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Thread: Analysis of cast boolit weight variences

  1. #21
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    More on the subject with range testing.........

    I loaded up a bunch of Lyman 457-132 Postell boolits that my Pedersoli 1874 Sharps shoots extremely well.

    Using a 6X Leatherwood Malcolm scope at a range of 200 yds, here are the results that various weights have on accuracy. Totally unscientific as there simply aren't enough shots fired for a real statistical analysis. But interesting none the less.....

    Bullet Weight Test #1, 5 shots, 200 yds, 24g SR4759, .010" away from lands, 525.3 - 525.9 bullet weight


    Bullet Weight Test #2, 5 shots, 200 yds, 24g SR4759, .010" away from lands, 526.4 - 526.8 bullet weight


    Bullet Weight Test #3, 5 shots, 200 yds, 24g SR4759, .010" away from lands, 527.3 - 527.8 bullet weight

    BTW, that is two boolits into the hole at 9 o'clock....

    Bullet Weight Test #4, 5 shots, 200 yds, 24g SR4759, .010" away from lands, Random Weights 521.3 - 535.6 bullet weight


    All were shot over a Ohler 35 chronograph.....

    The ave velocity of the 15 weight sorted boolits was...1206 FPS
    Extreme spread of 41 FPS, SD of 14.......

    The ave velocity of the RANDOM weight boolits was...1221 FPS
    Extreme Spread of 42 FPS, SD of 15

    Comments on any of this????
    Roy B
    Massachusetts

    www.rvbprecision.com

  2. #22
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    OK, once again the fine folks over here on CB got me thinking........Thinking about contact pressure of the mold handles that is. So I decided to figure out a way to keep this constant.

    Gussy makes a great set of "Constant Pressure handles", but I'm inpatient and want to do some casting tonight.

    So I built these:



    And I wrote a whole "How To" article on my web site if you want to make a set for yourself......Didn't take me an hour, beginning to end.

    www.rvbprecision.com

    Now I have to try them out and see if they improve things around here!

    Roy B
    Massachusetts

    www.rvbprecision.com

  3. #23
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    Quote Originally Posted by rbertalotto View Post
    More on the subject with range testing.........

    I loaded up a bunch of Lyman 457-132 Postell boolits that my Pedersoli 1874 Sharps shoots extremely well.

    Using a 6X Leatherwood Malcolm scope at a range of 200 yds, here are the results that various weights have on accuracy. Totally unscientific as there simply aren't enough shots fired for a real statistical analysis. But interesting none the less.....

    Bullet Weight Test #1, 5 shots, 200 yds, 24g SR4759, .010" away from lands, 525.3 - 525.9 bullet weight

    Bullet Weight Test #2, 5 shots, 200 yds, 24g SR4759, .010" away from lands, 526.4 - 526.8 bullet weight


    Bullet Weight Test #3, 5 shots, 200 yds, 24g SR4759, .010" away from lands, 527.3 - 527.8 bullet weight

    BTW, that is two boolits into the hole at 9 o'clock....

    Bullet Weight Test #4, 5 shots, 200 yds, 24g SR4759, .010" away from lands, Random Weights 521.3 - 535.6 bullet weight


    All were shot over a Ohler 35 chronograph.....

    The ave velocity of the 15 weight sorted boolits was...1206 FPS
    Extreme spread of 41 FPS, SD of 14.......

    The ave velocity of the RANDOM weight boolits was...1221 FPS
    Extreme Spread of 42 FPS, SD of 15

    Comments on any of this????
    Actually, this is PLENTY of data points for a potentially interesting regression analysis, but I'm not sure you can make anything from it as you've done it.

    This reminds me of something that's bothered me before in my own testing. Really, the order of the different weight "settings" should be randomized (don't do all of a weight range at once), and/or sequential so you can separate thermal, fouling, wind convection, and maybe other effects from the effect of weight, don't you think? If the weight settings are more evenly distributed over time then cumulative and time dependent effects are more easily averaged out to determine the effect of just your weight parameter...

    Also, my supposition would be the primary differences between the different weights of bullets would be related to internal and not external ballistics, and so I would be tempted to reduce your range for the shots down greatly to reduce any impact of wind, etc., and make trips downrange less time consuming.

    It was interesting that you shot the last group with various weight settings, but that might have been more informative if you noted which impact corresponded to which weight. I think a better experiment would have been to order your load block with rounds of known weight in random (or evenly distributed) order, then put one shot each into sheets of graph paper with a printed aiming mark. I would have tried to have a fairly dense/uniform distribution of weights over the weight range of interest. Later you can extract POI for each shot and do a regression analysis.

    Also, if you were going to go to this much trouble after weighing each, I probably wouldn't have coarsened your weight data by just blocking bullets. Why not keep track of the weight of each as exact as you can measure if you are going to go to all the trouble?

    All of this would have been more work...
    Last edited by DrB; 07-08-2011 at 04:51 AM.

  4. #24
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    Roy, checked out your website and enjoyed the projects. Think I may have to do the PID. Was wondering though why you left the original system/thermostat/rheostat that came with the pot in place?


  5. #25
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    Thanks DrB. Lots of good "thinking points" in your post. As I practice with the gun more and more, I'll keep better track of what is going on, I would think that after a while, a theme will develop that we can analyze.

    I'll stay on it.

    As far as modifying the lead furnace. The "dial" on both of my pots is simply a rheostat. They are not any type of thermostatic temperature control. So simply setting them to "High" effectively removes them from the circuit. I'm not aware of any of these casting furnaces having any type of thermostatic control.
    Roy B
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    www.rvbprecision.com

  6. #26
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    I have done several tests using boolits that are visually as near perfect as I can make them and grouped in wt ranges of under half a grain, 1/4 gr IIRC. They shot good but I still had fliers and my unsorted groups were still usually only slightly larger, some were decidedly smaller! My conclusion? Well, I think air voids are an obvious issue. Another issue MIGHT be length. When we size boolits we're actually swaging them. The larger diameter a boolit, the longer it will be for a given finished diameter- unless, I think, we're compressing air voids. So there are couple things we might want to add to the testing-

    Group them for wt. before sizing
    Group them for length before sizing
    Group them for length after sizing

    Maybe that will add a new dimension into the results.

  7. #27
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    Thanks Bret,

    But I have to discount the air void issue. If you look at my boolits, they all fall within a relatively small range as a percent.

    But then I have what I call "Bad Boys"..........(I was going to call them BFBs...Big Fat Bast...ds). These boolits are all MUCH heavier than the norm. I'm hoping my "constant pressure" pliers will resolve this issue.

    I've cut apart my lightest boolits and I've not been able to find any voids.

    Next step will be to measure the length of these BBs after sizing to see how much they actually grow in length. You might be on to something here.
    Roy B
    Massachusetts

    www.rvbprecision.com

  8. #28
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    Interesting discussion so far. While I haven't progressed into rifle boolits yet, I am quickly getting my feet wet on pouring up several different calibers and weights for my handguns. This past Wednesday, I sat down, and set up the pot with my newly acquired thermometer stuck off in the alloy, then I cleaned and lubed my 6 banger mold up, and slid in the probe from to monitor that temp as well. Turned on the digital read out and sat the mold up to pre-warm as the alloy melted.

    Once thing got up to my previously marked setting on the Lee 1-10 dial settings, I started checking temps. I ad previously marked my setting when I poured my initial batch of Lee 300gr boolits for my 454 and figured this would be an easy way to remember.

    This said the WW alloy reached 675 as a top end temp on the thermometer. I allowed plenty of time for it to stabilize and started to pour. The mold temp was initially 215 degrees and the first couple of pours resulted in some wrinkles. It warmed up quickly to 310-320 before I noticed frosting just starting to form on the noses. At this point I really wasn't counting seconds between pours I was just simply running things up to see about where things started to change.

    So I cooled the mold down to about 295 and poured two full loads as the 10 second timer reset the temp on the meter. So now I was using the 10 second delay between temp checks as a timer. This proved to be fine and allowed me to cast around 6-8 pours before I had to once again cool the mold with my fan.

    I poured up close to 60 or so before the sprue handle called it quits and broke off even with the bolt. So not to let a good thing pass, I simply swapped molds and went on to another Lee 6 banger for the 210gr WC 41 cal TL. For this one however I had drilled the hole out for the thermocouple to me inserted in. So I just poured until I had about 6 or so through it and cooled it down a count of 20 in front of the fan, then resumed again until the TL grooves started to get a bit frosty.

    I ended up with a bit over 50 of the 41's before I decided to try out yet another mold I had found off in a box of shelved stuff and just cleaned up. It's the Ideal 358311 160gr RN. THis being totally new to me is a well used old mold. I figured I would throw out a bunch just to see how they poured and how they might shoot in my TC's 10 and 12" barrels. Anywho I close to 60 of them keeping the temp in the pot sitting around the initial 675'ish area.

    Sorry to have put up such a prefix to this, but I'm new to all of this and working hard to get my feet under me and on to producing consistent boolits to be utilized for hunting. This said, I had hoped from reading the initial post that by weighing out my newly cast boolits I would have come back to hopefully find quite a few comparisons among the post on accuracy variations from separating by weight, or keeping the temps in an average span to produce boolits of certain weights more consistently. Don't get me wrong, I am still very interested in this, and know from a couple of other treads that I'm on the right track.

    My results were as follows with my little bitty sample,

    On the Lee 300's I randomly grabbed up 15, which averaged (8)306.20grs +/- .02. The heaviest of them weighed (2)308.10 and the lightest was (1)301.70. The other3 were between 304 and 305.8.

    On the 41's out of 20 grabbed from the pile, I had (9) @ 213, (5)@ 214, (3)@ 215 and the rest were under 211grs.

    For the .357's I snagged 10 which went (5)@163, (3)@ 162 and the other 2 under 161.

    So I realize I don't qualify for the most detailed study, but what did strike me odd twas that most folks rarely if ever even weigh their handgun bullets. I might be anal about a few things, but figured that if I was gong to go through all of this to "make" my own bullets, that I should at least throw in some QC, other than simply looking them over just to make sure they don't have holes in the bottoms.

    Should I even make this effort to weight out and separate them? Is it really going to mater at ranges of 50 - 100yds, with boolits ranging from 140grs thru 310grs? I'm not shooting matches, but I generally do my best to load my ammo to match quality if possible. So is it reasonable to expect the lower velocity rounds to shoot good even with the weights being separated by a decent spread of say 4 or more grains?

  9. #29
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    Great post Mike. Thanks for taking the time to do this.

    I just statrted using a BBQ thermometer on my molds. Result will be posted as I cast more boolits.
    Roy B
    Massachusetts

    www.rvbprecision.com

  10. #30
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    UPDATE:

    Results with "Constant Pressure Pliers Handles"

    I finally had a few moments to analyze the results of using the constant pressure handles I built;




    As you can see. Huge improvement. 3.7g variation. I'm still not sure how you folks are getting 1/2 grain variations. I have a long way to go to get there. But this is huge for my stage in the game.

    Here's a quick video of how the pliers are connected to the temperature probe.


    http://public.fotki.com/Rbertalotto/.../p1020782.html


    BTW, I found my best bullets were cast with the "1-20" Allot at 750 degrees and the Lyman mold at 425 degrees..........

    Thread on the constant pressure handles:

    http://castboolits.gunloads.com/show...ht=rbertalotto
    Last edited by rbertalotto; 07-10-2011 at 06:06 PM.
    Roy B
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    www.rvbprecision.com

  11. #31
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    Well I dumped a bunch of 300gr boolits yesterday minding the pot temp and mold temps as posted above. I haven't gotten a chance to run them over the scale just yet as there were simply too many of them to deal with last night. I also dumped quite a few of the 230gr RN TL ones for my 45 which will also get weighed up. I'll post my results as soon as I get them weighed.

    Also found that my thought of using a 1# Folger's plastic coffee bucket for storage might have to be dedicated to something else, as when I was done picking through the 300's, I had it full enough I could just snap the top on and then could hardly pick it up. Those darn Lee six bangers sure are nice to use,but they sure do empty the pot quick.

    Oh yea, in the above post I noted that I started to see some frosting on the boolits when the mold temp got up to around 320 degrees. Well it turns out that is was actually caused by a heavy area of soot from when I sooted the mold. I noted it again yesterday, and stopped and checked the mold. I dusted it ever so lightly with a fine hair paint brush and cured that right up. Not like the other boolits will shoot any different from it as it was purely superficial, but the ones from yesterdays pour were all very pretty.
    Last edited by 41mag; 07-11-2011 at 05:55 AM.

  12. #32
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    Mike, if you could plot them like I did above, that would be greatly helpful to the cause.

    Thanks
    Roy B
    Massachusetts

    www.rvbprecision.com

  13. #33
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    I have had funny results weighing boolits and sorting them. I never remember shooting better and seem to have more luck just taking them out of my box and using them as is.
    So after reading this I took my 320 gr 45-70 unlubed boolits and weighed them. I only had 50 left. Most were within .2 gr in each pile, many were exact. From one side to the other the highest weight change was .8 gr and I had three piles.
    These were from my home made two cavity mold and ladle cast.
    I don't think the scale will ever be put to use weighing boolits again!
    I suppose little bitty boolits should be weighed but will they vary more then store bought J word things?

  14. #34
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    I must be doing something wrong or it's the salt air here on the east coast. I'm all excited when I see a 3.8g variance over 130 bollits and folks are telling me they are seeing a two tenths of a grain variance!

    I suck at this boolit casting stuff.............

    My Benchrest rifle, custom boolits (J-word) will be within .3 to.5 grains for a 65 grain boolit out of a box of 100. It amazes me that folks are seeing smaller tolerances with heavier boolits with all the inherent variables that lead casting introduces.

    Onward and forward!
    Roy B
    Massachusetts

    www.rvbprecision.com

  15. #35
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    I am NOT a target shooter, just a hunter. I do weigh my rifle bullets and reject any over 1% + or -. A 400 gr bullet is accepted if it falls between 398 and 402. I average 50 bullets and apply the 1% rule, load and go hunting. For handguns, if it looks good it shoots good. Works for me.
    45 AUTO! Because having to shoot someone twice is just silly!

  16. #36
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    I agree on the handgun boolits. And just about any boolit shoots "good enough" out to 50 yards.

    But it's those 600 yd shots that really get your attention and all the little stuff gets exagerated.
    Roy B
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    www.rvbprecision.com

  17. #37
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    For a BPCR rifle the weighing makes sense. The difference on the rams will be enough to matter. For 100 yard shooting I can't se spending e time worrying it. Then again I am not a bench shooter.

    This is definitely one of those niche things in casting. I feel the same about your constant pressure handles. For BPCR they make sense, for a hand gunner, no way.

    With weighing you will need to pay close attention to slight changes in rhythm, pot temp, etc. So many things can give that slight variance you want to avoid. You are truly trying a very technical, difficult area of casting. Good luck.

  18. #38
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    With weighing you will need to pay close attention to slight changes in rhythm, pot temp, etc. So many things can give that slight variance you want to avoid. You are truly trying a very technical, difficult area of casting. Good luck.
    Well for me, my personal goals are simply to be able to control what I am pouring and get somewhat more consistent results from it. As far as sitting down and weighing every single bullet I shoot, nope ain't going to happen. I know form past experience that event eh factory J's vary sometimes quite a bit, but I still am able to shoot tiny groups with carefully developed loads. This said, I at least know they have some sort of tolerances that they allow, and also QC most of their products.

    This is simply all I am doing, gather enough info that when I set up for a pour, I know within reason that by keeping this, that and the other consistent, I will end up with at least something VERY close to what I had before. Since this is all new to me, I gotta start somewhere and this doesn't seem such a bad place to start.

  19. #39
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    OK, I'm going to ask if no one else will that doesn't have a set of those "gussy" handles. It seems to me there should be two wooden handles instead of one as you generally expect else how are you going to keep your right hand from getting burned. I looked a them on Cabintrees' website and couldn't help wondering. Maybe I'm not getting the right picture. I know gloves help but maybe that's all that's needed.
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  20. #40
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    Ok here is my contribution to this. I ended up with 286 from yesterdays pour.

    I separated them in 2gr increments, starting at 300grs, and going up to 310grs. The lightest one I weighed was .297grs, and it went with the other 6 culls I tossed as I went through them for the second time.

    So here is what I ended up with,


    Top row was 300 - 302grs, second row was 303 - 305grs, third row was 306 - 308grs, and bottom row was 308 - 310grs.

    Out of these I noted that the second column contained around 75% weighing 305+grs, the third column contained around 80% weighing 307+grs, and the last one contained roughly 50% at 308+grs and the others at 309+grs, with only one hitting the 310 mark.

    I doubt very seriously that I would ever notice the differences in them if simply loaded and shot. However, it is nice to know that even with my rookie pouring I am still pretty darn consistent with keeping them mostly within roughly a 3 grain span. I have to give credit to the folks that posted up previously on what temperatures they normally pour at and what they try to keep the molds at as this was around the same area I was pouring mine at. Keeping the pot between 675 and 700 and the mold between 300 and 335 for the most part. There were times where it reached up to 350 but this was usually when I loaded it up when it was already pushing 330, and the added pour would jump it up.

    So there ya have it. I am happy with my results, and will probably simply pour from the second row down back in the 1# plastic can and wait until I am ready to lube size and shoot them. They should make some pretty nice hunting boolits for sure. The others will go back in the pot to be poured again, and hopefully hit the mark a little better with the second time round.

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