Accuracy loss from ragged sprue cut?

[quack1]

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?

[MostlyLeverGuns]

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.

[Bad Ass Wallace]

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.

https://i.imgur.com/SabiU6D.jpg

[popper]

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.

[beagle]

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

[Shopdog]

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.

[44MAG#1]

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.

[gwpercle]

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

[tmanbuckhunter]

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.

[dtknowles]

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

Tim

[44MAG#1]

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.

[fc60]

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

[megasupermagnum]

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.

[B R Shooter]

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.

[dtknowles]

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?

282881

Tim

[Win94ae]

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?

282881

Tim

Mine are never that good, not even close; yet I get sub-moa still. In my opinion, it is a non-issue.
282882282883

[WheelgunConvert]

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.

:bigsmyl2:

[Driver man]

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?

282881

Tim

looks off centre to me

[44MAG#1]

Again nothing is perfect. A lot of us are off center or off plumb.

[dtknowles]

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

[Beaverhunter2]

+1 DT. For me that boolit would be on its way to the range or the hunting blind.

[35remington]

I have shot the Ranch Dog 190 with substantial base divots from a friend cutting the sprue too soon. After GC’s were applied and shot through a particularly accurate Ruger 350 mag at 1400-1600 fps these shot just as well as the bullets without sprue divots....and the divots present were quite substantial. Being centered more or less probably helped.

Under 3X magnification I find no visually perfect cast bullets. Everything has something like a band which does not have perfectly sharp edges or something to that effect.

One of the most common things cast bullet shooters do is talk about the occasional exceptional group and ignore statistical representations of how their guns actually do shoot.

Post five, five shot groups on the same piece of paper or something statistically representative of that sort and then let’s talk about how your rifle or pistol shoots. Posting the occasional bragging group always leaves doubt.

[44MAG#1]

At last someone that has both feet firmly planted on the ground. Handgun shooters are some of the worst when it comes to talking about their ability. As I have said before on this forum most handgun shooters are poor to mediocre shooters. Only rarely will one see someone who can cash the check their mouth writes. Seen it too many times. Rifle shooters are a somewhat different story since most stay on sandbagged rests. Of course some handgun shooters do the same. It is what YOU can do over a PERIOD OF TIME that determines how good you are. Even I have had extremely lucky days but it in no way defines how good I am. Neither do the extremely unlucky days.
Oh well.



I have shot the Ranch Dog 190 with substantial base divots from a friend cutting the sprue too soon. After GC’s were applied and shot through a particularly accurate Ruger 350 mag at 1400-1600 fps these shot just as well as the bullets without sprue divots....and the divots present were quite substantial. Being centered more or less probably helped.

Under 3X magnification I find no visually perfect cast bullets. Everything has something like a band which does not have perfectly sharp edges or something to that effect.

One of the most common things cast bullet shooters do is talk about the occasional exceptional group and ignore statistical representations of how their guns actually do shoot.

Post five, five shot groups on the same piece of paper or something statistically representative of that sort and then let’s talk about how your rifle or pistol shoots. Posting the occasional bragging group always leaves doubt.

[B R Shooter]

I have shot the Ranch Dog 190 with substantial base divots from a friend cutting the sprue too soon. After GC’s were applied and shot through a particularly accurate Ruger 350 mag at 1400-1600 fps these shot just as well as the bullets without sprue divots....and the divots present were quite substantial. Being centered more or less probably helped.

Under 3X magnification I find no visually perfect cast bullets. Everything has something like a band which does not have perfectly sharp edges or something to that effect.

One of the most common things cast bullet shooters do is talk about the occasional exceptional group and ignore statistical representations of how their guns actually do shoot.

Post five, five shot groups on the same piece of paper or something statistically representative of that sort and then let’s talk about how your rifle or pistol shoots. Posting the occasional bragging group always leaves doubt.

I will agree, there is no such thing as a perfect cast bullet, especially in numbers, and it goes deeper than visual inspection. I think the base has more effect on rifle accuracy. A gas check gives the opportunity to normalize the base to a degree. I reject a bullet that shows a divot in the base, or a hump. But the edges can vary a bit. A gas check has a rounded "corner" where it was formed and you can seat a gas check squarely if done properly.

A rifle/bullet/load must prove itself for consistency. That's why I like shooting CBA matches where you shoot 4 targets each at 200 and 100 yards. That will show how consistent your gun combo is.

[dtknowles]

At last someone that has both feet firmly planted on the ground. Handgun shooters are some of the worst when it comes to talking about their ability. As I have said before on this forum most handgun shooters are poor to mediocre shooters. Only rarely will one see someone who can cash the check their mouth writes. Seen it too many times. Rifle shooters are a somewhat different story since most stay on sandbagged rests. Of course some handgun shooters do the same. It is what YOU can do over a PERIOD OF TIME that determines how good you are. Even I have had extremely lucky days but it in no way defines how good I am. Neither do the extremely unlucky days.
Oh well.

I judge my shooting by my worst groups using my best ammo. Ammo is only as good as its worse rounds. To claim a gun shoots under 1MOA groups over 1MOA need to be rare and explainable by some cause other than the gun.

[44MAG#1]

"I judge my shooting by my worst groups using my best ammo. Ammo is only as good as its worse rounds. To claim a gun shoots under 1MOA groups over 1MOA need to be rare and explainable by some cause other than the gun."

Mr. dtknowles,
You lost me in that one. Please explain. I am getting old.

[dondiego]

He said that he judges his ammo by its worst groups and if you claim to get 1 MOA, then you need to do that more often than you don't!

[44MAG#1]

He said that he judges his ammo by its worst groups and if you claim to get 1 MOA, then you need to do that more often than you don't!

Wasn't that what I meant by, "Only rarely will one see someone who can cash the check their mouth writes."?

[45-70 Chevroner]

Mine are never that good, not even close; yet I get sub-moa still. In my opinion, it is a non-issue.
282882282883

I have burned up a lot of powder behind boolits that look just like the one pictured and one's with divots, I can't see any difference and I am a lot better than average shot. My shooting when I was in the Airforce, was Expert Marksman.

[dtknowles]

"I judge my shooting by my worst groups using my best ammo. Ammo is only as good as its worse rounds. To claim a gun shoots under 1MOA groups over 1MOA need to be rare and explainable by some cause other than the gun."

Mr. dtknowles,
You lost me in that one. Please explain. I am getting old.

Say I have worked up a new load. If I go shoot 5 ea. 5 shot groups at one hundred yards and the groups are 1.12", 0.78", 0.92", 0.85", and 1.07" I would claim that gun and load shoot a little over 1 MOA not is shoots under 1 MOA. Yeah, sometimes is shoots under 1 MOA but not always. A gun/load is only as good as its worst group in idea conditions.

Tim

[dtknowles]

Wasn't that what I meant by, "Only rarely will one see someone who can cash the check their mouth writes."?

If you practice what I preach you can cash that check almost every time.

Tim

[dtknowles]

No doubt but were you shooting a gun that could notice the difference. Also the distance to the target matters. At longer ranges small differences in bullet weight make a bigger difference. At 100 yards a divot might make a couple tenths of an inch difference in group size in a gun that can shoot groups under 1 MOA. Few people own a gun that can shoot plain base cast bullets with enough precision to notice the difference a divot on the base might make. Even fewer people shoot enough of those small groups that they could tell if the difference was the divot on the base of the bullet or just the conditions that day.

Tim

[dtknowles]

He said that he judges his ammo by its worst groups and if you claim to get 1 MOA, then you need to do that more often than you don't!

Not just more often, if it was 50/50 half over and half under 1 MOA it is not a 1 MOA gun/load. While I don't hold to a 3 sigma standard I would think it should be twice as many are under as are over. Two thirds/one third.

Tim

[Bigslug]

I don't think I retained the hard data, but I recall the experiment.

When casting up some NOE / Lyman 299 gas check clones for my .303's, I had a good handful of them on which the sprue plate climbed away from the base of the bullet on cutting, leaving a small "stem" that was visible even after the gas check had been installed.

Since I was accuracy testing anyway, I separated those out to shoot a segregated group with, with no change in the load other than the not-smooth base - the logic being that if it didn't matter, rate of production could increase without loss of performance.

Unfortunately, as it turned out, it matters - significantly at only 100 yards - and good lab technique is still required.

[megasupermagnum]

Here's the thing with chasing accuracy. EVERYTHING matters. It just differs to what degree, and if you care. In the case of a sprue cut, just do the best you can. As I said, the only "perfect" base you will ever see is from a nose pour mold. Base pour molds do a dang fine job too. If you are chasing accuracy, cast the best you can, then sort the best ones you can get out of those. When working up loads, I'll often cast 300-400 of the best bullets I can, and maybe only keep 50-100 of the best of those for testing.

[44MAG#1]

This why posts such as this one is difficult to really hash out.
The thread title is "Accuracy loss from ragged sprue cut".
What degree of "accuracy"? What type of "loss"?
If one is going to compete in a "Big Time Match" the accuracy requirement may be different from someone deer hunting at 100 yards etc. etc. etc.. "Loss", how much is a "loss"? There is insignificant "loss" and major "loss". Is an insignificant loss a real "loss" or not? Will that "insignificant" loss be something that would cause "major" problems? Where will it cause the most problems, in the persons mind or in the actual shooting?
Can one tell the difference if they are not on a benchrest using top tier bench shooting technique? Again, where will that loss make the most difference? In the mind or in real world?
Perfect versus imperfect? Since nothing is perfect let's disregard that term to begin with. We have near perfect to severe imperfect. Where between the two are we talking about? If near perfect is a 10 and severe imperfect is a 1, where are we being impacted on that scale? That would be determined by the person being impacted. Some would swoon and turn pale with major fits of anxiety if they had some bullets with a very, very, very, very small tear, divot, or rough place on the base while others wouldn't be bothered if it looked like a major sinkhole that could be used as a bowl for their ice cream.
What level are we talking about from 1-10? That makes a difference as to what level we are talking about. Is the bullet base imperfect or is it I M P E R F E C T?
Just something to keep in mind.

[megasupermagnum]

Load 30 bullets straight off the casting bench, then load 30 bullets that you have sorted to as best as you can create. There is a difference, and it is often quite dramatic. People talk about tenths of an inch at 100 yards. I've seen bullet imperfections make inches differences. In handguns, I've seen sorted vs unsorted bullets double group size at only 50 yards. Which of the imperfections caused the worst issue, I can't say.

Bullet weight matters, fully filled out drive bands matter, bullet bases matter, cases matter, powder weight matters, primers matter.

Take a very accurate target rifle, but load it with random head stamp brass (no annealing, and fully size without regard to headspace), with a mix of "dads old primers", with sloppily thrown powder charges, and with bullets you did not inspect at all. I'll show you a rifle that might not even hit paper.

[44MAG#1]

Can you tell which degree of imperfection caused the terrible accuracy? Was it just one type of imperfection or was it a conglomerate of imperfections?
If it was a conglomerate of imperfections would the accuracy be less affected if it were only one imperfection?
What if it was only very minor ragged sprue cut versus a minor sprue plus a minor lack of a drive band filled out along with a bullet maybe sized out of alignment (I have seen that happen many times by over zealous casters just jamming them into the sizer to hurry up) ?
What about a base that had an imperceptible slight rounding of a small spot on the edge?
What about a middle band not fully filled out while the front band and base band are filled out?
Is any one of this things slight in nature enough to cause great concern or a few slight ones that added up make a major concern the problem? What about a larger single example of a malformation only by itself?



Load 30 bullets straight off the casting bench, then load 30 bullets that you have sorted to as best as you can create. There is a difference, and it is often quite dramatic. People talk about tenths of an inch at 100 yards. I've seen bullet imperfections make inches differences. In handguns, I've seen sorted vs unsorted bullets double group size at only 50 yards. Which of the imperfections caused the worst issue, I can't say.

Bullet weight matters, fully filled out drive bands matter, bullet bases matter, cases matter, powder weight matters, primers matter.

Take a very accurate target rifle, but load it with random head stamp brass (no annealing, and fully size without regard to headspace), with a mix of "dads old primers", with sloppily thrown powder charges, and with bullets you did not inspect at all. I'll show you a rifle that might not even hit paper.

[megasupermagnum]

Can you tell which degree of imperfection caused the terrible accuracy? Was it just one type of imperfection or was it a conglomerate of imperfections?
If it was a conglomerate of imperfections would the accuracy be less affected if it were only one imperfection?
What if it was only very minor ragged sprue cut versus a minor sprue plus a minor lack of a drive band filled out along with a bullet maybe sized out of alignment (I have seen that happen many times by over zealous casters just jamming them into the sizer to hurry up) ?
What about a base that had an imperceptible slight rounding of a small spot on the edge?
What about a middle band not fully filled out while the front band and base band are filled out?
Is any one of this things slight in nature enough to cause great concern or a few slight ones that added up make a major concern the problem? What about a larger single example of a malformation only by itself?

As far as I can tell, the answer to all your questions is yes.