Is it alright to expose the lube groove?

[WayneConrad]

Here's another question brought up by my quest to load L-FP 122 for 9mm Luger.

The Lyman load for L-FP 121 iis 3.7-4.4 gr of Unique, OAL 1.110". But with my bullets, that OAL causes the lube groove to be partially exposed, with the case mouth sitting on wax instead of lead.

I will need to seat about 0.075" deeper, for an OAL of 1.035", to reliably get the lube groove entirely within the case.

It it alright to expose the lube groove? My gut says no, because the lube can get knocked off in handling, loading, or chambering the round, and because I don't know what hot gasses in the chamber will do to the lube before the round is thrust into the barrel, and because I will wonder if the case can hold the bullet securely with the case mouth on wax. I think I should seat it enough to cover the lube groove, but be very cautious of the increased pressure I'll cause. Is that the correct approach here?

 

[ReloaderFred]

WayneConrad,

You'll want to seat the bullet until the lube is covered by the case mouth. This will help to stabilize the bullet in the case and to keep it from setting back from recoil. With the lube outside the case mouth, it has a tendency to pick up all kinds of debris, none of which is good for the bore and rifling of your barrel. Dirt that is stuck to the lube is like very fast sandpaper when the bullet travels down the barrel.

Hope this helps.

Fred

 

[WayneConrad]

Fred, it definately does help, thanks. I hadn't considered dirt.

 

[Brian Williams]

and because I don't know what hot gasses in the chamber will do to the lube before the round is thrust into the barrel,

Those hot gasses are in the cartridge case behind the bullet both of which are in the chamber. The chamber holds the cartridge, the cartridge holds the initial gasses, untill the bullet is started down the barrel. There are no real gasses in the actual chamber because the case serves to be a gas seal, some times with low pressure loads the case does not expand enough to seal and some gas slips between the case and the chamber wall, this is where you see black fouling on the outside of the case after firing.

The lube is probably only touched by hot gas due to a little blow by while the bullet is in the throat, and then only a little bit.

 

[Brian Williams]

OBTW seat the bullet past the lube groove to prevent wobble and setback.

IHTH

 

[fecmech]

Wayne--The Lyman bullet is .625 oal and has a bearing surface of about .280 that goes in the case. I load the lee bullet which is only .563 oal with approx .280 bearing surface. So when I load at 1.048 oal with the lee I have approx the same amount of space left in the case as the Lyman at 1.110 and the same bullet weight. I don't have acces to a pressure gun but I'd bet that pressure is pretty darn close to Lymans figures. If case capacity, bearing surface and bullet weight are the same I don't see how pressure can be much different. My $.02 Nick

 

[ReloaderFred]

Brian,

Every planet has it's STOBOR, if I remember the book correctly from my school days, which was many, many years ago.

Your description of the chamber gasses is correct. The case seals the chamber and the base of the bullet seals the bore. The bullet lube is washed off on to the walls of the bore by the friction and the compression of the base of the bullet, which squeezes out the lube enough to coat the bore. The lube works for the base of the bullet being fired and the portion of the next bullet that is ahead of the lube groove.

When I'm sizing hard bullets of linotype in one of my Star sizers, I run a lubed bullet through the die about every fifth bullet, which relubes the die and makes it easier to size the next few bullets. This is the same principal as the lube in the bore of the gun.

Hope this helps.

Fred

 

[Jim Watson]

Apples and kumquats.
The typical commercial 122 grain bulk cast bullet is not out of a Lyman mold and seating depth/OAL numbers for Lyman no 356402 do not apply.

Seat the bullet to where your gun tells you to. Make up a dummy round, sized brass, no primer, no powder, and seat a bullet to just cover the lube groove. Drop it in your chamber - barrel clean and out of the gun - and see if it goes in all the way and would allow the slide to close and lock. If not, seat a little deeper as required by your gun's chamber. Then load some to that OAL with your starting powder charge and shoot for function. Increase as required to get full slide travel. Tinker with OAL if necessary for feeding.

 

[Sharps Shooter]

Or horses and dogs.
I've collected about six Lyman manuals over the years. I checked 4 of them this morning and they all show 4.3 to 5.3 grains of Unique for the Lyman 356402 bullet in the 9mm Luger. I don't see the load data showing only 3.7 to 4.4 grains of Unique. I do see that my Lyman manuals show 1.110" OAL for the 9mm Luger when using the Lyman 356402 bullet, but as Jim Watson wrote, that's probably not the mold those bullets came from.
But to answer your question - no, it's generally not okay to leave the lube groove(s) exposed. The lube will collect dirt. Besides, there's a pretty good chance when you chamber the cartridges, the bullets will be forced further into the cases anyway - if they'll chamber at all. That said, occasionally you'll see a rifle shooter who has left one or two lube grooves exposed. Particularly in black powder cartridge rifle competition. But those are special circumstances where the cartridges are kept in closed boxes and not exposed to dust or having the lube knocked off until the moment they're drawn from the box and shoved in the chamber of the gun.

 

[Jim Watson]

Yeah, I do that. One or two grooves of SPG exposed in my BPCR ammo, but that is a specialty load.

 

[BluesBear]

Jim nailed it.

You need to load the bullet so it's ogive is the same as for ball ammo.
OAL will be different for every bullet style.
I advise people whan loading handgun ammo to forget about OAL entirely.

Load ammo that FUNCTIONS.

Worry only about maximum length. AFter all if is won't fit into the magazine or cylinder if won't work.

Just beware that as a bullet base is seated deeper into the case pressures WILL rise.