3 groove pacnor barrel

[andym79]

Hi guys I am 90% sure I am going to do a bs 33-47 single shot.

I have worked out for the bullet I want to use a 1:15 twist would probably be optimal. Most makers go 1:10 some 1:12 but Pacnor are the only ones who do 1:14.

I would very much like to know people opinions on if a 3 groove will work okay with lead. By that I mean can more be squeezed from its potential from 4 5 or 6 grooves.

In addition is there any advantage to having deeper grooves? I ask because the B plan for a barrel would be Krieger, I have been in touch with them and they can do a 1:15 twist with 340 or 342 groove diameter.

Sorry if I seem ignorant I have been shooting cast for a while but am new to BS and trying to figute out what makes a truly good cast barrel. All but one of my barrels has a standard for caliber twist.

Thanks Andy

[runfiverun]

the taller lands will dig in deeper and grab the bullet.
4 lands will place those directly across from each other.

will it matter?
probably not at 16-1700 fps.

[Scharfschuetze]

I would very much like to know people opinions on if a 3 groove will work okay with lead.

The US Military used 3 groove barrels with lead bullets until the adoption of the 30/40 Krag with its jacketed bullet.

[andym79]

I did know that thanks. But can more be got from 4, 5 or 6? And are odd or even grooves better with cast? Some have told me that odd grooves are better because having grooves and grooves and lands and lands directly opossing each other distorts bullets more than if a groove opposes a land. Is there truth in that?

[guicksylver]

A LOT of people are shooting tiny groups using lead boolits out of guns that have been rebored from .308 Win to .358 by Jess ...the most popular boring is the 3 groove option

I should also note that odd groove barrels are usually the better ones because when cutting the grooves the cuter is braced on the opposite side by a land..
examples 5R rifling (Remington) ..US M1917

[KVO]

When I was at the AMU number of grooves and "best" twist rate were always a popular subject, but there was never a clear winner in spite of trying them all. An odd # of grooves does not place opposing pressure on the projectile, so theoretically less bullet deformation. A lot of the theory takes second place to precision and manufacturing quality. Boots Obermeyer jokingly mentioned to one of my coworkers that he liked odd groove barrels because his customers had trouble measuring them and he'd get less calls about groove and bore diameters being +/- a thousand or two from "ideal spec." Regardless of rifling profile the proportion of land to groove surface area is fairly close between them all. My experience relates to smallbore rimfire (which can drive you to the edge of your sanity) and jacketed centerfire. Admittedly I am newer to optimizing cast performance, but the principles are a constant esp. compared to rimfires. All that is to say that a quality barrel from any of the good manufacturers will have about an equal chance of performing if the chamber, throat, tennon threads etc. are cut straight and to the appropriate size.

[KVO]

For all of the good shooting barrels I've seen, there is the occasional bummer from everyone, Krieger, Lilja, Hart, Shilen etc. The bad ones would feel "choppy" if you slugged them with tight and loose spots, though they looked perfect with the bore scope. Interestingly, the really bad shooting ones would improve marginally with more lapping (all the premium bbls are already hand lapped), but the bad barrels could rarely be improved enough to be usable for competitive use. One of the things I've speculated (absolutely no proof) is that bad barrels may result from some flaw or irregularity in the barrel material itself, be it a flaw, inclusion, or stress.

[country gent]

Some claim that 3 groove barrels center the bullet better and faster. (A 3 legged stool always sit with out rocking) Odd number of groove barrels may produce less distortion than even number of groove barrels. I have 2 3groove barrels a Pacnor on a savage action 26" long it is chambered for a wildcat 6.5 on a shortened 300 wsm case ( 5 % less capacity than a 6.5 284 case) and the other Is a 3 groove lilja 22 caliber 1-7 twist onn my spare upper for my AR match rifle. This barrel started as a 26" but the chamber was bad when cut and we shortened it and recut the chamber so its now 24". Both are very good shooters with Jacketed. The good upper with Krieger 26" barrel and the spare upper are for all practical purposes equal in accuracy. I agree that the quality and craftsmanship of the maker is more important on a barrel. The top makers are so close that its hard to tell a diffrence

[jerry6stl]

Most serious target shooters and benchrest competitors us 6 groove barrels.