FINALLY - 5 Underwood 10mm Ammo Disections

[Kwesi]

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

Amen to that.  BTW: when I placed the order with Kevin for the XTP 200's I had not read his warning in red nor did he ask me if my gun had a ramp.  If I had or if he had then the order would have never happened because the HK Roller locked weapons system has no barrel ramp.  In the end I should have noticed that on his web site.

[REDLINE]

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.

You are correct in my loose assumption, just than that I generally think about it as adding an additional 100fps per 2" of additional barrel length.  And your are correct, it doesn't always work out that way depending on the specific 10mm Auto recipe being tested.  It's simply the rule of thumb I use and most of the time works out pretty well in what I've seen.  Again, certainly not always though.

[REDLINE]

Only problem: they don't make another LP for more potent ammo, the two choices are Hi or Lo LP's.

This thought is over my head personally, but is there a possibility that someone with such know-how could modify the LP made for higher power loads to handle souped-up 10mm loads the same way there's a difference between the two LPs that already exist?

I expect it's probably a stupid thought, I just thought I'ld throw it out there anyway.

[Kwesi]

This should put a new spin on some of the posts:  HK lists specific factory ammo and which locking piece to use.  These are recommended loads for the MP5 in full auto using the HI LP

Norma 170 gr. JHP @ 1461
Masters 150 gr. JHPN @ 1481
Hornady 155 gr. JHP @ 1445
Hornady 170 gr. JHP @ 1406
Winchester 175 gr. STHP @ 1377

I also find the following very interesting

Norma 200 gr FMJ @ 1195
Hornady Custom 200 gr FMJ @ 1124

BUT

PMC 170 gr JHP @ 1329 REQUIRES THE LO LP

I believe the key to this operating system has much to do with the "Impulse" of the load - don't have a clue how to measure!

[Intercooler]

Are those velocities out of your barrel length or a pistol?

Can't see Norma ever hitting that in any pistol.

[REDLINE]

These are recommended loads for the MP5 in full auto using the HI LP.....

Gosh, hardly any of those loads exist anymore.

[Kwesi]

These are out of the MP5 barrel (same as mine). Many of those loads do not exist but as I stated earlier it's been many years since H&K developed the MP5-10 for the FBI.  I've got some of those Norma and Win ST's but I'm happy with my FMJ loads.  I believe it, while weak for the 10mm, will still do the job on the hogs and in semi.  But if I'm wrong then we will go to the happy switch

[REDLINE]

I guess I look at it that you're good to go anyway since with the barrel length of 8.8" you still get great velocity, even with heavy weight bullets.  Kind of a win-win.  Lower pressure loads with great velocity compared to what a common handgun platform is capable with any ammo.

[4949shooter]

Kwesi, you might want to try the standard Hornady 200 grain XTP load. Doc chrono'd 1050 fps out of his Glock 20 with these. With the velocity increase from your MP5-10 barrel, and a deep penetrating 200 grain XTP, this might be a good load for hogs without the concern of excess pressure.

[Kwesi]

Kwesi, you might want to try the standard Hornady 200 grain XTP load. Doc chrono'd 1050 fps out of his Glock 20 with these. With the velocity increase from your MP5-10 barrel, and a deep penetrating 200 grain XTP, this might be a good load for hogs without the concern of excess pressure.

Thanks!

[The_Shadow]

I'm supprised no one pulled down a 165 gr loading to see the difference from the 155 grain.  It was shown in a video that the 155 was pushed to 1500 fps if I recall...

Underwood 155 gr TMJ old load 1374 FPS @ 650 ft lbs
Underwood 155 gr TMJ new load 1551 FPS @ 828 ft lbs

[REDLINE]

I'm supprised no one pulled down a 165 gr loading to see the difference from the 155 grain.

Does anyone have an Underwood 10mm 165gr load(s) they would disect for us and post the findings?

[Kwesi]

Only problem: they don't make another LP for more potent ammo, the two choices are Hi or Lo LP's.

This thought is over my head personally, but is there a possibility that someone with such know-how could modify the LP made for higher power loads to handle souped-up 10mm loads the same way there's a difference between the two LPs that already exist?

I expect it's probably a stupid thought, I just thought I'ld throw it out there anyway.

It's not a stupid thought at all.  Some of the clone manufactures make a gun that was never produced by H&K.  A Vector 53K is a good example (K stands for short).  BTW: this is one of my favorite guns that is chambered in .223 and has a 5" barrel.  They had to grind down a factory locking piece for this platform to function.  The angle on each side of the LP is what determines the timing and cyclic rate on these platforms.  That said I do not expect anyone will attempt this with the 10mm issue I've experienced.  Good thought though!

[REDLINE]

Only problem: they don't make another LP for more potent ammo, the two choices are Hi or Lo LP's.

This thought is over my head personally, but is there a possibility that someone with such know-how could modify the LP made for higher power loads to handle souped-up 10mm loads the same way there's a difference between the two LPs that already exist?

I expect it's probably a stupid thought, I just thought I'ld throw it out there anyway.

It's not a stupid thought at all.  Some of the clone manufactures make a gun that was never produced by H&K.  A Vector 53K is a good example (K stands for short).  BTW: this is one of my favorite guns that is chambered in .223 and has a 5" barrel.  They had to grind down a factory locking piece for this platform to function.  The angle on each side of the LP is what determines the timing and cyclic rate on these platforms.  That said I do not expect anyone will attempt this with the 10mm issue I've experienced.  Good thought though!

It's funny how I'm sometimes baffled by what's all available in the marketplace.  That said, it then leaves me even further baffled by little things here and there that aren't.  I'm quite sure you're not the only one out there who would take advantage of an LP designed to handle the likes of Underwood 10mm Auto power level ammo if one were to be made available.

[MrRedbull616]

never was impressed with Todd Bailey clones.  Vector probably made the best CLONE you could get.

High pressure ammo in a fluted chamber probably not the best idea. HK didn't design the MP510mm for such loads...when it was designed (and short lived) it was during an era of subsonic speeds and deep penetration thinking.

So not only are you using ammo in a platform it really wasn't designed for...your using a CLONE (CA89 of all things) of the original platform.