On Wed, 23 May 2012 21:42:10 -0400 gene heskett <ghesk...@wdtv.com> wrote:
> Greets all; > > Does anyone have any links in their bookmarks that might give me a > 'rule of thumb' at least for BP nipples using #209 primers? I have > the 2nd one at the "all the cylindrical work done" stage, and so far > a single #74 drill (0.0235") in the center of the end of it, which is > obviously smaller than a factory nipple has, with that one being > about a #67, and 2 more that same size on the sides so they blow out > thru the circular gap between the breech plug and the end of the > nipple. I'm out of #67 and #68 drill bits with only 2 indexes, > chinese of course & only 1 out of 3 actually sharp. So instead of > drilling one hole all the way thru, I thought I'd drill 2 all the way > thru giving 5 .0235" vent holes. > > I tried the first of these nipple designs out Monday and got a 2" > group, but with 5 #68 holes, the blow back is pretty strong, backing > the striker up and lifting the primer plumb clear of the nipple with > only a 50Gr load of BlackHorn 209. That of course lets out quite a > bit of gas, none of which seemed to get to me although there was > quite a cloud of it the breeze carried into my face for a couple > seconds. > > I've considered cobbling up a latch for the striker so that when it > comes down, its snap locked, holding the primer in place, requiring > the latch to be released to cock it again. > > The TC Black Diamonds are not exactly a closed breech design, so the > latch it closed idea is a good one, just need to work out the > details. That's what you get for something that wally sold for $200 > several years ago, but it still shoots better than the $600 Omega > they just put a new barrel on since the OEM barrel was damaged from > the gitgo. It shot a 3" group Monday with the same load the Black > Diamond used for a 2" group, but hey, that is about 3 feet smaller > than it did OOTB with the damaged barrel. > > Anyway, this is about flash hole sizes. > > Does anybody have any comments/links to offer? > > Cheers, Gene You might take a look at the size of the two holes in a Berdan setup. Maybe start small and work up 'til you get reliable ignition. There was some information floating around a few years ago about some Berdan primed 7.62 x 51 that shot groups about half the size of the Boxer primed stuff. You get to balance the venting of small holes against the blow-back from chamber pressure. I think it is pretty empirical. Dave ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
