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Thread: Accuracy loss from ragged sprue cut?

  1. #1
    Boolit Master
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    Accuracy loss from ragged sprue cut?

    Has anyone done any tests on accuracy loss from ragged sprue cuts on plain base rifle bullets? I make sure any plain based rifle bullets I cast have perfect as possible bases, including a nice smooth, sprue cut. I have a bunch of what I think are commercial cast bullets (the label on the box is illegible )with a lot of ragged craters of varying depths where the sprue was cut off. I planned to just melt them, as they were in a flood and are covered with a light coating of dirt and grit. As I was washing them prior to throwing them in with some range scrap I was going to melt and clean, I started to wonder why a commercial casting outfit would let such sloppy bullets out the door, as they probably wouldn't be very accurate. Then I got to thinking that maybe my opinion that they wouldn't be very accurate might be wrong. There is no way I'm going to put any of these grit covered bullets down any of my barrels, so testing them is out.
    Does anyone here have any solid shooting data showing how varying depths of ragged sprue craters affect the accuracy of plain based rifle bullets?

  2. #2
    Boolit Master
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    There is a book 'The Bullets Flight' by F.W. Mann that covers bullet defects and how they affect accuracy. Written long ago covering cast bullets with thorough coverage of almost all bullet defects and their affects.

  3. #3
    Boolit Master Bad Ass Wallace's Avatar
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    Quote Originally Posted by quack1 View Post
    I make sure any plain based rifle bullets I cast have perfect as possible bases, including a nice smooth, sprue cut.
    Your thinking is correct. Every time that I pour I check the bases for flaws, either sprue torn out or base feathering under the sprue plate. I have not done specific accuracy testing but I do weigh my match boolits to +/- 0.1gns. A torn sprue can make the boolit weight vary by up to 2 gns. Only perfect[y cast boolits will give good 10 shot groups like this from a 30.06.

    Hold Still Varmint; while I plugs Yer!

  4. #4
    Boolit Grand Master popper's Avatar
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    Bad edges of the base have more effect than sprue divits. Sprue divits can be soft/porous alloy that smushes when fired. I tried actually cutting the sprue just as it gets solid, had more trouble with plate lifting and giving non-flat base. Accuracy suffered and almost (if I'd fired more rnds) got the 'circle (300BO @ 100 yds, 2k fps 145gr PB - ~2" circle). Deliberately dinged the edge of 40sw and got the 'circle' 5", @ 7 yds. So yes, base divits can cause inaccuracy but bad edges are much worse.
    Whatever!

  5. #5
    Boolit Master


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    BAW, can't argue with success like that. Whatever you're doing, keep on doing it.
    From my experience, a GC hides a lot of sins and base divots and they usually shoot better than do PB bullets with divots.
    Now, this is a discussion thread so I'm going to throw my $.02 and opinion in.
    I've shot a lot of handgun bullets with divots. Haven't noticed a loss in accuracy but my shooting is not precise enough to be able to tell.
    I've read of an experiment where the bases of PB bullets were filed perfectly flat for rifles with excellent results. I would say that the position of the divot has more to do with accuracy than the presence of it. Off center positions would surely cause some problems in balance during flight. How much? Who knows.
    Having been a member here for a long time, I've poured my share of lead and my bullets are "run of the mill" as the next guys.
    Now, here I'm gonna bust some bubbles. You guys pour bullets, inspect meticulously, size precisely and some even go to the extravagance of weighing and sorting. "My bullets are perfect" I'll hear.
    I say "hogwash".
    Somebody make this experiment as I don't have the time or assets right now.
    Cast 150 say .30 180 grain spire points like say the RCBS 30-180-SP. Inspect them and be very aggressive in finding faults. Out of this 150, select the best 100. These should be perfect. Weigh if you want but end up with 100.
    Take these 100 "perfect" bullets and tumble them in metal "jeweler's media or perhaps the new stainless steel media being used now (i'm a dinosaur) for two hours in a tumbler.
    After this inspect them again. I'd be willing to bet this process will expose sunken places or voids in 75% of your perfect bullets and this is only what you're seeing near the surface.
    They will be present in base, bands, ogive and lube grooves. Most of these you'd cull if you were aware of them.
    The bottom line is there ain't a perfect cast bullet. The "freezing" process of the lead sets up internal voids whether you like it or not.
    We even did multiple fluxes, cleaned the melt and let it set at casting temp for 2 hours and then cast and didn't return sprues and cull. Still the voids were there.
    Surely these voids affect bullet flight as much as a divoted base as most are off center.
    Cast the best you can and cull aggressively and do what works for you. There's ain't any thing such as a perfect cast bullet. Take them as is and enjoy shooting them. It is what it is./beagle
    diplomacy is being able to say, "nice doggie" until you find a big rock.....

  6. #6
    Boolit Buddy
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    I have a cpl loads,and 5 gang fixtures for squaring bases on a Bridgeport. And these are WITH gaschecks. It started when I was shortening a Lee 130g 7mm to use in a factory 11T Savage,7-08 barrel. Their eng. dept must've been on a heckuva binge that week? In anycase,they got shortened one dr band and turned "into" 100g. Shot very well. One thing was for sure,they were DANG SQUARE,and flat.

    Can't remember what other fixture I made,know there's two... too lazy to go look,probably a .22? Anyway,if you are wanting bugholes @JB starting velocity,it's just another small hurdle. The fixturing makes it very quick and easy. Good luck with your project.

  7. #7
    Boolit Master
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    This is what I would do. Remember just what I would do.
    I would select 15 bullets with near perfect bases, (nothing is ever perfect), and load them with my pet powder charge. Select 15 with the bad sprue cuts and load them the same.
    Go to the range and shoot 3 five shot groups or 1 fifteen shot group and see the difference.
    That way you will have done your own work and will have a determination based on what you have experienced based on your testing.
    That way you will have at least some solid reasons to believe the way you believe.
    Unless you are going into some competition where there is a grand prize that is remarkable it may not make any WORTHWHILE difference.
    Just playing and fiddling at the range, unless the accuracy is very poor you may find it isnt worth the time to sort the projectiles.
    We Know Mass Cannot Be Weighed But It Has Newtonian Weight And That Is Derived From Kilograms And Kilograms Can Be Converted to Pounds. But, Still Mass Cannot Be Weighed. But How is the kilograms obtained? Can Kilograms Be Weighed? Evidentally Yes It Can. But, Still Mass Cannot Be Weighed So Kilograms Must Not Exist. Funny Isn't It.
    One good thing out of this the next time I'm at the doctors and they want to weigh me I'll tell them mass cannot be weighed.

  8. #8
    Boolit Grand Master

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    Those may be "seconds" culled because of the ragged base and sold cheaper than the good ones .
    More than likely it's simply a slipshod operation run by someone with a casting machine in his garage to make cheap boolits to sell at gunshows ... sometimes they don't know any better and other times they don't care . Not every boolit maker runs a quality operation .

    I believe holes in the base affect accuracy ...based on nothing more than common sense .
    How much the accuracy is affected ...don't know . I make sure all my boolits are cast with perfect bases .
    Gary
    Certified Cajun
    Proud Member of The Basket of Deplorables

  9. #9
    Boolit Buddy tmanbuckhunter's Avatar
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    Bad bases do affect accuracy, but not as bad as one thinks. As someone stated above, good sharp edges on the driving bands and the base are the most important thing. My plain base boolits have to be perfect. Keep in mind, that when trying to cast bullets of a consistent weight, it's better to have perfect bases anyways. The difference between a divot and a perfect base is only a few extra seconds of sprue solidification time.

  10. #10
    Boolit Master
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    Could someone post a picture of a perfect base, I don't think I have ever seen one.

    Tim
    Words are weapons sharper than knives - INXS

    The pen is mightier than the sword - Edward Bulwer-Lytton

    The tongue is mightier than the blade - Euripides

  11. #11
    Boolit Master
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    Perfect is a loosely used term that most of us understands. Nothing is "PERFECT" on this earth. But some are nearer "PERFECT" than others so it becomes a relative term.
    Just like the term "FRIEND". How many uses the term "FRIEND" for someone that is just a buddy or acquaintance?
    One must understand relativity when using terms".
    "PERFECT" is one of those words or terms.
    We Know Mass Cannot Be Weighed But It Has Newtonian Weight And That Is Derived From Kilograms And Kilograms Can Be Converted to Pounds. But, Still Mass Cannot Be Weighed. But How is the kilograms obtained? Can Kilograms Be Weighed? Evidentally Yes It Can. But, Still Mass Cannot Be Weighed So Kilograms Must Not Exist. Funny Isn't It.
    One good thing out of this the next time I'm at the doctors and they want to weigh me I'll tell them mass cannot be weighed.

  12. #12
    Boolit Bub
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    Greetings,

    Another consideration is this...

    I cast softer alloys, 20:1, and the shearing of the sprue compresses the metal near the base. That is, it creates a slightly oval bullet base. This is easy to test using a good micrometer.

    I place an old pure cotton cloth, soaked with water, near the furnace. Prior to knocking off the sprue I turn the mould sprue side down and quench the sprue momentarily on the water soaked cloth.

    I do the above to harden the sprue so that when knocking it open less metal distortion occurs. Also, it keeps the sprue plate and top of the blocks from the dreaded "Lead smear".

    Most casters use alloys containing Antimony. There is a large window of "slush phase" when Lead-Antimony alloys cool. Most Lead-Tin alloys cool fairly quick and there is a smaller "slush phase". LinoType is excellent as it melts and hardens at the same temperature, eutectic, I believe.

    SAECO moulds have smaller holes in the sprue plates. These require less energy to shear away. Most of my old SAECO moulds cast nice bullets.

    Cheers,

    Dave

  13. #13
    Boolit Master


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    Quote Originally Posted by dtknowles View Post
    Could someone post a picture of a perfect base, I don't think I have ever seen one.

    Tim
    The only way you will ever get a perfect base is from a nose pour mold. I only have one nose pour rifle mold, and my other nose pour molds like shotgun slugs have base pins for a hollow base. I don't have any of those rifle bullets cast at the moment, so I can't post a picture of a perfect base. That bullet is a 45 caliber, likely for 45-70. I got it from my grandpa who used it for his 458 win mag pistol.

  14. #14
    Quote Originally Posted by megasupermagnum View Post
    The only way you will ever get a perfect base is from a nose pour mold. I only have one nose pour rifle mold, and my other nose pour molds like shotgun slugs have base pins for a hollow base. I don't have any of those rifle bullets cast at the moment, so I can't post a picture of a perfect base. That bullet is a 45 caliber, likely for 45-70. I got it from my grandpa who used it for his 458 win mag pistol.
    Well, only if the mold is right. I bought a well known nose pour mold, used, and it really casts nicely. but, I noticed the base seemed out of kilter. I am only familiar with this one and only nose pour mold, so I'm not speaking about others. Looking at the mold, the pivot end had a spacer between the top and bottom plates. I took it apart, miked the mold blocks, then the spacer, and they didn't match. So I chucked the spacer up and started gently shaving it so it matched the mold block. Reassembled it and it now casts much better.

    Then, I bought a mold from one of the better known makes of today. I was getting weird bases. As I was standing them to weight sort them, some were rocking. Sure enough, there were some bases that had a divit in it, and some that had a bump. I looked at the sprue plate, and the funnel cuts were not carried far enough to the bottom surface, leaving a dull cutting edge, one that had an obvious flat. So I deepened the funnel cuts to the point there was no "edge" visible, meaning it was sharp. I then stoned the bottom of the plate to make sure there were no burrs. It now cuts a very nice flat base.

    Still, I have ways of seating a gas check that is square the the bullet centerline, and they are crimped/sized the same way. A flat and square base is paramount to accuracy.

  15. #15
    Boolit Master
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    Quote Originally Posted by 44MAG#1 View Post
    Perfect is a loosely used term that most of us understands. Nothing is "PERFECT" on this earth. But some are nearer "PERFECT" than others so it becomes a relative term.
    Just like the term "FRIEND". How many uses the term "FRIEND" for someone that is just a buddy or acquaintance?
    One must understand relativity when using terms".
    "PERFECT" is one of those words or terms.
    I know by perfect we do not mean flawless but perfect for this application and while you think everyone knows what that looks like but I don't have a point of comparison. I have not seen a lot of pictures of good bases posted to the forum.

    Is this good, perfect, not bad or trash?

    Click image for larger version. 

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    Tim
    Words are weapons sharper than knives - INXS

    The pen is mightier than the sword - Edward Bulwer-Lytton

    The tongue is mightier than the blade - Euripides

  16. #16
    Boolit Master Win94ae's Avatar
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    Quote Originally Posted by dtknowles View Post
    I know by perfect we do not mean flawless but perfect for this application and while you think everyone knows what that looks like but I don't have a point of comparison. I have not seen a lot of pictures of good bases posted to the forum.

    Is this good, perfect, not bad or trash?

    Click image for larger version. 

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    Tim
    Mine are never that good, not even close; yet I get sub-moa still. In my opinion, it is a non-issue.
    Click image for larger version. 

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  17. #17
    Boolit Buddy

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    I’ve learned that imperfect bases are deadly when you seek perfect bases. Be content with the imperfections and be happy with the knowledge that perfect bases do exist.

    Stronger, Prouder and Greater!

  18. #18
    Boolit Buddy Driver man's Avatar
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    Quote Originally Posted by dtknowles View Post
    I know by perfect we do not mean flawless but perfect for this application and while you think everyone knows what that looks like but I don't have a point of comparison. I have not seen a lot of pictures of good bases posted to the forum.

    Is this good, perfect, not bad or trash?

    Click image for larger version. 

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    Tim
    looks off centre to me
    The Bird of Time has but a little way
    To fly-and Lo! the bird is on the wing

  19. #19
    Boolit Master
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    Again nothing is perfect. A lot of us are off center or off plumb.
    We Know Mass Cannot Be Weighed But It Has Newtonian Weight And That Is Derived From Kilograms And Kilograms Can Be Converted to Pounds. But, Still Mass Cannot Be Weighed. But How is the kilograms obtained? Can Kilograms Be Weighed? Evidentally Yes It Can. But, Still Mass Cannot Be Weighed So Kilograms Must Not Exist. Funny Isn't It.
    One good thing out of this the next time I'm at the doctors and they want to weigh me I'll tell them mass cannot be weighed.

  20. #20
    Boolit Master
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    Quote Originally Posted by Driver man View Post
    looks off centre to me
    I agree and it is slightly raised does that mean it is not perfect? Does that mean it is bad, reject? For me that one is a keeper.

    Tim
    Words are weapons sharper than knives - INXS

    The pen is mightier than the sword - Edward Bulwer-Lytton

    The tongue is mightier than the blade - Euripides

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check