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Bullet length question (Read 6183 times)

RSW Frequent Elocutionist Offline Posts: 1188 Location: Arizona Joined: Sep 8^th, 2006	Bullet length question Mar 6^th, 2011 at 3:39pm	Print Post
	After running the numbers for my 32-40 through “CharlieDELL'S Rifling Twist Formula” excel spread sheet, I come up with a maximum bullet length of 0.97”. Bullet diameter .321, twist 1:4, MV 1,400fps. I have been shooting a Mos spitzer of 1.16” length for some time now with excellent accuracy (meaning I’ve won my share of matches with it) and the bullet holes in the target are nice and round. Seems to me Charlie’s formula may be on the conservative side as to bullet length for a given twist or am I missing something? Opinions?

	Randy W ASSRA 10211 - ISSA 125 There are indeed two Americas. Simply put, it is not the haves and have nots. The two Americans are in reality divided into those who do and those who don't.
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rustyrelx Senior Forum Member Offline Posts: 474 Location: Wallace Idaho Joined: Oct 9^th, 2007	Re: Bullet length question Reply #1 - Mar 6^th, 2011 at 8:13pm	Print Post
	1 in 4 twist is as fast as I've ever seen. Maybe your on to something.


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RSW Frequent Elocutionist Offline Posts: 1188 Location: Arizona Joined: Sep 8^th, 2006	Re: Bullet length question Reply #2 - Mar 6^th, 2011 at 9:13pm	Print Post
	1:14 sorry about that

	Randy W ASSRA 10211 - ISSA 125 There are indeed two Americas. Simply put, it is not the haves and have nots. The two Americans are in reality divided into those who do and those who don't.
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MAD MIKE Oldtimer Offline Posts: 655 Location: So Cal Joined: Oct 31^st, 2006	Re: Bullet length question Reply #3 - Mar 7^th, 2011 at 2:12am	Print Post
	When they refer to bullet length on those charts, if I recall correctly, bullet length was measured as a cylinder(no meplat or ogive),(hope I spelled those correctly). I'm sure that's printed on some charts. That's the way I remember it, anyway. ...MIKE...


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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Bullet length question Reply #4 - Mar 9^th, 2011 at 5:37am	Print Post
	With a .321" bullet at 1400 fps C. Dell's formula says max bullet length is .96" With a .321" bullet 1.16" long at 1400 fps C. Dell's formula says min twist is 11.6" With a .321" bullet .96" long Greenhill says min twist is 16.1" With a .321" bullet and 14" twist Greenhill says max. bullet length is 1.104" The C. Dell formula is for longer range slower bullets. Greenhill is for shorter range, the BPCR guys say. I would say that in the world of approximations, it's all pretty close. How close is your twist to 14", velocity to 1400 fps? joe b.


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John Boy Ex Member	Re: Bullet length question Reply #5 - Mar 9^th, 2011 at 8:43am	Print Post
	Crash, put this calculator into your references for twist rate calculations ... (You need to *Login* or *Register* to view media files and links) Here are some more JBM calculators ... (You need to *Login* or *Register* to view media files and links)


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RSW Frequent Elocutionist Offline Posts: 1188 Location: Arizona Joined: Sep 8^th, 2006	Re: Bullet length question Reply #6 - Mar 9^th, 2011 at 1:00pm	Print Post
	Guys - thanks for the feedback, it is much appreciated. John Boy: from those calculators, it looks like I could stabilize a slightly longer bullet than the one I’m using now. joe b: the different bullet lengths derived from the two formulas make sense if Greenhill’s formula is for shorter distances and Charlie’s formula holds-true for extended ranges, where the bullet is subsonic for much of its trip to the target. My current spitzer stays stable at 200 yards which is the only distance I really care about. I have never measured the actual twist of the barrel, it’s a heavy Badger that came on the rifle and is supposed to be 1:14. I’ll measure it so I’m know for sure. Where I’m going with my bullet length question is that I’m trying to tighten-up my groups a bit with this rifle by designing a sptizer bullet to more precisely fit the throat/leade. By knowing the optimum bullet length, I then have a starting point for developing the bullet design. Once I get the bullet drawing developed, it’s off to the mould maker. The 1400 fps (or slightly faster) is my intended muzzle velocity so the bullet stays supersonic all the way to the target. My actual velocity will be whatever is most accurate when I work up a load for the new bullet.

	Randy W ASSRA 10211 - ISSA 125 There are indeed two Americas. Simply put, it is not the haves and have nots. The two Americans are in reality divided into those who do and those who don't.
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Big Dave Newbie Offline Posts: 7 Joined: Apr 20^th, 2010	Re: Bullet length question Reply #7 - Mar 11^th, 2011 at 10:05am	Print Post
	The Corbin twist rate calculater gives 1.125 inch long and 225 grains for bullet in 1:14 twist barrel. This calculater seems to be working with my bullet configuration so far. The 190 grain by .980 length is working excellent in the 1:17 twist barrels. I made some for a guy with 1:14 twist, but do not think the weather has let him try them yet. Do not know if this will help of confuse. Good luck.


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RSW Frequent Elocutionist Offline Posts: 1188 Location: Arizona Joined: Sep 8^th, 2006	Re: Bullet length question Reply #8 - Mar 11^th, 2011 at 2:24pm	Print Post
	Big Dave Thanks for your input. The 1.125” bullet length (maybe a tad bit longer) is about what I think I will end up choosing but a longer nose spitzer since I intend for the bullet to stay supersonic at 200 yards. It will probably weigh a little less than 225 grains though. Your bullet configuration looks interesting. It appears to be knurled, correct? Do you lube it? If yes, do you dip lube, tumble lube or maybe you shoot it paper patched. Inquiring minds want to know

	Randy W ASSRA 10211 - ISSA 125 There are indeed two Americas. Simply put, it is not the haves and have nots. The two Americans are in reality divided into those who do and those who don't.
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Big Dave Newbie Offline Posts: 7 Joined: Apr 20^th, 2010	Re: Bullet length question Reply #9 - Mar 11^th, 2011 at 9:39pm	Print Post
	I knurl the sized (to weight) slug, then tumble lube them. The next step is to form them in the dies. The lube is sealed in the knurl as they are formed, and lubes the complete bearing surface. These seem to have no leading problem. The nice thing about my dies is that I can make some variations to the bullet. This helps make a bullet to fit a particular barrel / rifle fairly easy. The attached photo shows two nose shapes I am doing. On these 32 cal. 190 grain, the blunt nose is .980 long and the long is about .020 to .025 longer. The more I do with these the more interesting (sometimes frustrating), it gets. Dave


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RSW Frequent Elocutionist Offline Posts: 1188 Location: Arizona Joined: Sep 8^th, 2006	Re: Bullet length question Reply #10 - Mar 14^th, 2011 at 10:31pm	Print Post
	Big Dave Your bullet concept looks interesting. If you don't mind sharing, how do you knurl them uniformly? Also, do you breech seat or shoot fixed? Are your bullets groove diameter and I guess another basic question, are you shooting black or smokeless? Thanks for engaging in this dialog, it's appreciated.

	Randy W ASSRA 10211 - ISSA 125 There are indeed two Americas. Simply put, it is not the haves and have nots. The two Americans are in reality divided into those who do and those who don't.
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Cat_Whisperer Frequent Elocutionist Offline No 1, 9.3x74R Posts: 3877 Location: Mountains of Virginia Joined: Apr 17^th, 2004	Re: Bullet length question Reply #11 - Mar 14^th, 2011 at 10:35pm	Print Post
	GOOD lookin' bullets! How do they shoot?

	Cat Whisperer (trk) Chief of Smoke Pulaski Coehorn Works and Skunk Works Drafted May 1970, Retired Maj. U.S.Army assra #9885
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JLouis Frequent Elocutionist Offline Posts: 10625 Joined: Apr 8^th, 2009	Re: Bullet length question Reply #12 - Mar 14^th, 2011 at 10:52pm	Print Post
	Dave interesting concept please keep us informed on further testing and your results. J.Louis

	" It Is Better To Now Have Been A Has Been Than A Never Was Or A Wanna Be "
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Big Dave Newbie Offline Posts: 7 Joined: Apr 20^th, 2010	Re: Bullet length question Reply #13 - Mar 15^th, 2011 at 9:24am	Print Post
	Crash Landing Your bullet concept looks interesting. If you don't mind sharing, how do you knurl them uniformly? The photo shows my knurl tool. A slug that is correct weight is shown on the rolls. The top roll pivots down and the screw at the upper part of the photo is a stop screw to keep the knurl uniform. Also, do you breech seat or shoot fixed? We have used them both ways. Are your bullets groove diameter and I guess another basic question, are you shooting black or smokeless? They measure .322 diameter with my micrometer. They should work fine with black powder, but we have only used smokeless so far. Cat_Whisperer GOOD lookin' bullets! How do they shoot? At Joe's place, a 100 yard "home range" that is fairly protected from the wind, some excellent groups have been shot. Joe had purchased a 32 Miller and was ready to sell it because he tried all of the cast bullets he could find and the best he could get was over 1 inch groups. The first time with these he started getting consistant groups of about 1/2 inch. One of the guys did shoot a five shot group with a CPA 32-20 that was just under 1/4 inch center to center. These were with the blunt nose in 1:17 twist rifling. We have to try the more tapered as soon as the weather gets better. Good shootin, Dave


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