Thanks Intercooler, and I am sorry about your experience with the DPM system on your gun. After reading your post I must conclude it is a real and accurate report on your weapon and your experiences. I can only speak for three handguns I have used this system with: Glock Gen 4 G20, Walther P99 .40 S&W (2000 year model), and the Springfield Armory Mill-Spec .45 ACP.
     One thing I agree on, it appears to work better on some models than others as far as reduced recoil (compared to stock); however, it DID help on ALL of them, and was worth the $100.00 to spend on ALL OF THEM.  There is no doubt that the one it helped the MOST was the Glock G20, followed by a CLOSE second with the Mill-Spec .45 ACP. I believe that Gun Weight, or maybe Slide weight might have something to do with how much you feel in reduction (along with HEAVY HOT LOADS).  The photo you showed does not do the device JUSTICE, and the overall length looks to be somewhat "shorter" then the G20 or .45 1911, which COULD affect the travel needed to properly use the Triple Spring (Remember that with G20 and 1911 were dealing with 5" barrels).  I took a saw and CUT one in half to examine the TRIPLE spring on the inside of the Rod, and it is cool how they made it work on the PROGRESSIVE SPRING design.
     One last thing Intercooler, When shooting your gun using DPM, did you notice the "reverse muzzle flip" after you installed the DPM over stock? That was the part that got me the most. That is where I really seen the grouping gets better as I learned to use it with the system.  I might not be calling this by the right terminology, so I will try to explain it and hopefully you can relate.
    As you know, the DPM works on the principle of "Triple Progressive Spring" design, just like an automobile engine and its Valve Springs. In Cars (or in my case Drag Racing and HIGH RPM engine power profile), we experience what is known as "VALVE FLOAT", which is where the weight of the valve (in this case the Slide of the gun) determines the spring pressure needed to prevent "VALVE FLOAT", or the Camshaft follower staying on top of the camshaft lobes and not "BOUNCE" and loose contact with the Cam Lobes. The problem here for years was in using a SINGLE VALVE SPRING was if you tried to increase the pressure needed to keep the valve float from happening, the pressure would be SO GREAT that it would Burn the lobes off the cam on flat Tapped hydraulic or solid lifter cams. Many is the time We used to have to take the secondary spring (on a double spring) out of the spring set, start the car using only the LIGHTER outer spring and break in the camshaft, take the heads back off the car and install the second valve spring AFTER the Camshaft was broken-in.  By installing the SECOND SPRING the spring allowed us to get the higher pressure while not having all the heave spring pressure of a single spring on the "CLOSED SPRING PRESSURE". 
     In Sum it all up, the weight of the valve in relation to how far it is lifted off the valve seat in the head could be controlled by using a LIGHTER SPRING FOR THE FIRST HUNDRED THOUSANDS of lift, and as the valve lifted further off the seat the SHORTER second spring would kick in and increase spring pressure as it needed it to keep the lifters from bouncing off the cam lobes!!!
THIS IS EXACTLY WHAT IS HAPPENING HERE WITH THE SLIDE AND DPM PROGRESSIVE SPRING DESIGN.  When the slide first begins to move, it is using LIGHT pressure (the outer spring with a LITTLE Of the second spring) where it starts is 9 lbs., then about half way up the length of the rod (slide travel) it rises to around 15 to 17 LBS, then as it nears the end of travel the third spring jumps (about ¾ of the way to the end) to 26 lbs.  Now this happens in "REVERSE" that it starts out hard to quickly bring the slide back to the starting point, but the beauty here is it works PROGRESSIVELY in that pressure dramatically decreases as it comes back down so you don't have the "SLAM" down of a single HIGH PRESSURE SPRING!!!   As you can imagine, this means that it WONT over sling the muzzle downward near as much since the pressure is greatly reduced as it comes back down to 9 lbs.
     That Mr. intercooler was what I was referring to as "reverse muzzle flip", the pulling down of the muzzle so you can re-acquire the target much more easier than with the heavy hit of a single spring.  That is where I really seen the difference of this system, which allowed me to DOUBLE TAP using HEAVY loads keeping them in a TIGHT GROUP.
     I would like to hear if  you experienced this as well as I did, and to thank you for your replies.

I use a G20 Glock with the DPM Triple spring system with the Silver outer spring, and I use Underwood ammo with this spring set up;

With the silver spring I can go between:

Underwood 165 Grain FMJ
underwood 180 Grain FMJ
Underwood 200 Grain FMJ
Underwood 220 Lead Cast rounds

with the Yellow Spring outer I use the:
115 Extreme Defender
140 Grain Defender
Both from Underwood.
I use a Chronograph to record the FPS of the shots I make, and in ALL of the Underwood rounds, it EXCEEDS all FPS claims from Underwood by at least 30 FPS (most are around 50 to 60 FPS Greater than advertised).
I have shot over 1000 rounds over 18 months, and only during the first two months did I have any FTF issues, or until I got the right outer springs figured out on the DPM system. Over the past year not ONE SINGLE FTF happened, and I group (on double tap) 2 to 3 inch groups on 25 to 30 yard target ranges.  I absolutely love my G20, better than any gun I have ever owned. And thanks to Underwood, I can claim that I hit 1705 FPS (802 ME) on there 135 Grain XTP hollow-point on AVERAGE!!!
Take that .357 - 125 grain owners,,,, Eat Poo and LIVE!!!

Attack Members? WTF, I guess I should not be attacked for saying the results for something that is a game changer for being called a commercial or ad service. I don't work or sell ANYTHING GUN RELATED in anyway, or work on anyone's guns.  It is ONCE in a great while that someone invents something that actually works, but to work OVER and OUTSIDE what they claim is quite rare, this is the real deal and I wont bother to mention it on this forum anymore, as it appears that the I.Q. of most of the people who reply (I AM NOT ATTACKING, YET!

    It is one thing for someone to post something NEW, but quite another to have a review that over 18 months has passed of continued usage of this device, and to hear what the results are during that time to present, DON'T YOU THINK? This is the last post on this subject I will do, I just cannot believe my replies, when I see people posting "Single Spring Questions" when someone has invented a device like this that TOTALLY revises that old and last Century technology.  Good luck guys with your single spring "NON PROGRESSIVE" reduced recoil attempts.

One more thing to INTERCOOLER, and his answer on "HE HAS ONE", and I guess he has the DPM system? Why don't you tell these people what this is and back me up on this, because if you indeed have one, you know I am 100% right, and no other spring system out there can compare!!!

Good luck everyone, and I hope you don't ATTACK me any more...LMAO

Thats great, a commercial hugh? Well, I guess you guys can continue to use a dam single spring that sucks like hell, when you could use a PROGRESSIVE spring that builds pressure as the slide goes back, instead of ONE HARD ASS SPRING.  I paid for ALL my springs, NO FREEBEES, and I live in Nashville TN, NOT ATHENS GREECE where there made. At least I will have a frame on my G20 5 years from now. Good luck guys. You people are so smart...NOT!!!

To hell with all this single spring crap.  go here to solve that problem, it is in step with the 2015 world as Single springs are last century!!!

http://www.dpm-systems.com/

They make this UNBELIEVABLE system for all makes of guns, and IT WORKS!!! read my post after using this for 18 months now.

This just kills me, why in the world are you people using a single spring set up, when DPM makes the best triple PROGRESSIVE system ever made. It is right at $100.00 and there is NO comparison of any single spring to this Tech. Look up DPM reduced recoil systems, that SOLVES any and all problems with the 10mm.

I have been HOOKED on the 10mm round since 1984 when I met Col. Cooper, who invented the round in Nashville Tennessee at Berryfield Airforce Base.  But I never bought a gun that used it till November of 2013 because of numerous complaints on the problems with current doing well with the round as far as recoil and frame problems.
View the DPM Video I made over a year ago:
https://www.youtube.com/watch?v=SD31pGGq4ig

The reason for this post is that after 18 months, and over 800 rounds fired through with this system, here is the results and what happened over time.
It took about three months to fine tune for EACH BRAND OF AMMO USED, and to make a chart to what DPM rod and external springs used. If I had to pick an overall rod/spring combo that worked well with all types (in other words, a combo that would use all types without any Failure to Feed issues, it would be the HD (heavy duty) 28 lb. (it has an S on the end of the rod) and the Silver External Spring.  Now IF I was going to use the Underwood Ammo (it don't matter WHAT grain bullet from them guys at Underwood, there stuff is all just AWSOME) Exclusive I would use the HD 30 Lb. Rod and Silver Spring. By using the 28 lb. Silver set up, I have used Winchester and also Georgia Arms (http://www.georgia-arms.com/) range ammo with NO issues.
     I cannot rant and rave ENOUGH about the difference that this DPM system makes.  I read the follow up post, how I sound like an ad for their product, and I am sorry for that, but it is just THAT DAM GOOD.  What really makes the difference is that I can actually DOUBLE TAP this gun with this system intact, and using the Crap Gen 4 factory Glock Spring there is NO WAY you can do this... I know this to be fact. How you can tell how good this is, is that you can look at the frame where the slide hits the Plastic lower frame...I have used this since the gun was NEW, and there is NO MARKES what so ever. This to me makes more difference than recoil.

The real information here is after I got the DPM dialed in, I have not had ONE SINGLE FTF problem, and it is as constant as the northern star as far as reliability is concerned. The thing is that once you get used to this system (DPM) it is TOO HARD to go back, and I never would.  Where you really see this is in rapid fire, and the ability keep it GROUPED in a 2-3 inch group at 30 yards. 

When you compare this to a wheel 357 (I have a custom 686 6") there is NO comparison as far as putting lead downrange "GROUPED" closely. Combine that with the MUCH lighter weight of the G20 and I have to say that this is the BEST CARRY heavy firepower that the world had ever seen. EVERY person I have let shoot this gun (many LEO's) had a fit over it, and many have bought this gun.  Funny thing is, they came to me and said "it just don't shot like yours did that day" and once they seen the DPM, every one of them bought it for their own guns (even non glock).
     I guess that is all I have to say, in that after 18 months this is still as good as the first day (actually better now that I got it tuned for specific ammo). I can only attest to this: EVERYONE who has bought this system that I have shown it to SWARES BY IT, BOUGHT IT, and USE IT daily!!! This is the device that has taken the bite out of the 10mm, making it the best dam semi-auto full power handgun ever made in the world!!! Long live the G20 Glock with DPM systems reduced recoil systems!!!
I love my Glock and I have a LOT of cash in it as you can read my specs on my gun.  I wanted to protect the frame above anything else.
I have made the following mods on my Gen4 G20:
KKM 5.2 Match barrel with threaded end for silencer or Compensator.
lone wolf 10mm compensator
Glock Store Titanium Striker for Glock  LS002L
Glock Store Titanium Safety Plunger LS004
Glock Store Custom Side Cover Plate FBI T0996-Vd
Glock Store Double Diamond 3.5 Lb. Connector LS003
Glock Store Extended Slide Stop Lever e GESSL01-C
Glock Store Stainless Steel 3 Pin Kit CoT0782G4
Glock Store Extended Slide Lock lat T1450-BK
Glock Store Trijcon Bright & Tough Night Sights "NOVAC"
Rear esT0964-A
Glock Store Magazine Custom Base Plate T1004L-V
Glock Store Frame Insert kPG-FI21G4
Lone Wolf  LWD Barrel M/20 Conversion to 40 S&W 4.6 Stock Length LWD-2040N
Lone Wolf Magazine Extension +2 (10/45) LWD-7172 KIT
Walmart Protec LED Mini Pic/rail light
3 different: DPM Mechanical Recoil Reduction system for Glock G20 Gen4 (standard, 28 lb. and 30 lb.)

Here is the Website for DPM recoil Systems:
http://www.dpm-systems.com/en/mechanical-recoil-systems/dpm-for-glock
(MECHANICAL RECOIL REDUCTION SYSTEM (MS) DPM for Glock 20, 21, 41 SF 4th generation)
You can contact the DPM customer support for a "Heavy Duty" system that uses a different rod, a 28 Lb. and/or 30 Lb. rod.  Both sets use the same 3 different springs (external) for fine tuning the type of ammo used.

I got the DPM system, and I was wondering if you got the HD System? they make the standard 26 Lb. Deal, but I bought the HD system plus another control rod. the HD system came with a 28 Lb. rod, and I custom ordered the 30 Lb. Control rod, and it works GREAT!!! When Using the Underwood 155 Grain XTP Hollow (1600 FPS) it took the 30 lb C.R. to keep the spent shell casings at an ejection distance of 10 feet from the gun, and also by marking the frame with Blue Machinist Dye (or a yellow magic marker will do close to the same) to see the impact of the slide to the frame will tell you if the slide is hitting the frame TOO hard. By using the LONG outer spring (gold) and the 30 lb. Control Rod, I was able to see that the slide would BARLEY hit the frame, and that was with the HARDEST shooting ammo you can buy on the market. Be proud you got the BEST recoil reduction system money can buy, all that other bulshit (Steel guide rods, Tungsten guide rods, and the BIG single 22 and 24 lb. springs) don't work worth a dam. If you really want to beeee cool, by the KKM 5.2 inch match barrel for the 10mm with the threaded end, and get the Lone Wolff Muzzle Brake to let it work together, and you will really be surprised by the smoothness, and actions of the gun. You will think you will think you have another weapon in your hands....

     Hello everyone, I just found this forum, and I really impressed by all the information I have been reading about. I am a certified 10mm NUT, and have been since 1983!!! I have not owned a 10mm yet till November of last year when I bought a Glock G20 Gen 4.  I have replied to a post elsewhere in this forum, and some of the information I am posting here is redundant, but this is important enough that I thought I would pass this on to everyone.  This is many months of R&D on my part, and one of those things that TRULY WORK 100% as advertised by the company.  It works SOO WELL, that I would call it a GAME CHANGER in the handgun world.  This system worked so well, I bought it for my other three guns (semi-auto) as well.  You can read below as I posted some of this to a response on "Using Heavy ammo from Underwood in the G20 10mm handgun without damaging the frame, and also reducing the amount of recoil so as to keep on target with your grouping patterns.  I am not kidding when I say "It removes at least 30% of the actual recoil out of the Glock G20", and this system is fully adjustable as it comes with several outer springs, and different control rods. If you are tired of changing single springs, and the adapter from Gen 4 to Gen 3 so you can use the stiffer springs, and the stronger steel guide rod, which USED to be the way to go THEN READ ON,  It is NO MORE!!! Like one of the other readers on this thread, I used to HATE Glocks, and swore I would NEVER buy one. The only reason I ever got one, is 10mm.  I have been a 10mm fan since 1983, and other than getting to shot one in 1989 (Delta Elite Colt), I just never got around to it.
     As a mater of fact, shooting and guns had left my life for the better part of 18 years, and I just got back into it last year.  The first thing I did was go back to wanting the 10mm and MAN did I ever have a LOT to learn.
Anyway, as I found out the choices for 10mm are NOT MANY, and it seems that Glock was the only company that stuck it out in terms of development with 10mm. After 6 months of Research on the matter, in November of last year, I bought the G20 10mm Gen 4.  I am happy with the gun, but like most of you, I DONT WANT A 40 Short and week load in my 10mm. I found out about Underwood, and never looked back.
I have found, through my research, the ANSWER to the recoil problem, that just plain kicks the fire out of Glock store, and all the rest of the solutions offered called DPM Systems. They have the answer PERIOD!!! Go to http://www.dpmsystemsusa.com/ and solve the 10mm problem with the g20. They offer the Heavy Duty kit (I called Dmitri's, the owner of DPM) and I got three control rods (26, 28 and 30 Pounds) and SEVERAL springs to sort out the bullet grain/Powder loads.  I used Blue Machinist dye and marked the plastic part of the frame so I can SEE how hard each bullet I used marks the frame. I am SOO HAPPY, as it not only takes about 30% of the actual recoil OUT OF THE GUN USING THE 180 Grain Underwood loads, but you can tell that the slide BARELY touches frame (it takes much Testing, swapping and making a chart to record this info so you know WHAT ammo to use with what springs).
     This Triple Spring System is absolutely the Problem Solver to the G20 and using HARD AMMO, and not hurting the guns longevity.  I made a video on YouTube if you want to see how it works at:  https://www.youtube.com/watch?v=SD31pGGq4ig   
I hope this helps any of you, and I am going to Post this on the main topic page tonight as well, to share what I have learned and help any of you that have been using single springs to help this problem. Guys...IT WORKS!!!  It was the best $150.00 I ever spent on any automatic gun. Since then, I put it (DPM) in all my guns from my 1911 to my Walther P99 it worked so well.  Good luck, and if you have any questions you can reply to my new post I am about to put on the main page. Thanks...Thomas

I don't mean to get off subject (which it really isn't), but this thing your doing, wanting to know about changing springs, and the adapter from Gen 4 to Gen 3 so you can use the stiffer springs, and the stronger steel guide rod, USED to be the way to go. It is NO MORE!!! Like one of the other readers on this thread, I used to HATE Glocks, and swore I would NEVER buy one. The only reason I ever got one, is 10mm.  I have been a 10mm fan since 1983, and other than getting to shot one in 1989 (Delta Elite Colt), I just never got around to it.
     As a mater of fact, shooting and guns had left my life for the better part of 18 years, and I just got back into it last year.  The first thing I did was go back to wanting the 10mm and MAN did I ever have a LOT to learn.
Anyway, as I found out the choices for 10mm are NOT MANY, and it seems that Glock was the only company that stuck it out in terms of development with 10mm. After 6 months of Research on the matter, in November of last year, I bought the G20 10mm Gen 4.  I am happy with the gun, but like most of you, I DONT WANT A 40 Short and week load in my 10mm. I found out about Underwood, and never looked back.
I have found, through my research, the ANSWER to the recoil problem, that just plain kicks the fire out of Glock store, and all the rest of the solutions offered called DPM Systems. They have the answer PERIOD!!! Go to http://www.dpmsystemsusa.com/ and solve the 10mm problem with the g20. They offer the Heavy Duty kit (I called Dmitri's, the owner of DPM) and I got three control rods (26, 28 and 30 Pounds) and SEVERAL springs to sort out the bullet grain/Powder loads.  I used Blue Machinist dye and marked the plastic part of the frame so I can SEE how hard each bullet I used marks the frame. I am SOO HAPPY, as it not only takes about 30% of the actual recoil OUT OF THE GUN USING THE 180 Grain Underwood loads, but you can tell that the slide BARELY touches frame (it takes much Testing, swapping and making a chart to record this info so you know WHAT ammo to use with what springs).
     This Triple Spring System is absolutely the Problem Solver to the G20 and using HARD AMMO, and not hurting the guns longevity.  I made a video on YouTube if you want to see how it works at:  https://www.youtube.com/watch?v=SD31pGGq4ig   
I hope this helps any of you, and I am going to Post this on the main topic page tonight as well, to share what I have learned and help any of you that have been using single springs to help this problem. Guys...IT WORKS!!!  It was the best $150.00 I ever spent on any automatic gun. Since then, I put it (DPM) in all my guns from my 1911 to my Walther P99 it worked so well.  Good luck, and if you have any questions you can reply to my new post I am about to put on the main page. Thanks...Thomas