Lead vs steel internal ballistics

[Guest cookoff013]

Ok guys,

i`ve been researching into steel shot cartridges for quite a while. The data i got was mainly size and weight data, Ballistic coefficient data, time of flight, energy transfer data.

most of these datasets are single pellet models, where a steel or lead pellet starts off at "x" feet per second travels "y" distance, and retains "z" energy which is "a" ftlbs or so.

The most interesting part of the whole research is that the data or information is nearly always about external ballistics, I can agree that it is the most important factor when load

application or performance is discussed.

I have been sending off shells for testing for quite a while and the internal ballistics has greatly interested me. I am usually less concerned about the external ballistics of lead shot.

it has been a traditional shot material, and a great performer (for a century at least), everyone knows about shotsizes, effective range and what speeds most shells run at.

This brings me to my very next questions, what happens internally when steel is used? compared to lead? that is a fantastic question. infact thats a question thats been buzzing around

in my head for ages and i`ve been thinking of tests too assay the question, so that some answers can come from it.

first lets compare steel and lead, steel having a density of ~7.8g/cc and lead about 11.4g/cc so there is a huge discrepency between the two shot materials. so from a volume point of view

we can only compare certain loads, to keep the 12/70mm format, 32-36g steel loads start to become 12-76mm and thats isnt right for the comparison tests, if we then use 12/76mm as a model then we are

clearly talking about 50gram shot loads of lead vs 32grams of steel. in all honesty i have no interest in such large lead shotloads. for that, some serious powder choices come into play and

its something i really didnt want to base a solid test on, an ultra-slow burning powder with a payload that really doesnt have any value where "sporting cartridge" applications are concerned.

i created a differential calculation between the two shot types, it works out like this, 32grams of lead shot is "equivalent" to x grams of steel shot (steel shot is always lower density, they both occupy the same volume in the shell.)

i can either weigh alot of shells, or i can just simple calculate. I prefer to calculate, then maybe back up the information with a few weighing excersises.

Second i needed to make a decision of what wad i am willing to use, as its a steel vs lead comparison it needs to be steel rated for the steel shot because i can easily fit lead into a steel shotcup.

that way the test barrel is protected, if not "over protected" for the lead shot cartridge. i selected the gualandi tubo 24 for the test, because it is a quality strong sporting wad. i havent a clue how this test would pan out

but essentially its selection was less scientific than you think.... i had a bag of them to use up, and i was also testing a 3" steel version.

so thats it, the numbers boil down to 24g-25g steel vs 35g-36g lead.

The powder selection was another stickler point. Powder for 36g lead loads means some relative slow powders, and 24g steel powders could mean anything from vectan AS to alliant steel.

i cross refrenced a whole lot of cartridge reload data and it was coming up more and more that i should try a powder that is traditionally for lead 32g at 1300fps.

i selected a powder and fit enough in the hull to provide a good crimp. (these tubo24s are quite tall.)

by this time i happened to come across a post on another forum. where the test has already been partially done. the model they used was with the helarco wads. they are available, but not something

i wanted. i`ve used them before. The initial test was using a clay shooting type powder for steel shot. but there was data available but from a different source. hardly ideal for a definitive test of lead vs steel shot.

i looked again and saw that a common powder thats for 12-70mm-32g lead -1300fp

so the model i selected would be 36grams of lead vs 24grams of steel shot, so i`m kinda happy, because i`d like to re-visit the 24g load i once did, along time ago.

so thats virtually it. nearly done. so thats the test.

i weighed 40 charges of powder put the wad in and put them in a bag. randomising them and then selecting 10 for each test. i then charges 10 with 36grams of lead, and the other 24grams of steel shot, (#6 lead and #5 steel).

after they were charged with shotmedium they looked near identical, crimped identical.

before i put them in there bags to be sent off i checked them over with a magnet to assure me there were no mixups.

i sent them for pressure testing.

so what i sent off was

12-70mm

Primer

Powder @ x grains

tubo24

24grams steel or

36grams lead

crimp

the results came back.

lead produces higher pressures, slower speeds

steel produces lower pressures, faster speeds

because i sent them off for a pressure cip test, the results are geared to a pass / fail criteria, whereas i`m more interested in the raw data, and the "neatened up data" (thats the data that ommits clear outliers).

The results were very interesting indeed, the shells them selves were nothing to write home about, but the comparison of the loads raises some interesting points...

1, steel by volume gives lower pressures than lead about 120bar less, or 1/5 or 20%. that means that lead sits there just slightly longer than steel, either before or after the crimp pops. i think the weight is why it has a higher pressure, not the volume. the shot in the chamber acts like a big metal plug. steel gives lower pressure than lead, i dont know but i think it stops the "steel-set back" theory. that means steel shot is less of a plug compared to lead volumetricly.

2, comparing lead vs steel, lead gave higher pressures (thats the same statement as above).

3, comparing lead vs steel, lead produced a slower load, slower by 40m/s, thats not far off 100fps in old money. so obviously the speeds are not the fastest but there is a clear "lead differential". the steel shot was certainly faster.

4, Notably that the lead loads were actually more consistant all round. both pressures and speeds, maybe its an pressure efficiancy thing.

5, These loads were created to try and disprove a few things. i never managed to do that.

6, Thanks given to underdog, for the banter, this was created to try and prove when the peak pressure is and when the crimp pops, before or after the pressure peak. all it proved is that comparing the two loads, that there is a difference internally....

i estimated the pressures to be similar but i was real wrong. 120 bar difference is 1700psi or so, hardly "alot" there was some variance on both loads. knocking off the outlying data did nothing. so i failed, whether the lead produces more peak pressure in the shell before the crimp pops, i do not know. i could not determine, but there was a difference of lead vs steel

7, steel shells can be made up with relatively fast target powders, i didnt get the results i wanted, infact all the loads i sent off were quite low in pressure, this was the slowest powder i`ve been using for a long time.

8, i wouldnt mind re-visiting this, with a load ladder on both sides of steel vs lead, the tests. i also wouldnt mind a different powder, a powder thats more dense really. because the wads were tall, i couldnt fit alot of powder in the hulls, and it produces "lower" pressure loads.

 

[kent]

Good to hear your not stuck in using out dated lead load weights in steel. If the market can be persuaded it's the way to go

 

The rest? Not so sure what the final goal is but lead and steel are so different in how they behave you just need to forget about one and concentrate on the other.

[TONY R]

Fantastic insight there thankj you very much for sharing your findings, Ther lead vs steel pressure debate is a long oft debated subject, and as you have found out by acctualy testing theory its by no means a cut and dried case.

The initial pressure with lead is more the mass of shot dictates that along with set back and defornaty of the softer shot which you would expect but probably not as much, from then on with lead its a steady decline in pressure up to the choke area then atmosphere . , The lighter steel load has initial pressures some set back and deformaty of shot then it has a short period of highr pressure again as the deformed steerl pellets recover their shape.

This spiking of pressure can vary quite a lot is shot size and shot finnish sensative. Polished shot at higher velocitys can put pressures over where as a normal steel pellet in the same load can be in spec and safe.

Bore size and certain pellet sizes give strange over pressure signs in the recovery period typical signs arer streaking in front of the forcing cone area and unusualy over wrecked wads.

Interesting you should post this up rigght now, i am in the midst of copper shot testing and what i am finding with this shot is it has less pressure spiking on recovery as you would expect given its nature, but its low i mean unexpectably low but initial start pressures are closer to lead than steel so a more progressive powder than typical ITX loads ( similar to copper MASS !) is acctualy needed i am finding.

Brilliant insight though on your part much apreciated .

[Guest cookoff013]

i can see copper and sinter tungsten and other shot types being very interesting. i was going to add to it but think i`ll re design the assay, get some copper shot, tungsten then do all shot types and record the density differencials.

 

would be nice to see on some graphs, i needed to get an optimal lead load first, as i can see the tungsten loads going above the lead pressures.

 

incidently the differential of density between lead and steel is about 0.695 (or thereabouts) 36g lead x 0.695 = 25g steel (both ocupy the same volume.)

[TONY R]

By Toungsten i guess you mean HW 13 HW19 RIGHT? Or are we talking Matrix here.! either way you are right it makes more pressure than lead PR .

With Matrix i never put much through the pressure gun and what i did was 5s from striped loads i put 1s in instead .

I did not run no 2 port unlocked just port 1 for initial and matrix was high higher than lead on pressure all things being equal. , i will have some records i can look out if you want them, but they showed me enough to put me off trying too hard to make matrix go faster, it was too soft in fact very soft .

HW 13 & HW19 i have not tested many loads i dont use it much in 12s mostly tens but no test gun for 10ga. What little i have done was with 3 and 3.5 inch loads of HW13 , i did notice suden jumps in pressure with it and put that down to mass low volume and hardnes and just stuck with loads that were well known from the states, i gave up trying to get it quicker for now in lighter loads.

 

Dropping back on steel in lighter loads, i think the biggest draw back in steel performance at the moment is powder charecteristics, Without going into too much on.. this and that.. powder does this when? Your lighter loads of steel shot at lower prerssures initialy couyld have beern down to powder charecteristics and primer briscance due to the low weight of shot, some of the more progressive powders need a hot ignition and a simple change of primer can make a big difference both to pressure and speed. Prime examples of this are some of the old white box winchester Primed loads in old RSI data these along with changes in A steel leave many of those lods a job for an educated guess shredly termed Modified. By some of the americans who debate these loads.

I have named a powder type and i A steel but realy it can be lots of different powders and the burn rates of them can be quite away from what you would expect with steel and esspecialy light loads in steel.

Just a thought on your point no *8 how about LONGSHOT do you think that might be a good powder for this comparison. I cant think where it would fail myself.

Edited March 22, 2016 by TONY R

[Guest cookoff013]

i was more thinking about softer sinter type tungsten but i could use any in this system..

i`ve not encountered hw13-19 but i do know they exist, they are a tad too expensive for my wallet really.

i bet those sudden jumps of pressure are due to the "large shot charges" of "very dense shot"

 

i actually used a powder that should have been a solid performer, the 36g lead loads were not "spot on" but were not that far out really. i didnt need all shells to pas 740bar but i did want it to, so i could publish. the data came back too low in pressure, and not worth publishing.

 

i kinda want to stay away from longshot. i wanted to use a faster target powder to show the internal ballistic differences, not have the slow powder mask the changes.

 

i have a powder in mind, and i think it may be very good for this application. (its more dense so can fit more in a 70mm hull / tubo24 wad) thats the catch 22. i wanted to have a common powder, and have decent data with all the shot types, steel lead, tungsten, copper?, sinter hevi, and the "other"

[TONY R]

I can see where Longshot could get in your way but it is a wild child right enough. poke Longshot with a big stick IT BITES!.

In 70mm guess multi hull and that wad M92S or if too bulky for your tastes G3000, good thing is about those two they will get you sub 740 bar with everything G3000 might strugle with lead or ITM initialy but not by very much. Practicaly M92S How about that. ?

[Guest cookoff013]

these are all powders i cant get.

i didnt want 1500fps + loads, or powder heavy loads.

 

now i know what i know know, the powder type wasnt that bad. as i have said it is a fast type powder, for target and game loads.

now i know how things behave i shall re-do it all with a new powder in the same range, 32g lead loads at 1300fps nice. i just need a denser powder.

 

if i were to go to a different powder, then it would be 3" 30+ grain powder charges. i`m not interested in that. to me 30+ grain powder charges are a non starter.

[TONY R]

A1 - 36 would do it. But dont see it since charlton stopped doing it in the 90s. Green dot its a bit special is green dot brezny had a lot of time for green dot. Jumping to herco you are in danger of its slower nature getting in the way. You would get the same with Vectan A0 which is a bit too bulky anyway. GREEN DOT? About 18 to 22 grains.

Edited March 22, 2016 by TONY R

[Continental Shooter]

Tony,

 

Where did you get M92S??? i want it, i really missed it for my geese loads...

 

Cook, i know the nature of your tests, as discussed, but i am still of the idea that whit a slower burning powder, maybe in 12/67 or even 12/65 you could come up with something you like without the 30 grain powder charge.

 

I am thinking Tecna N, PSB1, 800x should all get you there with low charges, also with A0 you could push 28 gr easily with less than 30 grains.

 

I am sure if you could do the ogival closure, you could have lots of fun! I am looking to get one here but need some one with a lathe to get the stand built at the exact angle ...

[TONY R]

Tony,

 

Where did you get M92S??? i want it, i really missed it for my geese loads...

 

Cook, i know the nature of your tests, as discussed, but i am still of the idea that whit a slower burning powder, maybe in 12/67 or even 12/65 you could come up with something you like without the 30 grain powder charge.

 

I am thinking Tecna N, PSB1, 800x should all get you there with low charges, also with A0 you could push 28 gr easily with less than 30 grains.

 

I am sure if you could do the ogival closure, you could have lots of fun! I am looking to get one here but need some one with a lathe to get the stand built at the exact angle ...

I would not have a clue where to send you. split a 20kg barrel with two others when we could get it out of a popular cartridge firm on our account before they went stupid. , i used it in a couple of 3/4 and 7/8 loads and a 32 gram load quite regularly, But I started using 381 ( same as lot 12 in the lightening steel loads and sheled the m92s. I still have a couple of killos left.

[Guest cookoff013]

Tony,

 

Where did you get M92S??? i want it, i really missed it for my geese loads...

 

Cook, i know the nature of your tests, as discussed, but i am still of the idea that whit a slower burning powder, maybe in 12/67 or even 12/65 you could come up with something you like without the 30 grain powder charge.

 

I am thinking Tecna N, PSB1, 800x should all get you there with low charges, also with A0 you could push 28 gr easily with less than 30 grains.

 

I am sure if you could do the ogival closure, you could have lots of fun! I am looking to get one here but need some one with a lathe to get the stand built at the exact angle ...

 

The slower powder might work and think the 67mm might work. But I want 70mm.

I did a 3" too and stuffed it with fast powder. The 3" load was safe with room to wiggle. Was good speed too.

I did A0 but was very powder heavy.

That's why I did the faster powder.

Thing is if I change the powder to a slow one, I have to go 70 mm minimum

And relative large powder charges get good speed.

 

Next stage would be more testing. New powder, get that right with lead. Then do +2 grain powder steel, -2grain hevi tungsten.

(Wink wink?)

[Continental Shooter]

looking forward to it )