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Ballistic Stabilty Calculator
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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Elvis
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PostPosted: Tue Jun 21, 2011 11:29 pm    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

thankyou for that Pumpkinslinger you have just confirmed what I wrote when talking about structual integraty. I have yet to work out how a projectile can spin too fast for its own good if it is well balanced and holds together?
Gelandangan have you tried doing to your subsonics something along the lines of the ol .303 rounds that had aluminum etc in the front half of the projectile to promote tumbling???

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Ominivision1
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PostPosted: Wed Jun 22, 2011 2:44 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Elvis wrote:
If you round things off abit for ease of calculations a projectile doing 3000fps fired through 1 in 12 rifling is rotating 3000 times per secound which is 180,000 rpm. so its no wonder we run into issues at times.

Yup the numbers seem astronomical but in reality, the time to target is only a little more than one-tenth of a second.

-100 yards times 36 inches is 3600 inches
-one turn in 10" twist barrel---3600 divided by 10= 360 bullet revolutions per 100 yards
-1/9 twist--400 complete rotations of the bullet out to 100 yards
-1/7 twist--514 revolutions of the bullet out to 100 yards
The revolutions remains almost constant until the bullet stops. So at 400 yards the bullet in a 1/10 twist will have turned completely 1440 turns. The bullets do not rev up after firing and exiting the barrel but they have a constant 1 turn in whatever twist the barrel is and velocity will change bullet rpms. Now if the bullet was traveling through the air for a total time of one minute the total number of rpms would be the high numbers such as 200,000 or more.

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Last edited by Ominivision1 on Wed Jun 22, 2011 3:58 am; edited 1 time in total
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Aloysius
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PostPosted: Wed Jun 22, 2011 3:50 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Omi, I have a qsuestion:
"velocity won't change bullet rpms"
you mean that the rpm of bullets coming out of the same barrel but at different speed, are the same? In my opinion the lower the velocity of the bullet, the lower the rpm.
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Ominivision1
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PostPosted: Wed Jun 22, 2011 4:01 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Thanks for catching that Aloysius, I edited the post to "velocity will change rpms"

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Pumpkinslinger
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PostPosted: Wed Jun 22, 2011 2:10 pm    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Gelan, I'll have to nitpick again but the problem given in your example isn't that the bullet is over stabilized, it's that the bullets aren't designed to expand at that impact velocity. Again, that is a issue of bullet construction, not "stabilization". In the case of a sub-sonic .300 Whisper there may not be a manufactured bullet that will do what you want it to. You are compensating for the problem by trying to have the bullets tumble on impact but the real problem is still one of bullet construction/selection.

By the way, Hornady now has two factory .300 Whisper loads.

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Ominivision1
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PostPosted: Wed Jun 29, 2011 11:39 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Loaded up 100 /06 cartridges last night with the just arrived box of Nosler 125gr spitzer ahead of 57.5 grs IMR4831 with COL at 3.20" which is under Noslers recommended max. I headed over to a buddy's farm after work. Before sighting in for 200 yards, with a muzzle velocity chrony at 2900fps, with no adjustments to the scope, target picture is the results. After I sighted in the rifle, I got this rascal at approximately 125 yards. While I normally use my 22-250 for Pdogs, the opportunity was there and I took it. I think I will stick with this combination after these results. Very Happy



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1st Dog
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3006-200yards.jpg
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slimjim
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PostPosted: Wed Jun 29, 2011 7:26 pm    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Yep, looks overstabilized to me! OV1, shouldn't you be shooting more than 1-shot groups?!?

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Aloysius
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PostPosted: Thu Jun 30, 2011 12:15 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

slimjim wrote:
Yep, looks overstabilized to me! OV1, shouldn't you be shooting more than 1-shot groups?!?

and worse: overstabilized to the left while I was thinking more conservative... or is this a special round for grounddogs sitting left from the target? When they are facing you they might be on the right site you know... better hit 'm with a paintball first and give the real targets a red colour. Or was that one on the picture hit with a red paintball and now playing death?
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stovepipe
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PostPosted: Thu Jun 30, 2011 8:30 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

If a projectile comes apart leaving the muzzle, it aint over-stabilised, it's pushed too fast and CF rips it apart. I've heard both sides of the fence on over-stabilization. 90% of the feedback is there's no such thing. It's either stable or un-stable. And, gets upset most of the time going sub-sonic after being super-sonic.

I know some that zero a bit left @ 100y to compentsate for spindrift on RHT... out past 300y it makes a diff on some loads, so I've read, makes sense. I zero @ 200y + 0.5" left with the 300 and can whack man sized gongs @ 600y. I forgot the article I was reading on LR shooting about reading mirage, set up, etc. I think it was by Lazeronni.

I've had questions about when the projectile goes to sleep and settels down and how far out it'll stay stable etc. and since I suck at math and dont have a computer at home.....I emailed Sierra with all my load and firearm info. Even with less than factory velocities the projectile stabilizes @ 2100'/sec and stays stabilzed/super/trans-sonic to 1000y with my 300 and I aint shooting past 700y mostly....no worries. 1 call did it all. Yeh trans sonic ant the most stable speed range to be trying tgo hit stuff but whatcha gonna do...bullet shape helps there. Back to BOOM PANG!
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Ominivision1
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PostPosted: Thu Jun 30, 2011 9:08 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

stovepipe wrote:
If a projectile comes apart leaving the muzzle, it aint over-stabilised, it's pushed too fast and CF rips it apart. I've heard both sides of the fence on over-stabilization. 90% of the feedback is there's no such thing. It's either stable or un-stable. And, gets upset most of the time going sub-sonic after being super-sonic.

I've had questions about when the projectile goes to sleep and settels down and how far out it'll stay stable etc.

I agree Stovey, like my above load for the /06, it is just above what Nosler recommends for a minimum load but with the bullet seated deeper, its more accurate in my gun then with the recommended col. And like you said, a bullet is either stabilized or it isn't, can't be both or can it?

My question on that is before a bullet goes to sleep on its flight, is it considered unstable? Just a thought. Smile

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stovepipe
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PostPosted: Thu Jun 30, 2011 10:10 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Ominivision1 wrote:
My question on that is before a bullet goes to sleep on its flight, is it considered unstable? Just a thought. Smile

Nope- just restless. Try Somminex. Smile

And, no digs againts any of my brothes here that do all this math. I'm a little jealous as I dont have that mental capacity so I over compensate by over simplifying... Embarassed
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Ominivision1
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PostPosted: Thu Jun 30, 2011 10:21 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

LOL, ok Stovey but think about it, when you were a kid and pulled the string on the top, didn't it first start out wobbly? After a sec or 2 it became smooth (stable?). Just a thought. Smile

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stovepipe
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PostPosted: Thu Jun 30, 2011 11:03 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

Yes and....um...I don't think that's the same thing but I see yer point. That's why I contacted Sierra as I wasnt pushing my bullets super fast and wondered the same thing, they gave me the dope so....and only girls tops wobbles. Mine went straight up from the git go. Give it more yank!

And next time Kabong spits out a top at some paper I'll check fer keyholing. Razz
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Ominivision1
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PostPosted: Fri Jul 01, 2011 9:45 am    Post subject: Re: Ballistic Stabilty Calculator Reply with quote

stovepipe wrote:
..and only girls tops wobbles.



Haha Haha Haha Haha Haha Haha

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