For this project I’m basically converting a stock PTR91 into an HK PSG1 look alike or clone. I’d like to get this gun as close as possible cosmetically and then, eventually upgrade to the real PSG1 bolt and trigger group.
- Receiver modifications
- PSG1 26″ barrel
- Trunnion extension
- Cocking tube and PSG1 for grip
- Receiver side stiffening rails
- Forward assist
- HK PSG1 stock and grip
- PSG1 scope
- Clone PSG1 tripod
The PTR 91 receiver is actually built quite well. This is one of the closest to HK spec receivers you can buy. There are some differences though between the HK 91 clone and the PSG1 receiver so I will outline the changes in this section.
I will be removing the rear site and site base. I’ll need to grind and file to remove the welds and smooth it out so it looks like it never had a rear site base at all.
I will need to mill a set of “L” brackets that will be welded to the top of the receiver to mount the scope. I will post measurements, drawings and pics soon.
The barrel trunnion on a PSG1 is almost twice as long as the normal HK91 trunnion so I will either need to replace the trunnion with a longer one or make/buy an extension for the stock trunnion and weld it on. The extension helps give the extra long barrel additional support and acts as a support for the rear section of the PSG1 for grip. With no extension the PSG1 for grip will not fit tight or stay in place on the gun. The plan as of now, is to make a trunnion extension on a lathe and weld it to the existing stock PTR trunnion. This way it will be cut exactly for my barrel. I will post more measurements, drawings and pics soon.
A set of steel side stiffening rails will be milled to fit the PTR receiver. I didn’t have a set of originals or after market rails so I made measurements from pictures and scaling from my PTR. It may not be 100% exactly the same as the HK parts but it will be close and it should look good! Either way it will still look like a PSG1 and they will get the job done just fine. I will post measurements, drawings and pics soon.
The PSG1 and MSG90 also have a forward assist mechanism where as the 91 does not. These little units are a bit expensive for what they are so I’m planning to fabricate this as well. I don’t have 1 on hand to take measurements from so it will be a custom “guess job”. I may try to use an ar15 forward assist plunger for parts. Also the bolt carrier will need to have the forward assist notches milled into it. The other option is to buy a MSG90 or PSG1 bolt carrier with the notches in it already. I will post measurements, drawings and pics soon.
Original HK PSG1 Stock and Grips
There are some replica parts available for the 91 and clones that are similar to the PSG1 parts but none of them are exactly the same. I wanted the real PSG1 look so I went with the real PSG1 stock and buffer, real PSG1 wooden hand grip, palm rest and the real PSG1 for grip. As expected the parts fit and look great. The PSG1 stock has a different buffer in it as well that help to additionally reduce felt recoil. All of there parts were purchased used and cost me more than the gun itself!
I will post pics soon.
Cocking Tube Mods
The cocking tube on the PSG1 is different than the 91 mainly, in that the end does not taper and there is no iron sight. Also the for grip pin loop is eliminated. For this modification I will need to make an end cap tube with a slot in it for the quick detach latch on the PSG1 for grip. It will be welded to the end of the existing cocking tube after the tapered extension is cut off. once this is dome the grip should fit on and snap into place. The Barrel trunnion extension will also need to be in place for the grip to stay tight. I will post more measurements, drawings and pics soon.
Originally I was going to make an extension for the existing 18″ PTR stock barrel but came across a great deal on a 26″ heavy PSG1 barrel clone. Its never been used and it will need to be pressed and head spaced/bolt gapped in my PTR receiver. This was a great find and I’m very exited to see how this barrel compares to the stock 18″ PTR91 barrel.
I will post pics soon.
HK PSG1 Tripod Clone
HK made a snap-together tripod for the PSG1 that came standard with the gun. They are rare to find for sale alone and expensive if you can find one. I plan to make a similar tripod out of aluminum for my clone. It will work similarly to the real one but may be slightly different for an easier build. I will post measurements, drawings and pics soon.