Recoil spring guide rod question

[unspellable]

I have a Ruger P89 chambered in 7.65 mm Parabellum, AKA 30 Luger. I also have a Browning High Power in 7.65. Now I wouild expect the recoil spring to be a bit different than for the 9 mm version. The mystery is that in both cases the guide rod is different and I am baffled as to why it should be different. Any ideas?

BTY: the High Power seems to function fine with a 9 mm spring and guide rod.

 

[JTQ]

You're confused why the P89 and the Hi-Power have different recoil springs and guide rods than each other, or you're confused why the 30 Luger P89 and Hi-Power have different guide rods and recoil springs than the 9mm versions of the P89 and Hi-Power?

 

[unspellable]

The question is why, for both pistols, the 7.65 guide rod is different than the 9 mm guide rod.
A difference in the springs is expected as the 7.65 mm produces less recoil impulse than the 9 mm.
Would not expect the Ruger guide rods to look like the Browning guide rods and they don't. In the Browning the take down pin goes through an eye at the rear of the guide rod, not so on the Ruger.

 

[bersaguy]

Guess it depends on what they look like exactly. A photo would help, but on speculation, I'll take a stab at it. A spring with fewer turns, or smaller diameter, or thinner wire (ie, weaker for less recoil) would be more prone to kinking, and therefore require a guide rod that was maybe longer or shaped differently to accommodate the properties of that particular spring

 

[unspellable]

I'll try to get some pictures and measurements on here in the morning. I have both guide rods for the High Power, but only the 9 mm spring. With the 7.65 barrel and the 9 mm spring and rod it ran 20 rounds with no hickups. 10 rounds were Winchesters which are underloaded. (Winchester claims they are standard velocity loads, but the chrony says otherwise.)

 

[unspellable]

Ruger P89 springs and guide rods. 7.65 mm on the left, the spring is captive. 9 mm on the right, spring is free. Note the wasp waist on the 9 mm rod about 1/4 of the way down.



High Power guide rods, 7.65 mm on the left, 9 mm center. The sproing is for 9 mm. The thin rod at front of the 7.65 is spring loaded and can be pushed into the main body. The 9mm rod has a spring loaded ball at the front. The pin on the take down lever passes throught the eye at the rear of the rods.

The 9 mm cartridge will produce about 13% more impulse than the 7.65 mm cartridge, not a huge difference. The High Power ran 20 rounds of 7.65 with the 9 mm rod and spring with out a hiccup.