Which can promote some airgun related discussion. The world is going to Hell in a hand basket. We drop in here for a small diversion.

I'm gonna be having injections tomorrow. I might not be so frisky tomorrow afternoon/evening. I'd enjoy some discussion.

Hey ... don't make me have to ask if .177" or .22" is better.

How about a rousing round of "How old are we?"

Common .. give it a thought. There must be something that can stir the hearts of the most calloused keyboard shooter ...

Gary

How about groove depth and /or width for airguns vice PBs? Or, why don't all airguns use a poly style or "smooth twist barrel?

how about repeater/clip vs single shot?

OK ... those are topics. Let's see what comes up. Now - if I start .... that's not intended to be the end too.

To my experience, since we are dealing with limited power ... I like many knife edged lands, rather then wide flat lands. Even though there are more lands, in my barrels (I use from 10-36 grooves) ... combined, they displace less area, and are each easier to engrave.

I think the deepest grooves I've seen, are with Black Powder guns. Mostly, they are using a patch to engage the rifling. At least traditionally.

It really takes very little groove depth to control slugs. I always make them deeper than they need to be.

Everybody loves a repeater. From my position ... it adds weight, complexity, cost, and I think it compromises accuracy.


Gary

Have you ever thought about a grooveless barrel? I'm thinking of something like the polygonal barrels but without actual edges, something that just slightly deforms the slug so it holds the barrel as it twists...

Hi Jerry,

Yeah ... I've actually read something about that. Fella sent me a clipping. This one, just had the last few inches of the barrel
"swagged" into a gentle Octagon or something like that. Would take a die set and then hydrauliuc pressure. The trick would be to control it. I could bend and mutilate a bunch of steel tubing, if you like ... .... hahahhah

What do you know about it? Is it being done, successfully? Seems that would be one for industry, and their "hammer forged" barrels.

Gary

Hey Jerry,

Ever looked down the tube on a Glock pistol? All of them have "polygonal" rifling with no distinct lands and grooves, just a rotating polygon to give the bullet it's spin. The Glock rifling isn't even an actual polygon, since the individual "facets" are curved instead of straight sided. I think that their barrels are hammer-forged, but I don't know for sure. This type of rifling has some benefits in a regular centerfire pistol, namely that it's easier to clean than conventional lands and grooves. They're generally fairly accurate as well, but are hardly considered tackdrivers. The downside of polygonal rifling is that it only really works will with jacketed bullets. Glocks are notorious for how quickly and how badly they lead up when you try to use cast bullets. With the cheapest of cheap reloads with soft cast bullets, you notice the accuracy start to suffer before you're done with even a single magazine full. It's a PITA to remove, though oftentimes a couple of jacketed bullets down the tube will remove quite a bit of the leading prior to getting the brushes and patches out. Some brands of cast bullets can be made to work with polygonal rifling, but typically they're either coated with some sort of polymer, or they're super-hard, or both. Since airguns don't really work with either jacketing or super-hard lead projectiles, I suspect that polygonal rifling is never going to be the best option.

Gary,
Your barrels remind me of an old Marlin .22 that I've got, lots of little, shallow grooves. I suspect that they use button rifling too, given how many individual grooves you'd have to cut. I think that the Marlin trade name is "microgroove", I remember seeing it stampled on the barrel.

Well ... there ya go! In the time it took to read just one more comment .... Glock had already taken my cue ... tooled up .. used hammer forging to boot! And produced an entire line of pictols with polygonal barrels.

Guess it pays to read the whole thread first. But then, it's easy to miss commenting on a given person's contributation.

And, Marlin started "Microgrooving" their barrels. I need to get out more .... ..... hahahaha

Yeah ... I had heard of microgrooved barrels before. Didn't know who or where they were made. Works great. The Butler 56 has a microgrooved 36 groove barrel. Very different look inside.

Best,
Gary

LW makes their airgun barrels in regular or polygonal. I've never seen one so I don't know if it has flat sides or curved. I believe the LW poly barrels are pulled like their regular barrels. As far as I know, only BSA is hammer forging airgun barrels.

I don't think the glock experience translates to airguns as far as leading goes. I know that Pablouk has a poly barreled .25 and I've never heard him complain that his barrel needs cleaning.

I've heard of the smooth twist barrels with just some of the barrel "rifled" but I was wondering if a button that was just very slightly shaped (think of a circle with 4 nearly imperceptible high spots) could be used to make an effective barrel. I suspect that even a small deformation of the slug (but over a wider patch) would take about as much or maybe more energy and the friction would be higher than regular rifleing. With normal lands and grooves, the slug can be sized to just barely touch the bottoms of the grooves, this prevents air from getting by but also cuts friction to a minimum. That's probably tougher to do with the idea I tossed out...

HI Jerry,

If you end up with essentially four very wide grooves, with four very slight bumps ... then I guess you really have four lands and essentially a rifled barrel. I see the design. You are right, anything that's counting on total contact with the slug, is going to produce a lot of drag. Now ... a standard pellet with a thin head rim and a thin and fragile skirt edge, can easily form to such an animal.

Regarding the "blow by" issue of regular designs. I suspect the very quick passage of the bullet thru the bore, highly minimizes the vol. of air blast that has time to squeeze thru the micro spaces at the bottom of the grooves? I've always thought it might take the path of least resistance, and it's easier to push the slug out of the way, than squeeze past it. Some would have to. I just wonder how much of a factor it could be.



Gary

Hi guys, there are a number of hand gun manufacturers that use polygon barrels. I'm not sure what the advantages V disadvantages are but I haven't seen one on a rifle yet. The micro rifleing has been around for some decades now and has proven quite popular with the target shooters esp target pistol which tend to be loaded on the light side. I have experimented with a rifleing button which used 4 x 1/4'' ball bearings in a boss which could be adjusted out via a taper that ran up the inside of the boss and pressed on the inside faces of the balls, a bit like a plumbers swageing tool. I had to use a type of sign board to empart the twist on the button whilst it was being pulled through the blank but it worked quite well and gave a kind of polygon effect. This type of barrel worked better with a hollow base slugs. Iv'e found that with the spitzers which tend to prefer a standard type of rifleing of .004'' deep lands are much more less fussy when it comes to slug design, ie lots of different styles and weights can be used and still group well. I generaly use slugs sized .001'' larger than the barrel and have found that a hallow base slug of the same weight will give a slightly higher muzzel velocity than its solid based cousin which leads me to believe that even an oversized slug will alow a blowby whereas the hallow base seals better. So a hallow base spitzer mould will be my next project.Regards to all, Danny.

Danny,

The ball button is a clever idea. I like it. I can see why it would like the hollow base slugs, as (if you used the 4 balls) then you ended up with 4 very wide lands and 4 inverse lobes.

IIRC, some old BSA barrels were made where there were only slight lines cut, leaving the remaining bulk of the circle as smooth wall tubing. In other words ... enormously wide lands, and very narrow grooves. Therefore; the skirt of the pellets had to "blow into" the very narrow grooves, rather than the very wide lands cutting into the slug/pellet.

Gary

From what I understand, with the right combination of slow twist and soft lead, it hardly takes any rifling at all to impart at least some twist. I remember reading (quite a while back) on another website an article about "rifling" smoothbore shotgun barrels with just a close-fitting wood dowel wrapped with steel wool. In this case, some guys were trying to skirt around a law forbidding "rifled shotguns" in a shotgun-only deer hunting area. They were trying for better accuracy with the old "pumpkin slugs" via a number of methods, and this was one that they tried. Since there were no real lands or grooves, the shotgun barrels obviously weren't rifled in the traditional sense, yet their spiralling surface finish did rotate the slugs and vastly improve their accuracy compared to the old mirror-polish smooth-bores.

Of course, Gary's rifling rig is undoubtedly a bit more complex than their method of using a pair of vice-grips clamped to a dowel, measuring their desired twist rate with a yardstick while rotating and pulling their steel-wool "rifling button" by hand.

No ... that's just how I do it too ... Hummmm ... vise grips .... never thought of that .... better than pliers .....

OK ... who's next? We need another topic.

It's two weeks later, and I get another series of injections again tomorrow. Glad for the relief. Hate to have the down time. Especially when the weather is getting better here.

Common ... I know you have a wonderful airgun topic all researched and ready!

Gary

How about sights? Anyone had a chance to use one of the big-bore types with a low power pistol scope mounted in the "scout" position? How about a holosight, or an Aimpoint type red-dot? Enquiring minds want to know...

Hi Rotor,

This one is made for Jerry. He's got a dot sight worth more than my truck, on his Yukon. Works well.

I've done well with my guns, out to 200 yards, with a 4X fixed turkey scope. On Julio's Yukon II.

For the record: I survived my Epidural Injections today. Though, they used dull needles today ... and it hurt a bunch. After they peeled me off the ceiling, the rest was a pc. o cake though.



Gary

Gary,

I've had this idea for a while that might be worth discussing. I've been wondering if it is feasable to have a doublerifle airgun. I can't think of a technical reason why it won't work. Have you ever seen such a beast?

Keith

Hello Keith,

Yes - it could be done. Cost and weight are most of the reasons you don't see them.

It's been my experience, that most people who bring an idea over from firearms, prefer the whole concept to identically mimic the firearm in question. Therefore; they might want to see a nice little - fast pointing - six pound double rifle just like the last safari rifle they saw. In a PCP, there's about another sixty parts including pressure vessels, valves, and heavy springs and hammers.

If you made a true double rifle ... then you'd have nearly all the parts of two complete PCP big bores. You'd be waaay ahead to complete both rifles. If you made a double barrel, where the barrels could be "switched" via a valve ... to fire ... it would be better. Would still be more complex and cost far more.

I have some ideas though. Don't rule it out.

Gary