... Please!  New to HK and have enjoyed reading this section. Fell in love with the USC/UMPs recently and am looking to start my project soon. I plan on running with the USC for a while SBR'd with the ~8" barrel. Will do full conversion at later date. Mostly wanted to hear thoughts on these two calibers, will give you my situation to help:

- Will be SBR with a .45 cal suppressor.
- Have Glock 23 .40 cal with lots of ammo.

Importance levels:
1) sound suppression - which would be quieter with factory ammo out of a .45 can? Is there a significant difference? 5 db means little to me, 20 db is more! I've read too many opinions saying both are quieter that I'm confused now.

2) knockdown power - in the unfortunate chance I may have to use this double NFA scary black item to save my life from a home intruder. Is .45 that much more signifant than .40? I feel confident I can place shots well but I'm realistic and have no experience with my adrenaline pumping in the dark at 3am after being suddenly awoke and having a suppressed Hk in hand.

3) Availability of parts - mainly with the shorter barrel first, are .45 cal parts (barrel, mags, etc) more readily available? What about ammo?

4) Cost/Interchangeability - I'd rather spend more to get what is needed or best for my situation but should parts and ammo be part of the decision from a cost standpoint? I like the idea of having plenty of .40 cal ammo for both my glock and hk... Especially in a hurried grab and go situation.

The bottom line is for a $2-3k+ "toy" I'm not worried about spending an extra $100 to get what's best nor am I worried about saving $50 bc of xyz.

Thank you in advance... I look forward to being part of the Hk family soon. I would appreciate any other thoughts, opinions, advice as well.

I am right now in the middle of the USC/UMP conversion myself. I am waiting on parts which is slowing me down. I would suggest a degree of versatility in your weapons platforms in case you can't find ammo in one caliber you always can use a different weapon caliber.  I am going with the 45 USC/UMP conversion because they look great and I couldn't really find a good AR 45 platform that I really liked. I have gotten a lot of good advice here and also on HK Pro.com.

The benefit of the .40 is 30rd mags vs 25rd mags in the .45. The downside is the .40 bolt and machining required for it to work in the USC receiver will easily add another $600+ to the already high cost of the conversion.

Meh, get both that's what I did. Seriously, get your USC and keep an eye out for a good .40 UMP kit. It will have the stock and lower you need and once the bolt is modded all you'll need to do is chop the original USC pipe and you'll have a 2 caliber SBR.

to me you have to go with .45.  That is what I did.  The usc is already 45---keep it simple!!  

.45

^^ THIS exactly.

FWIW the machining on the UMP bolt costs about $150 and simply removes some metal from one side of the bolt. See here:  http://www.hkpro.com/forum/hk-long-gun-talk/123924-ump-usc-bolt-diffrances.html

Thanks everybody, really appreciate the comments! I've called several places around Houston but found little luck, this is like looking for unicorn dust huh?

Probably will go the gunbroker route if I find a decent price for the .45 in black. Would prefer to support a local shop and don't want to get screwed by some scam artist. Any words of wisdom using GB?

I used gun broker to get mine. It was the only rifle I ever bought from GB. I suggest you look at the positive feedback and if it is an FFL or you can post in the WTB forum on HK pro.com that you are looking for an USC.

Really appreciate everyone's replies. Sent payment for the .45 so it should be arriving at my dealer next week! Also, hk parts dotcom was pretty quick... I already got in my rails and threaded 8" barrel (which looks freaking sweet).  Octane 45 has been paid for, waiting on the permission slip to be cashed... And I will be requesting SBR permission shortly.

Now to start stocking up on range ammo...


Ah, one last thing I need is a light/laser combo to add on a front rail. Thoughts on good ones?

Eta pic