HK USC/UMP 460 Rowland Conversion -- Chrony results...
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Thread: HK USC/UMP 460 Rowland Conversion -- Chrony results...

  1. #1
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    Default HK USC/UMP 460 Rowland Conversion -- Chrony results...

    Since my original barrel from my Tactical Excellence SBR build was just collecting dust -- and since I had recently caught the 460 Rowland bug by converting a Springfield XD "Compact Tactical" and Glock 30 within the past month -- I decided to ream the original carbine length barrel to accept 460 Rowland.

    I did a little range work with it today with a Chrony...

    Unfortunately, unlike the converted pistols -- the USC doesn't have an extractor strong enough to properly headspace 45 ACP ammo in the lengthened 460 Rowland chamber. Therefore, I will not be reaming my SBR barrel to 460 Rowland specs.

    I ran two 5rd strings of Georgia Arms 185gr Nosler 460 Rowland ammo (stated pistol velocity was advertised as 1400 fps from a 5" barrel). The average velocity from the 16" HK USC barrel was 1692 fps = 1175 ft/lbs... Definitely in 44 Magnum territory.

    The 460 Rowland ammo is a "thumper" in the HK USC/UMP conversion. After the range session, I field stripped the carbine to clean and change barrels back to SBR configuration. I saw no evidence of abnormal wear -- or any form of damage. The recoil spring is evidently strong enough to handle the increased bolt velocity in combination with the stock neoprere buffer in the rifle. Upon examining the spent cases, I observed no bulging or splitting to indicate dangerous premature extraction from the chamber. I was concerned about this possibility because of the blowback design on an intended low pressure cartridge.

    I did not attempt to shoot any 230 gr or 255 gr 460 Rowland ammunition -- nor do I think I will. I figured I was plowing new ground by even attempting a 460 Rowland "conversion" to a $3K+ SBR project... I do feel comfortable with an occassional diet of the 185 gr stuff -- possibly to pig hunt with.

    Here's a pic I took for the Chrony:


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    this is awesome! How are there no replies to this?? Have you shot any of the more potent 460 rowland loads in the last 4 years? Is a barrel swap on a USC something you could do at the range or is it more involved? I'm thinking about a usp 45 tactical with a second barrel/recoil spring assembly set up in 460 rowland. It would be nice to have the same option on the USC so you can move between 45 and 460. I did a bunch of searches and it looks like you are the ONLY person to have ever done this. I saw the other thread were people were advising against it due to double the chamber pressure. I wonder if anyone is crazy enough to try it with the 454 casull? Now THAT would be insane. You should post some vids of your conversion shooting the 460 stuff!

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    While some don't favor anyone replying to old threads, I'm glad you revived this thread.

    I have an interest in the 460 Rowland fired from HK's, having added a custom muzzle brake to a Mark 23 and shortened some 460 Rowland brass to 45 Auto length, with excellent effect. I'd also be interested in shooting 460 Rowland from our USC in 45 Auto, but hadn't considered it because I had no idea whether that might be damaging to the firearm.

    Does anyone have other thoughts on whether the USC is likely built to do well with this powerful a loading?

    Even if the OP may not see these replies (but as he's still active he may), his post is good information that's probably of interest to at least several right now and it could be worth seeing if anyone has information or educated judgment to add to it now.
    Last edited by trenace; 01-06-2017 at 03:31 AM.

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    I haven't shot anymore .460 Rowland in the USC/UMP. With the simple blowback design of the rifle - I don't think it is advisable to do so for safety.

    However, since moving to Alaska I have converted an HK USP Tactical 45 to a dedicated .460 Rowland pistol successfully.


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    Quote Originally Posted by flyandscuba View Post
    I haven't shot anymore .460 Rowland in the USC/UMP. With the simple blowback design of the rifle - I don't think it is advisable to do so for safety.

    However, since moving to Alaska I have converted an HK USP Tactical 45 to a dedicated .460 Rowland pistol successfully.


    Sent from my iPhone using Tapatalk
    Yeah, i saw your other thread about that and am following in your footsteps! Had a question for you over there too when you have a sec:
    HK USP Tactical 45 - .460 Rowland Conversion

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    Quote Originally Posted by flyandscuba View Post
    I haven't shot anymore .460 Rowland in the USC/UMP. With the simple blowback design of the rifle - I don't think it is advisable to do so for safety.
    Thank you! I won't be doing it then.

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