Testing the 30XCB

[MBTcustom]

That's right Frank. Breach seating gives gentler torsional strain on the nose of the bullet, allowing it to exit the barrel without having a lot of pent up torsion to release on it's way to the target (that's assuming your nose was short enough to not get permanently bent by that torsion (ie: slump) before it made it 2" down the barrel, so it could actually have some torsion to release upon exit). Paper patching does the same thing.
That's how Bjorn was able to use my breach seater to shoot 3100 FPS and maintain less than 1.5" groups with my 30XCB design.

Shooting from fixed ammunition is a whole different ball of wax, and is what I designed the XCB bullet to accomplish.
My efforts were concentrated on making a plug and play bullet that could bring accurate high velocity shooting home to the members of this forum. Since that is the reality of what I created, the XCB designs will also impress at low velocity, they will also impress when breach seated, they will also be less effected by lube changes, seating depth, alloy choice, propellant choice, and they will do all of this at longer ranges as well.
I designed based on my own experience, but I also humbly asked for advice from more experienced members of this forum, chief among whom was none other than Larry Gibson. He corroborated my theories, and added experience to them. I trusted his advice (although I did spend the money required to verify it) and he was spot on every time without fail.
The XCB project is seasoned with Larry Gibson's expertise through and through, and we are all succeeding because of it.
I have developed a "plug and play" path to get our members to their goals be it accuracy, HV, or both, and I have tried very very hard to solve every problem in a way that doesn't require special equipment, or special loading techniques. The XCB system is impressive to say the least, but the bullet mold alone is the most scientifically advanced cast bullet design of this century, and it shows. It has been used to obtain quick results in:
300WinMag
30-06
30X60XCB
30XCB
308 Winchester
7.62X51 NATO
30-30 Winchester
30 Herrett

The 30XCB bullet shoots. ​Just as Larry Gibson said it would. Larry's advice is spot on and is best to be headed, whether dealing with bullet design or shooting dangerous loads in an 8mm Mauser.

Larry and I go back a long way with him trying to prove me wrong about a lot of different things. Should I trust what he says regarding anything? With all the wrong assertions that he's made in this thread regarding the bullet I designed ................ any wonder?

Nope. No wonder at all from my perspective. Looks to me like he was right back then, and he was right again this time.

Now, please excuse me. I have to go read my daughter a bedtime story. It should be good. It's called "the emperors new clothes".

[frnkeore]

Tim,
I'm supprize that you would do this:

"The 30XCB bullet [I]shoots. ​Just as Larry Gibson said it would. Larry's advice is spot on and is best to be headed, whether dealing with bullet design or shooting dangerous loads in an 8mm Mauser."

Larry and I go back a long way with him trying to prove me wrong about a lot of different things. Should I trust what he says regarding anything? With all the wrong assertions that he's made in this thread regarding the bullet I designed ................ any wonder?


Are you accusing me of suggesting that I did, indeed suggested a dangerous load for a 8x57, 185 gr load? In responce to a PM you sent me a while back, I also told you of this and suggested that you check it out.

To clear my name, I'd suggest that Larry, please repost the strain gage results for the 18.0 gr loading with a 185 gr bullet, that I suggested and that he tested, that was, indeed a low pressure load and didn't have any pressure spikes, at all.

A completely safe load!

Frank

[Bjornb]

If I could, I'd like to suggest that this line of argumentation is cut short right here. Frank, your name has not been sullied. You and Larry had a back-and- forth argument a few pages back that resulted in Larry's suspension from this thread for 10 days. I'm not going to argue the merits of this suspension; everyone involved can guess what I think about it.

Then in post # 714 you bring up some old, obscure argument between you and Larry, about 296 powder in 8x57 loads. Is this your way of bringing peace to this thread?

Your bullet was tested by 2 shooters (myself and Larry), with pictures and very little commentary. Nobody tried to sabotage your design in any way; the tests were fair. You objected to Larry's bullets' casting size, that's your right. The other shooters on this forum can draw their own conclusions as to the value of our testing.

I suggest that we all take a deep breath and get this thread back on track.

[cainttype]

Earlier today, before sunrise, I looked for but couldn't find this thread. In view of the past thread closures (and outright thread disappearances) associated with the entire HV subject anytime slower twist rates or "XCB" is part of the subject matter, I feared this thread may have joined the victim list.
There is an obvious intent by some on this forum to silence anyone attempting to openly post and/or discuss the results of the HV testing being done by the XCB/slower-twist guys. I view any thread drift resulting in angry exchanges as a potential excuse to eliminate these threads by those opposed to discussing and/or exploring the validity of these theories openly.

Perhaps concentrating on this thread's intent, testing the XCBs, and ignoring all other chatter will help keep this thread alive.
The data collected here should be archived permanently. I'm hoping that we can all benefit from it in the future.

[MBTcustom]

Allow me to share my afternoon with the board:

Today I had planned to get up early, skip church like a total heathen, and go shoot the Felix rifle (my personal XCB testbed).
Unfortunately, it was raining cats and dogs (again) Working around all the rain has been difficult this year to say the least.
When my plans were thwarted, I tore into my Browning 1886 and slicked it up a little and did a trigger job that dropped the pull from 6 pounds down to 3.5 (MUUUUUCH better!)
It finally stopped raining about noon, and I decided to finish up the 1886 and head out anyway.
I was loading up the truck and my daughter drew my attention to the FISH IN OUR FRONT YARD.
Seriously. You know you've had a little rain when you see this:
Attachment 140980
Attachment 140981
Hmmmm. More fertilizer I suppose.

I got to the range with all my gear, and the only thing I forgot to bring was my screwdrivers which was no problem because I didn't end up needing them.
Here you can see the 1886 and my press, powder measure, and an assortment of powders I brought along.
Attachment 140982
And here's Felix hanging out in the cool dry shade, being cool and kickin it MBT style. You will notice the Chronograpgh tripod is set up in standing water (but no fish thank God).
Attachment 140983
Attachment 140984

I started with the old standby: a case full of WC867. Kind of an appetizer.
Speed was 2150 (yawn) and group size was about 1.25" at 100 yards for ten shots. Nice way to start a range session.
Bullets were the XCB design, cast of house alloy, sized to .3097
Lube was White Label 2700+
Hornady gas checks
Attachment 140985

Next, I fired ten identical loads but instead of House alloy, the bullet material was linotype. This didn't fare as well, and rendered a group size of about 1.75"
Attachment 140986

That was fun, but I really wanted to see how this 30" barrel would play with Leverevolution powder, so I quit playing and got down to the HV stuff.

First group was shot with the linotype bullets over 37 grains of LvR and produced a 1.375 group. Speed was 2425 average:
Attachment 140987

Then I went back to the House alloy but upped the charge to 38 grains. Speed was 2500 and accuracy was sub MOA except for that one at the lower left that I shot just as the guy next to me let go with a muzzle break. I'll take it as is, but that was a called flier.
Attachment 140988

I upped the charge to 40 grains, used House alloy, and got this at 2550 average:
Attachment 140989

Time was at a premium at this point because they were going to close the range in a matter of 30 minutes, so I upped the charge to 41 grains of LvR, loaded up another 20 shots of house alloy, and gave it what for. At this point the barrel was starting to really cook, and I was getting heat mirage off the barrel making the target dance a little. Speeds were from 2650 to 2700 which is right at the RPM threshold.
This was the first string:

[MBTcustom]

Attachment 140990

And this was the second:
Attachment 140991

These last two groups were identical loads. I can't explain what happened, but I was all over it like a cheap suit, and those were not called fliers.
I don't think I had crossed the RPM threshold either. I was right on top of it, but this isn't what usually happens when you cross the RPMTH.
My best guess is that the barrel was producing mirage that was making the target appear in a different spot than it actually was, or the barrel was hot enough to start stringing (it was visibly hot. You could see the heat waves rolling off it).

When I got back to the shop, I carefully scoped the barrel from both ends and found exactly what I want to see: A smoky looking bore and a nice little star on the crown.

[MBTcustom]

Honestly, I'm going to check out that 38gr charge a little more thouroughly.
It was done with house alloy which is cheap and effective, and I call it House alloy because I like to make everything out of it if possible. It's a very versatile alloy that is comprised of 95.6% lead, 2.2% tin, and 2.2% Antimony.
It's one of the most consistent alloys I have ever cast with.
Air cooled on the bench it renders a hardness of 14BHN, and water dropped it goes as high as 27BHN after a fortnight of aging.
These bullets were water dropped and aged about 2-3 months?

If this alloy/charge will hold less than 1.5 MOA out to 300 yards, then I think I might have a candidate for a long toss on a deer. (not with this rifle of course).

I didn't get a chance to run a similar workup on H414, but that's a project for another day.

[HotGuns]

Alright...I'm convinced. I have a perfectly good Rem. 700 that I willing to use to rebarrel or do whatever it takes. How do I get a mold? Like right now. Reamer? I want to go play with this thing.

[MBTcustom]

Alright...I'm convinced. I have a perfectly good Rem. 700 that I willing to use to rebarrel or do whatever it takes. How do I get a mold? Like right now. Reamer? I want to go play with this thing.

Well the mold is available from NOE.
The barrels are available from Shilen (and Krieger and Brux etc etc).
As for getting things put together, PM me and we'll work something out.

[HotGuns]

Yo Tim I will do that. What twist are you using? I've got several .30 cal barrels laying around.

[MBTcustom]

depends what you what cartridge you want to use and where its comfort zone is with cast lead.
If I had chambered 308, I would have gone 1-13
this is a 30XCB chamber so I went 1-14
1-16 worked really well for Larry Gibson in 30X60 and Bjorn went the full 30-06 and chose 1-17.

In this same thread of thought, I would submit to you that the classic twist rate for 30-30 Winchester was 1-12.

Now, if you go to jacketed shooting philosophy, all the bullets get 30-50% longer so all the twist rates get much faster accordingly.

[Larry Gibson]

HotGuns

I would heartily suggest you have Tim put a 14" twist barrel of minimum 26" length on your M700 and chamber it in 30 XCB. Tim can also easily adjust a set of standard '06 dies for forming and loading. I suggest a Bushing die to NS with but a standard '06 NS die can be shortened also. The cases are easy to make but neck turning is a must. The 30 XCB is the optimum choice for excellent performance up through 2700 fps as you've seen posted here. Above 2700 fps other things begin to happen to the bullet caused by additional acceleration, heat and increased psi necessary that create additional problems. The 30 XCB in a 26" + barrel with 14" twist is and easy way to actually get such accuracy at these velocities.

Larry Gibson

[Bjornb]

Agree with Larry. What Tim has created here is a plug and play system where you order a setup from any number of combinations, knowing in advance what you'll get in the end.

My target rifle will now get a 1-17 twist barrel, plus it will be reamed all the way to 30x63 XCB (30-06). At that point most of the combinations will have been tried, even though it would have been very beneficial to the project if the owners of the two 1-12 rifles would have joined in the testing. But sometimes you've gotta be happy with what you've got.

[HotGuns]

Thanks for the advice gentlemen. Any thoughts on a .308 chamber with a 1/8 twist? Would that be too fast ya think? I have a bunch of .30 cal barrel blanks but most of them are 1/8 for the numerous Blackout builds that I do.

[MBTcustom]

There's a common saying: "I have an app for that".
I'm going to start saying "I have a sticky for that". LOL!

In this case, here it is:
http://castboolits.gunloads.com/show...velocity-chart

[dragon813gt]

Make it an App and your problem is solved.

[HotGuns]

Thanks. Looks like the 1/14 might be the way to go for the .308, which I have a gazillion cases of. If that'll spin a cast lead bullet at 2700 FPS, with any accuracy, this could be a wonderful deer whacking machine.

[cainttype]

Thanks for the advice gentlemen. Any thoughts on a .308 chamber with a 1/8 twist? Would that be too fast ya think? I have a bunch of .30 cal barrel blanks but most of them are 1/8 for the numerous Blackout builds that I do.

Your results using the XCB bullet in a 1-in-8" twist would be interesting extra data here.
There are some here (and some no longer here) that claim to be able to reach similar performance levels as those being posted by the XCB testers, even in mil-surps with fast twist rates (velocities at 2500-3000fps with less than 2 MOA, to 300yds). Perhaps you can be the first to join the trials with a detailed report of your own results.
I'd be very interested in your findings with the XCB projectile in the faster twist, and I'm sure there are others that would feel the same.

[HotGuns]

Now off to another subject...has anyone tried this bullet at subsonic velocity's to be shot through a suppressor?

That might be an interesting setup.

[MBTcustom]

Now off to another subject...has anyone tried this bullet at subsonic velocity's to be shot through a suppressor?

That might be an interesting setup.

Dang Bob, what took you so long? I was starting to think you turned over a new leaf. You have an incorrigible aversion to muzzle blast.


If you want to try some, I'll hook you up. Bullets are cheap and I've got a bunch of them.