Maximum velocity with gas checks

[GreenMachine79]

I just finished my first batch of cast bullets ever, they are Lee 430-310-RF. After messing around with the heat of the lead and the heat of the die I was able to cast some decent bullets, a few were a little frothy so I will try to keep things a little cooler next time.

My questions is how does a gas check effect the maxium pressure (velocity) of a cast bullet, my lee hardness tester shows that the bullets have a hardness of 13.4BHN and that the maximum pressure is 17152psi. Is their a rule of thumb for gas checked bullets?

I would like to throw this data into quick load to get a idea of where to start my load at.

[RobS]

A gas check can skew the hardness issue and so does powder selection. An air cooled WW with a smooth bore and correct cylinder throats to bore diameter dimensions can shoot at very close to max levels fairly easily and many have done so at max levels with a plain base bullet even. You shouldn't have any problems with a air cooled bullet that is gas checked. To do this with better success, slow powders are the answer as they have a starting pressure that is less than the faster powders and eases the bullet into the bore so to say. BHN hardness is relevant to what stress you are placing on the bullet and where as the Lee chart gives you a working pressure and an alloy strength it comes down to where the pressures peak in relation to where the bullet is at in the firearm.

An example would be to examine Unique vs 2400. Unique has more energy and builds pressures quicker or more abruptly vs 2400. A person wanting to use Unique at higher velocities will basically be giving bullets a quick kick in the butt right out of the gate where as with 2400 (slower powders) the bullet starts off easier and continues to build pressures/pickup velocities throughout the length of the barrel. The issue with the quicker powders and higher end loads is with the increased pressures at ignition they also push the bullet faster at ignition which puts more stresses on the bullet as it makes it's way into the forcing cone/barrel. This can distort the nose of the bullet (smash it) and front drive band which could even cause skidding. The only way to combat this is to use a harder bullet with those quicker powders if you are after high end loads that is.

As for a GC design it makes it easier to shoot without leading which will increase accuracy generally speaking. A harder bullet may help out if you have shallow rifling as it will be less likely that the bullet will skid as it hits the lands of the barrel, but this is no absolute. Also the same principle applies regarding bullet hardness if you plan on using a quicker powder to light things off. If you don't know shoot some groups and see if your gun is liking what you feed it. :)

[stubert]

I am shooting the same bullet in my Ruger SRH. using 20.3 gr. of 296, mag primer and seated to 1.7" No leading and super accurate, am lubing with orange magic.

[AZ-Stew]

I think what Rob is trying to say is that if your boolits are sized correctly to fit your revolver and properly lubed, merely use the published data for that boolit weight. I don't recall any data that differentiated between checked and plain base boolits of the same weight. I may be wrong here, but I think most of us here disregard Lee's maximum pressure suggestions. The Hodgdon web site shows WW296 and H110 (the same powder) to give mid 1200 to mid 1300 fps with 20 to 22 grains of powder, respectively using a 325 gr GC boolit. I'd call that a pretty potent load.

I see nothing out of the ordinary in your description of your boolits. They appear, from your hardness measurement, to be air-cooled WW. As long as they're cast well without base voids and are completely filled out, they should be accurate and not lead.

As Rob said, ACWW will work well at full velocity even with a plain-base design.

Regards,

Stew

[Bret4207]

Those boolits will harden over he next 3 weeks or so. Hardness isn't the biggest factor, but fresh cast is sifter than aged cast. Some will grow a bit in diameter too, depends on your alloy.

[randyrat]

I just finished my first batch of cast bullets ever, they are Lee 430-310-RF. After messing around with the heat of the lead and the heat of the die I was able to cast some decent bullets, a few were a little frothy so I will try to keep things a little cooler next time.

My questions is how does a gas check effect the maxium pressure (velocity) of a cast bullet, my lee hardness tester shows that the bullets have a hardness of 13.4BHN and that the maximum pressure is 17152psi. Is their a rule of thumb for gas checked bullets?

I would like to throw this data into quick load to get a idea of where to start my load at.
I'm using 180 gr GC ACWW over 11-12 grains of 2400 In a GP100 (357 mag).. I know this is way over the pressure limit that wheel weight air cooled are supposed to handle. Also NO leading. Go figure. I gave up trying to use that pressure guide long ago.
That guide may have some use, but I and many others before me have gone way past the limits that are printed. Some can do it without GCs. Don't over look the importance of your cylinder throats compared with your forcing cone/barrel.

Your guide/rule of thumb is going to be your gun

[GreenMachine79]

These are air cooled wheel weights + 1% tin. It took a little tweaking with the temperature of the pot and die to get it to throw ones that were filled out properly without wrinkles, I culled all of the ones with problems. One other thing is that I can see and feel the seam where the dies are not lined up perfectly, acording to calipers the bullets are up to .005 out of round.

I'm a little confused, I thought that gas checks were meant for higher pressure/velocity, as in full loads. If they are not going to be of any benefit I would rather not go through the trouble and expense of putting them on.

[RobS]

Are you sure they are .005 out of round or is that because of the seam on the bullet. .005 is quit a bit as you could have for example a .452-.457 bullet in readings. GC are a help in approaching higher pressures/velocities but some cartridges can be successfull both ways. You happen to be reloading for one of those. Pushing high end loads out of magnum rifles well then its more in demand to work with GC's. With a GC in your situation it makes for easier travels to the upper ends of the load data.

[RobS]

I also see where you are referring to the mold and mold blocks as dies....................this one makes me laugh a bit as the newbie comes out in you. :)

[missionary5155]

Good morning Welcome about Greenmachine79.... I wore a Picklesuit 71-74 (Armor).
And do not get too concerened about frosted boolits. I have a couple molds that need HOT mix to fill out and so thsy get frosting all over... but they seem to shoot fine.
A perfect boolit is far more usable.
My basic thought is I never use a GC till I have to. As you do your load workup (Never start at MAX) you will find out IF a check is necessary. I load lots of 41 Mag and seldom do I get to Needing a GC. I have a 265 grainer that needs one to push to high speed. But if I can get by without then I sure do not go looking for more work or expense.
Shoot safe and alot !

[GreenMachine79]

I am not measuring on the seam so my .005 reading isnt being effected by the seam itself. If I put my finger nail on the bullet and rotate in the radial direction I can feel a step down of a sevreal thousands as I pass over the seam, if I keep rotating the bullet I can again feel a step down of a couple thousands over the next seam. Since the step downs are in the same direction this indicates to me that the "mold blocks" are not lined up perfectly.

I am going to shoot these bullets and see how they do. The next time I cast I will inspect the blocks, its possible that their is debris or a bur causing the aligment problem. I will also beable to work on my casting technique some more.

On a side not I am a machinist so I have plenty of experience working with calipers. Also forgive me for refering to the molds as dies, it was the first thing that poped into my head, but I think most understand what I am refering to.

[RobS]

Not a biggy, most know what you mean, just a terminology thing. Anyway it could very possibly be a bur or you may have yourself a bit of lead that has made its way onto one or both of the mold blocks face. If you are not lubing the alignment pins and sprue plate that will go along way in helping block alignment and cutting sprues and also reducing galling on the top of the blocks.

[Wayne Smith]

I just finished my first batch of cast bullets ever, they are Lee 430-310-RF. After messing around with the heat of the lead and the heat of the die I was able to cast some decent bullets, a few were a little frothy so I will try to keep things a little cooler next time.

My questions is how does a gas check effect the maxium pressure (velocity) of a cast bullet, my lee hardness tester shows that the bullets have a hardness of 13.4BHN and that the maximum pressure is 17152psi. Is their a rule of thumb for gas checked bullets?

I would like to throw this data into quick load to get a idea of where to start my load at.

Greenmachine, there is a difference between "frothy" and "frosty" - I thought I knew what you ment but did get a chuckle imagining what you wrote. Lacy boolits anyone??

[GabbyM]

I just finished my first batch of cast bullets ever, they are Lee 430-310-RF. After messing around with the heat of the lead and the heat of the die I was able to cast some decent bullets, a few were a little frothy so I will try to keep things a little cooler next time.

My questions is how does a gas check effect the maxium pressure (velocity) of a cast bullet, my lee hardness tester shows that the bullets have a hardness of 13.4BHN and that the maximum pressure is 17152psi. Is their a rule of thumb for gas checked bullets?

I would like to throw this data into quick load to get a idea of where to start my load at.

Don't know what data you are reading but that psi sounds more like minimum pressure for obturation rather than maximum pressure. Bullet casters do not agree on how hard a bullet needs to be. So you get opinions and math formulas that vary. Here is a clip from page at htis link. http://www.lasc.us/CastBulletNotes.htm

Example: Alloy BHN of 12 multiplied by 1422 = 17,064. An alloy of 12 BHN should be used with a load that develops a "minimum" of 17,000 psi. Need more info on minimum / maximum alloy BHN? These Glen E. Fryxell articles explain alloy BHN in easy to understand language

Your alloy reading a BHN of 13.4 would be 13.4 * 1422 = 19,055 psi. That is minimum psi to force obturation of the bullet. Which is a higher number than you quoted as max pressure. There are different camps out there as far as how hard a bullet needs to be. In a 44 mag you don't have to hunt far to find someone that will tell you it must be at least 22 BHN. I'd say your bullets are hard enough. In fact they are harder than what I shoot since I load expanding bullets in my 44 as opposed to the solid "hard-cast" wide flat nose. After your bullets harden a bit and reach 14.5 ? you'd need almost 1,600 fps to get any deformation on impact.

Gas check helps with those heavy bullets. I wouldn't say they were a waste of time.

[stubert]

When using a gas check, I will use data for j bullets if no other info is avail. I have never had much faith in the psi chart that comes with Lee's hardness tester, If I did we would all be shooting subsonic loads. P.S. Anything shot with a c-310 gc. when properly placed does not need to expand much, that bullet makes 2 big holes on game.

[GreenMachine79]

RobS, That could be it, I lubed the pivot pins with anti seize but I didnt lube the alignment pins and the sprue plate itself.

GabbyM, pamphlet that comes with the Lee Hardness Tester gives that as max PSI. I would expect to shoot a actual velocity much higher then what that pressure would provide.

Everyone else thank you for the informaton.

[JIMinPHX]

You are going to run into problems with pressure before you run into problems with velocity. I've pushed a gas checked 13bnh boolit over 3,000fps out of a .223. Accuracy was a challenge above 2,500fps, but other than that, I had no problems.

In some recent tests that I did with a .44 mag, I found that slower powders & harder boolits gave me better accuracy because heavy charges of fast powders like Unique would deform the boolit before it ever left the barrel.

Edit: This is the thread discussing that issue.
http://castboolits.gunloads.com/showthread.php?t=81258

[leftiye]

Anti seize may be the problem. I don't know what your stuff looks like, but mine is a thick greasy goop with copper and stuff in it. It may be possible that it is mis aligning your mold blocks. Try using Bullplate lube maybe. Pay special attention to anything sticking to the V-grooves and sticky outie parts that fit in them. Sand them smooth maybe.

[Bret4207]

I'm a little confused, I thought that gas checks were meant for higher pressure/velocity, as in full loads. If they are not going to be of any benefit I would rather not go through the trouble and expense of putting them on.


GC's make it easier to get higher level performance, sometimes a lot easier. Depends on a multitude of things. Bit overall as pressure rises GC's make things far, far easier to work with.

They also make he difference at lower pressure in some guns, sometimes because of bore condition, sometimes because that's just life.

[qajaq59]

Check your mold blocks with a magnifying glass. It only takes the tiniest bit of grit or whatever in one of the grooves to keep the blocks apart. I had one that took me 15 minutes to find one day, and I could barely see it with the glass. One part of the problem is that the lead stuck in there is the same color as the aluminum.