4 vs 6 groove rifling [Archive] - Home of the 6.8 SPC - 68forums.com

: 4 vs 6 groove rifling

12-12-2009, 11:37 AM
can someone tell me the pros and cons between 4 vs 6 groove rifling i would appreciate the help with this info

12-12-2009, 11:41 AM
4 groove reduces pressure IIRC

12-12-2009, 11:58 AM
6 groove is cheaper for the manufacturer to build. 4 groove tends to lower pressure.

12-12-2009, 12:15 PM
wont higher pressure give better ballistic performance ?

12-12-2009, 12:29 PM
wont higher pressure give better ballistic performance ?

No. It's the land to groove ratio which is really important not necessarily the number of grooves. Anyway, think of it as increased friction on the bullet., so the bullet takes longer to leave the barrel and your powder burns earlier relative to the bullet's position in the barrel. That means less space for gases and higher pressure.

Juwst throwing in some numbers for illustrative purposes, these are not accurate and would vary by powder. If you had a barrel with more friction the powder would burn in the first 10" instead of the first 12". That means you cannot use the same amount of powder since the amount of volume is less. If you did, you'd get symptoms like blown primers, ejector swipes, etc. Since you can use more powder because it will burn over a longer time period you can load hotter and wind up exerting more force on the bullet overall.

12-12-2009, 12:42 PM
thanx for the info

12-12-2009, 01:28 PM
6 groove is cheaper for the manufacturer to build. 4 groove tends to lower pressure.
Six groove is cheaper if the button is already made to rifle the barrel, it's a one time investment to have one made to your specs. Most of the companies that made six groove barrels did so because they felt no need to invest in another button.

Most times, a four groove rifling will have a higher land to groove ratio, meaning there is less area for the bullet to have to squeeze through to go down the bore.

12-12-2009, 01:58 PM
Most manufactures (Shaw or Wilson)want to use 6 groove buttons because they pull through the barrel faster and easier, they last longer. 6 groove barrels can pull 60% faster than 4 groove so if Shaw builds 4000 4 groove barrels in a day they could pull 6400 6 grooves. Figure each machine is costing $60/hr minimum and they may have 10 machines. That is a lot of savings and why they push 6 groove barrels, also 10 twist is a standard 270 twist so YHM does not have to wait for a special button to be made.

This post relates to this topic as well.