Your pointy bullets and their flight

[dedogs]

Just read all 9 pages...WOW...what an eye opener!!! Thanks very much to ALL who have participated in this discussion! dedogs

 

[jerrysharrett]

I read all the way back to the F104 that Kelly Johnson put on the table. The Tennessee ANG had them in the 1960's and then they were activated and sent to Germany where the F104's were converted into drones, yes drones in the 1960's.

If we could find another Kelly Johnson???

Back to reality. We need a shape, with or without its ability to maintain constant BC, that we can generate with greater repeatability than what we are using now, IMO.

???

 

[338 Mollett]

Point to ponder!Isn't bullet stability and repeatability related?Throwing in some variables like manufacturing consistency,and the environment,I would think they are closely related.I also wonder in bullet design with all the different forces acting on a bullet,if there isn't a sweet spot like an accuracy node.And to think about how wide or narrow you can make that sweet spot in designing that bullet for a specific purpose.

 

[spclark]

Wonder what the ratio of mirage effect at point blank vs 1k is?

Whooo... a LOT!

I don't use optics much at all for my shooting, with aperture sights at 1,000 yards the challenge is enough just getting centered up! I can say that there have been days when the mirage is so bad I just do a "let's hope" before touching a round off that looks like it should be an X or 10 when the sights settle... referred to as "calling your shots" when the only better feed-back is when the target comes back up, with the spotter in the X-ring!

 

[jerrysharrett]

One recent development of note is a chamber design where the freebore is long, tapered and very slightly under groove diameter. This thinking if it proves out may be one of the innovations this thread was started to accomplish.

Opening the gate on this design, Lou Murdicas, he started out with a 0.039" group in competition. This amazing group was a 5-shot group from a rail gun. Lou may be on to something since our basic benchrest freebore design, except varying its length, has pretty much stayed the same.

Maybe nothing is new? Greg Wally just told me the long tapered freebore is already being used on one of the 300 magnum SAMMI drawings.

 

[Blaster-37]

One recent development of note is a chamber design where the freebore is long, tapered and very slightly under groove diameter. This thinking if it proves out may be one of the innovations this thread was started to accomplish.

Opening the gate on this design, Lou Murdicas, he started out with a 0.039" group in competition. This amazing group was a 5-shot group from a rail gun. Lou may be on to something since our basic benchrest freebore design, except varying its length, has pretty much stayed the same.

Maybe nothing is new? Greg Wally just told me the long tapered freebore is already being used on one of the 300 magnum SAMMI drawings.

Lou is very familiar with the "Bore Rider" concept and a great guy. It works with solids. I competed with the 50 BMG. I studied this concept until I understood it. There is a 770 grain solid "Bore Rider" bullet at Lehigh Bullets that I helped with and competed successfully with at 1000 yards.
Why the 50? I got into the 50 for a tool to break hazard rocks above highways with government provided Raufoss MK211 Penetrating Explosive Bullets instead of repelling into a dangerous environment with explosives. I enjoyed the 1000 yard 50 BMG competitions as before with smaller guns. My previously broke and fused neck protested me back to small caliber 1000 yard shooting after a few years. Other than more than their fair share of testosterone, those great guys, including several high ranking government brainiacs, use and continue to improve some very interesting proven ballistic theories like the "Bore Rider" chamber. The "Bore Rider" Chamber seemed to be the best way to get a small group at 1000 with the 50.
greg

 

[spclark]

One recent development of note is a chamber design where the freebore is long, tapered and very slightly under groove diameter.

OK, I have to ask: how the heck do you achieve a freebore diameter less than the diameter of a bore measured at the depth of the grooves?

Taking a rifled blank as a starting point you can cut a freebore to the same or just a wee bit larger diameter if you're both good and careful... but wouldn'tless than require adding metal back to where it's been removed in the groove-cutting operations?

 

[Blaster-37]

One recent development of note is a chamber design where the freebore is long, tapered and very slightly under groove diameter.

OK, I have to ask: how the heck do you achieve a freebore diameter less than the diameter of a bore measured at the depth of the grooves?

Taking a rifled blank as a starting point you can cut a freebore to the same or just a wee bit larger diameter if you're both good and careful... but wouldn'tless than require adding metal back to where it's been removed in the groove-cutting operations?

Basic description:
From: Lou Boyd <boyd@apt0.sao.arizona.edu>

#Whats a "borerider" bullet?

In most modern small arms the bullet diameter is close to the groove diameter
of the barrel. When the bullet is fired, the barrel lands engrave the sides
of the bullet. In a borerider bullet most of the bullet lenght is close to
the same diameter as the bore (not the grooves) so the bullet slides down
the barrel with only a small area at the back of the bullet being engraved
to provide the gas seal. The reason this is popular with 50 cal bencrest
shooters is that (in theory) the less the bullet is distorted and the more
accurately it is centered in the barrel the more accurate it will be. The
50 cal benchrest shooters have been having good success.

Borerider bullets can be shot from conventional chambers, but for best
results the chambers are specially made with very short throats so that
the driving band (the portion to be engraved) is very near the lands
and bullet is well seated into the bore before firing. This requires
very tight control over the match between the bore and the bullet
diameter to allow the cartridge to be loaded without pushing the bullet
into the case or having it too loose. Another problem with boreriders
is that because of the small engraving area, the bullet material must
be strong enough to spin the bullet without stripping the driving
band. Usually bore rider bullets are solids, made of hard copper,
bronze, leaded brass, or soft steel. Good results are being obtained
with steel coated with moly disulfide. Barrel life isn't spectacular
but that's not the objective. Accuracy is. The concept of boreriders
isn't new. To some extent the minneball (sp?)could be considered a
borerider and many artillary projectiles have used this concept.

Some of us messed with the solids in a 6mm and were not satisfied with the results with our typical chambers.
greg

 

[jerrysharrett]

Greg thanks for the clarification. Looks like I had my description of under vs over backwards? I have not looked at the SAMMI drawing on the 300 mag Greg Walley told me about.

There is a reamer print on benchrest central but it is so tiny I can't read it. Even when I pulled it up on my iPad and zoomed it I still couldn't read the numbers.

Thanks again for the explanation on bore rider technology.

 

[spclark]

Thanks Greg, that makes sense now.

I agree on the "less is more" philosophy, as applied to bullet distortion contributing to improved ballistic stability... among other things.

Isn't this why some bullets feature a 'pressure ring' near their bases? The bearing surface is very close to bore diameter & deforms little if any once into the lands. Gas seal is achieved at the pressure ring only.

Curious then why solid metal projectiles with their drive bands aren't more widely used, unless it's because for the weight their length is longer than lead+jacket bullets? The added length can't be / isn't as well balanced across the rotational speed range they must undergo when shot at long ranges?

 

[Blaster-37]

Thanks Greg, that makes sense now.

I agree on the "less is more" philosophy, as applied to bullet distortion contributing to improved ballistic stability... among other things.

Isn't this why some bullets feature a 'pressure ring' near their bases? The bearing surface is very close to bore diameter & deforms little if any once into the lands. Gas seal is achieved at the pressure ring only.

Curious then why solid metal projectiles with their drive bands aren't more widely used, unless it's because for the weight their length is longer than lead+jacket bullets? The added length can't be / isn't as well balanced across the rotational speed range they must undergo when shot at long ranges?

Your assumptions are in line with many of my conclusions. I am not an "expert" on this compared to some others. The Lehigh 770 grain I worked with had 5 driving/ pressure bands. We did a lot of high speed videos on this. My conclusion was although they are near perfectly concentric but they are not as well balanced longitudinally as some jacketed lead bullets. I experimented with a lot of different grain bullets. We could achieve 4 inch consistent 5 shot groups at 1000 from a good shooting system in a good environment. They are not much better for counteracting the wind conditions. A few shooters have made them work in the smaller calibers. I know they had to go deep to get tight groups. I assume the "Borerider" disciplines were included. It would take an unlimited rail gun to make it work like Lou's due to weight requirements.
In my experience, they need to be pushed very hard to keep them stable. My conclusion is there are better bullets out there for the smaller caliber match restrictions than solids. I know there are some very smart scientists and balisticians out there still working on exoctic ideas searching for the elusive "Magic Bullet", most supported by government funding. I know of at least 3 guys with CNC machines in my area trying smaller caliber solid bullet designs. I have tried many of them. I wish them well.
greg

 

[jerrysharrett]

Greg, you are saying to push the bullet harder. Doesn't this just increase the spin rpm. Would going to a 1/2 or 1 twist faster on the barrel help on this problem.

On making solids. That will eliminate some of the nose irregularity I feel caused some of the "jumping out". I know in about 1994 or so Remington Arms bought some Hitachi-Seiki CNC lathes for the Loanoke Arkansas plant for just that reason, making bullets from solid materials. They failed to produce the desired result in REPEATABILITY required for premium quality hunting bullets.

I've had some 40 years dealing with NC/CNC machining and so far no one has made a machine or a feedback system that would take accuracy to the 6th decimal place. The 5th decimal place REPEATABILITY is not close enough for target quality bullets, IMO. It probably takes tenths of millions to machine bullets to the required repeatability, 0.000001" or better.

 

[Blaster-37]

Jerry,
I believe the 4th decimal will work. The magic is in the design. I believe the "Borerider" was the best new design at the turn of the century although it had weight distribution issues. There were also limited powder options available. They have a lot better powders and materials available out there now.
There have been some very smart people working on this. Some have worked with different materials like a hard cores and soft shells, "jacket", etc. They were trying to find the sweet spot in weight/ balance distribution. There are some government labs out there with some really cool toys including using a completely controlled environment, many chronographs, super high speed cameras etc. It is an underfunded science. When I was there working with explosives testing, I was able to see their very long range tunnel and equipment, very cool but I did not ask for or was given proprietary information although I dreamt about tuning in there. It was like the warehouse on really good steroids.
I do know of some designs that I have personally experienced 1 MOA higher with slightly better groups using the same weight and load as some very good jacketed bullets. I did not have enough of them to test some different tunes. These were CNC turned brass bullets with cores. The problem was consistently getting the right materials and somebody to pay 7.00 to 13.00 per bullet.
Get outside the box, experience an epiphany, design a perfect bullet that all the supercomputers did not see and you may change the rifle ballistics world. Heck, they probably already have the answer and are not interested in releasing it to the public. Why should they?
I believe jacketed lead bullets are like the "cap and ball technology" with way too many variables and will be replaced by something much more accurate in our time. I hope somebody will come up with the feasible "magic bullet" we can all use without internal or laser guidance.
Have fun.
greg

 

[jerrysharrett]

I told the guys at Loanoke years ago that they might turn the bullets 0.001 or so oversize then push them through a swage die and get the desired diameter...they do have to be very close to the same.

 

[Dave L Kiff]

The first Borerider design that I ground was in the early 1980s for Skip Talbot back when he broke a couple World records with a 50BMG that had a bore rider with the width of my grinding wheel as the second step. I remember him standing next to me bragging about his two door Mercedes yapping in my ear while i was trying to hold .0002 on his reamer . He grabbed the tool said good by to Keith Francis and I and on the road to Nevada he went to try it out. I ground bore riders in the 50 BMG for about every 50 FCSA record holder up to our present day Lee Rasmussen , he broke them all I think. Well about Six years ago I started a formula on bullets per Projectile weight and length on regular jacketed bullets. Its been a success so far with everything from 338 Lapua's to 22 rimfires with with the 14 different caliber family's we have 6 pending, Tied or confirmed World records, not to shabby for needing perfect conditions . I will set back and watch in the next few years and see what happens . To date the two combinations of the Rogue shoulder formula and my bore rider have been absolutely remarkable, hell it turned the old 303 British cartridge into a record contender in Europe . Well that's my time, back to finishing wildcat prints so I get home . Thanks Dave

 

[Hal]

It's always great to read what people are testing.

Hal

 

[jerrysharrett]

Dave tell us more about this Rogue formula, and, do you have anything like that for the 6PPC?

Jerry