Handloader Mag, June 2017 FAKE NEWS? - Page 3 - Graybeard Outdoors
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post #21 of 31 (permalink) Old 05-26-2017, 05:29 PM
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Originally Posted by AccelR8 View Post
I get the digital addition of American Rifleman (save a tree). All my dad's old ones are long gone. I'd love to have them today.

On the subject of belted magnums and case stretching; I do have a 300 WM which is a belted magnum but the little amount of shooting I do with it is mostly factory ammo so I can't speak from experience. I had made a comment previously about firing and resizing with excessive head space but I was thinking of a non belted cartridge. After some research it appears that the concern with a belted magnum is if you have a long (maximum dimension) chamber and you're repeatedly full length resizing, pushing the case shoulder back to a minimum dimension. So you can have good tight head space because of the belt and still have a case that is being repeatedly stretched long and then squashed short.

But that's a little different than what the article was talking about which is fire forming.

With a rimless/beltless case one can adjust the sizing die to dimension the case so it is very slightly less than maximum even to the point that when the bolt is cammed close headspace is a press fit. If one sizes so the belt seats tightly against the belt shoulder there can be a gap between the belt shoulder and bolt face long enough to create excessive headspace. The belt interferes with the bolt's ability to cam the case forward for a tight fit. It is possible to adjust headspace to one dimension such as a rimmed case rim, or to a rimless case's datum point. It is difficult to make it fix simultaneously two separate dimension (belt & datum point). Belted cases are a poor design choice in small arms. They solve no problems while creating a new one. The only place they serve a purpose is in some rapid fire cannon where the inertia/momentum of a forcefully chambered cartridge may need a positive stop to prevent the case should from being forced too deep into the chamber thereby producing dangerous headspace. That is why the 27mm Mauser cannon round is one of the few such cartridges its rounds being rather violently slung into the chamber.

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post #22 of 31 (permalink) Old 05-26-2017, 05:33 PM
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Originally Posted by nanuk-o-dah-nort View Post
EXACTLY!


if you create a false shoulder.... so what? that is to hold the head against the bolt face/breechblock. if the Belt was doing that as stated in the article, the false shoulder would do NOTHING


any ANYONE ever had a problem with brass stretching at the case head when forming 30-30AI, or KHornet? Or how about fireforming new brass in a military chamber in a SMLE??

what about putting a long bullet in and jamming it into the rifling? once the gun goes off, you would have the situation of a totally unsupported cartridge, yet that is not a factor, as brass expands ALL directions... it doesn't stretch forward from the BACK END!



Right. That is why the former British method of pressure testing lubed the entire cartridge before loading so there would be no adhesion between the case and the chamber. The result was that firing caused the entire case to be forced back against the face of the breech resulting in a fired case fitted to the maximum internal chamber dimensions. A case that doesn't 'grab' the chamber walls is not going to experience case stretching.

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post #23 of 31 (permalink) Old 05-26-2017, 05:35 PM
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Originally Posted by nanuk-o-dah-nort View Post
read the article, if you can find it... your experience is the same as mine. You'll be shaking your head also


The thinning of the case head has nothing to do with the sizing. It occurs when the cartridge is fired. The lengthening of the case is a consequence not the cause.

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post #24 of 31 (permalink) Old 05-26-2017, 05:39 PM
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Originally Posted by AccelR8 View Post
I've fire formed lots of Hornet brass to K-Hornet. It is very easy to see by looking at the brass after firing, the unformed part has the original sheen and the part that moved to conform to the chamber has a different appearance. All the movement occurs at the front of the case.

I think that author may have been thinking of how, after repeated firing and then resizing brass with a lot of head space, brass flow may cause thinning in the web area. I'll defer to those here with more experience though.


I have formed 22 K-Hornet, 7mm AI, and 30-30 AI. If the bases of your cases are unmarked consider that the load did not generate enough pressure to expand that part of the case to fit the chamber walls.

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post #25 of 31 (permalink) Old 05-26-2017, 05:47 PM
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[QUOTE=nanuk-o-dah-nort;2055094417]Is it me?
Do the Gun Rag writers have nothing left to say, they have to make stuff up?




BUT, it IS stated: "The position of the belt does keep the case head in tight contact with the bolt face, but if a case is short on the shoulder, a belt does not prevent it from stretching at the web as a cartridge fires and expands to fill the chamber."

WHAT THE.... ???? This new revelation will come as news to the tens of thousands of shooters who routinely fireform brass with a belt or rim moving the shoulder forward. (30-30AI, KHornet to name but two)

This is EXACTLY what the belt does if it is in "Tight Contact with the Bolt Face"! A rim does the exact same thing!

The belt of a belted case experiences the same problem as the rim on a rimmed case. They are rigid and do not permit the case to conform to the inside of the chamber. Due to manufacturing tolerance between different guns and different cases the linear deviation can be quite great at times. The best way to load belted and rimmed cases is to ignore the belts and rims and adjust the dies to keep the base pushed back as far as reliably possible. Of course with rimmed straight cases there is no should to push against and one must depend of the headspace rim thickness setting and hope for the best.

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post #26 of 31 (permalink) Old 05-26-2017, 07:23 PM
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I understand the case stretch and resultant brass thinning occurs during firing. My point about resizing was that the brass stretches again on the subsequent firing and it's that repeated fire-size-fire cycle that leads to problems.

It seems that the way we wound up with belted magnums is...well take the 300WinMag as an example, it was developed using the 375 H&H Magnum as the parent brass. That cartridge (375 H&H) had a very tapered body and a not so well defined shoulder. Apparently it's designers felt using the shoulder to stop the cartridge might not be consistent enough and head space might be unpredictable as a result. They didn't want to use a rim because they felt rimless was the way to go in a box magazine so the belt was a compromise, or an elegant solution, depending on if you're selling it or not.

So the belt just got carried over when somebody chose the 300 H&H Mag. case as the parent for the 300 WM. I suppose that was a cost effective choice but it seems to me there's been enough 300 WM ammo made to offset the cost of a new case...? Of course I could be wrong on any or all of this.

When it comes to cartridge design, I wonder...if the Ackley Improved features of straight (or nearly so) body and a sharp shoulder (40 degrees?) are such improvements, why do newer cartridges appear with tapered bodies and lesser shoulder angles (20, 30 degrees)? Is it because tapers and more gradual shoulders provide more reliable feeding, chambering and extracting? If so, do the AI cartridges have problems with feeding and extracting? Are A.I. shooters, who are more enthusiasts than the general public, willing to work through such issues?

Am I derailing this thread? If so I'll cease and desist but inquiring minds want to know!
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post #27 of 31 (permalink) Old 05-27-2017, 07:08 AM
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I receive a shopping bag of gun mags every month, stuff like shooting times, rifleman, shot gun news, guns and ammo, along with many more. Boring stuff unless your into reading about AR's, Hand guns and propaganda. I have a roll of jute twine in the coffee table near my recliner, roll those magazines up tie them with some twine. Take them to the furnace room and put them to a decent use adding heat to the house.


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post #28 of 31 (permalink) Old 05-27-2017, 05:10 PM Thread Starter
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Originally Posted by gcrank1 View Post
The shoulder is a restriction (just like your thumb over the end of a water hose), the pressure from the case body (expanding gas) hits the internal wall of the shoulder and pushes it forward (like the water in the hose trying to push your thumb off) while it is releasing the bullet, which has resistance to moving (intertia) and the brass is still being pushed forward likely until that projectile exits the case mouth and there is a pressure drop. The brass 'thins' back at the junction of the case wall and case head.
This happens every time the case is resized 'too short' for the 'too long' chamber. The cartridge manufacturers have no control over this 'fit', we as reloaders do, and it is our due diligence to make the best fit possible rather than just continuously full length resizing for a too long chamber. Our reward is 'custom fit brass' to our rifles, which last longer and may be as good, or better, in accuracy and far less expensive.
This thinning is bad enough in typical cases and possibly even worse in rimmed (and a belted case is just a rim in a different place) where the back end is locked in. The belted cases may exhibit case head failure more quickly because they are typically used for high pressure loadings.
Make the rim and shoulder contact their respective 'seats' at the same time in chambering and happiness and long life will be found.

I don't think you have this quite correct

as stated in the article, creating a false shoulder would do NOTHING if what happens is as you say, as the main shoulder area would still create stretching



the shoulder is not moved forward so much as the neck/shoulder junction is moved out an an angle... pressure is not linear, but radially centric. Think balloons.

as soon as pressure builds, the WHOLE case expands, even the neck area to release the bullet, that is why there is gas cutting

as the pressure builds, the front half of the case grips the wall directly outside it, and the front moves out and forward, the rear moves out and back (out as much as it can, as brass thickens, it resists the outward movement.
it is THIS pushing of the base back that causes the thinking near the base. IF the base is held tight on the bold face, there can be NO Thinning near the base to create separation

with a rimmed or belted case with TIGHT headspace there will be NO thinning near the base.

rimless are the WORST for this effect if too short headspace.

MANY MANY wildcats move the shoulder foward and outward with NO case stretching at the base.

With SMLE's in 303Brit, with historically HUGE chambers, what folks have done to create perfect brass, is to expand the neck and create a false shoulder to hold the base TIGHT against the bolt, wrap a 1/4" wide piece of tape to "Fatten" the base to it is chambered concentric, lube the case, and fireform with cream of wheat.

out pops out a perfectly sized case, capable of excellent accuracy if the rifle is up to it.
There is NEVER any thinning near the base.

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Originally Posted by BAGTIC View Post
The thinning of the case head has nothing to do with the sizing. It occurs when the cartridge is fired. The lengthening of the case is a consequence not the cause.
it does! With a rimless case with too short headspace, the firing pin pushes the case forward upon impact, the shoulder hits the front of the chamber, the powder ignites, pressure builds, brass expands and grips the walls, and the base has no support so moves back, stretching at the area between where the brass is gripping the walls, and where brass thickens to the point of not being able to expand.
This only happens with higher pressure cases as proven by Ackley

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Originally Posted by BAGTIC View Post
The belt of a belted case experiences the same problem as the rim on a rimmed case. They are rigid and do not permit the case to conform to the inside of the chamber.
Huh?

belts and rims do a better job than nothing.... when a case is too short in the HS department, if there is nothing to hold it back, it WILL cause problems

this is well documented and why they sell "Broken Shell Removers"

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post #29 of 31 (permalink) Old 05-27-2017, 05:20 PM Thread Starter
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Hornady has a good article on this issue

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post #30 of 31 (permalink) Old 05-27-2017, 08:03 PM
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You clarified better what I was thinking but didnt say quite right; ie, when I said the pressure hits the shoulder and pushes it forward, along with the bullet, what I didnt say was what you did, then the back end of the case (the containment vessel) body has to expand, both radially (held in check by the chamber) and back at the head if there is too much headspace, thus the thinning.
Im sure many are only interested in what to do (the Readers Digest Condensed Version) but Ive always been intrigued by the why of things and reloading has certainly kept me entertained!
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