making bump die

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  • Last Post 22 January 2019
porthos posted this 16 January 2019

copied the pictures of the bump die made by  OU812 . but, i'm still confused as to there construction. can anyone draw a cross section diagram and post it and describe what each piece does

porthos                

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OU812 posted this 18 January 2019

It's squeezes the bullet fatter and more round using a precision machined RCBS style top punch. It's actually very simple. Calibers larger than 6mm require a catch cup to extract and catch bullet after bumping. Smaller caliber bullets simply fall down thru primer slot cut in ram during extracting.

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OU812 posted this 18 January 2019

Sometimes I will size down a bore riding section of bullet smaller using the NOE sizer before bumping more round. Yes it does improve accuracy and so do does the lost art of water quenching and more velocity.

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OU812 posted this 18 January 2019

Softer Aluminum RCBS style top punch works best. Some harder more brittle steels will crack and split. I use 12L14 steel for the die body, but aluminum should work also?

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Ken Campbell Iowa posted this 18 January 2019

i use decent aluminum ( 6061 t3, 2024, 7075 ) for die bodies including 44 cal., so far so good.   aluminum is not best for a thinwall nose punch, but ok for a thick wall nose punch design. 

rock hard alloys are essentially not swageable.   common " hardball" not heatreated is ok.

one benefit to aluminum is it is easy to cut and i usually wind up making several variations of everything .  i find it is easier to just start making  something even if wrong ... then usually even before you are done, you see how to make it better ....  

i might mention that a theoretically perfect swaging die set is very complicated, and corbin earns their money .... however, a slightly flawed homemade cast bullet die set can make your casting about as good as a casting can be, and can be put together for 1/10 of the time/cost.   

our ultimate accuracy problems with cast is not because the bullets are that bad: it is what happens to them when we shoot them ... ( g ) ... 

just some thoughts, ken

 

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OU812 posted this 18 January 2019

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OU812 posted this 19 January 2019

 

 

Shell holder removed and flat plate laid on top of ram to bump.

Plate removed to extract bullet. Larger diameter bullets require a catch cup machined from delren plastic.

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OU812 posted this 19 January 2019

This method works verywell with long bore rider bullets, but can also taper bump using extra step. Machining top punch for close precision fit to bore is important (.001 undersize works perfect)

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porthos posted this 19 January 2019

 

OU812:  a little clearer now (almost)  i assume that the bolt is to act as a depth stop? but, why the "o" ring?     the item that is 1.2 inches long with a hole. does that act as a spacer and hold the top punch?. if so, why not make a longer bolt and eliminate the spacer? and, last; i've already started on a couple things to make push thru size dies. i annealed several shell holders. made them soft enough to turn down in the lathe. eliminated the rim notch , and turned down to a flat surface. i hope some day to be able to post pictures!

thanks

porthos

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OU812 posted this 19 January 2019

The Lee flaring die is locked down using Hornaday lock ring. The bolt determins how much the bullet is squeezed (usually 3/4 turn inward from TDC). The O ring prevents bolt from spinning in die after setting. You could machine end of longer bolt flat and drill 17/64 hole in end, but the floating spacer works best I think. Making the RCBS style top punch is the most difficult part.

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OU812 posted this 19 January 2019

Just use your imagination. You may have easier and better ideas. Such as a different top punch design that does not require drilling the 17/64 hole.

I use the RCBS shape so I can use in my Lube a matic.

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OU812 posted this 19 January 2019

Here is my taper bump die (.310 diameter, .75 degree per side). Extraction punch is machined to align nose and not damage. Die was made using a blank PTG 30 cal case sizing die...check bore diameter.

Some of the longer 30 caliber bore riding designs (Accurate moulds) can benefit by swaging down to fit bore. Order an over size mould to cast large and do so. Or bump an undersized bullet larger by hammering downward on extraction punch while ram is at top dead center...or using other die design to squeeze fatter.

 

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Ross Smith posted this 19 January 2019

OU812: Do you swage these base end up and pointy end down? I always envisioned this the other way around, meplat up.

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OU812 posted this 19 January 2019

Pointy end up.

Why is this stuff so hard for some of you to understand. I never graduated from high school and this stuff is easy to me.

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Ken Campbell Iowa posted this 19 January 2019

OU812 ... really nice work, .... and nice lesson !! .... ken

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OU812 posted this 19 January 2019

Thanks Ken.

McMaster Carr sells the chucking reamers to cut bore and band diameter when sizing bore rider bullets. These reamers are available in most every diameter in .0005 increments. The taper reamers can be purchased from Manson, PTG etc. The tail stock on lathe must be centered before drilling and using the chucking reamers.

FIT IS KING! Bullet must chamber inline and fit snug.

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Slug Gun posted this 22 January 2019

A simple drawing of what the inside of the dies look like would sure make it easier for us new guys to understand what’s going on here. 

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