Underwood 220gr Hard Cast Pull-Down

[mt10mm]

I think the 24lbs spring is the fix all for me. I will run some of the new batch 220 today and see for sure.

[Intercooler]

  Which Glock Gen do you have now and what barrel will you be running? I for sure would run the 24lb spring setup! These are top tier loaded and need all the help from the spring you can get.

[mt10mm]

  Which Glock Gen do you have now and what barrel will you be running? I for sure would run the 24lb spring setup! These are top tier loaded and need all the help from the spring you can get.

I have the SF and was running a 22lb spring and was still having slight issues with the 220. Went out yesterday with the 24lb spring but didn't bring the 220! I had no issues with UW 200TMJ,DT 200HC or Prvi 180 so I think the 24lb spring fixed my issues.

[Intercooler]

 That's good news!

[mt10mm]

That's good news!

You had it pegged the whole time saying the 24lb spring!

[Intercooler]

<----- Glock recoil spring 

[The_Shadow]

<----- Glock recoil spring 

That's funny stuff right there!  I don't care who you are!

[mt10mm]

<----- Glock recoil spring 

Whatever makes it run.

[wingspar]

I know this is an old thread, but I'm new to the 10mm and am spending some time reading thru threads.  I've had my G20 Gen4 for a couple of weeks with a little over 200 rounds of various ammo thru it, including Underwood 180 and 200 grain TMJ's.  I have already ordered 50 rounds of the Underwood 220 hard cast bullets, and until I read this thread, I never gave any thought as to the round being too powerful for my Glock.  It is totally stock, and I plan to keep it that way.

What is the consensus on running these rounds in a stock G20?

[The_Shadow]

Hello Gary, Many have run the 220's in the stock Glocks, more so the 3rd gen and earlier, the gen 4's are newer and yet to be tested as much as the older models.  The ammo is stronger impulse than the lighter loaded stuff like CCI, Remington, Federal, etc.

That being said there have been some feeding issues in all models for different reasons.  Early on Double Tap was getting FTF reports and they shortened the COL of their HC WNFGC 200 and 220 to 1.2420", this improved the feeding.

Underwood uses a slightly different bullet (more of a Truncated Cone) without the gas check, thus it provides better feeding properties.

Now, the rest will reside with the gun and the setups.  You will need to test out how they perform in yours as setup.  The 4th gen RSA should handle the slide speeds better than the older factory springs.  Issues with the 4th gen have been more magazine related with the followers.

You may not experience any adverse issues, ONLY TESTING WILL SHOW THAT!

Best regrads,

[wingspar]

Thanks for the reply.  As you know, one can hear just about anything on forums.  I have heard of G20's having problems with the high pressure stuff, and I've heard of them handling it just fine.  Many modify their guns and some of the problems may reside with the mods, and some may not.  The 220 hard cast bullets are for woods carry, so as not to have to order another box (the stuff isn't cheap) I'm thinking of shooting no more than 25 to see how they run, and hold onto the rest for carry till I'm ready to order something from Underwood.

I did have to send one of the magazines back to Glock.  It would not hold the slide open at all.  A letter from Glock says they are replacing it, but need a physical address to send it to since they don't use USPS.  I have not had any problems with the two I have left, and will use them to try the 220 HCB's.

[wingspar]

Hello Gary, Many have run the 220's in the stock Glocks, more so the 3rd gen and earlier, the gen 4's are newer and yet to be tested as much as the older models.  The ammo is stronger impulse than the lighter loaded stuff like CCI, Remington, Federal, etc.

I finally got to put a few of the Underwood 220 grain hard cast bullets thru my G20 Gen4 yesterday.  I only put 20 rounds thru it as the ammo is expensive, and I want to use this as my woods carry round.  I had no malfunctions.  It performed flawlessly.  I realize 20 rounds isn't a real test, but until I order more, it will have to do for now.  It flung the brass a good 20 feet.

What I did notice is what looked like a bunch of horizontal marks on the cases.  Marks that rubbed off with a finger.  However, some had a horizontal scratch on them shown by the red arrow in the photo below.  Other than that, and I'm not sure that's a concern, I see no indications of problems with the brass.  Do they look ok to everyone else?

I have been carrying the Underwood 180 Gr TMJ bullets for the woods.  Published FPE for the 180 grain bullets is 676 fpe and the published FPE for the 220 grain bullets is 704 fpe.  Is that a significant difference if needed for a black bear?

[wingspar]

Cartridge is from Ammo Manufacture: Underwood 220gr Hard Cast (MT10mm)
Ballistics Information: 10mm Auto
Muzzle Velocity: 1240 fps
Muzzle Energy: 750 ft. lbs
Brass Make/Headstamp: Underwood - Brass
Bullet Make/Weight/Construction/Info; Length 0.7310"/Dia. 0.4010": 220gr. Hard Cast
MEPLAT 0.2640" / Flat Base
Actual weight 216.6 grains   Crimp squeezed bullet to 0.4010"
C.O.A.L.: 1.2585"
Primer: Nickel color
Case: Diameter 0.4215" Crimp Diameter 0.4225" (Tight) Length 0.9880"
Powder Description/Positive ID/Type/Charge LongShot Weight: 8.6 grains

I'm curious.  The Underwood published fps is 1200 fps both on their web site and on the box I have.  Did you get your 1240 fps from testing with a chrono?

[The_Shadow]

If you look further into the linked info you will see that there were some loaded 8.6 grains LongShot and then some at reduced to 8.0 grains which were said to be marked 1200 fps.

Intercooler tested these 8.6/8.4 gr loads;

These ran flawlessly out of the Limited Pro today.

Limited Pro 4.75" 1237, 1231, 1250. Average = 1239.33 FPS/ 750 LBS

The distinct line is the dreaded "SMILE", it is that portion of the brass which is laying at the feed ramp with the least amount of support!  The pressure starts the softer brass to stretch and flow, these are at the point where they are tearing on the molecular level.

BTW, they can not be fixed with any sizing and could experience a catastrophic failure if try to used it again!

[wingspar]

So, Underwood has recently changed the load in the 220 grain hard cast?  I see the second test at 1200 fps now.

I did some research on the "Glock Smile" since I last posted, and this isn't as bad as some.  However, I did find a good video on the "Glock Smile" here. 
https://www.youtube.com/watch?v=20aSjSMKqY4

It's an informative video for guys like me that are just starting with the 10mm.  After watching his video, I measured the fired case and the unfired Underwood 220 Gr HCB's.  My results were the same as the guy that did the video.

New unfired brass.  0.422 OD
Fired brass.  0.427 near the mouth and 0.431 near the base at the smile.  (A bulge not visible to the naked eye).
A fired Remington UMC brass that I happen to have laying here 0.425 top and bottom.

Until I watched that video, I really did not understand what "unsupported case" meant.  You can see where the round is not supported at the feed ramp in the left photo below.  The photo below is two photos combined into one.  On the left is an unfired UW 220 HCB.  On the right is a fired UW 220 HCB case with the crack (smile) facing the feeding ramp.  You can see it no longer drops right into the chamber, but can be pushed the rest of the way easily and removed easily.



I've learned a lot today.  I have come to the conclusion that the 220 grain brass is fine to fire in my G20 Gen4, but I should toss the brass and not save it.  Anyone disagree?

Does the UW 180 grain TMJ round suffer this same problem in a Glock?