.40-40 fireform

[Battis]

I've never fire formed a case, but I think I should to form a .40-40 Maynard from .30-40 Krag brass. The .40-40 will be loaded with black powder, so should I form it with BP?

[DonHowe]

What will it be fired in?
A case full of black with any .40 bullet will certainly do the job but there are other methods.

[Battis]

It'll be fired from an 1873 Maynard.

[Wayne Smith]

Use a powder appropriate for the Firearm, not the cartridge!

[BP Dave]

I think your best bet would be to cut off the Krag case to the right length--maybe leave it a few 1/1000ths over--then expand the neck to seat a bullet and load normally. You should get a little body expansion, but it isn't very much, just going from the slight taper of the Krag to pretty much a straight case. There are smokeless loads out there for the Maynard cartridges, but I would stick with black powder both for your initial "fire forming" load and for subsequent loading.

I assume you're using brass do-nuts for the thick rim.

[Battis]

The case length for the 1873 Maynard is listed as 1.84". The most I can get from a .30-40 Krag case is 1.75" without going into the neck of the Krag case. So, I can't cut it a little longer. I have the CH4D FL sizing die, and I'm waiting for the Accurate mold to get here (I can't do much without the bullet). The spacer rings for the rim are also on their way.
I'll only use black powder. I'm thinking that the shorter case (1.75") should be fine.

[BP Dave]

You should cut the case off a little longer than 1.84. That will be just barely into the neck. Then you expand the shortened case with a tapered expander. When you do that it will ordinarily shorten the overall length a little, because the metal pulls back toward the head as it is expanded. Depending on how carefully you do it, it will also likely end up with a case mouth that is slightly uneven, which you can clean up by trimming slightly if it is too uneven. When you fire the case the first time it should blow it out from a slight taper to very close to a straight cylinder. That will likely reduce the length just a little bit more, which is why you leave it long when you first cut the case.

You could go with the shorter case, but you would end up with about a tenth of an inch of extra freebore where the bullet is not supported as it jumps from the case to the rifling--it might not make much difference, but could reduce your accuracy. You would also be burning powder in the end of your chamber--if you ever go back to full-length cases you could end up with the same type of fouling and erosion problems that can crop up when shooting .38 Special in a .357 Magnum, except you are dealing with steel that is almost 150 years old.

[Battis]

I was thinking that fire forming the case would expand the small section of the neck, as you said (I think that's what you meant). But I'm not a fire former so I don't know for sure. I could also set the bullet further out of the case so it wouldn't have to jump as far into the rifling. The case length for the 1865 and 1882 Maynards is 1.75", but longer for the 1873 with that extra headspace.
Interesting gun. I bought it with a smoothbore barrel, then found the rifled barrel on Gunbroker.

[BP Dave]

Well, if you're intent on fireforming instead of neck expanding I would leave the case full length, load with perhaps a third to a half case full of black powder, fill the rest with a filler such as cream of wheat, and seal with wax or glue. You might want to try a couple first to see if it blows the neck out enough and adjust your powder charge and filler accordingly. If the necks split or if your load doesn't have enough umph to blow the neck out straight you could try annealing the neck, but if it's new brass the factory annealing should be enough. You could then trim the fireformed cases to length. But with fireforming, for each case you're expending about a half-charge of black powder and a primer without actually putting a bullet downrange.

[Battis]

Neck expanding does make the most sense. When I get all of the components together, I'll just cut the case as long as I can, load powder and bullets and shoot.

[DonHowe]

It'll be fired from an 1873 Maynard.

Cut the case to length, expand the mouth to fit your bullet, fill case with BP to bullet base, seat bullet and fire the round. The expanded case will be skinny behind the expanded portion but firing will straighten it out.
You can use a BP substitute powder. The only one I have experience with is Pyrodex.

[Battis]

My point is that I can't get enough length out of the .30-40 Krag case without going into the neck. I'll try it when I get the mold and cast some boolits.

[Wayne Smith]

I just expanded some 30-06 cases up to 9.3 to cut down to 57mm. Only lost four of 50 and they were of unknown previous use. Did not anneal, but maybe should have, did not use my 8mm as an intermediate step and absolutely should have. Use any intermediate step you have but don't hesitate to expand those necks.

[Deadeye Bly]

Use BP Daves method. Fireform the case before trimming it. I would go about 2/3 full of black instead of 1/2 full but that's just me. Use what works for you. I have found that neck expanding is not as accurate as fireforming from scratch. Lately I have been expanding to 35 caliber, loading with black and a 38 special lead bullet and firing. This gives a well formed case in one firing.

[Wayne Smith]

When the parent case is the same size as the chamber I would agree. 9x47R fireforms to 10.5x47R without a problem. When the parent case is longer than the chamber I would question it. My plan in making 9.3x57 out of 30/06 is to expand the neck, trim the case until it fits my chamber, set my trimmer at that length and trim the rest of the cases.

[Battis]

Anyone know the OAL of a Maynard .40-40 cartridge?

[BP Dave]

James Grant in his More Single Shots book lists the Maynard .40-40 case lengths as follows:
Percussion (1865) 1 3/4"
1873 1 27/32"
1882 1 25/32"
The most common length I see listed in other sources for the 1873 is 1.84", which I presume is the decimal conversion of 1 27/32" (.184375) rounded off to two digits.

I've never seen an explanation for the slight length differences, but I suspect the same chamber dimensions were used for all three cartridges, so that barrels would be interchangeable among the different frames and that the different case lengths are the result of the varying distances between the barrel and the breech face as a result of the different thicknesses of the case rims. That would not account for the different bullet diameters that Grant reports (.422, .421, and .417), but if he was measuring cartridges it is possible that late 1800's manufacturing variances would account for those variations.

[Battis]

The 1873 is longer because of the thick rim (1.84") I was looking for cartridge overall length but then again, that would depend on the bullet used. I cast some bullets from the Accurate mold (.419"), I formed some brass from .30-40, I got the spacer rings, and I made up a dummy round. Just trying to figure out how deep to set the bullet. I guess that would depend on how much BP I use.
Back to the salt mines...

[BP Dave]

Grant lists the 1873 .40-40 with an OAL of 2 11/32". With dimensions given in 32nds of an inch there is probably some wiggle room.

[Battis]

According to the InnerWeb - 2 11/32 = 2.34375. Good info.
How many books does James Grant have out there? It looks interesting.