7.65 parabellum

[unspellable]

Hi guys, I'm a newbie!


Question: What is the REAL groove diameter of the 7.65 Parabellum barrel? I am fast coming to the conclusion that the 0.308 and 0.309 inch stories I keep hearing are myths that have been repeated so many times every one "knows" something that ain't so. I have measured the barrels on four DWM Model 1920's, a WWII era Mauser that had been rebarreled, two Mauser re-intro's and two Ruger P89's. All measured 0.3110 to 0.3115.


Now contrary to rumours, back at the begiining of time DWM kept very tight tolerances on barrel diameter.


So what's the real story here?


After the controversy dies down, the next questuion is what do you feed it? Winchester factory fodder is obviously not going to work. Aside from the question of having enough steam to cycle the action, Winchester (I got this from the horse's mouth.) loads a bullet with a nominal diamter of 0.309 plus 0.000, minus 0.003. This is obviously not conducive to accuracy.


unspellable

[Kyrie]

Hi unspellable,


Bullet diameter of the 7.65 Parabellum really is .309, and bullets of .308 diameter do provide nice accuracy in a nice condition bore. And yes, true bore diameter of Lugers will vary with wear and tear :-(


That said, try the .309 bullet diameter ammunition in your Luger. Itâ??s sometimes surprising just how accurate a .309 bullet can be when fired through a .311 groove diameter bore.


Regarding ammunition, Iâ??d suggest the Finish military surplus being offered by SAMCO (http://www.samcoglobal.com). Iâ??ve found the Winchester .30 Luger to be too hot for my taste - it sounds, looks, and feels like 7,63 Mauser going off!


Best regards,


Kyrie

[Thor]

I agree with Kyrie, the winchester loading is too hot. The Sako/Lapua sounds like the best bet. I have had good luck with the Hornady .308 diameter bullet though I seem to remember most of the diameters I have sluged were miking .310". The one thing that is important for reloads to know is that both sets of reloading dies I bought, one the RCBS die and a LEE set did NOT have the correct diameter expander plug for the .308" bullets which resulted in them being pushed back into the cartridge case during the loading sequence. I contacted both manufacturers and RCBS basically ignored me but the LEE company sent me a correct diameter expanding plug for FREE! Now I reload with no problems. I have an box of FIOCCHI that I use for shooting the first trials to test the action as it is underpowered and I dont want to hammer the action. Then I can adjust my handloads to work for that particular gun. What a neat fun caliber and accurate! Thor

[Lonnie Zimmerman]

Why don"t you slug your barrel and you will know the true size and know what to shoot in it? Very easy to do.


Lonnie

[Thor]

I have slugged it Lonnie, that is how I got the .310" measurement. Thor

[unspellable]

I have been measuring barrels! Not worn out barrels either. I'll go into a little more detail!


1: DWM Model 1920, condition as unfired, perfect

2: DWM Model 1920, condition very sharp, shiny and crispy

3: DWM Model 1920, poor, looks like somebody put it away with corrosive primer gunk in it as it is not all that worn.

4: DWM Model 1920, condition pretty good, shows some use

5: Mauser 1942, rebarreled, condition sharp, shiny, and crispy (Who rebarreled it? I'm wondering if it's a french occupation item.)

6: Mauser Interarms, unfired

7: mauser Interarms, unfired

8: Ruger P89, near new, 100 rounds through it

9: Ruger P89, unknown usage, but in good condition


Not one of these barrels measured less than 0.3110 inch. The largest went 0.3115. This is why I am questioning the use of 0.308 and 0.309 bullets. I do have a bunch of hard balls from a gun show that were sold as being for the 30 Luger and they measure 0.3110 but they are loose in a bread baggie and I don't know who made them.


The near new Ruger is mine. With Peters ammo the ejection was not at all enthusiastic but it was reliable. With Winchester ammo I had malfunctions. All this with the soft recoil spring. With Feochi it would jam the nose of the first cartridge against the feedramp when you released the slide. After that it would function. Did this with two new magazines. The ramp seems pretty smooth. The Fiochi does have a different ogive curve than the Winchester.


Meanwhile I'm doing the standard trick of switching magazines in the Lugers. That seems to be helping some.


What sort of primers in the Finnish stuff? Corrosive? Berdan?


Years ago I shot semi-wadcutters and wadcutters in my 30 Luger. I'd like to do that again and try some serious target shooting.


One odd observation: Never saw a jackrabbit run after I hit it with a 30 Luger hardball. I've seen them run after getting hit with a 455 Webley, 38 Special, 357 Magnum, 30-06, etc., wtc. Go figure.


unspellable

[Lonnie Zimmerman]

Unspellable; wouldn"t 32 ACP bullets work with the 30 Luger? They are .312.


Lonnie

unspellable ;

I would give some heavy thought to firing anything that measured even .001" greater than the groove diameter.

Remember that the bullet is being swaged by the rifling and any oversize will just increase chamber pressures more.

And this higher pressure will not necessarly result in more recoil or velocity, being somewhat absorbed by the internal friction of deformation of the slug.

I would say no to any thing larger than the rifling bore size by more than .0003"

IMO, For what its worth.

ViggoG

[Lonnie Zimmerman]

This is a little off the subject, but why do rifle bullets have a pressure ring of up to 1/2 thounsanths, and pistol bullets have no pressure ring?


Lonnie

[Thor]

Viggo, I agree with you! After you slug your own barrel like I did, I would NOT hesistate to shoot a bullet .001" over but ONLY if it was a CAST LEAD BULLET, companies like LYMAN RECOMMEND it but I WOULD NOT do it in a Jacket bullet. Hugh has had good luck RESIZING jacketed bullets with a lead bullet sizer die as long as you dont go more than .001" at a time. One day I will buy a bunch of .310" hard cast lead bullets and try them, I bet they shot REALLY GOOD. I have a bunch of .310" light HPs that Hugh resized for me from .312" bullets and he says they are great snail rat(armadildos) killers Thor

[Thor]

The Remington Golden Saber has an interesting dual diameter design with a larger diameter ring at the rear of the bullet, it is said to enhance accuracy and obviously the gas seal. The Driving Bandâ?¢ Makes the Difference.http://www.remington.com/ammo/pistol_revolver/goldnsaber.htm

Thor

[G.T.]

Can you put gas checks on any cast lead bullet? Or do they have to have a relief moulded into them especially for the gas check? Till...later....G.T.

GT,

You guessed right !

There should be a modification to the rear of the slug to accept gas checks, Which are installed while sizeing and lubing.

If I remember these must be forced into the die, base first and a formed punch is used to force them through and shape the nose of the slug .

ViggiG

[Kyrie]

Hi Lonnie,


I'm not quite sure what you mean by "pressure ring" - can up help me understand?


Best regards,


Kyrie

[G.T.]

[Marvin]

Viggo,


You are correct that the mold must have the "ring" on the base of the bullet for the gas check. I would place the gas check on the die, set the bullet on top, and pull the lever. The bullet had the gas check properly seated, lubed and sized in one operation.


Marvin

[unspellable]

Guys! There's been some discussion here, but we really haven't answered the original question. What's the groove diameter of a 7.65 mm Parabellum barrel supposed to be? After measuring 7 or 8 barrels, I've run out of barrels to measure. How about, instead of quoting this or that source, some of you people measure your barrels and report back with the results?


I really suspect this is a case of "Everybody knows what ain't so!" I can quote a few other instances of this effect, but they don't have anything to do with Lugers.


I'd also like to hear what sort of accuracy people are getting with factory ammo and various handloads.


unspellable

[unspellable]

Hello Rick,


I'm really seriously wondering if the correct diameter for the jacketed bullet isn't in the range of 0.311 to 0.312. I don't know where I would get a 32 ACP bullet and they generally run too light any way. I know there are some people using bullets intended for the 32 H&R Mag, these are the standrad 0.312. They say if you run a jacketed bullet through a cast bullet sizing die you can squeeze it down provided you do it in 0.001" steps. (The 32 H&R Mag is an odd one in that it has TWO correct bullet diameters, the 0.312 in revolvers and 0.308 in some single shots. I used to run 0.312 cast bullets intended for the 32 S&W in my first 30 Luger.


I very seriuosly doubt the Winchester load is too hot. Winchester claims 93 gr at 1220 fps from a 4.5" test barrel. I have an orgiinal owner's manual in German for the DWM Model 1920 in which they claim 1223 fps from the 3.9 inch barrel on the actual pistol. This means the Winchester load is slightly lighter than the DWM load.


Incidentally, the correct term for the measure of the load's ability to operate the action is impulse, not recoil. The concern here is obtaining the correct impulse. The action is very strong and there is plenty of margin for pressure. Keep in mind that the old flat spring carbine working load was the same as the proof load for the pistol.


This action will stand up to 32,000 psi from now until the cows come home. Winchester's data for handloading runs around 23,000 psi at 1080 fps.


So any body out there going to measure a barrel and tell us what you come up with?


In about two weeks I hope to be able to run some of the factory loads over the chronograph.


This mess is not a first. I have a rifle chambered for the Purdey 400-360 2-3/4 Nitro Express. Almost anything you can find in print about this cartridge is dead wrong.


Impulse = bullet weight in grains X muzzle velocity + powder charge in grains X muzzle velocity of gas, all divided by 7000 to convert grains to pounds. (Not slugs, that's another story) Since it is pretty difficult to get an actual measurement of the average velocity of the gas it is usually considered to be 2000 fps for a smokeless pistol load.


unspellable

[David Jackson]

I don't do the loading but an expert friend does. He was talking about 1300 fps which I thought would be way to hot; but if your data is correct not so much really.

Your original manual in German; does it really have fps or some sort of metric measurement you have to convert?

If not, sounds like the Winchester is about right; at least to this amatuer.


David Jackson