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Posted: 5/9/2006 4:20:15 AM EDT
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Can someone tell me if I should purchase a barrel with a polygonal bore for my .308? I never plan to shot lead ball or any soft jacketed bullets. Just solid copper Barnes XLT. Found this link if anyone is interested. Reference: |
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For what it's worth: The grooves most commonly used in modern rifling have fairly sharp edges. More recently, polygonal rifling has become popular, as it seems to produce better accuracy due to the fact that it does not damage the bullet as badly as conventional rifling. Polygonal barrels also tend to have longer service lives because the reduction of the sharp edges of the land reduces flame erosion. Higher velocities may be generated due to a reduction of friction and an improvement of the gas seal between the bullet and barrel. A disadvantage of polygonal rifling is that if simple lead bullets are used, lead from the bullet tends to accumulate in the barrel (called leading) resulting in a dirty barrel, poor accuracy, and if the leading becomes severe, excessive chamber pressure which could cause a barrel or locking failure. Polygonal rifling is currently seen on most pistols from Heckler & Koch, GLOCK and Kahr Arms. Polygonal Barrels |
If you are dead certain that you will never, ever use any bullets contraindicated for use in a poly barrel, then have at it. There are some possible advantages to the design. However, if you are less than positive about this, then a conventional barrel would offer more options in the future. For example, what happens if your type of bullet becomes unavailable for some reason, and all that is left is bullets that are not suitable for polys? What about re-sale in the future? The future buyer may not share your enthusiasm for your barrel's restricted diet. Will the manufacturer offer a variety of barrel profiles, lengths, and twists? Might want to consider that, as well. One way to increase the life of any barrel is to have it cryoed. Claims of 50% increased life are regularly made, with some evidence that would be supportive. That might render the poly barrel's claims of greater life somewhat moot. A high-quality conventionally rifled and cryoed barrel is likely more accurate than the vast majority of shooters, and a good deal less expensive than its poly counterpart. That being the case, I am of the opinion that the possible, incremental increase in accuracy is not worth the added cost and hassle, not to mention the restrictions placed on bullet types. YMMV. |
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I am not a paying member so I cant find my old posts. But let me explain... Glock and HK have a polygonal bore. This means that the bore is the shape of a polygon and it "turns" the polygon down the length of the barrel to spin the bullet. These bores are made integral with the making of the barrel in a hammer forged barrel. This is the only way they are made. There is no need to rifle the barrel because they are already in the barrel when its made. ONLY HK and Glock offer this barrel to my knowledge. Now lets look at Lothar Walther, Pac Nor etc polygonal. This is a TRADITIONAL land and groove profiled barrel. A blank is produced and button rifled. The difference in a "polygonal rifling" as opposed to a polygonal bore is the polygonal rifling is not the shape of a square and 90 degrees on the angles of the lands and grooves. Instead it is polygonal shaped rifling. You cannot see this with the naked eye. With the naked eye you see traditional land and groove rifling and its jsut got angles on theh edges of the rifling. With a polygonal bore you can easily see there are no lands or grooves but as polygonal shape instead. Now the site you linked to is decribing polygonal bore, made via hammer forging like glock or HK. This is also the bore that should not have lead bullets. What applies to polygonal bore and polygonal rifling is not one in the same. The terms polygonal bore and polygonal rifling are often used in place of one another which leads to confusion. Do not think you are getting the benefits of an HK or Glock style rifling when you are not. You can shoot all the lead bullets you way from a polygonally rifled weapon. It is not the same as the HK/ Glock style polygonal bore. You cannot find polygonal hammer forged barrels for sale. All the references you will get for polygonal custom barrels will be of the land/groove variety. People often try to claim the added velocity and life of the hammer forged type applies to the button rifled type. This has not been proven like it has with the Glock/HK type rifling. Controversy still abounds. Some calim a small benefit others none at all. Be aware of these facts when making a purchase selection of your barrel. |
Hammer forged does not always = polygonal but polygonal always = hammer forged.... unless its polygonal rifling and nt a polygonal bore which is usually button rifled. |
this needs to be tacked. |
That was quite possibly the best post you've made Devl.  There's two sides to the polygonal rifling camp too. Those who are for it, and those who are against it. 75% of the time, both camps will exaggerate to the extreme to push their own philosophy, and many times even more when finances come into play. I suggest talking to the people who own them and are unbiased. They are not super barrels, but they are still very high quality. I'd rather have traditional rifling, but the availability of match carbine barrels still hasn't exactly peaked. I could count the places on one hand where I could get a 14.5" SS barrel, and Noveske is one of the few offering such a barrel. ETA: There was a German company a few years ago that made polygonal bore AR15/M16 barrels. I forget the manufacturer, but IIRC they were in the $700+ range. |
| Thanks for the compliments. I have a PacNor blanked polygonal barrel that is being built up on a rifle right now. I have not been shooting with it so I cannot make any claims or show proof one way or the other as to accuracy, velocity or life. To be honest I thought this barrel was going to be HK/Glock style when I bought it as I did not know the difference in polygonal barrels myself. After calling PacNor and doing a bunch of research I learned what I posted in the above post. I think the polygonal barrel confusion is pretty widespread and people need to know the differences. I question whether or not I would have purchased the PacNor blank if I had known what it REALLY was when I decided to purchase it. |
Well, what about the velocity figures that Wes at MSTN reported from Noveske's 12.5" Crusader 5.56 barrels? IIRC, he was getting 14.5" velocity figures from the 12.5". Just some food for thought. By the way, how's your ABS build coming along? Justin |
You'll get the same numbers from any SS barrel with a match type chamber. I got the same results from Wylde chambered Wilson barrels from WOA. |
Steve, You say they're tight match chambers, Wes says otherwise. I honestly would like to know once and for all which is correct; please help me oit here Steve. Justin |
Sorry, tight is not the right word, as the chamber body is larger, I dont remember how to explain the differences. Its mostly lead and free bore if I remember correctly. Either way, in the scheme of things its doesnt matter  If you really want to know, call John Holliger 309.376.2288 and ask him to explain. He does a much better job than I can. |
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I read a recent interview with Tubbs in one of the gun rags, can't remember right now. He stated that the rifle barrels he shoots are polygonal rifling and that he uses moly-coated bullets. He believes this maximizes velocity from the barrel (less restrictive rifling and the moly as lubricant). He also states that he cleans after 600 rounds have been fired, and that he does not have to clean as much because the polygonal rifling does not trap as much residue as standard land rifling. Just thought I'd throw this into the mix. |
After ABS corrected the mistakes the barrel and bolt are now adequate, sending everything off the Hondo and hoping the SBR paperwork from LW to GP has cleared but I dont think it has yet. |
Hard to disagree with this. Has anyone got any life experiences with polygonal or just hear say. |
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