FINALLY - 5 Underwood 10mm Ammo Disections

[Yondering]

The HK roller locked system does not utilize different recoil springs other than each caliber has a different spring.  They utilize, in the 10mm and 40, two different locking pieces ( LP ).  One is for low impulse ammo and the other is for high.  I had the Hi LP installed which is what I also use for my 1200 FPS loads.

If the high-impulse locking piece works correctly with your 180gr 1200 fps loads, I'd say you'd need an "extra high impulse" locking piece (if there were such a thing) for the Underwood loads. 180@1200 is relatively weak, compared to the Underwood stuff, or any "full power" loads, especially considering that 1200 fps is out of your 8.8" barrel. Just off-hand, Underwood 180's are probably at 1400+ from the same barrel?

Looks to me like that gun is just not designed to handle full power 10mm loads.

[Kwesi]

The HK roller locked system does not utilize different recoil springs other than each caliber has a different spring.  They utilize, in the 10mm and 40, two different locking pieces ( LP ).  One is for low impulse ammo and the other is for high.  I had the Hi LP installed which is what I also use for my 1200 FPS loads.

If the high-impulse locking piece works correctly with your 180gr 1200 fps loads, I'd say you'd need an "extra high impulse" locking piece (if there were such a thing) for the Underwood loads. 180@1200 is relatively weak, compared to the Underwood stuff, or any "full power" loads, especially considering that 1200 fps is out of your 8.8" barrel. Just off-hand, Underwood 180's are probably at 1400+ from the same barrel?

Looks to me like that gun is just not designed to handle full power 10mm loads.

I certainly understand your reasoning but my buddy has the exact same gun and runs 165-175's @ 1500+.  Also to be more exact my loads of PP are 1232 and Longshot are 1262.  I also fired Georgia Arms at 1360!

[Kwesi]

Thought you might want to see a pic of the gun we've been discussing:

[REDLINE]

I certainly understand your reasoning but my buddy has the exact same gun and runs 165-175's @ 1500+.

But what do those velocities equate to from 4.6" of barrel?  I'm thinking much lower than you're thinking.  Literally weak or just making it to "warm" by any decent 10mm standard.  Probably around 1250 fps.  So if that's the case, they are much less of a load than the UW 200XTP load.

[REDLINE]

Thought you might want to see a pic of the gun we've been discussing:

Thanks for the pics.  I was curious.

[The_Shadow]

Redline, the remarks were made on GT, when XmmAuto, was buying the Pressure Trace system and the TC with a 10mm barrel to conduct pressure testing.  As we discused the accuracy of such testing and calibration.  He has since sold off the equipment and the TC pistol if I recall.

I also mentioned it here on this form as concern.
http://10mm-firearms.com/factory-10mm-ammo/10mm-ammo-history/

TYVM for the link.

My interest lies in what issues there are or aren't using a strain gage setup as opposed to the copper crusher system or the piezoelectric transducer system.

I did see at the link you provided in reply #21 where you said;  "Using that system would be better than those which use the strain gauge wrapped around the out side of a barrel."  But I saw no additional or other comments regarding the same, either to agree, discuss, or spell out where your thoughts are coming from on that.

So what I'm trying to find is any discussion or general writeup regarding, as you put it;  "the accuracy of such testing and calibration" or the like, negatively toward the strain gage setup.

Can you give me anything toward that light or point me in a general direction?

The second post is were I added my thoughts on the systems...

Here is something to consider...The pizoelectric transducer system employs the transducer flush mounted inside the chamber of the test barrel. Pressures developed by the expanding gases to the cartridge walls causing the transducer to deflect creating a measuerable electrical charge. This change is then converted to a pressure reading in psi.

Systems being sold are being used on the outside of the chamber of the test barrel. The expanding cartridge is not directly acting upon the transducer as in the SAAMI testing. The preceeding line is why I think the results are skeptical for trying to measure outside the barrel.  While the strain gauge outside the barrel system yields results, calibration and accuracy leave me second guessing, I could be wrong!

The other post #19 & #20 was descussing the Krieger test barrels and the internal strain gauge system like those used in actuall SAAMI testing.  I have no way of knowing how Kevin Underwood test his ammo or what system he uses, he may have it outsourced or he may do it in house...he hasn't discussed this that I know of in the forums.

[REDLINE]

Thanks for elaborating.

[Kwesi]

I certainly understand your reasoning but my buddy has the exact same gun and runs 165-175's @ 1500+.

But what do those velocities equate to from 4.6" of barrel?  I'm thinking much lower than you're thinking.  Literally weak or just making it to "warm" by any decent 10mm standard.  Probably around 1250 fps.  So if that's the case, they are much less of a load than the UW 200XTP load.

I'm not sure I'm following your thought process.  I agree that 1250-1300 is what his loads are in a 4.6" barrel.  UW ammo is 1250 out of a standard Glock barrel.  Your point?  I updated the actual velocities above of the loads I fired: 1232, 1262 and 1360.

[REDLINE]

I certainly understand your reasoning but my buddy has the exact same gun and runs 165-175's @ 1500+.

But what do those velocities equate to from 4.6" of barrel?  I'm thinking much lower than you're thinking.  Literally weak or just making it to "warm" by any decent 10mm standard.  Probably around 1250 fps.  So if that's the case, they are much less of a load than the UW 200XTP load.

I'm not sure I'm following you thought process.  I agree that 1250-1300 is what his loads are in a 4.6" barrel.  UW ammo is 1250 out of a standard Glock barrel.  Your point?  I updated the actual velocities above of the loads I fired: 1232, 1262 and 1360.

I'm just saying your buddy's loads of 165gr and 175gr bullets at +1500fps from 8.8" of barrel are weaker than the UW 200gr loads that hit 1250fps from a G20 4.6" barrel. 

For example, a 165gr 10mm UW load rated for 1400fps would probably be doing around 1650fps from your friend's 8.8" barrel, and in my mind is weaker still weaker in terms of PSI developed than the UW 200XTP load rated for 1250fps from a G20, which should be doing 1450fps from an 8.8" barrel.  And your buddy's 165gr load at +1500fps is weaker than either of those two UW loads.

And yes, you said;  "My 180 gr FMJ loads chrono'd @ 1232 with PP and 1262 with Longshot.  I also chrono'd some factory Georgia Arms Canned Heat 165's @ 1360.  All these were fired in the CA89-10."  What I'm saying about these is that they are outright weak based on the combination of your 8.8" barreled CA89-10 and the velocities you've shown compared to the UW 200gr XTP load.

So my point overall is that neither your buddy's loads at +1500fps or your PP and Longshot loads are anywhere near as powerful as the Underwood 10mm 200gr XTP load.  And therefore I'm not surprised that your buddy's loads at +1500fps and your PP and Longshot loads are safe to shoot in your CA89-10, while the UW 200XTP load isn't.

Now I'm just hoping I haven't entirely missed what you were actually saying and/or asking.

[REDLINE]

Redline, the remarks were made on GT, when XmmAuto, was buying the Pressure Trace system and the TC with a 10mm barrel to conduct pressure testing.  As we discused the accuracy of such testing and calibration.  He has since sold off the equipment and the TC pistol if I recall.

I also mentioned it here on this form as concern.
http://10mm-firearms.com/factory-10mm-ammo/10mm-ammo-history/

TYVM for the link.

My interest lies in what issues there are or aren't using a strain gage setup as opposed to the copper crusher system or the piezoelectric transducer system.

I did see at the link you provided in reply #21 where you said;  "Using that system would be better than those which use the strain gauge wrapped around the out side of a barrel."  But I saw no additional or other comments regarding the same, either to agree, discuss, or spell out where your thoughts are coming from on that.

So what I'm trying to find is any discussion or general writeup regarding, as you put it;  "the accuracy of such testing and calibration" or the like, negatively toward the strain gage setup.

Can you give me anything toward that light or point me in a general direction?

The second post is were I added my thoughts on the systems...

Here is something to consider...The pizoelectric transducer system employs the transducer flush mounted inside the chamber of the test barrel. Pressures developed by the expanding gases to the cartridge walls causing the transducer to deflect creating a measuerable electrical charge. This change is then converted to a pressure reading in psi.

Systems being sold are being used on the outside of the chamber of the test barrel. The expanding cartridge is not directly acting upon the transducer as in the SAAMI testing. The preceeding line is why I think the results are skeptical for trying to measure outside the barrel.  While the strain gauge outside the barrel system yields results, calibration and accuracy leave me second guessing, I could be wrong!

The other post #19 & #20 was descussing the Krieger test barrels and the internal strain gauge system like those used in actuall SAAMI testing.  I have no way of knowing how Kevin Underwood test his ammo or what system he uses, he may have it outsourced or he may do it in house...he hasn't discussed this that I know of in the forums.

Thanks for pointing out what you said in your second post.  I missed that the first go around.

I guess I'm not sure there is an issue there or not, whether a piezoelectric transducer system measuring pressure from inside the chamber (let alone the copper crusher system) is actually any more accurate than a strain gage measuring stretch of steel based on a pressure level being contained by it from the outside of the chamber.

SAAMI's ANSI publication #205 doesn't say there is.  They simply say they only recognize the copper crusher and piezoelectric transducer methods, but don't say for what reasoning either way.  They don't comment one way or the other on the strain gage system measuring pressures from the outside of the barrel.  Plus that publication was last copyrighted 19 years ago.  That doesn't prove anything, I'm just saying.

Did a strain gage system even exist 19 years ago on the open market to average people like the one from RSI and Southwest Products?

I'm noting that in their literature they say;  The strain gage was invented back in 1938 and are a common item in most laboratories.  So the idea is to get strain readings of the outside barrel surface to the nearest millionth of an inch via a polymer material with very fine conductor loops on the surface that measure the stretch of the barrel steel by sensing changes in electrical resistance, that are then converted into pressure via a Wheatstone bridge producing output voltage directly proportional to the change in resistance of the strain gage, which is then passed through instrumentation amplifiers and an analog to digital converter where a microcontroller chipset sorts out what the end result in pressure in PSI is.

Well that's easy enough to understand for a caveman or sasquatch.   Okay, it's over my head.  BTW, I got all that from here -
http://www.shootingsoftware.com/ftp/PTII-Help.pdf

I don't know, but I have yet to come across anything explaining why a strain gage setup is any less accurate than a piezoelectric transducer setup.  And just because I haven't come across it doesn't mean it doesn't exist, so I may be wrong too.   I'll tell ya what though, if I could afford it I would have it, no different than having my chronograph.  That is unless some information would surface showing the strain gage setup to be a literal waste of time and money.  So far information like that doesn't seem to exist.

[Kwesi]

I certainly understand your reasoning but my buddy has the exact same gun and runs 165-175's @ 1500+.

But what do those velocities equate to from 4.6" of barrel?  I'm thinking much lower than you're thinking.  Literally weak or just making it to "warm" by any decent 10mm standard.  Probably around 1250 fps.  So if that's the case, they are much less of a load than the UW 200XTP load.

I'm not sure I'm following you thought process.  I agree that 1250-1300 is what his loads are in a 4.6" barrel.  UW ammo is 1250 out of a standard Glock barrel.  Your point?  I updated the actual velocities above of the loads I fired: 1232, 1262 and 1360.

I'm just saying your buddy's loads of 165gr and 175gr bullets at +1500fps from 8.8" of barrel are weaker than the UW 200gr loads that hit 1250fps from a G20 4.6" barrel. 

For example, a 165gr 10mm UW load rated for 1400fps would probably be doing around 1650fps from your friend's 8.8" barrel, and in my mind is weaker still weaker in terms of PSI developed than the UW 200XTP load rated for 1250fps from a G20, which should be doing 1450fps from an 8.8" barrel.  And your buddy's 165gr load at +1500fps is weaker than either of those two UW loads.

And yes, you said;  "My 180 gr FMJ loads chrono'd @ 1232 with PP and 1262 with Longshot.  I also chrono'd some factory Georgia Arms Canned Heat 165's @ 1360.  All these were fired in the CA89-10."  What I'm saying about these is that they are outright weak based on the combination of your 8.8" barreled CA89-10 and the velocities you've shown compared to the UW 200gr XTP load.

So my point overall is that neither your buddy's loads at +1500fps or your PP and Longshot loads are anywhere near as powerful as the Underwood 10mm 200gr XTP load.  And therefore I'm not surprised that your buddy's loads at +1500fps and your PP and Longshot loads are safe to shoot in your CA89-10, while the UW 200XTP load isn't.

Now I'm just hoping I haven't entirely missed what you were actually saying and/or asking.

Ok gotcha.  One difference I realized is that it seems that you are assuming the velocity gain is 60+ per additional inch.  I verified in my notes that the Georgia Arms Canned Heat 165's averaged 1245 out of my EAA Witness Limited which equates to about 30 additional FPS/inch.  Not sure if this is relevant.

Thanks for everyone's input! 

[sqlbullet]

I have a CETME with a roller lock system that is identical in design to the system in this gun.  I think the UW ammo, plus the way the chamber is cut, is setting up a perfect storm as it were.

The LP is calibrated for 10mm ammo's impulse, but as we all agree here, most 10mm ammo out there is really 40 S&W "+p" not really 10mm.  I am going to assume the LP for 10mm is calibrated to the ammo made by the big boys for 10mm.  This is generally 180 grain at 1150 to 1200 fps, not the 1350 to 1400 fps the 10mm can make.  40 S&W maxes out at about 1050 for 180 grain.  All speeds for a 4.5" barrel.

So, if they make a different LP for 180@950 (factory 40) vs 180@1200 (factory 10mm) then you are definitely going to need a heavier LP for full power 10mm (180 @1400).

What happens is the lower mass LP allows the rollers to unlock before pressure has dropped, which causes adequate support to become inadequate support.

I think you will need a higher mass LP to get this to function with UW ammo.

[nickE10mm]

Great information here ....

I got way into testing 800X years back and, more recently, testing Longshot at max loads also.  In my experience, the 800X outperforms LS in velocity by a small (insignificant?) margin across all loadings.  Accuracy is still undetermined.  There are quite a few loads where LS really excels in accuracy, 9.2-9.4gr LS under a 180gr XTP is one of them. 

Anyhow, I sitll have a bunch of my original bottle of 800X left.  Keeping it for a rainy day.... but overall, I only use Longshot since 800X needs hand weighing.  My next project is to do an accuracy workup at max velocity with 200gr XTP and WFNGC bullets, hand-weighing both the LS and 800X.... if there is any noticeable difference, I'll post it up, otherwise, I'll probably just carry on using my Longshot in the fuure. 

Again, good info here, though.  Kevin @ Underwood is doing a great job and I think his charge weights are spot-on where they should be. 

[Kwesi]

I have a CETME with a roller lock system that is identical in design to the system in this gun.  I think the UW ammo, plus the way the chamber is cut, is setting up a perfect storm as it were.

The LP is calibrated for 10mm ammo's impulse, but as we all agree here, most 10mm ammo out there is really 40 S&W "+p" not really 10mm.  I am going to assume the LP for 10mm is calibrated to the ammo made by the big boys for 10mm.  This is generally 180 grain at 1150 to 1200 fps, not the 1350 to 1400 fps the 10mm can make.  40 S&W maxes out at about 1050 for 180 grain.  All speeds for a 4.5" barrel.

So, if they make a different LP for 180@950 (factory 40) vs 180@1200 (factory 10mm) then you are definitely going to need a heavier LP for full power 10mm (180 @1400).

What happens is the lower mass LP allows the rollers to unlock before pressure has dropped, which causes adequate support to become inadequate support.

I think you will need a higher mass LP to get this to function with UW ammo.

I believe you and the others are correct.  Only problem: they don't make another LP for more potent ammo, the two choices are Hi or Lo LP's.  OTOH: when I think back to when H&K developed the MP5 in 10mm the ammo was much more limited & thus less potent.  I'm very happy using my weaker 180's and I would have used them for the hogs except the UW was recommended.

[4949shooter]

Well at least your gun wasn't damaged and more importantly, you weren't injured.