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Posted: 8/20/2026 4:10:25 PM EDT
| How does a suppressor affect a mp5/sp5 function? I've read that you might have to change rollers? Does the type of suppressor make a difference in that regard? |
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Originally Posted By OmegamanX: How does a suppressor affect a mp5/sp5 function? I've read that you might have to change rollers? Does the type of suppressor make a difference in that regard? Full size will run fine with or without can with no roller change. K model may require depending on combination of bullet weight, shouldered or not and can flow through. Object is not to over cycle the bolt carrier and it's easier to do on the K due to the less mass. |
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Originally Posted By chargerdude70: Full size will run fine with or without can with no roller change. K model may require depending on combination of bullet weight, shouldered or not and can flow through. Object is not to over cycle the bolt carrier and it's easier to do on the K due to the less mass. Caveat that if its a MKE made fullsize it probably came with a 120 degree locking piece and should be swapped out to 90/100 degree for suppressor usage to avoid roller dents and just prevent excessive fouling inside the receiver for good house keeping. |
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The SP5K-PDW may require changing the locking piece to a #28, which may also require a change in the rollers to ensure bolt gap is in spec. Full-size SP5 does not need the locking piece changed. The rollers only need to be changed in one of two scenarios. First if you change the locking piece and doing so causes the bolt gap to be out of spec. Second if you have an out of spec gun from the factory (I’ve not seen this on an unaltered factory German gun). The addition of a suppressor by itself does not result in the need to change rollers. |
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My full size POF and K sized AP5-P both run fine with or without a suppressor. But, to avoid damage if using a K sized gun, a stock/brace AND shooting heavy ammo and a suppressor, it’s a good idea to go to a 90 or 80 degree locking piece. This is to prevent roller damage to the upper. So far my AP5-P will function with a 90* lp with a suppressor. It runs all bullet weights. I need the original (100*?) lp for it to run 147gr bullets unsuppressed. Now that my gun has a few rounds through it, I’m going to try the 90 again. If you change the locking piece you should check your bolt gap. You may need to change rollers to keep it in spec after the change. FWIW: When I had a K made by PTR, it ran like a champ when I installed the 90* lp. All guns are different. |
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| Most MKEs seem to come with the 100 degree LP now. I haven’t swapped LPs in my Zenith Z-5RS or full size HK SP5. On my SP5K-PDW, I swapped to the RCM 90 degree LP as I was running into some issues with the 80 degree (#28) LP with some ammo. Even with the 90 degree, it didn’t like 150 grain Syntech when paired with a low backpressure suppressor (Milkman). |
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Originally Posted By Aphex: Caveat that if its a MKE made fullsize it probably came with a 120 degree locking piece and should be swapped out to 90/100 degree for suppressor usage to avoid roller dents and just prevent excessive fouling inside the receiver for good house keeping. FWIW I had the problem with a POF-5, too. I used the stock locking piece, shot it suppressed (and FRT'd), and ended up with roller dents. |
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Originally Posted By OmegamanX: How does a suppressor affect a mp5/sp5 function? I've read that you might have to change rollers? The actual roller diameter sizing is determined by your measured bolt gap using feeler gauges. Consult your manufacturer's instructions for measuring and setting this critical gap or if they have specifics (if any) regarding a non-standard contraption like the MP5k-SDs out there. Always confirm your bolt gap is set within spec before changing anything else. Different suppressor architecture and larger volume can resolve gas blowback issues. Suppressor length also has a little bit to do in helping cut down gassy blowback but ultimately ammo selection is most important. HUXWRX and Dead Air seem to be the outfits claiming they're concerned with the least blowback on MP5/MP5k guns. I wouldn't know since I've been using a vintage non-serviceable K-baffle can on my full size gun for a long time and have never needed a different locking piece or rollers. |
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