I've been searching on the internet to see if I could find any information on how much a bullet looses it's initial rotation rate over distance.   I've not had much luck.

What I'm considering is if an initial bullet rotation rate just stabilizes a bullet over a long distance would the bullet loose enough rotational rate for it to become unstable.

Anybody have any information on this?

Thanks.

B'duckie

Bobduck wrote on Dec 18^th, 2014 at 12:30pm:


Mathematically, if a projectile is statically (gyroscopically) stable at the muzzle, it will remain statically stable.

Here is the reference: (You need to Login or Register to view media files and links).

JackHughs

old-win, what are the weights of your Pope 32-40 and the pointy bullet? I have two Pope 32-40 molds and they both throw 193 Gr bullets. The length is 1.000" Pope must have been fussy about this as I have had the opportunity to measure 10 or 12 of them all nose pour and the Blocks are all 1.000" long. I bought a few years ago some Pope style nose pour molds from Saeco. They were good cavitys but I disliked them because they were cut in a two or more cavity mold block and the handles were 10" Long or more. Very clumsy and tiring to use. I traded one to a friend that was interested. He reported that he got heavy tipping and once in a while a bullet flat sideways AT 200 Yds. So I measured a bullet and it was 1.050 long and he reported it cast 210/209 Grs. I offered to correct it by facing off the base. So did it in a lathe with the bore trued up. Now cast 195. Grs and was 1.000" long. He reported that the tipping was very slight and the flat sideways holes were gone. I know that for many the Greenhill formulae is supposed to be the way to define Bullets to Twist issues but I am not sure all is explained or considered there. Just my thoughts and experience with this issue. HTH Regards, FITZ.

I had an interesting experience several years ago at a 600 yd BPC match at the Paul Bunyan range in Puyallup.  I was pulling targets for a new shooter who was shooting a borrowed Italian Sharps.  The target backers were corrugated plastic.  The shooter was initially having problems getting on paper and when he did the first shot resulted in a loud CRACK.  Scared the heck out of me
Several of the next few shots did the same.  Those bullets were impacting the target so perfectly perpendicular that you could count the grease grooves.  They eventually stabilized and he shot a acceptable score. 

Jack

Old-Win wrote on Dec 18^th, 2014 at 6:52pm:


Will you tell us your method for lapping out a brass mold?

Thanks,

JS

OLD-WIN, tell me about your Mos mold. A few years ago with xxgrampa we rounded up a bunch of shooters that wanted Mos to make a production run of Pope copies. I provided diameters and lengths from my Pope molds in 38-55, and 32-40. I ended up with one of each. To my disappointment they came cut into (I think RCBS or maybe
SAECO blocks) BIG! HEAVY! BIG HANDLES. I am not sure about the 32-40 blocks I may have loaned or sold them Still have the 38-55 here in my book shelf beside the computer desk. Never cast a Bullet from either one. Being honest, it never occurred to me that the Blocks would be anything other than Lyman single cavity size blocks. I really HATE big over size molds. Tiring and slow you down and tend to make you quit casting sooner than you should.
My fault, I never asked xxgrampa. Just goes to show you gotta ask. What configuration is your 32-40 Mos mold? style
flat nose? Tapered nose to base? Nose pour? My 38-55 that I still have is a base pour. Again beautiful cavity. I am surprised that your 32-40 at .980 Long still comes out to 192 Grs. My Pope is exactly 1.000" and it is .193/.194 Grs memory here. As far as the question about lapping out your brass mold that was absolutely the best procedure. I have found that trying to work on the inner cavity details usually results in a mold block set that is put aside to be re-machined into some thing bigger because it has been bitched up inside. Well a little long winded here. HTH Regards, FITZ.  

OLD-WIN, Just a thought about your bullet weight difference. Grease Grove size? Ta-Da* FITZ.