Thursday, December 05, 2002

My sub-sonic .30 Herrett project continues apace. Of course I have to do a dangerous thing, extrapolate data from the .300 Whisper to the .30 Herrett for the 200 gr. bullets. After much hand wringing and such I swagged it and picked 13 gr. 2400 for the 220 gr. Sierra Matchking. That tumbled.

Ok, the books show the .300 Whisper 1-10" twist barrels shooting the 220s ok but evidently that is wrong. So... I go back to my local dealer, er supplier, er, well you know what I mean. Anyway I go and buy a box of Sierra 200 gr. Matchkings. As mentioned earlier I intend to seat them "backwards". Here they are compared with the "standard" (mine) 130 gr. Hornady SSP load. Since I dropped 20 gr. in bullet weight and want to stay below the speed of sound I also dropped the powder charge by 2 gr. I've yet to chronograph these though and will report speeds when I get the chance.

There are a couple of things of note here. First, the seating die is left the same when seating all loads. It may not result in the most accurate ammo but it works for now and saves me problems. I can adjust how far off the lands the varying bullets are later, IF it is worthwhile. However, as a result, the 200 seated backwards and the 130 Hornady transition to the ogive at about the same point. So does the 200 seated forwards! Will this actually help? We'll see.

Second, the 200 seated backwards has a big flat meplat just like the LBT style bullets and looks like a long truncated cone bullet.

As I mentioned a couple of days ago, the reversed bullet is supposed to most closely approximate a water droplet which is supposedly the most efficient sub-sonic shape.

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