cast bullet size for rifles?

[Shadow9mm]

So for revolvers I understand you want to be right at or .001 over throat diameter to get a good seal and prevent gas cutting.

And in general for cast bullets you want to be .001 over the groove diameter to ensure a good seal.

I have a Henry 44mag/spl rifle. Henry stated the groove diameter was .430, and I just slugged it, and it came out to exactly .430.

My sizer is a .430. However the pressures I have been shooting are low, in the 13k to 14k PSI range. I am powder coating and then sizing. trying to achieve a sub sonic hunting load with 44spl's for my son. Hunting deer here in Indiana and a long shot is 100yds.

However I have been having troubles with bullets going into the target yawing at 25yds and sideways at 50yds.

my alloy is around 13bhn, recycled bullets that were sized wrong by the maker. (they replaced the batch for free )

I am wondering if my pressures were too low to cause the bullet to obturate into the grooves to seal properly.

my friends loads with the same bullets, sized the same, shoot great, but he is in the 17k to 20k pressure range. and I am wondering if the extra pressure is making them widen out and seal properly.

but back to my main question. I need to buy a new bullet sizer. do I go .431, or .432? or buy both and as the years progress and the bore wears I can go up to .432 later

and do you think going up .001 will solve my instability problems, or is there something else at work?

[waco]

Try different sized bullets. The largest one your rifle will chamber will likely shoot the best. My Marlin 1894 .44Mag prefers .433" bullets.

[BK7saum]

What is the twist rate and how heavy and long are your bullets? This may be more of a stability issue than a bullet size issue. If you are trying to run 310 grain bullets at 950 fps, the twist rate may be too slow. Just asking for a bit more information. What exactly is your load and have you ran it over a chrono?

[BK7saum]

Per a 2018 post I saw that the twist on some models was 1 in 38" If yours is an older rifle, then i think you don't have a fast enough twist to run the bullets slow.

I know there were reportzs that marlins sometimes had trouble running 265s unless pushed really hard.

[Shadow9mm]

What is the twist rate and how heavy and long are your bullets? This may be more of a stability issue than a bullet size issue. If you are trying to run 310 grain bullets at 950 fps, the twist rate may be too slow. Just asking for a bit more information. What exactly is your load and have you ran it over a chrono?

Bullets are over stable if anything based on bergers bullet stability calculator.

Per Henry its a 1:20 twist, I also checked when cleaning and my rod makes 1 full revolution when going through the 20in barrel.

I have 2 bullets and 2 loads that were both yawing and key holing.

first is a 200g lee round flat plain base at .600 long. traveling at 1322fps with 6 shots over the chrono

2nd is a 284g(with gas check) NOE wide flat nose. long nose designed for 44spl cases, too long for magnum cases. .785 long, going at 1055fps with 6 shots over the chrono

[Winger Ed.]

For the cals. I load, I think the Lyman book data uses sizers .001 over bore dia. in all their rifle data.

Something that's quick and easy to try without buying a new die:

Size a few, then powder coat.
It'll trick the barrel into thing the boolit is bigger.

The boolits might also just be too slow.
I don't know what the pressures would be,
but I'd get the boolits up at least to Black Powder speeds in the lower-ish 'teens.

[GregLaROCHE]

When I was helping a friend develop a subsonic load for .308 cal, before we could get subsonic, the boolits would always keyhole and not be accurate. We tried all different weights of boolits, but finally decided it must have been due to the twist rate.
Try to recover some fired boolits by shooting then into something so they don’t get deformed. I always thought a swimming pool would work great. Measure and look at them and you may get some clues.

[dale2242]

I size most of my cast bullets .001 over bore diameter with good sucess.
Some I size to bore diameter.
My granddaughters 7MM-08 loves 145gr. bullets sized to bore diameter.
I cast my rifle bullets with 50/50 alloy of WW/Lino.
22 calibers are cast of pure lino.

[sharps4590]

As with others I believe your size is too small. With smokeless and hard bullets, obturation shouldn't necessarily be counted on.

Secondly, with your heavy bullet load I don't believe you're driving it fast enough to stabilize.

[Nobade]

As mentioned above, a bullet that is a slip fit in a fired case is usually the best. In the case of my Marlin that is .433". Another thing is what does the throat look like in that rifle? If it's got the long tapered throat like Marlins and others, light loads let most of the gas blow past before the bullet gets to the rifling and seals the bore, torching material off the side and ruining accuracy. The solution is #1 - bigger bullets. #2 - longer cartridge length. Sometimes so long a loaded round can't be ejected. #3 - inert filler of some sort to act as a gas seal. All are a pain in the butt but I've done plenty of that to get 44 mag rifles to shoot. Then again, some of them work like they're supposed to. You just have to look at what you have and give it what it needs.

[reddog81]

Try sizing at .430 and then powder coating. The bullets should come out .431ish.

[Shadow9mm]

Try sizing at .430 and then powder coating. The bullets should come out .431ish.

Going to coat a few tomorrow, see exactly how much width I am adding. But I would prefer to coat then size as I feel it will be more consistent.

[mehavey]

Coat then size (432 suggested) -- you got it.
What's the fastest powder you have available/using ?

[10x]

I have discovered that if the seated bullet is larger than the bore diameter accuracy usually improves. I size my bullets so the case neck fits without sticking. this means I also thin the necks of my cases so they are standard.
My L46 Husqvarna in 9.3x57 loves a 0.368" cast bullet. Recommended bore diameter on this caliber is 0.366". a 0.369" bullet (in a very thin case neck) will chamber easily and shoot very accurately in one of my L46s, in the other it is tight because neck diameter with that size bullet is too large. I currently size my bullets to 0.367" so I never run the risk of the neck being squeezed by the chamber and raising pressures.
Somewhere in a book on casting I read that the best swage to size a bullet diameter to bore diameter is the throat of the rifle barrel . I have found this to be true of most rifles.
When I match cast bullet diameter to bore diameter groups get slightly larger. When I go 0.001" or 0.002" or more over bore diameter usually groups shrink.
BTW, i have gone to powder coat, and size after powder coating.
Recovered bullets (Gas Check) show that the powder coat does not come off and sticks well - even on expanded bullets.

I discovered sizing to max neck size with 303 british rifles - some of these had a 0.314" bore, some a 0.313" - the downside was that I had to keep batches of loaded bullets segregated by neck size for each rifle. All of these rifles shot well when I sized to the maximum neck diameter the chamber would accept
With cast bullets, your mileage will vary with different guns within the same caliber.

I want to ream the neck of the 9.3x57 chamber so that it will fit a 0.368" cast bullet - currently a 0.367" chambers nicely, a 0.368" is "sticky" .

My 9.3 (M98 mauser) in 9.3x62 will easily chamber any cast bullet and may even chamber 0.375" bullets. that is the largest neck I have ever had on any rifle compared to bore diameter. The larger the diameter of the bullet, the smaller the group. I powder coat, add gas check, and size the gas check on to seat it without sizing the bullet. Then shoot as cast. 1.5" to 3" groups are normal at 100 yards with a 0.369" as cast powder coated bullet

[reddog81]

Going to coat a few tomorrow, see exactly how much width I am adding. But I would prefer to coat then size as I feel it will be more consistent.

Test some out and see what happens. The difference in consistency will be negligible. Currently bullets are hitting the target sideways at 50 yards. It’ll be hard to do worse than that.

[mnewcomb59]

I would guess that the only reason your groove size bullets are tumbling is because you don't have a large expander for your cases. If the case is .426 inside diameter, and you stretch that thick magnum brass out to .430 using your softish bullet, then your base driving band is likely getting sized down.

[Shadow9mm]

Well, that did not go as planned. I sized to .430 and then coated a small batch for testing. Results, bullets came out at .432 to .433........ And I cant put gas checks on now cause they will go back to .430.... so major fail....

I ordered a .431 and .432 sizer for my press. Gonna have to wait until it gets here to get going. Hoping .431 will get the job done, but wanted a .432 just in case.

[Shadow9mm]

I would guess that the only reason your groove size bullets are tumbling is because you don't have a large expander for your cases. If the case is .426 inside diameter, and you stretch that thick magnum brass out to .430 using your softish bullet, then your base driving band is likely getting sized down.

I have some of the NOE expanders for other calibers, had a few issues with them, generally found that just flaring worked as well and was easier to set up. I will order a set for my 44 and see how it does.

I grabbed a piece of fired brass, my .430 sized bullets do not want to go into it. Not sure if the brass will fit after being sized up, similar issue to what I had with my other cartridges, but they were going in a tighter revolver cylinder.

[Shadow9mm]

So I got a micrometer in today. Had been using my calipers, figured relative size would be ok. measured my slugged bullet. to my surprise, it came in at .4312. so my measurements with my calipers were off a bit. I have a .432 sizer on the way, will powder coat, size and see where I come out at.

[mehavey]

Powder Coat, size to .432, use a fast powder.
No problemmo....