Tech data sheets; what is "Bumping"?

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  • Last Post 27 June 2015
cheatermk3 posted this 24 June 2015

I've been participating in CBA matches for a few years.  I joined the assn. because I wanted to more fully participate in the matches.

Recently, a question that I have yet to recieve a definitive answer for was discussed, briefly, here:

http://noebulletmolds.com/smf/index.php/topic,800.0.html>http://noebulletmolds.com/smf/index.php/topic,800.0.html

See replies 7 and 8 . 

Just what info is to be had in answering the tech sheet question: “Bump"?

That is, just what is meant by Bumping a boolit?  Is tapering the transition from the nose(bore riding) section to the driving band(body?) to be considered “Bumping"?

I, and some of my friends answer this question on the tech data sheet “No” even though some taper their boolits to match(or try to) the angle at the origin of the lands.

So, is this correct?

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John Alexander posted this 24 June 2015

This question can better be answered by someone who does it.  But the first thing to know is the is that the term “bumping” is used to describe at least three different but similar operations. If I remember correctly back in the late 1970s CBA shooters with molds producing bore riding type bullets with under sized noses found that they would sometimes shoot better if you mashed them a little extra in the lubrisizer to fatten up the nose.  They called it bumping. in engineering this is called upsetting, but bumping it is now. This lead to a lot of broken lubrisizers because with hard bullets and small noses this took a lot of force.

John Ardito gets credit for coming up with the system that many top CBA shooters now use. His method involves making a tapered throat and a die with the same reamer.  When the bullet is mashed into the die the result is a near perfect fit in the throat. This should be called swaging but is usually also called bumping.

Some shooters use a die to just taper some part of the bullet short of swaging it into the die.  Someone doing it maybe will explain better.  But this is often called bumping as well. 

I hope other will add to or correct if need be.

John

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cheatermk3 posted this 25 June 2015

Bump-up, Swage-Bump, Taper-Bump?

 

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RicinYakima posted this 25 June 2015

Yes, Mike, we do it all. What ever it takes to make the casting a smooth tight fit into the throat. If you are moving metal, it is “bumping".

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OU812 posted this 25 June 2015

Taper bumping helps remove cast bullet imperfections and fit the throat much better when bullet is jammed against rifling. Ardito got a lot of the credit for doing this with his less taper bullet/throat designs. Lots of his designs were cut by Donald V. Eagan.  I cut a blank sizing die of same bore diameter using the same PTG custom throater used to cut throat in barrel. I use my RCBS press to bump just enough to form nose taper better, then tap the bullet back out using flat snug fitting drift punch. My 30 caliber bullet (accurate 310-200g) has a .75 degree per side or 1.50 degree included taper. So far my groups has been more consistently accurate with this style throat. Longer bullets work best (more accurate) from my brief experience.

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OU812 posted this 25 June 2015

Here is my taper bumping set up. PTG blank 30 caliber sizing die and shortened Lee sizing stem. Entrance to die was flaired a little for better stem alignment.  Blank PTG dies can be purchased at Midway. The drift used to remove bullet can be made from soft steel rod with tip hollowed and filled with epoxy to form to nose better.   I believe this will also improve some bore riding designs by making bore riding section more concentric. My 30 caliber die came with a bore diameter of .2995 and can be opened larger using 600 grit paper, dowel and drill. I may cut a .218 and .2995 die just for bore riding bullets.

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frnkeore posted this 25 June 2015

This discusion came about because of the confusion between the term “sizing” and “bumping". The term “sizing” was used for tapering the bore riding portion of a bullet in a CBA equipment list.

I had always concidered “sizing” to mean that bullet is made smaller (any portion of it) and a parallel surface is generated by doing so.

So, should there be a difference in reporting between the two terms?

Frank

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John Alexander posted this 25 June 2015

Frank wrote: “I had always concidered “sizing” to mean that bullet is made smaller (any portion of it) and a parallel surface is generated by doing so.

I think most CB shooters think of sizing as you describe it. I would like to hope that at least we could agree to use that term as you defined it and not fling it about willy nilly to mean whatever strikes our fancy.  But with people calling upsetting or swaging a bullet in the throat (to get measurements) pound casting when we all know what casting is and isn't doesn't make me optimistic.

Sticking to some standard definitions would make it easier to communication with one another and reduce the kind of confusion that started this thread. But if we would rather invent term as we go -- I can live with that too.

John

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cheatermk3 posted this 25 June 2015

Quote: ...Sticking to some standard definitions would make it easier to communication with one another and reduce the kind of confusion that started this thread. But if we would rather invent term as we go...

Well That's kinda where my head was at when I started this thread.  If there is more than one commonly accepted definition  then answering the question “Bump” with a    “Y” or “N"  does not convey information.  If one reason to have tech data sheets (TDS) in the first place is to share information then a simple yes/no answer is at best meaningless, if not downright misleading. 

So to my way of thinking, there are 4 possible answers; bumped nose up, swaged, tapered and “no".

So, maybe they could be abbreviated: U=upset or “Bumped up" S=swaged(formed in a custom, throat-matching die) T=tapered, referring only to the transition from nose to drive band. N=no, that is, only the diameter of driving bands reduced in a standard type sizing die.  Nose left as cast.

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RicinYakima posted this 26 June 2015

However, none of those options are available on data sheets, so, for me, if I do anything other than size in a standard lube and sizer die, it is “bumping". When you are picking nits, you have to define what is a nit and what is a louse.

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cheatermk3 posted this 26 June 2015

If there is no one definition why bother with an answer?  It's just noise.

 I guess I'm new enuff at this not to have realized that of course the high-scoring shooters are bumping in some manner or form otherwise they'd not be shooting so good.

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John Alexander posted this 26 June 2015

RicinYakima wrote: However, none of those options are available on data sheets, so, for me, if I do anything other than size in a standard lube and sizer die, it is “bumping". When you are picking nits, you have to define what is a nit and what is a louse.

Rick, Your response on our current data sheet is a rational action but as cheatermk3 points out it doesn't really convey much information.  If we want to help people reading match reports understand what is actually being done I don't think specifying the shooter's type of “bumping” is nit picking.  It seems to me that post #9 defines the nits and lice pretty well and would tell more specifically what is being done.

I will pass post #9 on to the the Board and suggest that we consider modifying the tech data sheets to be more specific about what the loading techniques are.  Maybe there are other ways the tech sheets could be improved.

Any suggestions for refining the suggestions in post#9 or other suggestions for making the tech sheets more useful would be welcome.  After all if we are going to fill them out they should be as specific as practical.

This forum is an ideal to have that discussion.  What say ye?

John

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John Alexander posted this 26 June 2015

cheatermk3 wrote:  I guess I'm new enuff at this not to have realized that of course the high-scoring shooters are bumping in some manner or form otherwise they'd not be shooting so good. Not all of them. There are lots of ways to skin a cat.

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Ken Campbell Iowa posted this 26 June 2015

  • bumping * only means you hit something with something else .... not too much interesting information conveyed there ... ( g ) ...

similar to saying ” i red-hatted it ” or ” i blue-hatted it ” ....


as mentioned before, it is not useful to redefine ” bumping ” ... more useful would be a short description of the results of any modifications to a previously cast bullet .

or at least a column headed * casting modified ? *

ken

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OU812 posted this 26 June 2015

My new taper nose 31-200g bullet pictured above shoots just as accurately as cast without bumping.

I have taper bumped some of the steeper angle Lee designs just to see if it helped accuracy...and it does help, but...................?

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RicinYakima posted this 26 June 2015

John and CheaterMk3,

The classes in post #9 are fine, but how would you describe what I do? I shoot the Lyman 311284, non bore riding bullet the most. This is how I do it: 1. sized and lube the bands, 2. size the nose sides straight, 3. taper the front driving band to 1 1/2 degrees included angle?

OU812 is using bullet design to do about what I do, but with no mechanical operations. With the custom mould makers, there are hundreds of different .30 mould today that most folks don't know they look like.

Although the shooters would hate it, I think a narrative description of anything other than just straight size and lube would be nice.

p.s. Didn't mean my first post to sound “snippy” or insulting, I just don't always write so that it comes out humorous like I intended. Sorry.

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pat i. posted this 26 June 2015

I always considered bumping an operation where there's a stop on top of the die so the bullet expands in certain areas to fit the throat. I used LBT bullets and just used a die to taper the forward portion of the bullet for the same fit so never said I was bumping on the tech sheet. I used to just say tapered. I personally wouldn't say a bullet is bumped unless it was done in a die with a mechanical stop on top of the bump die but to each their own.

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Ed Harris posted this 26 June 2015

I have always felt that bumping or swaging was a way to make an as-cast bullet which doesn't fit, more compatible with a rifle's throating, and to square the base of a bullet cast from a defective mold which doesn't produce one.

If the mold drops bullets as-cast to the proper dimensions and contour to fit the throat, bumping isn't needed. Why anybody would persist working with a defective mold which doesn't cast to size or produce square bases is beyond me!

With the high quality and affordable cost of custom lathe bored molds, which enable you to fit any barrel, it makes no sense to buy a cherry-cut mold produced using 19th Century technology and to have to fiddle with it, spending more on bumping dies and crap than you did for the mold, to make it work.

I think adding more info to the tech data sheets is just mental masturbation because every barrel is different and what works for one doesn't necessarily work with the other. Of course, I must confess that I haven't shot in CBA competition for years, because I no longer value having thousands of dollars in rifles and equipment which are used for nothing but bench shooting, needing a cart and a pony to get from the pickup to the firing line. Whatever floats your boat.

I think that Giorgio in Italy has the right idea with his emphasis on classic hunting rifles, revolvers and cowboy guns, having fun shooting steel targets and chasing the deer and the wild boar. To me the proof is on the barbeque and not on the backer.

If anyone has a recipe for steamed target papers stuffed with risotto, mushrooms and wild rice, I'm willing to try them once!

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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frnkeore posted this 26 June 2015

When I started shooting with the CBA, in 1987, the term bumping was generally used for most peoples attempt to match the bullet contour to the throat angle but, bumping was also used to bring undersize, bore riding noses up to land diameter or larger. In those days, a lot of people used the 311041 and it was “pushed” around, quite a lot.

Now a days, you can get most any kind of bullet mold and a mold number with the makers name attached will tell everyone what mold to order and use.

I would suggest the terms:

Taper bump Size bump (parallel implied) Size (parallel implied)

Check as many as needed.

There is no detailed description in the terms but, the space is limited on the data sheet.

You could add a space at the bottom to cover bullet details. Inforcement is also a issue, many just put “own” for things like bullet, throat and catridge and other things.

Frank

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Maven posted this 26 June 2015

 "I have always felt that bumping or swaging was a way to make an as-cast bullet which doesn't fit, more compatible with a rifle's throating, and to square the base of a bullet cast from a defective mold which doesn't produce one.”  ...C.E. Harris Years ago Ed Wosika/The Hanned Line offered a custom die which would do that plus flatten the gas check or base and alter the nose (added a meplat) if you wished.  It produced what frnkeore calls a “taper bump.”  I still use it and it consistently turns undersized and underperforming CB's into accurate ones.>

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pat i. posted this 26 June 2015

Ed Harris wrote: I have always felt that bumping or swaging was a way to make an as-cast bullet which doesn't fit, more compatible with a rifle's throating, and to square the base of a bullet cast from a defective mold which doesn't produce one.

If the mold drops bullets as-cast to the proper dimensions and contour to fit the throat, bumping isn't needed. Why anybody would persist working with a defective mold which doesn't cast to size or produce square bases is beyond me!

With the high quality and affordable cost of custom lathe bored molds, which enable you to fit any barrel, it makes no sense to buy a cherry-cut mold produced using 19th Century technology and to have to fiddle with it, spending more on bumping dies and crap than you did for the mold, to make it work.

I think adding more info to the tech data sheets is just mental masturbation because every barrel is different and what works for one doesn't necessarily work with the other. Of course, I must confess that I haven't shot in CBA competition for years, because I no longer value having thousands of dollars in rifles and equipment which are used for nothing but bench shooting, needing a cart and a pony to get from the pickup to the firing line. Whatever floats your boat.

I think that Giorgio in Italy has the right idea with his emphasis on classic hunting rifles, revolvers and cowboy guns, having fun shooting steel targets and chasing the deer and the wild boar. To me the proof is on the barbeque and not on the backer.

If anyone has a recipe for steamed target papers stuffed with risotto, mushrooms and wild rice, I'm willing to try them once! I haven't shot BR in a few years either but I think the same can be said about throwing money at the bunny gun idea when there's plenty of perfectly good over the counter guns out there that fill the same shoes. Some for under 250 bucks brand new. But like you said.....whatever floats a person's boat.

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