Shoulder bump problem or no problem?

[Tac-O]

I'll first be attempting to set my mandrel to only expand the portion of the neck that I seat the bullet into, leaving the donut inside. If that works, I'll do that as long as possible.

If it doesn't, I may look into getting a cheap neck turner even though I don't want to.

 

[Tidesloe]

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.

Thanks! I'm thinking there are nuances to this type of action. The bolt is different, and I've never worked with one. Otherwise I'm still not sure. I also started with a lower, but not bottom 338 WM load, and loaded 5 up in 1 grain increments. I did see only with a magnifying glass a slight ejector mark, on my 3rd round. I backed the other 2 off 1 gr, and it seems that worked well.

 

[Tidesloe]

I'll first be attempting to set my mandrel to only expand the portion of the neck that I seat the bullet into, leaving the donut inside. If that works, I'll do that as long as possible.

If it doesn't, I may look into getting a cheap neck turner even though I don't want to.

Hahaha, I hear you man. I've got one, had it for years but have never needed to use it. Who knows, maybe I end up using it on this one. Good luck and let us know how it goes.

 

[Roughrice]

I have several Origin actions in SAUM and Standard long and short action configurations.
I haven't had problems with either of them in measuring chambers or loading yet.
Don't have a 338 Mega though…and I am no gunsmith.

I would put money though that the problem has already been mentioned somewhere in this thread.

 

[Tidesloe]

I have several Origin actions in SAUM and Standard long and short action configurations.
I haven't had problems with either of them in measuring chambers or loading yet.
Don't have a 338 Mega though…and I am no gunsmith.

I would put money though that the problem has already been mentioned somewhere in this thread.

Yep, there's probably no doubt about that. I'm just doing what I can for now, and I'll be looking at the other possibilities also. Good to hear you have no issues with Origin actions. Some of this might be overthinking it also. I can't discount that either.

 

[Roughrice]

No doubt!!
I think from your experienced investigation and many of these guys opinions…the problem should have been come across somewhere.
It sounds like a tough one but , like you already know, keep the obvious at hand.

 

[Roughrice]

I'd go back to the beginning with no shoulder contact on sharpied case but bolt would still not close until you bumped .008 or so.

 

[Tidesloe]

No doubt!!
I think from your experienced investigation and many of these guys opinions…the problem should have been come across somewhere.
It sounds like a tough one but , like you already know, keep the obvious at

I'd go back to the beginning with no shoulder contact on sharpied case but bolt would still not close until you bumped .008 or so.

It will close, but with resistance and clickers opening the bolt. Somehow maybe I am dealing with a donut. Stiff bolt closing and opening all the way back to .006 that I came up with last night. That's the same amount of movement of the bolt head in and out that I measured last night. That's what I keep trying to wrap my mind around. There is a spring between the bolt head and bolt body keeping it out, but it's not a strong spring. Can't imagine it would cause that much stiffness.
That's with no firing pin installed

 

[Roughrice]

You can push the back of your bolt with your thumb and compress the washer.

I'm doubtful that a donut will cause clickers.

I try to keep symptoms simple to eliminate one at a time.

This is a wonderful place to get information for such problems.

Without seeing or measuring, That web area and headspace measurement is where I've EVER had clickers happen and what I'd focus on first.

 

[Roughrice]

Did you fire a second round of fireforming the same brass?
That should give you a good idea of your chamber length measurement and case web diameter.

 

[Roughrice]

It will close, but with resistance and clickers opening the bolt. Somehow maybe I am dealing with a donut. Stiff bolt closing and opening all the way back to .006 that I came up with last night. That's the same amount of movement of the bolt head in and out that I measured last night. That's what I keep trying to wrap my mind around. There is a spring between the bolt head and bolt body keeping it out, but it's not a strong spring. Can't imagine it would cause that much stiffness.
That's with no firing pin installed

I can barely feel a loaded round resistance on bolt closing. I can tell but it's a smooth steady close and opening feels the same.
The closing stiffness on your bolt may be that donut that you and others spoke of. I would very well measure everywhere on your second firing brass compared to the new brass that closes without problem to determine your max and minimum chamber dimensions.
As said before... bumping the shoulder .008 back from a fired case measurement if not needed is destined for case head separation.

 

[Tidesloe]

Did you fire a second round of fireforming the same brass?
That should give you a good idea of your chamber length measurement and case web diameter.

No, I've only fired 5 rounds. I'll have to fire a few more next weekend. The web and 200 line is where I began with all this but my measurements, and what the reamer designer told me the chamber measurement is I kind of discounted it. It should be .555, all my measurements have not been more than .553. I might go back to it, and donuts and basically start all over again.
What part of Louisiana are you from?

 

[Roughrice]

Central Louisiana. South of Alexandria. I'm a farmer and have a shooting range set up with steel to 1330 yards then jump to 1 mile.
So... I shoot every weekend unless its raining. It's my expensive hobby now that the kids are grown and gone! LOL!

 

[Tidesloe]

Alright. I lived in Lake Charles many years ago. Most of my family is all from that SW part of the state