Testing the 30XCB

[cainttype]

I have followed Larry Gibson's writings for some time,they are well presented without any bull dust,yet he is regularly attacked by people who can see anything in his work,except what he has written.Why he bothers to persevere on this site is beyond me.If he is driven off,it will be a great loss to the Cast Boolits Forum.
Mike H.

I agree completely. Both Frank and Larry are real assets to this forum, and their contributions to their respective pursuits make this forum a much more interesting place.
There have been many much more heated discussions than Larry and Frank's debate over the definition of "bearing surface", which was nothing more than an arguement over semantics, which drew absolutely no threats of disciplinary action. Oddly enough, Larry is accused of violating the TOS and receives a ban (temporary I hope) after he was warned to cease and desist (WHICH HE DID) or desciplinary action would be taken.
I view suggesting that Larry's "ill behaviour" had persisted for days (false, the only possible objectionable posts seemed to occur on the 28th), and referring to his posts as "arrogant", "downright trollish", and "disgusting" was an larger violation of the TOS than anything that transpired previously in this thread...yet, that goes unmentioned.
I'm hoping test results comparing the XCB along side Frank's design at high velocity will be posted here by both Bjorn AND Larry. That info would benefit all who are interested in the ongoing XCB/High Velocity experiments.

[detox]

An accurate rifle and cartridge combination should not be fussy. My first time out at range with my Ardito style tapered bullet shot better than 30XCB and Frank's bullet. So far I will say both Frank's and the 30XCB are both equal to each other, but not as consistently accurate as my new Accurate Mold bullet and matching throat...this was an instant success in the accuracy department. Perhaps the 30XCB just needs less taper to be more consistant at higher velocity (.309 diameter, 1 degree included taper)... this style throat should shoot jacketed well also.

Here is my new bullet BTW.

[35 shooter]

detox, i'm curious, at what speed did you shoot the 31200G on your range trip?

[Nrut]

Group size and number of shots per group would be nice also..
I take it you are shooting .308?

You should start your own thread about what you are doing instead of posting here..

This thread is about "Testing the 30XCB"....

Not other bullets or cartridges..

Just a suggestion...

[Bjornb]

Group size and number of shots per group would be nice also..
I take it you are shooting .308?

You should start your own thread about what you are doing instead of posting here..

This thread is about "Testing the 30XCB"....

Not other bullets or cartridges..

Just a suggestion...

As much as I appreciate debate about HV shooting, I have to say I agree with Nrut here. This thread has been derailed numerous times for numerous reasons, and it would be nice to keep it on track. As much as Detox would love to discuss his throating schemes, the XCB reamer is pretty much perfect for its purpose the way it is and no mods will be done to my knowledge.

For those who follow the twists and turns of HV shooting, there's going to be a new barrel on the scene shortly. Goodsteel has in his possession a new Shilen match grade 17" twist barrel for Bertha, to be installed and head spaced when I can get my butt down to Arkansas. We have decided to take the XCB concept all the way out to 30-06 length this time, so I guess this will be a 30x63 XCB.

The purpose of this re-barreling is to see where the upper velocity limit of cast bullets lies, and/or where accuracy falls off. Tim is modifying his breech seater for this new barrel.

[MBTcustom]

Indeed.
I fully support anyone else doing their experiments with HV shooting and posting their thoughts on how it works, but when it comes to the XCB, I designed it with an eye on science rather than art, and so far, our efforts have yeilded something that no one else seems to be able to bring themselves to include with their claims of success:

Groups (always 10 shots).
Chronograph readings.
Load data.
Repeatable examples of these.
Recorded at various ranges, at various altitudes, by various shooters, at opposite ends of this continent and everywhere in between.
I'm happy with the design, and no rifle built by me in the twist rate we have demonstrated works, fails to deliver these results on demand by anyone.
The XCB bullets work in other platforms very well, but nestled in cases prepped the way we do, and plugged into an MBT rifle built correctly for the purpose, it's a forgone conclusion.
I have done my homework, listened to the right people (like Larry Gibson) approached the concept with honest science and logical thought, and the results are there for anyone to see.
Not read about. Not think about and imagine.
See with their own two eyes, again and again, for month after month in threads like this one.

I understand that BjornB recently met Larry Gibson in Arizona and they spent time at the range......shooting. At 3000FPS. Exactly what has been claimed has been witnessed and demonstrated.

That's how we do it. Some call it an affront. I call it fun.

Now, I have no doubt that there are other ways to get HV with accuracy, and I would encourage anyone to do what I have done here (with considerable help from Larry Gibson, BjornB, sgt.mike, Lovelife, Glenn Larson from White Label Lubes, Al Nelson from NOE bullet molds, and many many others.)
The XCB is just my attempt to bring people together to demonstrate A WAY to get to HV with accuracy that anyone can have. A benchmark. One time in the history of this forum where it was done, done correctly, and done often enough by enough people, and explained so candidly that it's validity is irrefutable. Just one way that you can get there every time.
I am hoping that this solid infromation will be used as a springboard to develope more methods, and to attempt to set an example of the right way to prove a method using this new medium of comunication: the internet forum.
I still hope for success.

[DR Owl Creek]

Group size and number of shots per group would be nice also..
I take it you are shooting .308?

You should start your own thread about what you are doing instead of posting here..

This thread is about "Testing the 30XCB"....

Not other bullets or cartridges..

Just a suggestion...

This seem like the best idea to me too. That would eliminate most, if not all, of the background noise and distractions. IMO.

Dave

[detox]

detox, i'm curious, at what speed did you shoot the 31200G on your range trip?

Following Larry's advice I kept velocity between 1666-1944fps in a 1-10 twist barrel.

This Ardito style taper is nothing new. It just requires rethoating your barrel to match bullets taper exactly (I did not bump). I seat the bullets long so that only .170" of bullet is held by case neck. Most of bullet is surrounded by throat of chamber (within .0005 leade clearance). When bolt closes the bullet is pressed firmly against rifling to help center the bullet before takeoff. The first load I tried was 21grs. of 4759 for a velocity of 1900fps in 1/10 barrel....consistent groups under 1 inch.

I know lots of you guys have seen Eagans brochure before. I found it very interesting. I hope the link works. If not just copy and paste link below (highlight, right click, copy, paste)

castpics.net/subsite/HistMolds/Eagan.pdf

castpics.net/subsite/HistMolds/Eagan.pdf

[detox]

Tom at AccurateMolds can cut any concentric taper you desire and on the fly. The .75 degree per side rifling marks on my bullet match perfectly.

LBT can do this also

[35 shooter]

detox that's good shooting for sure and an interesting design, but i don't think i've ever seen that style boolit shot with accuracy at much over 2200 fps. I may be wrong.
The guys on this thread however are shooting the xcb with very good accuracy at amazing speeds and with a variety of powders. I think it has aquited itself very well and know of no other design doing anything like it at these speeds.

I don't think anyone knows at this point how truly accurate this boolit can be (accurate enough for sure) as the emphasis has been on speed with accuracy and has accomplished that with gold stars! When the speed limit with accuracy has been found, i'm sure there will be some back tracking to find to the most "accurate" loads as far as target shooting is concerned. Only a handfull of guys are doing this at this time and it will take time.
The results from the testing so far are nothing short of amazing to me.

This design is so new and already done so well, it deserves it's own thread to continue with all emphasis on the xcb design till all avenues with it have been exhausted. It will take time, but is moving quickly.
I anxiously await the 35xcb just from the results of the 30xcb so far, but that, i'm sure will be in another thread also as it should be.

[Bjornb]

The first (and so far only) 35 XCB rifle is in the mail from Goodsteel to my FFL as we speak. We have named her the Eskimo Queen (she sports an Arctic Camo stock from McMillan). As soon as the rifle has been to the range I'll start a new thread. Tim already shot some one hole groups with her, and I'll be feeding her RCBS 200 FN bullets until the 35 XCB molds become available.

[Hannibal]

Please post results when available. Inquiring minds gotta know!

[runfiverun]

it'll work...


the boolit detox shows is somewhat modified from the 165-A which I have been creeping up on 2500 fps with in my 10 twist 308, and is the boolit I will be directly comparing to the 30 xcb boolit in my xcb rifle.

I'm still putting things together for the rifle [which now wears a new scope] and will be getting a new recoil pad while I search for a heavier stock.
this rifle is beating me down from the bench, but is for sure murder on the rock chucks.
I made a 300 yd head shot across an open canyon using the speer 125 TnT hp bullet while resting the rifle on a sage brush.

for the first time ever I named a rifle, this one got nick-named 'GOOFY'.
but it shut's everyone up when they look at the targets.
I gotta get some more brass though, the 12 pieces I made are about toast.

[detox]

One neat thing I like about a separate throating reamer like the Uni-Throater is that throat taper can be recut when throat erosion becomes a problem. So it is best to cut throat a little short (short COAL) to begin with so you can recut throat deeper in future and what ever angle you desire.

[Larry Gibson]

Testing the NOE309-169-FN at HV

Earlierin this thread I stated;“I conjecture (the 309-169-FN) ELCO bullet may indeed dowell to perhaps 2500+ fps in a 14" twist XCB but doubt it will performwell above that, especially in the 2600 - 2900+ fps range. But then, onlytesting will really give the answer.” I was then thinking of Bjorn conducting the test since he was getting or had the mould. I also offered to conduct a test of this particular bullet and a forum member was gracious enough to send me his4 cavity mould so I could cast some of these bullets and test them. Thus I conducted the following test:

Since the design of this NOE 309-169-FN is thought by some to be adequate for use at HV I confined my testing to right around 2500 fps upwards of 2800+ fps. I decided to test the NOE 309-169-FN against the designed for HV shooting NOE 310-165-FN (XCB) and the Lyman 311466 Loverin design which is also reputed and proven to be an excellent performer at HV. Thus with the 3 bullets to compare in this test I had 4 cavity moulds for all of them. The bullets were all cast on the same day of the same alloy of linotype. A Lyman Mag-20 bottom poor was used and the alloy temp was maintained at 715 – 730 degrees. The alloy was melted, fluxed with beeswax and “cooked” at that temperature for 30 minutes when it was again fluxed before casting began. The moulds were pre-heated and 4 casting done with each before any bullets were kept. The sprue was cut as soon as it hardened and the bullets were WQ’d immediately. The BHN ran 26 – 27 after 72 hours.

After aging for 72+ hours the bullets were inspected for any visible defect. Any visible defect was cause for rejection. The rejection rate was very small and was about equal with each bullet. The bullets were then weight sorted with a lot selected for each bullet at+/- .2 gr. The 311466 weighed 150.2 gr,the 30 XCBs weighed 154.1 gr and the ELCO bullets 158.5 gr. The ELCO bullets dropped at .3125 – 313, the XCBs dropped at .311 as did the 311466s.

Hornady GC were used (same box) and initially seated and crimped on with the Lyman GC seater on a 450 lubrasizer using a .311 H&I die. The bullets were all sized and lubed (2500+) in the Lyman 450 lubrasizer. Those bullets (30 XCB and ELCO’s) to be used in the 30x60 XCB were then push sized through a Lee .310 sizer.

I decided to test all three bullets in the.308W Palma rifle with 14” twist barrel 27.6” long. Researching my records I found 2 loads that performed equally well for both the 311466 and the 30 XCB that gave velocities of 2500 +/- fps.
A Forster COAX press was used for loading both cartridges. All the Winchester test cases (both the .308W and 30x60 XCB are Winchester cases match prepped and fire formed) were NS’d the same using a Redding Bushing die. The necks were inside uniformed with a Lyman 31 M die for a .002” neck tension. Primers used were WLRs.

The two powders chosen for use with all three bullets in the Palma .308W were AA4350 and H4831SC. A charge of 47.2 gr AA4350 has proven accurate at 2500+ fps with both the XCB and 311466 bullets as has 48 gr ofH4831SC. Those two loads were chosen to test each bullet with.

Of the several .308W rifles I have the Palma rifle has the longest throat which allowed the ELCO bullet to be seated with the top of the GC at the base of the neck. The other two bullets had a bit of the GC up into the case neck also.The bullets were all seated to just bump the leade.

Attachment 140247

[Larry Gibson]

In the 30x60 XCB rifle (Dawn with 16” twistbarrel 31” long) I decided to push the ELCO bullet from 2500 fps or so to 2800+fps using AA4350 as the powder as it has proven accuracy potential with both the 311466 and the 30 XCB bullets in that same velocity range. I loaded up a 10shot control test with the 30 XCB of 46 gr and then loaded four 10 shot test strings with the ELCO bullet using 46, 48, 50 and 52 gr of AA4350.

Thus for the purpose of this test I went to great length to ensure everything was identical except for the design of the bullet.

Conditions at the range were pretty good this morning except for the wind. It was a nice bright day with the temp running 68 – 78 during the testing. However the wind was not good coming out of 10 – 1 o’clock switching back and forth with irregularity. It was running 6 –10 mph and gusting to 12 -13 mph. The barrel was cleaned between test groups and allowed to cool. 3 - 5 foulers were then fire to determine zero and to season the bore. The 1^sttest was with the 311466 bullet over 47.2 gr AA4350. After the foulers the 10 shot test stringwent into 1.64” at 2536 fps. The 311466 over 48 gr H4831SC went into 1.67” at 2395 fps. The 30 XCB over 47.2 gr AA4350 went into 1.68” at 2563 fps and over 48gr H4831SC went into 1.65” at 2421 fps. As we see on the target that is pretty consistent performance, given the wind conditions, between the 2 bullets.

Switching back up to the fouler target the ELCO bullet put 2 shots high and 2 shots low way out of the expected impactarea with the starting load of 47.2 gr AA4350. Dropping down to the bottom left diamond for a test string one shot wasoff paper and the other 4 shots encroached on the other groups so I decided toput up another target with a single diamond in the middle for the test string.

Attachment 140248

[Larry Gibson]

Attachment 140249Attachment 140250

Thetest load of 47.2 gr AA4350 managed to keep them on paper with a 13.6” group.The velocity was 2543 fps.The ELCO Bullet should be well stabilized ina 14” twist at that velocity according to the Miller stabilization formula.As we see obvious signs of wobble or thebeginning of instability there is another reason for the inaccuracy.

Thinkingmaybe I was just pushing the ELCO bullet too hard with AA4350 I put anotherfull target up with the aiming diamond in the middle and tested the 48 grH4831SC load.

Attachment 140252

Itappears that at a little more than 100 fps less at 2414 fps the ELCO bulletperformed “better”.The bullet holeshere also indicated excessive bullet wobble in flight so I had some hopes thehigher velocity of the 30 XCB might settle the bullet down.

[Larry Gibson]

Imoved on the test the ELCO bullet in Dawn, my 30x60 XCB rifle.

Attachment 140256


Ifirst shot 3 foulers and then shot the control group using the 30 XCB bulletover the start load of 46 gr AA4350.Aswe see they went into the usual 1.68” group at the expected beginning velocityof 2525 fps.Next up the ELCO bulletover the same 46 gr AA4350 load was again disappointing with 7.75” group.The bullet holes still indicating excessivebullet wobble.
Attachment 140260

[Larry Gibson]

[FONT="Tahoma"]NextI shot the 48 gr AA4350 load.Thevelocity was 2598 fps but accuracy did not essentially improve as the group wasstill large at 7.3”.Moving on to the 50gr load the velocity was 2822 fps and accuracy was worse at 9” for the 9 shotsthat were on the target.One shot missedthe target.We can see the readilyapparent bullet instability, particularly with the low left shot of the lasttest group.I did not fire theremaining test string of 52 gr AA4350.[COLOR=#000000]

Attachment 140262


Inthe earlier post in this thread I conjectured the ELCO (309-169-FN) bullet mightdo well upward of 2500+ fps in a 14” twist barrel.I conjectured so because the ELCO bulletappeared to have some attributes that should lend itself to reasonable accuracyperformance at 23500 fps +/-.So far Ihave proven myself wrong on that conjecture.

Ialso conjectured the ELCO bullet would not do well at the higher velocitylevels in any twist barrel.Iconjectured that because this bullet was not designed for those higher level velocitiesand had some design attributes that would prevent it from giving reasonableaccuracy at the velocity level of 2600 – 2800+ fps.

LarryGibson

[MBTcustom]

It's got to be that long nose that's causing the problem. It's just not supported.
I see the 311466 actually did best in this test which I hate to see, but I understand why. Even though the 311466 isn't shaped very well for long destance flight, it has all the earmarks of an extremely effective HV cast bullet.
It has a bunch of bearing surface
It has very little nose protruding.
It has very small lube grooves.

Very informative test Larry. I learn more from looking at the results of tests like these than in 100 pages of forum. The pictures alone tell the tale.

The fact is, you just can't design a cast bullet to look like a jacketed bullet. It will not work as well. Cast is as different from jacketed as water is from stone.
When I was a kid, there was an engineer that worked with my dad who showed me how to build a switch barrel potato cannon. This cannon would shoot paint balls, golf balls, tennis balls, pop cans, and even water balloons.
I was most intrigued by the water balloons. The guy showed me how to shoot them, but told me that I had to keep the speed very low, or the balloons would pop as they left the barrel (sound familiar?).
Well, I wanted to shoot water balloons a long loooooong ways out there, so I started experimenting with lubes, and how full I made the balloons (projectile hardness), wads, and charges of ether.
I ended up making bigger and bigger cannons, till I had a pressure chamber made of the largest schedule 40 PVC pipe I could find. I ended up shooting water balloons over 200 yards!
That exercise drilled into my brain certain principles of shooting soft, easily damaged projectiles, and I still defer to that knowledge when designing cast bullets and ways to shoot them. What I remember discovering, was that the further I got from the ideal projectile shape, the worse it did at an exponential rate.