Hi folks,
A recent question, which stroke my eyes. I read an article in which the author stated that in most cases gasses from the combustion of the powder could escape alongside the bullet and get in front of it during the barrel passage. So these gasses were passing the bullet and could have more velocity than the bullet itself.
Is this true or is it nonsense?
In well made barrels and with well made bullets this seems impossible to me, but what is your opinion? Hot Core perhaps?
Nice day and thanks for input,
Jan

Since things happen very fast and since there is a short period where the mouth of the case has opened under pressure while the bullet hasn't yet contacted the lands, the lighter gas could, in my opinion get by the bullet for a short time before the bullet occludes the bore.

If the bullet were undersized for the bore a certain amount of the gasses would pass along side in the lands of the bullet, and probably have a slightly higher velocity , but as long as accuracy is acceptable SO WHAT

Jan, don't believe everything you read. Modern "journalists" make money selling stuff not understanding how it works. There maybe an brief instant where some gas gets past the bullet as it enters the throat and obturates (fancy word for distoring into the rifling). Especially a problem with short light bullets in guns made for long heavy bullets, like a match AR with a throuat for 80 grain bullets and shooting a 52 grain in it. In the high speed pictures of a gun firing the "puff of smoke" seen is the air in front of the bullet being forced out by the 800 to 3300 fps projectile behind it.

If the combustion gasses passed the bullet you would not build pressure. In cast bullets (2 "l's" no "o's") gas checks were invented to keep the gasses from cutting between the bullet and the rifling. In modern fire arms the soft copper and lead construction allow th ebullet to seal the bore.

Another way to look at this is as an engine. When your rings go the engine still runs but has no power and leads to cylinder damage.

Hey fellas, don't speak to loud about gas passing bullets. Al Gore and to other idiots will start claiming more global warming green house gases.
The UN would start hearings leading to banning under the chemical warfare treaties.
I sort of like the idea of bullets passing gas or was it gas passing bullets
Jim

Well said, Sam. Some years ago and experimenting with moly coated match bullets I was told that you needed to load a bit heavier to keep the same velocity as non coated due to "slippage" of gas around the bullet seal? Supposedly the moly due to higher lubricity/less friction, would permit this to happen? One hears all manner of "facts" but I ceased to use the molys so it did not matter to me.

quote:

the author stated that in most cases gasses from the combustion of the powder could escape alongside the bullet and get in front of it during the barrel passage.

I think this is pure bullshit!

Was that the correct thing to say???????????????

quote:

Originally posted by Jan:
...the author stated that in most cases gasses from the combustion of the powder could escape alongside the bullet and get in front of it during the barrel passage.

Hey Jan, It is colloquially refered to as "Blow By". Articles are written and become "dated" as they set around awaiting publication. And older Books/Magazines contain a lot of information relevant to a specific time period, which may be slightly different when read at a later date.

If you want to create Blow By, you can get a Very Hard Cast Lead Bullet that is slightly "Undersize" for the Grooves and it will happen - no Obturation. Or you can have a properly Sized Hard Cast Bullet, shoot it through a Revolver Chamber which is smaller than the Groove Diameter and you will get Blow By.

I seem to remember this Chamber situation used to be an issue on some of the old Colt Revolvers. GunSmiths would Ream the Chambers in the Cylinder slightly Larger than Groove Diameter to get them to shoot accurately.

It can be seen on recovered Bullets as small Grooves and Rounded Edges where they should be Sharp along the Wider Diameter of the Bullet which was inside the Barrel Grooves.

This also creates a different type of Leading which can go full length of the Barrel. And as a couple side Benefits(???) it leads to short Barrel Life due to the Torch like Flame Cutting of the extremely Hot Gasses and poor accuracy with the Flame Cut Bullets.

It is possible to Cast a Bullet too Hard which creates unwanted results.

quote:

So these gasses were passing the bullet and could have more velocity than the bullet itself. Is this true or is it nonsense?

True, depending on the above listed situations.

Also agree with Grumulkin about the Blow By during the Transition from the Chamber to the Barrel - in a Revolver. In a Pistol or a Rifle, then having the Bullet Cast/Swaged 0.001"-0.002" over Groove Diameter, plus Seating close to the Lands "almost totally" stops Blow By, but there is always just a little in the very beginning of the Firing Sequence.

quote:

In well made barrels and with well made bullets this seems impossible to me, but what is your opinion? ...

That is close enough to reality to not make it worth arguing over. Just depends on the Chamber/Barrel dimensional relationship and how "Hard" the Bullets are Cast.

Gas can get past a jacketed bullet if there are tight spots in the barrel. The gas has to be going faster then the bullet to pass. How common is it , i do not know. Air gauged barrels prove there are tight spots. If there is a wide variation in groove diameter, bad things happen to the bullets.Most of these bad barrels will never leave the factory, surely never a custom barrel maker. Barrels with variations in groove diameter,if not to large, do not effect accuracy if the muzzle is the tight area. Bench rest 22lr shooters will gauge a barrel, then cut it off in the tight area of the barrel groove, and recrown it.

If you've got a good smith, he will measure each end of your tube and put the smallest end as the muzzle.

Yes...gas DOES pass the bullet from the moment the bullet exits the case until the jacket "obdurates" and seals the bore.

There is quite a bit of room around the bullet OD and the ID of the chamber neck/throat and the gas merrily "blows by" or however you wish to describe it...

Newtons 1st law of inertia covers this phenomenone---Objects tend to remain stationary or tend to continue in motion unless acted upon by an outside force---the mass of the gas is lighter and under continuously increasing pressure due to the powder burning and will accelerate quicker than the mass of the bullet, the mass of the bullet takes time to get moving and which is also covered by Newtons 2nd law F=MA, Force equals mass times acceleration or in this case, more aptly applied, A=F/M, Acceleration equals Force divided by Mass...

There is also a variable amount of distance between the bullet OD and a variable amount of time for the bullet to get stuffed into the lands and obdurates, which also allows for the gas to flow/blow by.

Whether or not it has any meaning other than academic "gass" is up to you...it happens, it has an effect, it is part of the concept of
"gas cutting" on the throat metal, but for all intents and purposes it doesn't mean squat to the average hunting rifle and only slightly more to a competition shooter as gas blowby does affect accuracy over time...unless you're talking about a 7mm bullet going down a 30 cal barrel or something equal.

It would take a camera viewing the INSIDE the barrel looking at the WHOLE area from the chamber to the barrle end and taking vids in microseconds to actually "see" what the heck is going on and a pretty fast computer to calculate what all the components are doing.

As per usual there is a ton of mis-information, dis-information, smoke and mirrors and down right lies concerning this phenomenon.

I will volunteer for the experiment if everyone ever using this site will send me $1000.00 apiece to front the equipment.

Luck

If this is a problem effecting accuracy or other exterior ballistic factors (EBF), just get someone to dissipate the exiting gases by waving their hand RAPIDLY (important) in front of the muzzle just before the bullet exits.

Blonde headed women seem to be best for this.

You could circumvent any questionable effects by just stuffing the bullet into the lands to begin with so the bore would be sealed BEFORE the gas could start causing any questionable problems.

Then the only thing to be considered is the air in the bore in front of the bullet.


I wonder just what effect that will have on accuracy?

Be sure to include an extra $100.00 apiece for the extra work in that determination.

Luck

Sounds like something I would say, if fir no other reason than to get someone to think, after the bell has been rung there is no way to put the sound back, it has already been decided: gas passsing is not a rare event.

According to D. R. Corbin of Corbin Manufacture gas passing is a good thing, Gas passing the bullet reduces resistance caused by atmosphere compression ahead of the bullet. Only if it was possible to film/record the bullet leaving the barrel or if it has been done those watching should watch more closely, if gas does not pass the bullet there will be a small white cloud or puff leaving the barrel first because as we all should know when an atmosphere is compressed the moisture becomes vi sable, then there is heat, the atmosphere in the barrel will be thinner because of heat is ambient (hidden) but hot air is thinner and less dense than cold air AND heat determines the amount of moisture air can be suspended so when the atmosphere is hot it is thinner thin and less dense than cold air, but when it comes to flying cold air is more stable,

Yes it sound like gas passing... the bullet sounds like something I would say because time is a factor, we all go to gun shows and gun stores etc., and pick up a rifle, throw it to our shoulder and point it at something,well almost all of us, I do not, I open the bolt and check the condition of the barrel, smooth, dark, rough, pitted, I checked a Springfield type Rock Island 03 double heat rifle in Victoria TX. in appearance the rifle had nothing but a black hole down the barrel, it had never been cleaned NEVER! so I told the dealer I would purchase the rifle if he could convince me it had rifling's, in an hour he had worked up a sweat and found the hint of rifling, I purchased the rifle cheap then spent a week of cleaning, I was told it was a loss cause. When finished the barrel was like new 'inside' over the years the bore had built up a cake similar to a cured tobacco pipe, my concern then was for the receiver, the hole down through the barrel was less than .300, the bullets were .308 my thinking the bolt and receiver took a hammering every time it was fired and I would suspect after the bullet was swagged into the bore, there was no gas passing,

And the rifle came with a straight handle bolt.

In the beginning there were black powder rifles, then there came the conical bullet and bullets with a concave base, it is only a wild ... guess but to me it seams 5% of the blast beats the bullet out the barrel, but as Corbin and the other experts before the Internet would say 'including Martha Stewart' "That is a good thing".

F. Guffey

Just what we need a thread on gas passing.

SOME, a tiny bit, passes the bullet before it exits the barrel.. then the gases appear to be rushing past the bullet.. but, in fact, acceleration has ended at that point

Try this link:Image Source Page: http://www.thegunzone.com/45hst.html


Indeed, it appears that the gasses have exited the muzzle ahead of the bullet.

K-22hornet, that is all I was trying for APPEARS. Thanks for the effort,

F. Guffey

Thank you very much, guys, for the serious answers.
So blow by could happen in special circumstances, but can't be considered as an always happening phenomenon.
Thanks a lot,
J.

quote:

Originally posted by vapodog:

I think this is pure bullshit!

Take a look at the video on this page for an example of gases leaving the muzzle before the bullet:
http://www.kurzzeit.com/

Looks like some dirty powder.

They have a youtube video that is about 10 minutes long of bullets hitting plates, targets, glass. I was glued to the screen the whole time.

quote:

the author stated that in most cases gasses from the combustion of the powder could escape alongside the bullet and get in front of it during the barrel passage.

BS, at least in the sense the author presented it.

All the video shows is the exit of residual smoke/air in the bore from a previous shot being forced out ahead of the bullet.

quote:

All the video shows is the exit of residual smoke/air in the bore from a previous shot being forced out ahead of the bullet.

That looks too much like a jet of gass traveling faster than the bullit. right at the muzzle and the puff is way ahead of the bullit and remains there. Wathcing a differend video one can clearly see the gas exiting the muzzle ahead of the boolit - not being pushed out bt the passage of the bullit.

It would be unreasonable to expect a jacketed bullet to seal the bore perpectly and the pressure behind the bullet is rather high. There must be a powerful annular jet of gas escaping past the bullet especially if the bullet is under groove size. Examining fired bullets one does not usually find groove contact marks. A properly fitted grease groove cast bullet or a paper patched bullet might seal perfectly. The cast bullet operates at much lower pressure while the [paper patched bullet operates at near full rifle pressure. It has to seal or it won't shoot straight.

quote:

D. R. Corbin of Corbin Manufacture

http://docs.google.com/viewer?...0VadpplmPOuDUGdY9WEg

andCorbin said gas passing the bullet is a good thing.
F. Guffey

Long before the Internet and us, a picture taken from behind a large shore gun at the moment the large projectile left the muzzle, it took longer to sort out the details of what the photo captured than it took to build the big gun. In the old days they thought it was just a blast without details, and time was/is a factor.

F. Guffey

I think that gas passes the bullet during the jump to the lands for sure. after that it may or may not but I think that the idea is that it doesn't. There are no "perfect" barrels with exactly the same diameter from end to end and when it goes from slightly small to slightly big (think .0001 difference) some gas will go around. In that same line of thinking, longer bullets would leak less because they might even bridge some of these inconsistancies. Shorter bullets would leak more. I think the amount of these inconsistancies and the amount of gas leakage is what can separate a bad barrel from a good barrel and a good barrel from a great barrel. If you want the most accurate barrel, it should limit the gas leakage and thus the release of the bullet out of the muzzle will be the most consistant.

FWIW, I think the video shows the column of gas already in the barrel being pushed out by the bullet more than it shows blow by. I might have seen one little puff of blow by and that is it.

quote:

Hi folks,
A recent question, which stroke my eyes. I read an article in which the author stated that in most cases gasses from the combustion of the powder could escape alongside the bullet and get in front of it during the barrel passage. So these gasses were passing the bullet and could have more velocity than the bullet itself.
Is this true or is it nonsense?

It's true that a SMALL percentage of burned gases do in fact jump ahead of the projectile .As powder ignition is far quicker than projectile jump an sealing ! . However the small amount of Passing Gas is in NO WAY ,to be construed as more velocity . The bullet under velocity is PUSHING the gases ahead of that bullet , an that's why in super slow frame one sees the bullet punching through expended gases ; rather than those gases blowing ahead of projectile . In that video note the sealed gases blowing outward and forward once the projectile exits the bore. That's the Gas of " velocity "exceeding the projectile

If one wants to prove this it's relatively simple to do . I suggest a Pistol cartridge rather than Rifle ( for ease of bullet removal ) Build a " SAFE " severely under powered load . Gases will pass and float out the end of the bore ,while bullet remains lodged in the bore . It sure as hell isn't going to explode out the end of the bore ,it merrily floats out ,as it's energy is expended within the frame work of said bore length . AN if ANY of YOU try building that load ; BE SURE AS HELL TO REMEMBER TO CLEAR THE BORE !!!!!!!!!!!!!!!!!!!!!!!!.

I've not only seen this on Cowboy pistol shoots but also on the Trap Skeet Clays courses from squib shot shell loads .

I have a friend who RUINED his Winchester Model 101 with a NON intentional squib load !. Wad failed to clear one of the bores ,yet smoke came trickling out , I was next too him on the Trap range and thought to myself it sounded like a punk load . I Yelled at him to check his bore , having his hearing protection on he failed to do so . Unknown too myself as I was on station next . When his round came again he Bulged the top barrel !!!!!!!!!!!.

Some leakage around the bullet is a certainty and photography shows that it is a good bit of gas. My high speed internet is at the moment stuck on dial up speed or I would try to find some examples.

Chronograph placed 12 to 15 feet in front of the muzzle so it won't get confused reading from propellant gases? I say that true.

I saw the words Gass and pass and it immediately made me think about my good ole hunting buddy, Hotsh$t.

Sorry, my mistake.