Neck sizing and overpressure signs in 338LM

[bigsampson]

I know I read something on this before, but my search foo must not be up to snuff.

I have a 338 LM, If I full lenght resize all is well. If I neck resize with the same loads, I get a very sticky bolt and a bit of a flat primer and some primer flow around the firing pin.

I neck resize for all my rifles and never had this issue before and I am a bit confused.
Needless to say, the neck sizer is in the closet for now.

Any ideas or suggestions certainly appreciated.

 

[Mikecr]

Your pressure is too high, and you still need to bump shoulders.

 

[bigsampson]

Well,
I know the pressure is too high, hence the title of the thread, "Re: Neck sizing and overpressure signs in 338LM"

I could understand having to bump the shoulder back after two or three reloads, but after one firing? The rounds chamber fine, maybe a little more force than a full length resize. And I agree that bumping the shoulder is required. That is why I have put the neck sizer away.

Is this something that is more common in big cartridges like 338 LM and the RUMs? Have never seen it in 308, 223, 30-30, 30-30AI, 300WM or any of the other rounds I load for. Or is it because my chamber is on the tight side? I guess I am trying to say that I don't understand the dynamic here. The round is a safe, well under max load that fits in the chamber. The neck has been resized and the shoulder is within enough tolerance that it fits the chamber. Yet it is developing more pressure than a full length case of the same load.

I figured on a factory Rem 700 action and barrel neck sizing would enhance accuracy. But on this gun I guess not.

 

[SBruce]

I've never run into this with smaller calibers, but I've always done my load development with NS cases. As you said, usually only need to FL every few fireings?

Have you by chance tried backing the charge down just a hair? I mean on the NS rounds. If there's more pressure, I'd assume they're faster too.

I'd be curious to know what the velocity difference between the NS and FL rounds are with same powder charge.

 

[RockZ]

The dimensions of the NS cases are much closer to the chamber size.
So they fit tighter and expand to chamber size sooner after shooting.
They expand to fit the chamber but then shrink a little.
But to a dimension that is larger and tighter than your fulllength cases.
Basically there is less room to expand with the NS cases.
Making it show pressure.

 

[Mikecr]

His pressure problem is not at all related to neck sizing.
He needs to back off the powder and/or lands.

If he full length sizes, his case capacity will drop and pressures will go up even further, unless he backs off on the powder.
Could just be a fast lot of powder..

 

[bigsampson]

This issue IS related directly to neck sizing.
The amount of case capacity lost from neck to full length resizing is miniscule.

The loads I am using are 2 grains or more under the lowest max published, are very standard 338 LM loads and function perfectly fine in full length resized cases.

In several cases, dealing with 250 grain bullets, the load is even lower than two grains under max. I see this issue when reloading 300 grain SMKs and several other 250 grain bullets.

Not talking about unusual powder either. Retumbo, the "go to" 338 LM powder.

OAL isn't the problem either, not even close to pushing this.

I think Rockz is probably on target.

 

[RockZ]

mike
He says when he full length resizes, all is fine.
That's why I figured the case is tight going in and even tighter coming out.
I too believe he could back it off a bit.
But if it was overpresure alot wouldn't all roundsbe
a problem

 

[Mikecr]

He said right up front that he had a pressure problem. Well neck sizing doesn't cause pressure problems. If what he really has is an extraction problem, then I agree that body sizing might help.
But then, what REALLY was the question?
Was it 'Do I still need body sizing -combined with neck sizing, for my load'?
Answer, YES

 

[RockZ]

I agree.
That is what I was saying.
The problem with neck sizing is he needed the body sized and maybe the shoulder pushed back.
No need to get riled up
LOL

 

[Boss Hoss]

Well,
I know the pressure is too high, hence the title of the thread, "Re: Neck sizing and overpressure signs in 338LM"

I could understand having to bump the shoulder back after two or three reloads, but after one firing? The rounds chamber fine, maybe a little more force than a full length resize. And I agree that bumping the shoulder is required. That is why I have put the neck sizer away.

Is this something that is more common in big cartridges like 338 LM and the RUMs? Have never seen it in 308, 223, 30-30, 30-30AI, 300WM or any of the other rounds I load for. Or is it because my chamber is on the tight side? I guess I am trying to say that I don't understand the dynamic here. The round is a safe, well under max load that fits in the chamber. The neck has been resized and the shoulder is within enough tolerance that it fits the chamber. Yet it is developing more pressure than a full length case of the same load.

I figured on a factory Rem 700 action and barrel neck sizing would enhance accuracy. But on this gun I guess not.

Every BR shooter (some HOF) I know myself included FL size. Have several 338 LM Imp's and even with FL sizing proper lubrication is the key so pay close attention to the process.

 

[Mikecr]

This issue IS related directly to neck sizing

You said yourself that neck sizing has never been an issue for you. Now all the sudden neck sizing is bad?
You've conceded that your pressure is too high. In a SINGLE firing(I assume you mean first firing), you get flatened primers and sticky bolt lift. Right?
YOUR PRESSURE IS TOO HIGH,, atleast for neck only sizing.
If you desired to do neck sizing only, then why have you gone so high in pressure as to cause case body changes?
What did you think would be the results of this?

The loads I am using are 2 grains or more under the lowest max published

Not talking about unusual powder either. Retumbo, the "go to" 338 LM powder

'Published' and 'popular' are with test barrels and chambers and powder lots that are NOT yours.

Seriously, think about what you're doing...
You know very well that you can scrape that yeilded brass aside, and work up a lower pressure load that can be managed without ever FL sizing. Right?
What's the problem?

 

[bigsampson]

Mike,
Please stop.
Your additions are totally worthless.


I very clearly said that I had stopped neck resizing due to the signs of pressure. And was posting trying to understand why a load (and similar loads) of 90 grains of Retumbo, which is actually 4 grains less than the Hodgeden max rec, shoots great with absoloutly no signs of pressure when the cases are full length resized and are showing signs of too much pressure when neck resized.

I never said neck resizing is bad, or that I was going to stop in the other calibers I normally use it in, just that I had never experienced this issue before and wanted to understand the dynamics on why it might be happening in this gun and/or this caliber.

You make too many assumptions and preach too much.
If you don't know why this occurs, leave it alone.

 

[SBruce]

Do you have, or have access to a chronograph?

If so, posting the results of NS vs FL sized loads (everything else being precisely identical) could maybe shed some light on this dark subject.