*** Additional Warning *** +P+ ammunition is loaded to much higher pressures than standard ammunition. Use this ammo sparingly, and only in firearms that the firearm manufacturer specifically states are safe for use with +P+ ammunition.
I really don't know much about Underwood Ammo other than it seems to be the posted about frequently around the internet forums and has gained a very good reputation with folks. It's made in the US and the 10mm fans can't seem to get enough of Underwood Ammo. When I was searching around I found that tnoutdoors9 had been testing some of the Underwood Ammo and doing some excellent videos. Unfortunately, I found nothing about the performance of this 9mm load from a shorter barrel length.
Pistol Specs:Boberg XR9-S with 3.35" barrel
My testing process is pretty simple. I take one shot at the end of a Clear Ballistics Gel block. I take the shot from 8 feet away and impact velocity is measured 2 inches away from the block. Clear Ballistics Gel is calibrated to 10% ballistics gel density. I shoot the block at the range and then bring it home to analyze the block and recover the bullets. Immediately prior to the terminal test, I shoot a five shot velocity and point of impact test string from 8 feet over a Competition Electronics ProChrono Digital chronograph.
As my experience with the Clear Ballistics Gel product increases, I'm starting to better understand how to read the blocks and capture more of the data that is visible in the blocks. You may have noticed I added two new data points to the test recap data sheet. Those points are a measurement of the maximum stretch cavity height and also the penetration depth when the maximum stretch cavity was measured. These new data points may provide additional comparison points between various bullet types and loadings as we collect more of this data over time. The video below documents my entire test from range testing to bullet recovery.
Since we used a short 3.35" barrel in this test, it was unreasonable to expect 1400 fps velocity. I was pleased that we lost less than 100 fps from the manufacturer published velocity specification.
The high speed video for this test turned out well so I had to grab a still frame showing the "dynamic entry" into the block.
Disclaimer....This test should not be considered an endorsement or recommendation for the product(s) tested. All tests represent actual performance in ballistics testing media. Terminal performance in all other media will show different results. It is up to each individual to make their own personal decision on which specific ammunition to use for their needs. It's also critically important to test any ammo in YOUR SPECIFIC FIREARM before relying on it for any purpose.
Ammunition labeled as +P or +P+ should only be used in firearms that have been certified by the manufacturer as safe for the additional pressures generated by these ammunition types.