Making 30 XCB cases: a quick tutorial

[tomme boy]

Wouldn't be better to use a jacketed bullet to fireform the cases. That way you can up the PSI to form them better? Or just run the full PSI loads you are already running with the normal loads? I think they would fill out much better than a lower PSI load you are going to use. You might have to load them a couple of times to fill out with the lower loads.

[dtknowles]

Wouldn't be better to use a jacketed bullet to fireform the cases. That way you can up the PSI to form them better? Or just run the full PSI loads you are already running with the normal loads? I think they would fill out much better than a lower PSI load you are going to use. You might have to load them a couple of times to fill out with the lower loads.

Jacketed bullets will foul the bore and require cleaning and reseasoning.

Tim

[Bjornb]

The 3031 loads will be in the 27k range, and if it's not enough to iron out the necks I'll just pull them and do it again. I've got the time.

[geargnasher]

I think Tomme said the Remington 8mm Mauser brass had such thin necks as to be pretty much useless, it appears you have proven him right. I'm looking for .0135" minimum. Got .0145" easily with Turkish headstamped 8mm brass, but only had two examples of it.

Gear

[MarkP]

The screenshot below is part of what you are seeing, final draw punches are tapered such that there is a thickness transition in the shoulder junction. Your neck is now located in the former shoulder area. When the diameter is decreased the walls will thicken (constant volume) and you should see a slight increase in length, and just the opposite when necking up brass, thinner wallsand slightely shorter in length. In addition, a family of cartridges will share the same cup (the brass part that is blanked from strip and formed into a cup and annealed) 1st draw, 2nd draw, tooling. The third draw or last draw punch will be different for each cartridge. For example a 358 W will have a different final draw punch as compared to a 338 Federal, 308 Win, 7-08, ect. There can be some overlap such as a 260 Rem may use the same final draw as a 7-08. A 243 final draw punch would have the largest diameter (thinnest walls at mouth of final draw) within that family of cartridges. Tapering usually occurs with 3 or 4 dies, first die sets the body taper, latter dies form shoulder and neck.

[Bjornb]

I think Tomme said the Remington 8mm Mauser brass had such thin necks as to be pretty much useless, it appears you have proven him right. I'm looking for .0135" minimum. Got .0145" easily with Turkish headstamped 8mm brass, but only had two examples of it.

Gear

I checked out some other headstamps after I saw your post. I also have a good stash of PPU 8mm cases, and they miked .0115-.0125, none over .0125.
I have a few hundred Berdan-primed cases, 1942 Adolf-era 8x57 brass, it all mikes .015-.016.
So if you're ready to go Berdan let me know! At least 80% of the primers go bang!

On a serious note: I'll fireform these and try them out alongside the 7x57 and 30-06 cases. I can't hurt to try every combination.

[btroj]

Send those Berdan cases to Tim, for a few bucks apiece he can make them boxer primer ready!

[btroj]

Bjorn, have you tried any of those cases with the thinner necks? Would be interesting to see if .003 necks clearance or so makes any difference if shot with same load as a closer fitting neck.

[Bjornb]

I'm fire forming 55 cases this Saturday or Sunday (some had neck striations from forming and weren't uniform enough in the neck/shoulder area). Then I'll load them up immediately and post the results.

[tomme boy]

I think if I was going to do this cartridge, I would be using the 3006 brass. I would also spec the reamer for the neck for the 3006 brass so the only thing I would have to do is a very very light cleaning of the neck on the brass.

Wouldn't it be easier this way? Maybe contact Tim to see if you could open the neck a little? Or speck the reamer for the 8mm brass? I know this is a on going learning for this new cartridge so just asking ???'s

[Bjornb]

Here's what I'm learning: with the necks turned to .125 so I have about .0015 nominal clearance with a .311 bullet, the fired brass will not accept a bullet. So all I've had to do is reprime, charge and seat a new bullet. The fired cases will let me enter about a gas check's worth of bullet. I'll be curious to hear if Gear and Btroj have similar chambering issues.

[btroj]

I do size but minimally. With my cases I use a .333 bushing, this lets me seat a bullet with just a very slight flair. I use an M-die for that, the spud doesn't expand the neck at all. I tried a .335 bushing and it was too loose, I could spin seated bullets by hand.

I haven't measured but I'm sure I am sizing cases around .003 at the present. As brass hardens with use that will change too as the cases will spring back on firing and sizing.

I may make some more cases and see what happens if I go to a thinner neck. Only problem will be that I will need a smaller bushing to get any bullet tension at all. Might order a .330 and give it a go.

[geargnasher]

With hotter loads and soft necks, mine need a resize. I measured my 1x fired necks tonight, they're all .3370" on the money, the harder, 9x fired necks that were never annealed and hard to begin with come out about .3373". I'm using a .333 bushing and the new batch of softer stuff is finishing at .3350", the harder necks at .3355" or so, some larger.

Going .3095" with the bullets makes the .333 bushing BARELY enough, the military brass still doesn't clean up 100% even then, it would be much better with .310" or larger bullets, which is what I originally intended to use and was discussed when we spec'd the reamer.

If I were to do an '06 reamer for cast, I'd go .337" with a standard '06 throat, but I'd go .336" or less with a longer, shallower throat and smaller throat entrance, like .3095" tops. I have a very tight .308 barrel to test that theory with, it has a super-long, shallow throat and .3095" throat entrance. If that works out (who knows), I might just get a similar throat cut and a .335" neck on my next '06. Only problem with that is getting a gunsmith willing to do it, most of them balk if going below .337" due to pressure excursions if anyone else gets hold the the rifle and tries to shoot factory jacketed ammo in it. The XCB won't chamber .308 OR 06 factory ammo, so no worries, we could have gone tighter but I suppose didn't know better, it was a learning experience and that's why we did it in the first place.

Gear

[Bjornb]

Yeah once I got my necks squared away (turned to .0125) I've been able to chamber .311 bullets without forcing the bolt. Tim was afraid I would shave lead above .310 but I've extracted several rounds and there are no signs of force applied to the bullet. Evidently the throat is large enough to fit the NOE bullet as cast.

[geargnasher]

Mine start to shave at .3105". It was the first chamber cut, should have been the largest throat I would think. A slug shows .3106", surprisingly right on spec.

Gear

[MBTcustom]

Mine start to shave at .3105". It was the first chamber cut, should have been the largest throat I would think. A slug shows .3106", surprisingly right on spec.

Gear

Gear, when using good quality Reamers with stone sharpened edges, you would be surprised how consistent the diameters are.
I just cut two more chambers last week, and carefully measured the throats on them. It will surprise you to know that the measurements I took are nearly identical to those you just posted.
I had cautioned Bjornb to be careful going anything over .310 because at that point you are a mere .0005 away from max diameter. That's getting real close.

[runfiverun]

those are the same neck striations I get with fired Remington brass.
I'm gonna try bumping the shoulder first with a 358 win die on the next go-round.

[Bjornb]

those are the same neck striations I get with fired Remington brass.
I'm gonna try bumping the shoulder first with a 358 win die on the next go-round.

Yep. That's what I'm using. Fired Remington brass. 358 die it is. Got an RCBS one.

[kbstenberg]

I was thinking the other day about how you ream out the inside of the neck (the doughnut) and were having problems with consistency. Would it help if you put the case to be reamed into some kind of a case length gauge and left the length gauge on to support the outside neck/shoulder when trimming the inside of the neck.
Like most novists their trying to help is old news, or unworkable.

[Bjornb]

This tool is what I have found to be excellent when it comes to removing the "donut" and turn the outside neck at the same time:

The mandrel, which supports the outside cutter, has its own cutter that ONLY cuts to the diameter of the mandrel itself, thereby only removing inside neck material that is in excess of the desired ID.