First I must say this site totally rocks. Long Range Demon TacKac (LRDT ) gets major Kudos for his excellent post. As my existentialist guru is trying to teach me (and LRDT points out), you canít have a meaningful dialog without precise definitions.
I got flamed off another site for asking this exact question Ė they were unanimous Ė no shooting over 300 yds. ****, I was taking several deer a year with my cheapo .243 win at 350 yards with my 87gr reloads. It got boring. I was winning the 500 yard silhouette contests at my range - with my cheapo 30-06 (165g BT) Ė and we were free standing Ė no support, no bipod, no bench. One guy could hit the pig 50% more often than me (using his custom .243 with a bull barrel) Ė but he rarely had the momentum at that range to knock the pig over. The two guys with 300 mags ( on win, one weatherby spayer) rarely hit the pig. I attributed this to anticipation of kick.
Me bad. Range Iím looking at is to optimize the gun for 750 yds. Not ultra long range, but definitely long range. Itís for use at my friendís ranch outside GF Montana Ė which is windier than the windy city. The 5 points on his ranch donít let you get closer than 500 yds very often. Sometimes I can sneak to within 350 yds, but I donít have time to use a rangefinder (when less than 400 yds).
Major Kudos to Kirby too. I would much rather have a barrel from my buddy Daniel Lilja. Why does everyone miss the major point that a 1:15 twist Lilja heavy barrel will give me outstanding accuracy with a 125gr bullet?
Numbers are boring Ė take a look at my graphs at
300 RUM vs Kirby Mag
also look at :
7mm vs 300 vs 257 Kirby Mag
Kirbyís gun does win vs the 300 RUM, but not by huge margins. The graphs show the 7mm the best perf. I think with a custom bullet the 300 RUM would do much better. But the graphs show out to 750 yds no meaningfull difference. I had to go to 1000 yds in the drop so you could even see a difference.
I made the graphs with Shoot http://www.ballistics-software.com/
Ė kinda crappy software but itís free (and forever if you write a simple registry modification program [img]images/icons/smile.gif[/img]
Sorry Kirby, Like GW I have AADHD (http://www.adult-adhd.com/
) (and dyslexia) so I skipped all those boring numbers u spent so much time on. I did notice your time seems way off tho.
Budget limit is about $2,000 (not counting glass). ( I can pick up a used 300 RUM for less than $500 leaving me $1,500 for upgrades)
RBrowning writes (hey, are u any relation to my great great uncle John Moses Browning?)
While b1g_b0re used the clasic "milk bottle full of powder with an asprin on top" approach, he didn't take into account the damnable effects of drag, therfore he used a light for caliber bullet instead of the more aerodynamic heavy for caliber bullets. If he had necked his case down to a 25 he would have been pretty close to what Roy Weatherby did in 50 years ago. It worked then and it still works today.
I think u have the analogy backwards. The physics is very simple. F = MA or what we want is A = F/M. Given that M is fixed, we are left with A is directly proportional to F. Force is just pressure * Area. Again, letís assume P is constant (a reasonable assumption given high pressure RUMs and Kirbys). Now F = P*Ar (Area), and Ar = pi*r^2 or F is directly proportional to caliber squared. Roy on the other hand did things the old fashioned way (he had no other option, living in the ice ages He used an ultra long freebore so he could increase P (increased freebore resulting in decreased accuracy and increased muzzle erosion). Roy was not after accuracy (despite his marketing department slogans)
But your right that bullet drag is proportional to the CUBE of V * caliber squared Ė this will be the dominating factor at long range.
As my charts show, there is little difference between the Kirby mag and the gun Kirby will build for me in all areas sans wind. Perhaps wind is what puts the Kirby mag on top.
So far itís Kirby vs. Kirby [img]images/icons/smile.gif[/img]
I need to find a better bullet to compete with Kirbys custom projectiles.
STL: writes b1g_b0re, lose the lightweight bullets and try a 190 to 220 grain bullet with high ballistic coefficient in that 300 RUM. If you can shoot it accurately - you'll have a top-notch long range slayer.
Iíll probably have Kirby rebarrel my 338 RUM to shoot 180 or perhaps 200 gr BTís. If If I need anything heaver than that, Iíll go with my 375 RUM or one of my custom 50 BMGs.
KEEP IN MIND Ė I do get shots at 4 to 5 pt Bucks at less than 400 yards with no time to use a rangefinder.
Roper rites (sorry, couldnít resist the phonetic alliteration) your barrel may not last past load testing that throat will wash out pretty quick.
Not true : with Kirby boring a tight throat with my dummy cartridge. You would get fast throat erosion given the factory throat and hot 125 BT loads.
Speedbump : dang, I had to redo all my charts with your awesome suggestion. If your data is accurate ( I dropped velocity to 3350 ) Ė Iíd say you have the winner. Check out the graphs at
7mm vs 300 vs 257 Kirby Mag
I own all the RUMS EXCEPT the 7mm. Maybe this is the direction I should go.