Underwood 10mm 180gr TMJ



I found the C.O.L. to be 1.245”

Taking a look inside I found 9.6gr of propellant that looks very much like 800-X.



A closer look;



The bullet weighed in at 179.4. This looks just like a Speer 180gr TMJ.



At the range I shot two groups this time. One, with the stock spring, and the other with an ISMI 22# spring and SS guide.
Gun is a brand new Glock 20-SF with stock (4.6") barrel.



First, I was surprised to see such a significant velocity spread in both groups. I had velocities as low as 1155fps and as high as 1275fps. Now If I was to try to use any kind of powder measure with 800-X, I know what would happen.. Large weight variations.. So I wonder if that is happening here. I am tempted to pull down some more rounds and see what variations there might be.
Well the ISMI spring seemed to help with accuracy a bit, and the brass stayed closer and easier to find.

Second, this ammo is warm. Many of the fired cases produced smileys..



The cases that did not have smileys measured;
.4340, .4392, .4348, .4343, .4341.. These must have been the rounds that shot in the 1100’s.

All in all, the ammo shot very well and functioned flawlessly through the Glock 20-SF. I’ll keep a magazine full of these for woods carry. I just won’t bother looking for brass..