Testing the 30XCB

[detox]

Groups are getting better. Was it the water quenched WW?

I will try posting pictures soon. Five shot groups, five targets, same unedited target. I hate a barrel that walks.





Much like this official target.

[detox]

Goodsteel, Larry,

Sorry if I sounded like a troll. Your 30XCB cartridge/bullet idea is a very good one (the more I think about it). Maybe accuracy is improving because of gradual throat erosion (maybe gun is not broke in) ?

BTW will a Remington Short Action receiver work with this design? Is magazine well long enough? Will 30XCB cartridges chamber easily without modification?

[Larry Gibson]

Or maybe accuracy is improving because we're learning more about the techniques of casting and loading for these actual high velocities and about the loads needed for accuracy?

Personally I've not found nor been able to measure any appreciable throat erosion in my 30x60 XCB with over 1301 rounds through it as of today. Accuracy between 2600 - 2900+ fps has remained a steady 1 - 1.7 moa with 10 shot groups with the better loads right from the beginning of testing to todays testing. The XCB bullet was designed to fit the neck of the XCB cartridge and the chamber throat. It does that very nicely. However, based on extensive testing of the XCB bullet in my .308W Palma rifle I can't say the angle or length of the throat matters a great deal if at all. The key seems to be fitting the GC inside the case neck (or at least the top of the GC, with the bullet ogive bumping against the leade. We may or may not improve accuracy with a shallower leade angle but I think there are greater forces at work affecting accuracy at the psi's and velocities we are using (2400 - 2900+ fps).

The OAL of the 30x60 loaded with the 30 XCB bullet is 2.908 which may be a bit too long for the short M700 magazine. The boys with the 30x57 XCB can give a better oal for that cartridge.

Larry Gibson

[Larry Gibson]

Made it to the range this morning to beat the wind (managed that) and heat (didn't manage that so well as it was 85 - 94 degrees while I was shooting) to test the 30x60 XCB load with 41 gr H4895 XCB bullet load at 300 yards. In the F class match you have 22 minutes to shoot 2 sighters and 20 shots for record in 22 minutes. I wasn't sure of the exact 300 yard zero and knew that the two sighters out of the clean barrel (same load but with 2 fully lubed 311466 bullets) would not hit to group. The 1st XCB bullet with the same load has always then gone to group at 100 yards so it would also be interesting to see if it did at 300 yards (it did). Thus I chose to just shoot for group tracking the location on target of each shot. I would then overlay the center of the group on the center of the "X" of the 300/600 F class target center for "score".

The first 10 shots went into 3.75" (very close to moa at 300 yards) but shooting 20 shots in 20 minutes causes additional problems. In the morning heat of probably 85 degrees the barrel heated up rapidly and stayed hot. I was giving right at 50 seconds to 1 minute per shot and finished the 20 record shots right at 19 and a half minutes. Mirage was very bad coming off the barrel and even with the extended scope tube the aiming point was dancing around like an ice cube in a hot skillet. I called shot 14 low and away because of the mirage and that's where it went. Shooter fatigue and concentration can also falter over such a long string being shot in such a short time. As I was getting ready to load shot #16 I was interrupted by a shooter wanting to post targets. He was gracious allowing me to finish the string though. However, it interrupted my cadence and concentration and I failed to slide the rifle back forward on the rest. The rifle felt funny as I was settling in for the shot but being rushed I didn't stop and check why. As soon as the shot went off and I saw and felt the different recoil I knew why; sure enough the shot went high like they always do when the rifle isn't pushed back forward to the stop on the rest. No matter, it and the called #14 shot were still for record and they still counted. Total group size for the 20 shots was 6.6". Overlaying the target on the center produced a score of 184-2X.


Attachment 141684 Attachment 141685

Certainly not going to set any F Class records but it would have gotten every ones attention at the match, especially since the cast bullets were moving along at 2765 fps. Also considering the entire 20 shots were minute of deer/antelope if not coyote I found it somewhat satisfying. Then, also considering the first 10 shots at 3.75", it makes that load minute of rock chuck and prairie dog! Additionally I do think I'll do a bit more 20 shot group testing at 300 yards with several other powers a bit slower than H4895; Varget, RL19, H4831SC and perhaps RL22.

Larry Gibson

[CJR]

Bjornb,

I have not read every post on this very interesting thread. Could you summarize how you now reload your CB loads; i.e. brand dies used, body full-sizing or not, neck-sizing or not, partial neck-sizing or not, neck turning or not, CB runout measurement or not, cartridge fit-up to chamber, CB sizing or not, CB weight variation, M-die use or not, crimping or not, etc.

Keep up the good work! Advancing the "state-of-the-art" is never easy.

Best regards,

CJR

[Bjornb]

Bjornb,

I have not read every post on this very interesting thread. Could you summarize how you now reload your CB loads; i.e. brand dies used, body full-sizing or not, neck-sizing or not, partial neck-sizing or not, neck turning or not, CB runout measurement or not, cartridge fit-up to chamber, CB sizing or not, CB weight variation, M-die use or not, crimping or not, etc.

Keep up the good work! Advancing the "state-of-the-art" is never easy.

Best regards,

CJR

Hi CJR,
with the XCB rifles Goodsteel has made reloading very easy. I only speak for myself here, and there's certainly more than one way to skin this cat. Others shooters use different methods, but here's how I have standardized my reloading:

With fired brass I only deprime and tumble clean in walnut media. No sizing of any kind. The chamber is tight enough that I don't see the need for any neck sizing. The rifle takes a .310 cast bullet (the XCB), and this size, combined with an unsized neck, gives a tight slip fit. (If shooting jacketed the necks need to be sized for the smaller .308 bullets, this is done with a modified Lee collet die). About every 5 loadings or so the necks need to be re-turned (they were originally turned to .0125" thickness). I'm currently experimenting with turning them down to .011 and expect having to size the necks after firing with the thinner necks.

I have an excellent runout gauge on loan from Goodsteel, I usually check every 8-10 finished rounds, both neck and bullet ogive.

I have been weight sorting my bullets from the start, but with better casting techniques and the recent addition of a mould thermometer I hope to build enough confidence to skip this rather time consuming step in the process.

I don't use any kind of neck expander; with the RCBS competition seating die the case neck and bullet are mated inside a sliding bushing, and the combination of chamfered case mouth (Lyman VLD chamfering tool) and the radius of the gas check on the bullet heel is sufficient to enter the bullet in the neck with no issues.

I never crimp. I also seat the bullets several thousands long, letting the bolt do the final seating into the lands.

The methods written above are a work in progress; I have used various dies, expanders, bushings, etc., and will most likely try other tools as they become available. I try to listen to other shooters and pick up any tips they are willing to share.

[Larry Gibson]

I'm NSing my 30x60 XCB cases with a Redding '06 bushing die shortened for the 30x60 case. I use a bushing .002 smaller than the fired case neck diameter for .002 neck tension. I've accuracy tested from zero neck tension to .004 neck tension and .002 seems to be the best giving "field" serviceable handling characteristics to the loaded ammo.

Larry Gibson

[MBTcustom]

My process for reloading the XCB is as follows:

Cut off the brass to the correct legth +.020
Set back the shoulder of 30-06 brass with a 358 Winchester FL die set to length with a dummy cartridge.
FL size with the customized 30-06 die to create 30XCB
Anneal the necks
Run through the sizer a second time
Trim to length
Neck turn so a tight slip fit is achieved with a seated .3100 cast bullet.
Expand the necks with a custom MBT neck flaring punch
Prime, load, and fireform.
Deprime and wash in vinegar for 30 minutes, rinse thoroughly, and tumble in crushed walnut with two tablespoons of flake carnauba wax added (bought from randyrat) for 24 hours.

Now the brass is ready to be reloaded and shot. Accuracy seems to improve on the third firing BTW.
In order to reload, I have a set of three dies that I use for the purpose:
A 308 FL die I set high and use to neck size and deprime.
A 308 seater die I use to hold my neck flaring punch.
and a custom inline seater die I made from an actual section of barrel steel. It is reamed with the XCB reamer, and carfully bored to allow a very precise slip fit of a 30XCB bullet through the barrel and into the brass. The brass fits the die perfectly because it was fireformed to a chamber exactly like the one in the reloading die. The die has a fine adjustment knurled rings that I set for the exact seating depth I require.

Before using these tools, I use an OAL gauge of my own design (very similar to the one offered by hornady) to find the exact seating depth where the bullet touches the lands. One this measurment is taken and written down, I begin my reload as follows:

Neck size with the 308 FL die
Flare with the custom punch (exactly enough to swallow the GC and no more)
Prime, and charge the brass
Plug bullets into the necks
Run them up into the MBT seater and seat the bullets by hand with the punch.
Wipe away any lube on the nose of the bullets.
Shoot.

If anyone is interested in the process used to cast the XCB bullets, it can be found in my thread entitled "consistency applied" in the main cast bullets section.
If this is way past where you are at this present time in your reloading, and you need to take a step back and work your way up, check out the thread I wrote in the main cast bullets section entitled "Just a few tips for new rifle casters" in the sticky section.
If you want to know why I use only slow twist barrels for the XCB project, check out the stickys in the main cast bullet section written by Larry Gibson dealing with the RPM threshold.
If you want to read more about the XCB project, there are a few noteworthy threads over on the NOE website (pick up a mold or two while you're there! LOL!)

[detox]

Taper bumped 30XCB to match my .310 x 1.5 included taper throat. I need a matching nose punch to prevent deforming soft WW nose when removing bullet from taper die. Bullets where cast using Lawrence Magnum Birdshot alloy, gas checks installed and sized .310, and then taper bumped. Next I will heat treat in oven @480 degrees and water quench to make extra hard. These will be shot from a Shilen 1/10 twist barrel. Caliber is 308 Winchester. Maybe I can reach speeds of 2600 with good accuracy and 1/10 fast twist barrel.


BTW I purchased two 25lbs bags of Eagle brand Magnum Birdshot from Rotometals and two 25lbs bags of Graphite Coated Lawrence Brand Magnum Birdshot directly from Lawrence. I casted a few bullets from each different brand and then checked hardness one hour later using SAECO hardness tester. The Eagle tested 9 BHN and the Lawrence tested a harder 13 BHN (more antimony). Of course hardness will increase then seattle after TWO weeks. Water quenching will make them much harder.

Because of the arsenic, use good ventalition when smelting Birdshot. The Eagle brand shot has a very unpleasant oder much like BAD BREATH......STAY AWAY ! The Lawrence brand had no bad oder, but left behind lots of graphite that must be skimmed of. I like the Lawrence Magnum brand best.

I cast these at 800 degree pot temp for best fillout and no wrinkles. Hotter casting (slight frost appearance) temps work best if you are water dropping directly from mold into DEEP 5 gallon bucket.

Taper bumped 30XCB bullet on right. Softer "un" heat treated alloy is very easy to taper and hold shape. Oven Heat treat afterwards.

[detox]

Taper bumping will also eliminate (flatten) that pesky nose whisker when bullet is removed from taper bump die. I used a blank 30 caliber PTG die, .310 x 1.5 included taper throat reamer, and shortened Lee 30 caliber sizing punch.

http://www.midwayusa.com/product/118...ProductFinding

[detox]

OH YEA! I size and seat gas check nose first thru my RCBS Lubamatic using .310 sizer. After heat treating I lube bullets base first using the larger .311 sizer. Try lubing one band only with LBT soft blue lube.

Here I be....

[detox]

I need to make a punch to remove bullets from taper die. All that is needed is a 4" long .2995 diameter steel rod hollowed on end then filled with JB weld to form to nose. Bullets can be tapped out using any hammer, but I use a small lead filled leather mallet.

[CJR]

Bjornb,

A couple of comments:

1. Just because a case is fired-formed and not resized is no guarantee the case is not "banana-shaped". Banana-shaped cases will "tilt" the CG of the bullet as it is chambered and causes inaccuracy. This has been discussed many times by many people; i.e. McPherson, etc.. Unless the case is checked for a banana-shape you can't be sure. Because banana-shaped cases can't be corrected, they are typically discarded.
2. What do you consider to be acceptable bullet runout?
3. Are you bumping your case shoulder back a 0.001" or 0.002".
4. Using benchrest seating dies is no guarantee you've eliminated bullet runout. I use Forster BR seater dies in a Forster Co-Ax press and will get occasional bullet runout that I then straighten.
5. Many top competitors are using Redding Full Length resizing Type S Bushing dies. The FL resizing minimizes the "banana case body" effect, the bushing diameter sizes allow precise bullet tension, partial neck length resizing allows the unsized portion of the neck to align the round in the chamber, the case shoulder can be precisely "bumped" back, while the forward cylindrical part of the CB can be aligned precisely in the rifling to minimize CG offset and improve accuracy.

Finally the obvious question arises,"How significant is bullet runout?" We know from Harold R. Vaughn's book, "Rifle Accuracy Facts" and Dr. Mann's book , "Flight of the Bullet....... (based on 40 yrs of study), that CG displacement (either by casting voids or tilted bullets is VERY significant. Vaughan took a 270 bullet and drilled into the side to displace/offset the CG by ONLY 0.00118". Yes the CG offset is ONLY 0.00118"! The group size at a 100yds was 2.58" or approx. 2.60". BUT if you mark the high runout with an "index mark" and then "index load" the round into the chamber, the groups can be reduced to 1MOA or less. Ahh the Physics of bullet flight. Now let's put this into proper perspective. A typical accurate CB will have its CG about mid-length with the CP slightly forward. So a 0.002" bullet tip runout would give us an CG offset of about 0.001" and a group size at 100yds of about 2.6". Now suppose we flare a case neck to insert a CB and then DO NOT remove the flare. That flared neck, on chambering, can push the CG laterally and cause inaccuracy. The more I work with accurate hivel PPCB, the more I respect the accuracy that goes into making match jacketed bullets. Obviously, if you're happy with 2.5+' groups at 100 yds , this doesn't apply to you.

We also know that James A.(Bud) Welsh, of Kenmore, NY, in 1978 fired a 10 shot group at 200 yds. of 0.521" by seating the bullet (separate from the case) with a special bullet seating guide tool that insured perfect CB placement in the rifling. Nothing like keeping the CG perfectly centered in the rifling. Granted the velocity was lower than hivel, but 0.521" group at 200 yds with a CB is still an outstanding achievement in anyone's book.

Best regards,

CJR

[Bjornb]

Thank you for your comments.

[detox]

Cast bullets are not concentric to begin with. By experimenting, I taper bumped the 30XCB using a .308 x 1.37 per side taper bump die and you can see the irregularities on bullets taper afterwards (high and low spots). Alloy shrinkage causes these irregularities.

Concentric brass, Turning necks, Full length resizing and sizing neck no more than .0015 smaller than cast bullet helps. OH YEA...and taper bumping.

[detox]

PTG has just started selling a new spiral fluted throater that makes throating easier without chatter. I hear a 1 degree per side or 2 degree included taper works great (.310 x 2 degree included taper). These also work great at making a bump die.

I think the 30XCB uses a 1.22 per side taper.

[detox]

I read in the little Blue book "a faster twist will help shoot an "out of balance" bullet more accurately down range".

Today I rebarreled my Remington VS using one of Brownell's short chambered 308 barrels. I used a standard 308 Winchester reamer (.310 diameter x .090 length leade) to set head space, then cut throat using my .310 x 1.5 included throater. I tightened factory receiver (not blueprinted) to barrel. Hopefully it will shoot well without shots walking. I will let you guys know how well it shoots with my tapered 30XCB bullet.

I have another 308 Remington rifle with same throat taper, but deeper leade length for longer heavy bullets.

[GabbyM]

OH YEA! I size and seat gas check nose first thru my RCBS Lubamatic using .310 sizer. After heat treating I lube bullets base first using the larger .311 sizer. Try lubing one band only with LBT soft blue lube.

Here I be....

This question is a bit rudimentary but. What do you use for sizing lube in this first step? Anything I've tried cooks into a glaze when oven heat treating afterwards. I'm not anxious to accept cleaning individual bullets of lube. What I've been doing is using bullet molds that do not require size reduction. Just a bit of qualifying.

[detox]

This question is a bit rudimentary but. What do you use for sizing lube in this first step? Anything I've tried cooks into a glaze when oven heat treating afterwards. I'm not anxious to accept cleaning individual bullets of lube. What I've been doing is using bullet molds that do not require size reduction. Just a bit of qualifying.

I use no lube when sizing and seating GC nose first. No lube helps the bullet and sizer stem to fall freely into hand after being pushed thru.

[Menner]

good day at the range:
I have been following the xcb thread from the start and became very interested in the boolit and while I am not looking for HV cast at this point I have started shooting at a cba match and looking for a boolit that would perform at 100 and 200 yrds and I was looking in the 1800 to 2000 fps range as far as speed goes. I bit the bullet so to speak a few weeks ago and ordered the NOE brass mold ( boy is that a nice mold its the first brass mold I have owned. not the last I think) Now I am not a Master Caster but I do the best I can.
I tried different alloys and the one I settled on for now is a 50/50 pure lead Lino
I water drop it ( I have been told that water dropping lino does nothing but I was water dropping a COWW boolit for another rifle and just kept at when I started casting these so right, wrong or indifferent they are water dropped)
I was getting OK results with this boolit but nothing to jump up and down about.
was heading to the range today and last night I was thinking about something Tim said (if accuracy does not come try seating the boolit out farther ) but I was already at the lands at 2.63 oal well I thought lets let the barrel finish the job and I set it at 2.66 and tried it in my rifle it seated the boolit and the bolt closed so I shot em.
Rifle started life as a Stevens 200 7mm08 it is now a 308Win with a Criterion 26" SS 1 in 10 Barrel and a Eabco varmint stock and a Savage level 2 Rifle Basix trigger and a Sightron 36x scope. ( I have done all the work myself barrel change and free floating the barrel etc.... I am no gunsmith )
24 gr of 3031 was consistent but not the moa I was looking for, but just outside it so that was were I started.
The diamond is 1" point to point all targets are 5 rounds at 100yrds (sorry they are side ways but could not get them to rotate)
bottom diamond on the left target has what looks to be a flier but it is the round I used to see if I could close the bolt on 2.66 oal after that the next 4 are at 7/8" I also loaded another 5 at the same load and that is the top diamond left target and it is a 3/4" group.
the right target is 24.5 and 25 3031 the one on the bottom diamond was the dummy behind the stock round 5 of the string So I will verify next weekend.
I didn't set up the chrony but I figure I am right at 1900fps with the 24gr next week I will set up the chrony to verify and I will put a better backer behind the target for better holes.
Boolit = 30xcb
Alloy= 50/50 Lino and pure lead
sized to .310
Lube= tumble lubed with alox
Powder= 3031

I seem to be on the right track only more holes will tell the story
Stay Tuned
Tony