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Bullet selection and guns rate of twist formula Rate Topic: -----

#1 User is offline   Uncle Buck 

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Posted 06 March 2010 - 09:16 PM

I was talking with my gunsmith today and asked him about the 30 grainer's... He said you have to make sure the rate of twist is just right to stabilize the bigger bullets...I have been trying to find out the length of this bullet since I have a formula that I use to see if the rate of twist will work for any given bullet.

(1.) Measure the Length of a bullet in inches, then divide by the bullet diameter.

(2.) Divide 180 by the result of (1). (note the 180 value will always be a constant in your calculations for all computations)

(3.) Multiply the results of (2.) times bullets diameter. Round to the highest whole number for your rate of twist..


Here is one I just used to figure if my Encore 22250 with a rate of 1-12 will shoot Nosler 60 grain Partion bullets:


(1.) .752 divided by .224 = 3.35

(2.) 180 divide by 3.35 = 53.73

(3.) 53.73 X .224 = 12.03

So my Encore 22250 with a rate of twist of 1-12 should shoot the .224 60 grain Partiton well.


Formula Found in April 2010 Guns Magazine
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#2 User is offline   Uncle Buck 

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Posted 06 March 2010 - 09:21 PM

Berger Rep did respond back to me and told me that a 17 Center fire in a 1- 9 twist will stablize the 30 grain .17 cal bullet they manufacture..




Um will this ever end? Now I want to determine if one of the Speer Varmint 30 cal 130 grain bullets will stabilize and shoot in a 308 Winchester. I know better that it sure ain't no fox round...But how neat to pick off a woodchuck at 300 yards with a 308 Winchester and use a bullet that will fragment just like a .224 223 or 22250.
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#3 User is offline   Uncle Buck 

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Posted 06 March 2010 - 09:38 PM

This kind of explains twist rates for the curious:

http://www.eabco.com/TwistRate.htm
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#4 User is offline   DJnRF 

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Posted 06 March 2010 - 10:43 PM

Darn good info! Since I hadn't done it in so very
long I had forgotten the method. Also, I can't
seem to find my book. This will give me a good
bit of info to save to remind me if I have to
figure this again.
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#5 User is offline   model99er 

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Posted 06 March 2010 - 11:50 PM

View PostUncle Buck, on 06 March 2010 - 09:21 PM, said:

Um will this ever end? Now I want to determine if one of the Speer Varmint 30 cal 130 grain bullets will stabilize and shoot in a 308 Winchester. I know better that it sure ain't no fox round...But how neat to pick off a woodchuck at 300 yards with a 308 Winchester and use a bullet that will fragment just like a .224 223 or 22250.



UB,

Let's put it this way, I happen to know a feller that just loves 125gr Nozler BT's (loaded on the hot side) for Deer in his 300 Savage. ;) :D

If Bawana ever gets caught up on all his chores and current backlog of loading (including 222, 243, 270, and 308) for himself & me, I might then have the nads to ask to load 308 125gr BT ammo for both he and I, since we both happen have 308 Model-99's.

He did witness me using the 300-Savage 125gr BT's he loaded on two Deer the year before last. He was like a proud pappa watching that first one be lifted up off the ground a few feet then doing a nose dive in the dirt at ~150yds. :rofl: :lol:

Fortunately model-99's with their rotary mag design don't have a probelm shooting BT ammo like other levers do; I'm also fotunate that thanks to Bawana, I'm still setting on 5+ boxes of that ammo that I still have left. :o :D

Un-fortunately, on his "off-week", Bawana is either working on the Farm for his step dad or helping his Father-In-law run Dump Trucks or plow snow. Since I happen to hunt on their Farm rather often, I sure as hell ain't gunna complain too damn much. LOL :ph34r: :D

Besides, I really enjoy using the 243 and 300 Savage model 99's and this year will be the 1st year that I'll also be using my 270 Browning on Deer, so the 308 and 125gr ammo for it prolly will have to wait another year or so.


99er
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#6 User is offline   DJnRF 

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    'A little bit of knowledge is dangerous while a lot leads one astray from the intended idea.'

Posted 07 March 2010 - 08:36 PM

Oh, well! I probably shouldn't worry about things such
as this. In no time I will probably just have to settle
on only one gun to be able to hit anything anyway. I
will just then stick to a 75mm Pack Howitzer. I got
pretty good at adjusting powder charges when doing
the reloading of these rounds, and there has always
been a good choice of projectiles. lol
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#7 User is offline   Uncle Buck 

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Posted 08 March 2010 - 12:57 AM

Thanks to the kindness of my children I got three gift cards this Christmas...Went to Cabelas this week-end...Oh no.....there it was at clearance price because it was wrapped in last years sleeve... a 308 Win Prohunter Encore barrel Stainless Steel 28 inch fluted.. Now Encore is also giving away $50.00 bucks to so I had to buy it. When rebate arrives it will only cost $117.00, that the tax too..
Now I want to try to use this for chucks....with the 308 HP 125 or 130 bullets from Speer.. I wonder what a chuck would look like if when it gets hits with a 30 Cal 130 grain varmint bullet... Would it work the same as a .224 or would it mist the larger woodchucks like praire dogs??? I knwo the 308 Win is not a fox gun thats for sure... However it would be good to pop chucks on Windy days or when you wanted to shoot them at 300-350 yards...

Oh Oh I need one of 99er suggested golf carts for sure......
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#8 User is offline   DJnRF 

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  • Location:Peoria, IL.
  • Interests:Most everything these days can be stated as "formerly". Hunting, fishing, competition shooting, and many days/nights/weeks of camping or other field experience are now relegated to teaching, lecturing, and writing about. Former associate of Maj. Geo. C. Nonte, a firearms testing and evaluation firm that authored many books and articles on hunting, and firearms. The first writer for Shooting Times. All are now grouped into the field of survival, in which the knowledge, familiarization, and ability with all types of weapons are included. I still have to practice what I teach, lecture on, or write about, but, alas, that is getting to be a real difficult thing. The ole bod doesn't take too kindly for much of that activity these days. (But, don't give me even a shirt button at 300 yds, or it's mine!)
    'A little bit of knowledge is dangerous while a lot leads one astray from the intended idea.'

Posted 08 March 2010 - 09:46 PM

View PostUncle Buck, on 08 March 2010 - 12:57 AM, said:

Oh Oh I need one of 99er suggested golf carts for sure......



I managed to pick up a Wal-Nut electric cart that they were
going to junk. I found that the original problem was that
the mounted battery charger had quit working. Instead of
getting someone who knew how to test for problems they
had one of their own people tear into it. After tearing
up the wiring to the controls they determined that is
wasn't worth fixing.

Repair of the wires are not a problem, nor is the charger
a problem. (It is fixed already) I intend to change the
steering method, put on four larger mcy wheels from an
old style Sprint, and have already started to make a
change in the gearbox. This should give me a nice,
quiet, light, and fairly fast type of ATV. The seat
box is large enough to handle two batteries, and to
add a mcy alternator will help to charge them while
running. I figure I should be able to get about
five hours run time that way before needing a full
recharge. I am kinda looking forward to those
'lazy' days of field hiking.
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