Bore Rider Design

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Wm Cook posted this 08 January 2022

Disclaimer; I've been shooting cast for 30 years but it's only been in the past two years that I focused on cast accuracy. In short I'm not smart enough to eat at the big people table when it comes to cast accuracy.  But to a degree I'm smart enough to listen to what they say and I do catch the occasional cuss word.

Two years ago I would have flunked the test for the definition of bore rider vs bearing surface.  Even today there may be a dispute about where bore riders design ends and bearing surface begins. But I hope we can start out with the expectation that bore riders must make contact with the lands.  between 20/1 and Linotype are a couple of variables that makes this a pointless to argue over.

Borerider accuracy: Pieces of the puzzle started to fall together when Covid hit and I started to spend a lot of time at the bench.  After a through weeding out of my gun safe I wound up with a new Savage 10F in .308.  That led to a second 10F in .308.  That was the start of the rabbit hole that had me hooked on the number of variables that must be controlled for accuracy. Not many will argue that cast accuracy is significantly tougher to achieve than jacketed accuracy.  And although I'm talking about bore riders I believe the majority of folks will agree that a properly fitted tapered design will be more accurate then a borerider. 

From Ken

i have always thought that bore riders are a good way to get down to about 1 moa, but full groove diameters necessary to get much under that

But I hope to have this thread focus on boreriders because it is user friendly for a number of shooters.  I think tapered design is better but there's a steep learning curve to understanding bullet to throat fit. 

A couple years ago the only competitive mold I had was a Lyman 311299.  This is a borerider design.  I may be way off base but it strikes me that the freebore design is a good middle of the road choice for a production rifle.  As long as the freebore can take .310 sized shanks you can get the gas check at the bottom of the neck and you should be reasonably accurate.  I believe the freebore design started with the Springfield four groove barrel way back when but I'm not a historian, ballistics expert or a machinist so others know a lot more than me. 

Unique to the .308 rig I'm working with is that the bore is oversized.  As best I can tell the bore on this barrel is ~ .3014.  I've tried to measure bore (tip to tip lands) every way come Sunday and its hard as heck for me to get an actual measurement on the bore.  I've tried measuring, using a small bore gauge, pound cast, chamber side bullet tap and even  reverse engineering guesstimate to see where the lands contact the nose (non bore riding bullet) but everything boiled down to an estimated ~ .3014 bore.

My two cavity Lyman 311299 drops similar bullets with a ~ .2985 to ~ .3004 nose.  The dimensions differ through the length of the nose but you get the picture.  With some support from someone on the forum I was hand fed the how to beagle a mold.  I haven't received my certification yet on Beagling but I've come far enough that I can compare nose to lands tolerance as an independent variable to cast accuracy.  

Results: Four five shot groups with a proven load were shot side by side. Lyman 311299 weighted to the .1 grain, #2 Lyman, 23.0g H4198 ~ 1760fps, Fed 210 primers, Can Bl lube, .335 bushing, sized .311.

  • ~ .2985 to .3004 nose diameter aggregate 2.285" MOA
  • ~ .3010 to .3014 nose diameter / aggregate of 1.453" MOA

I may be the last person on this forum to figure this out but I believe that bore rider tolerance is as critical to accuracy as olgive to lands is with jacketed bullets.  Where jacketed accuracy is found by starting on jam (.001 to .002 of sticking on a new barrel) and then backing off in increments of .002/,003; optimum bore rider accuracy may be found with nose to land tolerance of +/- .00025.  And although alloy (#2 Lyman vs Linotype) gives us a variable to work with, the alloy source is critical.  

OU812's design for sizing the nose seems like a big step towards to finding that sweet spot.  Beagling is another choice.  There is always the alloy and of course you have Tom who can cut anything you need for bore dimensions.  A custom mold and playing with the alloy can give you +/- .00025 to work with. Maybe the tolerance isn't as tight as I think.  Maybe .0005 impression of the lands on the nose is good enough.  Maybe .00075" is right.  Then on top of that throw in the typical BS / SS (Barrel Specific / Shooter Specific) factor and you have an interesting puzzle. 

Unique to my situation is that I have a tight freebore.  Instead of the SAAMI .310 I had ~ .3085 on each barrel.  My guess is that this bullet will never be competitive in the barrel I'm putting it through. That's why the bullets are seated down to the shoulder.  Thanks, Bill. 

Here is the difference between the .~.300 vs the ~.3014 nose on the bore of my rifle.

 

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Spindrift posted this 08 January 2022

Thank you for an interesting post!

Nice to hear your mould modification turned out well!

I have a .35 caliber bore- rider where I use another solution to the problem with an undersized nose. 

This is a CBE 360-300, the nose is about .349 in my (scrap) alloy. First, I size the nose in the NOE bushing sizer, using a .349 bushing. This doesn’t really size the nose, more clean up the mould seams. Then I powder coat the bullet, which adds about 0,002in size. Then, I run it into a .351 bushing that even out the high spots that might be there. These bullets shoot very well with 45 grs Vihtavuori N150, actually one of my most consistently accurate load.

 

The NOE bushing sizer is an excellent, clever tool. The nose sizing function, though, has clear limitations. If you try to size down 0,001in, you’ll cut a ring of lead that’ll end up by the front driving band. It is a marginal tool for minimal modifications.

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John Alexander posted this 08 January 2022

Wm Cook,

Very interesting statement of some of the factors to be dealt with in fitting a bullet to a throat. I hope it leads to productive additional discussion.

As you have observed threads on a forum tend to go in all directions often getting off on to a completely different issue. I am not so green that I think this can be entirely prevented, or in some cases or that it is always a bad thing, but it, maybe, can be partially avoided with a a good definition of some key terms.  I believe that most on this forum understands what a bore riding bullet is, but I think your definition of the two approaches below would help keep us on the same page.

Properly fitted tapered design

Freebore design 

John

 

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OU812 posted this 08 January 2022

Squeezing the bullet to a more perfect round shape and then fitting to throat can be rewarding. You can make a simple die using aluminum rod. Drill then ream the aluminum to desired size. Hardest part is machining a nose punch to fit bullet tip perfectly. You can sqeeze bullet by striking with rubber dead blow hammer, but i use a press. It would be nice if NOE moulds would sell such a die since they have CNC 

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OU812 posted this 08 January 2022

The trick to reaming is you must stop the lathe when extracting reamer because it is still cutting.

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John Carlson posted this 09 January 2022

I also use the NOE nose sizing dies.  I found that it helps significantly to touch the entry with a tapered grindstone then polish the die with 2000 wet-or-dry with oil.  Finished product is about .0003 oversize. Lead slicing is not a problem when reducing diameter up to .002 with lube sizing 311299/314299 bullets.  I use the same treatment on Lee push through sizing dies and find no need for lube.

I have not yet found the sweet spot and generally cannot identify a measurable and repeatable improvement in accuracy with nose-sized bullets vs the same bullets as cast.  Doesn't mean I won't keep trying and I will certainly be following this discussion.

John Carlson. CBA Director of Military Competition.

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Wm Cook posted this 09 January 2022

I believe that most on this forum understands what a bore riding bullet is, but I think your definition of the two approaches below would help keep us on the same page.

Properly fitted tapered design

Freebore design

In the OP I asked about bore riders. It's simple and doesn't have the controversy of ball fitting.  I was hoping to stick with bore riders on this thread.  I'll start another thread about tapered design because that seems to be an area where a lot of progress can be made.  And that's an area where there is a lot of controversy.  Impassioned myths will be intermingled with statically valid results.  And its also one of the remaining pockets of "tricks" that can give a shooter a competitive edge.  So in hopes of keeping this thread on track I was only speaking of true bore riders.

Cast bullet design will continue to evolve as accuracy is pursued.  Perhaps the bore rider design is not as susceptible  to change?  I'm not a historian but as I understand it the Springfield 4 groove barrel was one of the first to benefit from bore riders.  I have not researched this further.  Maybe others on the site can give us a better of the historical place bore riders paced in cast bullets.

To me it seems that there are two obvious dimensions to fiddle with on a bore rider.  The shank diameter and the nose diameter.  Using common numbers like .310 for the shank and .300 for the bore fitting nose would be common in a 30 caliber mold.  A simple definition would be that a bore rider bullet's nose is the same diameter as the rifle bore.  Full load bearing only occurs on the driving bands.  The nose is controlled, leaning against, or bouncing off the lands dependent upon the tolerance between the bore and the diameter of the nose. 

I am politically dodging the variable of a bore rider driving band seated into the lands.  Not that that's a bad idea.  The Lyman 311299 looks more like a 30-06 bullet than a .308 because of its bullet base to front driving band. But if the driving band will pass through your freebore on a .308 you could put most of  front driving band >.100" into the freebore and have the bullet base in the bottom of the neck and nearly touching the lands with a production rifle throat.  SAAMI specification is .310.  My freebore is .3084.  A common .30 cal bullet size is .310 so there may be a conflict on some chambers. 

What I'm trying to learn is if anyone is using the nose diameter as an independent variable to tune for accuracy.  OU812 is an emphatic yes. His method of pressing the nose into a round uniform shape and diameter will work but it will be hard for the average reloader to replicate.   The NOE die is another choice.  But if I were tuning a load by varying the tolerance of the nose to the lands I would have to be able to readily adjust it to shoot a simple 2 x 2 design method.  Linotype vs #2 Lyman may give me that.  I don't have enough experience to say that I will truly gain .0005 with Linotype.  I'll know about that in about 4 weeks.  

I know I'm always making apologies like "gee if only I had...." but I am a born tinkerer and get my jollies manipulating variables to see if there are statically solid results.  Its easy for me to dream about a bore rider design three cavity aluminum mold from Accurate.  One cavity each .299, .300 and .301.  Then cast with both #2 Lyman and then with Linotype.  Combine those 6 variables with dependent variables (powder, charge, case, weight, COAL etc) and you could wring out the value of +/- .0005 on a bore rider nose. That would give you a 6x study that would be statistically valid.  A tapered design may still be more accurate but for ease of use the bore rider bullet is attractive to a lot of people.

Final note on bore riders: Accuracy will try to cut any nose diameter you want.  His tolerance for dimensions on bore rider nose is +.000 and - .001/.002.  He tries to be within tenths of a thousands on the dimensions requested but results are too convoluted when you add in the alloy that's used and user specific casting methods.  Note: he does ask for the alloy you use so compensation is fudged in to reach the dimensions you need.

The following is the drawing for Tom's 31-175 bore rider.  It is a good example of how a bore rider looks.  I have his original drawing that has all of the dimensions on it on the right. 

Just cause I'm a geek I would like to point out the .245" where the top driving band starts and .355 where the top driving band ends.  This bullet makes it a good fit for the .308 Winchester. which has a neck length of .303.

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OU812 posted this 09 January 2022

John Ardito was an engineer, machinist, gunsmith. So he had done lots of experimenting. He could machine a chamber/throat to any of his ideas. I bet he had lots of barrels and reamers laying around in his shop.

I wonder if ever experimented compressing the bullet to align the nose.

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Wm Cook posted this 09 January 2022

OU I will never match your knowledge of what can be done with reamers.  I have to reverse engineer to visualize what the freebore, leade looks like. 

But the bore rider is such a simple affair that getting the nose to the right dimension is doable.  You're compression method would work if you knew what diameter you wanted.  You could make a stepped improvement with one bushing but trial and error would be needed to get the tune right.  .If I were talented enough and if I could operate my lil Jet lathe in my shop I could probably turn out several bushings and do a side by side study myself.

Wouldn't it be funny if the next step in cast accuracy was a high velocity, hard, heavy, long bore rider compressed to uniformity and sized to get the most out of the bore/nose fit.

IMHO iIf the relationship between diameter of the nose and the bore is as important as I believe, tI would guess that there may be a  50% improvement (not just a .5 MOA improvement) in group size.  The definition of group size in this case is the aggregate of four 5 shot groups.  All of the foundations for accuracy (casting, handloading and bench discipline) would naturally need to be in place,

Then again, maybe cast accuracy buffs have already passed on the bore rider and are focused on finding the right combination to seat the bullet into the throat with a tapered design.  Take care, Bill.

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OU812 posted this 09 January 2022

Your posted picture of the as cast bullet will deliver standard boring accuracy. You must try something different. What size bullet do you think you need. Maybe I can machine a die to fit your gun and make you some more perfect bullets from my mould. Will have to dust off the mini lathe...not easy.

What is the length of your freebore, testing has shown longer freebores work best. My old Remington had the NATO chamber with long .190 freebore length...gun shot really good until i ruined it by lengthening freebore too long.

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John Alexander posted this 09 January 2022

Wm Cook,

Thank you for taking the time to explain what you have in mind and how you intend to do it. I am glad that you are confining your plans to the bore rider type bullet. I think it has proven its superiority in factory rifles by its popularity in our military matches and in Production and HNR classes.

I also think it is seldom tried in the full race guns in Heavy, UNR, and UNP. If everybody is using the Ardito approach then that approach will win the match. I wonder what the full potential of the bore rider is if given a good try with the high priced guns?  Your proposed experiments should get us a little closer to the answer. 

A few random bits from 40 years of shooting bore riding bullets that may or may not be useful: Hard bullets will not seat with more than the light land marks. Soft bullets seem to shoot better with heavy engraving, but not so much that you don't get firm contact in the throat by the first driving band. Rounding of the bullet edges and pretty big wrinkles in the bullet seem to have no effect on accuracy down to about 0.8 MOA and maybe beyond.

Good luck with your experiments.  We will look forward to your results.

John

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OU812 posted this 09 January 2022

John, Have you considered rebarreling your 6mm ppc to shoot 30 BR. You could turn down the larger case rim of 30 BR to fit your smaller bolt face. This way you would not have to buy larger bolt face. Then experiment with bore riders.

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Tom Acheson posted this 09 January 2022

 

There’s a lot of interesting information being exchanged here!

 

Those of you who shoot in the CBA matches have seen the note on the Tech Data sheet asking for the bullet size diameter and the NOSE diameter. I’ve never included the nose diameter on the many tech sheets I’ve filled out. After reading this post, some people who read the match results might find the nose diameter an important data point. From my uninformed perspective I concluded long ago that if the bullet is being engraved by the rifling, what does the nose diameter matter? Dumb question time….are there bullets whose surface is 100% bore riding and no engraving takes place? Probably not, otherwise why is rifling present? If the bore ride area is short, how much does guidance does it impart on the bullet? I assume (probably incorrectly) that the role of the bore ride area is to help guide the bullet and help keep it centered in the bore.

 

I’ve used a bump die on several of my previous rounds. The stem in the die that provides the effort to eject the bumped bullet, has a conical recess machined in the end of it. So that the recess does not damage the bullet’s nose, a soft lead “slug” or molten lead is inserted into the recess. Then as bullets are bumped, the soft lead deforms, taking on the shape of the bullet’s nose. Over time, this soft lead “nose forming material” needs to be removed and replaced.

 

The bump die can be adjusted to position the start of the tapered area on a bullet. On a single lube groove bullet, this location has been on the middle of the driving band above the lube groove. The taper on the bumped bullet matches the “taper” in the chamber (not a factory rifle) so the “fit” is a cone in a matching cone. I guess this is one form of “bullet fit”.

 

FWIW

 

Tom

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MP1886 posted this 09 January 2022

John, Have you considered rebarreling your 6mm ppc to shoot 30 BR. You could turn down the larger case rim of 30 BR to fit your smaller bolt face. This way you would not have to buy larger bolt face. Then experiment with bore riders.
Personally myself I'd keep the 6mm PPC, it's a great little cartridge.  "There are bore riders that will work in it. 
Not your 6mmPPC,  but I built a match AR15 in 6x45 and shoot cast from it exclusively.  It's deadly accurate. It's gets to be quite boring. I shoot a bullet using a mold from Mihec. 

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RicinYakima posted this 09 January 2022

Download PDF of Secrets of the Houston Warehouse By Dave Scott Precision Shooting Magazine Special Edition 1 1993
Download Full Article – Secrets of the Houston Warehouse By Dave Scott
Originally Published in Precision Shooting Magazine Special Edition #1 1993

29 years old now, but jacketed BR shooters have not beaten these in outdoor matches. 

FWIW, Ric

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OU812 posted this 09 January 2022

John, I agree with your statement, sometimes I speak before I think. Although for me the smaller 6mm would be harder to machine dies for. Lots more bullet choices in larger calibers. Accurate does not offer a 6mm option...I think. NOE is a good option.

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MP1886 posted this 09 January 2022

John, I agree with your statement, sometimes I speak before I think. Although for me the smaller 6mm would be harder to machine dies for. Lots more bullet choices in larger calibers. Accurate does not offer a 6mm option...I think. NOE is a good option.
Saeco and Mihec do.

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OU812 posted this 09 January 2022

Tom A.,
I have seen your legendary groups in the Lyman reloading manual. You do know what your talking about.

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Tom Acheson posted this 09 January 2022

OU8,

Wish I could take credit for the groups in the photo. That is my rifle. The targets are examples that I collected over a couple of summers from CBA Postal match entries. I toss out targets that I scored but sorted those in the photo to be from shooters using the noted Lyman bullet and powder.

As a Postal scorer, I get to see a lot of targets. The event I score is called a “season” event, meaning you shoot and send in targets for scoring in May, June, July and August. Most of the CBA rifle categories are available. Heavy and Unrestricted don’t always have the smallest groups, as one might anticipate.

Using that photo at the start of the chapter was an attempt to get non CBer’s attention and maybe read the chapter.

Experienced CBA match shooters would not be surprised by the groups, especially if you have attended the CBA National Tournament.

Tom

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John Alexander posted this 10 January 2022

I have considered rebarreling my 6PPC to 30 BR and other calibers as well. If it weren't for the slow twist of my present barrels I would try to get a suitable similar to the 22 bullets I am using. But the slow twist would require a short CB and you don't see many short CBs in the winners column for good reasons.  Long bullets are easier to achieve good alignment upon seating and also provide higher BCs,

The other reason is I enjoy shooting practical hunting rifles in competition.

OU812 is right there are a lot more mold choices. Most mold makers won't make 22 molds and won't consider 22 spitzer molds.  Fortunately we have NOE.

John 

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John Alexander posted this 10 January 2022

Tom asks:

"If the bore ride area is short, how much does guidance does it impart on the bullet? I assume (probably incorrectly) that the role of the bore ride area is to help guide the bullet and help keep it centered in the bore.

===

The answer to your question is -- less than it needs to be. I believe your assumption is correct about the role of the nose.  That is why a good bore riding bullet should be mostly snout. The longer the better, in my opinion. 

John

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