An Experiment in Headspacing Non-Headspaceable Cartridge for Fireforming

[c-fbmi]

First I'll start with my problem................I am building a 458 based on the 375/416 Ruger case, however I have moved the shoulder slightly ahead and increased it to 40 degrees. I do not intend to use Horn brass for this rifle as it is sh!t and I have successfully fireformed 300 WM to 375 Ruger, allowing me to use whomevers brass I choose for the Rugers. What I have and will be using, is 300 new R-P 416 Rem brass, so herein lies the problem. I can neck the 416 up to 458 no problem, then FL size in my Lott die set and it comes out looking very nice, but straight. Now I trim it and size the inside of the neck and voila, I have brass that will fit and fireform, but without any way to headspace for the fireforming process.

The solution...........Now I am aware that one can jam the bullet into the lands for this process, if one wishes to waste 300 .458 bullets at about a buck and a half a pop. I can use lead cast bullets but I'm uncertain if they will withstand the firing pin blow and maintain a tight enough headspace. Also if I wish to use CoW or something similar I need a method of headspacing the case correctly. The solution came to me the other night as I was loading 45 ACP, why not headspace on the case mouth. The chamber case mouth is cut at a 45 degree angle but should still be sharp enough to headspace on, so I determined my chamber length to be .020 longer than max case length, which I nominally set at 2.62" (this is normal for reamer makers to give an extra .020" of neck length to alleviate case mouth crunch as the brass grows during firings and it is even more prevalent in DG cartridges for obvious reasons. I spoke with Dave Kiff about this at length while designing this reamer). So I trimmed my cases to 2.64 and gave them a slight bell so they are very snug to the case neck walls in the chamber and should come up hard against the chamber case mouth. I also gave the cases almost no chamfer, just taking the trimmer flashing off but not chamfering the outside of the case mouth hardly at all.
The problem is exasperated by the fact I do not have dies yet for this cartridge and will be making the dies after I have cases fireformed. Kinda a "Catch 22" situation, otherwise I could just take the cases up to 475 with my 470 NE dies and then neck it back down creating the necessary shoulder to headspace.

Second problem............Broke my action wrench trying to remove barrel to rechamber it for this cartridge, so all is on hold right now...........I'll have to get back to y'all and let you know how it works..........I have great hopes though.


Has anyone ever tried this or even thought about it?

 

[scott585]

would the extractor not hold it well enough to fireform with cream of wheat? sort of like 7mm-08 fired accidentally in 30-06 guns

 

[burnt_servo]

ran into something similar with a 9.3x62 improved I've been playing with using 30-06 brass .

I necked up the 06 cases with a 375 die , that left no shoulder and the 375 expander ball wasn't big enough to create a false shoulder to hold it tight in the chamber .

what I ended up doing was just necking up with a .375 die , then taking a .375 ball , wrapping a piece of masking tape around it a couple times , then inserting into the neck and lightly crimping it with the 9.3 die .

the neck was now tight into the chamber , or at least tight enough to keep the round seated to the bolt face when firing .

 

[c-fbmi]

would the extractor not hold it well enough to fireform with cream of wheat? sort of like 7mm-08 fired accidentally in 30-06 guns

S585..........the 308 case was designed to headspace and fire in a 30-06 chamber, it was one of the design criteria when the military commissioned a new shorter 30 cal cartridge, hence all 308 based cartridges 30 cal and under SHOULD if properly made, headspace and fire in an '06. The Rem 700 extractor (which is the rifle I'm using for this build) will not reliably do this like a big Mauser extractor may. Many Mauser extractors have too much play to be relied on to correctly headspace a cartridge either, but that's another whole set of problems.

 

[c-fbmi]

ran into something similar with a 9.3x62 improved I've been playing with using 30-06 brass .

I necked up the 06 cases with a 375 die , that left no shoulder and the 375 expander ball wasn't big enough to create a false shoulder to hold it tight in the chamber .

what I ended up doing was just necking up with a .375 die , then taking a .375 ball , wrapping a piece of masking tape around it a couple times , then inserting into the neck and lightly crimping it with the 9.3 die .

the neck was now tight into the chamber , or at least tight enough to keep the round seated to the bolt face when firing .

Yep BS, when making 9.3X62 I take 35 Whelen brass up to 40 cal and then run it through the 9.3 die until the bolt closes with a good bump. Then one can just load as normal with no fireforming load required. I can take the case up all the way to 50 cal if I want, but I have no way of necking it back down to 458 and leaving a shoulder for headspacing...........what I need is a 458 WSM sizer die.............cause they're just so common..........

 

[burnt_servo]

Yep BS, when making 9.3X62 I take 35 Whelen brass up to 40 cal and then run it through the 9.3 die until the bolt closes with a good bump. Then one can just load as normal with no fireforming load required. I can take the case up all the way to 50 cal if I want, but I have no way of necking it back down to 458 and leaving a shoulder for headspacing...........what I need is a 458 WSM sizer die.............cause they're just so common..........

when I did my brass , 375 was the biggest die I had on hand at the time . not big enough to create a shoulder , but it was big enough to make for a tight fitting neck .

if you have a lathe , build a expander ball to make the neck just over size enough that it drags in the chamber , then find something solid to fill the neck to keep it from collapsing too much to keep things tight ( like a paper patched 458 round ball maybe ... ie masking tape around a round ball ) .

it should feel like a oversized round going in when closing the bolt .

you just need to keep the case head firmly touching the bolt face

I was also using a case full of powder to hold the ball in place on the back end , with a crimp on the case mouth on the other end .

a fast pistol powder and a filler would do the same thing . I had no pistol powder but lots of imr4831 on hand

 

[tbdtp]

All my wildcats are based on necking down the parent cartridge and with one like the 17ah you make a false shoulder at the base of the neck. Would you be able to turn a expender ball at just over 458? Say neck up to 465 ish then neck back down to 458 leaving a slight crush fit. A expander ball chucked in a drill with a piece of emery cloth has worked for me before to build a custom expander before.

 

[btridge]

if your keeping the .515 shoulder diameter, I would make a .483 expander and then neck back to .458 creating a good crush fit. fire form using COW method then load and fire 3 with bullets to make sure they fit your chamber perfectly and send them off to the die maker, or use when making your own dies.

 

[BigUglyMan]

Since you have the reamer why not make a forming die out of round bar? Then you could go to .475 and run it through your home-made forming die and you should be good to go. No need for it to be hardened since all you will likely do is 100 cases before your new dies show up.

 

[c-fbmi]

Gentlemen, as I explained earlier I have to make my own dies, I bought a die making reamer with the chambering reamer, and yes I could make the die first, but it's better to have several fired cases when making the dies in order to get them perfect when FL sizing.
BUM......Yes I could do it that way by just using a 7/8 FT bolt and have made "make shift" dies before like this, or I could even buy blank die stock from Huntingtons and make up a case forming die.........but that's a lot of work and I'm lazy........if I can get a good positive headspace by doing it this way, on the case mouth, and I believe it will work, it is something anyone can do without owning a lathe. Hence the value of putting it on here, with a lathe virtually anything is possible, but doing it this way can be done by anyone with a relatively well stocked and tooled loading room.

For this project, I acquired a set of 458 dies with the rifle, I will be annealing them, recutting them for sizing and seating, polishing and rehardening them. And if I f**k them up I'm not out a nickel..........but have done this many times so it's not beyond my abilities at all. If you don't harden them right away BUM, they gather grit and scratch the hell out of the case necks, even after 15-20 rounds of what appears to be new brass, they will inevitably pick up something and scratch the sh!t out of things........this in turn causes premature case neck splitting and failure, even before I get to oversize the primer pockets !!!!!!!!

 

[Ganderite]

I fI was doing it, this is what I would do.

I would fire form with cast bullets, loaded upside down so as to get maximum resistance. And I would lube the case, so it would set back on recoil, and not stretch.

 

[Why not?]

Doug,

1)Neck up a case to .475.

2)Centre bore a 7/8-14 bolt it in your lathe.

3)Ream a stubby die in the bolt to form the shoulder on the brass you have necked up to .475

4)Screw die into your press, and size the neck down until you have a crush fit on the brass, same as you do when making your 9.3 brass

5)Load and fireform

Ted

 

[scott585]

S585..........the 308 case was designed to headspace and fire in a 30-06 chamber, it was one of the design criteria when the military commissioned a new shorter 30 cal cartridge, hence all 308 based cartridges 30 cal and under SHOULD if properly made, headspace and fire in an '06. The Rem 700 extractor (which is the rifle I'm using for this build) will not reliably do this like a big Mauser extractor may. Many Mauser extractors have too much play to be relied on to correctly headspace a cartridge either, but that's another whole set of problems.

no, it was designed to use the same bolt face, just like you are doing here. it wont headspace, the shoulder doesn't even come close to touching in a -06 chamber, it is held in by the extractor and the case stays straight because the chamber wall doesnt let it tip very far. i dont think it needs very much extractor strength, as there are lots of pictures of cases with a smaller case head accidentally fireformed in different chambers

i would say you have nothing to lose by getting some soft primers (federal?) and trying it, if they dont fire, it cost you a few cents worth of primers and powder.

 

[c-fbmi]

no, it was designed to use the same bolt face, just like you are doing here. it wont headspace, the shoulder doesn't even come close to touching in a -06 chamber, it is held in by the extractor and the case stays straight because the chamber wall doesnt let it tip very far. i dont think it needs very much extractor strength, as there are lots of pictures of cases with a smaller case head accidentally fireformed in different chambers

i would say you have nothing to lose by getting some soft primers (federal?) and trying it, if they dont fire, it cost you a few cents worth of primers and powder.

S585........you really do need to look up your cartridge history. The 7.62 NATO cartridge was in fact designed to headspace and fire in a 30-06 chamber. It headspaces because the shoulder of the 7.62 NATO is a larger diameter than the corresponding spot of the 30-06 case/chamber. You are correct in saying it does not come close to headspacing on the datum line, but it does none the less headspace in the '06 chamber and was a design criteria, by the military, of the 7.62 NATO.
S585...you need to understand head space can be achieved in many ways, rims, belts, datum regions on shoulders, case mouths or even friction fit as in the 308 - 30-06. Any method that will consistently hold the case head snugly against the bolt face while being struck by the firing pin is an acceptable means of headspacing. Several of which have been discussed in this thread.......I'm proposing case mouth head spacing, Ganderite proposes bullet engagement head spacing, B_S proposes a friction fit head space by making the case neck oversize and causing it to fit very tightly in the chamber, and Why Not? proposes making a die and actually creating a shoulder to headspace, which will be the final form with this case once I get a shoulder on it.

The problem is not that the primers won't fire when struck by the pin, it's more about the firing pin blow driving the case .030" into the chamber and then firing. This would cause the case to stretch .030" somewhere along it's body and create a very good chance for head separation if not this firing then likely the second or third. Which is not something one wants to entertain on a DG rifle.........ever !!!!