New to group and trying to understand some load data

[powderhombre]

Hello, I'm not really new to reloading. I reload for the 45/70 Gov. Mostly Black Powder, some smokeless. I got a new Italian made .45 Colt 1873 clone I want to reload for. I saw on this site some guys using Unique powder, so I bought some. I am a bit confused about the data I see for loadings. I happened to notice while looking over the Alliant manual the .357 Magnum using a 200 gn lead wad cutter the max load for unique is 6.0 grns for 1015 fps and 33000 psi. The loading for the .45 Colt max load for a 200 grn Jacketed bullet is 9.0 grns for 895 fps at 11 000 psi . The more powder less psi is what's leaving me unsure I'm understanding this data correctly. I do also know that this information is max loads and not be a starting load. with that said can someone help me understand? thanks Al

[Coal Creek Griff]

The more powder less psi is what's leaving me unsure I'm understanding this data correctly.

The big factor here is case volume. The .357 obviously has a much smaller case and hence less volume than the .45 Colt. Thus, when the powder ignites, it is less constricted and creates less pressure.

PS -- Welcome! You'll find a lot of great folks on this site. Many are opinionated and willing to loudly voice those opinions, but good people. I learn a lot here.

[Professor Marvel]

Greetings My Good Hombre

The loading data you cited IS correct!
the simple answer to your question "why more powder, less pressure?"  is ......
.............  SCIENCE .................................  SCIENCE .................................  SCIENCE ....................
welcome to the world of SCIENCE!

yup, I hate to tell you but reloading is a combination of the advanced sciences we loved to hate back in school..

to wit:
- inorganic chemistry
- physics of
     solids, fluids,  gasses,
     advanced exploration of combustion and expansion of gases
- mathematics
- metallurgy

In this case, it is not too complicated, it has to do with rate of combustion ( burning the powder to turn into expanding gasses) and rate of expansion
of the gasses INSIDE DIFFERENT VOLUMES!

.357    26.2 gr H2O (1.70 cm3)

.45 colt 41.60 gr H2O (2.696 cm3)


the case capacity of the .45 Colt is approx 1.6 times the volume of the .357
thus when the powder burns it has MUCH more room to expand into , even when
it hasn't yet moved the bullet.

Thus the pressure is initally lower in the .45 because in this "initially closed system"
the gasses have 1.6 times the volume to fill just to get started.


Once the bullet starts moving the gun is no longer a closed system, because the volume the gasses
have to fill includes first the cylinder, then the barrel.

Then at any point in time one chooses, the volume of the .45 is getting larger faster:

V = π r2 h


example: at 2 inchesfrom the breech ( or, technically the internal head of the cartridge)
the .357 volume = pi * .357 * .357 * 2 = .800 cubic inches
the .45 volume = pi * .452 * .452 * 2 = 1.283 cubic inches

at 4 inches
.357 == 1.600
.45  == 2.566

each time the .45 is still about 1.6 times the volume of the .357, so we can see that
the volume increases "linearly" . That makes pressure calculation a tad easier.

Unless the powder burn rate and powder gass expansion rate is nonlinear! If it
was non-linear ( ie exponential, logarithmic, etc) the pressure calculations get messy
and instead of simple algebra and basic calculus, I would probably be ion over my head.

Technically, we should also take into account the powder space - the space occupied by the powder decreases, as the powder burns, thus increasing the total volume.

But Wait! The good news is, we can rely on ENGINEERING and measure the pressure with tools
and come up with tables of EMPIRACLE REAL WORLD RESULTS!

Oh, those are called loading manuals!

I believe this stuff is covered ( and explained much better) in the "technical" sections of
several of the best Lee, Lyman, and Speer loading manuals .... the parts that everybody skip.

Also, as time goes on, powder companies change formuals or methods of measurement so, load data
can change... for example my 1975 copy of the Lyman Loading book has a number of slight changes
from my 2014 copy...

Thus, it is ALWAYS a good idea to buy and read good current load manuals!

hope this helps!

prf marvel

[Advertising]

[Professor Marvel]

Ah, My Good Griend Grif beat me to it 

and with a simpler explanation, too boot!

thanks Grif 

[Coal Creek Griff]

I couldn't have given the detailed explanation and I forgot the expanding volume. Hopefully between us, we got it covered. 

[powderhombre]

Thank you all very much. Yes it all makes sense now that I understand it. I do trust the manuals but it doesn't hurt to know the why before you pull the trigger.

[Professor Marvel]

It never hurts to ask!
and understanding the physics behind a thing is always useful....

prf mvl

[Coffinmaker]

   Oh WOW   

PLUS ONE too The Perfesser You Betcha.

Butt,  All this Science and Psychics stuff makes my head hurt.  I have found a much simpler existence by switching to a nice Substitute.  Makes no difference the size (Size Does Matter) of the container, nor the specific volume of the projectile, simply add propellant until it touches (touchy feeler stuff) said projectile (no excess space allowed) and crimp said projectile home (Scrunchy Stuff).

Although I do understand that Science and Physics stick the ugly heads into everything we do, Einstein said we don't have to know or remember anything that is written down.  Just remember where you put the Writtens.  Burma Shave

Hide and Watch

PS:  Drat, Almost forgot.  We ALL know a "POWDER ROOM" is names for the space where we stash our Explosives.  So, how did a slightly enlarged domestic latrine ever become known as a "Powder Room."  That is the KEY QUESTION

[Black River Smith]

Professor Marvel did a great job of explaining it.
I will try to put it in simpler lay terms.  The general Ideal Gas Law Equation we learned in high school is PV = nRT.  P is pressure; V is volume; n is a constant; R is mass of material burned and T is temperature.

Your question and most of our concerns we are only interested in P and V.  So the eq becomes P = nRT/V.  This then become easy to rationalize.  If the volume of the container is increased from 1 to 2 times it original size then the P is reduced by 1/2.  P = (1x1x1)/2 = 1/2 or 0.5.  In the next example, If the V of the container is reduced by 1/2 or 0.5 then the P goes up by a factor of 2.  P = (1x1x1)/0.5  = 2.  This just based off of generalities, but the ideal result is 'TRUE'.

The bottom line is don't double charge a given case.  The other would be don't compare two different size cylinders(casings) in the same light of thought.

Hope this helps you see see the affects.

Another example would be - take 8 grains of Unique and load it into a 45Colt casing.  It will maybe fill to 1/4 or 1/3 the casing for factory equivalent velocities.  Now take that same 8 grains and load it into a 0.357 casing and it will fill it to the bottom of the bullet or even overflow the casing.  Which one would you think would be correct to fire?

[powderhombre]

Black River, now see you went and opened my brain into a new direction. The 8 grains in a 45 case will maybe fill 1/3 to 1/4. After reloading Black Powder for the 45-70 I am so used to filling the case and compressing enough to seat the bullet that I get a little jiggy with the idea of leaving any air space inside the case. Reading about detonation just makes me even more concerned. I would suspect the use of fillers is a big no no with smokeless. Although I suspect, as I haven't loaded anything yet, that big honkin bullet will eat up a large amount of room in the case to meet with the powder when seated properly.

[Black River Smith]

Sir,
I started reloading back 30 years ago.  I started with smokeless and I read and re-read a lot of sources before beginning.  I started loading 45Colt and 45/70 with Unique.  But I learned about both cartridges and the powders and weights for each and bullets in each.  I stayed with traditional bulllet weights and designs so that was constant.  I also went with just factory velocities for the 45Colt.  In the 45/70 I stayed with minimum velocities for a Trapdoor design.

I loaded smokeless for 6 years then I moved to BP subs for everything for next ~18 years.  That was a new learning experience as you listed in your 'air space and compression' statement.  But I learned about the differences between smokeless and BP to understand the WHYS before beginning.  I then devised an approach to loading BP that worked for me and used only one bullet weight and design for several, several cartridges.  I then created my own scoops for the only 'sub and grade' I used for each.  That was the only way I knew to stay constant.

Now because of not shooting CAS outside, I have gone back to loading only (mainly) smokeless.  At this time I did question about the use of a filler, powder positioner plug (Kapok/Dacron).  So ,I read and re-read again.  I have personally decided to not use a filler material.  Instead I went to a powder that would maybe fill the case more but still stay within the reference manuals (Lyman's) guidelines.....Always follow the references for safe use for the firearms manufactures specs.  That is my approach but there are a lot of people that do use fillers.  Read and decide for yourself of what the reference manuals advice.  Sometimes they do give load with a suggested filler.  Very Rare though.

I am not an Elmer Keith type person.  I stay at what is claimed to be factory velocities or just slightly above for any pistol cartridge.  For rifle cartridges of large calibers, I like staying in the 1200 to 1400 FPS range.  That is true for 30/30's, also.  I mainly shoot lead in almost all the cartridges because they are CAS 1800's design firearms.  I am not a hunter.

One last comment for you about your statement ---"Although I suspect, as I haven't loaded anything yet, that big honkin bullet will eat up a large amount of room in the case to meet with the powder when seated properly."   My comment to you is --- The larger the bullet the less volume the 'CLOSER IT COULD BE".  It depends on the volume of powder you added as your load.  The powder sits horizontal on the bottom of the case in the chamber.  All the excess space is what creates an issue.  'FOLLOW THE MINIMUM LIMITS'  in the reference sources also...

It is fully evident that you are doing your reading and are being precautious.  Don't blame you about not want to make a serious mistake.  It's the best approach.  Read more and you will get comfortable about what to do and what to trust.

There are a lot of knowledgeable people on here that will help.

[Black River Smith]

Sir,

This is a P.S. to my previous posting.  You do not list the type of rifle or levergun that the 45/70 is used for.  But I would suggest you go down to the other forums like the BROW (Buffalo Rifles), the 1876(45/60 loading data sticky); the WIN 1886 and the Marlin forums just 'to see' the the different powders and load volumes and techniques others have stated that they use.

Just for the exposure and knowledge.

[powderhombre]

Thank you Black River. The 45-70 is a Pederosoli 1874 sharps I like you, like to keep this traditional. I've been on the BPCR web forums and have experimented with lots of loadings. I invented a reload target recorder. www.powderhombre.com Now I just got into the .45 colt and of course messing around with the PB for it as well as using the unique.

[Trailrider]

The first and most important rule is READ AND HEED THE LOADING MANUALS!  I have been loading for the past 60+ years, almost exclusively with smokeless powder, and a lot of my experience is with the old black powder (BP) cartridges.  The best handloading manual for these cartridges is the Lyman 49th Edition and the data from Hodgdons (online...although they do put out an annual manual).  A word of caution about minimum loads.  They can produce some problems that can create HIGH pressures! I would start about 10% higher than the lowest listed loads.  If the maximum recommended load is 9.0 grains and the minimum is 6.0 gr., the range is 3.0 gr. Ten percent of that is 3.0 x .10 = 0.3. Add that to the 6.0 and you get 6.3 gr.  That will vary with each type of power. ALWAYS roll crimp the mouth of the case firmly into the crimp groove or a grease groove on the bullet.  This gives the powder time to build up pressure to the level where the powder is burning stably.  If you get hangfires (delayed ignition), stop shooting that load and increase the powder charge a grain (1/7000 lb) at a time. 

On the subject of "detonations".  Technically, there is no such thing in small arms.  HOWEVER, there can be conditions such as if the bullet jumps out of the case and into the forcing cone of a revolver before the powder starts burning stably.  If the bullet stops in the forcing cone, the pressure will build up to the point where it can split the cartridge case and the jet of hot gas can burn through the chamber until things come apart! The way to prevent this is CRIMP! CRIMP! CRIMP! And be sure the case is sized enough to provide good resistance to the bullet moving.  NOT trying to scare you, Pard! But good loading techniques will be very satisfying. 

Oh, BTW, if you do load BP, remember NOT to leave any airspace between the powder and the base of the bullet!

ALWAYS ask questions! 

Welcome to the campfire, Pard!  Stay well!

[greyhawk]

  Oh WOW   

PLUS ONE too The Perfesser You Betcha.

Butt,  All this Science and Psychics stuff makes my head hurt.  I have found a much simpler existence by switching to a nice Substitute.  Makes no difference the size (Size Does Matter) of the container, nor the specific volume of the projectile, simply add propellant until it touches (touchy feeler stuff) said projectile (no excess space allowed) and crimp said projectile home (Scrunchy Stuff).

Although I do understand that Science and Physics stick the ugly heads into everything we do, Einstein said we don't have to know or remember anything that is written down.  Just remember where you put the Writtens.  Burma Shave

Hide and Watch

PS:  Drat, Almost forgot.  We ALL know a "POWDER ROOM" is names for the space where we stash our Explosives.  So, how did a slightly enlarged domestic latrine ever become known as a "Powder Room."  That is the KEY QUESTION

I imagine you have an almost unprintable answer to your question - could be fun to see it .....................

[greyhawk]

I imagine you have an almost unprintable answer to your question - could be fun to see it .....................

did ya ever read "The Specialist" by Chick Sales ? Goes in to infinite detail about dunny (privvy) building ina olden days - little short book

[powderhombre]

Thank you Greyhawk for the tip on the Lyman book. I am pretty comfortable with BP. I always use an SPG cookie on top of an over powder wad and calculate the bullet seating depth and use a Lee factory crimp die for a good crimp. I do not want a chain fire! I'm getting there on the smokeless. The only questions I have is sometimes the bullet you have is not listed in the manual. Just as an example. The manual may have load for a 230 grain bullet and a 255 grain bullet but for some reason maybe you have a 200 grain bullet. should you not use it or is there a formula to compensate for the extra space(air) in the case? Or what if the loading calls for a jacketed bullet but you have the same bullet weight but it is cast. Sometimes these variables cause doubt with the smokeless where as with the BP they are not as critical where safety is concerned.

[greyhawk]

Thank you Greyhawk for the tip on the Lyman book. I am pretty comfortable with BP. I always use an SPG cookie on top of an over powder wad and calculate the bullet seating depth and use a Lee factory crimp die for a good crimp. I do not want a chain fire! I'm getting there on the smokeless. The only questions I have is sometimes the bullet you have is not listed in the manual. Just as an example. The manual may have load for a 230 grain bullet and a 255 grain bullet but for some reason maybe you have a 200 grain bullet. should you not use it or is there a formula to compensate for the extra space(air) in the case? Or what if the loading calls for a jacketed bullet but you have the same bullet weight but it is cast. Sometimes these variables cause doubt with the smokeless where as with the BP they are not as critical where safety is concerned.

Sorry for causing confusion here - "The Specialist" is a little book about building outhouses - that was meant for Coffinmaker after he posted his bit about the powder room (an indoor outhouse) Aussies call it the dunny - some people in the north call it a privvy .......................

Lyman ? twerent me .............

Smokeless powder ?? I have an extravagant habit - I like to use a smokeless load with a slowish burn rate for the case in question - usually we can get a bit more velocity for equal or lower pressure - and - it makes it impossible to double charge a case. The downside is powder costs more - so its tempting for guys that shoot a lot to use hot stuff like bullseye and Red dot - fast burning powders that take much smaller charges to get to workable velocities. Downside of that game is - man you can get in trouble quick - double charge a case - even a glitch in the reloading process and a grain extra goes in - or change up to a little heavier boolit and assume the same powder weight will be ok ? Once you get near the top end of safe, pressure spikes real fast with these pistol / shotgun rate powders - no spare room for fools there.   

[Black River Smith]

Since your 45/70 is a Sharps design, it would be sacrilegious to use 'Smokeless'.

[greyhawk]

Since your 45/70 is a Sharps design, it would be sacrilegious to use 'Smokeless'.

I agree 100% - only have a couple guns that get smokeless anymore at my house (working guns, for pest critters)  All of my fun guns get black powder (or a couple get a little duplex load of black over smokeless)