Gunsmithing Polygonal rifling

[Greg Langelius *]

I'm in need of some solid facts and experience from actual users of Polygonal Bore Rifle barrels. I had appended my initial question to another thread, but I think it deserves a thread of its own. The initial response was very helpful, but restricted to issues and factors associated with creating them. I am properly grateful and it was very informative, but I'm still also interested in actual experience and recommendations from users. Also, I'm concerned about rifle barrels only, not pistol barrels.

Informed viewpoints preferred; speculation, less preferred.

Greg

 

[chpprguy]

Re: Polygonal rifling

Here is thread with some folks who used polygonals...
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=969137

HTH
Andy

 

[Greg Langelius *]

Re: Polygonal rifling

Andy;

Thanks abunch, now that's what I'm talkin' about.

Always hungry/greedy for more, anything else?

Greg

 

[918v]

Re: Polygonal rifling

I used Lothar-Walther's poly barrel in my 22-250. I saw 200 FPS less velocity than QL predicted. When I contacted LW to get some info about the bore's square footage (so I could modify QL's parameters) I was told that was proprietary information and I should not be using QL to work-up loads. When I told them I was shooting 90gr bullets outa my 22-250 the argument started to revolve in a circle... use published data... don't use QL... so I got frustrated and sold the barrel.

 

[Falar]

Re: Polygonal rifling

I have a 21" Noveske barrel on my AR10. It does clean easily, probably just as easily as a chrome lined barrel. As far as velocity goes it does not seem to be super fast or anything like that. Velocity seems to be right where it should for its short barrel length, 46gr Varget gets 2750fps with 155gr Scenars, 45gr Varget gets 2630 with 175gr SMK. The hottest load I ran through it is 46.7gr Varget w/155s for 2820fps. Honestly, it seems there isn't much of an increase over regular 20" AR10 barrels. I have a 28" 1:10" Polygonal Pac-Nor on the way for my Savage 10FCP, should be here this month. I'll be able to more directly compare it to the factory 24" barrel since I never even used my factory Armalite barrel.

 

[chpprguy]

Re: Polygonal rifling

Greg,

I pm'd Gunfighter14e2 a week or so ago to see if he was still happy...
He has switched other barrels over and is very pleased...

My LTR barrel will be replaced by one....

Andy

 

[Huckleberry]

Re: Polygonal rifling

I have Pac-Nor polygonals in 223, 25-284, 260, 7mm Weatherby, and 308. Clean easily, high velocities, good accuracy. Heavy and light contours.

Waiting on Bartlein gain twist barrels for 338 project.

 

[Greg Langelius *]

Re: Polygonal rifling

Thanks, you guys. Has anyone managed to get much of a handle on comparative bore/throat life?

Greg

 

[Clark]

Re: Polygonal rifling

http://en.wikipedia.org/wiki/Polygonal_rifling

 

[Pete Lincoln]

Re: Polygonal rifling

Greg, GYR (gyr) has got one from Lothar Walther on a Howa based rifle i put together for him. Its the 1st one ive used for a bolt action barrel, he is monitoring its behavior, so far its shooting well and wacking plenty of Mallorcan goats and some nice groups on paper from what i understand. Might be worth you swapping notes with him,.

regards Pete

 

[gyr]

Re: Polygonal rifling

Yes it is shooting fine.

A good feature is that it shoots well any bullet I have tried so far: either the 155 scenars, 168 SMK, 168 Nosler competition, or 168 AMax.- HAve also tried the 208 Amax and got a nice group, considering all shots were different charges and that my concentration was not excelent as the first 208 Amax busted my CED2 sensors nicely.

.

Most of my shooting is done hunting, usual distances up to 600 m. and shoots better than I can.

As far as cleaning, I can only compare to a LIlja and some factory barrels. The Roedale provided LW cleans easier and seems to foul much less.

 

[Pete Lincoln]

Re: Polygonal rifling

is that a cm square? with the 208gr ?
regards Pete

 

[bignada]

Re: Polygonal rifling

Heckler and Koch did the polygon rifled bores that were not actually "rifled" The bore is like a twisting pentagon and it shapes/holds the bullet without actually being a lands/grooves type barrel that engraves the bullet. The diameter and edges of the polygon fill and hold the bullet, but aside from the boring job done by the cutter, there is no cut or button rifling process.

Then there are polygon rifling methods which shape the lands without the distinct 90 degree angle to the bore of traditional rifling. Polygon rifling imparts more bearing edges over less area which supposedly is a smoother transition into the rifling. Less violent grab on the bullet may mean better accuracy. More bearing area angles mean longer wearing barrels.

The H-K rifling method may be superior for plated bores on battle rifles, but I don't believe anyone ever achieved much success with a twisting polygon barrel in competition. Polygon shaped lands in traditionally rifled barrels are used by many in competitions. The H-K polygonal bore was an interesting engineering advancement, just not an advancement in precision and accuracy.

 

[border_reiver]

Re: Polygonal rifling

Bignada,

Those HK polygons were hammer forged if i remember correctly. They're difficult to measure 'accurately' as it's more of a twisted smear than a groove 'circle' they were creating.