Home Forums Reloading Bullet Casting 405 grain cast bullet keyhole

I have some 405 grain Magma bullets I bought from a caster in Montana.

Loaded them above 36 grains of 5744.

They go through the target sideways at 25 yards. Kind of worried one might circle back and get me.


Rifle is a Miroku 45-70 Winchester.

At the range this afternoon this rifle would put the 300 grain Hornady hollow point into two inches at 100.

Cast bullets are a mystery to me.

Why are they tumbling?

Is one using gas checks?

Cast 405's (actually about 419) are nail drivers in a friend's Guide Gun. Not tried them in mine, but 400 grain jacketed slugs work extremely well for me.

Among the BPCR folks, thoughts are the 405's go to hell after about 400 yds. Most go heavier, like 540+ grainers when stretching out their Sharps.

No. They are a bevel base Magma 405.

Three grease grooves and a flat nose.

I bought a bunch of different bullets for this rifle and none of them were short enough.

Near as I can figure out the rifle is supposed to have a 1 in 20 twist. Supposed to be fast enough to stabilize.

Jim:

With a little surfing I find twists ranging from recent productions of 1:18 to about 1:22 for more ancient units. Seems all should be capable of stabilizing the typical 405 slug to at least 3-400 yds. In theory one should be good to go, as that's the slug they were built to handle.

I've used cast 405's in a 45-90 Sharps and they're flying true to at least 100 yds with BP. I've not stretched that out and will be going heavier (545 gr) when I do. Velocity is probably around 1,300 to 1,400 fps with the first firing of those cartridges. Might be able to speed that up in the second loading being able to fit more powder when the cartridges are up to chamber dimensions.

Any idea what velocity one is getting with your load?

My Guide Gun is fun to shoot with the typical factory fodder going out at about 1,250 fps also with a 1:20 twist. Same for my friend's unit with his cast slugs. I jacked that up a bit with some hand loads to around 1,750, and it kills on both ends again though with jacketed bullets. It is not pleasant to shoot.

About my only suggestion is that one mic a few slugs to see what they measure. Also, if one has a BPCR neighbor about with a lube/sizer, one could try those slugs with a gas check installed. The examples I saw with my surfing show a beveled base suggesting there's room for a gas check there. Could be there's enough heat/pressure to cut past the belts, and that would create all kinds of issues.

Gas check link

Might also try them in some other rifle to see if results are similar.

One could also quiz the Shiloh forum and likely get an authoritative answer. First though, one will have to take a beating from that crowd for using smokeless.

Do keep us up on your findings and good luck.

I've not used 5744, but I looked at the data and nothing about 36 grains seemed out of place. If anything, it would be considered warm, which I wouldn't think would be contributing to your current problem. If your bullets are undersized, cast hard, and bevel based, it's likely that your bullets are not slugging up to fit the bore, and the bevel base is allowing gas to slip around it.
Check your bullet diameter and inquire as to the alloy/brinnel hardness of those bullets. Most commercial cast bullets are too hard with lube way too hard to do any good (it'll stay on during shipping though). Then, they put a bevel base on them so "it makes them easier to load" when it reality, all it does is give gas a path to go where you don't want it.
No, I'm not a fan of MOST commercial cast bullets.

Try another propellant perhaps. Some barrels and some bullets (cast) can be fussy sometimes. IMR 4198, either 4895, and H322 have all shown me good attitude in various 45-70s with cast bullets.

I use 5744 for a number of loadings. 36gr will give you a VERY hot load (somewhere in the 1700fps area) without a gas check and "may" not be properly sealing the bore. Try ~28 - 30.0gr which will likely give you ~1300 to 1400fps which may allow it to fly better.

What is the OAL?

I'm in the group thinking they may be undersized.

Ed

They list them at .458.

Prefer .459 cast bullet size for my rifles.

My hunting partner is using about 52 gains of 4895, and having no issues that I know of. He's only papered out to 100 yds. I don't know, however, what brand of slug he's using, as he's not started pouring his own.

Have you slugged the barrel?

Seat them deeper to fit....or seat your magma jobbys OUT until the lever closes with just a hint of resistance. Keep in mind they should function even if the chamber is dirty. Reduce your load accordingly and work back up to your desired speed.
Give them a slight roll crimp, wherever it may be so they don't push into the case under recoil in the magazine. The crimp groove location is secondary to jumping into the lands. Cast rifle loads detest jump...especially if the throat is cavernous and you're not making minimal land/throat contact.

It sounds like a combo of undersized (to the throat) and unbalanced (unstable) as the bullet slams unconcentric to the bore upon ignition. This gets worse with jump as the bullet deforms even more as it hits with the point off center upon ignition. Fill that "freebore" with the bullet.

A cast load that's truly undersized for the BARREL will lead the [bleep] out of stuff; especially if hard and even more so with a [bleep] lube. I'd be sure to check the barrel to make sure that isn't the case before firing more rounds down it. If its clean and the rifling is easily discerned, the bullet fit/jump in the throat is the culprit. If you can't see rifling or see globs/patches of layered lead, the groove is too large for the bullets you are using and it needs cleaned.

I cast my own for my Guide Gun. I use gas check bullets for high velocity like your friend is shooting.

If your bullets do not have gas checks I would keep my loads to 1200 FPS or less. Try it and see.

Wonder if the bullets could have gotten squashed in the loading. Could the bullets have stripped in the rifling? How about pulling a bullet from a loaded round. Measure to see if the bullet is going down the tube at .458.

Bullet is too small. Skids rifling. You have Laser Cast and they are small. You need .460". Do not fool with .457".

Agree.

Bullets likely undersized. As a start, you need to slug your barrel to find GROOVE diameter. Then have the bullet 0.001”-0.003” over groove diameter. That will get you closer, but is not really the answer.

Ultimately, you want to know the diameter of your chamber’s THROAT, by doing a “pound cast” of it. Then match bullet diameter to throat diameter ( or just a smidge under, Ex. 0005” smaller). This will be the best way for selection bullet diameter for your barrel.

The pathway of using groove diameter +” a little extra” is a shortcut to the variance you may see in your throat. Do the pound cast method. It’s not difficult. You learn what you need to know, and it allows you to understand your barrel / casting MUCH better. It ultimately saves you time, money and frustration, as you will have an accurate load developed in a shorter time.

https://www.artfulbullet.com/index.php?threads/article-2-how-i-make-pound-casts.131/

Thank goodness they are undersized. 36 grains of 5744 is 8 or 10 grains more than you should be shooting in that gun...

Lyman lists 36.0 at 27,000 cup with a 405 cast.

However, 36.0 grains of IMR 4198 makes a nice start load at milder pressures and only a bit less speed.

I have abandoned those for a while.


I as of yet have not slugged anything.