Tim, you could also say that it is better to be proactive then reactive in achieving consistency.
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Tim, you could also say that it is better to be proactive then reactive in achieving consistency.
I could also say, you have an absolute propensity for condensing 1000 of my words into two lines.Originally Posted by Doc Highwall
LOL!
Thank you sir!
Precision in the wrong place is only a placebo.
Well I keep learning! Now that I am actually paying more attention to what is going on, I see I need to change. I started weighing my bullets tonight, and was seeing weights from 408-410. Then I noticed that where the sprue was cut, sometimes there were little voids. Am I right that that comes from cutting the sprue too quickly? I looked for some that were not torn as bad, and sure enough, they all were at the top ends of my weight. Now they weren't torn very badly, but it seems like it was enough to vary my weights.
A dull sprue plate can do that also. When I cut the sprue I apply downward pressure on the sprue plate and twist at the same time.
There are a few things you can do to help that.
1. The trick is to control your temperature exactly and cut right in between the time that the puddle freezes and it changes color. It's nearly impossible to describe this via this post, so take my word that it is in that area. Just start experimenting with it, but be consistent with your experiments. A perfect cut is accomplished the same way everything else is when casting a perfect bullet. It boils down to temperature and timing. Your timing can be spot on, but if your temperature fluctuates, you're going to find yourself chasing rainbows, and the same is true if your temperature is consistent but your timing is off.
2. Use an excellent alloy such as described in the OP.
If you are casting with straight COWW, then add tin to the pot. Assuming you are using a fairly full Lee 20lb pot (15 pounds COWW), depending on the form your tin comes in, add as follows:
40/60 solder, add .85 pounds.
50/50 solder, add .70 pounds.
60/40 solder, add .57 pounds.
63/37 solder, add .55 pounds.
pewter, add .40 pounds.
Pure tin, add .34 pounds.
These figures are based on my experiments with XRF testing of alloys before and after making changes. I find I can pretty much call my shot when smelting if I adjust my alloy calculator to reflect COWW as having no tin at all and 2.3% antimony. It has been very consistent for me when smelting large batches of COWW and having the resultant alloy analyzed for content. I have found no trace of arsenic in my tests, or at least none that amounted to a measurable trace when the alloy was analized. For all intent's an purposes, COWW is 2.3% antimony, and 97.7% lead. Often, there is .1-.3% trash in there that could be almost anything up to and including gold, but whatever that .2% is, it seems to make very little difference batch to batch, so I ignore it. (Again, it is consistent, therefore, it is not an error.)
The tin will help you with fillout, and reduce surface tension, but it also helps you get a clean cut.
3. sharpen your sprue plate holes. You can accomplish this very carefully with a good quality knife, but the best thing is to use a very sharp, 90 degree counter sink. Either way, be sure to use 400 grit or finer sandpaper with a flat backer, or a flat india stone on the underside of the sprue plate to remove burrs and hone the cutting edges razor sharp. Your sprue plate is a scissor, and needs to be sharp. This should never be done to a sprue plate made of aluminum, because sharpening it cuts through the hard anodizing and will allow your sprue plate to dull rapidly and you will be replacing it very soon after.
4. Adjust the keeper bolt (if your mold uses one) so that the sprue plate is held tight against the top of the mold when shut. Don't go crazy here, but what you want is for the sprue plate to swing shut with light pressure until it contacts the keeper bolt oposite the hinge bolt. At that point, I like the sprue plate to be seated in place with a little more pressure. If you can't feel the sprue plate sliding under the keeper bolt, then it's too loose and needs to be tightened. There is a very good reason newer molds have a bolt head there instead of just a stop pin like the old Lymans used. Use it to your advantage to keep that plate evenly captured on both ends with the bases of all your bullets between those two points of contact. This will aid in consistent bases.
5. Like Doc Highwall mentioned, when cutting with a gloved hand, push the plate down on top of the mold, or if cutting by strikeing with a stick (or a small rubber hammer in my case) strike at a slightly downward angle to accomplish the same thing. Remember, your sprue plate is a scissor. When cutting with a loose pair of scissors, you naturally use the handles of the scissors to provide pressure to keep the blades in firm contact with eachother. Cutting a sprue is no different.
Last edited by MBTcustom; 03-06-2015 at 12:57 AM.
Precision in the wrong place is only a placebo.
The last thing the moderators need is me making work for them BUT; would it be possible to link Goodsteel and Sgt.Mike's posts into one sticky? Not that others have not contributed but their methodology is basically the scientific method applied to casting and it might give newbies a quick start.
I've shot a lot of Laser Cast bullet and for the most part they are excellent commercial cast bullets. Based on your sampling 35% of those bullets are way outside the acceptable weight variation parameters I've found through considerable testing to be necessary for accuracy at HV. The Laser Cast bullets are certainly just fine for regular 30-30 velocities but when you push them faster the accuracy (group size) will get larger.
"a 0.75" x 0.001" lead sleeve"
What is the 3rd dimension (required to get cu. inch or weight) you used to get the figures you computed?
If you randomly shot 10 shot groups using the 34 Laser Cast bullets from the sample you show the centrifugal force will cause a much larger dispersion in group size with the 1.5 gr variation than if you used 10 bullets from the 22 that weighed the same. Those 10 bullets of the same weight would more than likely shoot a smaller group, all other things being equal, than a random lection of 10 bullet from the 34. Bottom line is; the greater the weight variation the greater the imbalance. The greater the imbalance the greater the group dispersion will be. The higher the velocity, the greater the RPM is and thus the greater the centrifugal force is which is what causes the group dispersion.
Larry Gibson
That's very interesting information about commercial cast bullets popper, and I appreciate you posting it.
However, I still get the sneaky suspicion that you think I'm using this method to prove bullet quality, and I'm supporting a caster using it to check his/her bullets for accuracy, so he/she can keep the "good" and cull the "bad"?
That's not why I wrote this as I have repeated over and over (although, if you expect to shoot in extreme circumstances with your bullets, I think you'll realize a very real advantage to having them all be exactly the same weight, diameter, length, hardness, appearance, and seated with uniformed GCs).
This method can be used to cull bullets if you absolutely think it makes that big of a difference, but the fact of the matter is that if you can measure variances in weight and diameter, then all the variances that you cant measure are going to be much worse than what your scale or micrometer is telling you. If your process has been whipped to the point that you have found a way to reduce the occurrence of errors you can measure, you can be sure that you have also reduced the occurrence of errors that you cannot measure as well because all these things are tied together.
This process is used to reduce the consistency errors in yourself, not the bullets. You are the cause, the bullets are the effect. Observe the effect you can see to correct the cause that you may not see.
Fix the problem at the source, not the effect three steps away.
Last edited by MBTcustom; 03-07-2015 at 01:58 PM.
Precision in the wrong place is only a placebo.
"I will restate my original thesis - dimensional differences cause the observable weight difference (plus bad sprue cut) - you can't weigh the bubbles - if they occur. To imply you can is a fallacy."
With 30 caliber cast bullets of 150 - 180 gr from various moulds/designs of any ternary alloy I can easily demonstrate the accuracy difference of a +/- .3 gr difference in weight and can demonstrate it on demand from different rifles ("regular", sporters and target), especially when you push the RPMs over 140,000. Granted at "24000 RPM" the amount of dispersion difference probably isn't all that much if you get the bullet to stabilize at that low of a velocity (334 fps from a 10" twist)? However, at 140,000 RPM (1940 fps (in a 10" twist) the difference will be measureable. The higher the RPM the greater the dispersion will be.
I have, on numerous occasions, taken the bullets that measured .5 or more less than the average and filed on them and found bubbles. Those bullet do not shoot well at all. That is not a "thesis" but is demonstrable at will and thus moves from being a "thesis" to being fact which is not "fallacy".
Larry Gibson
In the bad old days, our molds were not always as perfectly formed as today. I would imagine that a relatively small difference in center of form and center of mass would be quite telling. John Barsness had a bullet spinner built for him that gave some sort of indication of dynamic balance. I wonder if he ever published data on measured out of balance vs rpm vs group dispersion. He is mostly a sptzer j type person but the data might be interesting.
Bryan Litz (Applied Ballistics For Long-Range Shooting) spells it out as do many other ballisticians as well as many reloading manuals (Sierra, Hornady and Speer). To quote Bryan Litz who puts it in verbiage we can easily understand, from his book on page 144 about a quarter of the way down the page; "Any imperfection in the shape, balance, or alignment of the bullet will cause it to disperse away from the bore line when it exits from the muzzle. The amount of dispersion is related to how severe the imperfections in the bullet are, and also how fast the bullet is spinning......The relationship between spin rate and dispersion is stronger for low quality bullets." Thus bullets with a 1.5 gr weight difference are going to disperse farther apart at a given distance than those with a smaller amount of weight variance all other things being equal. How much dispersion variance is going to depend on the size and location of the imbalance, the rate of spin (RPM) and the distance to the target. This why we also seek linear dispersion tests to see if dispersion is linear and if not the load is exceeding it's RPM Threshold.
Larry Gibson
Just a thought on an internal void. A "bubble" if you will. Like my mentors always say, you have to look at what is not there just as much or even more than what is there.
A small bubble of air is very very light and would not cause much of a difference. However, the bubble sized pocket of lead that is missing actually does remove a significant amount of weight from that location in the bullet.
Concerning weight sorting, I think a thread should be started on that subject, or against that subject, or both. That has very little to do with what I am doing here (as I have mentioned several times).
This is a discussion about proficiency and consistency at the pot by the caster, and a method he/she can use to improve themselves. Just because I'm telling people to line their bullets up in a row based on weight does not mean that I am advocating weight sorting. All I'm suggesting is that the bell curves can be used as a sounding board to find out where you are, and learn how to improve.
That said, as long as the bullets are all lined up nice and pretty, and I'm going to shoot them anyway, I confess I do scrape the weird ones off the bottom of the bell curve and throw them back in the pot.
Yep.
All 11 of them. LOL!
Precision in the wrong place is only a placebo.
An excellent bullet may not cure the shake while you're aiming, but a badly loaded round could definitely cause a shake after you pull the bang switch.
I was on the phone with a good friend tonight. He said something that cracked me up so bad I almost died. He said and I quote: "Just pour the hot stuff in the square thing!!!!"
Precision in the wrong place is only a placebo.
Moist dust huh.
I always thought it was something like throwing the alloy into the cavity so fast the air couldn't escape through the provided vent lines.
Regardless, the question is; can voids in the bullets be detected with a scale, and I proved conclusively that they can, along with a lot of other variances, but more like a general "health and well being" of the bullets as a whole. If you can't drop your bullets so that they appear consistent with the basic tools we have available, it's certain that the rifle is going to choke on them too (unless of course, you feed it carefully and limit yourself to low speed, low pressure, low RPM, low accuracy standard, etc etc etc.)
However, regarless of whether you demand perfect bullets, you should at least be demanding a casting proceedure that allows you to do your best, and you should always be looking to improve yourself. It's a fact of being human that if you are not progressing you are sliding backwards. There is no "set and hold" when it comes to skill. You are either getting better or you are getting worse. If you think you are just holding still, I garantee you that you are actually only learning bad habits that will be very hard to break. I say this as someone who has mastered hundreds of skills. I wish I could tell you that once I learn how to do something, I just clip it to my tool belt and it's always there if I need it, but this is not the case. When it comes to personal skill, there are only three options:
Use it
Lose it
or corrupt it.
If you are under the impression that you have a skill that the above options does not apply to, then you are actually in one of the second two and you don't know it yet. Of the two negative options, "Lose it" is the better because you don't have any bad habits, you're just not improving your skills in any way. " Corrupted" skills are the worst, and if you actually use your skill sets to earn a living, you learn to fear this above all else.
This method is a way to keep yourself on the cutting edge of improvement and to keep you on your toes whether you need bullets this precise or not. More importantly, if the day comes that you start getting fliers, ans bad groups, this will be something you can use to check yourself and get back on the horse quickly so that you can get back in the power seat and regain control of yourself.
This is good stuff here. I don't know of any method that is this powerful and simple for staying on the edge of perfection.
Precision in the wrong place is only a placebo.
I have been applying some of my new knowledge.
All bullets cast with COWW +2%sn, PID temp controlled, Mold temp monitored. All sprues were cut immediately at freeze (there was no more than 1 second of molten lead on sprue), drop bullets, count (designated) seconds, close mold, count (designated) seconds, run a free lead stream, re-fill mold.
These are my bell curves
Pot temp 695 deg. a count of 4 sec. after bullet drop to close the mold, a count of 6 sec. rest before re-fill. Bullet variation was 1.5 gr. I forgot to record mold temp. but it varied only 5 deg. Bullets had miner frosting. No wrinkles or worm tracks.
197.3 gr = 1 bullets
197.5gr = 3
197.7gr=3
197.8gr=11
198.0gr=19
198.1gr=17
198.3gr=13
198.5gr=14
198.6gr=4
198.8gr=2
second casting melt temp 695. A count of 6 sec. until mold was closed and a count of 8 sec. until re-fill, If I didn't hurry to cut the sprue I had to use additional force. Bullet variation was .8gr. Mold temp was about 15 deg. under first test. Bullets had no frost. Good fillout, no wrinkles.
196.1 gr = 1 bullets
196.3gr= 12
196.5gr=24
196.6gr=23
196.8gr=13
196.9gr=7
Tomorrow I will test at higher melt temp. Kevin
Last edited by kbstenberg; 03-11-2015 at 01:13 AM.
Why it's important and beneficial to me to be consistent in casting and weight sorting.
I've done this sort of test many times before and the results always come out the same; if I want the best and most consistent accuracy, especially at high RPM and high velocity cast consistently bullets of the same weight and dimensions is necessary.
I had some 30 XCBs cast of #2 alloy which was WQ'd. The BHN was 21 - 23. I had weight sorted them and had a batch that were 154.3 gr in weight. I decided to test the 1.5 gr weight variation that has been mention recently. That would be a +/- .75 gr from the 154.3 gr. Sorting through the lighter weight culls for the "-" side I found a 153.4 and a 153.8 in weight that did not have any visual defects. On the "+" side I found a 154.8 and a 155.1 w/o visual defect also. That gave 6 that weighed the same, 2 lighter and 2 heavier with the 1.5 gr variation. I loaded them over a standard load that runs right at 2900 fps out of my 30x60 XCB rifle; Dawn.
I shot the test this morning. There was hardly any wind and the temp was 60 with a 16% humidity. Target was at 100 yards. I had marked each of the lighter and heavier bullets and spread them throughout the 10 shot test string. I tracked each shot on target and the sequence in which fired. The 2 lighter bullets were #6 and #8. The 2 heavier bullets were #3 and #9. As we see the 2 lighter bullets gave the 2 highest velocities and really went out of group giving an overall group size of 3.3". The 2 heavy bullets also were a bit out but still stayed within a 2" group with the main group. The main group of all the same weight bullets (6) went into a tidy group of .85". That's at a muzzle velocity of 2892 fps!
This once again demonstrates the necessity of consistent cast and the need for weight sorting if we want the best accuracy we can get at high velocity or any velocity for that matter. It's why most cast bullet benchresters and target shooters weight sort also. On the other hand I suppose if I was just blastin" with an AR out to only 100 yards the 3.3" accuracy would be sufficient, or at least it is with several milsurp rifles I just use for blastin' or rock shooting.........however, I did not build Dawn to go "blastin" so being consistent in casting and weight sorting is important to me. The proof is in the shooting.
Larry Gibson
Attachment 133638
I have a couple thoughts on that.
First, RPM is RPM, centrifugal force is centrifugal force, and it will have a certain effect on a projectile over a certain amount of time. Since Larry is getting the bullet to the target faster (nearly 3000 FPS) he will observe less effect (this is pure unadulterated speculative postulation on my part) than the same bullets shot out of a ten twist rifle at 1900 FPS.
Second, most shooters would see those fliers, and write them off as a pulled shot, a called flier, "its just cast and you can't expect better", or what have you.
Most cast bullet shooters are less than critical of their bullets in the first place because they have it set in their minds that cast bullets equal sub standard equipment.
I would humbly submit the possibility that the only thing sub standard about our sport is the processes used to cast, load and shoot the bullets, thus the reason for this thread.
Fix the process, correct the obvious proven issues ("excellent" alloy cast with good process control, slow twist barrels, good repeatable lube, etc etc etc), and hold a higher standard.
Last edited by MBTcustom; 03-12-2015 at 12:00 PM.
Precision in the wrong place is only a placebo.
Well, that's how you get started making bullets.I was on the phone with a good friend tonight. He said something that cracked me up so bad I almost died. He said and I quote: "Just pour the hot stuff in the square thing!!!!"
I have discovered that consistant pour spout location over sprue plate hole is a must when pouring from bottom pour pots. I may fabricate a tray that will allow exact location of mould everytime a bullet is poured and use one cavity only...especially for precision rifle shooting.
Pouring all five cavities at a time is fine for busting rocks.
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