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Posted: 5/22/2012 6:52:17 PM EDT
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Several years back I bought an mp5 clone, a BW5. It was a bit worn out an has given me problems from the start. Mostly FTE. Well over the years after replacing the extractor, ejector, ejector spring, and going to plus 4 rollers using original parts, and the lower and handgaurd with clone parts I'm still having trouble.
I took it out for a spin this weekend and the first mag (the one that came with the gun) was fine. The next I tried rapid fire (it is an original HK mag) and had a FTE resulting in a jam every 4-5 rounds. Next mags were an ATI rapid fire no problem, and then the first mag again a mix of slow and rapid fire no problem. Loaded in another mag (dont know which may have been an ATI or the original mag) and started getting jams again. This time I notice something didnt feel right, the recoil wastoo strong, so I broke the gun down. Upon disassembling the gun I noticed the rollers fell out, and upon further inspection the roller retaining plate had broken. Now this is the second time this has happened, and the last time it happened (time before it was shot last) I changed out the rollers to get the bolt gap closer to spec in an effort to curtail the malfunctions (went from 0.004 to 0.008). I'm not sure if the problem cause the plate to break, or if the plate broke and started casing problems. What could be causing this? The gun was getting some wierd FTE's even for this gun. One case actually turned backwards and impaled itself on the extractor. Not sure if that helps. Another thing I noticed is that the bolt gap is perfectly even all the way across, with both carriers I have. Not sure if that matters either. Also when I replace the extrator spring again i noticed the outside edges of the extractor are pretty thrashed like they were contacting the metal of the trunnion or something. Should I replace it and or the spring yet again? Any help would be much appreciated note sure what I should do at this point. I want to SBR it at some point and have the barrel pulled and a new one installed, but I dont want to blow all tht money on a gun that wont run. This gun has become a real money pit for me though regardless, so I really would like to get it running well. Not just on slow fire like it did this time until it shit the bed all the way. |
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Are you still using the factory trigger group, and does the trigger group sit parallel to the receiver? If the trigger housing is not sitting on the semi-auto shelf in a manner to ensure the trigger group is parallel to the receiver, the end result is usually that the ejector is not engaging the slot in the bolt correctly. Most likely it is sitting too low in the bolt slot. My BW5 had a crummy trigger group. It sat parallel to the receiver, but the ejector looked like someone ground it down to fit into the bolt slot and the quality of the metal itself was lackluster. On top of that the safety levers would not release from the trigger pack. It functioned okay, but it definitely wasn't right. I replaced the entire trigger group and moved on. Good luck! |
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Quoted:
Are you still using the factory trigger group, and does the trigger group sit parallel to the receiver? If the trigger housing is not sitting on the semi-auto shelf in a manner to ensure the trigger group is parallel to the receiver, the end result is usually that the ejector is not engaging the slot in the bolt correctly. Most likely it is sitting too low in the bolt slot. My BW5 had a crummy trigger group. It sat parallel to the receiver, but the ejector looked like someone ground it down to fit into the bolt slot and the quality of the metal itself was lackluster. On top of that the safety levers would not release from the trigger pack. It functioned okay, but it definitely wasn't right. I replaced the entire trigger group and moved on. Good luck! I'm currently using the trigger housing/lower from my PTR91. It fits very tightly. The fit on the original was a bit loose. Also I should probly mention my shelf is crooked, though not horizontally. It is level, it's just that it look like one side wasnt pressed all the way against the reciever when they welded it on so one side sticks out a bit more than the other. I dont think that is causing the issue here though. |
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So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. |
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Quoted:
So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. The pack is the original BW5 with an HK ejector. The lower/grip is from my PTR 91. I know better then to use an 308 ejector (dont think it would even fit) or hammer spring. |
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Quoted:
Quoted:
So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. The pack is the original BW5 with an HK ejector. The lower/grip is from my PTR 91. I know better then to use an 308 ejector (dont think it would even fit) or hammer spring. FWIW My SW5 runs better with a .308 Hammer spring...I couldn't get the hammer to set right with a 9mm spring..I took the trigger pack apart twice and that was the only thing that worked..Gun runs %100 but I have broken the strut once since switiching to .308 |
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Quoted: Quoted: So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. The pack is the original BW5 with an HK ejector. The lower/grip is from my PTR 91. I know better then to use an 308 ejector (dont think it would even fit) or hammer spring. Unless you've switched it out or verified it, your BW5 trigger pack most likely came with a .308 hammer spring from the "factory." I know mine did for sure, as did most other guns made with TB parts. Details matter. All I'm doing is asking questions and pointing things out to try and help. No need to get defensive. Hope you can get it sorted out. |
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Quoted:
Quoted:
So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. The pack is the original BW5 with an HK ejector. The lower/grip is from my PTR 91. I know better then to use an 308 ejector (dont think it would even fit) or hammer spring. Of course the 308 ejector will fit. That's how we move a registered sear pack from gun to gun. In fact, you can install a G3 ejector lever and put it in an MP5 and there is no interference. Actually, it's probably quite the opposite. I don't think it ever gets push up enough to even engage the shell case. But you'd have to test that out. Anyway, we're just trying to help here, as others have mentioned. And yes, back when these guns were being built, they were built with HK91/G3 packs. The hammer spring was never changed out by SW. In some cases, Bobcat Weapons figured out that changing to a pistol hammer spring would help them to cycle better and they modified them for that. But not in all cases. IT's worth checking out if you care to take a look. Here's a good description of the differences and how to change them out... http://www.hkpro.com/forum/hk-reference-library/65232-hammer-spring-identification-change-non-pinned-type.html You might already know how to do this, but I thought I'd post a link here for anybody else who would like to learn how. |
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Quoted:
Quoted:
Quoted:
So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. The pack is the original BW5 with an HK ejector. The lower/grip is from my PTR 91. I know better then to use an 308 ejector (dont think it would even fit) or hammer spring. FWIW My SW5 runs better with a .308 Hammer spring...I couldn't get the hammer to set right with a 9mm spring..I took the trigger pack apart twice and that was the only thing that worked..Gun runs %100 but I have broken the strut once since switiching to .308 Some people have reported the same thing. When I changed mine from rifle to pistol spring, it helped with the cycling. So as with so many other things... YMMV. |
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Quoted:
Quoted:
Quoted:
So long as the trigger group sits level, you can forget about the shelf geometry for a minute. Now, if its the straight up factory PTR91 trigger group that you are using, you should be advised that the ejectors are different between 7.62NATO and 9mm trigger packs. The hammer springs for the 9mm are also lighter in poundage. In my opinion both of these things could be causing you some of this grief. The pack is the original BW5 with an HK ejector. The lower/grip is from my PTR 91. I know better then to use an 308 ejector (dont think it would even fit) or hammer spring. Unless you've switched it out or verified it, your BW5 trigger pack most likely came with a .308 hammer spring from the "factory." I know mine did for sure, as did most other guns made with TB parts. Details matter. All I'm doing is asking questions and pointing things out to try and help. No need to get defensive. Hope you can get it sorted out. Didn't mean to come off that way, wasn't trying to be defense or overly curt. Just trying to relay as much info as possible. If its a 308 spring its much lighter than the one in my PTR, IIRC. I think the center of the problem is the broken retaining plate. I just cant figure out if that is breaking, thus causing the problem or is the problem (whatever it is) is causing that to break. But when the retaining plate is intact and not gumming up the works, and when the gun is fired slowly with a known good mag is runs fine, or at least did. I'm just not sure what could be causing it to have problems when rapid firing, and then ultimately shit itself. |
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Check the bolt face to make sure it holds a 9mm round firmly in place. If the 9mm round isn't able to stay in the bolt face on it's own then it's out of spec. I know my Cohaire 9mm bolt face was more like a .40 bolt face, the 9mm round wouldn't stay in place on it's own. I replaced the bolt carrier assembly with HK and now my gun runs 100% reliable.
Also my Cohaire roller plate broke, but my HK bolt has never broken it's roller plate. |
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Quoted:
Of course the 308 ejector will fit. That's how we move a registered sear pack from gun to gun. In fact, you can install a G3 ejector lever and put it in an MP5 and there is no interference. Actually, it's probably quite the opposite. I don't think it ever gets push up enough to even engage the shell case. But you'd have to test that out. Just to clarify I'm aware it would fit in the pack. I just have never tried to drop a 308 ejector'd pack into an mp5. Hence the "if it will fit" statement. Quoted:
Anyway, we're just trying to help here, as others have mentioned. And yes, back when these guns were being built, they were built with HK91/G3 packs. The hammer spring was never changed out by SW. In some cases, Bobcat Weapons figured out that changing to a pistol hammer spring would help them to cycle better and they modified them for that. But not in all cases. IT's worth checking out if you care to take a look. Here's a good description of the differences and how to change them out... http://www.hkpro.com/forum/hk-reference-library/65232-hammer-spring-identification-change-non-pinned-type.html You might already know how to do this, but I thought I'd post a link here for anybody else who would like to learn how. I'll look at that. I'm aware of the assembly/dissasembly process of HK trigger packs, but I wouldlike to be able to determine whether or not its hammer spring is an mp5 o G3. Thanks Overall I'm not sure the trigger pack is the right area to focus. It seems like if there is something causing the roller retaining plate to break that that is the most likely source of the problem. I could swap the whole pack with one from my PTR though (after swaping the ejector obviosuly) as that is a know good pack. What do you guys think? |
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Quoted:
Check the bolt face to make sure it holds a 9mm round firmly in place. If the 9mm round isn't able to stay in the bolt face on it's own then it's out of spec. I know my Cohaire 9mm bolt face was more like a .40 bolt face, the 9mm round wouldn't stay in place on it's own. I replaced the bolt carrier assembly with HK and now my gun runs 100% reliable. Also my Cohaire roller plate broke, but my HK bolt has never broken it's roller plate. Maybe I should just order a new hammer spring, bolt head, and shoulder piece and see what happens. Hmm. |
| Look at the alignment of your receiver rails to your trunion. It should be a smooth transition. If there is any difference that the rollers could hit prior to full lock up, it could cause problems. Also, check for the trunion being square with the receiver. Lastly, when you install the rollers make sure the roll pin is flush with the bolt head and not sticking out. |
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