SLOW Twists and FAST Casts Using CUSTOM Barrels...Results, Please?

[Hannibal]

(Insert the sound of a low, long whistle).

THAT'S going to be a tough act to follow! Thank you for sharing, Larry. And well done Sir!

[MBTcustom]

That's firmly breaking 3050FPS with fixed ammo, and a standard cast bullet with pictures, load data and a demonstration of progress to boot, but only two months after I shipped the rifle.

Larry, we are lucky to have your input on this forum. In the quest for HV, post #167 on this thread is the best that has ever been posted in this forum IMHO, and bravo to you for sticking to it and making it happen, just as you said you would.

You accepted a rifle build for free, but paid me after the fact.
You claimed 2" groups but you shot 1.5
You claimed 2800fps, but shot 3000.
You theorized that RPM is the biggest limiter of HV shooting with cast, but you paid the price to demontrate and prove in here in open forum.

In short, your actions speak louder than any words you will or have typed on this forum.
Thank you sir!!!!

[mnewcomb59]

I've gotta say, I personally believe that RPM can be interchanged with stability factor. Stability factor is a calculation that gives you a number you hope is near 1.5.

1.5 is the bare minimum gyroscopic stability needed to keep a projectile of a given length, weight and caliber from tumbling.

Less than 1.5 means the bullet will yaw. It may shoot decent for a certain distance, then after that distance groups will open up non-linearly.

Anything over 1.5 means your bullet has more RPM than it needs. When a bullet is way over spun, it will not go to sleep after its apex and start falling point first like a good football toss. Instead, it will maintain its same angle it was launched on (point slightly up) , eventually showing up as oval holes at long range.

Pretty much if you have any choice, pick your heaviest bullet weight you will shoot, figure out what twist length gives around 1.5-1.8 stability factor, then try to find a rifle with that twist.

As bullet weight goes higher and higher for caliber, lead bullets will struggle. First of all, they will need a faster twist, which is harder on the driving bands. Second, the first driving band of your 1.5 inch long 240 grain 30 caliber bullet will have to bite and torque the whole long, heavy bullet. In reality, the first driving band would probably skid, causing deformation and loss in accuracy even if the gas check caught the leading.

I think people trying to get 3000 fps+ would be better served by experimenting with low to middle sectional density bullets. The first driving band can easily bite and torque a 125 grain 30 cal into rotation compared to the front driving band on a 30 cal biting and torquing a 240 grain, for example.

Here are my personal results in my slow 30" twist 357 Rossi rifle. This gun is giving me really good accuracy (1 MOA) between 1800 and 2100 fps plain base. I sort bullets for good bases and tumble lube. 17.4 Lil Gun is also MOA, and the 18.6 grain (Brian Pearce data) load shows promise. I bet the vertical stringing was because my scout scope and eyeball alignment. Can't wait to do some shooting this spring. I hope to find the 18.6 grain (2000 fps) load just as accurate as 16 and 17.4


I would have shoot lead at 3000 fps in this 30" twist to have the same RPM (driving band torque stress) as a 10" twist 9mm at 1000 fps. What does this tell you about 9mm needing harder lead? It has enough twist for subsonic Whelen bullets! This 30" twist at 2000 fps is putting less stress on the driving bands than a 16" twist Ruger Blackhawk at 1100 fps. This 30" twist is so slow that the driving bands hold tight while the lube groove deforms and pumps.

One time I shot some 9 BHN Lee 125-RF at 2100 fps and recovered some bullets. The twist rate is so slow that there was no skidding on the driving bands, but the lube groove was completely swaged out. Also, the bases cupped really deep from the pressure. Accuracy went down to 3-4 MOA, and I suspect off center sprues and the deep base cupping threw off accuracy. No lead in the barrel with that soft alloy at around 2100 fps.

[cainttype]

Thanks for an excellent field report, Larry. I'm looking forward to the extended range testing results.
I'm still kicking around devoting a HBR rifle to cast-only, but I lean towards rechambering to a match 308 Win.. The chamber neck is much tighter than I'm interested in having for the project in it's current 308x48 configuration, but I want to at least run it through some preliminary testing before any final decision is made.
Now... If only I had more time... retirement sounds really great, right about now.

So, Mike... What is the status on your new lead-slinger project?

[swheeler]

Very good Larry! I would say you exceeded your own expectations with DAWN, what's not to love Another 1k of those loads and you can start chasing the rifling and will have a base for answers as to throat erosion some have asked. To go where no one has gone before, you should have been an astronut

[Larry Gibson]

Mike

My retirement goal is to wear out most all of my firearms! I'm working hard at it. I have no idea how I ever found the time to actual work before I retired. Retirement is a full time job!

Larry Gibson

[Larry Gibson]

Cainttype

All of my 10, 12 and 14" twist HV load development was done with the .308W. The 30x57 has basically the same capacity as the .308W but has the longer '06/30-30 neck. The 30x57 is a wildcat and Tim chambers it using very tight specs, especially the neck and throat designed for the 30 XCB bullet). It is not a difficult case to make. However the .308W with a match chamber and tight neck in a 26"+ length barrel with a 14" twist will also do nicely. Might have to throat it a bit so the GC doesn't get below the case neck though but I've not had to do that with the 5 different .308W/7.62 NATO chambers I've used the 30 XCB in. I've had very good results in the 2600 - 2700 fps range in my .308W Palma rifle with 27.6" barrel with a 14" twist.

Larry Gibson

[cainttype]

Larry, I'm going to have to wring out the 24" tube (1-14" twist) the rifle has before rebarrelling is a serious propostion. If it behaves well, as is (I think it will), I may opt for the 308 chamber to get rid of some case forming issues for convenience.
The short action Rem 700 action limits choices, but I've considered incorporating a longer neck (similar to the 30x57) in the existing chamber. It's currently nothing more than a 308 Win reamer short-chambered by 3mm, so adding almost 1/8" of neck is a definite possibility.
I have to admit that if the rifle shoots any cast nearly as well as jacketed, I'll be pretty happy. I'm not anticipating anything near the speeds you are accurately achieving with "Dawn", but I will eventually find my limitations with the smaller case capacity...In good time.

[1johnlb]

Well, I decided to join in on the slow twist chase for speed. I've picked up a new stock and a shilen 1in14", 30" long in 308 win to fit my savage 10fp. I'm still in the fire forming stage but just wanted to post some of my results.

I obviously tried to begin with the 30 xcb but had fit problems that set it way deeper than I would like, so I tried some of Larry Gibson ' s loads with them and the Lee 155 ' s and the NOE 129 sp on the first 100 cases of winchester brass with nothing special to write about. At this point I went through my 30 cal designs to find a better fit for fire forming the next 100 cases of PMC. I decided to try the lyman 311299 next because it fit the bore of the muzzle perfect and seated perfectly in the case when touching the lands. The 299s were originally tumble lubed and gc ' ed with Hornady checks cast from 2 parts ww and 1 part monotype, sized at 311 and later on pan lubed with 2500+. Before loading I weight sorted then loaded starting with h4831sc and accurate 4350. S&B standard primers. Shot at 115 yds.

While I know that I'm setting no speed records with the 299s but believe that I will be able to push the upper limits of a 200 gr projectile with good accuracy. This to date is my most accurate cast groups and when all is fully refined, I hope to see if it holds out to 200 meters and repeatable.


All the 4831sc loads left unburned powder with about 90 to 95% case fill.


I had 2 called flyers with the 41 gr load, the bulls eye hit was the first were I set the trigger to early. Throwing them and the cold barrel yielded me a .6 even group. Wow that's my best cast group, ever. The barrel ran remarkably cool with the 4831, never more than just warm to the touch.


I had 1 pulled flyer and 2 rounds from a cold barrel. The 6th shot cold barrel was from being distracted.


Here's a pic of the new girl in town, ain't she purdy. Now to go push em a little harder. I'll post velocities when my chrony comes in, still waiting on the funds.

[Larry Gibson]

1johnlb

As I mentioned to cainttype some .308Ws are to short throated for the 30 XCB bullet with the GC being seated below the case neck. The shortest throated .308E chamber of the 5 I have allows the top of the GC to be right at the case neck/shoulder junction. That hasn't caused any problems. If your rifle's throat is shorter then a touch with a throating reamer would solve the problem. The 30 XCB is designed for the longer '06/30-30 neck and it optimizes bullet weight with bearing surface and no bore riding nose. It is the best design if you want to optimize your barrels capability upwards of 2600 - 2700 fps.

Some pundits have continually complained the slower 14" twist isn't useable with "heavier" cast bullets. Not only have I proved them incorrect numerous times but now you are to with the 311299! I was able to push my own 311299 upwards of 2400 fps in my 14" twist .308W Palma rifle. After that as you push the bullet harder the minimal bearing surface, large lube groove and long bore riding nose work against maintaining accuracy.

Well done BTW!

Larry Gibson

[1johnlb]

Thanks Larry, if I can get any were close to 2400 I'll be happy. But then I'm happy with those groups regardless. If those will hold moa out to 200, I'll be even happier.

I wasn't very clear before and didn't give the xcb, Lee 155, and NOE 129 a good start by weight sorting any of those and what I experienced was very likely due to that fact. I haven't given up on any of them.

My 30 xcb seated at 2.53 oal, which put the check at the shoulder/ body junction. I'm not likely to change the throat, shooting the 299 that well. I also have a Savage 110 long action that I'm considering putting a Hart's barrel on. At this point I'm thinking about letting Tim chamber it for the /06 and ream it for the xcb, but unsure for the moment of what twist. I'll be watching closely for more post from you and others on the progress of the slow twist.

Thanks again Larry and all those taking the time to share their experiences and wisdom on all the accuracy techniques. I for one have learned more on these recent threads than I ever knew.

[dtknowles]

Larry, nice work. Thanks for sharing.

Tim

[tomme boy]

1john. Goodsteel has a copy of the print that Shilen uses for the 308W. We got it to check over my barrel for me. Might want to PM him to help find out what size to use for your bullets.

I have over 3500 rounds of cast through my Shilen 1-10 twist. And I am still able to hold less than 0.5" groups with 168gr Hornady AMAX bullets. I have over 600 rounds of Jacketed through the barrel on top of what I have shot cast also. So that might give some a clue as to how long the barrels will last.

Tim can say as to what it looked like. As he scoped it. Tim???

[Larry Gibson]

As I said in my last post on the results from the 30x60 using the 16" twist rifle Dawn, the next step would be to conduct a longer range test of the 49.5 gr LeveRevolution load to test for linear group dispersion. I conducted that test this morning at 200 and 300 yards. The load was the same; 49.5 gr LvR with a Dacron filler (1/3 gr). The bullet was the 30 XCB cast of linotype and WQ'd. Velocity runs right at 3000 fps with the linotype bullet sized at .310 and lubed with 2500+.

Looking at the 100 yard groups of 49 and 49.5 gr LvR I shot the other day and posted in the last report we see basically 1.4 - 1.5 moa between the two of them.

Attachment 134931Attachment 134932

Thus for linear expansion/dispersion of the groups at 200 and 300 yards we should expect about the same moa of 1.4 - 1.5. I was hoping to beat the wind this morning but it was not to be. There was a blustering non consistent 4 - 8 mph wind coming from 1 - 2 o'clock. Knowing the wind would only get worse I shot the 300 yard target first. The 10 shot group was 4.5" even with the wind. That is 1.5 moa.

Attachment 134933

I then put a target at 200 yards and measured the wind.......it was still coming out of 1 - 2 o'clock but had picked up running from 7 - 10 and gusting to 12 mph. It also would just die momentarily. I shot the 10 shots trying to gues when the wind was consistent but with no real wind indicators other than the feel of it at the bench I didn't do to well. That nice 5 shot group to the right is the result of the wind dying just as I pulled the trigger! None the less the over all group is right at 3" for again, 1.5 moa. There is an eleventh shot in there for you bean counters; I took 3 foulers with me and fired 2 before the test. I decided to shoot the last fouler into the 200 yard group. It is the high left shot of that five shot group on the right from when the wind died.

Attachment 134934

This test demonstrated the linear group expansion/dispersion is consistent at 1.5 moa for 100, 200 and 300 yards. That is exactly what we were looking for. This is an excellent load and will probably be my go to HV load for Dawn. I will be further testing this load at 400 - 600 yards in the near future. However, I have one other Powder to test with the linotype 30 XCBs. The testing continues but the RPM Threshold is well proven. What is also well proven is how to shoot real HV with cast bullets accurately if that is your goal.

Larry Gibson

[Yodogsandman]

Outstanding! Thanks for sharing your every step and your reasoning behind it!

[cainttype]

Larry, thanks for the update. It's more than just a little bit interesting to watch the results of the efforts, time, and money that all of you gentlemen have invested to put your ideas into practice in order to test them in this spectrum of slinging lead downrange.
Hopefully your results with "Dawn" won't discourage others from posting any results they achieve with rebarrels and/or rebores while experimenting to find the HV potential of their own combos...Let's face it, 3000fps while maining linear accuracy to 300 yds is a pretty hard act to follow.
Mike (IIRC) commented awhile back that his definition of HV with cast would be matching factory jacketed speeds...seems reasonable enough for mid-sized cartridges in medium-to-large bore diameters, especially now.
I've never felt the need to pursue velocities that high, having always been happy with speeds that ranged from the mid-teens to 2500fps. The work you have all been doing has given rise to an new interest in higher speeds that has me thinking... so it is entirely possible that I'll put the blame on all of you in the future.

[MBTcustom]

Outstanding results Larry. There is no better reward a craftsman can receive than to see the things he has made being used for the purpose they were intended to serve.

Cainttype: I don't know why people would be discouraged? In the past HV cast shooting has been a dark art that can only be taught by people who can't teach, and can only be learned by those who can't learn. Larry has been trying to tell people how to cut to the chase for years, and has demonstrated how to do just that. If someone wants to do as he has done, but pick and choose what parts they want to listen to, then they certainly will get discouraged very quickly.
However, if they follow basic techniques for loading precision ammo, use excellent alloy, and use the correct twist barrel, it's pretty much plug and play.

I would like to illustrate my point with the fact that I have a shipping ticket here with a date of 1-21-15. That was the date I dropped this rifle in the mail to Larry Gibson. It was a new wildcat cartridge (longer than the 30XCB) and the entire rifle was gone through in my shop. The action was trued, new hinged bottom metal was installed, a brand new barrel was installed, and when he received the rifle, the bedding was redone. For all intents and purposes, Larry started a month and a half ago with a brand new rifle that he had never shot before!!!! That makes a pretty big statement all by itself.

I think more results will be forthcoming this year. I just took in a shipment of slow twist matchgrade barrels today, and I think that at least some of them will be showing up in this thread, or on castboolits. Very interesting times lay ahead!

[cainttype]

Tim, perhaps I wasn't clear.
I meant to welcome everyone experimenting with these non-factory barrels to post their results. I was trying to clarlfy that results with any caliber, and the "HV" trials, others may be engaged in testing would be welcome here.
Obviously there will be interesting experiments resulting in less than 3000 fps, so there's no need to worry if your pet project is not in that realm... The pursuit of matching factory speeds is challenge enough. How you get there is all the fun.
As I have admitted before, anything in the 2500fps range has been HV in my world...That view is changing, although I still spend most of my time with loads in the mid-teens to lower 2000+ range. Using mostly hunting weight rifles, that's often all I'm willing to spend an afternoon pushing lead through.
I believe you are correct, "Very interesting times lay ahead!".

[MBTcustom]

Attachment 134946
hmmmm ....... Look anything like this???

Hmmmm, must have had a trunk monkey with a camera behind me. LOL!

[MBTcustom]

Tim, perhaps I wasn't clear.
I meant to welcome everyone experimenting with these non-factory barrels to post their results. I was trying to clarlfy that results with any caliber, and the "HV" trials, others may be engaged in testing would be welcome here.
Obviously there will be interesting experiments resulting in less than 3000 fps, so there's no need to worry if your pet project is not in that realm... The pursuit of matching factory speeds is challenge enough. How you get there is all the fun.
As I have admitted before, anything in the 2500fps range has been HV in my world...That view is changing, although I still spend most of my time with loads in the mid-teens to lower 2000+ range. Using mostly hunting weight rifles, that's often all I'm willing to spend an afternoon pushing lead through.
I believe you are correct, "Very interesting times lay ahead!".

I really wasn't arguing with anything you said, just wondered why any of this would be discouraging to anyone. This is the clearest path to HV shooting with the most solid results that has ever been posted. I find that to be beyond encouraging!


Larry has put himself in the drivers seat and showed us how to drift. If he can do it, then anyone can do it. It's all been explained very clearly.

Three years ago, I heard tell here on castboolits of how some people claimed to be able to shoot HV with cast, but the path to fruition was like walking through a swamp with wet matches to light the way. I decided I was going to do whatever it took to encourage all the players to shed light on their method and demonstrate it clearly so that others could follow their path. First there was paper patching, and geargnasher footed the bill perfectly with his clear demonstration with the 270 Winchester. Now we have a naked cast bullet matching and surpassing those speeds.
It has been expensive, time consuming, heartbreaking, I have lost more sleep over this issue than I care to admit to, and I have given everything I can possibly give to help anyone who so much as mutters under their breath a claim of HV with accuracy (in fact, you could probably squat the springs in my truck with all the custom rifles, molds, dies, and reloading equipment I have sent to the key players) but the results are worth every bit of it, and now castboolits is the best place on the internet (dare I say in the world) to learn how to do this.
So far, all the evidence shows that slow twist barrels and paper patching seem to be the best ways to get to HV with cast, and thanks to the hard work of forum members like Larry Gibson and Bjornb, we now have a very clearly laid path to that goal for anyone who cares to pursue it.
I'm elated by the progress that has been made by those who have taken the time, and had the courage to demonstrate their claims. The science has cut through the superstition, and the groups tell the tale.
Bravo!