Polygonal rifling -- Pros & Cons

[deadeyedick20]

I've been trying to find more information on Polygonal rifling, and so far I have only been able to find out what it is. The information I've found states that it helps the bullet to shoot straighter and that threre is less resistance in the barrel. There has also been warnings about shooting lead ammo in a barrel with this type of rifling. In looking at different guns, I have noticed that there are more of them coming out with this type of rifling. I would like to know both the benifits and drawbacks of this type of rifling.-------- I think I just found a bit of information as to why it is not a good idea to shoot lead in a poly barrel. The claim is that lead builds up more quickly in this type of rifling, and the buildup will increase chamber pressure to a unsafe level.

[IDPA Shooter]

I've been trying to find more information on Polygonal rifling, and so far I have only been able to find out what it is. The information I've found states that it helps the bullet to shoot straighter and that threre is less resistance in the barrel. There has also been warnings about shooting lead ammo in a barrel with this type of rifling. In looking at different guns, I have noticed that there are more of them coming out with this type of rifling. I would like to know both the benifits and drawbacks of this type of rifling.-------- I think I just found a bit of information as to why it is not a good idea to shoot lead in a poly barrel. The claim is that lead builds up more quickly in this type of rifling, and the buildup will increase chamber pressure to a unsafe level.

Glocks certainly likes it and so does H&K. I know all Glocks are polygonal and am unsure of the H&K, if all have it or just some. You say there are more coming out,I'm not aware that other major makers who use it. There could be many, I just know about them.

As to lead bullets, they both say don't do it for the reason you note. To save someone else writing , yes, people do it, but lots of rounds would cause an issue and it complicates cleaning. Better to get a Lone Wolf or other after market barrel. But then again, we had a student who insisted on firing 556 rounds thru his DPMS 223 stamped barrel was OK cause the guy at Sheel's who sold him the ammo said it was. He chose to ignore the DPMS certified armorer who was present who told him don't do it, so YMMV, but I don't shoot lead bullets in Glock barrels.

[JFettig]

But then again, we had a student who insisted on firing 556 rounds thru his DPMS 223 stamped barrel was OK cause the guy at Sheel's who sold him the ammo said it was. He chose to ignore the DPMS certified armorer who was present who told him don't do it, so YMMV, but I don't shoot lead bullets in Glock barrels.

mmmm 70,000psi random spikes. those are fun!

[RobD]

Velocities are usually better on polygonal rifling, presumably because of the smaller gaps in the lans and grooves.

This is also the concern with leading... The larger surface area gripping the bullets causes the lead to be stripped off and foul up at a faster rate. Glock states that you should not use lead bullets in their barrels. (They also tell you not to use reloads, so take it with a grain of salt.) H&Ks with polygonal makes no distinction about lead bullets.

That being said, there are PLENTY of people that shoot lead in Glocks with no issues. I have, and I didn't notice any issues... I also run a boresnake through my Glocks after each range session, and do a thorough cleaning once every month or two. If you keep an eye on your barrel and clean properly, you can shoot lead all you want.

I don't cast my own... I have small kids, and its just not worth the risk, and I have found buying jacketed are just as cheap if you buy them in quantity. Precision Delta comes to mind.

[Bessy]

el. But then again, we had a student who insisted on firing 556 rounds thru his DPMS 223 stamped barrel was OK cause the guy at Sheel's who sold him the ammo said it was.

I've heard conflicting reports from dpms on this, so I decided to figure it out for myself. I have 24 inch super bull barrel marked .223 from dpms. I also have a stoney point tool col tool. When I measure the COL using this sucker... it is LONG. If that's a standard .223 chamber than I'm the queen of France. Am I missing something here? I thought the the 5.56 chamber was just a little bit more generous and had a longer throat than .223 and of coarse that allows for higher pressure. This definitely seems to be the case with my barrel even though it's marked .223. (not saying all dpms barrels marked .223 are this way, but mine seems to be).

[Seismic Sam]

Got no idea on this one. My DE50 and my EAA Match 38 Super both have polygonal barrels, but the **** I shoot is all over 1400 FPS, so lead bullets are not an option anyway, and in a DE50 lead bullet vapor will clog up the gas tube and turn the gun into a single shot that you have to send back to the factory to have cleaned out, and it's very expensive to do.

The best advice on barrel leading is probably the Lyman reloading manual, where they go into some detail on different bullet lead mixtures and their relative leading problems. In general, the harder the lead (meaning more tin and antimony), the less problem you have with leading.

[EJSG19]

I'll defer to more knowledgeable people on the majority. But like SS mentioned, the hardness of the lead can have an affect on leading, maybe more than the type of rifling even. The Missouri Bullets website explains it pretty well, and I'm a believer anyway.

Hard lead = higher velocity for optimal leading (or not-leading)
softer lead = lower velocities for the least leading.

Mix those two up (hard lead - low velocity or vice versa) and you will get excessive leading. Too hard lead, and not enough velocity means pressure won't expand the bullet into the rifling completely, and you'll get blowby in the barrel supposedly. Too soft lead going to quick, and the heat melts the base of the bullet excessively leading to more leading supposedly. I'm no lab technician, but that is plausible to me. (This paragraph is worth doing your own reading on, I could be wrong, that isn't uncommon.)

Poly vs. Conventional rifling is one of those great debates with no real clear answer. Do enough research and you just find more and more information that contradicts the other side. I have a glock, I shoot lead because its cheap to reload. I figured why mess with uncertainty and bought an aftermarket barrel with land and groove rifling. Better safe than sorry, and the money was worth that. But, lots of guys are getting away with lead in Poly barrels too, so who knows. I read about it for weeks, until finally deciding enough is enough and did what I thought was best.

[JustinPo]

In general I find that Hex or polgonal rifling is very accurate, my HK USP 45 can hit anything I can aim at. The downside is the barrel seems to be a huge pain to get clean, I have had to switch from CLP 3 in one for my whole gun to using a dedicated cleaning agent for the barrel or I can be at it for hours!

Oh and according to HK never ever use lead bullets in their barrels.

[deadeyedick20]

I mentioned in the Bersa thread that my Thunder 9 Ultra Compact has weird rifling, in that instead of square shoulders on the lands and grooves they look more like humps in the barrel. I don't seem to get a huge lead buildup unless I rapid fire two mags back to back (26 rounds) then it seems that a warm barrel strips off more lead. Bersa does not call the afore mentioned rifling polygonal,and now they are using poly rifling in their new Pro Series hand guns. I use lead for target shooting because it is not uncommon for me to shoot 2 to 300 rounds at a time, and reloading my own ammo with lead helps keep the cost down. I ran into a situation a couple of years ago with my Walther P22, when I fired a butt load of Remington thuderbolt unplated ammo through it. I noticed that the accuracy dropped off dramatically, and when I checked the barrel I couldn't even see the rifling. I stopped using it, and when I cleaned it there was so much lead in the barrel that I had to run a 3/16 drill bit through it by hand just to be able to get the cleaning rod into in. Thank God for lead removing solvent, even at that it took me about a hour to clean it all out. Nothing but plated ammo after that. The P22 uses standard rifling, so I'm thinking it has as much to do with the ammo as it does with the rifling.

[Seismic Sam]

The temperature of the barrel definitely is a factor. The metling point is 636 degrees F. and you can certainly get a barrel up to 200F and possibly 300F if you really go at it, so that would have a large effect on the lead sloghing off on the barrel.

[SIGP240]

One secret is in the bullet lube choice. Look for lubes containing carnauba, or buy a standard stick of lube and melt 6 - 10 crayons into it and add a tablespoon of ultrafine graphite; pour the semi slushy slurry in your preheated sizer. Carnauba melts at a temp much higher than beeswax and parafin. The bullet will also benefit from being dusted with Boron Nitride (commonly called white graphite) this make a killer combo to fight leading. The articles I have read will let you push the bullet way over 1400 fps. The idea is that the carnauba wax plates the bore and it is then too slick to lead up. I shoot these in the Glock 24C factory barrel, no leading whatsover. As always, any accuracy lead bullet shooter slugs the bore, mikes it goes .001 over. Too much compression cranks up the CUPs too little will launch a 'wobbler' if your muzzle is not crowned! Anther secret is follow thru, in the P-240 and M-52, the velocity is so low that if you don't hold your gun solid after detonation, the recoil flip will have pronounced effect on your 10-x ring.