DW RZ-10 and Underwood Ammo

arentol · #1 03-03-2012, 05:39 PM

I have had a DW RZ-10 for a while now (since 2009). It has handled every bit of ammo I have thrown at a it without even a hint of complaint... Until today.

I recently got my hands on some 135gr, 165gr, and 180gr Underwood Ammo which is rated at 1600, 1400, and 1300fps respectively, and which, unlike Double-Tap which has similar ratings, actually achieves those high numbers.

Anyway, I took the above ammo to the range today and ran a magazine of each through my RZ-10. The 135 and 165's resulted in two FTE's per magazine, but the 180 ran perfectly for 2 magazines straight. One of the FTE's on the 165 even resulted in the round behind it getting shoved into the unejected case so hard the bullet got pushed back about 2mm into its case.

I want to use Underwood as my main carry ammo, and while I am fine with using just the 180, I would prefer to carry the 165 if I could get that to run reliably.

I assume that the main issue is that the springs aren't right for loads this heavy. Does anyone know what springs I should be changing to fix an issue like this, and what kind of change I should be making to them (heavier, lighter)?

Sheepdog · #2 03-03-2012, 09:42 PM

I would check the extractor tension. The the springs seem to be doing their job. Just my thought.

JBT · #3 03-03-2012, 09:47 PM

Does this model have a ramped barrel? Not saying that is the cause, I just know Underwood doesn't recommend shooting the 165gr in a 1911 style pistol with a without a ramp barrel.

arentol · #4 03-04-2012, 12:38 PM

The RZ-10 does have a ramped barrel, but I am still not ruling out case bulge as partial or full cause of the problem. I have pretty what appears to be the same problem with this ammo in my new (used) Fusion 10mm Commander that does not have a ramped barrel. However, the Fusion also has this issue with Double Tap ammo as well, which the RZ-10 does not.

Since I already have one on hand I am going to try a 3lb heavier (27 instead of 24) recoil spring in the Fusion and see if that solves the issue with Double Tap ammo. I don't expect the Underwood to work in that gun anyway so if it doesn't help with the Underwood I won't really mind. If it does help with Double Tap then I will probably order 2lb heavier spring for the RZ-10 to see if that solves the problem.

Does that sound sensible?