Bullet Design - Bore Rider Variations

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  • Last Post 25 March 2022
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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John Alexander posted this 23 February 2022

I am disappointed that Bill's  post above hasn't started any discussion about which of the features above make the most sense in which types of chambers. I don't feel like I have much to contribute.

When I designed the bullet I use most of the time the drawing I sent called for a taper on the front band. and the mold maker did a good job of following the drawing. However, to fit an earlier rifle's throat better I lapped out the front band to a larger diameter and in the process most of the taper disappeared. For the newer rifle it seems to work but I don't know what I would do if starting from scratch.

I do have one comment on the four designs.  In designing a bullet starting with the shape of a bus may be giving away in BC then needed to get enough bearing length.

I know Accurate can't or won't or doesn't like to make molds for pointed bullets but they do reduce wind drift. On the other hand a lot of top shooters do just fine with those big flat spots on the front of their bullets.

John

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RicinYakima posted this 23 February 2022

I have nothing to add, as I don't find bore riding bullets more accurate that the 1906 Ideal designs. My go to .30 is the 311284 that has always shot better for me, in my 1903 Springfields, than the 311299. CNC lathes are not capable of making pointed bullets. 

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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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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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OU812 posted this 24 February 2022

My bullets always shot better (more accurate) when compressed more round...bore riders or tapered 

 

This bullet shot very well after taper squeezing and aligning the tip of bullet...of course throat was cut to match bump die using the same .310 diameter .75 degree per side thoating reamer. Franks bullet is lightweight, so recoil was not bad. Do you guys remember Frank? I wonder how he's doing?

 

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Wm Cook posted this 24 February 2022

Hey OU, what’s that little .040 groove for in front of the last driving band? Or is that a lube groove? If it isn’t a lube groove is that like the Egan design? And it’s funny that the CG/CP is dead on the groove. Just wondering, still learning. Bill.

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

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lotech posted this 24 February 2022

I've always enjoyed cast bullet experimenting, but never to the point of incessant ruminating over the smallest (and sometimes insignificant) details. I'm quite content with the self-imposed limitations to my Goober approach to perfection, but keeping the "fun" aspect intact is important to me. This less-than-impeccable strategy may be the reason I've accumulated so many .30 caliber moulds in the last several decades. 

One .30 caliber design I've been working with off and on for the last year or so has been the Eagan MX3-30 ARD. I have no idea what the dimensions, taper, etc. are offhand. I'm sure the design specs are listed in my Eagan catalog should I ever need them. I ordered this mould at least thirty years ago but didn't work with it extensively until recent times. Like all .30 caliber rifle bullets, I run the Eagan wheelweight alloy 200 grain bullet through a SAECO .311" die. The sized bullet is around .3105" or so. 

I use SR4759 powder and load to a velocity of just under 1700 fps in a Ruger 77V and  Remington 700 VS. Both guns were purchased new more than thirty years ago and are unmolested, straight-out-of-the box. I don't know anything about the chambers except that I must use a different OAL in each rifle so that the bullets will very slightly engrave. 100 yard five-shot groups of under an inch aren't difficult and sometimes they're much less, but I can't do that consistently. Such accuracy is less than what serious accuracy enthusiasts require, but it's quite adequate for me. 

The MX 3-30 ARD is a good design worth trying. I would guess with all the custom mould makers we have today, someone has copied this design or makes something very similar. 

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barra posted this 13 March 2022

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?

Keep the base at the end of the neck. Straight OD - 1/2 thou of the free bore through to the leade and use the top of the lands to rub the nose diameter.

Would that be the ultimate for that particular rifle?

Thinking of a plainbase bullet.

or did I miss something?

Would it work or worth trying?

 Thanks.

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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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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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Tom Acheson posted this 13 March 2022

After shooting in over (256) CBA BR matches, I never filled-in the data box on the Tech Data Sheet that asks for the nose diameter. Never paid attention to it or bothered to measure that area of the bullet. But now I will. My latest project requires the bullet nose diameter to be reduced so that portion of the bullet can enter the bore when the round is chambered.

If the nose is left as-is, the OAL of the cartridge is way too short.

Just one more lesson along the road of enjoying this hobby.

Tom

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Wm Cook posted this 13 March 2022

Tom, which bullet are you working with?

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

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Tom Acheson posted this 13 March 2022

Mr. Cook,


This is a .22 BR. The bullet is the same one John uses, NOE 227-79-SP. It drops out of the mold (10 bhn alloy) at 0.228” on the driving bands and the nose varies between 0.220” and 0.2228”. A pin gage says the bore is 0.218”. I probably will try a 0.218” nose size bushing. Might consider a 0.219” also. A harder alloy would probably produce an even larger nose diameter.

Tom

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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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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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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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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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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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