Has anyone experienced a SIGNIFICANT difference between standard and polygonal rifling regarding accuracy? I read that poly rifling puts more “squeeze” on a bullet, but less “drag” - or marring, from standard rifling. Have you come across any riflemaker who’s gone to poly? Just curious.
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Polygonal rifling provides better gas sealing behind the projectile, which should give more consistent muzzle velocity for each shot.
They say it also comes with better accuracy… but I couldn’t find any prove of that, especially for defensive applications.
My Staccatos came with conventional rifling and they are pretty damn accurate.
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PS: don’t know if anyone other than Marlin that uses microgroove or
poly rifling. I think they did it because it was cheeper to make. If your shooting lead bullets Ballard stile rifling with a slower twist rate should be better.
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When I started to shoot Hornaday 160grn. Flex Tip in my Marlin model 336 30.30. I was a little worried about the Microgroove rifling’s in the barrel but they performed to standard.
I can shoot a sub 1" group at 100yds and a 3"x3 1/4 inch group at 300yds. with the advertised
11 inch drop at 300yds. with a 200yd. zero.
They have literally shrank my groups by 3" and added 100yds to my accuracy. 
When they introduced the Flex Tip the new Marlins were said to use a Ballard Cut rifling’s.
I did notice if you short shuck the Flex Tip it will get stuck. 
P.S. I was able to check with Marlin on the SN on my 336 and found it was made in 1970. I paid $200.00 for it in 1983 from a widow whos husband had passed, It was in “like new” condition.
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Polygonal rifling (/pəˈlɪɡənəl/ pə-LIG-ə-nəl) is a type of gun barrel rifling where the traditional sharp-edged “lands and grooves” are replaced by less pronounced “hills and valleys”, so the barrel bore has a polygonal (usually hexagonal or octagonal) cross-sectional profile.
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Glock pistol barrels have polygonal rifling. When someone uses a Glock in a shooting and the bullet gets recovered it is harder for a microscopist to match to another bullet from the same gun due to its smooth rifling.
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