Looking for owners with problems with the MM23 beltfed .223

[Bob T]

I have a MM23E and over the past ten months have had numerous problems. It ran great for about 5000 rounds but then things went downhill.

Michael has been helpful but the problems continue.

Here is an abbreviated list of the problems:

At around round count 300 the extractor claw snapped off

About round count 500 the ejector snapped in two at the pivot hole.

At round count 5000 the belt would not advance reliably. Sent the gun back to Mike(1).

After getting that fixed the gun started to have the hammer follow the bolt home in FA mode resulting in failure to fire. Sent it back to Mike(2).

Got the gun back and withing 300 rounds it started to have the same hammer follow on problem. Locking piece snapped in two during the 300 rounds. Sent it back one more(3). Mike replaced the receiver and bolts when he could not determine what was causing the problem (Thank you Mike!!)

Took the "new" gun out and about 300 rounds later the hammer snapped in two at the strut hole. Ordered two new retimed hammers from HK Parts expressed shipped in order to have the gun ready for the Big Sandy shoot.

At the Big Sandy Shoot the gun would only function in semi, was back to hammer following the bolt home in FA mode.

Spoke with a couple of fellow MM23 owners at the Big Sandy and they indicated they were having similar problems with parts breaking.

I would like to hear from other MM23 owners both good and bad experiences. I have used Wolf/Tula ammo and Federal XM193, no reloads or off brands.

When the gun works it is an absolute blast but I am getting discouraged with all these problems.

 

[maschinenpistole]

I've got about 500 rounds through mine in semi and full auto. I have had only two problems so far - one not being the gun itself but because of an un-timed trigger pack. I had a roller instead of a friction-type sear trip installed. The other issue - I was unable to get the gun into full battery requiring me to charge the rifle two or three times (links/operator error?) This lasted for about two belts and I don't have that problem anymore. I'm new to the beltfed scene and like mine a whole lot. I haven't got anywhere close to what you have put through your gun, so I don't think I would be qualified to say anything else. Hope things work out for you. Mike is a great guy!

 

[mattnh]

subscribed...

 

[DINK]

This is probably out in left field, but try pulling the buffer assembly out of the stock. I just got done sending mine back to Mike because the two parts of the main tube separated where they are welded together. My 23E was running like a nose, happily eating up cheap Tula/Wolf ammo and giving me no headaches when it started doing what you describe- it would stop running with a live round in the chamber, the hammer forward, and a light hit on the primer.

I'm not sure how a broken buffer assembly would cause it, but it's the only part on the gun that doesn't look perfect. It only takes unscrewing two machine screws, so pull it out and see what it looks like.

 

[Bob T]

DINK, good call, thank you!

I pulled the buffer assembly out of the stock and it is cracked through for about 3/4 of the way around the tube about 3/4" behind the mounting flange.

Got a call into Mike to see if I can get a new one which I hope will solve the problem.

 

[DINK]

No shit! I thought I was grasping at straws, but maybe there's something going on here. I'm sure Mike will take good care of you.

 

[JTinIN]

Dink

If the buffer assemble broke completely or even moved much, one would tend to think this might make the impact harder and allow mover movement of the bolt ... might have to be a yearly check.


Bob
Has Mike had a chance to look at the gun and your trigger pack with sear yet (could send at least the trigger pack with sear by USPS Reg mail full insured)?

Four friends have MM23e: one of the guys that I barely know does not fire his much as he is a collector not shooter, one works great with no issues in 5.56 and 308 with a post sample trigger pack, one took Mike setting up the sear pack and is fired in 5.56 and 308 (this friend is out of state), the MM23e that is shot the most had a locking piece break early on that Mike replace and ran perfectly until the barrel was lacking nearly all the rifling at 20K (many long belts at air planes) and now is on a 2nd loaner barrel (mine) and my MM23eK has worked well with one broken part, that was replaced by Mike and I just ran a thousand plus rounds last weekend with a few misfeeds (actually failure to cleanly eject the fired case) on lower power ammo, that swapping locking pieces took care of (since it is a K model with two length barrels have two locking pieces) and/or wear in of the new part (did not have the issue with same ammo when went swapped back locking pieces). Good Luck

There have been reports that the Wolf paper wrapped 55gr ammo is lower power than the older 20 round longer boxed Wolf ammo, however, ended up after a few belts both versions of Wolf ammo tended to worked great along with the 75gr Wolf which if still could get might be the standard food for it. Also shot some LC XM193 and tracer ....

Sounds like you need to load up a thousand rounds in good links (no rusty ones etc.) of XM193 from boxes (I stay away from the bulk pack for very good reasons) or similar NATO spec ammo, clean/lube the gun and check the head space etc. Then take it out for the next shoot and record what happens. Stopping to swap barrels every 200 rounds or at least letting it cool some (same nominal specifications as one should be shooting a SAW) and then run a bore snake through the cold barrel at around 600 rounds or after, when / if you have any issues. Take good notes and see what issues you are having. At that point if it is working good try some Wolf ammo (55gr FMJ or maybe heavier). Also do you have retimmed hammer, who did you trigger pack, what hammer spring do you have etc.

Take Care, good discussion ....

 

[eyegun]

I broke a bolt early on (trying to find a pic- it was an obvious heat treat issue, not geometry etc). Mike sent me a replacement. So far so good. I also ended up buying an HK 23 bolt and sending it to Mike for machining as a spare. I've been feeding it Wolf only and alternating barrels every 200 rds or so (what good is a QC barrel gun if you only have one barrel?). Notwithstanding the bolt, mine has been running very very well. I think I probably put 2000 rounds through it at Big Sandy (got 2 airplanes with it- one at night) and haven't taken it apart to clean it yet. I like to run my guns dirty til they stop then clean them.

DaveT I'd be interested in a close up pic of your OOB that you had a Big Sandy. Especially the primer strike. I spoke to a good friend of mine and he had an idea that would tie all of your 'issues' together.

My buddy who ordered his 23e at the same time had more issues but I'll let him tell you about those...

 

[JTinIN]

Eyegun when did you receive your 23e?

I got mine Jan of 2012 or nominally the same time as Bob T.

 

[Travarmy]

I also ended up buying an HK 23 bolt and sending it to Mike for machining as a spare.

eyegun - question: Did you buy a 23 or 23E bolt? I assume you mean a 23E bolt. If so why would it need machined to work in a 23E gun? Would it not just drop in? Asking just so I understand how these beast work.

Travis

 

[JTinIN]

eyegun - question: Did you buy a 23 or 23E bolt? I assume you mean a 23E bolt. If so why would it need machined to work in a 23E gun? Would it not just drop in? Asking just so I understand how these beast work.

Travis

The story goest the HK21e has a pin in the barrel that mates with a shallow hole in the face of the bolt when the barrel is locked in (i.e. rotates to lock) and keeps the gun from firing with the barrel is unlocked (a good thing ;-). Mike kept the same concept in his MM23e on the 5.56 round, which HK did not (I am guessing the amount of danger to the shooter / B gunner is lower with the smaller round and/or was not required by the end buyer). Thus my understanding is you need to either remove the barrel pin or mill a dimple (shallow hole) in the face of the factory HK 23e bolt to use with the MM23e.

 

[Slingo]

The story goest the HK21e has a pin in the barrel that mates with a shallow hole in the face of the bolt when the barrel is locked in (i.e. rotates to lock) and keeps the gun from firing with the barrel is unlocked (a good thing ;-). Mike kept the same concept in his MM23e on the 5.56 round, which HK did not (I am guessing the amount of danger to the shooter / B gunner is lower with the smaller round and/or was not required by the end buyer). Thus my understanding is you need to either remove the barrel pin or mill a dimple (shallow hole) in the face of the factory HK 23e bolt to use with the MM23e.

Correct and a small amount had to be removed from the underside of the bolt for the trip..I had the same thing done to an extra German bolt ..The thing about using a german bolt is now I need the german rollers to head space .I see the price of them now..Bob T I fell your pain messing with the feed unit I sent it back 4 times .What was the pain was to drag the beast out to test and get nothing..I have 9K? down the pipe but so much was testing..Now I have a broken timed hammer.I think eyegun is right about not to cleaning them every time I do some other issue

 

[eyegun]

I got mine Jan 2012

Yes, I bought a 23e bolt. He machined a hole in the face of the bolt to accept the 'safety teat' (for lack of a better term) on the barrel. Also he milled a small groove along the bottom of the bolt to clear something else. The 23e bolts use rollers that are made of titanium and aren't round- they're cut like a half-moon shape. $250/set from Adam Webber, so when Otte chose the bolt head design he wisely chose to use standard widely available cheap round rollers. I don't think there's anything wrong with his bolt design just that heat treating can be spooky and it's not an exact science so once you get that dialed in you never change heat treaters or method. Heat treaters will tell you it's Rockwell XX but you never really are for sure until you test and/or break it.

Talking with NoHair he thinks the feed unit is too high- that would account for all the issues that DaveT is having, including the OOB at Big Sandy- this is something I can listen to and understand but I don't think I could explain it on my own. This would account for the spotty performance from similar vintage guns, as the height difference of only 0.01" is significant.

 

[eyegun]

Here's my pics of the broken bolt head:

 

[JTinIN]

I got mine Jan 2012

Yes, I bought a 23e bolt. He machined a hole in the face of the bolt to accept the 'safety teat' (for lack of a better term) on the barrel. Also he milled a small groove along the bottom of the bolt to clear something else. The 23e bolts use rollers that are made of titanium and aren't round- they're cut like a half-moon shape. $250/set from Adam Webber, so when Otte chose the bolt head design he wisely chose to use standard widely available cheap round rollers. I don't think there's anything wrong with his bolt design just that heat treating can be spooky and it's not an exact science so once you get that dialed in you never change heat treaters or method. Heat treaters will tell you it's Rockwell XX but you never really are for sure until you test and/or break it.

Talking with NoHair he thinks the feed unit is too high- that would account for all the issues that DaveT is having, including the OOB at Big Sandy- this is something I can listen to and understand but I don't think I could explain it on my own. This would account for the spotty performance from similar vintage guns, as the height difference of only 0.01" is significant.

Thanks for the information, had not realized the other differences between the factory HK23e bolt (i.e. rollers and milling the bottom slightly) thus my initial thoughts (not really an idea yet just thinking out loud) of removing or pulling the "safety teat" from the barrel would not have been sufficient. It does help to ask around.

I also got my MM23eK January 2012 and my bolt looked a lot like yours six weeks ago, along with the extractor parts falling out on the canvas when I cycled the bolt since would not full chamber a round or full extract the round in the chamber (was pretty clear why when I removed the bolt ;-). Mike sent another bolt and the gun was shooting fine last weekend. Several friends have had MM23e's for a couple years and are past ten to twenty thousand rounds.

 

[eyegun]

Here's a couple of pics of the different bolts.

Both pics are:

MM Modified HK / HK / MM23e

Notice there is a hole above the bolt face that the teat from the barrel goes into.

Second there is a groove milled on the underside of the bolt that goes from front to back.

Also notice the different rollers

Both HK's are new, MM23e 'used'.

 

[eyegun]

Posting these for Slingo as he is 'technologically challenged'....

Not necessarily in order:
#1: Broken bolt (again, I think it's just a heat treat issue and will work itself out in time).

#2 Issue with the 'feed teat' or whatever it's called. He sent the feed unit in once or twice

#3 Recoil spring guide rod roll pins walking out (I've seen this happen on at least 2 different guns).

#4 Most recent- broken retimed hammer.

Again, I don't think there's any inherent design flaws in the MM23e, just it's a very complex machine with a lot of moving parts and a ton of intricate details that aren't immediately apparent to the casual observer and are often discovered during manufacturing. I expect all of these issues will work themselves out in due time. It's a big project. Again, I'm very happy with mine and I like that Otte went with a bolt that uses standard el-cheapo round rollers.

Mine has run like a top and has only broken one bolt. I run my guns like bitches- don't clean them til they stop running. Mine is a champ. I had at least 2500 rounds through it last weekend at Big Sandy without cleaning and no malfs.

 

[mp40gunner]

Wish you the best on getting it worked out. I shot JT's and I see it run on a monthly basis and trust me, he is not shy about burning the belts up. Also have (2) other guys in the group that stand on theirs as well. If I had a sear I would be interested for sure.

 

[Bob T]

Update:

Received new buffer and "retimed" hammer from Mike (buffer had cracked, hammer broke in two).

Installed both and am now back up and running, hopefully it will stay together for more than the 100 test rounds I have fired so far.

When it works it is a joy to shoot!

 

[DINK]

I'm glad yours is running again. I got the repaired (or replaced) buffer back from Mike, but the gun is still stopping with the hammer forward on an unfired cartridge. I guess I'll be calling Mike after Thanksgiving.