How many groove barrel for 7mm wsm
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Broz
Well-Known Member
I like the 6 grove Harts or the 5 C Broughtons for a 7mm. Anytime I plan to use an high expansion bullet, best suited for long range hunting, I like more groves with less jacket scribing going on. I feel this will let the bullet hold together better when taking game at closer distances and also why I only use enough twist rate to effectively stabilize the bullet of choice. With all the 7's I have put together the Harts and Broughts have been very accurate to very long distances.
Jeff
Jeff
I am debating the merits of 3 groove vs. 5 groove. I'm hoping someone here can discuss the reasons for the differing number and how to choose which is right for for my application. I know guys win with all differing groove paterns and I could go with what I know will work but I keep hearing threads mention higher velocity with some 3 groove. So why not 3 groove vs 5R and is it common to pick up a few fps ?
The only real test of groove count is to first determine what the bore and groove diameters will be.
Second, what will be the width and shape of the groove that also forms the lands as well as the cross sectional area. of the hole in the barrel.
Third, agree on the ammo to be used and peak pressure level to be used for testing velocity.
If any comparison's not made to these standards, the velocity numbers will be bogus.
The reason 4 grooves have been the standard for decades in 30 caliber military barrels is their depth, shape and width require minimal engraving of the bullet and weakening of its jacket as well as long barrel life and good accuracy along with easy, efficient manufacturing tooling. Other types start changing things.
When Sierra's 30 caliber 155-gr. Palma bullet was introduced, several folks tried 5- and 6- groove barrels that shot heavier ones very accurate. Neither shot them as accurate as 4-groove barrels.
Second, what will be the width and shape of the groove that also forms the lands as well as the cross sectional area. of the hole in the barrel.
Third, agree on the ammo to be used and peak pressure level to be used for testing velocity.
If any comparison's not made to these standards, the velocity numbers will be bogus.
The reason 4 grooves have been the standard for decades in 30 caliber military barrels is their depth, shape and width require minimal engraving of the bullet and weakening of its jacket as well as long barrel life and good accuracy along with easy, efficient manufacturing tooling. Other types start changing things.
When Sierra's 30 caliber 155-gr. Palma bullet was introduced, several folks tried 5- and 6- groove barrels that shot heavier ones very accurate. Neither shot them as accurate as 4-groove barrels.
Broz
Well-Known Member
Bart, to clarify, "them" being the light 155 gr 30 cal bullets correct?
This was not the case with the heavy for caliber bullets? correct?
Thanks
Jeff
Yes.
(C&P -- Barrel FAQ -- Barrel Velocities, Lengths, Twist Rate, Contours, Cleaning, Accuracy and Ballistics for Benchrest, Hunting, Precision Shooting)
What Is the Best Number of Grooves? Barrel-makers report that, as long as the ratio of lands to grooves is relatively constant, there is no demonstrable difference in accuracy among 3-,4-,5-,6- and 8-groove barrel designs. Krieger has told us "There isn't any advantage to the shooter. Assuming the ratio of the surface area is kept the same, the number of grooves should not have any effect. Barrel makers use different numbers of grooves for ease of manufacturing and ... marketing hype." That said, in our experience, 8-groove barrels are a little slower, and may foul a bit more quickly because there are more edges to cut into the bullet's jacket and to trap powder residue. We see no reason not to specify a 4-groove barrel if that is your preference. Moreover, IBS Hunter Champion Al Nyhus and others have had great success with Lilja 3-groove barrels. Al believes the 3-groove design cleans up more quickly and yields a bit more velocity. Famed gunsmith and wildcatter P.O. Ackley believed that, all things considered, a properly-made 3-groove barrel is optimal for most common calibers. Ackley believed 3-groove profiles can deliver higher velocities with less fouling and no significant reduction in accuracy. In the months ahead, 6mmBR.com plans to do a comparison test of various barrel formats.
I have a 30" Lilja 3-groove in my .270AI, I've shot <100 rounds but am very happy thus far.
Broz
Well-Known Member
MudRunner2005
Well-Known Member
All my custom barrels, from now on, will be Rock Creek (Mike Rock) barrels with 5R rifling.
I have both type barrels and I like both. For many years the 5R was locked in with Obermeyer he has the rights to that and he's let those rights out to some over the years and their very few making that type barrel. I have Obermeyer,Kreiger,Bartlein and Mike Rock 5r barrels also Broughton 5c and Shilen Ratchet rifled 4 groove. I also have some rifles with Lilja 3groove.
I've always like the 5r barrels been pretty hard to get at times. My last build used Rock 270 5r was a long wait. I put Lilja 3groove barrels on 280AI,284,270,30-338mag. My first 300WSM used a Broughton 5c barrel and lastest one used Krieger 1/11.25r and I was going to do a 7WSM looked at Bartlein 5r barrel for that but opt for the 280AI/284 with the Lilja.
Well good luck
