Posted: 4/4/2017 1
31 AM EDT
I've started a few threads in the various forums discussing our experiences with high-volume shooting on our range. We are now approaching, if not surpassing, 860,000 rounds per month We only use our ammo with our weapons as customers cannot bring their own weapons onto our range. We have provided this information to several state and Federal agencies as a form of "test and evaluation" on extended use and our results. That being said, I can provide you with a little insight into what our experience with HK's and HK clones. From this point forward, I will refer to all weapons as HK unless I am providing detail on a certain clone brand/mfg.
The most often used HK at our range is the MP5 followed by MP5K, then the MP5-SD, UMP-45/49 and finally the G3 (or semi the semi HK91 variant). The number one thing I can say about keeping the HK platform reliable is changing recoil and extractor springs. On our MP5's, we change extractor springs every 2-3 days. We've used the MP5-specific copper spring, the stronger steel G3 spring and aftermarket black extractor springs and they all give us about 2-3 days of hard use. We will bend them once before replacing but that's about as good as it gets for us. With the volume of ammunition we are putting down range, there has been no way around it.
The recoil spring is a completely different beast. By not changing it often enough, you will eventually destroy your receiver. The problem with the recoil spring is that it's right in front of your face but it rarely got changed up until recently. We now have a PC in the armory so the armorers can leave reminders to change springs out after three months. We've lost MP5 and G3/HK91 receivers because not changing the recoil springs. The receiver will start to bulge where the bolt carrier bottoms out at the stock. The weak recoil spring allows the bolt to come back with so much force that the rollers eventually to put reverse dimples/bulges on both side of the receiver. If not caught soon enough, the roller will eventually just start getting caught in those dimples and the bolt carrier will stay stuck to the rear. The other issue that occurs is the receiver will crack where the rear stock pins attach. Both issues are caused by the bolt carrier group slamming back so hard that the sheet metal eventually gives. We just recently lost a PTR-91 due to a VERY weak recoil spring that cause the rear of the receiver to crack. This rifle was never run full-auto but is shot daily because it's in one of our more popular packages (sniper package). I did have an original HK SR9 on the line but after five or six months of range use, the factory SR9 stock cracked. At that point I pulled the rifle from the line as it was one of my personal rifles. I never meant to keep it on the line and used it to see how well the package would do.
We keep (+) size rollers to keep the weapons running as the bolt gap slowly fades away. We have a decent inventory and pull and replace as needed. It's a simple fix for the HK platform but once they no longer work, it's time to push the barrel out and replace it. Once a new barrel is installed, you can grab your original rollers and set the bolt gap to those spec's and use them all over again. When replacing the barrel, we've always replaced our locking pieces. I don't know the proper terminology for it, but the angles that allow the bolt and rollers to lock up and go into battery, eventually wear away and won't provide a proper bolt gap. Replacing barrels isn't the easiest task and so I asked Tony Dee from the Gun Store (who has decades of experience on MP5's) to train my guys on when to replace the barrel and went to take it a step further.
We had approximately twenty MP5's that were down due to continued cycling issues. Tony explained to us that since some of our weapons were in the 400,000-500,000 round count, we needed to swap out the trunions. He showed us exactly why we were experiencing so many issues and all the (+) size rollers and new barrels wouldn't correct the problem. I had the staff do complete rebuilds on approximately fifteen of our MP5's. New trunions, barrels, bolt carrier groups, cocking tubes and recoil springs were ordered. After all of the time spend on doing the rebuild program, we've concluded that it's best to just demil or scrap the MP5's and start with new units. The issues we had were not limited to one brand but spread across all of the various manufacturers.
So, this leads to our experiences with all the different manufactures. We have used the following brands on our range: HK, Cohaire, PTR, Century (the HK-53 clone and CETME Sporter), POF, MKE, Special Weapons, Zenith and the Atlantic Firearms variants. Not one of these brands has really outlasted the other. Only one time did we receive a batch of POF's that we had problems with from day one. The rollers must not have been heat-treated properly because all of the rollers cracked within the first week of use. Once we replaced the rollers, the weapons went on to function for thousands upon thousands of rounds. The only model we never used were the cast receivers from Special Weapons or Cohaire, I don't remember who made them. We do have some Special Weapons stamped receivers that are over ten years old but they are finally being retired. ALL of the receivers eventually cracked where the receiver pinches the trunion and we welded them back up. I never considered this a safety or liability issue and they remained on the line.
We pulled thirty plus MP5's this past weekend and will start the demil process. Some of the receivers that were not converted to full-auto will be sold to staff members but they will get the whole firearm for $200 and these include the some of the receivers that just went through the full rebuild. I felt that the receivers were all in such different conditions and age that it would be better to start fresh at this point. We purchased thirty standard Omega MP5's, five Omega MP5K's and five Omega MP5-SD's and five PTR-91's.
I also want to mention the various types of magazines we on the range. We use POF, MKE, the Taiwan-made magazines with parkerized finish and chrome follower as well some HK factory mags mixed in. They all seem to function about the same but the HK factory units do last the longest. The biggest problem with them is weak springs that cause malfunctions. These magazines can get loaded 50-60 times a day and the springs don't last forever. We used to replace the springs with Wolff extra power springs but at this point, it's cheaper and more efficient to just replace the magazine.
I know there are quite a few things that I skipped right over so if I didn't bring it up, please ask me and I will try to answer the best I can. It's been a long day and I didn't mention anything about the various brands of parts we use or how often we replace other parts, which parts fail (other than springs), etc. As with the other threads, I started this thread for all the people are thinking about taking the plunge and purchasing a HK platform. It's not the cheapest platform out there but it's simple and reliable design with SO many choices for replacment parts that they really are a good purchase.
eta: Just like before, please forgive any typo's. I already have problems writing things as I hear them in my head but I am beat