.30 XCB wildcat, from scratch.

[cbrick]

Ok Tim, in regards to picture #2. Paper coffee cups aren't all that expensive, if you would like to try a clean one I could send you some.

Rick

[Larry Gibson]

I agree.

My answer to the 30 XBC-------------30 BR---1-12 Twist---309 x .100 deep throat with 1.5 deg taper leade (bump die to match throat)............LEARN TO READ WIND!!!!!!

Accuracy for competition was not the prime factor in the design of the 30x57 (30 XBC). Usable accuracy at high velocity (2500 to perhaps 3000 fps) with a1 50 - 180 gr cast bullet over slower burning powders in a 13" or slower twist barrel for hunting use was. However, with the design and case capacity of the cartridge excellent accuracy should certainly be feasable. The 30 BR is certainly an excellent cartridge for bench and target shooting but it lacks the case capacity and neck length for the desired results as mentioned.

Larry Gibson

[MBTcustom]

Ok Tim, in regards to picture #2. Paper coffee cups aren't all that expensive, if you would like to try a clean one I could send you some.

Rick

That's not coffee, that's cutting oil, and half a cup of that will wake you up much faster. LOL!

[cbrick]

I knew that . . . Just couldn't resist.

Rick

[swheeler]

I always thought this idea sounded good when Larry started posting about it 7-8 years ago. All the attributes he listed looked to be the real deal for lauching cast bullets at high velocity, it will be interesting to see how it pans out.

[MBTcustom]

I always thought this idea sounded good when Larry started posting about it 7-8 years ago. All the attributes he listed looked to be the real deal for lauching cast bullets at high velocity, it will be interesting to see how it pans out.

Actually, this project has been discussed in many different circles by many different people for many years. There is nothing new under the sun, especially when you are talking about 30-06 based cartridges.
That said, Larry has been right at the front of this project (along with Lamar IIRC) from the very beginning. In fact, when we all got together on this project, Larry already had the dummy cartridges made up and sent them to me. Most of the rest of the design was centered around chamber characteristics like neck length and diameter, throat angle etc etc etc.
We only decided to call it the XCB (extreme Cast Boolit), because this iteration of this wildcat was designed specifically to cater to the cast boolit extremists.
But please do not imply that at any time I would deny Larry Gibsons central role in this concept. In fact, I will be building him one of these rifles too, nearly free of charge for his considerable contribution to the project, and to our sport.
Of course, he's being smart by holding back so that we can get all the bugs worked out before he sends me a rifle to build on LOL!

BTW Larry, I hope you are scouting out a barrel. Good quality 30 caliber barrels are getting harder and harder to find, and the manufacturers are getting more and more backed up.
Never seen anything like it ('course I'm a young sprout).
It's absolutely amazing how the more out of stock things get, the more folks need exactly what is unavailable. You wouldn't believe how fast 22 rifles are flying off the shelves around here. Ammo's at $60 a 500 brick, and folks can't get enough of it.
Nuts!

[MBTcustom]

Tim, I was looking at a brick of 500 for $135.00 today of course that was the high end. Pretty sure soon I be able to trade that other brick at the house for a used rifle or redhawk.

And what do you mean that is not coffee on the lathe? Man it sure tasted bad last time I was over there.

And I'll bet you were good and regular for the rest of the day. LOL!

[MBTcustom]

So it seems. I just remember reading about it years ago and Larry explaining it's attributes in detail, seemed like a good idea to me then and still does.

Indeed! In fact, the only real downside is the fact that you have to neck turn which is a PITA.
The pros are many, and some of them are not readily apparent.
One thing about doing this conversion is that when the dies are shortened, it actually makes the brass a nearly perfect fit in the chamber even having been FL sized. It really was satisfying to slip a FL sized cartridge into the chamber and have to push it the last 3/8" with my finger to seat it. Then, when the rifle was turned barrel up, the brass would not fall out unless the rifle was bumped on the floor. Like it was fireformed and neck sized right out of the FL sizing dies. Sweet.
I personally hold that FL sized brass is more accurate albeit undersized, but now, we get to have our cake and eat it too it seems!

[swheeler]

I'm waiting for some reports on high velocity and pictures of targets. I know Ian got his and looks like Brad is next, then Run and Larry. I'm gettin impatienthehehe

[geargnasher]

I got sidetracked with this little Savage .308 Pig Gun I got for Christmas. I got it to shoot purty good while crowding around 2400 fps, but hit a wall (as expected) with 50/50 alloy. Strange thing is, my 12-twist .30 XCB is up against the same wall with the same alloy and four more inches of barrel. I'm learnin' stuff for sure. Powders including 3031, 760, 780, H4350, and H4831 have been tried in both, but no buffer or duplexing tricks as yet. The twist isn't the limiting factor or the Pig Gun wouldn't shoot past 2200, following the results of the XCB with the same boolit and much the same tolerances.

Gear

[Larry Gibson]

Gear

With your loading techniques you've pushed it to 144,000 RPM at 2400 fps with the 12" twist.
If you're 30x57 (30 XBC) has a 10" twist the close tolerance and cartridge have enabled you to push the Threshold higher at 2400 fps.
An accomplishment in and of itself.
A change of bullet design and/or an alloy change may allow pushing higher.


Larry Gibson

hopefully I didn't change the meaning of your words with this clean-up.

[runfiverun]

weight reduction= instant velocity increase.



one of the HV tricks bass told me long ago.

[Larry Gibson]

O

weight reduction= instant velocity increase.



one of the HV tricks bass told me long ago.

Especially if the weight comes off a long bore riding nose and the bullet has a 55-65 % bearing surface. The Loverin and LBT designs are excellent for HV. The LBT was a favorite of bass' s.



Larry Gibson

[Love Life]

I'm eyeballing this cartridge for a different use. I bet it would be about perfect for launching 185 Juggernauts without having to step up to the 30-06 or magnum class of cartridges.

[runfiverun]

I'm using a 'similar' cartridge to launch .284 diameter 140's to about 3-k if I wanna show off.
I generally keep them around 2880 though.

by bumping the pressure to the 55-60k range and using a long 175-180gr smk type bullet, yeah I can see 2800fps doable.
especially if this was done on a long action.
you'd be on your own as far as data was concerned but you should be able find plenty to start with. [7.5 swiss,7.7 jap, split 308/06,, etc]

[MBTcustom]

Brad's action is now blued, along with his rings. It's beautiful.
Almost there.

[runfiverun]

this round can be done on a 308 type action.
it's like the 257 Roberts and 6mm rem's that were done on them.
the throat length and the mag length are gonna be your issues but it's doable.
in this case the throat is set to a specific measurement so as long as those angles are followed the boolit length is actually negotiable.
you have the longer neck length to help hold more drive band length.

[Larry Gibson]

sgt.mike

That was cute

While the 30x57 can be used on many actions one of it's attributes is the standard taper of the '06 and most Mauser cartridges. Thus it will feed w/o action alteration in any Mauser action. Also while a 2.8" "medium length action may work ok it is really better suited for the 3" Mauser length actions and will feed many different nose shapes better in the standard 3.3" length Mauser action. Additionally if used in the standard length action and the 30x57 case does not have the capacity with slower burning powder (another attribute) the chamber can be reamed deeper with the same reamer until the desired case capacity is reached up to the standard '06 length.

Since standard '06 cases are used with shortened standard '06 dies no further dies are needed and no action alteration is needed. These are other attributes that gives great flexibility to the cartridge for use with cast bullets IF a correct twist is used and a correct length action is used. If the shorter medium length 2.8" action is used you are pretty much stuck with that.

Larry Gibson

[runfiverun]

the correct length mauser action would be preferable and the long action is almost [shrug]
the no brainer.
I built my X57 Ackley on a win [270] push feed action, and my 25-06 on a BRNO mauser action.
both feed like they are the right action for the round.

I had a 6mm rem on a rem-700 short action and it fed just fine too, but even I could see the mag was a tick too short for the round.
which sucked as the rifle abhorred anything under 75 grs of bullet weight.
there is a line between being workable and flexible.

[MBTcustom]

So far so good.
I have sunk the barreled action into the stock with scrapers and my trusty oil lamp. She is perfect stem to stern. Even though there are no pillars or bedding compound yet, the action slides into the stock and would almost stay there when the rifle was inverted if not for the weight of the barrel.
I'm almost done sanding the stock. Once that's OK, I'm going to bed the action, and the pillars, stamp the nomenclature on the barrel, and finish building.
She is definitely barrel heavy, so I'm going to have to weight the stock.
Attachment 103203