Repair mark question?

[Cthraen]

I am interested in the repair marks and kaliber stamp on my drilling (same boxlock discussed on this forum. This is what I know. The barrels carry a repair mark from 1933. The shotgun chambers are 65mm, thus not relieved to 70mm, therefore not the C/R. The rifle barrel carries a Kal 8 x 57 JR stamping that appears to be more modern in style, as in 1933 relative to the other mark fonts-styles. The rifle bore is .318. Two photos supplied.

Upon disassembling three 220 SP loads that came with the drilling I found 49g of 3031 powder in each. This would put the load at the top of the pressure/velocity chart and be consistent with the post 1905 .323 8mmx57 round for velocity and psi.
Now my query.
Is it possible/likely that the C/R marks indicate the rifle was reproofed to the 8mmx57 JS ballistics in 1933? The prior owner acquired the drilling while in Germany and the drilling did see action in Roebuck hunting. The loaded rounds would have been used in the drilling.

[mike ford]

Cthraen,
Was the ammo that came with the drilling marked as being loaded with 3031 powder or did the person that loaded it identify powder? If not, identifying it "by eye" is not reliable enough to know what the powder is. The best advice is just to start over and derive your own load, using a reliable loading manual(s) and chronograph. You mentioned the rifle has .318" groove diameter, then mentioned .323" ammo; did you measure the bullets pulled from the ammo that came with the rifle? If you did and it measured .323", the larger bullets might still be useable. If a bullet freely enters the neck of a case fired in a rifle and not resized, that bullet can be used to load for that rifle using the same cases. It is generally accepted that excess pressure is generated if the case does not have enough room to expand to release the bullet, rather than the bullet being a little larger than the barrel. I could not enlarge the small photo, so I couldn't read the proof load, but generally if a rifle was reproofed, the old load would be crossed out and the new load would be marked. FWIW, if H4895 powder was mistaken for 3031 in the ammo you have, the pressure would likely be lower since the 4895 burns a little slower. I like to use 4895 because it's burn rate seems to be close to R5 powder used in some old German ammo.
Mike

[Cthraen]

Mike, thanks for the reply.
I slugged the barrel and the lands measure +0.320. Supplied with the drilling is a swaging/reducing die to take a +0.323 bullet down to +0.318, plus boxes of Sierra, Speer and Hornady bullets in weights from 125g, 150g, 170g, 200g and 220g. All swaged/reduced to +0.318. Also supplied is a full set of +0.318 JR dies. I have created 5 fired-form cases and the neck ID measures +0.320.

On the already completed cases supplied the 220g bullets were swaged/reduced to +0.318. When weighed the powder charge was right at 49g. This is a maximum high psi load regardless, but I cannot say it was 3031 or 4198 so I will leave it at that.

I am loading new rounds considerably lighter using gas checked cast bullet load data. One 170g jrn at 28g IMR 4198 which is a PSI listed at 29,000. The other is a 139g bullet using IMR 3031 at 38g and PSI of 32,000.

Now to the Crown/R repair issue. There is nothing to suggest that the drilling was repaired in any discernable manner. The only oddity, if that is what it is, would be the KAL 12 - 8 x 57 JR. stamping on the side of the rifle barrel. This mark is over the original Krupp rifle steel engraving. I will provide clearer photos of this.

Your thoughts?
Photos Rifle Marks:

[Axel E]

The German factory 8x57 I and S cartridges were loaded the same pre-WW2, same bullet weight and same powder charge. So there was no need for any reproof.
As I already wrote here https://www.germanguns.com/vb5/forum...n-illustration I believe your drilling got a second, new set of barrels in 1933, maybe for the more up to date 8x57 IR instead of an old fashioned (by the 1930s) 9.3x72R one. As the action was unaltered, just the interchangeable new barrels got the Repair proofmark.
BTW, these 1933 barrels were bored and rifled by the well known Suhl barrelmaker Wilhelm Kelber.

[mike ford]

Cthraen,
The marking 7.8 over 57 represents measurements by the proof house, using gauge pins in 0.1 mm increments. Therefore, it means the bore (not groove or bullet) diameter was found by inserting a 7.8mm pin into bore, then trying a 7.9mm pin which would not enter. These measurements will not convert to either .318, .320, or .323" because they represent groove or bullet diameter instead of bore diameter. Measurement of the bore with the gauge pins is quick, therefore economical, while measurement of the groove diameter (which would represent a nominal bullet diameter) would require very sophisticated equipment to measure the actual grooves or "slugging" the barrel and measuring the "slug" as a representation of the grooves. This would be simply too expensive and time consuming and not necessary to ensure the barrel conforms to the requirements. To avoid the confusion of thinking the measurements stamped on the barrel are of the nominal cartridge, some makers or gunsmiths also marked the guns as to the common name of the cartridge they used. Indeed, under the 1939 proof law this became a requirement under the law for new guns. Accordingly, the KAL.12--8X57JR over stamped onto your barrels are the nominal cartridges the gun uses, whereas the 12 in a circle and the 7.8 and 57 represent measurements taken during inspection. While there is no way to determine now, it may have been reproofed under the 1939 law to acquire the new marks or it may have been marked simply to avoid confusion and the crown R represents reproof for some unknown repair work.
In handloading for the drilling, you should be able to use .318", .320", or possibly .323" (depending on whether it will enter the neck of a fired case) jacketed bullet, using powder commonly used with jacketed bullets or you should be able to use cast bullets of any of those diameters using powders appropriate for cast bullets. You stated the "lands" measured .320", I'm guessing you mean lands on the slug which would be grooves in the barrel. You mentioned that you couldn't tell if the powder in the ammo you have is 3031 or 4198; 49 grains of 4198 would be an overpressure load for sure. I used 49.5 grains of H 4895 behind a 198 grain Norma bullet in my 8x57JRS for years, having worked the load up "on the target" before I got a chronograph. When I did get a chronograph, I discovered the velocity was higher than for 8x57JRS, and more in line for 8x60RS. I consequently reduced the charge even though it had been used satisfactorily and this is why I recommend using a chronograph when working up a load for a drilling or other "tip up" type gun. If you depend on traditional pressure signs alone for this type of gun, the pressure will be too high before they show up.

I note that Axel has weighed in. If any of his comments differ from mine, you should accept his as authoritative.
Mike

[Cthraen]

Axel and Mike. Thank you for your detailed and knowledgeable replies. I personally knew the prior owners, going two generations back, and the provenence for this fine drilling beginning with its first non-German acquisition back in Germany. However both the first owner and his son have passed on taking that information with them and therefore discovering its history is indeed a pleasurable mystery to be unraveled. Your thoughtful replies have helped immensely in filling in the blanks.

I am using gas check cast bullet load data with jacketed RN and SP bullets because only my Accurate Powder load manual explicitly lists the 1888 .318 cartridge with grains, velocity and psi. Lee, Hornady, Lyman provide loads for the post 1905 8mm Mauser round with pressures above 40,000 psi and into the 50k. Seems prudent to start at this lower psi point.

I think it reasonable to keep my load pressure under the 35,000 psi SAAMI max for the 1888 .318 round. The drilling may be capable of more but it is not needed. There are many good loads for whitetail deer and boar that I can develop. I have an Oehler chronograph and will put it to use. I will continue to provide updates on my progress. I will also develop a slug load for the right barrel with a more open choke (+0.712). I believe the left is far too tight at +0.682 for a solid.

Again, thank you for your help and interest.

[mike ford]

Cthraen,
It is great that you are consulting various loading manuals and are consciously avoiding high pressure loads. Some things you should be aware of, however, can make a difference in the outcome. You say you are using gas check cast bullet data with jacketed RN and SP bullets because the loading manual lists the pressure of the listed loads. You should be aware that the listed pressure will not be accurate if you change the load by substituting jacketed bullets for gas checked cast ones. Jacketed bullets typically generate higher pressures because they are harder to push into the rifling than cast bullets are. Even when comparing manuals with data for jacketed bullets only be aware that different methods of testing result in different results. Older manuals used copper crusher type equipment which yields "Copper units of pressure", usually expressed as PSI in the older manuals but in newer ones it may be listed as CUP or psi cup. When transducers are used the result is expressed as psia. There is no accurate way to convert from one to the other, but transducers usually show a higher number for an acceptable load. Therefore, data with cup should be compared with other data showing cup. Likewise, psia data should be compared with other psia data. This doesn't mean you shouldn't use the date, only that you should do so with care. I previously mentioned that I use H4895 as a replacement for the old German R5(starting with a reduced load and working up, of course) because of similar burning rate. Axel has reported that he used VN 140 powder in a similar way for a similar reason. If I didn't have a stock of Military "pull down" 4895 and had to buy powder, I believe I would look for VN140 in accordance with Axel's extensive experience.
Mike