plain base hardness for the 444

[Marlin Junky]

Insted of getting right to the point, I'll provide some detail first. I've got a PB mold that drops .433+" boolits that I plan to use for my 444 Marlin (it's a 1:20" twist 336). I poured some the day before yesterday out of range scrap and COWW metal. My porportions of RS to WW metal are uncertain but the the air cooled BHN on those cast the day before yesterday measured 11.8 using the Lee hardness tester last night just before heat treating. So, I heat treated last night in a conventional electric oven with a wacky thermostat on a setting that shuts off the power at just about 450F and comes back on at just about 420F. This was calibrated with my RCBS casting thermometer. When I quenched in ice water I should have noted where things were in the thermostat cycle but unfortunately, I didn't. I was actually more concerned about attaining any appreciable hardness at all in contrast to the actual results. Perhaps it could be that my alloy is climbing in % range scrap and now has more Sb than I'm used to. I'll appreciate input regarding alloys and heat treating; however, my primary concern for now is:

The next morning, like right now, these bullets are absolutely unscratchable with a human finger nail... I was going to wait a couple days before applying the Lee hardness test again. Normally it takes at least 24 hours to notice any increase in hardness but normally I don't use this oven. Anyway, here's the question:

I sized these boolits in my .433" die before hardening and am wondering whether I should load and shoot them in a week (at this rate they'll probably register over 20 BHN a week from today) or draw them back to about BHN 14-16 before shooting. I was going to use about 25 grains of 4759 with these 315 grain boolits. I don't have a lot of experience with PB boolits and am not sure what a good hardness for this barrel would be. It's a 1:20" twist with 6 shallow grooves... not micro, but nevertheless, shallow (about .003" deep, at best). I'm not even sure if the barrel has one of these infamous Marlin restriction that has been plaguing the new guns for years (due to all the modern barrel stampings; i.e., WARNING labels) but it does shoot gas checked boolits very well.

Thanks,
MJ

[softpoint]

I have heat treated boolits, and water dropped them, and I haven't noticed any appreciable softening, or further hardening, within a few days, anyway.
I am wondering how you would draw the boolits to a pre-determined hardness after they were heat treated, especially if the exact alloy is not known?:lovebooli

[Marlin Junky]

I've drawn back this alloy (or something close to this alloy) which has been heat treated to near 30 BHN by oven tempering (in my usual oven) at temps ranging from 300F down to 225F in 25 degree increments. I'll assume for now that in a week the final BHN will be about 25. If so, I'll probably select 250F and let 'er rip for about 20 minutes then open the oven door slightly and let 'em cool for about 1/2 hour before removing them from the oven. I've found that 20-30 minutes at 225F will only lower the BHN a few points while about 30 minutes at 300F will remove most of the hardening and anneal the boolits to within a couple BHN points of their air cooled (after casting) hardness. It'll be pretty much a hit or miss proposition but 20 minutes at 250F will definitely soften them somewhat. The real question is... how hard should they be for this Marlin??

MJ

[softpoint]

I'd go softer than 20 BHN. I had an experience with plain base boolits in a Marlin 45/70, that I was trying to load with 27-30 grs. 5744, and kept getting leading. Turned out those boolits were too hard. They were water dropped WW with about 1 lb. per 20 of lino. I heated them in a toaster oven to soften them and then they worked fine at the pressures I wanted to load them. I didn't have a hardness tester at the time, but that is what prompted me to get one.
I'd think that 12BHN at the most would be enough, but of course every rifle is a bit different in what likes. :smile:

[44man]

It depends on what you are going to do with the rifle.
If just for target, plain old WD, WW's at about 22 BHN should work but I see nothing wrong with harder and it will depend on your groups.
Now for deer, the gun might shoot too fast for hard lead and it will make a nice hole poker so I would go softer for hunting.
I have accuracy problems with soft PB though so I am going to make two part boolits for next season.
I have never experienced leading from harder boolits so only you will see what your gun does.

[Marlin Junky]

This lil' exercise has nothing to due with hunting performance, just accuracy on paper targets. I'm going to draw these back to hopefully BHN 14 and shoot 'em on Wednesday with 26 grains of 4759 which should get me about 1500 fps from the carbine length barrel.

MJ

[softpoint]

This lil' exercise has nothing to due with hunting performance, just accuracy on paper targets. I'm going to draw these back to hopefully BHN 14 and shoot 'em on Wednesday with 26 grains of 4759 which should get me about 1500 fps from the carbine length barrel.

MJ
14 BHN ought to be right in the ball park. I suggested 12, not much diff. and that got me good accuracy and no leading in a Marlin 45/70 CB and a LTDIII. at about 1400 fps.
Let us know how she does

[Marlin Junky]

14 BHN ought to be right in the ball park. I suggested 12, not much diff. and that got me good accuracy and no leading in a Marlin 45/70 CB and a LTDIII. at about 1400 fps.
Let us know how she does

Thanks Softpoint... I'll post a pic of the target(s) if they please me. 20 minutes at 275F ought to get me in the ballpark. If I only hit 16-18 BHN, I'll add an additional 10 minutes to the draw-back time.

MJ

[Marlin Junky]

The alloy which registers about 12 BHN air cooled ended up BHN 33 after the heat treatment performed Saturday night (two days ago). It took 30 minutes at 300F to draw it back to about 15 BHN which is what I'll be shooting Wednesday 'cause I'm running out of time. The lube will be BAC. I'm also going to try 10 rounds with a home brewed lube that I feel might work better at low pressure (26 grains of 4759 for probably about 1550 fps).

MJ

[44man]

I would have kept a few of the hard ones and made a side by side group size with each.
I love 4759 and use it in my 45-70 revolver with Dacron. I had one 420 gr boolit that I reduced the load for. My normal load is 28.5 gr but I went down to 27.5 and the powder did not light with one shot and the boolit was in the bore with all the powder behind it.
A rifle is different of course and it might never happen and you might see groups open instead.
I also use a LP mag primer that makes a difference too, I don't want the boolit to move out in the long cylinder.
I have zero experience with a .444 and have no idea how much 4759 to use. Just a thought if you download, make sure all shots leave the barrel.
If groups are poor, just increase the charge a little at a time. The powder is very accurate.
Marlin made a mistake going to what they call "Ballard" rifling without increasing groove depth, however, your twist rate is good.
Internal volume of the .444 might be close to the 45-70.
I use 31 gr of 4759 with a 317 gr boolit in the 45-70 revolver for 1632 fps.
The sad part is that it is hard to find good info for 4759.

[Marlin Junky]

I would have kept a few of the hard ones and made a side by side group size with each.

I cast hundreds of these 315 grain PB boolits out of the same alloy and can heat treat to all kinds of BHN values... oh the joy!

I think 26 grains is a pretty good place to start with this boolit because 27 grains averaged a tad over 1600 fps with the shorter Lee c430310 at 314 grains ready to fly. IIRC the Lee boolit is just about .850" long and I just measured my 315 PB at .900". I'm also going to place a wad underneath the 315 PB so the combustion chamber will be somewhat less.

MJ

[onesonek]

This lil' exercise has nothing to due with hunting performance, just accuracy on paper targets. I'm going to draw these back to hopefully BHN 14 and shoot 'em on Wednesday with 26 grains of 4759 which should get me about 1500 fps from the carbine length barrel.

MJ

I found the temp guide on lasc pretty helpful and close. Any differences , I could easily attribute to my oven and or thermometer. If 2-3 gain in bhn is your goal in the future, try 385-390 degrees and quench in cold tap water. For every 5 degree increase in the oven, quenched with cold tap water, seems to give about 1-2 bhn increase (closer to 1 when over 400*, and tap water). My tap water runs about 56-58 degrees, and found this quite repeatable. Even with my oven, like yours fluctuates some, although not as much.
My suggestion with your oven, is to set it at 400*, then monitor it's cycle times, check the temp with your other thermomter in the middle of the cycle. Then adjust up or down to the 400* . HT the batch and quench in tap water, use this as a baseline.
Ice water would likely give you more increase in bhn over tap water, due to the temp differential. Personally, I really don't see the need of using ice (or dry ice/antifreeze), unless one is trying to gain much more than 10-12 bhn over aircooled.
One other thing I thought I read about somewhere????, and decided to try.
I had an alloy that aircooled about 11.5 after a week. I HT'd a batch, and after 2 days, it was about 15. I thought I would see if this sped up process might work. I HT's another batch, and 3-4 hrs. after quenching, I put them back in the oven at lowest temp of 170*. I let them warm 2 hrs., then turned it off leaving the boolits in there to cool slowly over night. At roughly 24 hrs. after turning off the oven to cool, they tested bhn19. 4 points difference on the same alloy and same HT temp., with the goal of 18-19. So it seems one can speed up the age hardening of HT's boolits. (hope it wasn't a fluke). Haven't had the time to confirm with a second test. Been going to try it with aircooled as well, when I get a chance. The alloy was COWW / ISO, and some extra SN, that figures out roughly 95 - 2.75 - 2.25

[44man]

I cast hundreds of these 315 grain PB boolits out of the same alloy and can heat treat to all kinds of BHN values... oh the joy!

I think 26 grains is a pretty good place to start with this boolit because 27 grains averaged a tad over 1600 fps with the shorter Lee c430310 at 314 grains ready to fly. IIRC the Lee boolit is just about .850" long and I just measured my 315 PB at .900". I'm also going to place a wad underneath the 315 PB so the combustion chamber will be somewhat less.

MJ
I would not use a wad. Use a tuft of Dacron so the boolit pushes it down a little when seating. Don't pack it. Just keep the powder near the flash hole.
Wads can get you in trouble and seating depth is over blown because each boolit needs a load workup. My strange findings are that the same load works best even with different depths because none of my loads are max anyway. Accuracy is always a velocity, twist match.
Based on the same boolit weight even with a slight difference in depth, loads will be close, maybe 1/2 gr and many times they are the same. Only with max loads will a deeper boolit be too much.
I have two boolits for my .475. They are exactly the same and seat the same depth. One is a PB and the other a GC. Same alloy. The GC boolit will stick cases with the same load as the PB. I MUST reduce the load.
Don't work with paper and pencil, work loads only. You might even find a deeper seated boolit needs MORE powder for accuracy. There are no stone tablets, only safety first, then accuracy.
You need to understand that even two different boolits of the same weight, seated at the same depth can also change pressure.

[Marlin Junky]

I would not use a wad.

These are polyurethane wads that I cut from a sheet about .075" thick, place in the case mouth and seat with the boolit. The function is not to take up case volume but to protect the edge of the boolit's base. Nevertheless, it does take up some volume and in conjunction with the very tight .433" PB boolit with a longer bearing surface than the .431" Lee C430310, and less case volume, I feel it's prudent to start with 26 grains rather than 27; not for safety sake (I'm playing in the domain of 20K PSI or less with 4759!) but because I want to be in the 1500-1600 fps range for my early attempts with PB in this gun. Perhaps I need to be in the 1400-1500 fps range. I won't know that for a while yet but I'd rather juggle the BHN than drop below 1500 fps.

MJ

[Marlin Junky]

Onesonek,

Thanks for your observations on heat treating... our experiences are similar assuming I stick to my convection oven... which I will be doing.

MJ

[onesonek]

Wished I had a convection oven,,,some day.
With this conventional electric, I thought it might be not a dumb idea to put a ceramic baffle (14" pizza stone), under my stainless steel strainer/quenching pan. Not sure it does anything or helps, but thought it might buffer some the heating element while in the on mode, as to not get too much direct heat under the boolits. I also place the pan on a couple 1/4" x 1/4" wood slats , to have air flow under the pan.

[Marlin Junky]

The insulator may help. I'm pretty much convinced that the proximity of the boolits (in my opening post) to the heating elements is why the hardness turned out greater than expected. I sized the boolits before heat treating them, thus creating shinny spots on the driving bands which took on a color cast similar to a 500F+ heat treat in my convection oven. The electric oven in my opening post is also infamous for burning my wife's cookies. Better equipment means more repeatable results. 8-)

MJ

[onesonek]

I totally agree on equipment and consistency,,,,,unless like my wife. She can burn cookies regardless :???:
Someday I will have a good convection oven,,,,,for the boolits. I quit eating cookies a long time ago!

[44man]

These are polyurethane wads that I cut from a sheet about .075" thick, place in the case mouth and seat with the boolit. The function is not to take up case volume but to protect the edge of the boolit's base. Nevertheless, it does take up some volume and in conjunction with the very tight .433" PB boolit with a longer bearing surface than the .431" Lee C430310, and less case volume, I feel it's prudent to start with 26 grains rather than 27; not for safety sake (I'm playing in the domain of 20K PSI or less with 4759!) but because I want to be in the 1500-1600 fps range for my early attempts with PB in this gun. Perhaps I need to be in the 1400-1500 fps range. I won't know that for a while yet but I'd rather juggle the BHN than drop below 1500 fps.

MJ
I have recovered thousands of boolits and never seen harm to the base. Only skid in the rifling with ones too soft.
Slump is different and can ruin a boolit top to bottom. A .38 can blow lead from the gap using pure wad cutters. Harden the boolit and it goes away.
Play with the hardness to find what your gun likes best.

[onondaga]

Your rifle is going to tell ypu how hard it likes boolits. Plain base boolits should be hard to prevent gas jetting as you have no gas check. At around 20 BHN you are going to have plain base boolits that will handle any safe load you can put in a .444. I wouldn't be any more concerned than that.

I have had good results in .458 Win Mag with plain base boolits at 15 BHN combined with BPI Original ballistic filler. This particular filler acts as a quasi gas check and allows softer alloys to be shot at pressures and velocities significantly higher than would be expected.

Your 20 BHN alloy will expand very little to none on game. If you will be hunting, a flat nose 444 bullet doesn't need to expand and they punch hard. But if you want expansion #2 alloy striking game with 1000 or more foot pounds of energy still left at your hit distance will expand the boolits 2X their diameter.

My .458 with a 340 gr boolit and a muzzle velocity of only 1610 fps with H4895 and BPI filler still has just over 1000 foot pounds of energy at 200 yards. The boolits are plain base #2 alloy. You could easily duplicate those ballistics with a 444. This is actually a wimpy load in my rifle that kicks less than a 30-30 lever rifle but the the load is a stellar performer on deer and bear in New York State for me.

Gary

[softpoint]

Shot any of those boolits yet Marlin?

[Marlin Junky]

Yeah... just got back from the range. Nothing to rave above but pretty good for a first cut, I suppose. No leading to speak of and 1.5-1.75" groups at 50 yards with the Leupold set on 4x, 26 grains of 4759, BAC and a foam wad. Alloy was probably near BHN 15 and I'm shooting for a little softer alloy next time. Velocity was around 1600 fps but the extreme spread was pretty high for 4759... at least I thought so.

MJ

[softpoint]

That ain't bad at all, that is about what most of my Marlins in 45/70 do as an average with plain base boolits.

[Marlin Junky]

I need to be puttin' them in one hole at this range. At 75 yards this gun will shoot 3 leaf clovers with Lee C430310 loaded hot (2100 fps).

MJ

[softpoint]

I get a bit better accuracy with gascheck boolits, and higher velocity,too. Not sure why, but my gascheck boolits give me better accuracy than paper patch, too. But to be honest, I haven't played with paper patch nearly as much as either plain base or gascheck. It is what makes shooting cast boolits interesting. Always more variables to try to see if performance out of a particular rifle can be improved.[smilie=2: