Cape gun back from gunsmith so I fit the scope to it today!

[cotis]

I posted a little while back about the cape gun I picked up a few months ago and dropped off at a local gunsmith for some work. Well I picked it up yesterday. He did a great job of fixing the forearm which was in really rough shape. The stock refinish looks good, really evened out the color.

So today I decided to mount the scope that I fixed up. I measured both sets of mounts that I had along with the rifle bases with calipers. Finally caught a decent break where I could use the front AKAH mount that already fit the existing scope holes along with the rear mount from the other set. I used Mike's advice which worked perfectly for measuring and fitting the rear mount. He was correct in that the bases were parallel to the water table but not each other. Front base was below the rear by ~1.8mm. It took me just over 4 hours but I am really happy with the result! I had to take around 0.020" from the inside claws of both mounts. This is a line-to-line fit with the gun bases, so this controls the side-to-side tightness of the bases. For the rear mount I pulled the slider from rear base and used a jeweler's file to cut the notches deeper in the rear mount. Once I was close I profiled the bottom of the slider to produce a tapered lock-up to pull the rear mount down. It is bank-vault tight! Bore sighting it at 100 meters I ended up only 4 clicks from middle on the scope windage, 12 clicks from middle on elevation! I could even remove the 4 click offset in windage since the rear mount is adjustable.

I need to repaint the scope rail as all the fitting on and off of the rear mount scratched off some paint from my previous respray. The front mount is tight but not bank-vault tight so I may get some shim stock and fix that. The 25-35 Win produces 7 ft-lbs of recoil so I am not too worried about it. The plan is to get to the range in the next few weeks and test the zero repeat-ability.

[mike ford]

cotis,
Great, shooting it will tell the tale. Good luck.
Mike

[cotis]

So I shot the rifle yesterday with both factory Sellier and Bellot 117gr ammo and some reloads using Winchester brass, CFE 223 powder, and Hornady 110gr FTX bullet. The factory S&B ammo was right at 2000fps average, the reloads were 2150 to 2300 fps (26gr to 27.5 gr in 0.5 gr increments). My reloads were more accurate than the S&B stuff. For each batch of my reloads, I fired two shots, removed the scope and replaced, fired 1 shot, removed and replaced then fired final 2 shots. Range was 100 yards. I averaged around a 3" group for the 5 shot groups. I could feel the slightest of play in the front scope mount at the base, I have already ordered some shim stock and other materials to correct this. Photos of two of the groups (in the 27.5gr photo two bullets went through same upper hole):

[mike ford]

cotis,
Normally, a good drilling would shoot better than that( barrel bundles are very stiff), maybe the shims will help. If you are careful about the shot, you could hunt with it, like it is.
Mike

[Diz]

My loading program lists both of these cartridges but gives widely differing Pmax for each. This surprises me since they are both also Piezo CIP pressure rated. The 6.5x52R shows up as 35534 psi Pmax while the 25-35 is given 44236 psi for a Pmax. I am at a loss to explain this except perhaps action types for both cartridges are taken into consideration.

I also ran your load data and plugged in a 24" barrel as I could not find a reference to length. Using 26.0 grains of CFE-223 the 6.5x52R gave a pressure of 30398 psi and velocity of 2397 fps. Pretty well within the pressure limits. The 27.5 grain load was 35636 psi and 2537 fps with the Hornady 110 grain bullet. This is just the slightest bit over max. When these numbers are plugged into the 25-35 with the same bullet and barrel length the 26.0 grain load showed 28312 psi and 2358 fps. The 27.5 grain load was 31978 psi and 2495 fps. There are some interesting differences showing up in the calculated data. I thought this would be an interesting exercise for the program and myself but someone with more information may want to clarify the difference in the Pmax pressures for two cartridges that are supposed to be the same. I would also be interested to know the source of your load data.

Thanks, Diz

[cotis]

Diz,
Someone I met through another forum provided me with 75 pages of magazine articles (new and old), old reloading manual charts (some going back 50 years), and some new information on the current loadings of 25-35 using CFE-223. That article used 117 grain bullets with a starting charge of 25 grains and a max of 28.5. The 110gr FTX has a smaller bearing surface than the 117gr RN, so did my work-up using the middle range of that recipe. I am going to stick with either 26 or 26.5 grains, no more. I do not want to push this old gun and stress the stock excessively.

Thanks for running the load data, that really helps!
chaz

[Diz]

I really like finding old load data myself. I think it very interesting to know how they were doing things back then. I admit being surprised at data for CFE-223 as it is a fairly new powder for the market. I think you are in fine shape with that load and smart for not trying to push it. If you would like me to run something else for you just PM and I'll be happy to try and help.

Diz

[cotis]

[Diz]

I am glad you posted that and again a little surprised that the pressure is listed in copper units of pressure and not psi. Based on the maximums in the data I have to assume that the 44,236 psi Pmax is correct for the 25-35 as cup is almost always lower than psi. I have been playing with a conversion factor that everyone seems to think is not possible but it worked out pretty well with this data as it came out to 44,020 psi converted. Very interesting indeed and thanks again. Diz

[Axel E]

My loading program lists both of these cartridges but gives widely differing Pmax for each. This surprises me since they are both also Piezo CIP pressure rated. The 6.5x52R shows up as 35534 psi Pmax while the 25-35 is given 44236 psi for a Pmax. I am at a loss to explain this except perhaps action types for both cartridges are taken into consideration.

The explanation is buried deep in history. The .25-35 became popular in Germany even before WW1. Nothing was standardized then, neither in Germany nor in the USA. In 1920 the metric name "6,5x52 R" was given.
In 1925 the 6.5x52R was normalized in Germany with metric case and chamber dimensions. Inevitably these differ very slightly from the American dimensions in inches, as the numbers were taken with German measuring and manufacturing habits and rounded to .01 mm. These slight differences cause some German 6.5x52R minimum chambers don't quite accepting American .25-35 factory loads. A handloader's solution: Grind about .5 mm = .02" off the bottom of your .25-35 fl sizing die.
A year later, 1926, the American SAAMI was founded. This started standardisation in the USA, completely independent from European normalisation. Dimensions and pressures from then on were taken with different systems and protocols. During the interwar years there was practically no ammunition import/export USA – Germany. So Germans depended on German, RWS or DWM loads exclusively. BTW, the CIP, a convention of European proofhouses,was founded in 1914, just a few days before WW1.
AFAIK the original .25-35 Winchester load was a 117 gr bullet at 1978 fps. Later this was stepped up to 2230 fps. RWS offered two loads, both with a 117 gr copper jacketed bullet, at 2000 and 2224 fps respectively. Apparently they copied the ballistics of the American "original" and "high speed" loads in the interest of sighting, but with German powders. Up to the 1930s the better German powders achieved the same ballistics with less pressure than their American and Austrian counterparts.
Until 1939 a gunmker had to specify the factory load a rifle was to be proofed for. The German 1939 proof law then prescribed maximum allowable rifle cartridge pressures for the first time. Contrary to popular belief these "Max" pressures were not determined by destruction tests of various rifles. Instead, the pressure of the highest intensity RWS or DWM then factory load was prescribed as "max" for the future. All rifles from now on were to be proofed for the new maximum pressure. These max pressures were subsequently taken over into european CIP rules. As the German loads then were loaded to the same ballistics, but with lower pressure powders,resulted in apparently low max pressures of some Austrian and British cartridges that were loaded with inferior powders to much higher pressures previous to WW1 originally. To this day European factory loads and published handloading recipes have to cling to these 1940 maximum pressures.
Imports of American ammo only restarted in the late 1950s when changes in the US$ - DMark rates made it affordable in Europe. Now American .25-35 loads were loaded to the higher SAAMI pressures. The CIP could neither ban the import of ".25-35" loads nor could they rise the max pressure of the "6.5x52R" without invalidating the proof of older rifles. So both cartridges are listed now with different max pressures.

[Axel E]

For the respective CIP data see:
.25-35 Win: http://www.cip-bobp.org/homologation...-en-page61.pdf
6,5x52R: http://www.cip-bobp.org/homologation...-en-page14.pdf

[Diz]

Axel, excellent site with all the information you could ask for. There is definitely a difference in the maximum pressure values for the two cartridges and my reference is correct. Thanks, Diz