The proof is always in the shooting. The only issue I would have is if the base rounding isn't uniform. If it's more rounded on one side, it will throw as a flyer.
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The proof is always in the shooting. The only issue I would have is if the base rounding isn't uniform. If it's more rounded on one side, it will throw as a flyer.
I'm picky, round base boolits go back in the pot. I really don’t have any problem with round bases once everything is up to temp and my alloy is right. I usually just throw the first few castings back in the pot. After that everything is honkerdory. Like 44man said, casting is easy once you get a few basics down.
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Sam
What would be the difference in a round base and a bevel base? I know it is the mold design, I am talking shooting wise? Seems to me they are one and the same as far as gas cutting and flinging boolits willy nilly all over the target.
Last edited by oldtoolsniper; 07-21-2010 at 01:19 PM.
“Work hard! Millions on welfare depend on it!”
I'm FAR more concerned and picky with the bases on my boolits than I am the noses. A rounded base goes right back in the furnace. I don't even think twice about it--back it goes.
Why go through all of the work to clean your brass, deprime it, size it, prime it , measure your powder, etc etc only to put in a less than perfect boolit? And perfection IS something we, as boolit casters, have control over.
A rounded base boolit most likely will not be uniform at the base due to poor fill out. If it is rounded a little more on one side than the other, it causes a problem when the boolit leaves the barrel. The side with "more round" will have a pressure release on exit on that side compared to the "less rounded side causing the boolit to cant. It's the same difference as having a bad or damaged crown on the barrel. The boolit needs to have a uniform pressure release around the circumference of the base of the boolit on exit of the barrel for the best accuracy.
Hope this makes sense!!!!
If ever a time should come, when vain and aspiring men shall possess the highest seats in Government, our country will stand in need of its experienced patriots to prevent its ruin.
Samuel Adams
Sam
Perfect sense! Thanks!
“Work hard! Millions on welfare depend on it!”
Like I said, if the base is uniformly rounded, probably not an issue. If the base is more round on one side than the other, it will likely throw a flyer.Originally Posted by oldtoolsniper
Rounded bases used to get rejected because I sized and lubed with a Lyman 450. Sizing a rounded bullet in the Lyman was a PITA cause the rounded base acted as another lube groove. Now I use a STAR and rounded or flat, the STAR doesn't care!!! STAR's RULE!!
ALL of my cast bullets are used for plinking so I don't care if they shoot 1.5" groups at 50yds.
Elk Country
Quit looking at the cast boolits as you drop them from the mold! That is a waste of time and allows the mold to cool off too much. I cast steadily until the pot is more than half gone and then add ingots and look over the boolits while the pot melts again. Your boolits on the left may well be due to your messing around looking at things while the mold cools off.
Lots of good info hear.I use a rcbs bottom pour and don't completely cover the hole so it can vent and I drag an aransas stone across the top mold block face to get a little vent line under the sprue plate.I let the sprue be able to pivot on its own when turned sideways.I think loose is better than too tight.With a little tilt and barely touching the plate with the nozzle it heats the spueplate while the lead is flowing into the cavity and when you keep it there momentarily while lead starts to pour over the side it has plenty of time to draw and make a big sprue when you lower and level the mold.Sometimes you can see the sprue suck down before it hardens.Sometimes it doesn't.I don't think you have to cast at a fast heavy pour rate to make good boolits but the mold and plate makes perfect boolits when they are hot enough.Better to be a little hot than cold and its easier to me to keep a mold hot by using 1 mold.I got to try ladle casting,It seems like it is a lot easier to get perfect boolits.You can make a lot of boolits fast with a bottom pour but you have to cool the mold with fan or wet towel to keep a iron mold from getting too hot when using one mold.I can get a few hundred sharp base boolits within a few hours even with a single cavity.Actually they can be easier because the middle doesn't get too hot like a 2 cavity.I wish somebody would make a perfect boolit fillout article,book or something.When the boolits are filled out perfect with sharpe bases everything is great,anything else seems not good enough.
What Down South said.
Rounded bases are NEVER uniform, either on the same boolit or within a batch. They'll shoot cr@ppy compared to boolits that have square (sharp) base corners. Took me a long time (thick head) to figure this out. And, NO, they're not the same as a properly cast bevel base. Square corners shoot best, BBs shoot worse, rounded base corners shoot really bad.
Regards,
Stew
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I think 44 man has identified what I find to be true. By the time my lee 20 lb pot is 2/3 empty I am pouring the best bullets - less pressure slower pour rate and I get perfect bullets. melt and mold are at a good temp - I always hate to quit to restock the pot because everything is going so well.
Talking just aerodymanic here, fill out et al regardless, I read somewhere, here I believe, the slower the speed and particularly once you hit subsonic, the more bullet base starts to matter. I can see how a good sharp edge would make the difference the previous posters have mentioned.
Came across this the other day. Just thought I'd share. I wish he had a shadow photo of a rebated boat tail for comparison.
Edit: There's some really cool, geeky stuff at that site. My mind started going mushy after reading just some of it. I'm putting it on my to-read list. Will take a while.
source
A .308 Winchester (7.62 x 51 Nato) FMJ bullet traveling at approximately 2800 ft/s (850 m/s). Note the change in flow type from laminar to turbulent at the bullet´s cannelure.
A 9 mm Luger FMJ pistol bullet, moving slightly faster than the speed of sound
A cal. .32 ACP (7.65 mm Browning) pistol bullet, moving at a speed considerably below the speed of sound. Only turbulences (the wake) can be observed behind the bullet´s base.
Last edited by Dannix; 07-21-2010 at 11:40 PM.
It would be interesting to see a WFN at about 1700 fps.
I have always said the pressure wave at the nose will move tissue in a deer out of the way into a secondary wound channel that collapses if the boolit is too fast. Be nice to see the wave.
Wanted to watch where this went.
A lot of times, this is the reason for large diameter bullets shooting well. If you mold it poorly or load it and shave or reduce down, you can still end up with a fairly square base if the bullet sizes down enough with pressure on the base to square it up. Another reason that many older PB designs had wide rear drive bands so the C of B wasn't disturbed enough to affect flight at common handgun ranges.
On the other hand, you can have a perfect bullet base and end up with poor muzzle fit for a multitude of reasons. That's the war the GC fights.
Easy to see. Just load case with no powder and let the primer run it up the barrel sizer far enough that it engraves. Then drive it back out and look close. Coarse this doesn't cover the pressure damage or repair aspect, but it will show you why the big bullet technique can tend to do better and why sometimes rounded bases shoot better than one would expect. (short range anyway) And thus why you have varied opinion yet again.
Old timers used to say that the base was the steering wheel of the bullet. But since it can be damaged so that a great sharp base isn't, I just say it's all in the launch.
Reading can provide limited education because only shooting provides YOUR answers as you tie everything together for THAT gun. The better the gun, the less you have to know / do & the more flexibility you have to achieve success.
No matter how hard I try, I'm failing to understand this. Could you elaborate a bit?
It is not the inflight shape that is the issue with a rounded base, it is the
non-uniform release from the muzzle crown. If one side opens up just a hair
before the other, you get a tip.
Bill
If it was easy, anybody could do it.
In this really good book I borrowed and read. (yes I learnt to read.)
the gentleman doing the testing could deform a portion of the base of a boolit and make it repeatedly hit a different spot (boolit lined up the same way in the barrel each time) from the normal group that was fired with the non deformed bases.
So yes, uniform bases are important.
Something I was thinking about just recently about the aerodynamics aspect -- gas checks aren't sharp-edged, so that may be a reason to not use a GC for slow stuff (besides unnecessary time and money expenditure). We could be talking about utter trivialities here though.
Bill, iirc, that's why some long range guys use rebated boat tail instead of 'standard' boat tail. Apparently the sharp edge of the rebated part makes for a more sure uniform release.
Wow, I'm get stoked just think of such a demonstration of geekiness. What's the book title?
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| 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 |
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