Yeah, the SAAMI spec of 1:10.GasGuzzler wrote:It does look like it settled. 150gr is pretty heavy. Is the Mini30 a 1:10 like most 7.62ARs?
Still no answer from the seller on diameter and they're about ten days behind on getting stuff out so I bet I'll be waiting another week. In the mean time I'm looking to over-spend some more by buying an optic set up.
When it comes to a cast bullet, with any cartridge, bullets are typically heavier because of the effort to fill the features of the chamber's throat. More lead up front, more lead is needed in the back. Without adding the lead to the back to balance what was added in the front, the bullet is extremely unstable. A lighter lead bullet, not filling the throat's feature is a failure from the start.
The simple Greenhill stability formula determines a minimum velocity at which stability is lost. It is based on bullet length rather than bullet weight. A typical 123-grain bullet becomes unstable at 692 FPS and the 150-grain cast at 596. I'm more interested in how stable a bullet within its usable velocity range, a factor that my ballistic software evaluates based on a number of parameters. A factor of 1.5 is marginal, 2.5 becomes usable. The 123-grain has a factor of 4.767 and the 150-grain cast, 6.889. The heavier bullet is 31% more stable than, the lighter.
Here are the ballistic tables:
123-grain
TLC313-150-RF
[hr]I've been meaning to mention something I tried with my Safety Scale. There was a topic about a YouTubers magnetic modification. I have never had a bad oscillation problem but one day a relatively large allen wrench ended up laying near it and I happened to notice how quickly the scale stopped moving. I thought the pan must have contacted the wrench but it didn't. I measured a couple of drops and it just halts. Moved the wrench away it went back to the little wiggle as it settled, so now the wrench stays put with the short, curved end under the pan. It must be the field between two metal parts that does it, without going through that fellow's mods. You can see the wrench in the appropriate spot in the first picture.
My bullets are less than a penny with a 2¢ gas check. So, round it up to 3¢/bullet. If this works out, I can send six downrange for the cost of one PPU. These rifles are like feeding a large dog! Since the NV project started, I've sent 237 rounds downrange! This is also why I wanted to move it to the Load-Master and use a brass catcher on the range. The cast will save $17 over jacketed for every 100 sent down range. With the steel targets extended down my range, I could shoot 100 rounds in a few minutes just messing around.
If there is none left, I lived longer than I thought and it all went to the cause.
