Light charges - Possible pressure spikes

[Bill Siler]

Thanks Dudedog posted this for me. I am working up some loads for my daughter for Steel Challenge and didn't want to blow stuff up. I understand I have to get the bullet out of the barrel and it needs to be able to hit the target accurately I was told on Facebook in a reloading group to watch going below the minimum recommend loads in the books.

I have found a few loads that Katie likes thanks to Dudedog I message him a lot thanks for the help Dudedog but if I can slow them down some more and I can I am sure. I have a load with BE 86 4.3 Gr under a 124 GR Extreme bullet doing around 1050 she likes it and I think it makes power factor. I loaded some 115 GR Blue bullets with HP 38 at 4.1 and ended up with a velocity of around 1050 if I remember right. The website shows 4.7 at 1050 I even loaded them longer by a little longer. I know power factor is not needed for Steel but she shoot an open gun at the USPSA match this weekend in Piru and really like it.

Playing around with this stuff is fun. Just trying to be as careful as I can.

 

[ATLDave]

I was told on Facebook in a reloading group to watch going below the minimum recommend loads in the books. .

See, there's the problem right there. You've got people calling start loads "minimum" loads, as if they were a hard stop like the maximum.

Now, there are minimum loads in loading manuals. Go look at the magnum revolver cartridges with H110 data. You will nearly always see a note that says :"DO NOT REDUCE BELOW THIS CHARGE" or something to that effect. That's because they are listing an actual minimum. The other handgun loads that don't have that are listing start loads. Those are a good place to start and work down if you are trying to explore light loads. Go slow, be careful, and pay attention to the risk of stuck bullets. Be aware of the ways in which different variables can make the difference between a stuck and non-stuck bullet. If you are right on the edge of sticking a bullet, then things like temperature, powder position in the case, or even brass headstamp can make a difference.

That said, unless you are running very light springs, most tilting-barrel 9mm's will run into ejection problems before you stick a bullet. That's what often sets the effective lower parameter.

And, as always, proceed at your own risk. I'm just a stranger on the interwebs.

 

[243winxb]

Standard primers caused no ignition issues at the max load but posted higher extreme variations in pressure and velocity in the lower pressure regimes of the start loads. In extreme cases, the start loads produced short delayed firings

Read more: http://www.shootingtimes.com/ammo/ammunition_st_mamotaip_200909/#ixzz56HiuaxZQ

 

[Walkalong]

I was told on Facebook in a reloading group to watch going below the minimum recommend loads in the books.

In all fairness, they have a point, you do need to be careful about going lower, as other factors come into play. It can be done safely, but not in all applications with all powders.

It's an issue we discuss here from time to time.

 

[Walkalong]

 

[Dudedog]

You're welcome Bill.
Thanks also to everybody else who replied.


Not worried about light charges myself, I have went light and had no issues.

If you want "permission" to load light,

Gave it to myself years ago, thanks!


As Walkalong pointed out a powder back round might clear the barrel while a powder forward/powder level round might not.
Probably not as much of an issue in 9mm as say .38 but something to keep in mind and test.

I thought the thread might be helpful for other people thinking about loading light in 9mm.

8 rounds in the revolver, which I am guessing probably only holds 6
Ruined what was probably a nice revolver.

Great Pics but almost sad in a way.....
(except the "machine gun barrel")

 

[ATLDave]

One other note about light loads in 9mm - be really careful if you have a 9mm AR or other long-barreled gun. Barrel length adds velocity until pressure has fallen to the point that the friction of the barrel is greater than whatever push force the bullet is getting from behind. For light loads in 9mm, this may occur over less space than the length of a PCC barrel... and bullets that might clear a pistol's barrel while still accelerating may get stuck in the last few inches of a longer barrel.

 

[Vern Humphrey]

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.

It has been duplicated in the laboratory -- as I recall, while developing loads for the 6.5X55 Swede. As I recall, they got a big pressure spike with one round, and then tried to duplicate it and succeeded.

The mechanism appears to be a charge so small that the primer doesn't fire into the powder, but flashes OVER the powder. The bullet is driven into the lede by the primer, and an instant later the powder ignites. The bullet stuck in the lede acts like a bore obstruction.

Now, as has been mentioned this has only been duplicated with rifle cartridges and it is NOT a "detonation" -- it is a high pressure event.

 

[Dudedog]

Thanks for a couple excellent points ATLDave
what clears a 4" barrel may not clear a 16" one, and in general in a semi auto 9mm if you have function you are not at risk of sticking bullets.

I need to find Walkalongs light charge tests and link to them. ( can't recall how low the vels got before he stuck a bullet but pretty lowww...)

"detonation" was probably a poor choice of words on my part, an excessive pressure event would have been better.
I used "detonation" because that's how some of the occurrences had been reported.

I say excessive because discharging a properly loaded round is a high pressure event.
(as reloaders we can look at say for example a .223 load and think oh, it's only 50,000 PSI or heck for that matter a light .38 load and think boy that ones only 8,000 PSI)