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Discussion Starter #1
Hey guys, I know this topic is probably beat to death, but I really just need a conclusive answer if I can get one. I have a USP .40 full size LEM Heavy, and I want to convert it to the light weight. I bought a light TRS and FPBS last night, but I'm not sure what I need to do with the hammer return spring, if anything. I'm really looking to lighten up the take-out and the break. Ideally I'd like to get it down to about 5-5.5lbs... I never shoot it from full double action, so I'm not too concerned with the full pull weight, but rather the "prepped" double action. I'm certain I'll see results with the new TRS and FPBS, but I wasn't sure if I should leave the present hammer spring or go with something different. Anyone with constructive feedback would be very helpful to me... Thanks!

-Alex
 

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If it came from factory as Heavy LEM, then yes, you'll need the original V1 hammer spring (214300) to make it a light LEM, as I am sure they replaced your hammer spring with the heavy spring that normally comes with the LEM kit. That, and the light TRS.

You shouldn't need the FPBS.
 

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Discussion Starter #4
Ok, so one for hammer spring, one for no hammer spring. Any other takers? I'll go ahead and install the FPBS since I already ordered it; I figure it couldn't hurt... I just want to feel comfortable with replacing the hammer spring before I spend more to ship it than the part costs... Thanks for the first two replies, guys!
 

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Your USP should already have the light FPBS (209296) in it, unless HK swapped it out with the heavy FPBS for heavy LEM. I don't see why they would do it, since the official LEM installation instructions did not require replacing the FPBS. The only 2 springs that would be replaced would have been the TRS and Hammer Spring. So, logically, what do you do to reverse the process? Put the original springs back.

What is your gun's date code?
 

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Discussion Starter #6
"AE". Looks like I'll give the hammer spring a shot. Thanks!
 

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I say switch all three out...and if you do in fact already have light springs, you will now have back up replacement parts! :)
 

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If you have a "factory" USP LEM pistol you should have the "heavy" spring set. All three are easily changed and the set of three will cost ya $20 from HKI in Columbus GA. $5 each and $5 to ship.

The easiest spring to change is the hammer spring. The trigger rebound spring is a PITA. The heavy LEM TRS is made from square section wire and is easy to spot. The Firing Pin Block spring is easy to change with the right roll pin punch.

I converted my USP9C from V1 to V3 and eventually to LEM. Following all the instructions I replaced all three V1/V3 springs and ended up with a horrible trigger. Browsing thru the parts list I noted the Light LEM springs for the trigger and firing pin block. Re-used the V1/V3 hammer spring. 5.3 pounds. Every shot. No internal polishing.

-- Chuck
 
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