9mm COL & Minimum Overall Length Questions

[Foto Joe]

I discovered a significant issue with Overall Length on the 9mm's that I have been loading. Yes I'm a beginner at 9mm and for that matter on smokeless cartridges so please understand that I realize I have made a LARGE error.

Gun: S&W Model 39-2
Powder: Universal
Primers: Winchester
Bullets: 115 LRN (Bear Creek)

In the previous thread that I started 9mm Tips & Traps, I mentioned that I had an overall length of 1.165. This was not correct it was 1.070, yeah, not a small goof on my part probably because I wasn't wearing those stupid bifocals! I realized this today while loading the first few of 50 or so with the correct glasses on my face. I reset the bullet seat to 1.100 which is the Hodgdon spec for C.O.L.

After loading 8 I loaded the magazine (I know, they should have been dummy rounds but I'm the dummy here:banghead and put it in the gun. I snapped the slide release and the first round loaded. I then attempted to pull the slide and here's where things got messy. The slide didn't want to come back so I jettisoned the magazine (by the way, I was bright enough to make sure the hammer break was engaged) and then PULLED the slide. What I got was an empty brass and 4.2gr of Universal all over the inside of the gun. The 115gr LRN stayed nicely stuck in the forcing cone and needed to be driven out with a light tap.

Needless to say COL of 1.100" is too long for a S&W Model 39-2 and using the gun for a bullet puller is not recommended.

Loading dummy rounds I finally got a maximum OAL of 1.082" +/-.001". This OAL loads and cycles just fine. Now here's the part that's got me spooked. Minimum Overall Length on smokeless is in my understanding EXTREMELY important, especially with high pressure rounds like 9mm. The shortest Minimum OAL I've found reference to is 1.100" and it's not with the bullet I'm using. Granted, because I screwed up in the first place I've already fired about a 100 rounds of the 1.070" loads out of the gun with no obvious ill effects, yet.

Why is it that Lee for example on thier data sheet that comes with dies states a definitive Minimum Overall Length for all load data that they provide (Universal ain't one of 'em by the way). Hodgdon on the other hand only states a C.O.L. but doesn't state for us beginners if this is a maximum or a minimum.

I do a lot of Black Powder cartridge loading and I'd like to continue to do so and I'd like to have both of my hands intact to do it. So in the interest of NOT blowing myself up I'd like some feedback on the above questions.

Thanks in advance,

 

[Oyeboten]

Hi Foto Joe,


As I understand it, the critical Metallic Cartridge OAL for any given Bullet and Charge is just that...so, for any given Bullet, the correct OAL for a given charge will be particular...and, as charges and or bullet lengths and weights go up, the OAL eventualy becomes a critical matter with respect to Pressures or pressure/duration.

Smaller Lighter Bullets of course, do not fit as far into the case for Cartridges that are to be used in Automatics, as would heavier longer Bullets...since, for Automatics the OAL is also a factor in how well or properly the Bullet will chamber, as you know.

My own naive opinion, is that the tiny bit more OAL you ended up with ( for these Lead Bullets to chamber correcty,) will not matter in any critical way, unless you are at or above Max Charges for that Bullet, where, such teeny differences probably should be regarded as mattering seriously.

Jacketed or FMJ Bullets at max charges, especially as the initially resist more in the Bore than do Lead, I would say the OAL definitely best not end up significantly short, for fear of it increasing the then already impendingly unforgiving if of course still somewhat eleastic limits of prudence and or Metalurgy, for respecting the Loading Density one would have going then.

Lead Bullets, especially light ones, if seated .018 of an inch too low from Loading Table Spec for medium/moderate charges, even if in a short Cartridge Case, such as your 9mm, in my imagination anyway, should cause any troubles.

Or, what it will be in effect, is a somewhat increased Loading Density, hence, a somewhat increased Charge/pressure being realized, for the increase in loading density.


If the same charge for that Powder is in the Books, for a longer Heavier Lead or Jacketed Bullet, or even same weight and shape Jacketed Bullet, you can then be sure then that you are not in any troubles with what you have, since the longer heavier or same weight/shape Jacketed Bullet would be enjoying a higher loading density or initial pressure than what you have now will.

That is how it is in my imagination or understanding, anyway.

 

[Ol` Joe]

You have a lighter load with 4.2gr of Universal. If you were working with a max charge you may have troubles, but I doubt you have enough of a change in length to make the load a problem.
VithaVourie in their manuals has a small paragraph on OAL and small cartridges such as the 9mm. The seating depth definitely makes a difference but some lee way IMO is necessary to fit the load to the gun as you have found out. I would stay away from a max load at that shorter OAL but wouldn`t fret too much and a long as things look OK I keep shooting what you`ve got and maybe even raise it a hair if I got the urge.

 

[918v]

If 4.5grs of Universal is max under a 115gr LRN @ 1.100" OAL per hodgdon, then 4.2grs @ 1.080" is max. If I were you, I'd reduce the load to 3.8grs and load five at 3.8, 4.0 and 4.2grs to test.

 

[Foto Joe]

I agree with 918v in that it wouldn't hurt to load up some tests and go run them through. I'd also like to chronograph those rounds just because. Also, where did you derive the 1.080" max/min foro 4.2gr?

I'm still confused though regarding the "C.O.L." listed on the Hodgdon data. They give NO explanation as to whether it is min or max.

 

[918v]

where did you derive the 1.080" max/min foro 4.2gr?

From my experience with OAL reduction in the 9mm and Universal Clays powder.

You also have to consider that most 9mm chambers accept 115gr RN's at an OAL much longer than 1.100". I'd venture to say that Hodgdon's test barrel has alot more freebore than your gun. Hodgdon's load at 1.100" OAL will produce less pressure in their test barrel than it would in your gun.

 

[Foto Joe]

Hodgdon's load at 1.100" OAL will produce less pressure in their test barrel than it would in your gun.

That's one of the reasons I'm a little spooky about the short loads.

One of the things that's got me scratching my head is that this gun even though rarely fired in the last thirty years, runs like a clock with factory ammo. Factory ammunition that I would assume has a length somewhere around what the reloading data says.

I've never measured a factory round since I don't have any, but maybe I'll take my caliper to the gunshop and see what they are. On the other hand, my caliper may be challenged for all I know.

 

[918v]

Don't be spooked, just work-up the load. Load-up small batches so you don't have to pull alot of bullets. So what if your starting loads fail to cycle? Better safe than sorry.

 

[TheCracker]

I find this odd. I have a 92f and a sr9c. Both will take my 115 lrn( MBC) loaded at 1.120 with no problems. (using 4.4 g of universal btw) The Winchester white box 115fmj's come at 1.165 if I remember right. Yesterday I loaded some 115g fmj's at 1.160 and they fall in both chambers and fall out with no problems.

My point is that I have 2 9mm's by different manufacturers and they will take longer oal's. I know I'm not using the same exact bullets as the OP but I wonder if his chamber is out of spec?

 

[Foto Joe]

I'm on my way to town and I'll take some of my reloads and probably the barrel and my caliper too. We'll figure this out one way or the other.

 

[RidgwayCO]

To answer your question about Hodgdon's COL listing, I've always assumed that the number listed was the COL that Hodgdon's technicians used in testing that bullet. So it's neither a minimum nor a maximum, just what they used.

I have to go to my reloading manuals to determine the SAAMI maximum length for a particular cartridge, and I've never seen a "minimum cartridge length" listed. Since some rounds are loaded with the bullet flush with the case mouth (.38 Special wadcutters come to mind), I've come to believe that the length of the case is the "minimum cartridge length."

With auto pistols it's always necessary to ensure that your rounds will feed correctly, as rounds that are too short or too long may not feed correctly. Also, rounds that are too long may not fit in the magazine.

That's the fun of reloading for auto pistols. Finding that "just right" load that combines the COL that functions 100% in your guns (and they vary tremendously), provides the performance you want/need, and all within SAAMI pressure limits. I've found QuickLOAD to be an invaluable aid in working (and staying) within these parameters.

 

[ranger335v]

"To answer your question about Hodgdon's COL listing, I've always assumed that the number listed was the COL that Hodgdon's technicians used in testing that bullet. So it's neither a minimum nor a maximum, just what they used."

Exactly so. This isn't a cut-and-dried activity that we MUST follow a manual 1-2-3 or things blow up. Adjust any OAL to where you need it and develop your load. I've been doing this for decades,rifles, revolvers and pistols, haven't even looked at a book OAL.

 

[Foto Joe]

Ridgeway & Ranger,

I took a couple of rounds and the barrel into town and talked to a VERY experienced reloader at the shop. He assured me of exactly what you stated above, probably at about the same time.

Lyman does have a minimum OAL listed as 1.065" for a particular bullet configuration but not the one I use. So...I'll go shoot up some of these thing this morning and see if I can make any improvements on my poor shooting skills with a semi-auto.

Thanks for the help.

 

[gamestalker]

It is indeed my understanding that finding the maximum operating OAL for your firearm. This is necessary to avoid extreme pressures that can present if OAL is less than necessary with the 9mm, and other simular cases.