I finally got to try some Underwood 200gr hard cast and some of their 140gr Xtreme Penetrator (their recommendation for wildlife).

I only did about 20 rounds of each -- alternating both of them with standard 180gr rounds across a few mags.


No issues with tumbling or cycling. They all functioned well.

However, the Underwood had a substantially stronger recoil impulse. And ejected rounds were being thrown considerably further. I can't tell for sure but the action of the slide seemed different as well.

I'm wondering if I should upgrade to a heavier recoil spring. Or should I just keep as-is as lnog it's cycling fine. If this were a 19, the cases are being thrown to a distance where I would consider the spring somewhat worn and would replace.

But I'm not sure if the the 20 is designed for these 200gr rounds or if it's designed more for 180gr and if I use the 200gr, I should plan for a heavier spring.

Any recommendations?

I have and shoot the same but with a Storm Lake ported barrel with no issues.

https://www.storm-lake.com/products/barrel#

Try putting some plain Jane .40 S&W through it, they barely trickle out of the gun. Travel maybe 2 feet

I have using the stock OEM recoil spring in my G20 with Underwood ammo too. But I limit the Underwood to a couple of magazines a year. If was shooting more than that I would go with a heavier spring. And I plan to replace the stock spring more often.
This lets me plink with low power ammo for practice and carry Underwood without a lot spring switching.

If I shoot HOT rounds, (I reload and some are to max load) I go to a 20 lb Wolf spring. Actually, I have replaced the recoil springs in all (4) of my 20s and 29. If you only run a couple of mags every now and then you should not beat the gun up too bad. I really prefer my 10mm served piping HOT!!!!!

Thanks.

Okay, I'll plan to pick up a 20lb spring. I want to practice more with Underwood as it will be my trekking carry round.

I assume that if it's cycling well with 180gr stuff, it'll be fine with 200gr? 180gr is more plentiful and cheaper.

I use the g20 for most of my handgun needs (I have 3 of them). I have those stronger springs but don’t really use them. I don’t shoot much Underwood Ammo out of my guns even though they are my primary woods/bear defense rounds.

I know they work so I don’t really see the need to shoot many of them, the recoil is snappier with them but not enough to make any major difference in the way the gun handles or will handle in a bad situation. Yeah

For practice I almost exclusively use blazer aluminum 200g rounds, in the woods it’s either. If fall bore or underwood 220g.

I think Buffalo Bore was saying that the velocity spread was a bit high (100 fps) with his 220 grain using stock spring so he swapped to heavier spring to get the spread down to around 35 fps. However he did say that the gun functioned fine as stock. You may want to chrono your Underwood and post results.

Since Underwood is not gas checked, do you notice any heavy leading?

quote:

Originally posted by saigonsmuggler:
I think Buffalo Bore was saying that the velocity spread was a bit high (100 fps) with his 220 grain using stock spring so he swapped to heavier spring to get the spread down to around 35 fps. However he did say that the gun functioned fine as stock. You may want to chrono your Underwood and post results.

Since Underwood is not gas checked, do you notice any heavy leading?

If you’re asking me, then no, I do t notice any leading because I use a KKM barrel for my woods gun.