Shoulder bump problem or no problem?

[Shane Lindsey]

If it will chamber but just tight, maybe make 5 rounds at the low end and see if it still does it. maybe they just aren't fireformed enough for this chamber and the energy expended itself in blowing out the shoulder.

Did you use low end FF loads? I have a 338 Sherman and it takes 280ai brass so not sure about the Mega and how the brass starts. I do have a fine line between soft tension and waaaaay to easy when setting my dies. Enough that is crushes the shoulders to be easy. I just live with a little more tnesion than I prefer.

 

[lancetkenyon]

I have not read this entire thread. So this might have been covered already.

If you are necking up brass from 30 to 33, and it is anything other than Rem or Win brass, you are probably getting a donut at the shoulder to neck junction. When you are sizing it, if using an expander ball or an expanding mandrel after, you are pushing that donut to the outside, causing a parger diameter at the base of the neck. Might barely be perceptable, but it is there.

Almost all brass manufacturers use thicker material at the shoulder than the neck. When you neck up, you are oushing some of that material that used to be shoulder into the base of the neck material now.

You need to turn the necks and eliminate that donut.

I necked up some Rem brass from 7RM to .338WM brass. No problem. Then did the same with Nosler brass, and had. Big donut. Had to turn necks.

That is also why the 6SLR/6.5SLR Recommend using Rem or Win brass as a no-turn option. You are pushing the neck down into the shoulder material.

 

[Shane Lindsey]

I have not read this entire thread. So this might have been covered already.

If you are necking up brass from 30 to 33, and it is anything other than Rem or Win brass, you are probably getting a donut at the shoulder to neck junction. When you are sizing it, if using an expander ball or an expanding mandrel after, you are pushing that donut to the outside, causing a parger diameter at the base of the neck. Might barely be perceptable, but it is there.

Almost all brass manufacturers use thicker material at the shoulder than the neck. When you neck up, you are oushing some of that material that used to be shoulder into the base of the neck material now.

You need to turn the necks and eliminate that donut.

I necked up some Rem brass from 7RM to .338WM brass. No problem. Then did the same with Nosler brass, and had. Big donut. Had to turn necks.

That is also why the 6SLR/6.5SLR Recommend using Rem or Win brass as a no-turn option. You are pushing the neck down into the shoulder material.

Would/do you neck turn prior to fireforming or after?
Size fireformed brass and then neck turn.

I have never turned necks.

 

[Tidesloe]

I have not read this entire thread. So this might have been covered already.

If you are necking up brass from 30 to 33, and it is anything other than Rem or Win brass, you are probably getting a donut at the shoulder to neck junction. When you are sizing it, if using an expander ball or an expanding mandrel after, you are pushing that donut to the outside, causing a parger diameter at the base of the neck. Might barely be perceptable, but it is there.

Almost all brass manufacturers use thicker material at the shoulder than the neck. When you neck up, you are oushing some of that material that used to be shoulder into the base of the neck material now.

You need to turn the necks and eliminate that donut.

I necked up some Rem brass from 7RM to .338WM brass. No problem. Then did the same with Nosler brass, and had. Big donut. Had to turn necks.

That is also why the 6SLR/6.5SLR Recommend using Rem or Win brass as a no-turn option. You are pushing the neck down into the shoulder material.

I suppose that's still a possibility, and we have talked about that on this thread. I'm only using an expander mandrel to expand the neck. After that a bushing no expander ball or mandrel. I sharpied that area and chambered multiple times and can't see any indication of contact, even with a magnifying class.

 

[Tidesloe]

I don't suppose it would hurt to turn the neck on a piece, just to see if it makes any difference at all. I'm gonna have to fire a few more rounds and start over. I talked with Zermatt this morning and they gave some helpful info, and cleared a couple of things up.

 

[Tidesloe]

Would/do you neck turn prior to fireforming or after?
Size fireformed brass and then neck turn.

I have never turned necks.

I haven't either. I've never needed to

 

[lancetkenyon]

I suppose that's still a possibility, and we have talked about that on this thread. I'm only using an expander mandrel to expand the neck. After that a bushing no expander ball or mandrel. I sharpied that area and chambered multiple times and can't see any indication of contact, even with a magnifying class.

If you are expanding first, then running through a bushing die with no expander ball or mandrel afrer, you are pushing the donut inside. Then the bullet would be pushing it back out if seated below this point.

 

[lancetkenyon]

Would/do you neck turn prior to fireforming or after?
Size fireformed brass and then neck turn.

I have never turned necks.

Depends on the cartridge.

In an Ackley Imp 40° or the like, it depends on if the bullet pushes out that donut to the outside and will allow the round to chamber or not.

If in an SLR type cartridge, I would do it before FF.

 

[Driftin]

I usually turn the necks as my last stage before loading. I assume the bullet pushes out the donut like Lancekenyon suggested.

 

[Tidesloe]

If you are expanding first, then running through a bushing die with no expander ball or mandrel afrer, you are pushing the donut inside. Then the bullet would be pushing it back out if seated below this point.

My bullet bearing surface is not more than halfway in the neck on my fireforming loads

 

[lancetkenyon]

My bullet bearing surface is not more than halfway in the neck on my fireforming loads

Then technically, a donut inside might not be an issue.

 

[HandgunHTR]

I have not read this entire thread. So this might have been covered already.

If you are necking up brass from 30 to 33, and it is anything other than Rem or Win brass, you are probably getting a donut at the shoulder to neck junction. When you are sizing it, if using an expander ball or an expanding mandrel after, you are pushing that donut to the outside, causing a parger diameter at the base of the neck. Might barely be perceptable, but it is there.

Almost all brass manufacturers use thicker material at the shoulder than the neck. When you neck up, you are oushing some of that material that used to be shoulder into the base of the neck material now.

You need to turn the necks and eliminate that donut.

I necked up some Rem brass from 7RM to .338WM brass. No problem. Then did the same with Nosler brass, and had. Big donut. Had to turn necks.

That is also why the 6SLR/6.5SLR Recommend using Rem or Win brass as a no-turn option. You are pushing the neck down into the shoulder material.

Just another data point here, I am using the same type of brass and dies as the OP is in the same chambering (338 Sherman Mega). I used the same method to neck mine up. The only differences I can see is that I used a pretty standard load to FF and I am using a different action and barrel. I don't have any issue with donuts.

OP, the last thing I can recommend is stepping up your fireforming loads. I used a middle of the road book charge for a .338 WM and pushed the bullet out so that it had 0.010" of jam. Got great results. But, I have been fireforming brass for a while now as I really like shooting the wildcats out of single shot handguns.

 

[Tac-O]

I do think that the method of fireforming has an impact on donut creation.

I think I've seen Alex Wheeler talk about this on accurate shooter forum but can't remember exactly what he said.

My thinking is that if you don't fireform an improved case with a slight crush fit (Ackley is supposed to be a 0.004 interference fit from base to neck/shoulder junction) then the case will move backwards to the bolt face on ignition and be more likely to move the shoulder marerial forward into the neck. If you do have the 0.004 crush fit, the case can't move and when the sidewalls and shoulder are blown outward the material will be pulled out of the neck since the web area is much harder and would resist moving moreso than the neck. The evidence for this happening is having a shorter neck and case oal after fireforming.

The mega has the neck/shoulder junction moved forward from virgin though, right? That's why you guys are jamming into the lands for fireforming?

 

[Tidesloe]

I do think that the method of fireforming has an impact on donut creation.

I think I've seen Alex Wheeler talk about this on accurate shooter forum but can't remember exactly what he said.

My thinking is that if you don't fireform an improved case with a slight crush fit (Ackley is supposed to be a 0.004 interference fit from base to neck/shoulder junction) then the case will move backwards to the bolt face on ignition and be more likely to move the shoulder marerial forward into the neck. If you do have the 0.004 crush fit, the case can't move and when the sidewalls and shoulder are blown outward the material will be pulled out of the neck since the web area is much harder and would resist moving moreso than the neck. The evidence for this happening is having a shorter neck and case oal after fireforming.

The mega has the neck/shoulder junction moved forward from virgin though, right? That's why you guys are jamming into the lands for fireforming?

I don't know, but it seems like that junction would be shorter after necking up. I could very easily be wrong on that though. Yes, that's why we jam so the case can't move backwards.
Here's how I fireformed these 5 rounds. I took a low 338 WM load with a similar bullet, and loaded 5 going up in 1 gr increments, until I see pressure, then back off a grain. I'm jammed .020, and lightly sprayed Hornady one shot case lube on it and fired. The should keep it from going backwards, and more easily move the brass forward to the shoulder. I talked to Zermatt today, after I realized I had movement of my bolt head on a spring. They said the bolt head is fixed solid and won't move with an assembled bolt and a trigger installed.
I think I'll go start over, and pull the firing pin, pull the spring between bolt body, and bolt head and find my distance to lands again. This measurement should change now, fire 5 more and see what I got. I'll test the fired rounds as I'm sizing and bumping in the same condition. This should be pretty close to how a standard bolt would be. Test a dummy in the chamber, load a few and shoot. If I'm still confused as to what I'm seeing, then maybe, just maybe there is a donut issue. I won't be able to fire any more until next weekend.
How you coming on yours? Are you gonna turn some necks?