Gear's 190x

[btroj]

Ok Popper, why does one alloy do better in one rifle but in both? Because alloy needs to be matched to the pressure curve.

See why all this is important? Look at the link I posted, Rick found that after a certain point a harder bullet shot worse, not better.

[cbrick]

I am sure you are quite familiar with this?

Oh yeah, I call it the "what if virus" and trust me, there is no cure for it. Every single "what if" you experiment with opens up 10 more "what ifs". Precisely why this thread and all of your testing is so fascinating to me.

Rick

[btroj]

I have a chronic, and possibly terminal, case of "what ifs".

That disease is what makes me question everything. I hold few things so dear as to not question them. Gear and I spend lots of time discussing what ifs. Others seem to revel in our disease and keep giving us a daily fix of more what ifs. I call them enablers and teachers.

It it also makes me seek out like minded people. People who understand that respect isn't something that is destroyed by questioning one another.

My daughter has a case that is still in it's infancy. As an engineer I am sure it will soon bloom into a full blown case, or at least I hope it does.

[cbrick]

Rick found that after a certain point a harder bullet shot worse, not better.

Yes but the reason I keep saying that my testing was with revolver is the relationship between throat fit is a different thing in a rifle (I can only assume). I use a mild snug fit in the throats. I can take the cylinder out of the revolver and place a sized bullet in each throat, jiggle the cylinder and the bullets do not fall out yet I can use a pencil and lightly tap them through. I also use a heavy for caliber bullet that is long enough that the full front driving band is fully in the throat with a chambered round giving a reasonable gas seal and alignment with the center line of the bore. The bullet is long enough that as the front driving band is entering the forcing cone the rear band and gas check is still in the throat, still giving a reasonable gas seal and alignment with the centerline until it clears the throat, by then the front driving band is fully engraved and sealing the bore and aligned with the center line of the bore as well as possible. The addition of the barrel cylinder gap will in my mind only limit velocity as by then the bullet is as aligned with the center line of the bore as well as I could make it in a given revolver.

Years of testing has proven this as most accurate in my revolvers but this discussion is about rifles and you guys are testing . . . Bullet, chamber/throat fit and alignment with the centerline of the bore along with alloy strength. Will the same increase in BHN have the same effect in a rifle? How close will that kind of throat fit be between rifle and revolver? Dunno, I'm all ears.

Rick

[btroj]

A revolver also has a bunch of free bore compared to a rifle. You have a bullet gaining speed in the cylinder throat and forcing cone before it hits the rifling. I assume, and that word is nothing but trouble, thst a revolver demands an alloy that can hit the rifling and begin spinning without excessive stripping.


A rifle is very different. Our bullet is just gaining speed when it hits the rifling, heck, we can have it on the rifling if we want. This opens other cans of worms. How much throat contact? How much jump?

Yeah, there is some difference but the alloys and how they behave when heat treated is the same. I have no doubt that your data will be an excellent start point in studying alloy, it is how that data pertains to shooting that will be different.

[cbrick]

I'll add to that my match revolver has throats that measure .357" across all five throats, the groove diameter measures .357" and all measurements are within a few tenths. Bullets sized anything over .357" will not chamber.

Rick

[Larry Gibson]

cbrick

I have tested with the same HV load (2350 fps) out of my .308W M70 target rifle using the 311466;

COWW +2 % tin, Lyman's #2, 80/20 linotype/lead and linotype. .....AC'd & WQ'd and appropriately aged.

I have also tested the best two of them at 2600+ fps out of my .308W Palm rifle. ...

If anyone is interested?

Larry Gibson

[geargnasher]

I certainly would be, as I am in the middle of a similar process albeit with significantly different alloys. I am taking an approach that will hopefully paint a picture of trends, meaning that I am compiling velocity vs. group size data with each alloy, not at just one or two "set" velocities where accuracy was found with one or more alloys.

Eventually, if I and my interests live long enough, the plan is to perform a similar test to what Rick did with his FA revolver (but in the .30 XCB) by drawing an alloy that had proven itself suitable in the previous testing to different hardness and finding the "sweet spot" with ONE load where all other variables are kept as constant as possible. Between data plots involving different pressure curves and peak pressures/velocities with same alloy and testing only temper of an alloy while all else is held constant, and group size being the method of scoring for all tests, some trends should be noted and some guidelines established.

I believe that unless you demonstrate where the peak or valley of the data is by generating enough data to plot a curve, any snapshot data has little meaning beyond the exact condition that generated the snapshot. Snapshots are useful, none the less. Please share.

Gear

[cbrick]

Gear, I didn't choose WW alloy based on previous results. I used it because I had 800 pounds of COWW in 5 pound ingots acquired over time from different areas. I blended all 800 pounds together into one homogenous lot of WW alloy, still using that same lot of alloy.

Your correct about snapshot data, the main reason my testing took a year and a half was that all tests were repeated many, many times to average results. Often a test wouldn't be repeated for months before getting back to it. Your also correct about snapshot data in that it's usually a snapshot of a single test that inspires continuing with that test to see if it will repeat.

I also learned during this testing that the single easiest way to destroy groups wasn't the actual BHN of the alloy. Yes, going harder over 18 did open my groups, 25 BHN groups averaged larger than 18 BHN but shooting groups with mixed BHN destroyed groups. I tried shooting groups with 5 different BHN's in the same group and not only did it not group I was lucky to even hit the target. This realization led me to convection oven heat treating only and eliminate the variability of quenching from the mold.

Hope this helps and inspires some thinking.

Rick

[geargnasher]

Rick, I've done the same thing with case neck tension when seating bullets by feel and sorting into lots to be fired by group. The group size difference between small lots that required more or less seating pressure was slight, but the POI was significantly different. If mixed, good groups would turn so simply horrid ones.

I really never had much getting consistent BHN when water-dropping my rifle bullets, but I think Brad has re-discovered why that is. I almost always use a 50/50 mix of COWW and near pure lead, but I have about 450 lbs of COWW that have been re-mixed with each other a few times as my fluxing knowledge improved, and one of those times I added a bunch of assayed solder that I got cheaply here to bring the total up to just over 2%. One of the reasons I cut my WW in half is to halve the tin. So I get about one percent tin in my WD mix, which according to Brad's and quite a few other's results makes less of a variance in final hardness. Water quenching from a hot mould meets at least the maximum the alloy can go, if I quench them any hotter or any faster they end up the same anyway after aging a few weeks. I AM very methodical about my water-quenched castings and it seems to be working, but if I used as much tin as you did I seriously doubt my methods would work and I'd be going to the oven as you do. No doubt the convection oven is the ultimate in consistency and predictability.

Gear

[popper]

Btroj agree with you completely. Guess I didn't state clearly.

why does one alloy do better in one rifle but in both?

BO AR is plain base, 308AR is GCd. ~ some pressure.
My intention was to give Gear some HT with Sn results I get. I'm guessing hard holds the lands but doesn't make the jump very well. Edit: rethinking (as I can't recover any) too hard may be like trying to hammer a wood screw into a 2x4 but the screw deforms vs the wood.
Anyway, I tested 3 loads (4227, 1/2 gr steps), 310 & 311, 3 alloys (iso, iso/pure 6/2, my normal alloy - all PC & H.T. @ 50 I could see the group size vary and it was very obvious (no leading). Iso did poor at mid load but OK at max ( >1800). 6/2 was ok at mid lever & poor on BOTH sides. Mine was only good at low load. Sizing also made a difference but that's another thread.

[cbrick]

I don't know that going from 1% to 2% Sn would change the final outcome much. I don't know that it wouldn't either but I doubt that small a percentage of Sn would make all that much of a difference.

A difference in Brad's oven heat treating (he got the same BHN at both 375 and 440 degrees) and mine is a test I have wanted to do for quite some time and never gotten around to it, he may have answered the question for me. ALL of my oven heat treating has been one full hour in the oven. Brad uses a half hour. Does that matter? Dunno but it is something that I've considered and wanted to test. Here's the deal, heat treating a Pb/Sb alloy works because of the crystalline structure of the Sb grows to a certain point at a certain temp. It takes time for that structure to form and I doubt just getting it hot (a half hour) would achieve the desired crystalline structure, in other words, not enough time for it to form. Once the crystalline structure is formed quenching it suddenly from the oven temp to the water temp freezes the Sb structure in place. That's why/how a quenched Pb/Sb alloy heat treats to a harder BHN than an air cooled bullet from the same pot of alloy.

Rick

EDIT to add: Not only were the bullets in the oven for a full hour but the oven was pre-heated to the desired temp before the bullets were put in but timing the hour didn't start until the oven returned to the preset temp, from that point the hour was started.

[btroj]

Rick, I never considered soak time and allowing crystalline growth. Makes me wonder if the time in the oven alters final hardness or consistency. Great, another what if.

We have much to look into, don't we?

What most don't undersrand is that much of this testing involves no trigger time. We can't understand what happens in the barrel if we don't know more about the alloy and how it behaves, how we can alter that behavior, and how to make it repeatable. Nothing would be worse than having multiple batches of bullets and each one needs a load tweak. I'm not interested in reworking loads every few hundred rounds.

Ok guys, what do we need to do for testing? What needs knowing and how do we learn it?

Brad

[cbrick]

Rick, I never considered soak time and allowing crystalline growth. Makes me wonder if the time in the oven alters final hardness or consistency. Great, another what if. Brad

No, that is not a what if, that is the metallurgy of Pb/Sb alloy. It takes X amount of time for the crystalline structure to grow, it doesn't just pop up because it got hot, the unknown for me was if a half hour would do it and it appears from your heat treating results that no, not enough time. If you want another what if try going in the other direction, try 2 hours in the oven and see if the crystalline structure continues to grow after the one hour testing I did or is the structure maxed out in an hour?

Rick

[btroj]

Sounds reasonable enough. Should reduce errors from overn temp fluctuations. I don't have a good way to know if my temp is steady or not. I sure don't intend to sit and watch a thermometer for hours, for that we need a retired guy!

[cbrick]

Sounds reasonable enough. Should reduce errors from overn temp fluctuations. I don't have a good way to know if my temp is steady or not. I sure don't intend to sit and watch a thermometer for hours, for that we need a retired guy!

I wasn't retired when I was doing all that, I was working 16-18 hour days. If I could do that you certainly can with your part time job!

I did have the advantage after I quit using a gas fired cook oven and switching to the electric convection oven that it does hold a pretty consistent temp and I added two oven thermometers inside to be sure. I bought that oven specifically for the loading room and heat treat testing. I also installed a laundry room sink in my loading room right next to the oven.

Rick

[runfiverun]

the only two direct comparisons I have done with the 4/6 and the ww alloy has been in the AR/223 and in my 308 using the rcbs 30-165 silh boolit.
with the rcbs boolit I just swapped out the higher bhn boolit for the other and seen an increase in accuracy across the board without even weight sorting.
the main reason I went to the alloy with this one was because the wife can cast with it easier [shrug] so it just happened as a by-product and not really part of a test.

the AR/223 use come about out after a little bit of frustration using lino-type, and hitting a wall where everything went off.
I tried ww and W/D but was flat stuck again.[worse off actually]
I tried the 4/6 as a 'well there is some in the 20 pound pot and it's about halfway between the two, so let's give it a go' type thing.

I still think the As in the ww alloy adds something to the mix too.

[popper]

Crystal growth is WRONG! You don't want that growth - makes for brittle boolits! You are heating a solid and the molecules need time to move around to form SMALL clumps (electrical mobility). There will always be clumps, smaller is better. Quenching stops the mobility (almost), tin is more mobile at room temp and will grow dendrites which makes it brittle. I heat for one hour & quench, hardness is there in a day or so. Labs usually heat for 3 hours, slice & take electron microscope pics. I'm not going to wait that long. I'm playing with alloy for a plain base so I get just (hopefully) alloy characteristics. I stay away from the slump temp, so 400F, yes I'm PC and that's the proper temp for PC.
Didn't want to wander from the mould thread but will interject correctness.
As allows HT to work better.

[cbrick]

Crystal growth is WRONG! You don't want that growth - makes for brittle boolits! I'm PC and that's the proper .

So what your saying is that the metals industry has it all wrong right? I'll let them know.

The brittleness of a Pb/Sb bullet will be directly related to the percentage of Sb in the alloy, HT'ing that alloy adds little to no additional brittleness which is the reason for HT'ing as opposed to just adding more Sb.

As for don't want growth unless you air cool the alloy you've got it, that's antimony plain and simple. See the NRA Cast Bullet Handbook (I think it was that book), some excellent photo's of the crystalline structure.

Rick

[Doc Highwall]

A question for the people that heat treat their bullets with a toaster oven and then quench. What kind of tray are you using to place the bullets on and how many bullets or how much room between bullets so the water will be able to reach all the bullets surface for even quenching?