New territory---belted mags

[snowgetter1]

I recently picked up a 300 win mag TC Venture and I believe I will now do a 7mm-300 wm on a spare action for long range prairie dogs. My questions concern the belt. I have never messed with belted mags. I have read the cases will expand ahead of the belt requiring a special body die to resize. If so what is the best die for this? Could or would a 300wm small base die resize this area of the brass?
Thanks!
John

[jim_k]

There is a collet die available from Innovative Technologies at www.larrywillis.com for this purpose, and it works for all the standard belted magnums, which have the same SAAMI spec diameter just ahead of the belt (0.510").

[Bigbuckdn]

I never worried about it till I had two cases split right there one in an encore and it was like mini blow touch comming out of the action scorched the action and took fish ff the scope

[Zero333]

Don't worry about larry wills die unless you're using once fired brass from another rifle that will not fit into yours.


After the initial firing the headspace moves to the shoulder not unlike non-belted cartridges so don't sweat it and load it like any other. Just get yourself the Hornady Headspace comparator so you know how far you're bumping the shoulders when re-sizing. This will avoid any case stretching above the belt.

Here is a pic of a case I sectioned just to see if it was stretching above the belt after many re-loads. (never mind the short neck, I chopped it for something else)

Notice no brass thinning at all. The Hornady headspace comparator is worth the money.


3749

[Bigbuckdn]

Don't worry about larry wills die unless you're using once fired brass from another rifle that will not fit into yours.


After the initial firing the headspace moves to the shoulder not unlike non-belted cartridges so don't sweat it and load it like any other. Just get yourself the Hornady Headspace comparator so you know how far you're bumping the shoulders when re-sizing. This will avoid any case stretching above the belt.

Here is a pic of a case I sectioned just to see if it was stretching above the belt after many re-loads. (never mind the short neck, I chopped it for something else)

Notice no brass thinning at all. The Hornady headspace comparator is worth the money.


3749






























I was not worried about larry's die I meant I was not worried about case separation at the belt. I just loaded ad normal and then it happened but then as you stated that was once fired brass from another gun

[jim_k]

Just my experience, but I had new brass in a .300 Win Mag that I traded in, so I no longer have it. Fired new factory ammo, but can't remember the brand. Sized it based on headspace as noted by poster above, and fired a couple of times in my rifle. No used brass, and no other rifle. Then I could not chamber it, and almost got a live round stuck in the chamber (no bueno). Checked the brass with the gauge on the Larry Willis die, and it was too wide. Ran it through the die, and no problem after that. YMMV.

[yobuck]

Using the shoulder on a belted case is fine, but regardless how you go about the process case failure is still at least a possibility.
One thing to have it happen at a range, but much more serious if it happens in the field especially when shooting at an animal.
I wont use brass that's more than once fired for hunting, and every round is chambered in the gun before it goes along.

[Zero333]

Just my experience, but I had new brass in a .300 Win Mag that I traded in, so I no longer have it. Fired new factory ammo, but can't remember the brand. Sized it based on headspace as noted by poster above, and fired a couple of times in my rifle. No used brass, and no other rifle. Then I could not chamber it, and almost got a live round stuck in the chamber (no bueno). Checked the brass with the gauge on the Larry Willis die, and it was too wide. Ran it through the die, and no problem after that. YMMV.

Now that you bring it up. I've only owned 300 winmags made by Savage and their headspace is always good. This might not be the case with all manufacturers and if there is too much HS between the belt and chamber (even tho the HS between the shoulder and chamber is good) will lead to the bulge.

I guess I've just been lucky.

[hafejd30]

I size my brass for my 300 WM same way I do any other brass. Neck sized and shoulder bump when needed. If it gets past that I'll chuck the brass and buy new brass. It's a hunting rifle so it doesn't see as many firings as a prairie dog rifle tho. About 200+ rounds this year so far. Same 50 pieces of Nosler Brass. Like yobuck said tho, I will check the rounds that I put in my rifle before going on an important hunt. My brass was new when fired in my rifle.

[lvjake7761]

i shoot 7mm RM and have had the belt problem
after 1 firing my necks have expanded after 2 firings i start getting sticky extraction
after that cases wont fit at all
i was really perplexed until i found Larry Wills's collect die
his dies thread in from the underside of the press making it kinda weird to use but they work like a dream
the top of the die is a gauge so you can drop a case in and see if it needs to be worked
if i get one case in the batch that needs it i run them all through the die
if i dont keep after them and let them get to the point where they wont chamber it's hard
to bring them back if i keep on top and run them through this die at first sign of needing it
it requires alot less movement and i can go through a box of 50 in maybe a half hour
one thing i have found though dont use imperial sizing wax like they say to use
ive started using LEE resizing Lubricant and this stuff it perfect for the collect die
i use a little brush and lube every 3rd case
i can say enough good about Larry and Innovative Technologies

[yobuck]

It's actually not a belt problem. It's a problem caused by the method used to resize the case.
Use cheap regular old full length dies, and full length resize the cases and the (problem) of chambering wont exist.
But case/head separation can still be an issue we deal with. Ive had it happen with non magnum cases also.
As a rule, I lose brass due to loose primer pockets with the magnum cases anyway.
About 20 or so years back belted cases really came under attack by the accuracy shooters as being a cause of poor groups.
Those in the know were building guns without belts on the cases, even if it meant turning the belts off, which to me actually makes more sense.
The WBY case was sneered at due to the belt and that stupid looking shoulder. The beltless cases like Rigby became the big deal to use if you ever expected to hit anything.
Today if you talk to guys like Bruce Baer they aren't as certain about that as they were 20 years ago, especially on hunting guns.
Anyway probably 90% percent of those in the know are now shooting Dashers. lol

[lvjake7761]

It's actually not a belt problem. It's a problem caused by the method used to resize the case.
Use cheap regular old full length dies, and full length resize the cases and the (problem) of chambering wont exist.
But case/head separation can still be an issue we deal with. Ive had it happen with non magnum cases also.
As a rule, I lose brass due to loose primer pockets with the magnum cases anyway.
About 20 or so years back belted cases really came under attack by the accuracy shooters as being a cause of poor groups.
Those in the know were building guns without belts on the cases, even if it meant turning the belts off, which to me actually makes more sense.
The WBY case was sneered at due to the belt and that stupid looking shoulder. The beltless cases like Rigby became the big deal to use if you ever expected to hit anything.
Today if you talk to guys like Bruce Baer they aren't as certain about that as they were 20 years ago, especially on hunting guns.
Anyway probably 90% percent of those in the know are now shooting Dashers. lol
I hadn't thought about that and it makes sense i think i neck sized at the begining that may have been what got it started
I do remember though once i had cases starting to deform i couldn't correct it with a full length die
The case would get stuck before it got deep enough to set back the sholder


Sent from my SPH-L710 using Tapatalk

[yobuck]

Well try a different shell holder with the full length die and see if that dosent help.
Sinclair sells a set of what they call competition shell holders for the purpose of bumping the shoulder back more.
Just follow the directions until you get to the one that allows the bolt to close.
But it could well be that brass is now junk.
If a guns gonna shoot well, its gonna also shoot with cases that are full legnth resized, and if it don't, how you size wont matter much.
If you want tiny groups you wont be shooting a magnum anyway.
Magnums have but one purpose, better performance for hunting at longer distances.

[snowgetter1]

So I guess the small base full lenght size die would be best? Then if brass begins to swell get the Larry Willis body die.

[yobuck]

For resizing any cartridge used for hunting, full length resizing is the safest way to go about it to assure it functioning properly.
Even then, if the brass is loaded enough times chambering problems might occur, assuming you haven't lost the brass due to other issues like primer pockets, neck splits and so forth.
If it does happen, ive personaly never had it that a different shell holder didn't fix it.
I have had brass given to me by friends that I couldn't resize to use in my guns however.
While I'm familiar with body dies, I'm not familiar with the one mentioned so I wont comment.
Fact is though standard full length RCBS, Lee, Redding, and others will all produce good accurate loads.
Bullet runout is I feel a seperate issue, and even though I don't use them, I can see the virtue of a better seating die.
I simply rotate the case a few times while seating the bullet using the standard die.

[snowgetter1]

Ok thanks for all the good info guys!

[bigedp51]

Excessive head clearance or the air space between the rear of the case and the bolt face is what causes case head separations. This excessive head clearance allows the case to stretch beyond its elastic limits.

https://i.imgur.com/HK76WCp.jpg

I collected .303 British Enfield rifles and at maximum military headspace you can have as much as .016 head clearance.

https://i.imgur.com/sHgqVJR.gif

As stated above with proper fire forming and letting the case headspace on its shoulder head clearance can be held to .001 to .002 or less.

https://i.imgur.com/AQEQ9Vw.jpg

The problem with the belted magnum is small diameter cases in relation to chamber diameter above the belt. Then add this to resizing dies that do not size far enough down the case just above the belt and this area of the case is never sized and binds in the chamber.

A small base die will reduce case diameter approximately .003 more and bump the shoulder back .003 more than a standard full length die. Meaning bring the case back close to SAAMI minimum diamentions. BUT nothing is written in stone, I have a standard Lee .223 die that reduces the case diameter and pushes the shoulder back more than my .223 RCBS small base die. Meaning either type die might not size the case just above the belt enough.

And now to make belted rifle owners feel even better, the belted case is a older British design from the turn of the 20th Century and out dated by modern designs. (Bazinga)

The British used cordite powder that looked like long strands of spaghetti and the case shoulder and neck of the case was formed "after" the cordite powder was placed in the case. Meaning the case shoulder location of rimmed and belted cases were not critical in British thinking.

Bottom line, the famous American Jack O'Connor was correct..................the .270 Winchester is the best non-belted magnum in the world.

https://i.imgur.com/d4VFLtP.jpg

"Raping and pillaging reloading forums is a great hobby"
Attila the Hun

[yobuck]

And he enjoyed lots of free safaris compliments of Winchester in order to reach that conclusion. lol
Had he not been enjoying the free campfire cocktails so much he might have realized what dumb things he said.
But he like other heroes of his age were above reproach.
That era was actually the beginning of what we now know as fake news.

[Zero333]

The problem with the belted magnum is small diameter cases in relation to chamber diameter above the belt. Then add this to resizing dies that do not size far enough down the case just above the belt and this area of the case is never sized and binds in the chamber.



This explains everything.