Barrel Twist

[icebones]

The process of matching barrel twist rate with the right weight bullet is, in my opinion an art form,

rule of thumb is, faster twist for heavier bullets. basic stuff right?

my question is, does anybody make a chart of refrence for bullet weights and twist rates? because it would shure come in handy...

im buying a .300 magnum rifle with a 26'' bbl and a 1-11 twist.
ive never hand loaded .300mag before, anybody know the "ideal" bullet weight, this rifle will be used for target and competition only, so i dont need any hunting bullets. i need only accuracy and consistency.

 

[taliv]

in my opinion an art form

if by 'art form' you mean, 'well-accepted math formula that nearly every ballistic calculator includes' then yeah

 

[icebones]

michelangelo used a paint brush and canvas

i use a rifle...

is there an on-line ballistic calculator, or a formula you know of?

i really dont feel like loading several lots with diffrent bullets for the trial-and-error, shoot and see which one works best. ammo is too high and my shoulder wont feel that well the next day...

 

[brian923]

1. twist really deals with bullet length, not weight.

2. best to go with reputable bullet makes, such as berger, hornady, sierra...
you can also go with bullet smiths. i dont really no of any, but i do know thatthere are guys that will hand turn you bullets, to your exact specification. your talking alot of money, but if you are serious, and want to keep up with the big boys, this is an option.

3. why do you want to go with a 300 magnum? (curious to which one, and why?) how far do you plan on shooting? might be easier to do it with a 6.5 something... expessially if you are not going to use it to hunt...

edit: to your second post...

every bullet is different. every rifle barrel is different. you WILL have to painstakingly go through many formulas to figue out what works and what dosent for YOUR rifle. if you dont, your wasting your time. (heres is also why i ask about a 300 magnum) ballistic calculators and formulas can help narrow your seach, but it wont end it!! it merly gives you a strting point, just as easily as does a good reliable reloading book.
brian

 

[taliv]

google "greenhill formula"

 

[Jim Watson]

Problem is, half of them are based on the Greenhill formula which was developed in a day of blunter bullets and lower velocities. Using it means extrapolating way outside the range it can be depended on.

Best thing to do is to go to some of the bullet and barrelmaker sites and see what they recommend.

Berger says an 11 twist is good for their 210 gr .30 cal VLD.
Lilja says an 11 twist is good for up to 200 gr .30 cal.

I'd try 190s to start.

 

[USSR]

A .300WM "used for target and competition only" will typically use 190 - 210gr match bullets. Your 1 - 11" twist is perfect for those bullets.

Don

 

[icebones]

now that i think of it, i might be tempted to use that rifle for pronghorn out west, its a little too big, but its the only decent long range rifle i will have with me.

i usually load Nosler or Hornady bullets for my larger caliber rifles.

mainly 7mm and up.

i was thinking 168 or 178 grain hornady match bullets.

the shooting range is cut right through a forest, and there is thick woods on the sides and downrange, the trees help break up the wind, so wind drift really dosent come into play with normal weather. the range is marked out to 550 yards, but the main berm is about 720, according to my rangefinder.

any reccomendations for powder?
i dont have a loading manual handy, but i use IMR4831 and Hogdon H870 in my 7mm mag with good results. it seems to like IMR powder the best though.

 

[brian923]

is your 7mm rem mag not a good shooter? it should reak haveck on paper targets, and pronghorn alike?!?! no??? 7m bullets seem to be the sweet spot when it omes down to long range performance. more bullet frontal area than a 6.5 mm bullet, and better B.C's than the 30 cal counterparts.

i am in the midst of building a 7mm rem mag switch barrel savage. .308 winchester is the other cartridge i have for it right now, but id like to add some more barrels to it in the not so distant future.

at extended ranges, with the lighter bullets, i dont see 300 win mag being to big for long range shots. maybe use a lighter bullet that dosent fragment. something that would go shraight through, without blowing the thng up, and you should be good. (i think, i have never been hunting for pronghorn, and i dont have a 300 win mag.)

 

[icebones]

yeah my 7mag shoots like a house on fire, ive killed deer, varmits, targets and steel plates with it. but my handload for it pushes a 120 grain nosler at over 4100 FPS, as you could imagine, it shoots like a laser. and drops whatever you hit in its tracks. that nosler is plain nasty at closer ranges, and every deer i have ever taken was a broadside or near broadside shot. my 7mag is also fun to vaporize water jugs at 500 yards too.

but im leaving it, and all my other guns behind

you see, im going to be spending the next several monts in sunny Texas, and i was planning on spending a part my enlistment bonus and salary on a sweet new McMillian rifle, and a motorcycle. i just wanted one in .300 mag, because well, why not?

after i get out of basic and A-school, i can purchase my personal weapons and bring them on base, they have to stay in the base armory with the others, but only I have access to them, of course. this only applies if i choose to live on base though.

also i was planning on signing up for the USAF shooting team too.

 

[brian923]

hey, thats a good enough reason for me.... and thank you for your service. i hope that you can find the right rifle and ammo. i have always wanted a micmillian stock, but i just cant afford one.

you must do one thing though.... POST PICS!!!!!!
have a good one, and be safe, brian

 

[GunTech]

It's not the weight of the bullet, it's the length. Jim Watson is right about the Greenhill formula. It was developed around round nosed flat base projectiles and not for modern spitzers. You want to calculate gyrostability - probably using McCoys formulas - with a range of around 1.2-1.4 t cover all possible atmospheric conditions.

See http://www.eskimo.com/~jbm/calculations/drag/drag.html

Lilja has some guidelines. They use weight, so the chart is really only for lead core jackets bullets. Monolithiic copper bullets for example require a faster twist due to the lower density, and hence length for a given weight.

http://www.riflebarrels.com/products/caliber_twist_rates.htm

For your application, you should be less concerned with weight and more so with BC. In general, this means a heavier bullet, but not always.