The Underwood ammo is relatively new, ordered April 2019.  All the other ammo was bought new around 8 months ago.  All rounds were fired from a bone stock G20 Gen3.  All my test results are averages based on 10 shots, 6' from the chronograph.  Energy levels are listed with all velocities.

Underwood 135gr Nolser Item #231
1600/767 Claimed
1426/610 Test Result

Underwood 155gr XTP Item #232
1500/774 Claimed
1479/753 Test Result
NOTE; 1 light smile.

Underwood 165gr Gold Dot Item #237
1400/718 Claimed
1318/636 Test Result
NOTE; 1 very light smile.

Underwood 180gr Gold Dot Item #244
1300/675 Claimed
1245/619 Test Result

Underwood 200gr XTP Item #246
1250/694 Claimed
1184/622 Test Result
NOTE; 1 very light smile.

Underwood 200gr Hi-Tek Coated Hard Cast FN Item #248
1250/694 Claimed
1155/592 Test Result
NOTE; The UW website claimes a 21 BHN.  I doubt that's true since the bullets have a baked on powder coat which takes hardness back out of the originally hard cast bullet.  I dropped an 8 pound hammer on one of the bullets next to another 200gr hard cast bullet rated at a 21 BHN without powder coat and the Underwood powder coated bullet smushed down much more than the non powder coated one.  While I can't guarantee the BHN of either bullet, the results as the very least leave me wondering.

Winchester Silvertip 175gr
1290/647 Claimed
1167/529 Test Result

SIG SAUER 180gr FMJ
1250/624 Claimed
1127/508 Test Result

Fiocchi 180gr FMJ
1250/624 Claimed
1098/482 Test Result

Blazer Aluminum 200gr FMJ
1050/490 Claimed
988/433 Test Result

American Eagle 180 FMJ
1030/424 Claimed
1004/403 Test Result

About the UW loads - the 155gr load was pretty sweet!, but I had hoped for a bit more from the others even with the understanding a Glock with a stock barrel is a worst case scenario for top velocities. My 4.6" Lone Wolf barrel in the same gun is usually good for an additional 25 fps or so, but that alone wouldn't have reached the advertised velocity, and I don't think another 0.4" of barrel would either.  All that said, I'm still happy overall to have UW 10mm ammo available, but is sure doesn't achieve what it used to back in the beginning!

No doubt UW is pushing them to the max with the current powder they are using based on the light smiles I was seeing. But it does seem their advertised velocities are a tad overstated.  At least they aren't absurdly off base like Double Tap's 10mm ammo.

I'm really tempted to get some current Buffalo Bore 10mm loads and see how their results compare, but dang it's expensive!

That's about right for most of these loads on a g20...
I know Underwood tests in a longer 5" 1911.
1911 also has more consistent dwell time. 

Odd that they're all low across the board and you got smiles. I still have some of the Underwood 155gr NFP rounds. Those will turn your wrists up!

Thank you Redline.  Good info!

Good stuff..  I haven't shot all of those out of my G20, but the ones I have, you got almost exactly what I got.

Thanknyou for all the work! 

CW

Thanks REDLINE, for your results as posted! 

Redline great results, thank you for your efforts I know this is not easy and takes a lot of work. We appreciate it.

Quote from: mr.revolverguy on July 22 2019 03:25:11 AM MDT
Redline great results, thank you for your efforts I know this is not easy and takes a lot of work. We appreciate it.

At least it's fun hard work! I always wish I could do more 10mm testing, with more different guns and more different ammo...but I am glad I've been able to do what I have, and others doing the same so we can compare results and see what's really what.

Thanks Redline!