300 Win Mag reloading question

[Alibiiv]

I understand, BUT, an unfired BELTED case is completely unsupported in a FL die, so, ANY eccentricity in the body, WILL transmit into the neck. This is another reason to own Neck only dies.
Even if you don't go to the expense and level that I do with precisely honed necks and custom expanders, at least you can size the neck (Redding Deluxe Die Sets are the best) and keep everything concentric.
I have been shooting belted cases in competition for 30 years, I understand their inherent drawbacks, figured out what works and what doesn't, the BIGGEST killer is excessive brass movement ANYWHERE on the case.
Many believe that the belt gets sized, it doesn't, many believe the belt stops a case being sized because it doesn't enter the die fully, it's not meant to, never was. Many believe if the expansion line is tight in the chamber they need to size further down the case, it doesn't, all this does is increase headspace and causes case head separations…
You need to understand HOW the case works when headspace is off the belt, the belt holds ALL forward AND rearward movement, the shoulder EXPANDS to fill the void and the belt keeps the case head against the bolt face. After which the case is PARTIALLY formed to the chamber, often .002"-.003" SHORT of chamber dimension. If you size at this point, you WILL BE inducing .004"-.005" headspace on the shoulder to base datum, THIS is what causes case head separations in belted cases. Period.
My custom 264WM, both chamber and throat, are based on the same principles of the A191 chamber dimension. This is one of the most accurate rounds I have ever developed personally, it is in the .2's and I have been using it for F-class this season with excellent results.
Brass movement, or lack thereof, is what is required for precision.

As @Mikecr says, more clearance is NEVER the solution.
Long winded, I know, but this needs understanding.

Cheers.

Would you please define "eccentricity" for me in this post. From my perspective, "if" the die is reamed in "ONE" step, with the same reamer, not in two steps with two reamers, how can the neck not be concentric with the body of the die? I have gotten new brass, that after full length resizing, trimming to length and then turning the necks have found that the "brass" on the neck was not concentric when it was manufactured, but never after the brass was FL resized the second resizing. Also not all separations are caused by resizing, some causes for separations are due to someone trying to take their cartridges to the next level of magnum and putting too much pressure on the case because the maxed out or went over maximum loads. Many reloaders oftentimes get into trouble because they are sacrificing accuracy for velocity! I read this all of the time on many of the posts in this forum. FPS trumps all other efforts of the reloading process and all safety and all manuals are thrown into the wind.

 

[marc357]

Absolute NONSENSE! Stop talking BS.
You have caused the issue, not the cartridge, YOU.
the brass doesn't stretch, it expands and fills the chamber.
Ever seen a case sized and loaded 10 times with no stretching…
Here's one.
I don't see any stretching, do you?

Do you think I can't measure?

I've been loading. 300WM for 25 years now, and produced ammo that shoots better than many people believe is possible- dang, you'd think I'd have learnt to measure by now.

If the Base To Datum measurement of my fired brass is .014" longer than the Base To Datum measurement of my factory round, what do you reckon happened?

How did the shoulder move forward .014 without stretching the brass?

Explain it with small words, 'cause golly, I must be ret@rd3d.

 

[Clem Bronkoski]

I believe you two might be getting involved in what words you're using. Please calm down. No sense getting heated up over this. I believe expansion and stretching are almost one in the same. Upon firing ALL brass expands to fit and seal the chamber then retracts slightly after cooling which allows for extraction.
Simple physics would state there is only so much brass in the case so if its initially too short for the chamber at the shoulder, upon firing, the entire case expands to fill the chamber. Sooooo if the shoulder is moved forward .XXXX" where does that excess material come from? Truth is the brass stretches along the body as the shoulder moves forward. Think of a balloon in a jar. When relaxed its fairly thick but blow it up inside the jar and the material gets thinner as it fills the jar.
Brass does flow forward a little with each firing. Especially cartridges like the 220 swift, 243 and similar. That's why after a couple firings, the cases mouths need to be trimmed. The brass does expand then retracts in the chamber but it also stretches (flows forward) at the case mouth. Some cases, because of their design and the brass composition itself, flow more than others.

 

[MagnumManiac]

How did the shoulder move forward .014 without stretching the brass?

The brass does NOT STRETCH. PERIOD.
I've been loading, forming and inventing cases much longer than you.
I successfully fireform 375H&H brass into MANY other cartridges, none of it stretches, what ACTUALLY happens with ALL brass that is blown out to a larger chamber is it SHRINKS as the brass is blown out from the neck, even 300WM brass. The brass expanding to fill the void comes from the THINNEST part of the case, the neck and the shoulder.
Anyway, I'm not here to argue, but I'm not here to sit back and read BS as if it's gospel. You have/are just repeating what you've HEARD over the years and believe it's true. It isn't.
Just another myth invented by gun rag writers for cash for comments.

 

[MagnumManiac]

Go watch how they make round metal containers for many different applications. They build them square, then using hydraulic pressure, it goes into a sphere due to the pressure.
Same principal applies, and the dimensions of the finished sphere are always smaller…

Cheers.

 

[marc357]

Anyway, I'm not here to argue

I think you've demonstrated the opposite.
Have a Super day.

 

[cajun]

I think you've demonstrated the opposite.
Have a Super day.

This same person goes off every time this comes up. Call it stretch or what you want. I do know that on the first firing of belted brass the shoulder will move forward .015-.020. If you push the shoulder back this much and head space off the belt the case will separate ahead of the belt in a few firings. This is fact. Call it what you want. But the shiny ring you see show up is a thinning of the brass. Why is it thinning?

 

[MagnumManiac]

I think you've demonstrated the opposite.
Have a Super day.

Whatever…
I wasn't arguing, pointing you to correctness and facts.
You have a Stupendous day