Do patched bullets bump up into the rifling?

[rayg]

Just curious, but do patched bullets bump up into the rifling like jacketed bullets do because they are fired at higher velocities like jacketed bullets? We all know that jacketed bullets when fired at the higher velocities, even though they are under the groove size, will bump into the rifling where cast bullets at lower velocities do not. Ray

[felix]

Same thing with any kind of projectile. ... felix

[leftiye]

We don't all know that. Jacketed bullets when a thou or two undersized sometimes shoot well anyway, but I don't think they bump up much with smokeless powder. Cast boolits without the jacket - will bump up much easier than any jacketed bullet will - if the pressures generated by the powder are high enough (regardless of velocity).

The best answer I can give you is that paper patched boolits sized to enter the bore will size up IF you use black powder. Smokeless loads usually involve the paper patched boolit being a thou. or two larger than GROOVE diameter and being seated into the start of the rifling (no bumping up).

[Digital Dan]

The type of powder has little to do with obturation. It is pressure and hardness.

Obturation Pressure = 1440 x BHN, or close enough.

[leftiye]

Sorry, the characteristics of black powder involve it being an explosive (whereas smokeless is a propellant and it burns, but doesn't explode). Due to this it (black powder) generates a shock wave (pressure front) which involves very high momentary pressures and causes much more obturation than smokeless.

As you said "or close enough" - what is necessary that the pressure causing obturation exceeds the plastic strength limits of the lead (= more pressure than the lead can recover from elastically) and that the inertia of the frontal parts of the boolit is high enough that this pressure can act against it, overcoming the elastic limits of the rear and middle portions of the boolit.

[rayg]

That's what I meant. Figuring the higher the velocity the higher the pressure. Probably didn't explain that right.
So will lets say will a cast patched 30 cal bullet loaded with 40 grs of I-4598 bump up somewhat like a jacketed bullet would even though it's smokeless powder it still is creating some push/pressures wouldn't it. Ray

[pdawg_shooter]

Sorry, the characteristics of black powder involve it being an explosive (whereas smokeless is a propellant and it burns, but doesn't explode). Due to this it (black powder) generates a shock wave (pressure front) which involves very high momentary pressures and causes much more obturation than smokeless.

As you said "or close enough" - what is necessary that the pressure causing obturation exceeds the plastic strength limits of the lead (= more pressure than the lead can recover from elastically) and that the inertia of the frontal parts of the boolit is high enough that this pressure can act against it, overcoming the elastic limits of the rear and middle portions of the boolit.

+1 ON THE EXPLOSIVE BLACK POWDER. I have never recovered a bullet, cats or otherwise that showed any sign of oburtation with smokeless powder.

[hyoder]

If you cast PP boolits from near pure lead they will bump up with smokeless quite nicely. They will also penetrate well and mushroom well at the other end.

[softpoint]

Just asking here, If black powder produces a higher initial shock wave, or pressure than smokeless, Why can the priming systems be weaker? Even shotgun primers are not good for high pressure smokeless loads. Even the firearms themselves can be of weaker design and construction. Even though the smokeless is progressive burning, if it produces 50,000psi at some point in the bore it seems to me more likely to obturate a bullet than an initial shock of say, 10,000psi?
Again, I'm not disagreeing with anyone here, I'm just looking for info!:drinks:

[windrider919]

I think it has something to do with the rate of pressure increase. A pressure chart of black powder has a spike of pressure right at the beginning but it does not go as high. The highest pressure looks like about 38 K which could be held by mild steel firearms. The pressure curve for generic smokeless that i looked at 'ramp' up to a pressure of up to 62 K. It looks like the pressure curve for smokeless is just peaking at about the time that the BP has dropped most of the way down. Comparing the two charts it appears that BP burns in 1/3 the time of smokeless. Maybe that has something to do with the bump up / obturation effect

[montana_charlie]

Smokeless applies max pressure after the bullet has been accelerating for some period, while black applies max pressure instantly.
Maybe an analogy will help visualize the difference in how black and smokeless accelerate a bullet.

A fast runner can do a mile in four minutes. That's fifteen miles per hour.
Assume you have a car with a seat mounted out on the front bumper that you can ride in.

The car is coming on at fifteen miles per hour, and you start running in an attempt to match speed before you jump in front of the seat. When the seat hits you in the back, it barely nudges you forward. If you were a bullet, you would not obturate from the impact.

Now just stand still with your butt sticking out, and let that fifteen mile per hour seat hit you.
I think it's going to flatten (obturate) something...don't you?

CM

[leftiye]

Probly (possibly) the difference is where the boolit is when the pressure happens - say contained partway down the barrel and after the gas seal has been accomplished (reads cannot expand) versus in the case/throat leade or in the bore, and unsupported?

What Charlie is talking about is the inertia thang - there has to be enough resistance from the inertia of the frontal parts of the boolit that the pressure has something to squash the rear parts of the boolit against.

[windrider919]

When I first started casting rifle bullets I, like most newbes went to the pointed cast moulds. And discovered like all the others that you just don't usually get any accuracy with that style pointed cast. Lots of reasons have been presented but one I remember is "bullet slump" at firing where the lead [unless really hard] does not support itself and slumps down under the acceleration of firing. Unfortunately, it seems to slump off to one side and hence causes an unbalanced bullet / un-accurate bullet. (Other reasons were: CG / CP placement, too short a bearing surface, etc). I read articles in magazines such as American Rifleman and others that 'proved' that this was happenning. So, if a bullet can slump, why not obturate? However, I have had a water bullet trap available for years and have recovered and miked many, many recovered bullets. And my experience is that even lead bullets launched with smokeless powder DO NOT obturate much if at all. even when the nose had mushroomed, the base miked bore n grouve size close to unfired. My experience is not fireside or kitchen table created but actual experience on the firing line and I am one of those "show me" guys to boot.

[Apache]

Smokeless applies max pressure after the bullet has been accelerating for some period, while black applies max pressure instantly.
Maybe an analogy will help visualize the difference in how black and smokeless accelerate a bullet.

A fast runner can do a mile in four minutes. That's fifteen miles per hour.
Assume you have a car with a seat mounted out on the front bumper that you can ride in.

The car is coming on at fifteen miles per hour, and you start running in an attempt to match speed before you jump in front of the seat. When the seat hits you in the back, it barely nudges you forward. If you were a bullet, you would not obturate from the impact.

Now just stand still with your butt sticking out, and let that fifteen mile per hour seat hit you.
I think it's going to flatten (obturate) something...don't you?

CM


ROTFLMAO!!!!!!!!!!!

Now THAT is an excellent description!!!!!!!

[montana_charlie]

I have had a water bullet trap available for years and have recovered and miked many, many recovered bullets. And my experience is that even lead bullets launched with smokeless powder DO NOT obturate much if at all. even when the nose had mushroomed, the base miked bore n grouve size close to unfired. My experience is not fireside or kitchen table created but actual experience on the firing line and I am one of those "show me" guys to boot.
I actually agree with your contention that bullets don't obturate (or don't obturate as much) when fired with smokeless powder. However, I don't see how your bullet trap proves that.

If you had a bullet that was undersize before firing...and still undersize when recovered...that might be called proof of 'no obturation going on'.

But, a bullet that starts out at groove diameter (or a bit more) and does not mike at groove, after passing through the bore, would be a strange result.
If it mikes at only a thousandth or two over groove, you might say that the amount of obturation was very small. But, you would have to explain how the bullet obturated after it left the muzzle.

THAT explanation might require some kitchen table time...
CM

[Lead pot]

This very subject came up in I think I think Hand Loaders Magazine several years ago.

And yes with his tests a jacketed bullet will obturate into the void between the case neck and the throat.
The pictures that where in the artical showed this very plain.

If you stop and think a moment; where can a bullet obturate to if that bullet is already groove diameter??

[felix]

MC, if the freebore plus leade is enough larger than the grooves to make the boolit exceed it elastic limit (permanent obturation) before the boolit is mated back to the grooves, and the grooves do not make the boolit exceed the elastic limit, then the boolit will flare back out upon muzzle exit. ... felix

[RMulhern]

Hmmmm....I bin a studyin dis heah problim da las minet or so...and it do seem dat if I takes a item of lead that bees .457" in diameter...and iffen I draps it into a hole whut be plugged off an da hole bees at .458" and then if I sticks a punch into dat hole whut be at just a slip fit into dat hole and I beats the livin snot out of dat punch wif a 40 # maul....dat lead ain't gonna go but to just so fur!!

[docone31]

Thats easy for you to say.

[ExtrahoProeliator]

look at it this way, think of black powder as a Peterbilt and smokeless as a Ferrari. They both have 500 horsepower. The difference is, the peterbilt has more to move with that 500 hp than the Ferrari. If you're in the driver's seat, the inertia from acceleration in the Peterbilt, will shove you backwards, but, the inertia from the acceleration in the Ferrari, will smack you backwards.

Black powder shoves the base or the skirt of the bullet into the rifling, whereas the smokeless smacks it forward.

Hope that helps

Buddy

[405]

These type threads are a good break from the dull tedium of some things we do.

All good stuff so far. I'll throw one more out there. Given the ballistic and physical characteristics of blackpowder is it not possible that the kinetic energy of the forward portion (at bullet base) of a column of blackpowder, immediately after ignition, could play a role in bullet obturation?

[waksupi]

look at it this way, think of black powder as a Peterbilt and smokeless as a Ferrari. They both have 500 horsepower. The difference is, the peterbilt has more to move with that 500 hp than the Ferrari. If you're in the driver's seat, the inertia from acceleration in the Peterbilt, will shove you backwards, but, the inertia from the acceleration in the Ferrari, will smack you backwards.

Black powder shoves the base or the skirt of the bullet into the rifling, whereas the smokeless smacks it forward.

Hope that helps

Buddy

Welcome aboard, Buddy.
Isn't that backwards? BP, being an explosive, gives the spank, whereas the smokeless is progressive in burn. That is why BP bumps up a bullet better than smokeless.

[ExtrahoProeliator]

Thanks Waksupi, I'm glad to be a member of this group.

In response, to your reply to my post, that would be a yes and no answer.
Yes, black powder is an explosive propellant and smokeless is a progressive burning propellant, but, you also have to consider the pressure curve and resultant spike in breech pressure, with respect to each propellant.

Black powder, has a strong, but relatively low pressure upon ignition. Once it is ignited, it has a long, arching pressure curve, much like a bell curve. That is not to say that it can't have a dangerous pressure spike, as there are too many variables involved from one firearm or cartridge. Each firearm is a law unto itself, as are a given powder charge, bullet, cartridge, primer, etc., due to the variables from lot to lot of ache component involved.

Smokeless powder, has a weak, but relatively high pressure curve upon ignition. Once ignited, it has a fast, spiking pressure curve, much like a spearhead. Again, that is not to say that smokeless powder can't have a bell curve pressure spike. A slower burning powder can have a fast spike and a fast burning powder can have a slow spike, due to variances from lot to lot, and the position of the powder in a cartridge case, the primer being used, the temp and humidity, etc.

What I was referring to in my last post was, the pressure spikes in particular, relative to the propellants used.

I am open to a debate on this, and I appreciate criticisms on my posts and ideas and theories.



Thanks for getting my weekend started.

Buddy

[windrider919]

ExtrahoProeliator, could you give a link to your source? I found my propellant charts in an old copy of Cartridges of the World. But my understanding was that BP had a sharp pressure spike and Smokeless took longer to reach its peak. Pretty much opposite what you wrote. I don''t have the book any more but I hate to think my memory was that faulty. What I remember is that the article described BP as a more rapid burn than smokeless powder. That it classified as an explosive but smokeless did not. And US postal Hazmat shipping regulations follow that too. I guess I will need to search and see if there are any pressure charts on the web.

[Digital Dan]

Sorry, the characteristics of black powder involve it being an explosive (whereas smokeless is a propellant and it burns, but doesn't explode). Due to this it (black powder) generates a shock wave (pressure front) which involves very high momentary pressures and causes much more obturation than smokeless.

As you said "or close enough" - what is necessary that the pressure causing obturation exceeds the plastic strength limits of the lead (= more pressure than the lead can recover from elastically) and that the inertia of the frontal parts of the boolit is high enough that this pressure can act against it, overcoming the elastic limits of the rear and middle portions of the boolit.

Without intent to belabor this, there are certain things to keep in mind in this discussion. The nature of BP pressure curves may present differently than smokeless powder, but the simple fact is that there is no higher pressure manifested through "shock" or "very high momentary pressures" than are recorded on pressure testing equipment. Smokeless generates higher pressures than black and both will obturate bullets IF the pressure/force is high enough. The peak pressure achieved is a function of powder quickness, charge volume, bullet hardness and the total of the bullet's resistance to acceleration (friction+land engagement+mass inertia). Bullets with higher sectional density are more prone to obturate if all else is equal. Larger calibers are less prone to obturation if all else is equal. Bullets with lower BHN are more prone to obturation if all else is equal.

Any of you thinking smokeless powder will not cause obturation are simply misinformed.

http://longrangehunting.com/articles/happens-fire-gun-1.php

If you want to argue with M.L. McPherson, well, pack a lunch.

http://www.barnesbullets.com/resources/newsletters/september-2008-barnes-bullet-n/

Scroll down to the bottom and learn that the Barnes monolithic bullets will not obturate below 45K KPSI. That value is consistent with the formula due to BHN. The will do so at higher pressures however. It is not the powder type that matters.

[leftiye]

You have to remember that the pressure equipment being used, especially the CUP (crusher) method no way can measure really short duration peaks. This is in my opinion the biggest lack in CUP measurements.

Nobody said that smokeless powder cannot cause obturation. But reality is that Black powder has been relied upon to do so as long as conical bullets have been used, and smokeless has been found to be very iffy in this capacity. So much so that standard practice is to size boolits for smokeless cartridges to groove diameter plus so as to not have to depend upon obturation when engraving. Also, generally pressures high enough to cause obturation with smokeless usually cause so much deformation that accuracy goes south. Not to mention providing velocities high enough as to be problematical in view of both deformation and leading.

There are though high pressure loads with smokeless in a chamber/ throat situation where the boolit is well fitted and cannot deform (contained in leade etc.) that work very well, but the goal here is not to cause or utilize obturation in this situation as much as it is to minimize deformation.

[Digital Dan]

You have to remember that the pressure equipment being used, especially the CUP (crusher) method no way can measure really short duration peaks. This is in my opinion the biggest lack in CUP measurements.

Nobody said that smokeless powder cannot cause obturation. But reality is that Black powder has been relied upon to do so as long as conical bullets have been used, and smokeless has been found to be very iffy in this capacity. So much so that standard practice is to size boolits for smokeless cartridges to groove diameter plus so as to not have to depend upon obturation when engraving. Also, generally pressures high enough to cause obturation with smokeless usually cause so much deformation that accuracy goes south. Not to mention providing velocities high enough as to be problematical in view of both deformation and leading.

There are though high pressure loads with smokeless in a chamber/ throat situation where the boolit is well fitted and cannot deform (contained in leade etc.) that work very well, but the goal here is not to cause or utilize obturation in this situation as much as it is to minimize deformation.

All Copper crusher equipment can do it imply peak pressure at a specific point in the barrel, as does lead crusher, commonly used for shotgun loads and BP. A guess on my part, neither is widely used in lab work these days. Peizo electric and pressure trace define the peak and nature of the pressure curve. A peak is a peak, regardless of cause or linear displacement on the curve. I think we agree on that.

I agree that jacketed and GG lead bullets used with smokeless loads are generally sized to groove diameter +/- a gnat hair. It makes obturation somewhat unnecessary on one part and problematic to evaluate on another. That said, Mr. Brooks stated his bullets don't obturate below 45KPSI. I believe it takes quite a bit more than that, but keep in mind the X bullet is SWAGGED. McPherson describes the process in painful detail in context of smokeless powder and if you've read much of his work you know there is quite a bit more to the story than portrayed in the link provided. Fact is that jacketed bullets are for the most part lead core and their hardness in context of this discussion must be viewed as a whole. Merely dropping such a bullet on the floor will deform it to minor degree and this is verified with the Juenke Comparator.
http://www.theaccuracyden.com/

I have been shooting smokeless PP loads for some time. They obturate within the compressibility limits imposed by the paper and do so uniformly. The load is 300 grains of pure lead in a FBFN form of .422" diameter. They are patched with 9# onion skin to .430" diameter. Both dimensions are congruent with the barrel dimensions. The pressures are estimated at about 35KPSI and velocity averages 1605 fps for over 10 shots. ES is 11. The measure of engraved surfaces, or perhaps obturated as a better turn of phrase, is very consistent. .426-.428" "groove diameter" around the full circumference of all recovered bullets, both from flesh and dirt. The impressions of lands and grooves is quite sharp and well defined. If that isn't obturation with smokeless and paper patch, I don't know what is.

[leftiye]

Ever heard of a parallel argument? We're not disagreeing with each other nor are we disproving anything. You can have the last word. Welcome you are.

[ExtrahoProeliator]

Hi Windrider,

I wish that I had my source, but unfortunately it was lost in a move. It was an ancient copy of a Hodgdon reloading handbook. There was a section in it on black powder. Another source that may be of some helpful information, is Lyman's Black Powder Handbook.

To everyone involved in this discussion, with reference and respect to burn rates, black powder burns at pretty much the same constant rate and pressure, either loose or confined in a barrel or cartridge case. This is due to the fact that it is an explosive.

Smokeless powder on the other hand, does not. When it is loose, it pops, cracks and sizzles. When in the confines of a cartridge case, or in a modern muzzle loading firearm, and yes, there are a couple that will let you fire a reduced load in a muzzle loader, it burns with extreme heat and pressure.

Therefore, either propellant will obturate the base of a boolit in the rifling.

Hope y'all have a great night, and enjoy this debate as much as I do.

Buddy

[405]

Good thread.
One post a while back described the "Crusher" method for determining pressure. Actually a small point about that... it is my undertanding of physics that all a "Crusher" set up can do is give an "index" of pressure. And the label of "peak pressure" in the context of the "Crusher" method is somewhat misleading by its very nature. The "Crusher" reveals pressure that is somewhat cumulative in nature as it "measures" a force applied to the crush pellet anywhere between AND all inclusive between powder ignition and bullet muzzle exit.

On the question of blackpowder obturating bullets? I still like my kinetic energy theory. After all, understanding kinetic energy eluded scientists and mathematicians for centuries maybe becasue it is not at all intuitive. :mrgreen:

[Digital Dan]

The best answer I can give you is that paper patched boolits sized to enter the bore will size up IF you use black powder. Smokeless loads usually involve the paper patched boolit being a thou. or two larger than GROOVE diameter and being seated into the start of the rifling (no bumping up).


Leftiye, I'm not looking for the last word on anything, but you can take it that way if you wish. In your first post on this thread you said PP bullets with smokeless don't/won't bump up because they are already at full dimension. They do. Nothing parallel about that. Paper is compressible. I think after review we are of the same mind on most of this, but I had to disagree with your statement because is was misleading. I don't think that was your intention. This form of discussion illustrates the best use of internet chat forums....the ability to share information and learn.

It wasn't long ago that I had no idea what a tricyclic precession mode was.

Nothing left to say on this matter. :drinks:

[montana_charlie]

If that isn't obturation with smokeless and paper patch, I don't know what is.
I don't know what it is, either.

You started with a patched diameter of .430" and shoe-horned it through a .428" hole.
One would expect the .422" 'core' of that package to be sized down to .420" by pressure from the paper.

Paper is compressible
If your bullet is coming out of the muzzle at groove diameter, where did the intervening paper go? Did .008" really compress down to .00gone?

My .452" bullets, patched to .457", travel through a .458" groove, and measure .453" when recovered from a snowbank.
These are 'soft' bullets propelled with black powder.
When recovered they are a thousandth bigger than cast, but the 'package' was started at a thousandth under groove.

Yours start out patched to two thousandths over groove, and (somehow) the bullet itself reaches groove diameter...in spite of being wrapped in paper.

Can it be that yours are 'bumping up' from high speed contact with that 'flesh and dirt'?
CM

[Digital Dan]

I think you misread what I put forth. The rifle's bore is .422" and the groove is .430".

In other words, the bullet is patched to groove diameter. The bullet is swagged at .422" diameter. Recovered diameter is .426"-.428" on the shank adjacent to the bullet base. It would appear the paper compresses to around .002"-.004" according to my math. I'd think maybe the impact might have some influence on that except that the measurements are very consistent around the circumference of the bullet. Are you shooting BP or smokeless?

[leftiye]

I think you are right, the problem is I'm not sure what it matters. The loads with paper and smokeless were made WITH NO INTENTION OF UTILIZING THE OBTURATION OF THE BOOLIT.

[docone31]

I doubt mine bump up at all.
I have a very hard blend with some zinc in the stew. I water drop these. Sizing them is indeed a challenge.
I doubt upon ignition, they bump up in the bore. Scratching them with a fingernail is a no go.
Others have tried my technique for patching. I am more and more suspecting it is the hardness that contributes to the success I have had with them.

[leftiye]

Doc, An intrigueing idea! So long as the bullet were to act like a bore rider (or approximate such) and so long as the paper were to seal the gasses, and grip both the rifling and the boolit, that should fly (straight). IIRC, you size your boolits themselves at .308 or thereabouts for both your .30 calibers, and your .303 British, which is some bigger than bore rider. Your second sizing after the boolits are wrapped would seem to resize both the boolit and the paper.

[docone31]

I size my .303 to .308 also. I have two different molds also. One for .30, one for .303. both Lee.
I wrap them identically. Both two wraps of printer paper. My strips are 1", and the length is 1 3/16. I have a small overlap on each caliber.
The nose on the .30 is .301, and the .303 is .304.
What I have been doing lately, is dropping the hardness slowly. Since we are now at a crossroad and BP seems to be unaffected, I am switching to smokers. Now I am ingoting pure and mixing it with my WW mix.
So far, I have not noticed any loss in performance. I have not really cast softies yet.
I am thinking I am also extrudeing paper into the lube grooves on sizing, rather than displaceing lead on sizing.
It is still a mystery to me. I just know I found something that works.
That alone is a miracle with my brain.

[Yellowhouse]

Smokeless rockets a bullet out of the barrel.

BP "knocks" it out of the barrel.

A gentleman across the water with vast experience says that it is not unusual to get .012 obturation out of BP guns.

Has to work cause .446 bullets out of my roller bump up and fill .451 grooves. Ain't trying smokeless in that old war horse though.

[303Guy]

Probly (possibly) the difference is where the boolit is when the pressure happens - say contained partway down the barrel and after the gas seal has been accomplished (reads cannot expand) versus in the case/throat leade or in the bore, and unsupported?
Any shock that will obturate a bullet more will stress the steel more. The higher the pressure the greater the stress on the bullet regardless of how fast that pressure rises. By the way, if black powder explodes and burns up early in the bore, why does it produce such a loud report? Also, don't black powder guns use soft lead? My understanding is that black powder burns real slow which is why it has to be ground real fine to get any kind of performance out of a pistol.

[rayg]

By the way, if black powder explodes and burns up early in the bore, why does it produce such a loud report? Also, don't black powder guns use soft lead? My understanding is that black powder burns real slow which is why it has to be ground real fine to get any kind of performance out of a pistol.


Here's a thought. If you put in too much BP in a muzzle loader. Not all the powder will burn up before the bullet exits the end of the barrel. You will see the excess powder burning and fizzing out the front of the gun. In other words it appears you can never overload a BP muzzle loader providing the bullet is free to move down the bore. This would seem to indicate that BP is a slow burner, no? Ray

[leftiye]

Black powder has a two phase burning cycle. It detonates - reads = it ALL ignites instantly (it IS an explosive). Goes ping you would say - if it were a gasoline engine. Therefore creating a shock wave as do all explosives. After the initial detonation, the particles continue to burn - Therefore the long barrels preferred in days of yore.

Montana Charlie had a very insightful (as he often does) take on the bumping up - that it may be true that not only the pressure wave, but the powder charge (due to the detonation) itself hits the boolit in the butt (so to speak), thus causing disproportionate obturation.

[Digital Dan]

http://en.wikipedia.org/wiki/Gunpowder

See paragraph #2.

[303Guy]

From Wikipedia;
A more accurate, but still simplified, equation is[6]

10 KNO3 + 3 S + 8 C → 2 K2CO3 + 3 K2SO4 + 6 CO2 + 5 N2.
The burning of gunpowder does not take place as a single reaction, however, and the byproducts are not easily predicted. One study's results showed that it produced (in order of descending quantities): 55.91% solid products: potassium carbonate, potassium sulfate, potassium sulfide, sulfur, potassium nitrate, potassium thiocyanate, carbon, ammonium carbonate. 42.98% gaseous products: carbon dioxide, nitrogen, carbon monoxide, hydrogen sulfide, hydrogen, methane, 1.11% water. I still think obturation of black powder bullets is a function of the soft lead used in them.

Black powder does not detonate - it ignites and burns rapidly. It is a 'low explosive'. High explosives detonate. That means they transform chemically at the speed of the shock wave that progresses through them. There is no supersonic shock wave either. Not possible. Sonic speed is the speed the of the shock wave - which is very fast! Very, very fast!

[Zeek]

Same thing with any kind of projectile. ... felix
Of COURSE it is a projectile! NOBODY wants an amateur jectile.
Zeek

[Zeek]

Just curious, but do patched bullets bump up into the rifling like jacketed bullets do because they are fired at higher velocities like jacketed bullets? We all know that jacketed bullets when fired at the higher velocities, even though they are under the groove size, will bump into the rifling where cast bullets at lower velocities do not. Ray
Mic McPherson answered that issue a while back. He switched cylinders in a 45 LC Ruger sixgun, replacing it with a 44 Magnum cylinder. When he fired a jacketed-bullet round, it expanded to 45 caliber, grabbed the rifling, and, in fact, didn't shoot all that badly, considering. Now, you do NOT try that with copper solids, of course, but a soft-lead J-word WILL expand, within reason (and quite a bit beyond that) to fit the groove diameter and then spin-up.

Actually, this is the same approach used in the PPatched buffalo BP rounds that had an across-the-patch diameter no more than 0.002 over bore diameter. They were seated out as far into the bore as feasible and expanded, upon firing as much as the gunk (filling the grooves near the rear of the barrel) would allow, and then CONTINUED TO EXPAND, later on, to fill the clean grooves a few inches down the line. Translation: we HAVE seen this before, so should not question it. It happens and it works just like that.
Regards, Zeek