Polygonal Rifling
I did a lot of research when a gun I was looking at had polygonal rifling (like Glock).
In short, polygonal rifling is a hammered barrel to make the tube out of round in a polygonal shape, some are hexgonal, some are octagonal depending on caliber.
Polygonal rifling tends, with lead only rounds, to slick the lead on the inner surface of the barrel. Land and groove rifling has places for the lead to compress to (within the grooves) and does not have this problem. Polygonal, leaves the lead no where to go and thin layers slough onto the inner barrel. This has the effect of gradually increasing pressure and thus decreasing consistency.
I bought the Mini Firestorm 40 and found that Firestorm(now called Bersa) had already solved this issue to some extent. Not only was the barrel polygonal, they had also machined in lands and grooves (albeit much less depth than typical). This reduces the slicking issue with lead only reloads.
What I do not know is if Glock has followed suit with their polygonal barrels. There are plenty of aftermarket Glock barrels with traditional rifling that will not cause consistency issue with reloads.
Benefits of polygonal rifling? The barrels wear down at a far less rate than land and groove. And they are much cheaper to produce (which is why Glock went with them early on)
I do notice after my shoot with reloads in this Firestorm, that there is quite a bit of lead to remove from inside the barrel. I bought a brass brush, specifically to do that. It even slicks up quite a bit of the copper.
Now, the reloads I used, weren't mine, but they were a reputable LGS locally. Their reloads worked as well as anything in my .45, but it took around 50 rounds to make this 40 start being inconsistent. Groups went to 4" at 7 yards instead of my normal 2". Could be me, could be the day. Not sure, it was only one shoot. But, the FMJ I shot afterwards, went consistent after 3-4 rounds. I assumed they blew the excess out of the barrel.
Glock says not to run reloads in their guns.... I do it all the time. How will they know?
I did a lot of research when a gun I was looking at had polygonal rifling (like Glock).
In short, polygonal rifling is a hammered barrel to make the tube out of round in a polygonal shape, some are hexgonal, some are octagonal depending on caliber.
Polygonal rifling tends, with lead only rounds, to slick the lead on the inner surface of the barrel. Land and groove rifling has places for the lead to compress to (within the grooves) and does not have this problem. Polygonal, leaves the lead no where to go and thin layers slough onto the inner barrel. This has the effect of gradually increasing pressure and thus decreasing consistency.
I bought the Mini Firestorm 40 and found that Firestorm(now called Bersa) had already solved this issue to some extent. Not only was the barrel polygonal, they had also machined in lands and grooves (albeit much less depth than typical). This reduces the slicking issue with lead only reloads.
What I do not know is if Glock has followed suit with their polygonal barrels. There are plenty of aftermarket Glock barrels with traditional rifling that will not cause consistency issue with reloads.
Benefits of polygonal rifling? The barrels wear down at a far less rate than land and groove. And they are much cheaper to produce (which is why Glock went with them early on)
I do notice after my shoot with reloads in this Firestorm, that there is quite a bit of lead to remove from inside the barrel. I bought a brass brush, specifically to do that. It even slicks up quite a bit of the copper.
Now, the reloads I used, weren't mine, but they were a reputable LGS locally. Their reloads worked as well as anything in my .45, but it took around 50 rounds to make this 40 start being inconsistent. Groups went to 4" at 7 yards instead of my normal 2". Could be me, could be the day. Not sure, it was only one shoot. But, the FMJ I shot afterwards, went consistent after 3-4 rounds. I assumed they blew the excess out of the barrel.