J E Custom
Well-Known Member
There will always be a difference in opinion on twist rates and groove counts, so when choosing, you have to use the best for your needs.
I am not an expert, but like so many on this site I do have some experience with grove count And I will share my thoughts and beliefs.
Starting with the heavy bullets (375,416 and 458) I have found that a 8 groove barrel engraves the bullet better and has enough grooves and lands to start the big/heavy bullets rotating without any jacket shearing.
The more common groove count is the 5 or 6 grove and it works well for the intermediate bullet dia/weights. (6mm to .338 or.358) with reasonable velocities. The thought behind the 5 grove is that there are no lands opposite of each other and that It should engrave more accurately. I have found no real proof of this but it does sound logical.
The 3 groove design is an attempt to increase barrel life on ultra high velocity bullets 3800 ft/sec+
and does so by increasing the land width so it has more lead width, slowing the throat erosion. However, this comes with a cost. IT is hard on this jackets and requires a heaver jacket to withstand the extreme starting speed and land width without deforming or shearing the jacket causing poor accuracy. with the correct bullets the 3 grove does work and seems to increase velocity a little.The 3 grove has the same function(No land has an apposing land).
I have had very good luck with all grove designs If used in the right application and with the right bullet.
If you are not sure about twist and grove count, Talk to your barrel maker and ask his opinion
based on your cartridge, bullet weight and velocity. Also the number of rounds you intend to put through it in its lifetime.
Hope this helps
J E CUSTOM
I am not an expert, but like so many on this site I do have some experience with grove count And I will share my thoughts and beliefs.
Starting with the heavy bullets (375,416 and 458) I have found that a 8 groove barrel engraves the bullet better and has enough grooves and lands to start the big/heavy bullets rotating without any jacket shearing.
The more common groove count is the 5 or 6 grove and it works well for the intermediate bullet dia/weights. (6mm to .338 or.358) with reasonable velocities. The thought behind the 5 grove is that there are no lands opposite of each other and that It should engrave more accurately. I have found no real proof of this but it does sound logical.
The 3 groove design is an attempt to increase barrel life on ultra high velocity bullets 3800 ft/sec+
and does so by increasing the land width so it has more lead width, slowing the throat erosion. However, this comes with a cost. IT is hard on this jackets and requires a heaver jacket to withstand the extreme starting speed and land width without deforming or shearing the jacket causing poor accuracy. with the correct bullets the 3 grove does work and seems to increase velocity a little.The 3 grove has the same function(No land has an apposing land).
I have had very good luck with all grove designs If used in the right application and with the right bullet.
If you are not sure about twist and grove count, Talk to your barrel maker and ask his opinion
based on your cartridge, bullet weight and velocity. Also the number of rounds you intend to put through it in its lifetime.
Hope this helps
J E CUSTOM
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