Cartridge Overall Length

I'm still trying to work up reliable handloads for my wife's Glock 42 (HP-38 powder, 100-gn FMJ bullets). (Up to now, the 3.1 grains maximum given by Hodgdon doesn't cycle the gun reliably. I'm about to go to the range to try out some with 3.2 grains of powder, and some with 3.3 grains -- the maximum according to Hornady.)

I've been seating the bullets at 0.980" C.O.L, as given by both Hodgdon and Hornady.

I know that C.O.L. that's too large can hang up in the magazine; on the other hand, C.O.L. that's too small can cause pressure issues, particularly since I'm at the high end of the recommended charge.

On the third hand, I see references that a lot of people seat their bullets deeper than 0.980" for the G42; and the couple boxes of commercial .380 FMJ ammunition I still have measure 0.970" or even less...

Some reloading sources say that recommended C.O.L is not-less-than, and some say it's not-more-than. Which is it? Or is it just a starting point?

Plunk test. Take the barrel out of the Glock an test your dummy rounds. If they fit it works.

303_enfield said:

Plunk test. Take the barrel out of the Glock an test your dummy rounds. If they fit it works.

Click to expand...

Yup the plunk test, when reloading for my khar 40 s&w I found the over all col needed to be a bit shorter. Your cases trim length needs to be correct too. The col in the loading books in many cases needs to be tweaked.

For example my case trim length for 45-70 using 350 gr for berry's is the same as Hornady 325 gr FTX.

The best thing to do is plunk test MFG shell and see how it fits. Then plunk test your reloaded case. If the reloaded case sticks and does not slide out press the projectial dow bit by bit until it fits correctly.

I have made pattern cases for all my reloads with mic readings on the cases. Also, have pattern dummy rounds .

You could also work "up" the load, but making them shorter in small increments.

Same idea of working up the charge, to slowly raise the pressure, looking for pressure signs.

I would probably drop the charge by .1 or .2, then shorten, then work back up.

Re: plunk test. Yeah, that would detect whether a cartridge is (way) too long, but not if it's too short...?

Pinecone said:

You could also work "up" the load, but making them shorter in small increments.

Same idea of working up the charge, to slowly raise the pressure, looking for pressure signs.

I would probably drop the charge by .1 or .2, then shorten, then work back up.

Click to expand...

That's what I was thinking. Drop charge by 0.1, and shorten C.O.L. by about 0.010" (one-hundredth), down to 0.97"...? If I still have feeding problems?

Mark K said:

Re: plunk test. Yeah, that would detect whether a cartridge is (way) too long, but not if it's too short...?



That's what I was thinking. Drop charge by 0.1, and shorten C.O.L. by about 0.010" (one-hundredth), down to 0.97"...? If I still have feeding problems?

Click to expand...

You will get feeding issues when you get too short.

For feeding, you can make some dummy rounds shorter and shorter and see how short will feed.

My cousin shoots a S&W EZ 380.

Tried the loads in the book from min to max powder W231 (HP38). Until I hit the MAX load, would not cycle. At MAX load it was NOT reliable.

Final working load is 3.2gn of W231 @.972

.972 was from a factory load she purchased. Work GREAT

radnor said:

My cousin shoots a S&W EZ 380.

Tried the loads in the book from min to max powder W231 (HP38). Until I hit the MAX load, would not cycle. At MAX load it was NOT reliable.

Final working load is 3.2gn of W231 @.972

.972 was from a factory load she purchased. Work GREAT

Click to expand...

Interesting. Of course, that's a S&W EZ 380, and we've got a Glock 42. A lot of people have apparently found that G42s really like hot loads, and won't cycle reliably with less. Which is what I've found.

With the G42 yesterday, I was still getting a couple of cycling issues with 3.2 grains. And no problems at all with 3.3 grains (0.980 COL).

Might be worth for me to try stepping down a tenth of a grain to 3.2, and shortening the COL down to 0.072" or 0.070"...

Have you tried factory ammo recently to rule out a problem with the gun? No chance of limp wristing?

Pinecone said:

You could also work "up" the load, but making them shorter in small increments.

Same idea of working up the charge, to slowly raise the pressure, looking for pressure signs.

I would probably drop the charge by .1 or .2, then shorten, then work back up.

Click to expand...

Art3 said:

Have you tried factory ammo recently to rule out a problem with the gun? No chance of limp wristing?

Click to expand...

I've, um, only got one box of factory FMJ ammo left. Which is why I'm reloading. A lot.

I did try one magazine of cheapo Estate Range & Target ammo yesterday -- no function problems. That takes me down to one 50-round box of the stuff.

I do have some SD ammo left, but I'd rather not burn through that. I did try some to make sure we've got SHTF function, and we do.

Limp wrist shouldn't be a problem. I always shoot two-handed, and have been paying a lot of attention to arm and wrist tension. Plus I've been firing supported a lot.

Per your suggestion, it’s worth a try dropping it a tenth and progressively shortening the COAL. But really that only helps mostly if it’s a cartridge length giving you a problem. Reducing the powder charge 3% (.1gr) is going to require a volumetric deduction of around 5%* to hit the same peak pressure if I have things figured right (less powder taking up space, but also less energy from powder burning creating hot gas).

But that’s only peak pressure, that isn’t total energy imparted in to the projectile. You’d gain less.

*please note I am referring to case volume, not COAL. A 1% reduction in COAL might be a 2-3% reduction in case volume.

.01” at a time reduction isn’t a bad way to go about it.

IMHO do what others have suggest. Plunk test the barrel. If you make 3 carts and they all drop fine and seat fully and aren’t getting jammed up if you tap the back of the cart in to the barrel some (as in drops free) then you know your COAL is fine (or should be).

Make a bunch of dummies if you need to. Been times I’ve had to load up 20 or so dummies to get a COAL a barrel has liked. You just pull them apart and work from there. Could also be too much or too little crimp. Which a plunk fest can also help you see if there is resistance with it dropping in to or out of the chamber (might not be fully taking the case belling out or something).

For your earlier question on COAL. What does the reloading manual say? COAL listed is either test length, SAMMI max or min. Some reloading manuals have all three for you. If all you have is one number, it is tested COAL.

The max powder charges are based on their test COAL. If it’ll run, you can run whatever COAL you want so long as it fits in your chamber. Check a 38sp. There is a whole lot of difference between a truncated come and a wad cutter for COAL. You CAN load a 9mm super short if you used a real mild powder charge. Want to run a COAL or .900” with a 90gr bullet for 9x19 you probably safely could with say 2gr of bullseye. Might not cycle the gun and might have freeing issues depending on the Magazine and specific gun, but it will chamber and shouldn’t cause pressure issues.

I am not suggesting to suddenly go wild. Max COAL is the larger concern. Beyond that and you aren’t likely to be able to get the round to work if the gun in question is using a SAMMI spec chamber and mouth. Spoilers, some guns are cut tighter than SAMMI spec. Why we say plunk test. See what your’s is.

Mark K said:

I'm still trying to work up reliable handloads for my wife's Glock 42 (HP-38 powder, 100-gn FMJ bullets). (Up to now, the 3.1 grains maximum given by Hodgdon doesn't cycle the gun reliably. I'm about to go to the range to try out some with 3.2 grains of powder, and some with 3.3 grains -- the maximum according to Hornady.)

I've been seating the bullets at 0.980" C.O.L, as given by both Hodgdon and Hornady.

I know that C.O.L. that's too large can hang up in the magazine; on the other hand, C.O.L. that's too small can cause pressure issues, particularly since I'm at the high end of the recommended charge.

On the third hand, I see references that a lot of people seat their bullets deeper than 0.980" for the G42; and the couple boxes of commercial .380 FMJ ammunition I still have measure 0.970" or even less...

Some reloading sources say that recommended C.O.L is not-less-than, and some say it's not-more-than. Which is it? Or is it just a starting point?

Click to expand...

I was doing the same thing with Berry’s 100 gr and had the same issue. The HP-38 just wouldn’t cycle the action. I switched to 3.1 gr of Bullseye and so far it has been 100%. I could be wrong, but after looking at the pressure data for HP-38, it seemed to be fairly low in the list of powders.

In my gun store journeys , I see more selection of Powders on the shelves than .380 ( or 9x19) ammo . Just saying .

lazarus said:

Per your suggestion, it’s worth a try dropping it a tenth and progressively shortening the COAL. But really that only helps mostly if it’s a cartridge length giving you a problem.

Click to expand...

Plunk testing seems to be all good now. Only problem I had before was with cases that I'd pulled bullets out of, and then apparently hadn't taper-crimped them enough.

I was just asking about COL because a lot of (Internet) people had apparently had good luck with G42s and COL in the 0.96" range.

lazarus said:

For your earlier question on COAL. What does the reloading manual say?

Click to expand...

My Hornady Handbook says C.O.L.: 0.980" for 100-gn FMJ, for all powder types. But it doesn't say if this is a max or minimum length, and no mention in the discussion in the front of the book.

Hodgdon shows C.O.L. 0.980.

And the data with my Lee dies show Min OAL 0.980. Which to me means no shorter than.

So those three sources are at least consistent in this.

I don't use Alliant powder, but they don't give load data for 100-gn bullets at all.

I also don't use Western powders, but they curiously show COL as 0.960 for 100-gn RN bullets and all their powders.

So maybe I won't fool around with COL shorter than 0.980 for now, which is what most of my references show...

kmittleman said:

I was doing the same thing with Berry’s 100 gr and had the same issue. The HP-38 just wouldn’t cycle the action. I switched to 3.1 gr of Bullseye and so far it has been 100%. I could be wrong, but after looking at the pressure data for HP-38, it seemed to be fairly low in the list of powders.

Click to expand...

Yeah, HP-38 doesn't seem to be extremely hot/energetic. What loads were you using with the HP-38, and what kind of gun?

Because it seems that 3.3 grains of HP-38 is working the Glock 42 reliably now. My other .380s seem to work well with about 3.1 grains (Bersa Thunder 380CC) or even 2.9 grains (1980s-vintage PPK/S) of HP-38. Note both are direct-blowback guns, which is kind of counter-intuitive...

In any case, I've got about 7-1/2 pounds of HP-38 sitting on the shelf now, and that's what I need to use for now...

Um, like I mentioned, I'm noticing a bit of muzzle flash from the Glock 42 with the 3.3-gn loads. Any issue with that?

It's not counter intuitive . It's takes more energyy momentum to unlock a locked breach action than to set a direct blowback slide into motion , kind of the whole point of the thing .

If your controlling parameters include huge stocks of HP-38 and 100gr fmj , then it looks like your solution is dedicated loads for each of your guns .

Biggfoot44 said:

It's not counter intuitive . It's takes more energyy momentum to unlock a locked breach action than to set a direct blowback slide into motion , kind of the whole point of the thing .

If your controlling parameters include huge stocks of HP-38 and 100gr fmj , then it looks like your solution is dedicated loads for each of your guns .

Click to expand...

I would say that you have it backwards.

With a locked breech, you have time helping, so that the bullet has exited the barrel and pressures dropping by the time the breech unlocked.

With blowback, the only thing keeping the breech closed for the bullet to exit is the mass of the slide and the stiffness of the spring.

Take a locked breech and blowback pistol in the same caliber and rack the slide. Which is easier.

Biggfoot44 said:

If your controlling parameters include huge stocks of HP-38 and 100gr fmj , then it looks like your solution is dedicated loads for each of your guns .

Click to expand...

With shortages these days, my choices are limited. Besides, HP-38 is a common powder for .380, and 100-gr FMJ is not that uncommon -- pretty rare in commercial ammo, but readily available (or used to be) as projectiles. That combination isn't that weird...is it?

Locked-breech vs. direct-blowback... There are obviously a lot of factors that go into a gun's design other than slide mass and spring stiffness. The gun's designer has to balance all these. The point is, once all these factors are balanced, theoretically all .380 handguns should function with typical .380 powder charges, all other things (bullet shape, etc.) being equal. With commercial ammo, most ammo-specific problems seem to be with bullet type and shape -- meaning feeding problems.

With standard recipes, I shouldn't need to have certain powder loads for certain guns...but apparently I do.

Again... Muzzle flash not an issue? As long as that's the load I need to function the G42 reliably?

Plunk Test Question

Please pardon my ignorance. I am assuming that a "plunk test" is placing a cartridge into a barrel chamber without using force to determine if the cartridge will freely enter the chamber and seat to the correct depth.
If my assumption is true and one uses a cartridge which headspaces on the case mouth, then the over all length (OAL) of such a cartridge may grossly exceed the recommended OAL and not fail the "plunk test" until the bullet hits the lands. Is this true?
JB