My Secret to HV Cast

[Bass Ackward]

HV Cast always stirs a debate and I wanted to ask myself why? My experience comes down to experience at pushing soft lead to do more before I harden. That's how I found it. Now how does "my" thought process work?

I have explained the wine glass theory many times. The harder you push, the greater the volume and the faster you go, the higher the pitch or vibration. That's our barrel. At cast velocities, pressure is low and vibration is minimized, so cast accuracy is easy and available across a wide spectrum. Well guess what. It's the same with jacketed. It's just that we don't waste jacketed for this purpose. And most casters don't waste lead when they have jacketed available. Because of this many develop a false RPM limit theory. So, both grounds go unexplored which would make ALL of this easier to understand.

With jacketed we all pretty much realize the our barrel vibrates and we tune the load to exit the barrel at the same point in this cycle. Then we learn that if we fire at a higher or slower rate and warm our barrel that our groups are gonna change probably for the worse, but sometimes better. I find the EXACT same with cast. No difference. Except that we have another variable to account for here. Lube and bullet hardness work hand in hand to control friction and thus the oscillation rate of my barrel. The difference in my thought process between jacketed and cast is 180 degrees opposite.

With jacketed I don't have to concern myself with my bullet and I just strive to get consistent ignition and barrel times to produce good accuracy. With cast, I must think of my bullet and I tune the barrel oscillation to the limit my bullet will withstand. There are a whole host of tricks here that do that and EVERY .... SINGLE .... ONE are designed to control pressure. Not RPMs.

The faster the twist rate, the more resistance the bullet will have to forward motion. The heavier the bullet, the more resistance to forward motion. The smaller the case capacity the faster pressure is going to come up. All of these will raise pressure and lower the options available for top end velocity for cast. Jacketed guys knew this for years. So when they wanted more velocity than a 30/30 could produce, they built a larger case to elongate the pressure curve. In my mind, I do the same. I know that everyone here knows this. What I am trying to show is how I approach it so you can understand my thought processes. RPMs for me are simply a coincidence that as velocity goes up, so do RPMS. Just like the sun coming up every day.

There are three ways to shoot cast. First, is shooting cast at low pressure with fast powders. Pressure rises immediately and begins to drop so the bullet coasts on out. That causes less barrel vibration as it travels out the tube.

The next method I used to list last and that is to mold hard and simply raise the pressure to what the bullet will withstand. Match the hardness to the pressure. But the problem there is that logic only gets you so far if you can't reach the next harmonic node. You reach a limit. Your accuracy doesn't, so you say, RPMs got me when it was really barrel vibration or bullet deformation that stopped you. Harmonics simply made it more difficult.

The third way is to shoot softer cast at the same pressures as in the first method, but to bring the pressure curve up slowly. The exact same logic used with larger case capacities for jacketed. This is the key step. If you have shot cast using methods one and two and believe in them wholeheartedly, then you will have difficulty with this thought process. This is where the game is won or lost. You learn to use lube and hardness together to .... tune "THE BARREL" to the load. Sometimes, the key can be to go to a SOFTER metal to tune friction and bring the barrel to the load.

Sometimes you may not have enough drive area from the lands to do this. That can be too short of rifling or too few of rifling. TOO wide of rifling can be just as much an impediment to forward motion as too fast of a twist. Sometimes your barrel may just not have the interior finish to do this. So I have guns that do put lower limits on me. By that I mean, I can only go so soft before the game ends and I don't have a wide enough window with which to operate with. Then I have to change variables and maybe go to a lighter bullet yet.

To be continued:

[dubber123]

Interesting read, I'm just getting into cast for rifles, (started about 5 years ago), and immediately saw it isn't the same game as pistol shooting with cast. Alot of your findings may take some of the mystery out of it for me.

[Bret4207]

Bass- Ever play with the German Mauser stepped barrels? The steps were to reduce vibration. Might be an addition to your discussion. Good read, keep going. You make sense.

[BruceB]

I do believe I'll go make some popcorn to watch the show with.....

[Bass Ackward]

So in some cases, by going to a harder bullet, you increase the initial pressure dynamics enough that pressure comes up quicker and as a result even the harder bullet CAN NOT be driven any faster or has to have pressure / velocity cut to go back to the last accuracy node. When this happens, you can say, RPMs got me and give up. When it was really pressure and the rate that that pressure came up that really got got you.

Now thee are a whole lot of techniques that can be used to alter pressure rate increase and we all know them, but one is using a lighter primer to slow the burn rate just enough in some cases to allow a softer bullet to accelerate with a softer curve that the base stays intact.

A BIG ONE that people seldom think of is bullet quality. Molding base pour bullets always means that the chances for defects which weaken the bullet occur in the base. The longer and smaller the diameter, the harder the bullet is to mold well. Taking a bullet from a larger bore diameter and sizing it down using a base first method keeps the base square as these voids are crush filled under controlled conditions. As a results in a stronger bullet to take increased pressure from say, a faster twist rate than even the hardest molded bullet molded base pour will endure. So I get less fliers to contend with having stronger and better balanced bullets as a result.

So the list of steps that I take for accuracy is different based upon caliber, gun type, bullet design, pressure rate (small cases vs larger ones) etc. But if you mold poor quality bullets in the base area especially, you are toast and will get a flier at a lower RPM than someone else. If your rifling height is a factor, learn to live with it. Or if you have pits, you may need a harder bullet that will limit top end. Your RPM level will be lower than the next guys. So while you can take load data from the first step and with only a minor powder charge adjustment, make it shoot well, you can't do that as you go on up.

You must strive to learn your rifle and work around the the limitations that " it " dictates to you. Or .... learn how to take steps to work around things that are limiting you and improve your chances for success. Think of how to cut or elongate pressure. Whether or not that is improving bore smoothing or dimensions. Or getting a better lube. If you do not want to change technique or play with humteen variables, then you are limited to the first two options and the accuracy limitations that go along with those. The RPM Monster will have gotten you.

The real limiter to cast? Bullet lube. It changes characteristics based upon temperature. SO if you NEED lube to work the balance magic, you will be constantly changing the balance as temperatures raises or lowers. The Best cast bullet accuracy at higher than cast bullet velocities will always be at higher temps because loads worked up in that environment will have thinner lube that allows the bullet to deal with it better. (Catch that Pat?) Lube always acts as a fouling meaning that it can be good right up until it sizes down a bullet causing it to strip. So while the bullet is getting more lube between it and the bore (which some people believe is a good thing if you are a seal theorist) you actually lesson the bullets top end capability.

BIG KEY POINT: If you look at lube as a sealant, you will always accept a lower velocity (RPM limit)threshold than someone who doesn't.

So RPMs eventually gets everybody in the end, to include me. Whether that is 40,000 RPMs with 14 BHN, PB bullets in a handgun. Or 200,000 in a rifle which I have not been able to beat .... yet. I do far better with HV in warmer weather. Often when I quote velocity, that fact is not always mentioned. but because I refuse to heat up my barrel to abuse my rifles throat, I must learn how to deal with lube as the limiting factor. I don't have any problems with lead until it starts to melt in air which occurs somewhere between 3200 and 3500 fps depending on meplat size and humidity levels.


OK. Right or wrong, now you understand .... where I am coming from on several key points over the years. While I can't prove my theories, my RPM level says that there must be something to them. When I .... preach a point, you must understand my entire train of thought to derive benefit from what I am telling you or my advice is useless. My techniques for doing this are too numerous to list here and change all the time.

The real enemy to cast is ALWAYS pressure and the real OBSTACLE is ALWAYS bullet lube that alters friction (changed by temperature) which alters harmonics. And as fouling causes RPM failure and stripping at lower levels because of it. My thinking 180 degrees out from jacketed to altering harmonics with bullet hardness and lube viscosity to work accurately within the twist rate limitation (RPM) of my load widens my chances for finding success at higher velocities. A PIA for some, and a definite disadvantage to jacketed, but it can be done. Once understood, "I believe" that this understanding helps me achieve higher velocities with softer lead at handgun levels and everywhere from that point right on up. Which is why I always beat and dislike that 1,422 hardness chart as well. (false limiter)

So for me, how long you have been shooting cast or how good of a reloader you are means little, to simplify it down to RPMs barriers or lube sealers or hardness charts eliminates options for improvement and accepts barriers that reinforces stereotypes.

[Bass Ackward]

So .... if you at least understand my theory, you can then realize that the best way to to build a cast unfriendly gun would be to take a small bore diameter. Put a fast twist to it. Use a small for bore (underbore) case capacity. Have a larger diameter throat that would need a large bullet for good alignment. Then harden your bullet so it took more pressure to size it. Have a long throat that required a 2lb cruise missile. And try to shoot fast powders. That's as bad as it can get. Sound familiar to anyone? (6.5X55 Carlina)

Now to make it better, I would cut a small diameter throat that was short so I could shoot as light a bullet as possible. It would be easier to mold well too. Then increase the case capacity to just slightly overbore and use as slow a powders as I needed. This setup would allow me to see exactly WHERE the RPM level was and not a false pressure level that I blamed on RPMs. But still I could then slow my twist rate even more so pressure wasn't killing me. (6.5-06)

[Larry Gibson]

"So RPMs eventually gets everybody in the end, to include me"

Well thank you Bass!

Now if you will go back and read and understand what I and others have said; with NORMAL cast bullet loads it is RPMs that will dictate the level at which accuracy deteriorates. Now Joe sent me an email still stating he can "hit the target" at HV. Well so what...so can I and so can every one else. The point is "How well you hit the target" i.e. ACCURACY. Don't get offended here when I call all the steps you describe as essoteric. They are far more detailed steps than most cast bullet shooters want to do. Now I have done all those essoteric steps over the years and most recently with your specific assistance and help using your LBT bullet in a very accurate 30-06 with a 1-10" twist barrel. I even used your bullets that you cast with your lube. I ran them every which way you said to, tried every powder you said to, tried the primers you said to and set the AOL as you said to and you know what? Accuracy still decreased at the RPM threshold. With the medium (3031, 4895) and slow powders (4831, RL19, RL22, 4350) the best accuracy was always in the 1700-1900 fps range. That is 122,400 to 136,800 RPM out of that 1-10" twist '06.

I will say I did get some "accuracy" at 2400-2600 fps ((2500 fps = 180,000 RPM out of the 10" twist barrel) but it was not the best accuracy that bullet was capable of in that rifle. Using 5 shot groups at 100 yards at 1872 fps (around 134,000 rpm) your LBT bullet shot right at 1" with 4895. With RL19, RL22, H4831SC and IMR4350 with velocities in the 2400-2600 fps range accuracy ran from 2.5" to 4.75" groups. I could not duplicate the 2.5" group consistantly and that load ran groups from 2.5 to 4.7". Over 2600 fps, with all powders but RL19, accuracy went to over 8" groups. Again I am not saying you can not get ANY accuracy at HV but am saying that you will not get the best accuracy. It is RPM that limits the accuracy because it accentuates to defects in the bullets. That causes yaw and pitching in the bullet. Both of those are detrimental to best accuracy.

When someone posts; "Gee my 311291 out of my '06 shoots really good at 1800 fps or so giving me 1 1/2" to 2" groups at 100 yards. I want to use it for hunting and am using ACWWs with 50% lead added. I've tried 4350 and RL19 will 4831 help? When I bump it up to 2400 fps the groups open to 4 to 6". How come? You can talk barrel nodes, lubes and different alloys all you want and that guys is still not going to get his 311291 to shoot 1 1/2 - 2" groups at 100 yards at 2400 fps no matter what kind of essoteric tricks he tries. It is the increased RPM that has caused the loss of accuracy period and "got him" as you so rightly state.

Larry Gibson.

[Pat I.]

That was an excellent and thourough explanation but there's a few questions I have to ask. First and foremost what do you consider accuracy? Not based on one group but at the very least the aggregate of four five shot groups at 100 yds. What velocity are you talking about being able to achieve? What calibers and twists have you tried it in successfully.

I'm not a lube sealant theorist and do believe lube quality, quantity,and consistancy can make or break a load but think I could show you a lot of examples where reasonable temperature
fluctuations didn't make that much of a difference.

Thanks, Pat

[felix]

Pat, I think what accuracy in this conversation is more like how round the groups are, and are they what is realistically expected for the trials. We must always keep in mind how the boolits stay together at rotation. Those which are mo'betta' balanced at the RPM threshold will out-round those groups which are not made with boolits other than not perfectly round (consistent) at the target. This has to do with how the boolits accelerate, and how much the boolits are obturated on the back, sides and front inclusively. So, you can see that lube plays a role here as well, because we have to consider how the sides obturate. ... felix

[crabo]

An obvious question, but I assume by RPMs you are talking revolutions per minute and the faster the bullet is going the more rpms? And I also assume that twist would affect rpms, although you can't change that easily.

[felix]

You got it! RPM's are a thing we can measure, but the other boolit variables which make the RPM as a practical indicator are the make-it or break-it functions at the target. Taking the air resistance out of the equation, like shooting in outer space, the twist itself would be very much out of the question to what we are trying to get at. Unfortunately, down here we have to deal with RPM because that is what destroys a boolit by pulling it apart, and, unfortunately again, RPM is needed to make the boolit to even get to the target. For example, you can over-twist a genuine BR bullet (full target bench rest gun bullet) by quite a bit before you can notice a strong degrade in terms of varmint applications. The softer the boolits, including the jacket material thickness, as in intentional varmint bullets, the more those bullets will get out of kilter and become more seriously range dependent. ... felix

[Pat I.]

Pat, I think what accuracy in this conversation is more like how round the groups are, and are they what is realistically expected for the trials. We must always keep in mind how the boolits stay together at rotation. Those which are mo'betta' balanced at the RPM threshold will out-round those groups which are not made with boolits other than not perfectly round (consistent) at the target. This has to do with how the boolits accelerate, and how much the boolits are obturated on the back, sides and front inclusively. So, you can see that lube plays a role here as well, because we have to consider how the sides obturate. ... felix

Actually all I'm asking is how accurate are the high velocity loads BA shoots. I'd be a lot happier with a 1750 fps one inch group than a 2600 fps 6 inch group. Velocity for velocities sake alone is useless. I have to give this a good read because I just breezed through it but it's nice to discuss without trying to piss each other off.

[Char-Gar]

How come in all of this theory, nobody has posted a pic of groups? If not a pic at least some measurments, load details etc. etc. etc.. It is all just talk until sombody can produce targets to back up his theory.

IN all of this talk about what can be done, I would like to see what has been done. It is just all dueling theories until somebody goes to the range and offers proof..

[45 2.1]

How come in all of this theory, nobody has posted a pic of groups? If not a pic at least some measurments, load details etc. etc. etc.. It is all just talk until sombody can produce targets to back up his theory.

IN all of this talk about what can be done, I would like to see what has been done. It is just all dueling theories until somebody goes to the range and offers proof..

You wanted a picture. Here is what happens when you fit a boolit correctly.

[felix]

Charles, looks like Bob has produced a heart shaped group. Yeah, you gotta' have heart to play. ... felix

[Char-Gar]

Bolbby that is a good start..now show me some more shot on the same day with the same load.

[Pat I.]

I'll post pictures of the only targets I have. The group target is from an August post I wrote on the CBA forum about barrel cooling and I just copied and pasted it here. The other ones from earlier this month. These aren't hand picked or anything and the barrel's only been on the gun for a couple of months so they're all I have.

The group target's four 100 yd. five shot groups plus a five shot warm up in the lower left using my Shilen barreled 17 twist 30x47 bench gun. Cases are formed Rem. 300 Savage with a .327 loaded diameter to run in the .328 chamber neck, WW primers, 39.5 grs of VV135, .960 long LBT 170 gr .5 radius ogive bullet tapered in a .310x1 1/2 degree incl. die to match the throat and sized .3097. Bullet has one .070 lube groove plus the one over the check. Alloy is oven treated WW with a dash of tin and a splash of shot 35 BNH. I'm pretty sure I've gotten the flyers under control by loosening up my grip on the gun and mixing a little transmission fluid into the LBT lube to soften it up. Chronographed velocity is 2575

The second target from this month is a 200 yd score target which explains only 4 shots per bull. Since it's a score target they're not four shot groups but one shot on each bull four times around the target. Everything's the same as above except this time I used a .890 long 155 gr LBT bullet with the .5 radius ogive, upped the charge to 40 grs, and because the gun was acting up in the cold weather I was shooting in removed the lube from the groove and just left it over the check. Velocity is 2650.

I've proven to myself that you can shoot fast using a slow twist barrel but even though I've tried I can't get it to work with a fast twist. I have 10, 11, 13, 14, and this 17 twist 30 caliber barrels fitted to this gun and have found that starting at around 1850 fps for the ten twist you can gain about 100 fps for 1 every one turn reduction in twist rate and still maintain good accuracy but if you try pushing them much faster the groups start opening up.

I really don't have an agenda and if I could have gotten a bullet to go fast with a 10 twist I would have done it to help beat the wind but in my case and with what I know I couldn't make it work wiithout losing accuracy.

[Larry Gibson]

How come in all of this theory, nobody has posted a pic of groups? If not a pic at least some measurments, load details etc. etc. etc.. It is all just talk until sombody can produce targets to back up his theory.

IN all of this talk about what can be done, I would like to see what has been done. It is just all dueling theories until somebody goes to the range and offers proof..

Charger

I mentioned the cartridge the bullet, the powder and the group sizes in my post to Bass.

Let me show you a very atypical series of groups that show best accuracy and the detrimental efects of RPM. Now in case Bass wants to critisize the bullet or alloy or lube or the powder or the primer let me say this very same bullet with all the same other componants shoots just as well at pretty much the same RPM in my Palma 14" twist .308 but at a much higher velocity of 2520 fps.

Here's a photo of four 10 shot targets shot with my 308 CBC cartridge (shown to the left of the 308 Win case) at 100 yards. The rifle is a M1916 Oviedo that I put a new 2 groove '06 barrel on. The rifle has been converted to cock on closing and has a lock time comparable to a M70. It also sports a civilian trigger set at 2 lbs. The rifle has a 4X Weaver on it. The bullet used is 311291 cast of 1-3 (line- range lead) and WQ'd out of the mould. BHN is about 25. The bullets are not pre sorted but are only inspected visually for defects. GCs are Hornady's and the lube is Javelina. Powder is 1 gr increasing increments of milsurp 4895 with a dacron filler from 25 gr through 28 gr. The top left group with 25 gr is 1.64" and is indicative of what this load in this rifle will shoot all day long. The velocity/RPM is 1840/ 132,533. Top right group with 26 gr is 2.31". Velocity/RPM is 1972/142,040. The bottom left group is with 27 gr and is 2.3" Velocity/RPM is 2047/147,442. The bottom right group is where accuracy REALLY goes south and is with 28 gr. Velocity/RPM is 2182/157,166. Note the bottom left hole and top right hole of that group are out of round and indicate severe wobble. Now I have pushed that bullet faster in the CBC rifle with slower powders (RL19 and H4831SC but the figurse remain pretty constant. Accuracy goes south above 135,000 RPM. As with Pat I> I have .308s in 10, 12 and 14" twist barrels and I find the exact same thing he does.

Now the photo I've posted is a very typical string of groups that most all of you will identify with having shot a .30 cal with a 1-10" twist. As Bass said; RPM get's ya.

Larry Gibson

[Pat I.]

Larry,

Your case doesn't look much different than my 30x47, about 30-30 capacity, and if you ever get the chance you should really try some 135 in it followed by 748. Jacketed Hunter Class Shooters use 135 pretty regularly in the 30x47 but I couldn't find any when I got this thing put together so tried 3031, 332, 335, 4895, Benchmark, and Varget but it didn't come alive until I got hold of some 135. I've since bought some 748 but haven't had a chance to try it yet. Hopefully it'll work as well because it's cheaper and a lot easier to find.

[45 2.1]

Bolbby that is a good start..now show me some more shot on the same day with the same load.

If you look at the boolit weight and type, you'll see that its meant to hunt with, and the charge is meant to hunt heavy game. Not exactly something you want to sit and shoot all afternoon. The object was to get first shot hits, anywhere anytime, not an excersize in manageing the rifle for heat. I will say that the mechanical accuracy holds up, but the body doesn't nearly as well under the pounding you get from these loads. Is this pursuit a trap or benchrest match or something else? If you want to shoot CBA matches, they offer quite a few, but thats something i've done and am not interested in anymore. More interesting things occupy me these days.

H.M. Pope said the 4570 wouldn't shoot. He was wrong on that score.