5mm smc

FiftyDriver brings up a good point about accuracy and bullet stabilization. Seeing that stabilization is really based on RPM's rather than a rate of twist, once you start getting speeds that this round claims, you can start playing with slower twist rates and will still be able to stabilize heavier bullets.

Seeing that Pac-Nor now chambers this round, and dies and brass can be bought from Russ Haydons supply, and go no-go gauges can be had from pacific tool and die, I am planning on building one myself just to see how it handles. And even though most people would agree that 1-10 twist is needed to stabilize the 50gr Bergers, I'm going to get a 1-12 instead and would bet it will still work fine.
 
Does anyone buy the claim of less recoil and barrel heating? Could less recoil be achived by keeping more powder in the cartridge case and not sendng it down the barrel with the bullet? Is this why the short mag crowd clame less recoil? Kind of off this threads topic but I've always been curious.
 
[ QUOTE ]
Does anyone buy the claim of less recoil and barrel heating? Could less recoil be achived by keeping more powder in the cartridge case and not sendng it down the barrel with the bullet? Is this why the short mag crowd clame less recoil? Kind of off this threads topic but I've always been curious.

[/ QUOTE ]

No.

Recoil is a simple function of the law of action and re-action.

The momentum (weight x velocity) of the bullet, plus the weight times the "average" velocity of the gas after the bullet has left the muzzle (called the "jet effect") MUST be equal to the the momentum of the rifle (weight x velocity) in the opposite direction.

Since the weight of equal rifles is the same, and the weight of the powder is the same, if the velocity is the same, the recoil must be the same...
... the only way it could be less is if the gas velocity after bullet exit was less, and this could be less only if the pressure was less, but that can't happen, becasue the velocity of the bullet is determined by the average pressure, x the barrel length, less the friction.

Which means that if the same amount of powder is used with the same weight of bullet in identical guns (of identical weight and barrel length)... the recoil MUST be the same if the velocity is the same.

In in simple numbers, if the sum of bullet (and powder gas) weighs 1 pound and the sum of the velocities is 1000 feet per second... the the gun weigh 1000 pounds, it will recoil at 1 foot per second.

No one has EVER broken this law. When they do, they immediately get a Nobel prise in physics, and spend the rest of their lives earning billions on the lecture routes.

AS far as heating the barrel... the same thing applies - the heating of the barrel is due to the calorie transfer coefficient of the steel, times the average temperature of the gas, times the time in the barrel... plus the mechanical heating of the barrel caused by the physical motion of the bullet. For equal barrels, and equal velocities, these are equal.

These "theories" are the purest of BS.

In con games, it's called "Smoking the Rubes" (aka "Blind them with ********!")

It is a common tactic. Throw enough bad science at a non-scientific public, and they automatically believe it, because, well... "It sounds so scientific"

.
 
Thanks Cat, I find it hard to believe that one shoulder design can "hold" a powder change and control the burn better than another. At least to a noticeable effect. I don't have a 204 Ruger yet and I do think tis 5 smc is cute. Hmmm...................
 
Cat, It cracks me up the way you explain things./ubbthreads/images/graemlins/grin.gif Only you can put together complex mathematical calculation, explaining the laws of physics and Thermodynamics principles all in one, in a way that is plain and simple enough for people to understand; not to mention that it's humorous at that. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif
 
Cat is 100% right.

On a side note, the average gas velocity is not "standardized" so some calculations will show a disagreement between their outputs when doing Recoil calculations. No matter if we're talking on Recoil Impulse or else.
 
catshooter,

Can you tell me why the short fat cases use less powder for the same velocity with the same bullet weight as the longer skinner cases?

I have several short fat rounds and their "equal" longer rounds and the short fat ones do seem to be more efficent, using less powder for same outcome. So if you have less powder to multiply by than you will have less recoil.

Engineering on paper does not always work the same as real life experiences. Can't control or figure on all variables that will influence the outcome. Not saying you don't know what you are talking about just that things on paper don't always work the same way in real life!
 
I would have to agree on the comments already mentioned about barrel heat and life.

Only way to keep the barrel significantly cooler is to A. reduce your powder charge or B. keep the powder in the case while it is burning.

No matter what you do, with a rear ignition case design, the powder will be pushed into the throat while it is burning to some degree or another. The larger the powder charge, the more will burn in the throat/bore.

Forward ignition is the only way to stop this. THis system uses a long flash tube to carry the primer flame up to a location right under the base of the bullet. The powder near the bullet ignites first and then the rest of the powder burns from the case shoulder back to the rear of the case.

Basically speaking, no powder leaves the case in solid form while its burning, only gas from the burnt powder in the case.

I have tested this with many rounds and can say without a doubt it dramatically reduces bore temps. Only problem, in small caliber cartridges, it is pretty much impractical to use this ignition system simply because the small dimensions are to hard to work with installing the flash tubes.

As far as why a short fat case will generate more velocity then a long skinny one of equal length:

1. shorter case design has more usible barrel length from where the bullet is seated to the muzzle.

2. A shorter, fatter powder charge has a larger cross section in the powder charge column. As such, more powder is exposed to the primer ignition to start with and more powder volume is ignited as the powder burns so the powder simply burns larger amounts at a quicker rate then with a long skinny design.

My opinion for sure but that is why I think it happens.

To be honest, if you give the two rounds the exact same usible barrel length, the different will be smaller just with that.

Kirby Allen(50)
 
I read a story on this cartridge in Rifle Shooter Magazine (March/April 2006). It was interesting but as usuall had many contraditory statements. It claimed a velocity of 4700fps but if you looked at the chrony print out, a five shot string produced a high of 4692 and low of 4648 Then it compares the ballistics of the 32 grain Sierra BK to the BC of a 22 cal 40 Gr Ballistic tip. Refering to 4700fps with the 5 smc to 4400 fps out of a 22-250. Well the Chrony tape lists a Berger 30 gr bullet not the 32 gr Sierra they use in their comparison. Why? So typical misleading statements which generally tell me one thing....BS Later in the article though it does give a good explanation of why a shorter fatter case has less recoil. This is due to a smaller lighter propellant plug being acclerated into the bore. Makes sense to me knowing that most recoil is directly related to the weight of the bullet. Basically what they are saying is that due to the better surface area ignition of the short fat case the gas in the brass pushes against a lighter plug thus generating less recoil than on a long case of the same capacity. I can believe that.....Anyway I think its a neat design but untill brass is as cheap and available as say a 22-250 it will never be as popular as the others.

Lance
 
What is not understood by most all shooters is that ALL of the powder is ignited at once. There is NO plug of powder that is pushed down the barrel.

The powder does NOT burn from back to front, (or front to back)... and that shock waves (aka sound waves) cannot ignite powder, no matter how loud, or what frequency they are created.

So all the rest is BS.

Also... "Makes sense to me knowing that most recoil is directly related to the weight of the bullet".

"... knowing that most recoil is directly related to the weight of the bullet" - how do you know that? From where?? What math and physics do you call on to make that statement??

Explain the science and physics behind that "knowledge". You CAN'T!! That's cuz it's pure ********.

It is this kind of statement that passes on myths from one group of shooters to the next... each "new" group believing it because they read it "somewhere", and it sounded so, well, you know... ah... er... scientific! Yeah, that's it, SCIENTIFIC /ubbthreads/images/graemlins/smile.gif

Recoil is related to any, and ALL, "ejecta" from the barrel. Physics does NOT differentiate whether it is copper, lead, or gas - if it has weight, and is pushed out the barrel, it causes recoil in the linear formula of "weight times velocity" (NOT squared!!).

Now, if you have a bullet that weighs 35 grains, and you have powder (which turns to gas) that weighs 35 grains... that is 70 grains of "stuff" that is being thrown out of the front of the barrel, so the recoil is equal to the opposite momentum.

Now, what is not understood is that at the moment the bullet clears the barrel, that momentum (35 grains times the velocity) is only part of the equation... now you still have 35 grains of gas in a column, of which the front is traveling at the muzzle velocity, and the rear (at the case web) is traveling at ~"0" fps, so the average velocity of the gas column, so far, is equal to 1/2 the muzzle velocity.

The added momentum (so far) is equal to the weight of the gas, times 1/2 of the muzzle velocity... OK??... but the whole column is under pressure - from ~10,000 to ~25,000+ psi.

When the bullet leaves the barrel, this uncorks the gas, and that column of gas REALLY takes off, reaching 4,000 to 5,500 fps, and that gas gives an additional component of recoil - this is called the "Jet effect", and has been known of for a long time - it is not theory, it is fact, and can be measured separately.

So how can you make the statement... "Makes sense to me knowing that most recoil is directly related to the weight of the bullet"... when, in fact, it makes no Goddamn sense at all! It is pure gibberish!

The effect of the gas is NOT inconsequential - in the case of a 35gr bullet, and 35grs of gas, measure the momentum of the bullet (35 x 4,000fps), and the 35 grains of gas (35 x 4,000 to 5,500 fps) and you will see that the gas can add as much, or MORE to the sum of the momentum, than the bullet.


It is this gas, and the ability to direct it, that causes muzzle breaks to be effective. If the propellant were compressed Helium, and weighed 5 grains, it would have a small addition to recoil... (and hardly any effect in a muzzle break).

[ QUOTE ]
Basically what they are saying is that due to the better surface area ignition of the short fat case the gas in the brass pushes against a lighter plug thus generating less recoil than on a long case of the same capacity.

[/ QUOTE ]

There is NO "better surface area of ignition"... all the grains are lit at once - the volume of the primer flame rushes through the grains and ignites them all in about nothing flat - and because of the way that smokeless powder burns (it is similar to sublimation, with the flame just above, and not touching the grain), the grains do not come in contact with each other... the burning powder behaves more like a "slurry" of burning sludge. This is also not an "opinion", it has been proven.

So this flaming "sludge" flows into the barrel, pushing the bullet, no matter what shape the shoulder is.

Not to "flame" anyone (that's a pun, son), but 95% of what the shooting public "thinks" goes on inside a case and barrel, and outside too, is an accumulation of pure wives tales, started by people guessing what goes on, "cuz it makes sense to ME!", written by gun writers (who never finished high school science and physics), and passed on by gun magazines (which are NEVER checked for accuracy), and now propagated by internet websites.

I just have no patience with this Bull poopie!

I know... I'm not on anyone's Christmas card list this year /ubbthreads/images/graemlins/frown.gif

That's OK, I send them to myself /ubbthreads/images/graemlins/wink.gif.

.
 
[ QUOTE ]
CatShooter,
Can you tell me why the short fat cases use less powder for the same velocity with the same bullet weight as the longer skinner cases?

[/ QUOTE ]

They don't!!

[ QUOTE ]
I have several short fat rounds and their[sic] "equal" longer rounds and the short fat ones do seem to be more efficent, using less powder for same outcome. So if you have less powder to multiply by than you will have less recoil.

[/ QUOTE ]

What the hell does "...seem to be more efficent[sic]" mean? By what standard?

Your statement only applies if you have set up the comparison so all factors are equal, except the chambers, and you haven't!

[ QUOTE ]
Engineering on paper does not always work the same as real life experiences.

[/ QUOTE ]

Yes it does - if it doesn't, your "real life experiences" haven't been "experenced" the same way as your engineered on paper was done, so it doesn't match your your work on paper.

You cannot "engineer" something on paper, then "run an experiment" with different criteria, and then bitch that "real life experiences" don't match your paper work, when the experiences are NOT what you did on paper.

[ QUOTE ]
Can't control or figure on all variables that will influence the outcome.

[/ QUOTE ]

Listen... don't talk this "engineering" crap, and then say you "Can't control or figure on all the variables".

If you can't control the variables, you aren't engineering ANYTHING - you are just blowing smoke and making noise.

Engineering IS controlling the variables.

[ QUOTE ]
Not saying you don't know what you are talking about...

[/ QUOTE ]

Yes you are - you just don't have the stones to come right out and say it!

[ QUOTE ]
"... just that things on paper don't always work the same way in real life!"

[/ QUOTE ]

That's because you aren't an engineer... if you were, you wouldn't make that statement.

A true story.

Some years ago, I got together a bunch of 308 rifles, and 100 rounds of 308 match ammo, same lot number, from the same case.

There were 4 rifles... none were junkers.

One had a 28" barrel.

Two had 26" barrels.

One had a 24" barrel.

The average velocities (20 rounds) were 2725 fps, 2685 fps, 2575, and 2550 fps.

Now I can, from the above facts, make the following statements.

"Well, long barrel lengths are faster than shorter barrel lengths"

Not true... we might assume that the 28" barrel went 2725 fps, and then we can assume that 24" barrel gave the 2550, but how does that explain one 26" giving 2575 and one giving 2685?? You CAN'T!!

OK... let's try the ol' "barrel friction" theory. It goes:
"Well, bullets only accelerate for the first 18" then slow down from friction"... we've ALL heard that line of BS (which applies to 0.002% of barrels with tiny cartridges).

So lets do the barrel friction thingie.

24" = 2725 fps
28" = 2550.
But Uh oh, we are back to 26" = 2575, and 26" = 2685?? It still doesn't play.

OK... lets try the "secondary explosion" theory... powder "burns, then goes out, then has a secondary "detonation".

So, 28" is back up to 2725 fps, and 24" is down to 2550 fps, and maybe one of the 26" was 2575, but the other 26" had a "Secondary detonation" and so the velocity went up to 2785 fps???

Well, that means that sometimes, you get a "secondary detonation" and some times you don't... in the same barrel length???

It doesn't fly

Well now, MR engineer, match the velocities to the barrel lengths, and explain why?

You can't! And that's because barrel length is not the only factor.

The real numbers were:

#1 - 28" was 2725 fps
#2 - 26" was 2550 fps
#3 - 26" was 2575 fps
#4 - 24" was 2685 fps.

Now explain why???

You can't!!

The differences were that the chambers were cut to different reamer specs.

#1 and #4 were match reamers with tight throats, and #2 and #3 were "field" reamers with long throats.

If you take two of the same barrels (two Shilen select match), and then cut two chambers that are throated alike, but one with a short, fat case, and one with a long, skinny chamber, BOTH of the same case volume, and then cut the barrels so they measure the same FROM THE THROAT, you will get the same velocities, within the same variations as you will get from two of the same chambers.

So take your case and try to sell it somewhere else, cuz it doesn't float.

Go out and spend the money and do it. Cuz up to now, you haven't presented ANYTHING that remotely resembles "engineering on paper"... you have presented toilet paper theories, with nothing but "it seems...".

.
 
CatShooter,

It must be extremely frustrating for you to know it all and having to hear a bunch of dummies giving their opinions. I'm surely glad that God doesn't take your attitude towards us because if he did we'd be toast. /ubbthreads/images/graemlins/frown.gif
 
Guy's it is relatively simple,with all things equal no matter HOW a case is shaped (short and fat or long and skinny,shoulder shape,etc.) at equal pressure the one with the most powder capacity will be the fastest... More case capacity means more volume of gas to continue projactile accereration at a faster rate than the one with less case capacity.A greater volume of gas means that (in equal barrels with the same chambers) the gas pressure will be higher at the muzzle than it will be from the case with less case capacity.

Catshooter is SPOT ON like it or not............
thumb.gif
 
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