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Discussion Starter #1
I have a BW5, runs great with standard pressure 9mm in the 115-126gr range, but becomes balky, lots of FTE's with the 147gr or 158gr ammo. Seeing as how I intend to have a NFA registered can/suppressor put on at some point, I would like to get it running with the heavies first.

Advice I have received was:
1. Replace the extractor, ejector, extractor spring with real HK parts first
2. Replace the hammer spring with a real HK MP5 version
3. Change the locking piece to a MP5SD version if none of the above solved it

Is that good or bad advice? What else?

TIA
 

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I have a BW5, runs great with standard pressure 9mm in the 115-126gr range, but becomes balky, lots of FTE's with the 147gr or 158gr ammo. Seeing as how I intend to have a NFA registered can/suppressor put on at some point, I would like to get it running with the heavies first.

Advice I have received was:
1. Replace the extractor, ejector, extractor spring with real HK parts first
2. Replace the hammer spring with a real HK MP5 version
3. Change the locking piece to a MP5SD version if none of the above solved it

Is that good or bad advice? What else?

TIA
I'd start with #2. Look at this thread for identification:

http://hkpro.com/forum/showthread.php?t=65232
 

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I run all three of my BW weapons with factory HK lowers with rifle-caliber hammer springs. They also have all HK internals (bolt, bolt carriers, etc.). My BW5 SBR frequently sees 115gr, 124gr, 147gr, and 158gr rounds--the latter two with my suppressor. I've had no problems or balky situations.
 

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I run all three of my BW weapons with factory HK lowers with rifle-caliber hammer springs. They also have all HK internals (bolt, bolt carriers, etc.). My BW5 SBR frequently sees 115gr, 124gr, 147gr, and 158gr rounds--the latter two with my suppressor. I've had no problems or balky situations.

retro-recap...

Person 1: "I have this problem. How can I fix it?"
Person 2: "I don't have that problem at all."

Person 1 (thinking): "Gosh, I feel so much better now, but my gun still doesn't work."

:D
 

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I have a BW5, runs great with standard pressure 9mm in the 115-126gr range, but becomes balky, lots of FTE's with the 147gr or 158gr ammo. Seeing as how I intend to have a NFA registered can/suppressor put on at some point, I would like to get it running with the heavies first.

Advice I have received was:
1. Replace the extractor, ejector, extractor spring with real HK parts first
2. Replace the hammer spring with a real HK MP5 version
3. Change the locking piece to a MP5SD version if none of the above solved it

Is that good or bad advice? What else?

TIA
It wouldn't hurt to change those items out. If i were you, i'd wait till you got the suppressor and have trouble with 147g ammo. The suppressor will create more back pressure and you might not have problems with fte's. If you are runnin good with 115-124g ammo and only plan to use the 147g suppressed, i'd leave it alone until it has problems. but if you plan to use 147g unsuppressed to, i'd go #2 first then number 1.
 

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I have a BW5, runs great with standard pressure 9mm in the 115-126gr range, but becomes balky, lots of FTE's with the 147gr or 158gr ammo. Seeing as how I intend to have a NFA registered can/suppressor put on at some point, I would like to get it running with the heavies first.

Advice I have received was:
1. Replace the extractor, ejector, extractor spring with real HK parts first
2. Replace the hammer spring with a real HK MP5 version
3. Change the locking piece to a MP5SD version if none of the above solved it

Is that good or bad advice? What else?

TIA
If you get down to the LP course of action, you may want to consider the MP5K LP instead of the SD. It is a bit less extreme than the SD locking piece and would be what I would try, especially if you are going to run the gun F/A and suppressed and F/A with hotter 115 and 124 grain ammo.

As an aside, what 147s have you tried? It's odd that 115s and 124s would work fine but that you'd have issues with all 147s. Maybe the load you've tried is particularly weak or has a bullet profile that the weapon doesn't like.

HTH
 

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Discussion Starter #7
As an aside, what 147s have you tried? It's odd that 115s and 124s would work fine but that you'd have issues with all 147s. Maybe the load you've tried is particularly weak or has a bullet profile that the weapon doesn't like.HTH
I have tried three 147's, Atlanta Ammo, Federal Premium JHP, American Eagle FMJ, plus two brands of FMJ 158's, Privi Partisan and another commercial brand I forget...

none run reliably, I am at a loss as to why. since we cannot own any registered SBR's in AL I am going to have to have the can pinned and welded to my barrel, I cannot afford a sear at current prices so this is going to be a suppressed semi-auto, MP5 profile with a permenantly mounted suppressor...hence the sense of urgency to get to the bottom of this, I will not be shooting non-subsonic ammo once the can is on the gun....doubt I will ever spring for the sear, would rather spend the $15K and get a nice used Miata...or a couple of decent used Jeeps...sheesh...
 

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I have tried three 147's, Atlanta Ammo, Federal Premium JHP, American Eagle FMJ, plus two brands of FMJ 158's, Privi Partisan and another commercial brand I forget...

none run reliably, I am at a loss as to why. since we cannot own any registered SBR's in AL I am going to have to have the can pinned and welded to my barrel, I cannot afford a sear at current prices so this is going to be a suppressed semi-auto, MP5 profile with a permenantly mounted suppressor...hence the sense of urgency to get to the bottom of this, I will not be shooting non-subsonic ammo once the can is on the gun....doubt I will ever spring for the sear, would rather spend the $15K and get a nice used Miata...or a couple of decent used Jeeps...sheesh...

I read the 'NFA' part of your first post too quickly. Doesn't change anything really, though.

One of those types of heavy ammo should have worked fine. FWIW, 158s should not be run in an MP5 due to possible increased wear on the recoiling parts.

Have you checked bolt gap? Maybe you are near the edge of acceptable range and plus or minus rollers would help. I would certainly check it before swapping any parts out, given that the gun seems to run with 115-124 grain ammo.

HTH
 

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Discussion Starter #9
Have you checked bolt gap?
lost my feeler guage, but I will get a new one and do that before I move on, the last time I checked this gun, about a year ago when it was new, it was right in the middle of the spec range, but that was a few thousand rounds ago....
 

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Discussion Starter #10
FWIW,
Getting the real HK extractor, extractor spring, ejector, and hammer spring in place fixed all of my reliability problems with the heavy ammo. Since I did it all at once, I cannot point to any single one of those as the cure. Gun runs 100% now. I am guessing that since I will get even more back pressure from the can once it is in place, I hope this is the end of my problems and dinking with locking pieces will be unnecessary.

Upon closer inspection of the bobcat ejector, I believe it was not lined up perfectly with the groove in the bolt and may have been dragging more than it should have, it was well worn on the rear surface of the top.

I did borrow a feeler to check bolt gap and the gun remains about in the middle of the spec range, so good to go on that count.
 

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I have a BW5, runs great with standard pressure 9mm in the 115-126gr range, but becomes balky, lots of FTE's with the 147gr or 158gr ammo. Seeing as how I intend to have a NFA registered can/suppressor put on at some point, I would like to get it running with the heavies first.

Advice I have received was:
1. Replace the extractor, ejector, extractor spring with real HK parts first
2. Replace the hammer spring with a real HK MP5 version
3. Change the locking piece to a MP5SD version if none of the above solved it

Is that good or bad advice? What else?

TIA
Can you clarify at all just what type of FTE it's getting? Is the empty left stuck in the chamber, or is it clear of the chamber but still inside the receiver?

If it's stuck in the chamber, I'd first replace the extractor and extractor spring. If it's clear of the chamber but still inside the receiver, go to the ejector lever next.

As for the hammer spring - I've had weak hammer springs (MP5 spring in a G3) cause some FTFs, but if the rounds are firing, then the hammer spring is most likely just fine. An MP5 should run just fine with a rifle hammer spring, it will just have a slightly lower ROF in full auto, and will be harder to pull the cocking lever back.

If it's firing, the locking piece should be ok.

One other thing I've seen - some of the clones have play between the trigger pack and the receiver. Some of them have needed shims placed between the pack and the front shelf and that has solved the problem cause by the extractor lever not being close enough to the slot in the bolt carrier.

So quick recap -
1. Replace extractor spring and/or extractor first
2. Check ejector lever for wear, maybe change to German HK part
3. Be sure trigger pack is held up to receiver with no slop
 
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