Quote:
Originally Posted by jaredp
I find that seating depth is monumentally more important than charge weight. Get close to your lands first.
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While it is usually much easier to find Good Loads with the bullet close to the lands most Saami and many Wildcat cartridge designs do not lend themselves to seating close to the lands. As well case capacity is usually too small or two large to get an optimal case fill of 95 to 100% without compression. As well COAL is usually over Saami Max so they will not fit in magazines of most rifles that they are chambered in. A close examination of the pictures I posted, with the 40 V-Max seated in various 20 caliber cartridges, and many loaded with RS X-Terminator as per Ramshot pressure data will show this.
The 204 Ruger is a prime example of this with close to 0.300" Jump to the lands with 32-40 V-Max bullets seated to 2,26"OAL. The overbore case required this design, much like Roy Weatherby's, in order to even out the pressure curve and it will run the 40 V-Max to 3700 fps and still remain within the Saami Pressure limit of about 58,000 PSI. It has 0.100" FreeBore and a 1 degree 30 Minute Throat angle.
The 20 Tactical is a 223 rem case with the OAL shortened and shoulder bumped back in an attempt to get a longer neck, like the 204R, and have the bullets fit in a Saami Standard 0.226" magazine. The FreeBore was reduced to 0.045", in an attempt to reach the lands with the v-Max bullets, but the Throat angle was left the same as the 204R. Then in an attempt to get the case to hold a similar amount of powder the case is blown out at the shoulder by about 0.014". This actually resulted in a case that holds about 0.7 grains less RS X-Term behind the 40 V-Max but can only get 3700 fps by increasing the pressure to 63,000 PSI. Accuracy is not good, especially in a 1/2" twist barrel until these pressures are reached. Here is a kink to a discussion by some of the boys who gave me a hard time on this site. Notice the confusion???
http://www.saubier.com/forum/showthread.php?t=28859
My 20 EXTREME is designed to reach the lands with the 32-40 grain V-Max bullets, seated properly in the neck and still able to fit in a 2.26" Magazine. The case capacity is optimal for a wide range of bullets and powder to get 95 to 100 % case fill even including the 55 Berger. It has accuracy nodes at 3500 fps with a 95 % case fill and 3650 fps with a 100 % case fill with the 39/40 bullets using IMR 8208. It will run the 40 V-max to 3700 fps, on a hot day with about 60,000 PSI as estimated by PR expansion, Primer flow and Quick Load.
After about 7,000 rounds my original 20 EXTREME barrel was getting washed at the throat so that my groups were getting more near 1/2 MOA than 1/4 MOA. I got David Henry to run my Minimum Spec Reamer in 0.170", which is the difference between a 222 Rem (20 EXTREME) shoulder and a 223 Rem shoulder. I now have a 20-223 EXTREME that has 20 EXTREME dimensions but is 0.170 " longer and about 1/2 way between 223 Saami Minimum and Maximum chamber dimensions at the 0.200" Base datum. This is a bit bigger than the 20 Tac and 20 Practical which measure between 0.374" and 0.375" at that point. However the shoulder remains in the same spot and remains the same dimension as the 223 Rem new brass. No bumping of the shoulder and no fire forming, like the 20 Tactical, and everything fits with a nice low pressure node and a High pressure node that is very similar to the 20 Tac with Term.
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This target shows the 40 V-Max with X-Term at the low and high nodes in the 20-223 EXTREME. It also shows a pressure ladder shot with RL 10 X and the 40 V_Max that is near Max at 3509 fps as primers are flowing 0.0025" and brass is fire formed at the base much the same as the 24.0 grain load of X-Term.
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H 4895 seems to be near Max as shown in this target with Lapua M and Winchester brass running neck and neck. The Winchester brass always seems to shoot best by a slim margin although velocity is down. Will have more on this later.
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