Semi-auto function ponderings

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film495

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I'm new to reloading, and have been tinkering with loading .32 ACP. I have a few things to do there, but haven't had time to really sit down and do the work.

I was reading a little on pistols and in all honesty it still seems kind of amazing to me that the mechanisms actually work, and reliably at that. So, I was reading a little on old Browning pistols and it seems some of them were the same pistols and barrels for .32 ACP and .380 ACP, they just bored the barrel and chambers different.

So, that got me to thinking - if you had a pistol that was structurally designed to handle .380 ACP pressure, what would happen if one loaded .32 ACP up to the .380 pressure? What would the risk be and what would the signs be of over pressure? In theory anyways, if the barrels were the same, the .32 ACP barrel and chamber would have more metal and again - theory only, be able to handle more pressure than the .380 counterpart, due to the additional material.

In digging into that - and wrapping my head around how these things work, basically one would notice signs of case expansion at the head just over the rim, because the case would start out of the chamber while the pressure was still to high, yes? The failure would be a matter of timing, and the case would be the weak link, no?

I'm thinking of the FN Model 1910, by John Browning - and if the slide is the same weight between the .32 ACP and .380 ACP, there must be a wide margin of tolerance in the timing for the action to still work correctly.

The current SAMMI pressure ratings are 15,000 and 17,000 CUP for .32 and .380 ACP respectively. What is the missing piece, does the additional contact area of the .380 case to the chamber delay the slide action? I guess I'm just surprised that the same weight slide and components would work with the different cartridges, and the action and timing would all still work correctly.
 
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Think you would run into some issues. Being 380 pressure capable may not include anything but the barrel and chamber. The higher pressure could be bad for other things. For one you most likely need a heavier recoil spring to keep the slide from slamming open and to make the timing correct. Other wear issues may need to be addressed.
 
The problem is 2000 PSI different isn't huge but that never stops anybody. look at all the threads about loading 45 Long Colt to 44 magnum pressures a little bit is never enough. The best and most realistic answer is if you need more buy a bigger or more powerful gun. Downloads for saftey make sense, going +p in a gun over 50 years old is just begging for trouble.
 
How would you even know if your charge was sufficient to raise the pressure to 380 levels, or if it was beyond. You are dealing with a case that's quite a bit smaller. I would think it wouldn't take much to increase pressure more than intended
 
Jonesy814 said:
How would you even know if your charge was sufficient to raise the pressure to 380 levels, or if it was beyond. You are dealing with a case that's quite a bit smaller. I would think it wouldn't take much to increase pressure more than intended
Click to expand...
don't know, that's part of what I'm trying to learn about. the CIP spec for .32 ACP, is a higher MAP psi or cup than the SAMMI for .380 ACP numbers
, so - I guess it partly depends on who's data you're looking at.

how do you know in a semi-auto if the pressure is too low? I had one factory us ammo, seem to shoot combustion sparks like a sparkler out the ejection port. it cycled and shot fine, so - I didn't think to much of it, figured it was probably normal. although, now that I'm learning more - is that a sign of too low pressure and the case not sealing to the chamber fully? or could this be a result of too high pressure as a little bit larger SAMMI spec bullet diameter hits 7.65 browning rifling?

uggh - I really need to slug this bore.
 
film495 said:
seem to shoot combustion sparks like a sparkler out the ejection port.
Click to expand...

Burning particles from the slow powders used to keep pressure low. Are your cases very sooty? No. The case mouth was sealed, but it does open with pressure in it still. That's what is sparking out.

film495 said:
The failure would be a matter of timing, and the case would be the weak link, no?
Click to expand...

Nope.
In this case the pistol will be. The case head won't expand until you are so far over pressure you're wearing a slide for a hat.
I get what you are saying, a 32Super would be neat. But there is more to it than just case pressure.
 
I could MAYBE understand your desire to increase things if the pressure window was greater, like 10,ooo. But 2,000 is just little over 10% more than that for the 32. So if you increased the powder from a max charge of “X” powder from 5 to 5.5 that isn’t much of a safety factor. And besides, when dealing with propellants/explosives the ingredients don’t necessarily work in a linear fashion.

Why would you consider risking not only destroying your gun, but your body parts as well? Now if you have your own ballistic lab, that’s another matter.
 
Reinz said:
And besides, when dealing with propellants/explosives the ingredients don’t necessarily work in a linear fashion.... Now if you have your own ballistic lab, that’s another matter.
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This is a really important point that many people do not get. You can't just "draw a line through it" and assume that pressure will continue to increase at some proportional rate. Burn rate is variable (this is why different burn rate charts don't all match)... and it varies differently for different powders.
 
Buffalo Bore sells "32 ACP +P" with a claimed 100+ fps gain over standard and with a slightly heavier bullet.
The problem is, there is no recognized specification for .32 ACP +P, they are just loading to what they think the guns will stand.
They have test equipment (don't they?) and the wide selection of bulk powders available to industrial loaders, so at least they know how much they are overloading the round. You wouldn't.
 
I am not a smart man, but i would never load something more then what it is designed for. If i wanted a 32 auto to be loaded to 380 specs. I would see what it would take to convert it to 380 before i loaded over the max.
 
The root of the conversation is how would you even know if you were over or under pressure. The bullet's I have don't come with published data. So, using some other data, of a different bullet type can be done, but is it good? What indicators would come from the gun or cases that one is over or under pressure? I don't know what to look for, that is what I was getting at.

There's a lot of rifle info out there on looking for pressure signs - just haven't run across much for semi-autos other than fails to cycle. I also found one resource that indicated expanded cases at the head was also a sign of over pressure. Are there other things to observe and look for?
 
Conventional wisdom might lead one to conclude that the pistol in general and the barrel in particular would be fine but even if that were the case, one might still run into issues with the .32 cases.

Not an uninteresting avenue to explore if one has very good diagnostic skills and a proper chronograph.

Todd.
 
ApacheCoTodd said:
Conventional wisdom might lead one to conclude that the pistol in general and the barrel in particular would be fine but even if that were the case, one might still run into issues with the .32 cases.

Not an uninteresting avenue to explore if one has very good diagnostic skills and a proper chronograph.

Todd.
Click to expand...

And a ransom rest with a remote firing mechanism!
 
film495 said:
The root of the conversation is how would you even know if you were over or under pressure.
Click to expand...

Pressure-Trace II and other specialized equipment...

Primers and brass don’t talk to you, in a pistol, until it’s too late. Pistols don’t operate at high enough pressures to flow primers. Brass doesn’t begin to flow until high RIFLE pressures. If you have that in a pistol, don’t do it near me...;)


ApacheCoTodd said:
Not an uninteresting avenue to explore if one has very good diagnostic skills and a proper chronograph.
Click to expand...

But what would you compare the chronograph results to?
Knowing that it only clocks speed and not the pressure to get it there.
 
Demi-human said:
Primers and brass don’t talk to you, in a pistol, until it’s too late. Pistols don’t operate at high enough pressures to flow primers. Brass doesn’t begin to flow until high RIFLE pressures. If you have that in a pistol, don’t do it near me...;)




But what would you compare the chronograph results to?
Knowing that it only clocks speed and not the pressure to get it there.
Click to expand...

"Too late" would be a result of failing to build the load incrementally.

Speed being product of pressure and a couple of other particulars is worthwhile and comps would be to established published knowns along with one's own diagnostic standards set prior to re-loading.

Todd.
 
challenge is there is no published load data for the Berry's bullets I have. most similar on Hodgdon's 2.1-2.3 grains Win 231
the bullet manufacturer lists Sierra 2.0-2.4 grains Win 231​
then there are various charges from 1.7 to 2.8 of Win 231 with other variables, bullet weight etc.
then there are some CIP based loads that post higher velocities, but none with Win 231 to compare to

so, in theory anyways - and I don't own a chronograph currently. if one were to make a series of loads with various charges, say 10 each, and then average those velocities and chart them against incremental load increases, I kind of assume there is a point of diminishing returns and/or where velocities become erratic as the load increases. In theory anyways, one could discover that velocity falls off or some other unexpected behavior - inside the closest published load data I can find. Could also adjust COAL as well and chart multiple variables and examine. Could also adjust bullet diameter, crimp, there are a lot of variables, cartridge length.

The idea being to just learn about the mechanism and what makes a good load and what does not.
 
"Just that little bit more” may feel like a slight increase in recoil, but it translates to several thousands of pounds at at time.
More so in a smaller cartridge. The volume of space in the case under the bullet leaves less room for error to create proper operating pressure, while staying under design failure limits, which may be quite a bit less than the material failure points in any given category.

If you are worried that using an unpublished bullet will blow your hand off, that’s different.

To that, I ask, are you speaking Portuguese right now? How about Dutch? Polish?
Ok, don’t get mad.:)
Use Hodgdon’s data you have that is close and be happy.:thumbup:
A thirty caliber hole in something right where you want it will beat a faster miss.
You won’t make this little guy any more lethal than he is, he’s already there.
But, if you don’t beat your pistol to death with over pressure, you can train with these puny power houses until you are the most lethal thing in eyesight!


You know, if you keep yours...:D
 
Pressure is one factor and you must understand relative to a blow back action what the word pressure means.
Pressure is defined as a measure of the force applied over a unit area. Pressure is often expressed in units of Pascals (Pa), newtons per square meter (N/m2 or kg/m·s2), or pounds per square inch
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Let me ask you this. Are the unit areas relative to the breach face identical in .32 ACP or not. Of course they are different. So for the same pressure the .380 will tend to unlock a slide or push back with more backward thrust, especially if its pressure is higher.
Many of the heavier straight blow guns first made in .32 ACP had enough of a safety margin engineered into them that they could function with the .380. In some cases you can exceed factory .32 ACP loadings, but I caution one not to do it. At best you can measure velocity with a chronograph, but most people do not own a pressure barrel or transducer to measure actual pressure and even if you did, one does not know what degree of pressure of above SAAMI specs is safe.
Note as one starts exceeding pressure things like extractors, ejectors, and other parts are apt to fail. Just not a good idea. Not saying that one can not do it, just not a wise, prudent thing to do without some knowledge.
The frommer stop pistol in .32 was said to have been designed to use a special higher pressure loading, but it is full length recoil system.
Muzzle velocity280 m/s (919 ft/s)
Click to expand...
Frommerstop.jpg
 
Is this really a thread about hot rodding the .32 ACP?

How about a follow up on the .22 Short Magnum?
 
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