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Discussion Starter #1
I own a sear that I would like to use in a PTR 91, HK 53 and a MP5-40. I've been told by various people that switching between these weapons require that you change out not only the sear but other parts as well depending on the caliber. Does anyone know of a comprehensive listing of which parts are required to be changed per weapon family.

I'm envisioning something like this ....

Weapon Parts Changed
MP5-9MM N/A Baseline
MP5-40 Sear and Disconnector?
HK 53 or 93 Sear and ?
HK 51 Sear and ?

I'm also wondering if someone can lead me to some information about a timed vs an untimed trigger pack? What does that mean and if an untimed trigger pack is dangerous then why did someone build that with an expensive sear in there?

Thanks for any insight and guidance.
 

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Unrepentant HKHolic
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Its mainly the ejector, sometimes the hammer spring will need to be changed for rifle calibers I run a rifle caliber in mine and it works fine for 9mm 40cal just fine.............
 

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The ejector for various calibers needs to be changed. I use a rifle hammer spring in all my hosts with great success. You will need an mp5-40 sear trip lever installed to run in the 40. The mp5-40 trip lever can remain in the sear pack and be used with all other calibers to.
 

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It's going to be a bit confusing as you come up to speed but it's allot simpler than it sounds. I went thru this learning curve a few years ago. Assuming your sear is in a pack now, it was set up for either 9MM ( or 40/10 mm - all pistol caliber is the same), .223 or .308. When you move between these calibers, you move the pack to the new hosts trigger housing and put in the right ejector. 1 push pin, takes 2-3 minutes top while at the range. Lots of easy videos on this - no disconnector or or other issues. I always bring 2-3 hosts when I shoot and am popping the pack in and out in the lane.

There are 3-4 different strength hammer springs you can use in your pack. The heavier springs are designed for larger caliber - most of us put in a heavier spring and it runs with all ammo - might slow pistol caliber cycle rate down a bit but that's the only issue I've ever heard of. Little more work but you can easily swap hammer springs too - depends on the hammer design but once you see it done - nothing to it.

The retimed hammer is something else. The aftermarket sear you spent so much money on isn't exactly like the original (unless you've got something called a DLO box). This difference creates a slight change in geometry. I ran my sear pack with the original HK hammer for 9 months and it is not a problem nor to my knowledge is it dangerous. It's just that because of the change in geometry, the HK hammer doesn't lock as far back when riding on the auto sear so you can get light primer strikes in certain guns. I got them on a PTR 32P where the primer wasn't being hit hard enough despite the strongest hammer spring. You can buy a retimed hammer for your pack (easy to install yourself) and it is designed to "cock" fully back. That's it - nothing to worry about - lots to learn as you started. Good luck. Matt
 

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Change your trip lever to a 40/10mm style and leave it. Have ejectors for each caliber and extra ejector springs and axles for when you loose them. I changed my hammer springs out to rifles and use them in all calibers. Once you change the hammer spring and the trip lever replaced it takes less than a minute between guns to change the ejector.
 

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Discussion Starter #7
It's going to be a bit confusing as you come up to speed but it's allot simpler than it sounds. I went thru this learning curve a few years ago. Assuming your sear is in a pack now, it was set up for either 9MM ( or 40/10 mm - all pistol caliber is the same), .223 or .308. When you move between these calibers, you move the pack to the new hosts trigger housing and put in the right ejector. 1 push pin, takes 2-3 minutes top while at the range. Lots of easy videos on this - no disconnector or or other issues. I always bring 2-3 hosts when I shoot and am popping the pack in and out in the lane.

There are 3-4 different strength hammer springs you can use in your pack. The heavier springs are designed for larger caliber - most of us put in a heavier spring and it runs with all ammo - might slow pistol caliber cycle rate down a bit but that's the only issue I've ever heard of. Little more work but you can easily swap hammer springs too - depends on the hammer design but once you see it done - nothing to it.

The retimed hammer is something else. The aftermarket sear you spent so much money on isn't exactly like the original (unless you've got something called a DLO box). This difference creates a slight change in geometry. I ran my sear pack with the original HK hammer for 9 months and it is not a problem nor to my knowledge is it dangerous. It's just that because of the change in geometry, the HK hammer doesn't lock as far back when riding on the auto sear so you can get light primer strikes in certain guns. I got them on a PTR 32P where the primer wasn't being hit hard enough despite the strongest hammer spring. You can buy a retimed hammer for your pack (easy to install yourself) and it is designed to "cock" fully back. That's it - nothing to worry about - lots to learn as you started. Good luck. Matt
Thank you for the guidance on this subject. I think I might buy the parts needed and keep them in separate plastic bags so I know what's what. I will finally achieve my dream of shooting all these HKs on FA from the MP5-40, HK51, HK53, HK91, MM23e ... I've only got the MP5-9mm and HK21E (Reg Rec) to rock so far.
 

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I thought the trip lever for the 21 & 23 worked in the 40 cal MP5. If I'm correct then that is one less step to worry about.
I simply bobbed (ground) the face of the trip lever while it was still in the pack to work in my 40 cal guns.
 
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