JARACAL

Dagse,

Weet iemand dalk wie plaaslik a reamer het vir a 7mm/300 Win Mag?

Sean, rather look at a beltless case wildcat, 7mm Gwaza from 8x68 RWS case.....

Already chambered for 7mm RM so it is a quick clean out and you have new throat with the 7mm-300 Win Mag and additional volume for the 180gr to do 2980 - 3050fps.

No barrel set back required so keep full length.

I like the belt - helps re-enforce that case head and brass is all over.
Run a tight spec reamer in Belt area.

Don't need any new dies. Short neck issue is over emphasized and in a Rem 700 LA is able to accommodate the extra length.

I'll bring one in if none available this side - just checking if anyone was onto it over here.

Those 8x68mm cases are hard to find.
But thanks for input, I'm not in a hurry.

I like the belt - helps re-enforce that case head and brass is all over.

How do you come to that conclusion, cut open a case, the belt don't make it stronger, it was invented because cases like the 300 H&H have sloping shoulders, they
felt that it could not headspace on the shoulder so that is why the belt was added, not to make it stronger.

There is a gunsmith in the Paarl area that did a 7mm PRACTICAL for one of the shooters at our branch of SA hunters.
The rifle shoots on the numbers out to 1000m.
DD

Dit is ñ blink plan Vaalbos, waar kan ek meer oor die kaliber lees?

Dit sal ñ wonderlike kombinasie wees met die nuwe 197gr SMK.

Groete

Johann

Gaan google 7mm300winmag longrange shooters of utah.

Ek het in Desember met Chrisjan begin praat oor die bou van my 7mm Practical, hierdie is die beste artikel wat ek kon kry oor die kaliber.
https://www.ballisticstudies.com/Knowle ... tical.html
Ek het my bou bietjie op ys gesit om ander projekte om die huis te finansier, maar eendag.....

Hi Flip,
Sorry, I have been away from base a couple of days.
I think most of the forum members are aware that the belt on the belted magnum cartridges was intended to ensure gently tapered cartridges have something providing resistance to the impact of the firing pin and in so doing ensure proper and consistent ignition of the primer.
This belt was first introduced on the 400/375 Nitro by Holland and Holland in 1905 and carried over to the 375 and later 300 H&H for obvious reasons.
I shoot a number of belted magnum cartridges which have been used at the top end of their ballistic window. Depending on the case manufacturer, it is evident that some brass is able to take a lot more pressure than others before permanent deformation sets in and renders the case useless. The outer dimensions of the cases are all defined by standards and specs but the insides are free for manufacturer interpretation. In most instances the draw punch design that is used to extrude the brass cup into the case form differs from manufacturer to manufacturer. This results in differing geometry in the case head and web area. Three characteristics determine the ability of the brass to resist the permanent deformation and they are brass composition, work hardening and geometry.
The belt is located in the web area of the case and in engineering terms, any time you add material to an area the strength is increased in that area. This can be both internal and external in terms of a cartridge case. Creating the Belt usually requires an additional form to bump up to the belt diameter after extrusion and in so doing working the brass more in this critical area.
One of the most active proponents of the belted magnum in the last century has been Roy Weatherby. When creating the 378 Weatherby Magnum, we know that the .416 Rigby case was used as the dimensional basis for his design. Why was the belt included into the design of the Weatherby case – marketing or necessity (by accident or intent)?
I don’t know, but I do know that when the US Military tasked RAI to develop the predecessor to the 338 Lapua in the early 1980’s, they also used the .416 Rigby case and were unable to achieve the desired 3000fps with the 250gr SMK bullet in this case as per Rigby spec. The .338/378 Weatherby Mag with a reduced case capacity, was achieving that in 26” barrels and had been doing so as a wildcat cartridge since the early 60's. This belt is not necessary to provide headspace on any Weatherby cartridge and is not used as a headspace characteristic by handloaders as it results in case stretching and reduced case life. The belt adds strength to the case in this area exactly where the Rigby case was deforming, hinging open and resulting in enlarged primer pockets.
The 338 Lapua Mag almost never saw the light of day due to the above case shortcomings. Lapua overcame the problem and re-enforced the case head internally but lost case capacity as a result which bumps up the operating pressures. The 3000fps with 250gr SMK bullet is typically only achieved with 26” + barrels as a result.
Interestingly, the CIP max pressure for the 338 Lapua Magnum was reduced to 60916psi in 2007 due to high temperature incidents and resultant high pressure generating plastic deformation of the case head.

Bottom line is that designed operating pressure will determine the case failure point but some extra strength built into the case design is not to be ignored when pushing things along as the Weatherby’s and other Magnums are intended to do.
If someone has their personal hate of the belt on some of the Magnum cartridges I’m OK with that but I’ll take a belt on a case if I can and it’s not going to be for headspacing reasons.

The above pic refers - somehow the comment was not published;

Failed attempt (1st ) on left at forming 7mm-300 Win Mag using only a tungsten neck and shoulder die. 2nd attempt with Std RCBS Full Form Die and lube next to stock 7mm RM on rhs.

Sean, the neck is too short.................. for good accuracy and low ES and SD, according to the keyboard snipers.

swc-tr wrote:Sean, the neck is too short.................. for good accuracy and low ES and SD, according to the keyboard snipers.

Yip, you see a lot of that.

Build a 28Nosler

Myne is “in the making”
Reeds reamer bestel. Loop oppad. Chassis system gekoop. Kan nie wag nie!! 180gr teen 3050ft/sec G7 BC 0.4


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[quote="LRLaubscher"]Myne is “in the making”
Reeds reamer bestel. Loop oppad. Chassis system gekoop. Kan nie wag nie!! 180gr teen 3050ft/sec G7 BC 0.4

Geweer Spec ?

Vaalbos wrote:I shoot a number of belted magnum cartridges which have been used at the top end of their ballistic window. Depending on the case manufacturer, it is evident that some brass is able to take a lot more pressure than others before permanent deformation sets in and renders the case useless. The outer dimensions of the cases are all defined by standards and specs but the insides are free for manufacturer interpretation. In most instances the draw punch design that is used to extrude the brass cup into the case form differs from manufacturer to manufacturer. This results in differing geometry in the case head and web area. Three characteristics determine the ability of the brass to resist the permanent deformation and they are brass composition, work hardening and geometry.

If you can generalize, which cartridge brands are 'better' in the belted magnums than others?

I use a 300H&H and have mostly used Hornady, which I have found to be average at best. Signs of case head separation at 3-4 reloadings in some cases. I seldom run close to max. pressure/velocity. I am migrating over to Norma, hence my question - I am hoping that Norma will be superior to the Hornady and hopefully help with accuracy too. I am asking for a lot!

Desperatezulu wrote:

Vaalbos wrote:I shoot a number of belted magnum cartridges which have been used at the top end of their ballistic window. Depending on the case manufacturer, it is evident that some brass is able to take a lot more pressure than others before permanent deformation sets in and renders the case useless. The outer dimensions of the cases are all defined by standards and specs but the insides are free for manufacturer interpretation. In most instances the draw punch design that is used to extrude the brass cup into the case form differs from manufacturer to manufacturer. This results in differing geometry in the case head and web area. Three characteristics determine the ability of the brass to resist the permanent deformation and they are brass composition, work hardening and geometry.

If you can generalize, which cartridge brands are 'better' in the belted magnums than others?

I use a 300H&H and have mostly used Hornady, which I have found to be average at best. Signs of case head separation at 3-4 reloadings in some cases. I seldom run close to max. pressure/velocity. I am migrating over to Norma, hence my question - I am hoping that Norma will be superior to the Hornady and hopefully help with accuracy too. I am asking for a lot!

Case head separation after 3 or 4 reloads is something else other than poor brass imo, I have Winchester brass that I use in one WM that has over 13 reloads on over over more than 5 years of use and they are still going strong

Vaalbos wrote:

LRLaubscher wrote:Myne is “in the making”
Reeds reamer bestel. Loop oppad. Chassis system gekoop. Kan nie wag nie!! 180gr teen 3050ft/sec G7 BC 0.4

Geweer Spec ?

Wat spesifiek wil jy weet Vaalbos?


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If you can generalize, which cartridge brands are 'better' in the belted magnums than others?

You migrating in the right direction.
Norma is very consistent and pockets stay tight longer.

[quote="LRLaubscher"]


Wat spesifiek wil jy weet Vaalbos?

Aksie, Loop, Sneller, Kolf, maak en styl van chassis ens..
Monterings en glas planne.
Dis mos lekker om die dinge te beplan en hoor wat beplan ander.
Wie gaan bou?
Miskien moet my loop ook a snytjie kry.

Vaalbos wrote:

LRLaubscher wrote:

Wat spesifiek wil jy weet Vaalbos?

Aksie, Loop, Sneller, Kolf, maak en styl van chassis ens..
Monterings en glas planne.
Dis mos lekker om die dinge te beplan en hoor wat beplan ander.
Wie gaan bou?
Miskien moet my loop ook a snytjie kry.

7mm-300WM (Nie die 7mm Practical nie)
Howa 1500 LA Aksie, Blue Printed, Bolt fluted en aksie Ceracoated Flat Black
Accugun/Mojet 1-8.25twist Heavy Varminter Fluted 7mm loop gekroon op 30”
Howa Hact 2 Stage Trigger, getoor!!
MDT LSS XL Gen2 in FDE met ergo grip
20 MOA Warn Steel Piccatinni Rail
Tier One Precision Ringe met internal Bubble
Vortex Razor Gen2 4.5-27x56 Mrad Scope
Gunsmith is Geoffrey Barrabal by Guncraft
180-197gr pille teen 3050-3080ft/sec met VV N570
Chamber Pressures onder 55k psi voorspel.





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Vaalbos wrote:

LRLaubscher wrote:

Wat spesifiek wil jy weet Vaalbos?

Aksie, Loop, Sneller, Kolf, maak en styl van chassis ens..
Monterings en glas planne.
Dis mos lekker om die dinge te beplan en hoor wat beplan ander.
Wie gaan bou?
Miskien moet my loop ook a snytjie kry.

Nous Vaalbos dood stil. Tiepies


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[quote="LRLaubscher"]

Nous Vaalbos dood stil. Tiepies


Nee net besig.
Dankie, lyk soos a mooi beplande projek.
Hoort regtig goed te skiet. Howa het goeie ondersteuning vir swaar loop.
Voer maar die draad met info soos dit bymekaar kom asb.

Alle voorspoed.
Jy sal moet ladings en teikens post!

Vaalbos wrote:

LRLaubscher wrote:
Nous Vaalbos dood stil. Tiepies


Nee net besig.
Dankie, lyk soos a mooi beplande projek.
Hoort regtig goed te skiet. Howa het goeie ondersteuning vir swaar loop.
Voer maar die draad met info soos dit bymekaar kom asb.

Alle voorspoed.
Jy sal moet ladings en teikens post!

Dankie Vaalbos ja ek sal so maak.


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LRLaubscher wrote:

Vaalbos wrote:

LRLaubscher wrote:

Wat spesifiek wil jy weet Vaalbos?

Aksie, Loop, Sneller, Kolf, maak en styl van chassis ens..
Monterings en glas planne.
Dis mos lekker om die dinge te beplan en hoor wat beplan ander.
Wie gaan bou?
Miskien moet my loop ook a snytjie kry.

7mm-300WM (Nie die 7mm Practical nie)
Howa 1500 LA Aksie, Blue Printed, Bolt fluted en aksie Ceracoated Flat Black
Accugun/Mojet 1-8.25twist Heavy Varminter Fluted 7mm loop gekroon op 30”
Howa Hact 2 Stage Trigger, getoor!!
MDT LSS XL Gen2 in FDE met ergo grip
20 MOA Warn Steel Piccatinni Rail
Tier One Precision Ringe met internal Bubble
Vortex Razor Gen2 4.5-27x56 Mrad Scope
Gunsmith is Geoffrey Barrabal by Guncraft
180-197gr pille teen 3050-3080ft/sec met VV N570
Chamber Pressures onder 55k psi voorspel.





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Impressive syfers!

Wat is die loopleeftyd op daai roer?
1800 houe?


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