the only reasonable thing to do is what Ben suggested. Once you cut it out annealing may keep it from coming back.

Joe

 

[Mozella]

............ snip..............but I fail to see how annealing is going to make the doughnut go away once it has developed. ........ snip...........

.

It's not the annealing that does the job, per se. Annealing is simply part of the process.

The theory, my theory anyway, is that when the expander is put down the neck, the ID is uniform and the doughnut is on the outside ready to be cut off during the neck turning operation. However, the brass having been fired several times is work hardened to the point that when the expander is removed, the neck springs back so that the doughnut returns to the inside of the neck where it causes bullet seating problems.

Annealing the brass should, in theory, soften it to the point that when the expander is put down the neck, it uniforms the ID, forces the doughnut to the outside, but this time it stays there since the brass is soft enough to be permanently deformed. In other words, when the expander is removed, the brass doesn't spring back since is has been recently annealed. Now, it should be a simple matter to remove it during the subsequent neck turning procedure.

This may or may not work, but it's simple enough to find out.

 

['Freak]

I don’t know, just wondering if it help the mandrel to push more or all of the donut to the outside by sizing the neck down another thousandth or a couple thousandths smaller than where it has been prior to expanding?

 

[dannyjbiggs]

Sorry fellas...don't look for your expander ball or your mandrel to rid your cases of a doughnut. You will have to cut them out with an inside neck reamer, and then you will not get it all with that. You would think that using a good mandrel followed by outside neck turning would get rid of them, but by itself, it won't! It generally takes a combination of the two. However, the most simple thing to do is rig your freebore so that you seat bullets forward of the doughnut.

Dan

 

[savagedasher]

That is the reason many do use the expander ball. Larry

 

[asauer]

I've not had any luck getting rid of donuts in my 300 wsm. I turned necks when new, cut far up into the shoulder, and still got donuts. Re-turned necks to no avail. I even used an expander ball before running over the mandrel. I think the neck/shoulder junction is very stiff and resistant to force pushing the donut out.

The inside neck reamer may get most, but it will still be there. Unless you're going to bore out the entire length of the neck, there's no way to possibly get all of the donut out so I can't see the point in bothering. You'd have to have it sized to a more perfect fit than would really be possible and still fit in the neck without gouging... But even then you'd still have that .0001"+ of donut height in there...

 

[ShootDots]

I've not had any luck getting rid of donuts in my 300 wsm. I turned necks when new, cut far up into the shoulder, and still got donuts. Re-turned necks to no avail. I even used an expander ball before running over the mandrel. I think the neck/shoulder junction is very stiff and resistant to force pushing the donut out.

The inside neck reamer may get most, but it will still be there. Unless you're going to bore out the entire length of the neck, there's no way to possibly get all of the donut out so I can't see the point in bothering. You'd have to have it sized to a more perfect fit than would really be possible and still fit in the neck without gouging... But even then you'd still have that .0001"+ of donut height in there...

You are correct that you will still have a "slight Doughnut" after you cut them out. BUT I have done it and it is so slight that only on a few of my cases can I even feel a VERY, VERY slight dragging of the expander ball thru the doughnut area. It will not bother the Boattail portion of the bullet (if that is all that is extending down into the case) and have no effect on the bullet whatsoever. Making sure you have a freebore long enough to keep the bearing surface above the neck / shoulder junction, cut out those doughnuts and all will be well..

 

[Joe R]

dannyjbiggs said:

Sorry fellas...don't look for your expander ball or your mandrel to rid your cases of a doughnut. You will have to cut them out with an inside neck reamer, and then you will not get it all with that. You would think that using a good mandrel followed by outside neck turning would get rid of them, but by itself, it won't! It generally takes a combination of the two. However, the most simple thing to do is rig your freebore so that you seat bullets forward of the doughnut.

Dan

That's exactly why PT&G sells the Uni-Throater. See http://pacifictoolandgauge.com/throat-and-neck-reamers/5226-17-cal-uni-throater-kit.html

Joe

 

[mikecr]

No, this is an example why you should turn necks first(before firing), as part of initial preps.
With this, and rational body sizing, and no FL sizing of necks(ever), donuts are mitigated.

 

[fguffey]

Donuts, I form donuts when I form cases, that is before I fire them. I have chambers that will never form a measurable donut. To some the donut appears suddenly and without warning.

F. Guffey

 

[asauer]

I did turn necks before firing. And yes the final (and best) solution was to lengthen the throat so my bullets were not in that area anymore. Problem solved and I don't care that they exist.

Fguffey, yes mine formed because of excessive radius in the reamer at the neck/shoulder junction, and because I was using a standard full length die. I've not had this problem with anything else, except my 25-45 when using the new Norma "tac" 223 ammo. Fired it in my AR to harvest the brass. Upon necking up it forms a strange donut. Doesn't affect accuracy so I don't care.

 

[Kyle Schultz]

Appreciate all the feedback guys.

I have a call into K&M to hear what they say. But I'm not excited about trying to cut the donut out from inside the neck. In fact, I purposely ordered the non-cutting pilot so as to avoid all the helical scoring that inevitably occurs inside the case neck.

My gun is being rebarreled at the moment. Different reamer than previous. The new reamer has a 0.136" free bore. I've measured the base to ogive in several cases with all the various bullets I plan to shoot bottomed out against the donut. As long as the base to ogive measurement for my loaded rounds indicates that I'm above the donut, I'm not going to worry about it.

 

[jlow]

The thing to keep in mind is brass is not exactly soft ice cream, what I mean is it is not soft to the extend that pushing a donut on the inside is going to make it pop completely to the outside. A softer annealed neck will of course help but the way I visualize it, pushing it on the inside will only make the outside bulge a little with a significant amount of it staying put inside. Spring back of course will make this harder… If you have seen how metal respond when it is worked on, you will never believe that it will pop outside, it just does not work that way.