Bullet length

[sandersj89]

I want to do a little checking now that I have established the twist rate in my 243 is 1:10. I have been given this formula to check bullet weight:

 

THE GREENHILL FORMULA:

 

"The twist required in calibres equals 150 divided by the length of bullets in calibres."

1) Divide the length of the bullet in inches by the calibre to get the length in calibres.

2) Divide 150 by the number from #1

3) multiply the number from #2 by calibre to get the required twist.

 

But I do not know the bullet length of the two rounds I have been using so far, Federal 100gr powershok and federal 55gr vitalshok. I look on the federal web site has not helped so far, does anyone know where I can get the measurements.

 

I would also like the info for Norma ammo.

 

Thanks

 

Jerry

[Ronin]

Jerry

 

if you scroll to the bottom of this link http://www.riflebarrels.com/products/caliber_twist_rates.htm

 

you will see a table of twist rates / bullet weight.

 

It is pretty accurate (in my experience) and ive refffered to it when speccing barrels for "out the box" bullet weights.

 

Generally, you dont want to overspin bullets as this causes any manufacturing defects to manifest themselves in blow ups and or poor accuracy.

 

 

Your 10 twist barrel should be fine for 100grainers but i'm not sure about the 55's.

 

(I dont normally "do" 6mm's)

[duey]

Jerry

 

1-10 twist would suit slightly lighter bullets better, 75-95gr, 100gr generally do better in faster twist barrels 1-8, 1-9, but each rifle is different and some will cope with 100gr with 1-10 twist, so if it works don't worry use it.

 

Ian

[sandersj89]

1:10 is gtg up to 120gr'rs or 95gr in VLD's

Keep in mind that velocity will also play a factor...

308Panther

 

Thanks guys, I am going to get some Norm 100gr to push through it to compare to the Federal, will see how it goes.

 

Jerry

[sandersj89]

1:10 is gtg up to 120gr'rs or 95gr in VLD's

Keep in mind that velocity will also play a factor...

308Panther

 

Thanks guys, I am going to get some Norm 100gr to push through it to compare to the Federal, will see how it goes.

 

Jerry

[sandersj89]

Had a bit a practise session today and ran a selection of ammo through my 243 whilst Southerner was trying out some home loads in his AR.

 

The conclusion for the 243 was : 100gr shoot better than 55gr.

 

Of the 100gr

 

Sako, cheap but wont group.

Norma, not bad grouping

Federal, the best groups and I think I will stick with them.

 

Weather was not great but at 100yards I did manage to put three shots into just over an inch.

 

Brian shot very well, a corking group at one point that was near as it can be bullet on bullet.

 

Jerry