Problems with .38/55 mold

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I bought this Rapine mold over a year ago, and just got around to loading it. It has two unusual features:

1) the bands all measure .379, except the rearmost at .380
2) there is no crimp groove

The round shown was reloaded without sizing the bullet or the already fired Winchester brass, and chambers ok in my Marlin .38/55 CB. However, the bullet is a loose fit in the case (twists easily and slides a bit back and forth); the RCBS die can't crimp it tightly enough.

Perhaps I bought the wrong mold for the application? Is this bullet designed for use in something other than a tube magazine?

[BABore]

It'll work fine where it's seated. Just size your cases first and expand, or at least partially size them by keeping the die end about 1/4" off of the shell holder. You don't have enough neck tension.

You should also slug your Marlin's barrel. They are notorious for having 0.380-0.382 groove diameter's and chamber's not large enough to handle the proper boolit size. Some have opted to have their chamber opened up to allow bigger boolits. Case wall thickness becomes an important issue when this situation occurs.

[44man]

It sounds like you have a generous chamber and you will need to size the brass and expand with just the right size so you have better neck tension. You can't cure loose fits with crimp. That hard of a crimp is not good if your boolits are soft. They will be sized when you shoot them as they try to iron out the crimp.
Boolit hardness dictates how much neck tension you can use. Too tight with a soft boolit will size them as you seat. Your boolits have the appearance of soft lead.
Something you have to work out yourself. You might consider harder boolits and tighter tension together.
Try partial sizing until you have the die adjusted for a good boolit fit without the need to expand and see what you get. Then you only need to flare a little for seating. Lighten the crimp to only enough to hold boolits in, in the tube. Filling the top groove with lube can aid the crimp by not letting the boolit move foreward too.

[homefront]

I did slug the barrel (.381), but haven't done a chamber cast - I was hoping this bullet would obturate if cast from WW, and pick up enough spin. Hard cast box bullets just don't shoot worth a darn, though I can get about 3" at 100 yards (6" drop when sighted at 50) with 10 grains of Unique (4227 is almost as good). I know I can get tighter with a bullet that fits the barrel. At the low velocities of the Unique load, drop at 200 yards is about 36"(!), which I'd like to cut at least in half with a faster load, but book loads of 4895, 4198, Rel 7, 3031, etc. are all way too fast for hard cast box bullets in this barrel.

[Kraschenbirn]

I only shoot .38-55s in a reproduction Highwall, but several things immediately come to mind:

1) You don't mention the weight of the boolit but, given the larger diameter driving band at the base, the three generous lube gooves and lack of a crimp groove, I suspect your boolit may have been designed for BP in single-shot rifles.

2) You might want to consider getting a Lee Factory Crimp Die. If you're not familiar with these, they're a collet-type die that compresses the case neck against the boolit rather than just rolling the edge of the neck into the crimp groove.

3) With a .381 bore, you may also want to consider "beagling" that mould out to drop at least a .382 diameter at the base band...if a .382 will chamber in your rifle.

4) For smokeless loads, I use AA5744 under a Lyman 375449 (w/o GC) for around 1350 fps.

Bill

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Great input, thanks. I suspected it might have been a BP mold.
It's a 245gr. bullet.
I thought about the FCD right off, and that the as-fired brass wouldn't give enough neck tension. I use FCD's for my .41 and .44 mags; I also see that Lee makes one for the .38-55. I'm going to remove the decapping pin from the sizing die and try a partial resize after seating, to increase the neck tension. I wonder if Lee would make a collet die for me? I just hate to go through all that to make a bullet work, if a different die would fix it all.

Again, thanks for all the input.

[BABore]

I wouldn't try the sizing after boolit seating thing. That's exactly how you make cast boolits easier to pound out with an inertia hammer. Brass has springback, lead has almost none. Your likely to size your boolit down even samller than it is now.

Don't know if your boolit is a BP design or not. I suspect not as the lube grooves are pretty shallow. There's alot of similar designs out there that serve double duty between leverguns and single shots. After a second look, I also noticed that all of your driving bands are nicely rounded. Is that how the mold is machined or fillout?

Check out the 38-55 forum on http://www.marlinowners.com/forums/

There's alot of guys dealing with the same problems that your likely to encounter with your groove/chamber relationship.

Also, for your information, Lee FCD's are of two different designs. The pistol dies have a normal roll crimp insert and a carbide sizing ring at their bottom. It's meant to give you a roll crimp and also iron out any case bulge that would prevent chambering. It's especially good at resizing cast boolits that are slightly bigger than the norm. The rifle FC die has a collet that indexes off of the shellholder. Contact closes the collet ring that is positioned at the approximate case length. The length of the collet ring is great enough to cover some variance in case length. No other sizing or resizing of the case or boolit takes place. You can overdue the collet pressure and actually imprint your own cannelure into a boolit.

[homefront]

No other sizing or resizing of the case or boolit takes place. You can overdue the collet pressure and actually imprint your own cannelure into a boolit.

Right. So I'd get a tighter crimp, without squeezing/resizing the entire neck?

[BABore]

Right. So I'd get a tighter crimp, without squeezing/resizing the entire neck?

Nope! You squeeze the case and the boolit down nice and tight when the collet is closed. When you relax the collet, the lead stays and the brass springs back a couple thousandths. Loose fit. Even if this didn't happen (and it does), the sized portion is only about 0.030" long. Hardly enough for proper neck tension.

[homefront]

Thanks for clarifying.

It's sounding like the way to make this work is to neck size the brass for better bullet pull.
I may as well try black powder while I'm at it.

[e15cap]

And turn the heat up on your melt. Too many round edges there.

[Boomer Mikey]

A crimp is no substitute for case neck wall tension against the bullet. Once the brass is bottomed out in the crimping groove there's nothing to be gained by adding more crimp... you're just deforming the bullet and reducing neck wall tension by making the bullet smaller.

The FCD is good for creating a crimp groove in the bullet where you want it including jacketed bullets as well as cast if you need it. The lube groove your crimping in has more than enough depth for the job.

Partial resizing the cases is similar to neck sizing bottleneck cases... the base of the case will fit the chamber better. Try to have the inside diameter of your case necks at least 0.002" - 0.003" smaller than your bullets OD after expanding the case mouths with an "M" die. Slower burning powders need the case wall tension to get the powder burning uniformly before releasing the bullet (higher pressure). Just enough crimp to remove the belling of the case mouth and tuck it into the crimp groove enough to prevent bullet setback in the magazine from recoil or chambering is all that's necessary.

It's better to create loads using a case filler like Winchester Super Grex to support the base of the bullet and hold the powder against the primer for uniformity. Super Grex also has a gas check effect that reduces leading with plain base bullets.

You're right, softer bullets are better in the 38-55... BHN 10-15 bullets should obturate fine at 1000 fps or better. A 250 grain bullet at 1300 fps with 10 grains of Unique generates ~2300 psi / 1422 = ~ BHN 16 maximum hardness for obturation. Air cooled wheel weight bullets will be between BHN 12-15.

Many fine articles can be found here:

http://www.lasc.us/CastBulletNotes.htm

Have fun,

Boomer

[Dan Cash]

Thanks for clarifying.

It's sounding like the way to make this work is to neck size the brass for better bullet pull.
I may as well try black powder while I'm at it.

You may find happiness with BP. I have a Marlin 1895 cowboy .45-70 that serves me very well with black. Being a Marlin, it is easy to pull the bolt and clean and you my well find clean up after black powder and lead bullet is easier than with smokeless.

[homefront]

What a great place - every reply helpful!
Thank you gentlemen, Very much!
I've got some experimenting to do. I'll post results with pics soon.

[Boomer Mikey]

I did slug the barrel (.381), but haven't done a chamber cast - I was hoping this bullet would obturate if cast from WW, and pick up enough spin. Hard cast box bullets just don't shoot worth a darn, though I can get about 3" at 100 yards (6" drop when sighted at 50) with 10 grains of Unique (4227 is almost as good). I know I can get tighter with a bullet that fits the barrel. At the low velocities of the Unique load, drop at 200 yards is about 36"(!), which I'd like to cut at least in half with a faster load, but book loads of 4895, 4198, Rel 7, 3031, etc. are all way too fast for hard cast box bullets in this barrel.

The hard cast bullets are probably too hard to obturate... most are between BHN 21-24. The original 38-55 loads were almost pure lead and obturation made them fill the bore completely. The "Book loads" will work fine with your 0.381" air cooled, wheel weight bullets.

The trick is to use a bullet soft enough to obturate and strong enough to grip the rifling without stripping at the velocity you want.

These articles may help:
http://www.lasc.us/TaylorLeadingDefined.htm
http://www.lasc.us/TaylorBulletWeakEnough.htm

Have fun,
Boomer

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Boomer,

Thanks for the guidance !