Polygonal v. Traditional L&G Rifling ("Glock tests")

This is the newest part of our site.  Firearms today typically use one of two different styles of rifling to impart spin to a bullet and thereby stabilize it for flight.  Traditional rifling uses a number of lands & grooves (L&G) which are cut into the barrel, and is the style of rifling most people are familiar with.  But a number of firearms manufacturers use polygonal rifling, most notably Glock, H & K, and Kahr.

For years people have wondered about the effects of the different styles of rifling, and whether one or the other would offer specific advantages for accuracy or velocity from a given cartridge.  But since many different factors can have an effect on both accuracy and velocity, these discussions have largely remained anecdotal.  We decided to see whether we could generate data as to performance differences between the two styles of rifling as concerns bullet velocity, using our standard chop-test techniques.  The data on this page is the result of those tests.

A few notes:

• In order to get both a traditionally L&G rifled barrel and a polygonal barrel from one manufacturer, we had to change our usual supplier.  We obtained both barrels from Lothar Walther.  Both barrels were "six groove" (the traditionally rifled one had six lands & grooves and the polygonal was hexagonal).
• Because we expected the differences in performance between the two styles of barrels to be fairly subtle, we decided to do 10 shots of each ammunition type through each barrel for each inch of barrel length.  At the outset we determined that we would want a minimum of 7 of those 10 shots to be "good" (generate trustworthy chrono readings), or we would add in additional shots to get at least 7 readings.
• For this test sequence we shifted over to a new Oehler Model 35P Chronograph system.  While we have been happy with the previous brands of chronographs which we have used, this instrument provided a significant jump in accuracy and ease of use, and gave very consistent results.
• The chops tests ranged in barrel length from 18" down to 3".  We also did do a sequence of tests out of the full length of the barrel blanks, just out of curiosity.  The results of those tests can be found on our blog.

Initially we intended to test both 9mm and .45ACP cartridges for this sequence.  Because of ongoing problems in obtaining sufficient quantities of high quality ammunition, we decided to just go with the 9mm sequence and see whether the results would warrant also doing the .45ACP.  At this time we have decided to hold off from doing the .45ACP tests.

Below you will find the data set for the different ammunition brands/loadings tested.  Each ammunition brand/loading tested is listed across the top, with barrel lengths down the side.  You will also find a graph to compare the trend for the two types of barrel over the different barrel lengths linked to each ammunition at the top.  A note about our selection of ammunition:  for both the standard pressure 115gr and the +P 115gr rounds we chose one jacketed lead hollow point and one solid copper type of ammo.

If you would like more detailed information showing the actual data collected for each test sequence, download the pdf or Excel files, linked on the "Raw Data" page.

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Barrel Rifling Results in fps

Of the real world guns listed below, only the Glocks have polygonal rifling.  The others are all traditional L&G rifling.