"Starting load" question

[Triggernosis]

I seem to recall someone saying to never load under the recommended starting load. How does loading a round too low cause an excess pressure situation? I'm not envisioning the physics behind it.


Yes, I understand that if you load too low and stick a slug in the barrel and follow it up with another round that bad things are likely to happen......

 

[SMSgt]

When I start working up a new load, I start at the mid range of the load data. I never have found a need to go to max, mid-range or slightly high giving me the best results.

 

[arjay]

The whole detonation thing is a myth IMHO
Easier to blame it on that than admitting to a triple charge of Bullseye [emoji38]

 

[fredj338]

The whole detonation thing is a myth IMHO
Easier to blame it on that than admitting to a triple charge of Bullseye [emoji38]

The detonation theory has never been proven or duplicated in a lab. The reason to not go below starting data is you could stick a bullet but with some really slow powders, you could get a hangfire.
I load below book starting data often with uberfast powders for 9mm & 40 minor. Hell I load off the book with several powders in several calibers as there is no data available.

 

[Rule3]

I seem to recall someone saying to never load under the recommended starting load. How does loading a round too low cause an excess pressure situation? I'm not envisioning the physics behind it.


Yes, I understand that if you load too low and stick a slug in the barrel and follow it up with another round that bad things are likely to happen......

Primary what you said about a squib. A squib is really defined as a under powered load, it doesn't have to stick in a barrel.

In a semi auto a weak load is not going to cycle the gun properly.

What happens with under powered loads is they may not be a a stuck in the barrel but you will get poor burn or detonation. This leads to crummy performance lots of soot, carbon and fouling, It can vary a lot depending on the caliber and powder,

Also load data is all over the place depending on what source so what is the "correct" start load??

 

[mikld]

All depends on the powder. H110/W296 are not to be "down loaded" or go below "starting loads" by the manufacturer's recommendations. Slow powders in a large case may (or may not) cause detonation, but more common erratic burn/pressures with incomplete burn and possible "squibs". Other powders may be more "position sensitive" so lighter loads take up less room in the case and the position of the powder upon ignition may cause huge variations in pressure/velocity.

 

[Qc Pistolero]

As far as I remember,different labs have tried over the years(decades)to duplicate the detonation phenomena without ever achieving it.I've read official reports all going the same way;there just isn't enough energy stored in a sub-minimum charge of powder to blow up a gun.
Qc

 

[SLT223]

Going below minimum loads means you may fail to achieve necessary pressure for good combustion. This can result in a squib.....not a magical transformation to Composition B as the interweb may have one believe.

 

[Wise_A]

Agreed. Sometimes the "Starting Load" is fairly close to a "critical failure" of the burning process, as in the slowest of handgun powders. Sometimes, the starting load is where the lab in question first found consistent-enough pressure data. Sometimes, it's almost completely arbitrary.

Whether I use it depends on what I'm trying to do. If I'm trying to make low-recoil ammunition, I go with the starting data, or sometimes under it. If I'm not, I happily jump straight to the midrange.

 

[Triggernosis]

What is this "detonation theory" y'all speak of?

 

[muddocktor]

What is this "detonation theory" y'all speak of?

The theory is (if I understand correctly) that with a low load of powder in a relatively large case such as a 357 or 44 mag case, instead of burning progressively the powder ignites all at once like a high explosive and pressure spikes tremendously. I don't think this can happen either, BTW.

 

[MJFlores]

I thought I read somewhere that a manufacturer was able to dupicate the detonation theory. This is why Ive avoided Titegroup in larger cases.

 

[ChiefStealth]

I seem to recall someone saying to never load under the recommended starting load. How does loading a round too low cause an excess pressure situation? I'm not envisioning the physics behind it.

It doesn't cause excess pressure. It can cause other problems, but not pressure.

 

[SLT223]

What is this "detonation theory" y'all speak of?

OK, there's two basic excuses for blowing up your gun that has nothing to do with you, or science for that matter, and ENTIRELY to do with unreplicated exothermic behavior of smokeless powder.

1) Flash over: As folklore has it if you have a small charge of fast powder in a large case, the primer flash jumps over the charge causing it to burn from both ends. The problem here is that there is simply not enough fuel to cause a problem. The reality is someone double charged their ammo with fast powder which easily fits in even small cartridge cases. It's easier to invent unproven, unreplicated, reasons for why the gun blew up than to admit failure.

2) Detonation: This gem of a story is usually associated with short charging very slow powders. What really happens here is a short charge of slow powder fails to achieve sufficient pressure to burn anywhere near completely. Sometimes the bullet lodges in the barrel. Our unsuspecting short charger fails to acknowledge the squib he just squeezed off, and squeezes again. The next round doesn't fail, and now the 40,000psi expands for three inches where it's stopped suddenly by a bore obstruction. The powder keeps burning. In a flash the pressure goes from whatever, to exceeding the strength of the gun's steel. Well yeah, the gun went high order, but it's because the barrel was squibbed, not because the exothermic behavior of the propellant changed to that of HE because of loading density.

 

[Nevada Ed]

+1 on post #4.

I have gone over and under the manuals data but I also have a chrony
and heavy, well made weapons.
I have yet to stick a bullet or blow up a pistol or revolver.
However I have locked up a bolt on a rifle on a hot summer's day.

As for detonation, I believe that pertains to a long rifle case that has less
than 50% of powder in the case and the primer lights up the top layer
of power, instead of just the base, as it is intended to do.

The small pistol cases, I believe, do not have enough volume with a bullet seated to be able to duplicate the same effect.
As for sticking a bullet in a hand gun...........
Most rapid fire ammo is not of the low pressure, low fps type.
Most is at 90% of a maximum loading, even with target ammo.

It is most often a low vel. hand loaded ammo that gets people into trouble.
It is wise to look for dust or a bullet hole, before pulling the trigger again with "Blooper" loads.

 

[rwsmith]

I've loaded underpowered round...

Agreed, detonation from small charges is a myth. But what you DON'T want to do is stick a bullet in the barrel. I've even made some under powered loads for a 9mm semi, but they were still able to cycle the action reliably. I was tempted to go lower but I saw no need because I was looking for a training round for my wife and those loads not only felt good, they were as accurate as could be. Heavy bullet, low velocity, low recoil. Most accurate load I've made for semi pistols.:D

The 'detonation of small charges' thing was invented by people who didn't want to admit that they double charged Bullseye.:D

 

[rwsmith]

In a word, No.

I thought I read somewhere that a manufacturer was able to dupicate the detonation theory. This is why Ive avoided Titegroup in larger cases.

The problem with Titegroup is the same as with Bullseye. A little too much powder goes a long way toward blowing up your gun. You have to be very careful when using tiny charges of fast powders. The fast powders are great target shooters, and very economical to use (2.8 gr. of Bullseye with a 148 gr WC) but many people don't want to risk a ruined gun, hand or more. Therefore they stick to bulkier powders. Trail Boss is the ultimate. You CAN'T overcharge a case with Trail Boss as long as you don't compress the powder in a load.

 

[rwsmith]

That first one is hilarious...

OK, there's two basic excuses for blowing up your gun that has nothing to do with you, or science for that matter, and ENTIRELY to do with unreplicated exothermic behavior of smokeless powder.

1) Flash over: As folklore has it if you have a small charge of fast powder in a large case, the primer flash jumps over the charge causing it to burn from both ends. The problem here is that there is simply not enough fuel to cause a problem. The reality is someone double charged their ammo with fast powder which easily fits in even small cartridge cases. It's easier to invent unproven, unreplicated, reasons for why the gun blew up than to admit failure.

2) Detonation: This gem of a story is usually associated with short charging very slow powders. What really happens here is a short charge of slow powder fails to achieve sufficient pressure to burn anywhere near completely. Sometimes the bullet lodges in the barrel. Our unsuspecting short charger fails to acknowledge the squib he just squeezed off, and squeezes again. The next round doesn't fail, and now the 40,000psi expands for three inches where it's stopped suddenly by a bore obstruction. The powder keeps burning. In a flash the pressure goes from whatever, to exceeding the strength of the gun's steel. Well yeah, the gun went high order, but it's because the barrel was squibbed, not because the exothermic behavior of the propellant changed to that of HE because of loading density.

That first one is hilarious. The second is the reason that magnum primers are recommended for many slow powders. They are harder to light and can burn poorly if not well ignited.

 

[hdwhit]

Triggernosis wrote:
How does loading a round too low cause an excess pressure situation?

Several people took your "excess pressure" question, immediately jumped to detonation and exploding guns and started discussing that.

Very small powder charges may, depending on the cartridge, fill only a small portion of the volume of the case. Depending on how the gun is handled after the cartridge is loaded, the powder could all be near the flash hole, all be near the bullet or spread out in between. This can lead to inconsistent ignition. If the flash from the primer initially ignites only a portion of the powder and the combustion wavefront has to propagate through the remainder while the pressure and temperature inside the case have already started rising, it can change the rate of combustion of the remaining powder.

The result is that one round that "normally" might generate, say, 8,000 psi and barely push the bullet out of the barrel while the next round combusts as described above generates 13,000 psi which makes it seem more powerful than would be expected for the size of the charge.

Neither of these rounds is "excessive" in the sense that the pressure reaches, much less exceeds, the limits of the cartridge or the gun, but the inconssitency can be enough to give that impression.

As far as "detonation", I concur with the rest of those who have posted that nobody has posited a mechanism by which it can occur that can be demonstrated experimentally and until that happens, it should be regarded as little more than mythical.

 

[mtgianni]

What is this "detonation theory" y'all speak of?

SEE or Secondary Explosion Effect is believed to happen when a charge ignites , the bullet starts to move is momentarily slowed in the forcing cone and the resultant pressure then causes the powder to fully burn and spike. It may have been duplicated in a factory but if so it was not well documented or released to the general public. With proper combustion the resulting powder burn/pressure wave sends the bullet through the forcing cone and bbl with no secondary pressure wave resulting in a smooth, spike free, pressure curve.