How many thousands of an inch larger than bore diameter can hardcast bullets be ? I generally aim for about .002 over, but my last batch is almost .005 over. Im casting for a new rife, BLR in 450 marlin. Havent slugged the bore yet but expect it to be .458. In my 45/70s I always shot .460 , but this latest batch is .463 on average. Are these to big?? They are powder coated. Mold is a Lyman 457163

You mean bigger than the lands right, not the bore ?

Yes

For starters - size your bullets to what you want them to be, rather than just depending on mold diameter; it's best to have them all start at the same diameter rather than varying a bit in as-cast size. Sizing irons out irregularities in the powder coating as well.

As for how big they can be - that depends on your chamber. In some, .005" over is fine. In a lot of guns though, that will be too big for a loaded cartridge to fit in the chamber. Forcing it in anyway will drive up pressures and can be the difference between a safe load and dangerous pressure. A simplified way to determine that is check your fired cases from that gun; if your cast bullets won't fit in the fired cases easily by hand, they are too big.

The best possible scenario is to size as close to the throat that will chamber/function and not really consider groove diameter of the barrel.

Yondering is correct; the bullet should still drop in a fired case. The case needs to expand to release the bullet.
That shouldn't necessarily be confused with fitting the throat or snug chambering.

So long as they fall into a fired case, make them fit the throat.

You can, for about $25, get a die and bottom plug for any diameter you need. Lee will make you one if not a std. diameter.It will screw into your standard single stage press and the bottom plug will slip into where your shell holder goes.

https://leeprecision.com/bullet-casting/bullet-sizing-kit/

You also might need a new expander plug for you dies.

Absolutely. Sizing larger than groove diameter is a "by guess and by golly" approach. Measure the throat diameter and size .0005"-.001" under that. Measuring throat diameter is as easy as measuring bore/groove diameter.

When you say "hard cast" what exactly do you mean? Are you measuring hardness with a tester? For a big old .45 rifle bullet used in .45-70 and such, a bullet doesn't have to be hard. In fact, better accuracy and performance can likely be had with soft bullets in the 9-12 bhn range- without leading or resorting to powder coating either.

if you can chamber a loaded round you should be good to go.

if you can't, it's too big.

yukon254: You must be new to the rodeo? Slug the bore and then load three rounds each(with same load), bore size--- + 1---+2 and then +3 over. Total of 12 rounds. Fire them and see what you get. blammer: a case could be loaded with a bullet 20/1000" under and it would chamber but I don' think it would be "GOOD TO GO"

Okaaaay....

Again, size to fit the throat.

I cast quite a bit, but I would quit tomorrow if sizing .001 an inch at a time made or broke the process for every gun, for every bullet.

Make a seal from case mouth to muzzle and go from there.

Bingo! I quit measuring my bore a long time ago and just size them to slip into a once fired case neck.

Thanks, Dinny

I tried that today with some 38-55.The lands slug at .380. A .379 bullet will not slip in to case after firing They chamber easy after loading and shoot well at 50 yards at least. 4 inside of 2 inches and two fliers that were me. These were 250 gr cast with 13.5 gr of 2400. Max is 18 grs so I am far below max. I had some.375 loads that will slip in to the case after firing. 5 rounds keyholed at 50 yards and only a couple caught on both sides of 2' x 2' piece of card board.A lot of these old 38-55 have a .380 bore.

I have some.381's on order.

I am open to suggestions.

Alloy and hardness?

Don't have the alloy .They are Missouri Bullets, Powder coated. Brinell 18

The.375 diameter are Western Bullet.Lyman 375296
The.376 are Hunters Supply bullet

Back to basics. Determine throat diameter and size to .001 under or less. Ignore groove diameter. That alloy is way harder than you need for those velocities too.

I don't know if you do much shopping for 38-55 bullets, but there isn't a whole lot of them on the market. I don't cast. Newer 38-55 have .376 diameter. which says the .375, or .376 should work in a newer barrel but older ,38-55 barrels vary on the.379- .380 diameter and most likely their throats vary too.

I am trying to come up with a match for this 1906 Winchester without spending $600 or so for a reline or new barrel.

These bullets I have are marked Ballard.I guess there may be different specs when the Ballards came out, but all the brass is the same

Again, back to basics can be done without being a caster. First you gotta determine throat diameter, even if you adopt the approach by which a bullet just barely fits in a fired case (which will approximate it but still leave you at the mercy of the brass thickness). Armed with that knowledge you can buy bullets larger than that and acquire a simple Lee bullet sizing die (screws into your loading press) and size them to your required diameter. I have no way of knowing if by chance said diameter die exists in their lineup. Your job to play detective there. If the exact diameter die doesn't exist get the one closest and have it reamed/honed to size, or do it yourself- the woods are full of guys who do that themselves. Bottom line is it's easy and cheap.

I can't help but think also those hard-ish bullets you're using can be contributing to your issues. The harder a bullet is the less elasticity it has and the more it resists " bumping up" to seal the bore right from the git-go courtesy of the powder's "explosion". I realize now you're totally at the mercy of commercial casters- wish I had known that- some detective work on your part may turn up a source for something softer. Perhaps even a local caster can accommodate you if you provide a mould and some lead. (A whole lot cheaper than spending $600 on barrel work.)

Soft versus hard is an area that is often counter intuitive to non-veteran cast bullet guys. Often a hard bullet will give more leading and less accuracy than a soft one will. But people insist on hard because that doesn't make sense to them and the commercial caster guys are in the game to make money so that's what they provide.

That sums it up succinctly.

Thanks for the info.I sure appreciate it..I went thru a similar deal with an old 38-40 and made my own sizer out of a 7/8ths hardware grade bolt. Then lubed with a cooking cutter type deal. These.379 bullets, I can force push them into a fired case if I start them and then push them against the side of the bench. So I am thinking the fired case is just about .001 smaller.

Lee will make you a sizing die for any diameter you want for about $30. I already checked in to that.

I figure I have these .381 bullets coming and I can size them down if necessary with one of the Lee sizers. Worse comes to worse, I can make my own sizer . I have adjustable reamers. One thing I can't control though is the hardness. The guy I am buying the bullets from might be able to vary the hardness too. I can probably find a caster in our gun club as we have about 1200 members

saddlesore,

Mike Venturino has spoke about these issues with the 38-55 (I'm assuming its an 1894)?

If they chamber easy, they'll probably be safe, especially with your sedate loads. Another benefit is since it appears you are on the verge of easy chambering AND the bullet not slipping back into the fired brass (assuming it's not a ding from ejection), I'd tell you to slightly bell the case and seat the bullet again. If there's plenty of tension, not enough to push in the bullet deeper by hand, DO NOT re-size the case. Just bell, seat and crimp for your levergun. Hopefully the crimp on your seater die isn't scraping the front driving band.

Another question, the bullets that worked well measured .379 and were powder coated, correct? What diameter do they measure with your calipers or 1 inch mic (better)?
Coatings add a bit of diameter; it depends a bit whether the maker made .379 bullets then coated them or the coating was part of the diameter measurement. It might also be why they won't drop in a fired case. Never trust diameters put on commercially cast bullets; always try to verify, because it can eliminate easily avoidable variables.

I would try the same no size and chambering test with your .381 bullets; its pretty uncommon for a fixed chamber gun to have a smaller throat than groove diameter, unlike revolvers, where a soft alloy can help. So long as they chamber without forcing things or compromising function, the fatter the better, the harder the better. The fact .381 bullets are available are testimony to the common large bores (and probably throats) of some 38-55's.

Thanks for the help.

Yes, 1894.

I have measured several of the.379 bullets with powder coating with a 4 place micrometer.They all are right at .379. The bullets I have coming are .3795 out of the mold and adding powder coating should bring them up to .381 according to the vendor.

At present, I don't have any Starline brass not sized, but today, I am going to check the neck thickness on those as compared to Winchester and Remington.Starline is suppose to be thinner. Then will try your recommendation of of slightly bell and checking fit and then not sizing and loading.

Nasty storm coming in with single digit temps tonight so it might be a bit before I get the the range gain.

Update.

I tried the bell without sizing and they still won't push in.However, if I run them thru the .377expander without sizing they will push in. Bullets almost drop in. Expander plug only goes about 1/2 way to the final seating of the bullet, but the bullet will drop all the way to the primer hole

Measuring Starline vs Rem or Win, I found no discernible difference in neck wall thickness. Maybe. .0005 ,which is about as close as I can measure with my tools.

I sized and loaded some the. .379 bullets with the .377 diameter expanded plug I made and if I am careful and rotate cases as I work them, I get very little bulge of to one side. After loading, I checked the fit and they all drop flush to the rim into the chamber, with no pushing.

I think I do need to re-make the expander plug as long as the seated portion of the bullet. I will wait until the .381bullets come in as I will need to make the diameter .379.