Originally Posted by jwp475
No point in going with a 300 Jarret over a 300 RUM. No case can give more velocity with less powder unless you run higher pressures. No way around that and add to the fact that a Jarret case has to be formed and it is a no go for me.
Jwp said it best !!!! There is no free lunch. Case design can give you a better/
more consistant burn rate (better Standard devations) making it more accurate
but pressure and time gives you velocity.
Before It was called a Jarret the smiths that were messing with the 8 mm case
called it a super 30.
I looked in to it and found that a 300 Weatherby was its balistic twin so I went
with the 7mm/8mm (Now called the 7 STW) sizing and fire forming was not a
problem but there was no advantage over the factory 300 Weatherby mag.
The Jarret/30 super is not more efficient Just smaller in case capicity (About 10
to12grs meaning you must use faster burning powder (More pressure)to get the
same velocity,s This also shortens case life.
With lighter bullets (130 to 150) its not far behind the RUM but with heavy bullets
180 to 240gr there is no contest. If you intend to use the 200 or 210 gr bullets
this is right up the 300 RUM,s alley.
I have the 7 STW and the 7 RUM and the Rum has 12 % more velocity and energy
than the 7 STW but I still like shooting it and hunting with it.
I use the 140gr bullets with the STW and 160gr bullets with the 7 RUM at almost
the same velocity.
And as far as belted cases the only negative thing is that they use up case capicity
for the same size case body(.532" belt on Jarret and .546 case body on the RUM.
Your question was a good one and I think everyone answered them very well.
"BUT" if you want a Jarret you should build it and enjoy because thats what custom
rifles are all about.(Build what you want not what,s popular.
J E CUSTOM