Reducing cartridge powers

[stuartyboy]

Hypothetical question that arose from another thread..

If you wanted a reduced power shotgun cartridge for close range quiet work could you download an existing factory made shell? Ie instead of buying all the components and tools required to load your own cartridge, you opened up existing cartridges and incrementally removed powder and tested the various cartridges over a chronograph until you got the required speed/energy?

As I say, its hypothetical and will help settle an debate. I realise with metallic cartridges you can get issues with powder detonation but is it safe to do so with a shotgun cartridge? I'm thinking if you only reduce the powder and everything else stays constant, pressures should remain safe?

[Guest cookoff013]

No. What you talk abutt is very dangerous. Do not do it.

[stuartyboy]

Yeah, it was purely hypothetical, a subject that came up. Thanks for your answer, looks like I stand corrected

[Flyboy1950]

Definitely do not do it.

Pressures can go dangerously high just as easily with a low powder charge as a high powder charge.

[Guest cookoff013]

It's to do with the peak pressure. Reduce the load and it won't burn great, the energy drop off would be extreme. At some point it may not leave the barrel right. It would either do really inconsistent. An or failure to clear.

[Continental Shooter]

It's a dangerous practice and not one to be done with a chronograph. There are certain exceptions but all require buying new components.

[stuartyboy]

Thanks guys

[chris1961]

Don't mess about follow tried and tested load data you only get it wrong once

[rovercoupe]

Definitely do not do it.

Pressures can go dangerously high just as easily with a low powder charge as a high powder charge.

Can anyone elaborate on this a bit more? Is it just as simple as less powder equals less surface area which can cause a faster burn and cause a spike in pressure, or something else?

[Stonepark]

It is a hang over from rifle cartridges with a fixed volume.

 

A cartridge with full powder load burns as there is limited space and the pressure rises in a controlled manner, a cartridge with half powder load and half air space can detonate into the air space providing a shock wave instead of a smooth pressure increase.

 

However in a shotgun cartridge the main risk is a failure to clear the barrel due to a under powered load resulting in a dirty burn (incomplete combustion due to not enough pressure for a clean burn) or rarely a hang fire (no or partial burn and unburnt powder potentially smoldering - you tip barrel up and remaining flakes start burning again and could possibly get a second burn resulting in a discharge in an uncontrolled direction or if you have broken gun open, cartridge case fired back at you.

 

Hence always wait at least 30 seconds before opening gun after a non detonation or squib.

[Salopian]

Stonepark,

You appear to have far more knowledge on this subject than I .

Could you explain a little more about 'half air space' please ?

If you load half the powder charge and compress the wad down onto the powder , where is the air space?

Years ago , before the availability of the various powders now available to us , commercial manufacturers produced 'light loads ' which actually had 12 to 14 grains of powder compared with their normal loads of 20-21 grains of propellant , both these loads worked and I am not aware of any disasters .

[TIGHTCHOKE]

Ian

 

Stonepark's first sentence states "It is a hang over from rifle cartridges with a fixed volume."

 

In a rifle cartridge of fixed proportions there would be an air space in the case if the powder charge had been reduced.

 

In a shotgun cartridge, as you say "If you load half the powder charge and compress the wad down onto the powder, where is the air space?"

 

There is no "air space."

[Guest cookoff013]

It is a hang over from rifle cartridges with a fixed volume.

 

A cartridge with full powder load burns as there is limited space and the pressure rises in a controlled manner, a cartridge with half powder load and half air space can detonate into the air space providing a shock wave instead of a smooth pressure increase.

 

However in a shotgun cartridge the main risk is a failure to clear the barrel due to a under powered load resulting in a dirty burn (incomplete combustion due to not enough pressure for a clean burn) or rarely a hang fire (no or partial burn and unburnt powder potentially smoldering - you tip barrel up and remaining flakes start burning again and could possibly get a second burn resulting in a discharge in an uncontrolled direction or if you have broken gun open, cartridge case fired back at you.

 

Hence always wait at least 30 seconds before opening gun after a non detonation or squib.

 

the issues that are discussed here can happen, the problem with generalising the whole subject its very polar. where powders have a different burnrate, means different powder can use the extremes of the pressure envelope. comparing say, A0 to ba10, i can tell you that one of them is an absolute animal, the other is quite bland indeed.

the airspaces that are discussed are the compression sections in the wadding, for loads to work, this void (compression section) needs to have gas volume delivered at such a rate that will squash the compression section, deliver the energy to initiate movemernt of shot and to overcome the crimp. whilst doing all this the wad is fireforming in the hull compressed to the chamber. its having the energy to overcome all these and in a consistent manor.

reducing energy input or increasing this volume really causes diferences in pressures.

i did an experiment ages ago, there were alot of experimemts i did, i had a single powder charge, and i loaded up 2 shells one that was 32g steel and another 32g niceshot. when the data came back from the pressure barrel there were very noticable differences....

 

steel- no compression section, doubled the pressure of the non compression, extracted all the power from the load.(plateauing the powder power efficiency) because steel has low density its good for extracting energy

niceshot, half the aforementioned pressure, less speed, energy extraction was mediocre, but is right in the powders comfort zone.

 

this comes to my very important second point, is wadding size and cartridge length. 65mm loads have less volume to play with, but offer great efficiency where powders are involved, the only duff point with the 65mm is the powder / loads available means 32g maximum loads (to a point, with speed) reduced length means less expanion of the compression section. now this also takes me to the wadding, fibre vs plastic, while they reload the same (thats a 24g lead load ) i had a punchy good load with plastic, and with fibre just straight over pressure.

fibre = less volume to play with.

the add 10% rule for fibre is to try and keep the speeds similar. but with every change pressures change, efficiency changes... (nb, both loads were 70mm)

 

with my ba10 powder i`m pretty sure it can be pushed quite low pressure, i think it was burning and below 300bar with one test. thats peanuts. really.

[neutron619]

Years ago , before the availability of the various powders now available to us , commercial manufacturers produced 'light loads ' which actually had 12 to 14 grains of powder compared with their normal loads of 20-21 grains of propellant , both these loads worked and I am not aware of any disasters .

 

Eley still do this with their subsonic / supersonic versions of the "Extralong" 18g/#6 .410 cartridge.

 

As for rifles, this is why Trail Boss was invented - high volume, low density powder (and fast powder at that) to fill out the airspace left by very light loadings. Think gallery rifle at 50m, shot with subsonic ammunition out of rifles designed for normal velocity.

 

The detonation theory (no-one's proved it, but I can see how it would happen and I'm convinced that it's possible, but rare) basically says that if you're shooting a large cartridge with a 50% fill of slow powder horizontally the primer flame will travel over the surface of the powder and ignite it all at once. Cue massive pressure spike and exploding rifle. In a full cartridge, the primer flame hits a smaller area - the cross-sectional area of the case - and the powder burns progressively, from bottom of the case to the top. This is much slower and generates lower pressures by comparison.

 

The complication is that the pressure generated by primer flame itself will push the powder towards the front of the case, immediately behind the bullet, which reduces the likelihood of detonation occurring, because you're back to igniting powder over the cross-sectional area and it burning progresively again. This is why, although many people manufacture quite risky subsonic rounds (i.e. using normal powder, rather than specialist powders like Trail Boss or pistol powders) for their rifles, very few get blown up doing it.

 

The final thing to mention is that detonation is generally an issue with slow-for-purpose powders only. The reason for this is that with a fast powder, whilst you always have the possibility of going over pressure limits, fast powder burns up quickly, produces its gas and gets the bullet moving relatively quickly.

 

The following is a gross simplification, but you can imagine it this way:

 

The primer flame passes over the top of the powder in the half-filled case and ignites every flake in the topmost layer at once. With a fast powder, by the time the burn reaches the third layer of flakes from the top, the first two layers are burnt and causing the bullet to move down the barrel. With a slow powder however, those first two layers of flakes are still burning, then you ignite the third, the fourth, fifth, etc. This means that rather than having a certain quantity of powder burning at any one time - say, two layers of flakes working outward through the powder from the point of ignition - until it's all burned up, you have essentially all of the powder in the case burning at once. The contribution that each flake makes to raising pressure is therefore all delivered at once rather than gradually. The gun then goes bang in precisely the wrong way.

 

For the reasons given above, however, I don't believe this is relevant in shotguns - but I would not personally fiddle with powder charges in this way.

 

Edit: for spelling.

Edited September 12, 2017 by neutron619

[rovercoupe]

The knowledge you guys have is amazing!

[Guest cookoff013]

The knowledge you guys have is amazing!

 

yeah, and the important thing is, we are still learning. learning from experimetal loads, big projects, proof runs and patterns. i think its very much known that i am really only interested in that 1" reading, for you metric or CIP guys thats the 25/30mm pressure reading at the chamber,. the rest i`m not even bothered with. the pressure barrels are interesting, they only tell truths, or half truths, they never lie.

 

the one thing that has always fascinated me is the bang. it is amazing what happens, i ended up doing alot of weird stuff with payloads to try and work out some things, the experiment was that volumetric reloads...

some great things came from it, ok, to confirm what is already known.

-increase payload, means pressures go up and vice versa, probably due to the initial extra energy required to move payloads /payload increments.

-energy outputs increas to a point, then it cant extract any more.

- *compression sections change pressures, changing efficiencies*

-there probably is a power band right in the middle of the ranges.

-pushing a load with a slightly larger payload actually had the highest energy output in that assay. with safe pressures.

-when i pushed a load with the highest payload, the pressures really wobbled, wobbled so much it just failed. (think of a 32g powder pushing 42g of shot)

-with that failed 42g load i hit the exact speed supposed to 1210fps. litterally 10fps off expected.

-reloading is fun

[Continental Shooter]

 

yeah, and the important thing is, we are still learning. learning from experimetal loads, big projects, proof runs and patterns.

 

Some will try to make you believe that you can do that by word of mouth ... nope! There is only one good, knowledge, and one evil, ignorance....

 

Cook is 100% spot on!

 

As they say: Wonder is the beginning of wisdom; only by studying on real books (and by that i mean recognised authors and physics books) and doing actual test to prove your theories you will understand the phenomenon and learn the dynamics.... and even then, you need to keep studying and testing. The only true wisdom is in knowing you know nothing...and take it from there

 

All components are affected by production batches; it's somewhat common for certain powder to change their burning rate from one batch to another, and so do primers (with CX1000 being the worse); even the polymer used for hulls can change and with it the dynamics of your load... so, expect the unexpected when you put your tests through the proofing barrel ...

[Guest cookoff013]

 

Some will try to make you believe that you can do that by word of mouth ... nope! There is only one good, knowledge, and one evil, ignorance....

 

Cook is 100% spot on!

 

As they say: Wonder is the beginning of wisdom; only by studying on real books (and by that i mean recognised authors and physics books) and doing actual test to prove your theories you will understand the phenomenon and learn the dynamics.... and even then, you need to keep studying and testing. The only true wisdom is in knowing you know nothing...and take it from there

 

All components are affected by production batches; it's somewhat common for certain powder to change their burning rate from one batch to another, and so do primers (with CX1000 being the worse); even the polymer used for hulls can change and with it the dynamics of your load... so, expect the unexpected when you put your tests through the proofing barrel ...

 

tell me about it.

 

the biggest problem i have is designing a load or an assay that will say something. for instance. when i did that volumetric test with nontoxic shot, it is actually a payload test, whilst keeping the wadding the same height the resistance or friction of the payload height is the same. and so is the compression section. meaning any results i had for the whole lot were comparable. whist if i had done a weight comparison the 32g steel load wouldnt have fit and the assay or tests would not be comparable. when i did this it was an out lier that i knew for the efficiency test.that whole assay toos ages to set up. it had a pilot run too. so about 12 proof runs already. the great thing about it is i kept batches of stuff to just do that. same everything. and infact. the data whilst individually is "just data" just like everything else. but the big picture of all the firings is pretty amazing really.

 

i still think its time that certain misconceptions are stamped out, i was told that vectan AS is not suitable for steel shot, but in reality and the amazing CIP regulations, its not far off being a great 24gram steel powder. in which there is data for and i ramped it up i "touch". but it only just failed cip test. infact i`m going to re-visit that test again.

 

i`ve a few handful of projects to sort out and i`m guessing that december is when the testing will be done. i`ve just bought a ton of components,... just to hopefully push some boundries.

 

i did study books for a while, and the caveat is always true, everyone has an opinion.

what i wanted to wade through is the rubbish and some safety concerns,

 

whilst increasing payload did increase pressure, from 24g to say 42g the pressure increased quite a small amount really. that was with a slower burning powder than i`m used to (A1). the warnings are quite extreme really.

thats not to say every load can be increased in payload and still be safe. clearly not.

 

the other thing i kinda learned, every powder charge has an optimal amount. it bangs with silly consistancy. its finding this. and it can work with many payloads. even abnormal ones, and still be safe.

 

the one thing that really and i mean really impress me, is that ITX10 stuff, i either hit a payload node but that energy extraction / energy produced was pretty good. i`ll be testing this stuff some more.

 

the tests i do tell me things. they tell me a story. i can read that story, if i change one component, i change a chapter, the story might change. who knows?

i`m having alot of fun seeing the results. and i personally want to thank those who do share reloads / test sheets..

 

my next reloads and tests will probably be a mixture, of weird stuff and some bread and butter reloads. i`m getting some csb5, 3" hulls and wish to do some steel reloads, lead and some other stuff.

i got a massive list.

[Continental Shooter]

 

tell me about it.

 

the biggest problem i have is designing a load or an assay that will say something. for instance. when i did that volumetric test with nontoxic shot, it is actually a payload test, whilst keeping the wadding the same height the resistance or friction of the payload height is the same. and so is the compression section.

 

As you know i never went close to non-toxic reloading. That assay you done open up a whole new world for me. Among the non-toxic, that ITX-10 was a revelation and helped me prove wrong lots of misconception on other forums (mainly continental ones). My 20ga 27 g & 30 g with decent speed and safe pressures aimed at shooting on old guns without the aid of steel wads are very nice; a twitch or two and they will be right up there with the BPI loads. When i submitted the results to them they were quite impressed, especially with the way the 800X performed under the 27g (while they max they load is 24). They noted though that speed was on the lower spectrum of what they consider 'lethal'; however, with such a low pressure there is a lot to play with.

 

A real success at the first attempt and all thanks to that test.

 

Tough, if i didn't have the base knowledge to read that story; probably it wouldn't have said anything to me ... as it didn't to loads of people in the forum; hence the little attention given in the forum even though, for home loaders it was a ground breaking test.

i did study books for a while, and the caveat is always true, everyone has an opinion. yes, but they give you different perspective; with a base knowledge of physics you can then ***** which one is more suitable to you and take it from there to go one and write your own story

 

whilst increasing payload did increase pressure, from 24g to say 42g the pressure increased quite a small amount really. that was with a slower burning powder than i`m used to (A1). the warnings are quite extreme really.

thats not to say every load can be increased in payload and still be safe. clearly not. With slower burning powders the problem is with lighter load as they are designed to cope better with heavier loads. Had you try to increment on AS or CSB5 ... you would have probably noted an esponential increas between the 24g and the 42g

 

the other thing i kinda learned, every powder charge has an optimal amount. THANK YOU been bangin on about this for some times

 

my next reloads and tests will probably be a mixture, of weird stuff and some bread and butter reloads. i`m getting some csb5, 3" hulls and wish to do some steel reloads, lead and some other stuff.

i got a massive list.

 

deffo looking forward to the results

[Guest cookoff013]

on a second note of "that" test, i screened lead vs steel first and noted the same changes, in the 70mm even if the pressure was low. i extended the hull crammed in some more powder then repeated it with all nontoxics (except t15-18).

 

but i`ll still say that that itx even as it is is my new best friend, it extracted energy well. it nearly outclassed the 36g lead load.

 

and lead, in all honesty as a shot type can produce higher pressures than steel !

 

on the initial firing it just sits there and absorbs more energy before the crimp pops.... it isnt too far from hevishot 12 ! if only there were more lead data in ninnytonic wads.