Light charges - Possible pressure spikes

[Dudedog]

I have heard that Going below recommend load data can cause pressure issues

Someone asked my opinion on this.
While most of us are not internal ballistics experts or professionals I was curious what other people thought.

I have heard that small charges can "Detonate" as opposed to the normal extremely fast burning,
but I have also heard that there are few if any confirmed "Detonation" incidents due to light charges.

The question was in reference to 9mm loads.
I know people loading for revolvers frequently load quite light, and that is a small charge in a large (compared to charge size) case.

For example Lyman lists a start charge of 3.7gr of 231 in .38 special with a 120gr lead bullet. ~700fps
Light charge, very little case fill.

I think a lot of the listed 9mm data does not go lower than it does because it is assumed that the 9mm is being shot in a semi-auto and the start charge is sort of an estimate on the minimum necessary to get proper function. (forgetting about those 9mm revolver guys)
I would think any charge that is enough to give function should be safe, even lighter is probably ok but thinking gets me in trouble often.
Of course we do need to get the bullet out the barrel.

So everybody your thoughts on this would be appreciated.

 

[ewlyon]

The worry with light charges is typically limited to rifle cartridges with slow burning powders. I figure with handgun loads the minimum charge depends more on what will get the bullet out. If everything else looks good at the lowest charge you have tried then you should be fine going lower gradually.

 

[edwardware]

I can't rule it out on the basis of combustion mechanics, but it sure is inconvenient how hard it is to differentiate between a kaboom caused by detonation of a light charge, and one caused by a double charge.

I've never seen an account of detonation that couldn't be more easily explained as a double charge. I do know that some powders become inconsistent at reduced charges, so inversions in the charge v pressure relationship are not inconceivable.

 

[hdwhit]

Dudedog worte:
I have heard that small charges can "Detonate" as opposed to the normal extremely fast burning,
but I have also heard that there are few if any confirmed "Detonation" incidents due to light charges.

I am not aware of anyone who has yet posited a mechanism by which a small charge of powder can "detonate" that has been experimentally verified and then experimentally verified by unrelated third parties following the same experimental procedure. Until someone does, it is safe to say that there is probably not such thing as "detonation".

A potential problem with 9mm which Speer notes in the comments on the 9mm cartridge in their published manual (page 385 in the 11th edition) speaking about bullet set-back, but intentionally setting bullets deeper than they are supposed to be set has the same effect, is that pressures can rise dramatically; more than doubling.

Someone loading a 9mm round light and then seating the bullet deeper than is specified and experiencing a catastrophic failure might put the failure down to "detonation" even though what they likely experienced was the massive increase in pressure from seating the bullet too low and leaving an inadequate amount of space in the case that Speer discusses. So, if you're going to load 9mm, it is a good idea to observe the COL provided by the manufacturer.

 

[Walkalong]

I have heard that small charges can "Detonate" as opposed to the normal extremely fast burning,
but I have also heard that there are few if any confirmed "Detonation" incidents due to light charges.

It is usually contributed to rifle calibers, and they cannot reproduce it in the laboratory.

9MM? Double charges, over charges, bullet setback. Not detonation IMHO.

 

[Blue68f100]

Like said I agree with the others, as it related to rifle cartridges, not pistol. Not like to ever happen on a small case volume, and fast powders used in handguns. BE shooters start at the min and work down from there, not up. So it it was a problem it would be widely know. The concern is getting the bullet to leave the barrel, and hit the target (not the dirt).

 

[ATLDave]

a lot of the listed 9mm data does not go lower than it does because

They took the measured max and then knocked off 10%. That's what the start load of most manuals will end up being. It's not any kind of minimum load, for most powders, although many people will erroneously call it that. If you want "permission" to load light, my now-1-gen-old Hornady book went way down the scale for some powders. They did not go with the -10% approach.

To be sure, many powders will become less consistent at lower levels. They may even fail to seal the brass to the chamber wall completely. But "detonation"? In a straight-walled cartridge? No. Now stick a bullet in the bore with a light charge and follow it up with another one... that will make a mess. But it's not some crazy, ill-understood, mysterious dynamic at play.

 

[Walkalong]

I have seen three plated bullets stacked back to back to back in a revolver barrel from charges that were too light, and they just kept shooting. The gap obviously let enough pressure off to not harm the gun.

I have seen a bulged 1911 barrel that locked the gun up from a bulged barrel when someone fired a full power round after a squib that left a bullet in the barrel.

Anyone familiar with shopping for old .32-20 revolvers knows to look for bulged barrels. Any revolver can do this, and I forget the story behind all the bulged barreled .32-20s.

I have never seen any of the catastrophic failures like we see on the web from what must be double charges of a fast powder. It happens obviously, and that is why we harp on being careful about charging cases and checking powder level.

 

[ATLDave]

I suppose it is pretty much obligatory to post one of these:



Don't do that. When playing with light loads, make sure you are getting holes in the target! Slow fire until you have put X number downrange without any stuck in the bore or failing to stabilize. What's X? That's up the reloader/shooter!

 

[Walkalong]

I test all light loads powder forward away from the primer to make sure any and all will easily make it out of the bore. I have stuck a bullet or two doing this. Some powders lose a lot of velocity this way. I tried a 125 Gr load in .357 brass that did 900ish powder back, and would stick bullets powder forward. Most are not this bad, but losing 200 or 300 FPS isn't unusual.

 

[clearcut]

Dudedog , Iv'e been using 2.1 grn. Titewad under a cast 125 grn. well below start loads.650 fps.

CC

 

[Walkalong]

I suppose it is pretty much obligatory to post one of these:

View attachment 777206

Don't do that. When playing with light loads, make sure you are getting holes in the target! Slow fire until you have put X number downrange without any stuck in the bore or failing to stabilize. What's X? That's up the reloader/shooter!

Dang, they reloaded and kept shooting.

 

[Doublehelix]

I suppose it is pretty much obligatory to post one of these:

View attachment 777206

Don't do that. When playing with light loads, make sure you are getting holes in the target! Slow fire until you have put X number downrange without any stuck in the bore or failing to stabilize. What's X? That's up the reloader/shooter!

Haha!!! What the heck is that???? Unbelievable that someone would put that many round down the pipe!!! That is a picture for the Gun Hall of Fame for sure!!! Just classic!!!

I laughed my butt off when I saw that!!!

 

[ATLDave]

I test all light loads powder forward away from the primer to make sure any and all will easily make it out of the bore. I have stuck a bullet or two doing this. Some powders lose a lot of velocity this way. I tried a 125 Gr load in .357 brass that did 900ish powder back, and would stick bullets powder forward. Most are not this bad, but losing 200 or 300 FPS isn't unusual.

Really good advice!

 

[ATLDave]

Haha!!! What the heck is that???? Unbelievable that someone would put that many round down the pipe!!! That is a picture for the Gun Hall of Fame for sure!!! Just classic!!!

I laughed my butt off when I saw that!!!

Then you'll love these, too:




Note that the one immediately above, with the ruler on the side, is purportedly a machine-gun barrel.

 

[ATLDave]

Note that all of these squib pileup barrel cutaways seem to involve projectiles with heavy jacketing. If you're going to play around with the really light stuff, maybe FMJ/JHP ain't the way to go...

And here's a bonus one where the gun completed the cutaway on its own:

 

[Armored farmer]

I suppose it is pretty much obligatory to post one of these:

View attachment 777206
Why didnt The air trapped between these bullets blow up the barrel?

Don't do that. When playing with light loads, make sure you are getting holes in the target! Slow fire until you have put X number downrange without any stuck in the bore or failing to stabilize. What's X? That's up the reloader/shooter!

 

[Doublehelix]

Dang! That is just hilarious! I have never seen any of these before... I love that machine gun barrel cutaway!

These made my day!

 

[243winxb]

Pressure Spikes _

CCI has recorded a pressure spike in 9mm when testing primers. They then changed the composition of the priming compound. http://www.shootingtimes.com/ammo/ammunition_st_mamotaip_200909/

The wrong combinations of components in a 257Weatherby rifle can produce the same results, early bullet movement. See photos. https://thefiringline.com/forums/showthread.php?t=535493

Both are caused when the bullet moves to soon. No Kabooms , but it may be possible

with certain smokeless powders with a high-nitroglycerine concentration can be induced to detonate.

https://archives.fbi.gov/archives/a...ience-communications/fsc/april2002/mccord.htm

We may never know for sure?

 

[243winxb]

Mostly reloading errors cause Kabooms. Photo album https://www.thehighroad.org/index.php?media/albums/kaboom.24/

 

[ATLDave]

https://archives.fbi.gov/archives/a...ience-communications/fsc/april2002/mccord.htm

Note that the FBI document here is referencing detonation in the context of bombs, not internal ballistics.

The 9mm story is about a primer issue, not light charges of powder.

 

[Blue68f100]

I suppose it is pretty much obligatory to post one of these:

View attachment 777206

Don't do that. When playing with light loads, make sure you are getting holes in the target! Slow fire until you have put X number downrange without any stuck in the bore or failing to stabilize. What's X? That's up the reloader/shooter!

You would wonder was he that bad of a shot he's missing the Whole Target . So he kept practicing.

What a way to ruin a good revolver.

 

[ATLDave]

Sometimes I shoot (at) targets that are far enough away that I cannot see bullet holes until I retrieve the target.

Don't do that when working up/down light loads!

 

[z7]

I have worked down in 40sw with Bullseye and 180g plates, I wanted some real soft rounds to help the wife start to shoot my 40’s
I went as low as I could shooting with 1 hand and still getting the slide to lock back

For reference I read up in folks going super lite with 38spc with bullseye and then I found this article and I went low slowly until I was happy, they are a real hoot for sure, the case barely ejects and lands on my wrists
http://www.handgunsmag.com/ammo/ammunition_40lite_091806/

 

[dh1633pm]

I loaded some powder puff loads for the 45-70 using a little Unique in a great big case. I used toilet paper as wadding.