OzFclass

There is no doubt that a big 30 cal pill can be very competitive.
Especially if it is well over the energy limit.

But does it make any sense to compare it to a 7 mm limited to 2850 f/s.

If both are unlimited, you need to compare with a 7 mm at well over 3000 f/s

Peter Smith.

Now your talking!
7mm RUM anyone?

Soooo
What cartridge will drive a 230gn 308 @ 2600 f/s efficiently?

Tim N wrote:Soooo
What cartridge will drive a 230gn 308 @ 2600 f/s efficiently?

Tim,

The short mags are efficient. The obvious choice is 300WSM. But the 300 RSAUM is a smaller case and would still do it, so on paper at least, more efficient. On the other hand, I have heard that in 30 cal form the WSM gives longer barrel life than the RSAUM. Strange really, because its quite widely believed that the 7mm RSAUM is easier on barrels than the 7mm WSM.

Alan

AlanF wrote:

Tim N wrote:Soooo
What cartridge will drive a 230gn 308 @ 2600 f/s efficiently?

Tim,

The short mags are efficient. The obvious choice is 300WSM. But the 300 RSAUM is a smaller case and would still do it, so on paper at least, more efficient. On the other hand, I have heard that in 30 cal form the WSM gives longer barrel life than the RSAUM. Strange really, because its quite widely believed that the 7mm RSAUM is easier on barrels than the 7mm WSM.

Alan

300 RSAUM, or maybe even an improved 30 cal version of the 284W case at a push for 2600fps. Like the Davis or Shehane improved versions reloaded by Barlow , but don't expect another firing out of the case at full-tilt, if that!

You really need that 68 to 72gr case capacity...and a 34" barrel with a tail wind. You can always cheat a little and use it under favourable atmospherics only, long throat the chamber so the you use as much of the neck as possible, keep barrel twist to a minimum, use the thinnest brass cases possible, anneal every reload...just have to be careful you don't find yourself shooting from a bench for groups.

Tim, I am with Alan on the 300 WSM. This case gives you a very efficient burn with the shoulder angle which was some of the theory behind Ackley Improved cases. This projectile was probably marketed to the US shooters who own a lot of Winchester 300 magnums. So in terms of efficiency at 2600, (obviously with the energy limit a consideration) I would be looking at a cartridge that would minimise the air gap so the projectile was sitting on top of the powder at the junction of the neck and shoulder of the case. I would also be looking at cases that give this speed with the widest range of powders to try, so you can refine the efficiency.

I stand corrected but only two cases fit this criteria - the WSM and the Winchester 300 Magnum. The WSM is popular in Britain maybe because they are subject to energy limits on their ranges. I'm sure the Brits would not miss a beat.

The range of powders include: IMR 3831, IMR 7828 ssc, VVN160, AAC 3100, HOG US 869, & HOG Hybrid 100v for the 300 Magnum; and for the 300 WSM : VVT N560, MRP, HOG 4831, HOG Hybrid 100v, IMR 4350, ACC 4350, Ramshot Hunter, Reloader 19, and Magpro.

Someone with "Quickload" could refine these powders a little better in terms of load and case capacity. But I think the WSM has its nose in front at this speed and because of a greater range of powders that are suitable.

I would conclude, by asking you which cartridge would most suit your action?



Hope this helps.

David.

David,
I have a Barnard mag action on the way and some 300 saum brass.
Maybe projectiles could be an issue as it looks like no heavy 30 cals available at present.

Tim, Stick with your first idea, that's why I let you buy the 7SAUM brass.
Geoff

Geoff's point makes a lot of sense.

Dave,

The LoadData velocities are generally much lower than what we get. For example the fastest load listed for 284 Win and 180 Bergers is less than 2700 fps! So I have no doubt that the 300 RSAUM would do 2600 with the 230s easily.

However, with the likelihood of 3500 ft-lb becoming the practical limit for F-Class, then 7mm makes more sense. If I was Tim I would only go with 30 cal if he wants to do something different, which is part of what F-Open is about. There's something about launching those big 230 gn bullets that appeals to many of us I think .

Alan

My 180 bergers are going 2950 fps in the 7mm saum, in nsw you could run a 300wsm at useful velocities (28xx) with the berger 215/230gr pills making the exercise worthwhile (at the moment)

Have to agree with you Alan. I am aware that published loads are very conservative and for good reason as there are many people who read these posts, maybe newbies who do not post and who do not understand working up a load to maximum pressure or that their barrels maybe longer and faster than the company’s test barrel. But like BC’s and bullets that are different, you have to find a starting point. You may start will the highest BC bullet and work down to you find the most efficient for your rifle, but you have to find a starting point for powders too if you don't know them and an efficient vessel to shoot them in. For the purposes of discussion, Tim's other caveat was the energy limit.

The commercial figures are still good indicators of burn efficiency at certain speeds for different cases if you do not have a pet load for something new, not that we can actually get more out of them. The posted SAUM figures don't make the 2600 criteria. But the 300 WSM and 300 Win Mag do more easily with similar powders and a greater range of powders. If you have more powders recommended for a particular velocity, for a given case, it also gives you a greater buffer in testing while looking for more efficiencies. I just returned to Seddo, his “Quickload” program, and this is the sort of program which can refine your hunt. Otherwise you have to suck it and see or find someone with first hand knowledge in the area you are working. I was hoping some readers would volunteer some loads.

While some cases can be capable of much higher speeds, I am also keen not to punish the brass, and I feel the recommended manufacture’s loads are a reasonable indicator of this. You can see the subtle differences in performance in case design from standard to improved or like the subtle differences with the Shehane from the standard 284. So as a general starting point, the powder velocity recommendations are a good safe guide for burn efficiency. You can top up of course.

The other thing I have been working with, with a couple of shooters at the moment, is the underlying harmonics when comparing negative, neutral and positive compensation. This burn efficiency and the position of the peak pressure is a big influence on accuracy and relates to case design. So the raw speed is not really an issue in my mind, but burn rates accuracy and precision are. The range limits being adopted will mean shooters will have to rely more on skill in developing loads and interpreting conditions rather than by brute force. That means hunting and analysing more combinations. Nothing like changing the goal posts and having to adapt to keep your mind ticking over.

Of course differing perspectives make it so enlightening and interesting. We never stop learning.

Having a few unchambered 6mm's and 30 cals in stock, I have to wear them out first and I am just happy to shoot these days. I am aware of their deficiencies compared to the 7mm. Just have to improve other skills to match the 7 mms if I can, but more than happy to enjoy the company. David

Hey Geoff,
I'll try not to do anything irresponsible with the brass
Maybe the idea of moving from a 7mm to a 30cal will be similar to the move people made from the 6.5 284 to the straight 284??
After Mr Fairburns recent performance there might be a few open shooters looking at a 30cal with just a bit more go than a 308.

Most shooters using 230gn Bergers in their WSMs are getting 2830 up to 2950 fps, so with a RSAUM being only slightly smaller, I wouldn't think that 2600fps would be too hard.
I have been thinking about some sort of cartridge to shoot the 230s out of, but not wanting something as big as a WSM case, so either a 284 or SAUM might interest me as well. I wasn't so much after better wind drift than 284s, but something which might be less affected by atmospherics on ranges with big hump, hollows and mounds.
Come on Tim, you are a big red blooded bloke, build a big fun toy. No need to worry about energy limits at the moment unless you travel up to QLD or down to Victoria.

Hey Rod,
That's 170 pound I weigh NOT KG
So many guns to build and not enough time!(or was that funds)
Because of the energy limit in Belmont and other ranges I won't build something that wouldn't comply as I like to travel and shoot at these ranges.
Even formula 1 has restrictions, this just means you have to think outside the square while inside the square