[JJ Hiryuu]

Hey everybody, I don't post often as usually any issue I ever could have has already been solved somewhere here. I have a Vector MP5 clone that has been tweaked and rebuilt and SBR'd. It's been a wreck since NIB but MOST of the issues have gradually been worked out. I'm down to an intermittent extraction/ejection issue. The gun will shoot fine sometimes with mildly inconsistent ejection pattern for a whole range trip, then the next it will fail to clear a case, which will get mashed into the chamber area, which of course then bends my extractor spring, which leads to yet more extraction and ejection issues. This happens suppressed or not.

It's an RCM bolt head with HK extractor and I have a steady supply of fresh springs for it. Ejector lever and spring are new HK as well, as is the recoil spring. Bolt gap is .017 and has held there for quiet some time now. I mostly shoot GECO, S&B, and Federal 124gr.

I've been tinkering with it a bit and think I might have a G3 hammer spring in here so I've got the proper spring on the way. While looking around for any cause of the problem I finally took note of the wear on my bolt carrier's face. I figured the finish was just worn but started to wonder so I searched here and couldn't find anything quite like it. It seems to be a bit more than just the finish being worn away. Any ideas? Possible issue? At this point I'm near ready to just drop a complete POF carrier group in and see what happens.

 

[rhouston8]

I have similar and other wear patterns on a variety of my MP5 carrier/bolts...from factory parts to RCM to MKE to POF.
While you can certainly get a stacking of intolerances that ultimately causes real problems the wear patterns on my various MP5 parts hasn't yet caused an issue that I know of. Just my experience over the last several years of shooting, cleaning, and messing with them.

The most interesting "wear" I've had to date was an isolated dented up roller. Weird. And the gun still ran fine despite the rounded surface on the roller basically being hexagonal or whatnot. never discovered why it happened. Just replaced the roller.

 

[11C ABN]

May I ask what manufacture bolt carrier?

Ive only seen it twice and one was a aftermarket carriers (not RCM) the other POF?

Can you take a straight metal measurement tool and check the rails. look to see if one of the rails maybe canted towards the trunnion and/or if the rails may have slight misalignment at the trunnion contact.

Not that the POF carrier was an older one.... I'm unaware if the newer carriers have had this issue. note it's in the archives concerning soft POF bolt carriers. search for it

 

[11C ABN]

also if you could take a few pictures of the trunnion and barrel area. What's the area look like?

What's the bolt head roller size?
Correct and identical rollers sizes in the bolt head? i.e. -4 on one side and +6 on the other side. booth should be standard or of the same size. +2 and +2

Locking Piece Picture please.
Check the wear and check to ensure correct Lock Pc.

RCM or HK works best.

 

[BravoSector1]

also if you could take a few pictures of the trunnion and barrel area. What's the area look like?

What's the bolt?
Correct and identical rollers sizes in the bolt head? i.e. -4 on one side and +6 on the other side. booth should be standard or of the same size. +2 and +2

Agree. Parts interface locations may lend some thought as to what is causing the wear...normal or not.

 

[JJ Hiryuu]

I'll get the detailed pictures of the other hardware tonight.

Bolt head, locking piece and carrier are all RCM. Rollers are +2 on both sides as far as I can tell. The markings are faded but both seem to be +2 according to my not very good calipers. They are round as well with no obvious dents. Thanks for the help so far, I'll get back with the other pictures once I'm home.

 

[JJ Hiryuu]

Ok, I did the best I could with a phone camera for more detailed pictures. I don't see anything unusual other than a LOT of carbon around the breech area. I can't even see that carbon without poking my camera in and turning flash on, it's all at angles I can't view from just naked eyeball looking in. The roller recesses seem clean as I do make sure to clean those out. The rails appear straight and even, not sure how easy it is to tell in the picture down the receiver.

EDIT: My replacement MP5 hammer spring came in today. It is a totally different length and composition than the spring that was in there. The new one is a thinner gauge wire and a good half inch longer so this was certainly a potential problem area.

 

[JJ Hiryuu]

Took the Vector clone out again today with the correct hammer spring installed.

Suppressed with an Octane 45HD using a trilug or direct thread mount I was getting very odd issues where the hammer was not being reset. I'd end up hammer down with a live round in the pipe.

Unsuppressed I did not have the hammer set issues but the random fail to extract/eject issues came back. Ejection pattern looks normal but every so often a few will be weak and just dribble out, and at least once in a 30 round magazine I will end up with a empty case floating around the chamber area with a live round pressed up under it.

I'm really at a loss here.

 

[kwesi]

FYI: I installed a rifle hammer spring long ago because I use it in 9mm, 10mm ,5.56x45 and 7.62x39 so I'm thinking that was not your problem. Have you tried 2 different mags? Who made them? What type of buffered stock are you using? Choate thick H buffer? One last thought: except for the 10mm I use the rifle extractor springs. Have you tried it?

 

[11C ABN]

Ok Possible issue....

The receiver has a steel pictinny rail welded to the receiver' I assuming because of the welds located at the top of the receiver. If you strip the weapon down completely and run your finger inside the receiver along the top portion' can you feel these welds?

Next can you take a lighted picture from the bottom of the receiver and the back of the receiver of the case deflector. Look for a harsh mark at the beginning of the case deflector like a strike mark. This mark may run the length of the case deflector.

if and I say if all of these items are there' you may have a carrier strike that's rising carrier.

2nd. Could you please take a picture of the top of your bolt carrier and the sides of the bolt carrier body.

Ill wait and add if I think theirs an added issue after I see pic's of the bolt carrier.

P.S. Thank Paul123 & JFK because these are the guy who taught me and others what to look fore.

 

[JJ Hiryuu]

I started looking through my gun where you guys suggested and didn't see anywhere the bolt could strike or get hung up, no signs of it happening either. In the process though I discovered that at some point I mixed up some parts with my HK33 clone, which is a Ghillie rebuilt C93. At some point during a detail strip of both guns I put the Century made trigger box into my MP5. I pulled the trigger pack from the 33 clone, and another spare I have and compared all three. The Century made pack only sits correctly in the lower housing it came with. The shelf cut on it is completely different than the other two. Swapping between them in the MP5 and looking through the ejection port I discovered the Century housing sits WAY too low and I was not getting good case contact on the ejector lever, and it was just barely resetting the hammer. The only spare lower I had was a converted G3 lower and housing so I moved my MP5 specific parts over to that, installed it and took it to the range today.

250 rounds from 2 brands in 4 different magazines (HK curved, HK Straight, POF, MKE) suppressed and unsuppressed and I had zero malfunctions. Ejection is now a LOT more positive. I don't know why the height of the trigger group never occurred to me before. Thank you all for your help and suggestions!

Here's a picture of it with the steel lower on there. I think I might leave it this way, looks pretty good.

 

[Fade2Blk]

Props for admitting your error!

 

[JJ Hiryuu]

Props for admitting your error!

Yeah the trigger pack was my bad for sure. I had taken that Century messed up trigger box out of both 33 and MP5 clones because it just looked rough. At some point it snuck back into my gun. Didn't realize until now just how messed up for shelf height it was! It's been a long process getting this gun working like it should, many other threads I've read through, posts here and there, and some help from some talented gunsmiths here.

I gotta say it felt good to finally dump a 30 round magazine suppressed and not have a single issue! Gonna need a lot more 9mm.