Home Forums Reloading Bullet Casting What is the minimum cast bullet diameter for consistent accuracy?

I'm sure some people who are meticulous and spend a lot of time working on their craft can get good, consistent accuracy with smaller diameter cast bullets than most others do, but I've read that there is a cast rifle bullet diameter threshold below which consistent accuracy is difficult to achieve. It seems like I read that minimum diameter threshold was somewhere around .30-caliber or maybe even .35-caliber (IIRC it was one of the gun writers from the '50s/'60s that made the statement), but I'm not able to find the reference. More important than the exact reference to me is an idea of where the threshold is currently for the average rifle bullet caster, not for the elite casters.

Ive had far better, and more consistent results with the 35 caliber and larger bullets sized and lubed to.001 over bore size, than smaller sizes, I have a few 30 cal molds and loads that work really well at low plinking velocities, but once you start exceeding about 1600fps accuracy gets rather inconsistent.
regardless of bore size , bullets sized to only bore diam. don,t tend to be as accurate, and gas check bullets with lots of lube grooves do tend to be more accurate on average
I generally cast 95% wheel weights ,5% pure tin , and cast hot enough to look slightly frosted and dropped into a 7 gallon bucket full of water from the mold


example the mold above is very accurate in my 358 win at 1500fps



not as accurate



very accurate, as long as sized and lubed correctly and not pushed past 1800fps

30 or larger seem to be easier to get them to shoot with more accuracy,that said I have been having fun with my 7x57.
I hope that when I start shooting my 25 caliber it goes well also.

I have had great accuracy with 40 cal cast bullets but as far as smaller than 30 or 35 cal goes then the 165gn 7mm bullet from my 7x57 at 2415fps that will shoot moa and in hunting mode is good out to 250 yds.




Von Gruff.

Mostly what I shoot in cast are 35 caliber and up, and I've yet to have accuracy issues. But as with everything casting, there are many factors that affect accuracy and generalizations can get you in trouble. I believe that most of the cast bullet bench rest records are held with 30 caliber rifles, but I could be wrong on that.

The other thing to watch out for in regards to cast bullets in rifles is the twist rate of the barrel. 1-14 and slower is very friendly to cast bullets, 1-12's usually not a problem, 1-10's are starting to put some serious strain on the bullets, and the under 10" twist rates are litterally working to tear the bullet apart. The other thing that works against cast bullets is too high of a muzzle velocity, or simply too big of a case for the velocity range cast is friendlies at 1800-2200 fps at the muzzle.

If I was looking for a purpose built cast bullet rifle I'd go with a 30 br. For factory rifles, the 30-30 is an excellent choice.

I supose it depends on what is meant by accuracy but in my 7x57 I run a 9 twist barrel and the 165 gn cast bullet at 2415fps over 39 gn ADI 2209 - H4350 and get a 250yd capable meat getter.


Just as an aside, it is also a softnose so get good expansion with 100% weight retention.


Von Gruff.

That is impressive VG.

IMO,

The threshold is more twist dependent than caliber, bullet length, lube also help, but smaller bores also have less margin for variances in casting/sizing.

30 caliber is an "easy" place to start and I'd rate 357/358's overall "best", but the most consistently accurate cast shooter I've used is a 1-16 twist 22 Hornet, even at 2,900 fps..

Any chance you would expand on your technique to achieve your soft-nose/hard-shank bullets?

You have mentioned these repeatedly and my interest is piqued.

I don't know what VG does, but there are two ways for certain without bumping or burning fingers:


1. Hard alloy (linotype) and soft alloy nose (pure lead).
Mould must be slightly over normal heat (above 750 F). Two pots, two pours to make the shank hard and nose soft enough to expand at the impact speed.

2. Same concept, but using an alloy with arsenic plus tin, antimony and lead in ratio to heat treat (like WW metal) and a non-treatable alloy (defunct of arsenic) for the nose. By having two alloys, the hard base will heat treat and the nose pour will not when water dropped from the mould or treated in an oven; the former is what my picture shows.

Rifle bullets at jacketed speed work best with tin-lead alloys or the best is silver/tin lead from dental impression filament and its crucibles, if you want the nose to be ductile.

The method takes a little time and as I tried the two pot method unsecessfully find it more accurate as well.
First I cast up a batch of bullets in 50/50 ww/Pb and cut a measured amount from the nose to give me a 65gn portion to put asside for later.I have a hardwood block with an apropriatly sized hole and place the bullet in and mark with a scribe so I can make the cut with a small set of bolt cutters.

The balance of the 50/50 bullets are for general plinking.
Then the lino pot is taken to tempreture and the mould heated again. A soaking wet towel is placed on a chair or other surface behind you so there is seperation between the wet and the pot. Having to turn arround keeps the seperation safety margin.
A nose is put into the mould using a fine set of needdle nose pliers to keep the finger from the heat.

The mould is placed in the pot for a count of 15. I played with different times and found this was enough time to bring the nose in them mould to just short of melt temp.
Fill the mould with lino and let the sprue start to set and return the mould to the pot for 25-30 sec or just until you see the sprue starts to silver off prior to melt temp. It will be liquid enough to allow pulldown of the sprue as it resets.

At this stage turn arround and cool the mould on the wet towel untill the sprue re-sets. This takes about another 25-30 secs.


This is what the two components look like seperated and together. They become a one piece unit in the melt and retain thier integrity through the 2400fps I send them into meat.

These were earlier ones that I cut with a fine hacksaw but find the small bolt cutters give a better cut and easier fit back into the mould.
Recover bullet with expansion from .275 on the nose to .577 with 100% weight retention.

Performance on animals has been spectacular to say the least, with these four falling to them from 143yds out to 185 for the last one.
[img]http://i667.photobucket.com/albums/vv39/VonGruff/Goats-Castsoftnose006.jpg[/img]

The best thing is that a straight lino bullet shoots to the same poi for practice etc. I run these over 39gn H4350 for 2415fps from my 7x57. Works for me.

Von Gruff.

Thank you very much for that tutorial Von Gruff. I may go home and give this a try tonight.

VG - how many rounds can you send down the barrel at 2400 fps with your 70/30 beeswax/vaseline lube before you have to clean out fouling? As someone who plays the homemade lube game, the 70/30 just seems to simple and easy.

Have put over 200 through it before cleaning it Selmer and using Ed's Red it comes up with a couple of patches. I do put a majority of a softer alloy (47/33/20 ww/Pb/lino) at 1900fps with Blue Dot and litho plate GC but a couple of hundred rounds still leaves a clean barrel. Generally run a few of the "training" rounds of straight lino at 2400fps before a hunt but get no leading and precious little powder fouling either.
Have run this lube at everything from 800fps in my 44 spc's through to 2500fps in 404 Jeffery and have had no issues. Fit of bullet first, velocity required and alloy second, GC material third and lube is at the end of the list is how I think in terms of tinkering with my combinations.

After a substantial number of shots I did test after my usual ER cleaning by leaving it overnight with Hoppes but there was nothing further to remove.

I see many who agonise over the lube with many fanciful ingredients and or costly shop brands, but I have not seen a need to stray from what has plainly worked for me for aver 20 years. I tried a few tubes of the 'storebought' at the start, untill I got onto the 70/30 mix. Some will play with the proportions depending on climate but it works for me at 70/30 year round.
Edit to add - when I was doing my load testing with the faster rounds there might be close to 100 down the barrel in a day's testing and the only time I had a leading problem was when I pushed velocity past the alloy's deformation boundaries.

Von Gruff.

Thanks VG. Now I have to buy beeswax and petroleum jelly too...aarrgh!!! I run mostly 50/50 COWW/Pb alloy, water-drop if I need it a little harder. I haven't tried the duplex alloy boolits yet, but it will be one more experiment to add into the mix. I will be hunting this fall with a .357 Max in a 15" TC Encore and 311299 boolits out of my .308. I'll be trying the duplex alloy in the .308 for sure, as I intend to run some expansion testing in water-logged magazines in a box.

I had a neighbour who was a beekeeper and I got a 25lb block so you can imagine how much shooting I will have to do to get through that lot.
I have 50/50 ww/Pb that I run to 1500fps in both my 7x57 and 404 Jeffery as plinkers and the the various 44 spcl's and 44mags I had at one stage. Good alloy for general low velocity use.

Von Gruff.

"...minimum cast bullet diameter for consistent accuracy?"

About 1 thou over groove diameter. ??

Yeah, I am wondering that myself

Lotta great info here tho