Bullet base perfection.

[AJC1]

What is it about a bullet base that actually needs to be perfect, for good bullets. One could assume that a base perpendicular to the bearing surface is a must. One would also assume that the outer edge of the base should be perfect. Where does that leave things like tear out from a bad sprue cut.... obviously they have cup and hollow base designs so are those the two important things????

 

[Bearded Phil]

Flatness for consistency in both weight & case volume and roundness for proper bore seal and to prevent blow-by.

With the flatness of the base and even sprue cuts it probably only really matters for long range competition style cast shooting. Roundness is probably negated by obturation (if any) in regard to small dings and the like from coating, unless it's really out of round from bad fill out in the mould, that's a whole different situation.

 

[GeoDudeFlorida]

What is it about a bullet base that actually needs to be perfect, for good bullets. One could assume that a base perpendicular to the bearing surface is a must. One would also assume that the outer edge of the base should be perfect. Where does that leave things like tear out from a bad sprue cut.... obviously they have cup and hollow base designs so are those the two important things????

I think the specific alloy and burn temperature of the load will determine how much of an effect either will have on accuracy, leading and such. A low melt point alloy with a “hot” powder may, under the right conditions, leave deposits in the barrel. I think the difference is absolutely negligible under most conditions but I’m sure an experiment could be crafted to demonstrate the possibility.

 

[.38 Special]

I think the OP summed it up with the first two characteristics: a perpendicular base with clean edges. Everything else is far down the list, as long as there are no gross deformations.

 

[Litetrigger]

Short answer: The best - meaning moulds that produce the most accurate rifle bullets - have sprue cut at point of the bullet, not the base.

 

[dredd]

I read an article quite awhile back about the impact that nose vs base had on accuracy.

Long story short, the base is where it's at.

They deformed & damaged the bullets in various manners.

A damaged base upset the flight much more than a damaged nose.

 

[gwpercle]

If I'm going to stand over a hot pot and cast bullets I make sure all my "keepers" have perfect bases , completely filled out , sharp edges and no holes or divots in sprue locations .
The mould determines the perpendicular / squareness of base to the bore , not much you can do but use a good mould .
Don't allow any wrinkles or voids on the base ... if not perfectly filled out ... the wobble will set in and wobbles destry accuracy .
Short range handgun ammo will tolerate a few minor wrinkles on side and nose ... but the truth is . with some "learning" casting mostly defect free bullets isn't that hard ...
Heck ... if this old fool can do it ... any fool can !
Gary

 

[GeoDudeFlorida]

I read an article quite awhile back about the impact that nose vs base had on accuracy.

Long story short, the base is where it's at.

They deformed & damaged the bullets in various manners.

A damaged base upset the flight much more than a damaged nose.

So you’re saying… it’s all about that base, ‘bout that base…

 

[AJC1]

Short answer: The best - meaning moulds that produce the most accurate rifle bullets - have sprue cut at point of the bullet, not the base.

I've read about them, never seen one. Can't explain why they are not more common if that's true...

 

[dredd]

So you’re saying… it’s all about that base, ‘bout that base…

I am starting to understand why people want a DISLIKE Button!!!!!

I'm now loading up some Judas Priest to try to rinse that from my brain!!!

Bad!!! GeoDude Bad!!!!

 

[AJC1]

I am starting to understand why people want a DISLIKE Button!!!!!

I'm now loading up some Judas Priest to try to rinse that from my brain!!!

Bad!!! GeoDude Bad!!!!

In this case would a trebble button be more useful.

 

[GeoDudeFlorida]

In this case would a trebble button be more useful.

You’re just getting me into more treble now.

 

[dredd]

We're going to get this thread locked! LOL

 

[41 Mag]

So aside from tha treble we might get into if our bass ain't right...what I have found is the best bullets are square and flat based with no tear out from the sprue cut.

I shoot an awful lot of cast handgun bullet at longer ranges simple due to practice makes perfect. That said I'm hunting with these out to around 50yds. Not spectacular but nonetheless I want to know that a load groups tight at 75 - 100yds so I reduce the adrenaline factor at 50 or less. Those bullets with a divit or tear in the base are usually outliers in the group. They are used for practice purposes only. For hunting purposes I will scrutinize a poured batch in order to get the best weight and sized tolerance before loading.

For rifle, I've noticed that some tiny imperfections to the driving bands may or may not show influence, but I always toss those with something showing on the base or bottom band. The other thing I have found is when using a GC, if it isn't seated square, it ain't gonna shoot to group. This is usually the result of the exiting gas influencing the bullet as it leaves the barrel.

 

[AJC1]

So aside from tha treble we might get into if our bass ain't right...what I have found is the best bullets are square and flat based with no tear out from the sprue cut.

I shoot an awful lot of cast handgun bullet at longer ranges simple due to practice makes perfect. That said I'm hunting with these out to around 50yds. Not spectacular but nonetheless I want to know that a load groups tight at 75 - 100yds so I reduce the adrenaline factor at 50 or less. Those bullets with a divit or tear in the base are usually outliers in the group. They are used for practice purposes only. For hunting purposes I will scrutinize a poured batch in order to get the best weight and sized tolerance before loading.

For rifle, I've noticed that some tiny imperfections to the driving bands may or may not show influence, but I always toss those with something showing on the base or bottom band. The other thing I have found is when using a GC, if it isn't seated square, it ain't gonna shoot to group. This is usually the result of the exiting gas influencing the bullet as it leaves the barrel.

I have had and seen many sloppy gas check installations. I can't understand putting all that effort to fail there. I use a noe sizing die, but with guys traditional lubing, the height for grease I think plays a big role. Grease under the check causes problems.

 

[GeoDudeFlorida]

Those bullets with a divit or tear in the base are usually outliers in the group. They are used for practice purposes only.

Makes perfect sense. Centrifugal forces would be out of balance. When the center of spin is out of alignment with the center of gravity, accuracy is impacted.

 

[dartor]

What is it about a bullet base that actually needs to be perfect, for good bullets. One could assume that a base perpendicular to the bearing surface is a must. One would also assume that the outer edge of the base should be perfect. Where does that leave things like tear out from a bad sprue cut.... obviously they have cup and hollow base designs so are those the two important things????

Most of my bullet casting for handguns is done with Lee 6 cavity molds. I flip the mold over and cool the sprue on a damp rag for a couple seconds, edges are crisp and tears are minimized. I'll do this every third or fourth cast. I haven't tried it with rifle molds yet, but I will the next time I cast some.

 

[41 Mag]

I have had and seen many sloppy gas check installations. I can't understand putting all that effort to fail there.

So to that end, the biggest problem I have with GC's is fitting bullet bases. Regardless of size, the difference in alloy or temp, not to mention variations in molds, will inevitably have an influence on getting the check to fit over the bases.

NOE makes a tool to chamfer the edge of the base a bit, and one can anneal them as well. Still however, some are just a pain to get situated. For flat nosed bullets this isn't as big a deal as for the Spitzer or RN type rifle bullets.

Any flat nose and most large caliber HP can easily be seated into a check using a flat nose punch and a small piece of flat bar to cover the sizing die hole. With the Spitzer or RN type however some of the nose punches have just enough slop to allow a bit of offset when just seating to give a bit of cant to the GC. It pays to have a straight piece of something to check how they sit after seating the check.

 

[mdi]

I've always believed/read that a flat base with a clean edge leaves the muzzle straight, with gasses uniformly pushing the base. Crooked, defects in base edge results in an uneven push out of the muzzle, skewing bullet flight. Haven't given much thought about sprue cuts and aerodynamics.

Nose pour bullet molds were once more popular than today, for "pointy" and hollow base bullets, normally much better bases. Better accuracy (?)...
https://brooksmoulds.com/
https://www.midwayusa.com/product/1010190911