Glock Rifling Question

April 03, 2017, 11:39 AM

Rogue's post in the Glock thread about the potential changes for the upcoming "M" series Glocks raised a question for me on a subject to which I admit total ignorance.

What is the practical difference between conventional rifling and Glock's polygonal rifling and why would one be more desirable than the other?

April 03, 2017, 11:47 AM

RogueJSK

It's rumored that this was one of the considerations in going with conventional rifling on the 17M/19M: http://www.thefirearmblog.com/...miami-glock-barrels/

I've heard that the new conventional rifling might have been based on Glock "Miami rifling" as discussed in that article. It makes sense that the 17M/19M models, which at this time are limited to only LE agencies, would go with a type of conventional rifling that's more conducive than polygonal rifling to ballistic identification, for help in officer-involved shooting investigations in which more than one officer fires.

Polygonal rifling is also less ideal when shooting unjacketed lead bullets, as it fouls more easily. But I doubt if that factored into Glock's decision.

April 03, 2017, 03:20 PM

RNshooter

I believe polygonal rifling creates a better gas seal, based on the very slightly higher velocities Glock barrels will produce, inch for inch.

I don't know of any other advantages? Production cost/ease?

Bruce

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April 03, 2017, 03:45 PM

RogueJSK

quote:
Originally posted by RNshooter:
I don't know of any other advantages? Production cost/ease?

Polygonal rifling supposedly results in longer barrel life, but I don't know if that's verified fact or just rumor.

April 03, 2017, 06:44 PM

NavyGuy

Polygonal barrels are hammer forged. The equipment to do this is said to be very expensive, and then there is a precise heat treat process needed to relieve the internal stress caused by the cold hammer process. So the manufacturer would need pretty large production quantities to get a payback on the machining equipment and heat treat process. Sounds like Glock and HK to me.

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April 03, 2017, 07:59 PM

Jim Watson

I suspect that the main advantage of the so-called* "polygonal" rifling is that the hammer forge mandrel without sharp corners will last longer in mass production.

*My sophomore geometry teacher defined a Polygon as a closed figure made up of STRAIGHT line segments. Not seen in gun barrels so described.