300 win mag f class

[dannywayoflife]

Is 300 win mag allowed in open f class?

[Ronin]

Yup

 

anything 8mm and under allowed...

[dannywayoflife]

thanks thats what i thought but i saw on diggles website that belted magnum is not allowed in f class.

[baldie]

No, its a belted magnum.

[dannywayoflife]

so is it a yes or a no? Ive only seen the mention of belted magnum not being allowed on the diggle website.

[baldie]

To the best of my knowledge, all calibres over 8mm and belted magnums are NOT allowed full stop. I could be wrong, i,m not an F class shooter, but thats the version i,ve been repeatedly told.

[dannywayoflife]

i knew the 8mm limit but didnt know the belted magnum rule ill have to do some more digging on the subject

[dannyt]

ive seen 300wm used at Diggle f class shoots and 30.338 lap mags used there and all the uk f class shoots.

[desparado]

Danny,

 

There is no prohibition on belted magnums in National & International F-class rules.

Over the years, I can think of several guys who've used the 300 Win mag', 7 Rem mag' & 7STW - all belted obviously.

 

Some clubs may have their own local rules, though any reference to belted magnums is frankly, an anachronism nowadays.

 

Cheers.

[dannywayoflife]

Desperado thanks for that. I'll bear that in mind

[Laurie]

Danny,

 

the reason you don't see belted magnums too often in F, or any other discipline, is not to do with any rules as Des points out, but rather because there are rather a lot of built-in problems with the design.

 

Before a number of forum members reach for their keyboards, to shout polite abuse, that's not to say that the .300 Win Mag and before it, the .30-338, and even the old .300 Holland & Holland are inaccurate. It's just that modern rimless cartridges are a technically much more elegant way to go. So, the SAUM, WSM, wildcats based on the 8X68mm RWS are much more favoured these days.

 

The problem with a belt is that it adds another dimension / item to the cartridge and performance, and a troublesome one at that. The original idea of the belt was and still is excellent in its proper context - a smooth and reliable feeding/extracting design for dangerous game cartridges to be used in bolt-action magazine rifles. It has the rimmed case's big plus of headspacing at the rear end allowing the case-body to be a relatively loose fit in the chamber for 100% reliable chambering even when the mercury is at 120 and the humidity turns cartridges green while you look at them. However, the rimmed case doesn't feed well in bolt-action magazine rifles - hence H&H inventing the belt before World War One when the traditional break-open British double rifle was challenged by Mauser action bolt designs to make it headspace as per a rimmed job, but feed as well as the rimless designs the Austrian and German competitrors were chamebred for. (Despite the widely held view, a belt has nothing at all to do with case strength and a belted case may be weaker or stronger than a rimless competitor, but always due to other design features.)

 

The problem with the belt is that it adds another factor into the case's / round's relationship with the chamber. In addition to shoulder position, there is the belt fit and position in its recess at the back of the chamber. Every time you fire a 65,000 psi belted cartridge, that belt changes its dimensions a little, but the chamber doesn't. Also, you can't resize a belted case body right down the belt, so they soon have a tight fit with the chamber just above the belt. These changes don't happen at an equal rate to every case in the box, so you have inconsistencies moving into the 20 or whatever number of rounds you fire in a match unless you junk the brass after only a couple of firings. There is a guy in the USA makes a special collet body die to properly FL size these cases. He only makes them occasionally and the last time I looked, it cost around $250.

 

Riflemakers chamber belted magnum sporting rifles very loosely up front as the belt is doing the headspacing work. That's why setting a FL sizer die up to touch the shellholder is usually a bad idea with cartridges for these rifles - the shoulder has fireformed into the chamber shape and is now pushed back a large way by the die. The amount of working of the brass in this constant fireform / resize cycle soon sees the case separate usually about two-thirds of the way up the body. A match rifle chamber will be a lot tighter, but even so, normal practice in the heyday of the belted cartrtidge long-range competition rifle was to fireform the brass and subsequently resize it to move the headspacing work to the shoulder as per a common or garden rimless case. The belt recess would be cut marginally deep and when so set up, the front of the belt didn't touch the ledge in the belt-recess, the case shoulder contacting the front of the chamber before that happened - in other words, the belt was stopped from undertaking its normal role and became in practice redundant. The reason people used these cartridges was because of their large capacity and high performance and the brass was easy to obtain and cheap compared to the very few rimless competitors, all of which originated in continental Europe. As soon as the 6.5-284 caught on the .300 Win Mag's popularity shrank in this role and the WSMs / SAUMs have nearly killed it off. The military on both sides of the Atlantic still like the cartridge, although .338LM has overtaken it in the very long-range sniping role.

[baldie]

Thanks for that very informative reply Laurie.

I,ve built quite a few 300winmag,s over the years and have always headspaced very tight to avoid the case separation issues they exhibit. I would like to know how the guys cut the belt deeper however, as it isn,t possible with the reamer, as it also shoves the shoulder forward at the same time ? I can only assume they get in there with a tiny boring bar. Wouldn,t pass proof in the UK however, as they use headspace gauges that gauge off the belt.

 

This topic only serves to illustarte the fact that the shooting public, gunsmiths etc etc, dont know all the rules regarding competition.

 

If you have time, and can list links to all the benchrest, F class, etc rules and regs, i will gladly make them a sticky here.

[dannywayoflife]

Laurie thanks for that informative piece that really clears things up thanks

Danny

[ChrisF]

I would advise you to look real hard at what most are using already in this class & try not to reinvent the wheel , look at 7mm Shehane & 7/300 WSM , driving a 180gr Berger .

 

However , I have a heavy 300WM rifle , and its a repeater , truck axle barrel & a Brake simialr to the 2 chamber AI magnum , and have fired it quickly at a tac shoot for 5rds at a time , less than a minute , and due to the recoil of the 208gr Amaxs at 2880 fps , find sometimes I could not spot my own hits .

In F-Class , I donot think you can use Brakes to reduce recoil ,maybe cans are OK ?, not sure about UK F-class , here in Nz we can use cans/suppressors , it still has to make the weight regs thou .

 

If you are dead set on using a belted mag , I would go std 7mm RM .

 

Its up to you .

 

Later Chris

[desparado]

I donot think you can use Brakes to reduce recoil ,may cans , not sure about UK F-class , here in Nz we can use cans/suppressors ,Later Chris

 

Chris,

 

Muzzle brakes are illegal in all F-class matches.

Moderators are ok for NRA and National League matches, but illegal for ICFRA matches eg, FCWCs.

 

Cheers.