Bigger diameter - is it always safe? (At least for 9mm)

[recoilguy]

Waaa Laaaa
nicely stated sir!!!

RCG

[Dan_69GTX]

Ok,  I'm slow - I just noticed this.....

"What I lack in speed, I make up for with inaccuracy"

I need that on a shirt!

[deadsh0t]

I'm not talking about the barrel but the gun in general due to pressure / vibrations, etc...

Except from erosion, I thought the fact that they burn faster with higher pressures, they tear the gun sooner (in general, not every double based powder)

You need to separate Temperature, Pressure, and Velocity in your thinking.


> The addition of nitroglycerin to any "burn rate" powder (whether "fast" or "slow") makes it burn at a much higher temperature. It's that elevated temperature, right in front of the shell casing, where the combustion is the hottest. that erodes the steel of the barrel. Of course, we're talking about over the course of 30 to 50,000 firings. This is normally a very slow process, but nitroglycerin definitely accelerates the wear.

Yes, the Pressure is also highest at that same location, but that is a function of the burning powder. There is also Pressure in the chamber of Olympic air rifles, but very low Temperature. And so after 50,000 pellets, these guns show no throat erosion. They may show wear over the entire barrel due to sliding friction from the pellet, but it is not localized at the throat.


> If a given bullet's Velocity is the same with 2 powders, one a double-base and the other a single-base, then the Pressure is the same for both powders. There is a 1:1 relationship between Pressure and Velocity. That's the whole idea behind the chronograph.

Normal Pressure within the barrel will not hurt the barrel. Obviously there are ways that are not Normal where Pressure can hurt the barrel, like double loads and debris blocking the barrel. But again, these are not Normal occurrences, and no shooter plans on having these.

Ok for the general idea. About the pressure / velocity, I'm not sure about it. Different powders can have the same velocity but different pressure peaks. That's why some powders are preferred for military ammo rather than others.

So given that, cronograph Will just test speed near the muzzle. Nobody talked about gun breaking sooner, but I can guess that some shoot less than 5000 rounds a year so unless it's specified it's hard to tell

[deadsh0t]

Waaa Laaaa
nicely stated sir!!!

RCG

Why even post just to troll?

[recoilguy]

does it upset you when I post?

RCG

[recoilguy]

Ok,  I'm slow - I just noticed this.....

"What I lack in speed, I make up for with inaccuracy"

I need that on a shirt!

RCG

[deadsh0t]

does it upset you when I post?

RCG

No, but it seems like all you can do is troll.

I would be curious about your results btw

[recoilguy]

Define troll....
ask the same question in as many ways as possible in as many places as you can hoping to sound intelligent and gain acceptance.
nah that's not trolling that's just plain wasting time.

Pointing out that someone wastes everyone elses time.....no that's just be kind.


what results are you curious about LM?
why would you be curious me?
why would anything matter to such an enlightened individual?
oh  just start a new thread, Ill stay out of it I promise. ZZZzzzzzzzz sorry I nodded of reading our last reply....

RCG

[Dan_69GTX]

Gun breaking sooner is all relative.

It is a known fact that hotter loads put a greater strain on the firearm.  So, logic indicates it will wear out/ fail/ break, sooner than if used with lighter loads.   

Hotter loads is more pressure.

To know how much sooner or faster it would break you would need a lot of $$ and an controlled test environment.

[jameslovesjammie]

Shooting lead bullets will not damage or break your gun.  Lead bullets will not harm your barrel, even if oversized.  Even if they are hard cast, which is a fancy way of saying they are an alloy (mix of lead, tin, and antimony) they will put less stress on your gun than jacketed bullets.

Lead bullets require a different approach than jacketed, because they function drastically differently when going down the barrel.  With a jacketed bullet, the lead core is protected from the barrel by the copper jacket, which is much harder and resisst deformation.  A lead bullet is incredibly malleable.  So much so that in a upon firing the base accelerates before the nose starts moving.  This creates a gas seal at the base of the bullet that prevents the super-hot burning plasma from shooting between the bullet and the barrel.

THAT is the main reason that you want a larger diameter bullet...to act as a gas seal.  If the bullet is too small in diameter, the gas will cut the sides of the bullet and escape down the barrel. 

Why does that matter? 
1. You are getting an inefficient burn of your propellant.  Think of it like an old engine that needs new rings on the pistons...smokey, poor mileage, inefficient burn.
2. It damages the bullet.  This leads to poor accuracy at the target.
3. The hot gas will microscopically melt the lead and iron it into place.  This is the main cause of leading when shooting cast bullets.

So we have established that lead needs to be a larger diameter than your barrel.  How big is too big?  If the round won't chamber...it is too big.  I have never seen a 9mm that would not chamber a .358" bullet. 

Does the larger bullet cause an increase in pressure?  Almost certainly.  But why?  Is it because the bullet has more pressure exerted on it upon obduration?  Or does it build more pressure due to a more efficient combustion?  Maybe a little bit of both.  But how much more pressure?  A barely discernable amount.

Now if you were talking about JACKETED bullets...then yes, a safe load could have a large increase in pressure from going up just 0.001" in diameter.  You would not want to shoot .357" JACKETED bullets in a 9mm, but lead bullets are just fine.

[Rcher]

...
Lead bullets require a different approach than jacketed, because they function drastically differently when going down the barrel.  With a jacketed bullet, the lead core is protected from the barrel by the copper jacket, which is much harder and resisst deformation.  A lead bullet is incredibly malleable.  So much so that in a upon firing the base accelerates before the nose starts moving.  This creates a gas seal at the base of the bullet that prevents the super-hot burning plasma from shooting between the bullet and the barrel.

Do plated bullets like Berrys behave the same as lead bullets? And that's why Berrys are 0.356"?
Will plated bullets leave more copper or lead residue? And what type of bullets (FMJ, plated, lead) is more safe for the barrel? For average and below than average loads/velocities?

[Creeker]

Hello

It's advised almost anywhere (with some exceptions) to use bigger diameters, let's say for 9mm when using hard cast / coated / plated.

It will probably guarantee more accuracy. What about the pressures? Any test done? Especially with hard alloys. I've been suggested NOT TO use 357 or the gun will break much sooner (not like 1%). In this case it's a CZ Shadow2 but it doesn't matter. Any idea better than "it should work fine"?

It's hard to find a manometric barrel, so anybody found the opposite, like parts breaking much sooner by using bigger diameters?

I'm NOT talking about FMJ

The idea is : if the slug test gives a .3555 result, then .3555 bullets (of a good quality), should be used. If they fail the accuracy test, the alloy is too bad or the quality is not enough.

I'd like to understand more, since this can't just be tested in the gun

I use the same powder charge in my CZ with .357 or .358 cast bullets. I can tell no difference in the pressure. I'm sure there is a difference but I it must be slight. Since I can't tell a difference I doubt it will break anything sooner.

[Earl Keese]

Hello

It's advised almost anywhere (with some exceptions) to use bigger diameters, let's say for 9mm when using hard cast / coated / plated.

It will probably guarantee more accuracy. What about the pressures? Any test done? Especially with hard alloys. I've been suggested NOT TO use 357 or the gun will break much sooner (not like 1%). In this case it's a CZ Shadow2 but it doesn't matter. Any idea better than "it should work fine"?

It's hard to find a manometric barrel, so anybody found the opposite, like parts breaking much sooner by using bigger diameters?

I'm NOT talking about FMJ

The idea is : if the slug test gives a .3555 result, then .3555 bullets (of a good quality), should be used. If they fail the accuracy test, the alloy is too bad or the quality is not enough.

I'd like to understand more, since this can't just be tested in the gun

I use the same powder charge in my CZ with .357 or .358 cast bullets. I can tell no difference in the pressure. I'm sure there is a difference but I it must be slight. Since I can't tell a difference I doubt it will break anything sooner.

Tell a difference how? Are you using a chronograph?

[Creeker]

Tell a difference how? Are you using a chronograph?

Never fired those loads over a chronograph. Like I said I'm sure there is a difference but comparing cases, they look the same. When shooting, the cases land in the same place. I notice no difference in recoil or report. I just can't tell a difference using my crude means.