M&P 9 Barrel: Five Grooves Instead of Six?

[Ben86]

I have recently noticed that both my 9mm m&p models have five grooved barrels instead of the usual six that I see in the rest of my 9mm pistols. I was wondering if anyone here knew why and if there is an advantage to having more or less grooves.

 

[Sam1911]

Smith & Wessons are like that. There have been some interesting threads with folks trying to figure out how to measure their revolver's true bore size after slugging the barrel and finding that there are no two groove impressions which are directly opposite each other! (So calipers won't tell you the bore diameter.)

No real benefits or detriments. Heck, if you inspect a lot of old US 1903A3 rifles, you'll find they had TWO groove rifling. And those are often quite accurate.

 

[Ben86]

Thanks for the info Sam.

I've also read that S&W uses a slower twist rate than most other manufacterers. It seems S&W marches to the beat of their own drummer as far as rifling, but it doesn't seem to matter.

 

[Sam1911]

You wanna see something really out there, their .460 Mag uses gain-twist rifling!

 

[rcmodel]

S&W buys all the broken and worn out 6-groove rifling cutters from Taurus and reshapes them into 5-groove cutters as a cost cutting measure.

I seen it on the internet, and the internet don't lie!

rc

 

[Infidel4life11]

S&W buys all the broken and worn out 6-groove rifling cutters from Taurus and reshapes them into 5-groove cutters as a cost cutting measure.

I seen it on the internet, and the internet don't lie!

rc

BAHAHAHA. Smith even put 5R rifling in an AR. With 5 grooves there is different degrees in which the grooves are cut. IMO 5R rifling is more accurate than the typical 6grooves. I'm not saying the rifling in your M&P is 5R but M&Ps are good shooters.