cvatridge design, H4198, and Qucik Load

Boyd, I have pondered just that question. If you move to 1,000 yard benchrest, where the absence of stock rules make a design to achieve a "center of mass" build easier, there have been several rifles built that approached this. The one that came closest, by his design and work, was Joel Pendergraft's world record holding heavy gun (his record has since been broken).

Now one 10-shot group, even if it is a record, proves very little. But the rifle was used, in two configurations, with two barrels, for over 4 years. In its first incarnation, Joel won more heavy gun matches at Hawks Ridge than any other single competitor. The rifle was rebuilt, with a different tube and barrel, and that one set the world record.

Before Joel, there was Charles Bailey's heavy gun -- actually, again, two different builds, and at least three barrels. What was so often remarked about with this rifle was the tensioned barrel. Less remarked was the mass of the two rifles, admittedly in large part due to the tensioned barrel setup, was centered around the centerline of the bore.

Then there is mine, again, two builds. I chose a design somewhat simpler to execute, so I do not have a perfect distribution of the mass. But it is close. Again, more than one barrel. I've not had the success of Joel and Charles Bailey, but the rifle is a consistent performer -- it's performance seemingly in direct proportion to how good the barrel is.

These rifles do not exhibit vertical, save due to conditions. This from reasonably extensive testing at 100 yards, where you have a fighting chance to get a handle on conditions. Neither Joel nor I had single digit ES for velocity. As I remember, SD did approach the single digit level. Whether or not that is a requirement I don't know. Current theory predicts that optimizing time-in-bore compensates for velocity variations, but only if the barrel has a cyclic vertical movement. Without that movement, you should get vertical dispersion, right? But we don't.

* * *

I've also felt, for the point-blank game, that one reason aggs have come down is that stocks have gotten lighter and scopes heavier. It use to be you had a 32-ounce stock and a 15-ounce scope. Now each is closer to 20 ounces. Maybe it's all just bullets and barrels, but the changed distribution of mass in a typical LV rifle is there.

The reason I brought up the "longitudinal" distribution of mass is that it would be reasonably easy to build a short-range HV rifle with the mass radially centered -- or top/bottom, left-right, if "radially" is the wrong term. Complete centering in all planes would not be possible given the rules, that would have to be an unlimited.

I don't know of any PB unlimiteds designed to center the mass around the bore. I have the pieces. If I ever get it built, I'll have one. My first one was tension-barreled, but a pendulum style, with several design flaws.

Truth to tell, I'm building much less these days, and shooting much less. I don't know if I'll ever get either the HV or unlimited built. And even if I do, they will still be only one data point. Still, they would show whether or not there was vertical with that "untunable" design.
 
Charles,
(Pictures?) I wonder if the tensioned barrel rifles perform more as a result of the added stiffness or mass distribution. If one simply distributes mass, without the tension, would the muzzle tend to hunt, without any induced swing? Have you ever laid a light stocked Sporter, with a relatively heavy scope on its side and picked it up at the muzzle and behind the action, by a rod through both (It helps to take the bolt out.;)), to see whether the top or bottom is heavier?
Boyd
 
Gene,

Thanks for the response. I don't really have a good response as to why I haven't tried the 6beggs other than I just haven't been able to get a 6mm barrel to shoot competitively for a year. I just can't figure out if it's my tune or barrels. I sure don't have that problem with the 22 short. Also, I do have a very good set of 22cal bullet dies. Send me a email or PM. I would like to discuss a couple of things with you.

thanks again
Hovis
 
Ratigan does shoot n133 but he doesn't shoot a .100 short. Mike shoots a .070 short i do believe, or an .080? One of the two. I think i may try my precious lot of new 8208. What few shots i have put through this new barrel i have looked good. You just cant let the barrel sit to long without sending a shot down it. My experience anyway with the 6ppc. Maybe the 22 will be different? Lee
 
(Pictures?)

Sorry, not great, but all I have. Charles E, I assume this is one of the rifles you had in mind?

Charles Bailey with his rifle, plus the only way to move a 150lb gun short of hired help.

cbailey.jpg


charlesbguncart.jpg
 
All pictures from old computer 378.jpgThe late great Skip Otto may have had some similar ideas about balance. These are not tensioned, and are filled with oil, with an O ring at the muzzle to act as a seal. I believe that Tom Libby shot a record with one, and that had to be the gun;). If you eyeball the weight of the top that is above and below the CL of the bore, it looks close.
Allpicturesfromoldcomputer377-2.jpg

Allpicturesfromoldcomputer378-1.jpg
 
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Boyd, here is a link to a few pictures of Joel's rifle (second incarnation)

http://bulletin.accurateshooter.com...ets-new-ibs-1000-yard-heavy-gun-world-record/

This one weighed about 80 pounds, made from aluminum. Charles Bailey's "Blue Gun" that Fergus showed was made of steel. His later "silver gun" was aluminum, and it too went about 80 pounds.

There was a picture of mine, but I can't find it. It is more of a bull-pup design, so went about 75 pounds even with a 3.5-inch o.d., .75-inch wall pipe (Thanks, Jackie!). It maybe has 5 pounds more on the bottom than the top, but I don't get vertical with it either. Maybe that is evidence for your point, that it is just total mass, and with the tensioning tube, the barrel is acting like a double-cantilevered beam.

These tensioned-barrel rifles are sort of like tuners in one regard: average barrels become good ones, good barrels become very good, and so on. Of the three barrels I've used, none was "very good," so my groups were about an inch, inch-and-a-half bigger that CB or JP at 1K. Kiss of death. But as I said, no vertical, and I could win the score portion with them. And did.

* * *

I've though about your question, whether or not we could scale them down to 10.5 pounds an have the same results. The rules make that pointless.

It wouldn't be pointless to build a 17-pound rifle for 1K light gun though; maybe that would give some answers.

I take Harold Vaughn's results with the recoil isolator as some evidence. Surely somebody must have tried that with a LV. If so, I guess it wasn't a success or we'd have heard about it. Neither of Vaughn's designs, the sporter or the rail, paid any attention to the longitudinal center of the mass, and his rail could be tuned for vertical, so no firm conclusions available from that source.

Time for some young'un to make some chips.
 
Charles,
I think that what Harold was trying to point out was what sort of barrel vibration was generated by using a Remington style lug, that as the force of the barreled action recoiling was transferred to the stock, that the lug was also acting on the bottom of the barrel shoulder, flipping the barrel. By delaying contact between the lug and the stock until the bullet was out of the barrel, the effect of the vibration caused by that particular transfer of energy was avoided. The common practice of gluing actions into stocks eliminates all of this, and a good pillar bedding job allows high enough torque to more effectively immobilize the action in the stock, given the calibers that are the usual in short range Benchrest. I seem to remember that Harold was using a conventionally bedded Remington .270 as a starting point, measuring muzzle vibration before and after the addition of the recoil isolator. More to the point ( I think.) was his rail gun experiment, where he added mass above the bore, to balance the top around it.
Boyd
 
Boyd, I spoke to Harold about this. He was remarkably available -- just call him up. I asked him if the same effect as he got with the recoil isolator couldn't be achieved by changing the position of the recoil lug, specifically to each side of the action on the bore centerline. His response was no, because the majority of the weight in a conventional rifle was below the centerline of the bore, that was the problem -- i.e., it was the total mass itself, not the location of what transferred the forces of firing to the stock (recoil lug). With the recoil isolator, the only masses involved while the bullet was in the bore were the barrel, receiver, scope, trigger, etc.

I could have misinterpreted what he said, but that *was* the basis for our conclusion that if all the mass was (approximately) on the bore center, vertical barrel vibrations would be greatly reduced.
 
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These rifles do not exhibit vertical, save due to conditions. This from reasonably extensive testing at 100 yards, where you have a fighting chance to get a handle on conditions. Neither Joel nor I had single digit ES for velocity. As I remember, SD did approach the single digit level. Whether or not that is a requirement I don't know. Current theory predicts that optimizing time-in-bore compensates for velocity variations, but only if the barrel has a cyclic vertical movement. Without that movement, you should get vertical dispersion, right? But we don't.

One needs to look carefully to find the difference between a tuned and untuned barrel at 100 yards. The vertical produced in a stationary barrel by an ES of 50 fps is only about 0.050" at 100 yards, or about 0.025" for an ES of 25 fps. So if a top/bottom balanced rifle stops vertical muzzle motion, then it can shoot some nice groups with low ES loads. But that doesn't mean it is a good design.

Happy Holidays,
Keith
 
Good Design



Keith

The best we can hope for is a consistent burning rate at a given temperature, and a consistent change of burning rate with change in temperature.


When I look at the big picture I don’t see much room for improvement of the Benchrest Rifle as used today and feel the weakest link is the still powder temperature sensitivity.

Any thoughts on how we can achieve the consistent burning you mention?

Ken
 
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Keith




When I look at the big picture I don’t see much room for improvement of the Benchrest Rifle as used today and feel the weakest link is the still powder temperature sensitivity.

Any thoughts on how we can achieve the consistent burning you mention?

Ken

Ken,
I don't know much about designing powders, but the physics suggest that temperature sensitivity is inherent because of the heat transfer to the barrel. One idea would be to control the temperature of the barrel, like with a water circulation system. That way the heat transfer may still be significant, but would be the same every time. Another route would be to minimize heat transfer by using insulating (lower conductivity than stainless), reflective (lower absorptivity) materials and surfaces in the bore.

I have measured barrel temperature during matches for a couple of years now. On my gun, barrel temperature follows ambient and never rises more than 6 degrees F above ambient on the outside of the barrel. Of course, it's the inside (bore) temperature that controls heat transfer, but if we could keep barrel temperature from following ambient during the course of a day, a large part of the tuning problem might disappear.

Happy New Year,
Keith
 
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