Bullet Design - Bore Rider Variations

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Last Post 25 March 2022

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Wm Cook posted this 20 February 2022

Like most everyone getting into cast accuracy with a long gun I found myself going down the rabbit hole of bullet fit to bore. Believing that there isn't a great chance that I would be able to create a unique design that would set cast bullet accuracy beyond what it is I looked at what other people had created. For reference I stuck with Accurate molds because of the CAD drawings and the flexibility for anyone to tweak existing drawings. Since I'm working with a Production Class .308 I looked at bullets in the 200 to 230gr range.

Accurate has 84 bullets listed that would fit in that group. The most popular design is the bore rider which has 55 listings of which 34 are the traditional straight nose design (Sample A), 4 that are of crush design (Sample B), 10 that are hybrid and 7 that I would fit into the "Other" category.

I'm curious if anyone has any history on these designs, possibly the correct name for them (not my "crush", "hybrid", "other"....) and the individual benefits or virtues.

As far as I can see sample A is a straight up bore rider . This is a slight variation of the 311299. Two areas that differ from the Lyman are the .180 flat nose as Accurate produces and the slight bevel from the front driving band to the nose. I think most all of Accurate's designs has this slight bevel where the driving band is given a short ramp into the freebore, lede or the face of the free-bore if you have a tight free-bore. Tapers are as short as .010 but some like Tom's 31.200L are just a little longer. This one has a .020 lead into the straight nose design.

Sample B has a similar transfer of design from the driving band into the straight nose but the taper is longer at over .050". Almost like a ball nose or a spitzer its almost like its designed to crush into the lede as the straight bore rider nose is suported in the lands.

Sample C is what I call a hybrid between a full out tapered nose and a bore-rider. On this one there's a long linear taper from the front driving band to the straight bore-riding nose. In this case the taper runs .135 which looks to me like it would run through the free-bore of most production chambers.

Sample D is confusing to me. The design is very popular because Tom's sold over 40 of them. For the life of me I can't wrap my head around the purpose of the design from .300 to .550 where it then transfers to the bore-rider straight nose design. And that little lube groove between .400 and .460 confuses the heck out of me. Maybe, just maybe this has to do with CP, CG? Probably I'm looking for something that isn't there or just not smart enough to understand its importance.

I can see the benefits of the modified bore-rider designs as it is filling the free-bore area with lead which will give the bullet more traction in the lands. This is my attempt to inch into the subject of variations on the bore-rider design and thus bullet design in general. Thanks, Bill Cook

A “Measured Response” is as effective as tongue lashing a stuck door.

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Boschloper posted this 15 March 2022

To build on John's comment "some successful bullet lubes don't make good lubricants", I have long felt that our bullet "lubes" were more "anti-fluxing agents" that prevented gas-cut droplets of lead from soldering to the bore ahead of the bullet than they are barrier film lubricants.

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Bud Hyett posted this 15 March 2022

Tom - I think I know of the Marston Ballistics Laboratory. Is this the same Marston, IL that is a small town near the Wind Hill Range? Was Ed Doonan a technician in that lab?

"Marston Ballistics Laboratory" - This was the name we used for the testing in the winter inside Ed's shop. and at the range the other days of the year. The testing was structured in that we set up a test with Mission, Goals, Objectives concept before we shot. I'd often spend Saturdays there, arriving in the morning with Ed already starting a test and working all day to discover or prove some concept.

Our biggest tool was the bullet recovery box, looked like a coffin for a python. Built principally out of two sheets of plywood, it was two foot square. The baffles were scrap foam rubber in the shape of the funnel of a fish trap with slots every foot. Oiled sawdust as no problem since Ed was a carpenter who had plenty and we both changed our oil. The first discovery was that bullets traveled in unpredictable lengths into the sawdust. This necessitated slots every foot in the top in the with a frame using waxed kitchen paper that pulled out so you could see where the bullet stopped.

Both jacketed and cast bullets were shot. Varmint bullets blew up in the foam rubber and were dropped. Cast bullets traveled into the first half with jacketed bullets going into the second half. The only bullets we tested that went to the end were the .45-70 Government 500 grain round nose at black powder velocities and the .30-'06 National Match load. Both dented the end panel. Shooting a Marlin 1895 with the RCBS 45-300-FN bullet at 1500 feet-per-second, this bullet didn't penetrate as far as the Government 500 grain load even with higher velocity.

Bullet Trap Testing:

Bullet penetration for distance in the box at varying velocities.
Bullet twist entering the leade and bore. Easily seen in the rifling marks.
Bullet twist with seating into the leade, off the leade, slightly touching the leade, .030 jump into the leade.
One test was the result of seeing the impressions of 2400 powder kernels firmly marking the base of the Keith 240 grain bullet. This was in contrast with the bore of the revolver having few kernels left in the bore after firing. We wanted to see how hard the primer ignition pushed the powder column.

Bullet hardness was tested.

Hardening by dropping the bullet into ice water from the mold versus using an oven was tested.
Hardening by air drying versus freezing overnight in a freezer.
Pure Linotype versus used Linotype versus 94/4/2 Pb/Sb/Sn alloy dropped into ice water from the mold.

Unfortunately, Ed's son after Ed's passing burned the notes from this time. I understand some pages were salvaged and I'd like to have a copy to see if I could resurrect the notes and publish in Ed's honor.

Note: Marston was a thriving small town up through the 1930's. Wheat grew in the area at 40 bushels per acre which was a good yield. Farmers were prosperous and the town was large enough to have a Ford dealership, several general stores, farm implement dealer, church (still there), and many houses. Then the wheat field suddenly would only yield 15 to 20 bushels per acre and the town began a slow decline. Today, the church remans and the place with all the partially disassembled trucks was once a general store. Ed joked that we would revive the town with the ballistics laboratory.

Farm boy from Illinois, living in the magical Pacific Northwest

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Wm Cook posted this 23 February 2022

I'm guessing that the design is where you start to cross over into the theory of how the bullet fits the bore, the bearing length and the BC out of the final design. All of the fitting in the world will not help beyond 100 yards if it has the BC of a dead cat. But since we're just kabitzing about this I'll stick to bore fit.

I believe John's bullet is a straight up D. Mos 85 grain bore rider. I don't have a drawing of it but I think he worked with NOE to have a reproduction available. So the numbers I took were from the NOS design. Their 227-79-SP GC has a BOAL of .982 with gas check. Of that there is ,275 that's full bearing length and another .340 that is leaning length for a total of .640 leaning/bearing length or about 63" of its total length. You can quibble whether leaning as good as bearing but at the end of a match the score/groups you post trumps anything.

I will add this. I shot a lot of different noses dimensions on two different bore riders this past three months. From ladel to bottom pour, from pressure cast to regular cast, Linotype to #2 Lyman, from non beagled to beagled and all combinations I could think of to change nose dimensions. I've reached a personal conclusion that the bore riders nose to bore fit is pretty darn important. On a gross miss match between bullet nose and bore I had a .300 nose going down a .3014 bore and there was a 40 - 50 percent improvement in group size when I beagled it up to .3015. And with a proper nose size you can feel the nose tension as it slides into the lands while still being able to extracted the loaded round. To me this was so obvious that if one chambered easily without this feel I would now be inclined to put it into the backstop rather than put it on record. I have zero proof of that. Just as I have no proof of weighing bullets but I do it anyway. But here's a spoiler alert. I am as new as a shinny penny and anyone of you knows way more than me.

And you also seem to need to keep a watch on length form gas check to the start of the front driving band. On the NOE 79 adn with gas check you have .220" to seat in the case. Assume maybe .020 from the case mouth to the free-bore wall leaves .200 in a .223 case neck that SAAMI spec of .203. I'm not sure what John's free-bore diameter is but from a distance it seems that the dimensions of the driving bands and a properly fitted nose to bore would shoot very well. And I guess that's maybe a bit of an understatement when you look at match reports.

I don't know what cartridge Ross is shooting but the driving band portion looks like its designed as a .308 or maybe a 30BR. The 31-190J as he said looks like a tapered design. It has a BOAL of 1.065, bearing surface of 40% and then what ever bearing assistance it gets in the .200" free-bore area of the bullet. Since the free-bore area drops about .010 in .200 maybe assume that .180" will be engraved, not just supported by the lands. If you called it that Ross would wind up with a bearing surface of 58%. Again, this is all hypothetical from someone has made about every mistake in the book. Well not every mistake. As of yet I haven't fallen off my bench stool. Yet.

Ross's 31-190J is another solid hybrid design. All all the tweaks and nuances that people have put into custom Accurate designs, there seems that a lot of thought put into blending the ease of the bore rider to bore fit with trying to fill up the free-bore area of the chamber right before the lede. In this case Ross has a fat .310 to .305 bearing surface out to .510" which gives it a full 50% bearing surface. Then it transitions into a bore rider and adds another .210 of leaning surface for a total bearing/leaning surface of 69%.

Ric's 311284 looks to me like a bore rider but I can't be sure. That too looks like a perfect match on 03 Springfield. His bearing/leaning surface may be pushing 80%

Another consideration is that I may be confusing apples and oranges when having a conversation with folks when one is shooting a vintage rifle with a vintage bore and someone else may be shooting a a new production Savage 12 with the throat opened up for 200 - 230 grain bullets and having a tight free-bore area. But were just talking here and we're not being scored or anything. Just a friendly conversation. Everyone has had their own experiences and the right to their own beliefs God bless the US.

All the numbers above were grabbed on the fly so if my math is out of wack I apologize in advance.

A “Measured Response” is as effective as tongue lashing a stuck door.

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Lee Wiggins posted this 13 March 2022

That little forward groove, look at the clone of the 311284 above. No lube in the forward groove. why put a groove at the rear of bore riding nose and front of the forward driving band. Just step up in diameter , right? No, I am pretty sure it is a "scraper groove", and its purpose is to scrape fouling from the bore and the groove is a place for fouling to go and be carried out with the bullet.

That's my story and i'm sticking to it. Lee Wiggins

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RicinYakima posted this 14 March 2022

Having cleaned maybe 50 1903 Springfield's that had not have the bore cleaned down to the metal since made, there is a lot of "stuff" in the barrel. I do know that reverse electrolysis will not remove it all without boiling water scrubbed through the bore also. There is so much porosity in the bore as the bullet passes down it, that they are never "clean". IMHO

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Ken Campbell Iowa posted this 13 March 2022

barra ..

your above noted scheme is usually the first choice in a serious attempt to getting best accuracy in a new project rifle.

most don't refer to a reamer drawing but just " cut and try " for best fit; checking for rub marks on a chambered bullet.

yes, the nose snug in the rifling, and the larger rear part of the bullet snug in the throat.

areas not quite defined are the " base of the bullet at the front of the neck " ideally the entire bullet is snug in the throat before firing ... as in * breech seating * ... but then you wouldn't have an actual cartridge ... the best compromise is to barely seat the bullet the least it will not fall out of the brass neck.

and almost always a well fitted gas check is more accurate ... probably because it stiffens the base and somewhat because it really is a * gas check * ...

***********

beyond a good fit ... which is a good start at 100 yards ... is the need for less wind dispersion at longer distances ... so as we try longer snug nose bullets, we run into more rifling drag upon chambering ... maybe taper it a little for easier chambering >> a compromise ...

then, if we use a long pointy nose to cut the air ... ... we might think that long pointy nose might sag sideways on firing ... and if the rear of the bullet isn't perfectly lined up at firing, that extra mass up front is going to continue to exit randomly out of the muzzle ... head off towards different starlings on a light wire, so to speak ...

***********

but yes, try for as snug a fit as you can ... at the chamber end. i think of it as the First ... and Only ... RepeatableRule in cast bullet accuracy.

usually repeatable, that is ... heh

ken

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Tom Acheson posted this 13 March 2022

It would be interesting to be a bullet and watch the relationship between the inside surface of the lands and the perimeter of the bullet as it goes down the barrel. Is the bullet always uniformly contacting the lands or is it "wobbling" with concentrated impact in one area and little or no contact in other areas?

Speculation is interesting but it makes you wonder what really happens? Does our attempt to understand surfaces, dimensions, behavior, etc. accurately play out to meet our perspectives? Does a real small group on the target prove our theories.....or is it just a coincidence?

Tom

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Larry Gibson posted this 13 March 2022

Tom

If it's a lubed cast bullet it is riding on a layer of lube. That's the why of it not leading the bore. Proven fact that lubed bullets come out at the muzzle .002 - 005 less in diameter than groove diameter. There should be little or no contact between the bullet and bore. Thus, the bullet is essentially "wobbling" going down the bore. It is my supposition that is why the greater the percentage of "bearing surface" to bullet length the better the accuracy will be....less "wobble".

LMG

Concealment is not cover.........

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John Alexander posted this 14 March 2022

Larry,

I certainly agree with you last sentence. I think the absence of short bullets in match winner's rifles seals it in general.

You also state " There should be little or no contact between the bullet and bore."

What is your take on the experiments I, John Carlson, and others have posted on this forum and published in TFS about unlined bullet loads up 2,000 fps produced no leading. John and I fired dozens of unlubed vs. lubed groups and found small differences in group size. John was shooting a variety of metallic sighted Springfields and my sight involved glass. John's were were ten shot groups averaging about 2" and mine were five shot groups averaging 1"

These results don't conform to the conventional wisdom about what actually happens so they have generally been ignored.

I would be interested in your and others comments?

John

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Wm Cook posted this 14 March 2022

No, I am pretty sure it is a "scraper groove", and its purpose is to scrape fouling from the bore and the groove is a place for fouling to go and be carried out with the bullet.That's my story and i'm sticking to it.

Lee that works for me. That's the first justification for the little groove that I have ever heard of.

Couldn’t one just use the chamber reamer drawing and put a lube groove or two. Draw a bit of a nose on the end of the top of the lands and call it good?

Barra that was my first though. Everything I heard hammered home the need to have the bullet fit the bore. Remember I'm only into cast accuracy for about a year now and I had to totally erase everything I knew about seating depth and jacketed bullets. I kind of think that's why the bore rider is so popular. Even if the nose is undersized and even if it's not touching the lands many shooters aren't particularly concerned. If it chambers and stays minute of deer at 100 yards it may fill the bill for them.

Like others have said, the bearing / leaning surface contact may be more critical when the accuracy expectations are raised. On the left is a bore rider that has a nose of about .300 out of a barrel that had a bore of about .3014. After firing you could see very VERY faint land tracks. On the right is a tapered bullet designs that looks to have a good fit to bore. One of the KC guys was nice enough to send me a few samples of that one so I could start to figure things out.

This was a fudged test because I had to keep the load subsonic so I could trap the bullet. At competition velocity I would assume there would be more obtrusion. I just did this to see if I could get a percentage of bearing versus leaning surface.

With the linear design of a tapered bullet you can come close to the dimensions you'll need by building an equation to determine the dimensions of the front and rear of the nose you need by taking the nose length, the throats freebore, the bore dimensions and you can order a custom mold. I used this on a tapered design mold I just got from Accurate and I was a little to conservative. I wish I would have gone another .0005 - .0007 on the tip of the nose.

With a bore-rider the closest I could come up with to determine true bore diameter was with a small hole gauge set. Then it seems that you have a little flexibility with alloys and casting methods to nuance it to where you can get a felt drag on the nose as its being chambered.

Then reality sets in when you find out that without a pointed nose the BC of what can be readily had with a custom mold becomes an issue. Maybe I'm wrong on that. Still got a lot to learn. I'm still trying to figure out bullet fit to free-bore, leade at 100 yards and get it to shoot competitively. Bill Cook.

A “Measured Response” is as effective as tongue lashing a stuck door.

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Larry Gibson posted this 24 March 2022

Certainly, have to agree with Ian's; " testing dozens upon dozens of formulas, compiling data, and studying the effects of many different lube ingredients begins to paint a picture of what substances work and which ones don't."

I conducted a test sufficiently to prove which lube(s) to use at HV which are readily available without a lot of at home "witchcrafting". Yes, I've made a couple of "home brews" myself but found it really wasn't worth the effort as I found no improvement over several commercial lubes available. Especially after reading the long lengthy trials and tribulations on the boolet and artful forums the now "artfull" crew has gone to. Can't say there really has been any improvement for all the effort. Actually, one of that artful crew has given up on lube and is PCing.

All that, whatever they chose to use, is fine with me. I keep reading their results, especially gear's results with PC, hoping to see a "breakthrough" that is worth using. Haven't yet but I keep watching.

LMG

Concealment is not cover.........

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John Alexander posted this 25 March 2022

I have just deleted a post in this thread. In my opinion telling someone who disagrees with you to stop talking about the subject i.e. shut up, is over the line. Disagreements are not attacks.

John

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Ross Smith posted this 23 February 2022

I have a John Ardito rifle that has a long tapered throat the same dimensions as your example "D". It does not shoot well with any other 30 cal. designs. The taper has to fit the throat for a good seal. Cartridges are loaded with the bullet seated out far enough that they are pushed back into the case mouth when chambered. My two most accurate molds are the Accurate31-155W and30-190J.

If there is no tapered throat, I don't think this design would work well. I don't now if Don Eagan was the originator of the tapered bands , but he made molds for John's rifles.

Just my opinion.

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Squid Boy posted this 23 February 2022

I designed this one for my Stevens 44. It has about one thousandth interference in the riding area and I believe it aligns well in my chamber and throat. It shoots better than some conventional molds I have and on par with a Hudson clone as well. I scaled up a couple for 45 and 50 caliber but haven't really worked on them yet. It seems to me that a bore rider is the easiest way to get decent accuracy in fixed ammo. Thanks, Squid Boy

"Squid Pro Quo"

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Larry Gibson posted this 13 March 2022

As to accuracy;

Agree with Tom and a couple others, the bullnose of a "bore rider" should be a tight slip fit in the bore so the front dive band can be seated against/into the leade. A couple here have mentioned that accuracy is improved when so. I also have found accuracy to be improved when the nose actually "rides" the bore.

Another consideration for any bore rider design is the length of the case neck and the length of the throat to the leade. Longer necked cartridges such as the 30-06 will often shoot more accurately with a Lovern, Ardito or XCB style bullet having maximum groove diameter bearing surface and minimal nose.

For hunting however, where weight of the bullet is also important and in the shorter "modern" length necks of many cartridges is where the bore rider comes into play the best. But again, the nose should still be a tight slip that still allows smooth chambering. Additional consideration for hunting with a bolt action is how well and reliably the loaded cartridge with said design feeds from the magazine; a full magazine and from both sides if the rifle has a staggered magazine.

I do remember frank (franknor ?) as I've had many a spirited discussion with him on this forum and the cast Boolet forum. He designed the NOE 311-160-FN which has a much longer nose than the NOE 30 XCB (310-165-FN). Frank claimed his bullet should perform just as well at HV as the XCB. Another member sent me his 311-160-FN mould (frank would neither send his mould nor any bullets) so I cast some up with the same care as i do the XCBs. Frank's 311-160-FN did not prove to perform well at all at HV. However, before returning the mould to it's owner i cast 500+ bullets for possible other use. Frank had stated his bullet was very accurate at the ASSRA game when shot at 1400 - 1500 fps. And so it is. I have been shooting frank's 311-160-FN in my M70 Classic 30-06. In fire formed cases with the flash holes drilled frank's bullet loaded over 10 gr of Bullseye runs right at 1450 fps out of the 10" twist 24" barrel. I've shot several 10 shot groups (100 Yards) that were right at 1 - 1 .5". With the right hold over hitting a 10" dinger at 300 yards is quite easy. Also hitting a 4" dinger at that range happens more often than not. Of course that is with decent wind conditions.

Thus, a lot of the "design" will, or at least should, depend on the intended use of the bullet.

LMG

Concealment is not cover.........

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RicinYakima posted this 14 March 2022

I don't know about the theory of wobble, but after 30 years I admit that the percentage of bullet land in the grooves and/or nose solidly on the lands, shoot more accurately.

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Tom Acheson posted this 14 March 2022

Larry.

If it's a lubed cast bullet it is riding on a layer of lube.

Hope I have this figured out. Since the nose is not lubed, it is not depositing lube on the top of the lands. But….the previous bullet’s lube that was in its grease grooves that got extruded out, did leave lube behind, on all of the surfaces in the bore. This is the lube the nose is “riding” on. Correct?

Tom

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Larry Gibson posted this 14 March 2022

"Tom Acheson posted this 1 hour ago

Larry.

If it's a lubed cast bullet it is riding on a layer of lube.

Tom"

That is essentially correct. Years ago I recovered numerous 311299s down range when the snow melted. They had been shot out of my M1903A1 match rifle I had at the time. The noses ran .298 - .299 and did not fit the .3015 bore (at the leade) . There was rifling indentations on one side of the noses but not on the other indicating the bullets had tipped in the bore during acceleration. The load used would give 2 - 2 1/2 moa accuracy for 10 shots at 100 yards.

I got a 314299 mould and the .302 noses fit the bore at the throat perfectly. The same load with those bullets gave 1 1/2 moa accuracy all day long. I used that bullet in that rifle (back in the early '70s) for local service rifle matches and did very well with it consistently shooting very good scores.

I my M1903A1 NM Type II I put together with a new 4 groove RA-42 barrel the bore is .300 at the leade with a .3105 entrance from chamber to throat. I use the 30 XCB bullet or the Lyman Lovern 311466 in it. Both shoot extremely well, better than the 311299 or the 314299, as neither has any bore riding nose and both have maximum bearing length.

LMG

30 XCB over 2400. Two sighters with sight adjustment and then ten "for record".

Concealment is not cover.........

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RicinYakima posted this 15 March 2022

And I go with "floating" gas checks.

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RicinYakima posted this 17 March 2022

Attached is the work of Harold R. Vaughn, PhD, designer of the US nuclear weapon housings. He was the author of "Rifle Accuracy Facts" that debunks lots of myths.

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