Burning rate vs. pressure curve and leading

[JudgeBAC]

I am still struggling mightily with the concept of burning rate vs. pressure curve and the effect if any on leading.

My case in point is a M29 Smith .44 mag. With 429421 and 10 grs. of Unique I have a very consistent low extreme spread quite accurate load. However, it leads like crazy. Take the same boolit from the same alloy and shoot it with 2400 and no leading. The problem is I can't find near an accurate load with the 2400.

So, I switch to a gascheck boolit 429215 using W-540. I.E. since I cannot solve the problem cover it up using a gascheck. Similar problem, at the upper end leading. At the lower end not as much leading but not as accurate. And by the way, I have used pin gages to measure the throats, had the throats re-cut and they now are compatible with the bore size.

Now I am thinking of going back to what John Ross suggested in an article about the .44 mag. Use a very slow powder at 100% plus loading density and avoid the apparent fire ball from faster powders which must be causing the problem?

Please weigh in, I'm 52 and don't have much hair left to pull out.

[HollandNut]

A higher load density with a slower powder is much gentler on the bullet , or so we all say ..

I always seem to get better results going that route ..

Dont worry , I'm fitty two and done pulled all my hair out ..

[Shuz]

Have you tried 18g of 2400 or 17g of WC820 with your 429421?

[JudgeBAC]

I have tried 18 gr. of 2400 with so so accuracy. My next experiment will be with VV N110.

If that is not successful I may try IMR 4227 or H4227 and Accurate Arms 1680.

Burning rate charts are great to show relative burning rates but they don't give much information about flame temperature and pressure curve.

Glen Fryxell noted in an article on the lSAC website that both Unique and 2400 had high nitroglycerine content and therefore had a higher flame temperatures which could result in leading.

I am not sure if any resource information exists concerning flame temperature of cansiter powders.

[Ricochet]

Burning rate charts aren't that helpful, really. They give an order of relative burning rates, not quantitative data. On a given chart, some adjacent powders may be nearly identical, whereas others may be far apart.

Also, in actual cartridges, the true burning rates of two powders often swap positions. Alliant says Red Dot burns 94% as fast as Bullseye. But loading manuals are full of pistol data with Bullseye having a larger maximum charge under the same bullet as Red Dot, with similar velocities and pressures.

Pretty much all the burning rate charts can do is to give you some idea of similar powders that you may want to try.

[JudgeBAC]

Richochet, I agree wholehartedly, but then where do we turn for better information? Q load?

[bcp477]

Experimentation. The only place to turn, unless you can find someone that has been through the exact process, with the same powders and projectiles.... in the same cartridge with which you are working.

Faster powders = a more abrupt "shove" on the bullet.....and pressure peaking EARLIER (which makes perfect sense, when you think about it).

Slower powders = a more gentle "shove" on the bullet..... and pressures peaking LATER.

Think about TIME in relation to burn rate..... faster = EARLIER / slower = LATER.

This is exactly why a faster powder will generally work better with a shorter barrel.....and a slower powder (by comparison) will generally work better with a longer barrel.


A faster powder will ALWAYS produce greater pressure in a given cartridge....vs. the SAME amount of a slower powder, in the same cartridge.

As others have said, a burn rate chart is only for relative comparison.....for choosing the approximate range of powders to try. Experimentation in your particular application is the key. Choosing the right powder is at best, an educated guess.

[Bullshop]

Something I have found interesting is when I shoot bore diameter boolits with smokless powder the burn rate has to be quite fast or the boolits do not obturate enough to fill the grooves to make a seal. If the powder is too slow accuracy is non existant.
With groove diameter boolits its not an issue. In general with groove diameter boolits I look to powders that could be considerd too slow for the caliber/boolit weight for my most accurate boolit loads.
Bore diameter will shoot quite well but need that kick in the butt from a fast burn rate smokless powder or black powder which is a fast burn compared to smokless powder.
BIC/BS

[madsenshooter]

Now, I'm not much of a revolver person, but it seems to me I read once about barrels being constricted where they are tightly screwed into the frame. You got your cylinders done, have you checked for constriction at the frame? If you had one there, it'd swage the bullet down a tad, then allow gas to blow by and cause leading in the rest of the barrel. The difference between Unique and 2400 in that respect may be that the pressure/time curve of 2400 obturates the bullet after this swaging down takes place, if it takes place. I guess the place to start would be some slugging of the bore in the frame and outside the frame to see if there is any constriction.

[MtGun44]

What are your throat diameter, boolit diameter and alloy + condition, and last but not
least - what lube? 10.0 Unique is a "gold standard" load in all my .44 mags, and most
other people's guns, too. If you are getting leading, we need to delve a bit deeper and
see if we can find the issue. You want throat diam + .001 or .002, WWt alloy air cooled
should work, maybe with a touch of tin, and nothing spectacular on lube, but at least
50/50 Alox/beeswax for a start.

Do you feel a tight spot in the bbl at the frame?

Bill

[JudgeBAC]

I had the throats opened up to .430, the bore measures .429, no real tight spots to speak of but unfortunately there are some prominent tool marks about an inch into the rifling past the forcing cone.

In an attempt to smooth out the marks, the barrel was firelapped. This seems to help some.

My next experiment will be with the .432-265 ranch dog bullet and XMP 5744. I emailed Western powders and one of their technicians sent me some load data to try. By the way, his reply was within 24 hours and very helpful. Nice folks to deal with.

[JudgeBAC]

Yes, groove diameter is .429 and no I have not tried Unique with 429215. For whatever reason, Unique has not worked in this gun with any other boolit. That is I have experienced leading with every boolit using Unique in this gun. 10 gr. of Unique with 429421 provided excellent accuracy but bad leading about .5 into the forcing cone and for another inch or so.

Of course, this could be the exception but I am going to try the slower powder route to see if that works.

[badgeredd]

My best accuracy vs, energy loads have always been with powders in the H110 range. Recently I tried some VV N120 and now I have to buy some for my 4-4. For whatever reason it seems to give me better accuracy with heavy boolits than I've gotten in the past. Your mileage may vary.

Edd

[JudgeBAC]

Success at last. Ranch Dog 432-265 sized .432 lubed with LLA. Weighs 273 grs. with gas check. 19.8 grs. of IMR 4227 1" 5 shots at 25 yards with virtually no leading. Another promising load is 19 grs. of 5744 same boolit 5 shots into a little over an inch. Federal Large pistol primers. Shot in a M29-10 6" with 2x Nikon scope.

Now I can back off to 50 yards and get into some serious load development.

[JudgeBAC]

One other observation: for whatever reason, the 5744 load seems to have less recoil than the IMR 4227. Curious.

[felix]

True, because 5744 has 20 percent nitroglycerin and comes on quickly after the heavy deterrent is gone. 4227 will not have that quick rise at that same pressure point commensurate with 5744. The AVERAGE pressure developed will be very close for the same energy contained within each, no matter what the total curve looks like. The 4227 curve will not be as peaky as 5744 given the same internal expansion space, provided the space provided does not entirely consume the peak given by 5744, meaning that a "sharp peak" never occurs. ... felix

[JudgeBAC]

Obviously the best powder will be the one that produces the best accuracy without leading.

Theoretically, which would be the best powder with a plain base boolit? Can you make the general assumption that the higher the nitroglycerin content the higher the quick rise in pressure and a commensurate rise in flame temperature which would be bad on a plain based boolit?

Also, where is the information on nitro content in various powders?

[Molly]

[QUOTE=JudgeBAC;717555]...My case in point is a M29 Smith .44 mag. With 429421 and 10 grs. of Unique I have a very consistent low extreme spread quite accurate load. However, it leads like crazy. Take the same boolit from the same alloy and shoot it with 2400 and no leading. The problem is I can't find near an accurate load with the 2400.

Ahhh, JudgeBAC, I REALLY don't mean to bust your chops, but the scenario you present (good accuracy with a light load and poor accuracy with a heavy load) is very often explained by flinching. Are you testing from a rest? Has anyone else gotten the same results with your combo? I suggest you take the pistol and a box of 18g 2400 loads to a good range, and wander around until you see someone bringing back some good targets. Ask him / her to fire your gun and ammo just as insurance that the problem is not behind the gun's grip.

Another way to check on this (and I speak from long, bitter experience) is to have a buddy load the pistol for you while you look the other way. He's to load two to four rounds only, and leave enpty cases in the other chambers. Then he's to spin the cylinder and hand the closed gun to you. Fire a few cylinders of this at a target. If the muzzle jumps even though there was an empty case under the hammer, then my friend, you are flinching badly, and need to spend some spare time with dry fire practice.

Also, if your groups tighten up dramatically when you don't know if she's gonna go bang or not, it's because you're being forced to squeeze the trigger properly to avoid the embarrasement of watching that muzzle dance around when all she does is go click. I know. Been thar. And I don't know of ANYTHING that will both diagnose shooting problems - and cure them too - as this little trick. Good luck.

Molly

[JudgeBAC]

Molly, I can't deny an occasional case of the flinches; however, my new load is 265 gr. Ranch Dog (actual weight 273gr) sized .432 19.8 grs of IMR 4227. No leading and one inch groups at 25 yds. The weather has been too bad lately to test at 50 yards.

Also, I'm not convinced that 10 grs of Unique is necessarily a light load.

My .44 bisley shoots great groups with 20 grs. of 2400 and the 240 gr. RCBS gas check.

[MtGun44]

Very interesting. Once again, we see that every gun is a thing unto itself. You can
start with the designs and methods that many have had success with and in a particular
gun, it may be unhappy where many others from the same factory are happy.

Glad you found a solution. I wonder what the issue really was, just to learn some more.

Bill

[JudgeBAC]

Bill, I suspect it was a size issue. The throats measure .430. My .430 size die sizes bullets to .4305. This is what I had leading problems with. At the time, I did not have a .431 die so I used my Lee .432 with the ranch dog bullet and IMR 4227 with great success.

[03lover]

I have loaded the same boolit for over forty years.

My two favorite loads were 7.5gr. and 9.5gr. of Unique. I did get some leading, but not real bad.

When I started loading for my two Rugers in 45 Colt I tried Trail Boss powder as a Cowboy Action, light but accurate load. It worked and there was no leading.

So, I tried the Trail Boss in my Ruger Super Blackhawk, 44 magnum. For light loads and great accuracy, I use 4.5 and 5.5gr. of Trail Boss with Remington No. 2-1/2 primers and get no leading.

If you are looking for magnum pressures and velocities, Trail Boss is not for you.

[Lloyd Smale]

a couple obvious questions would be what alloy are you useing and what lube. Ive shot uniquie in my 29 and 629s for 30 years and have never had it be the cause of leading. At least not if im using a properly fit bullet of at least 12bhn and am keep pressures down to where my velocitys dont exceed a 1000fps. One mistake many make is trying to use a faster powder like unique to get top end loads. But it surely should work for velositys under a 1000.

[BOOM BOOM]

HI,
What one shooter "feels" is light VS a heavey load is somewhat relative.
For me 11grs. of unique behind a 250gr. 44 mag. was my light practice load for many yrs. 20grs. of 2400 behind the same bullet was another light practice load.:bigsmyl2:
So a min. VS. Max load may be a better scal for us to use in load discussion.

Of course the actual load grs. vs. bullet listing as you did in your post is even better.
Curse my failing memory, but I do remember somewhere seeing data ploted in graph form on burn rates & pressure piek(SP) points of various powders vs. time, Unique 4227, & 2400 were listed. Sorry I can not remember where.
But the data is out there somewhere, maybe someone ealse with a better memory can tell us where.