Subscribe via RSS Feed

Choosing a Scope for Your HK91 or PTR91

Filed in Articles, HK, Optics by on November 10, 2011 8 Comments • views: 23562

So you want to put a scope on your HK91 or PTR91 (or other HK91 clone).

I am not an expert in riflescope optics. I don’t even play one on TV. (If you are looking for someone who seems to know his stuff about optics, go here.) I have learned quite a bit about scopes as they relate to the HK91 and the purpose of this article is to share what I’ve learned.

My own Personal Considerations

While 600 yard shots are not unrealistic for .308, my nearby range is more limited.  While a few lanes allow 250 yards, most are 200 yards. As a result 250 yards is the practical maximum range I’ll be shooting at. During the summer when it’s really hot outside (I live in Phoenix, AZ) I shoot at an indoor range that is just 25 yards. As a result, I need a scope that will handle 25-250 yards.

Some people advocate the option of no magnification (1x power) for close-in stuff, claiming that you can acquire the target and get the shot off much faster.  I don’t see myself ever ivolved in that sort of situation.  My soldier-son has a Trijicon ACOG which is 4 power.  I’ve shot it at 25 yard targets and while 4X seemed a tiny bit of overkill, it worked just fine.  So I’m looking for a scope that has a low-end magnification in the 1x – 4x range.

There are several really nice 1-4X scopes that I like:

  • Leatherwood CMR
  • Nikon M223
  • Burris Xtreme Tactical

If my eyes were younger, 4x magnification might be sufficient at 250 yards.  For me, at my age, it is not. As a result, my first choice is a 3-9x scope.

Lesson 1: The Forward End Of The Scope Must Clear the Cocking Handle

HK91 PTR91 ScopeHere is the first scope I bought, mounted on my PTR91.  Three nanoseconds after mounting it, I noticed the cocking lever as if it was the first time I’d ever seen it.  I thought, “Gee, I didn’t think about that.”  IMHO, you want at least a half an inch between the front of the scope and the cocking handle.





HK91 PTR91 Scope

Lesson 2: The back of the scope must provide sufficient eye relief.

Grab your rifle, get into your normal shooting position, and take note of where your eyeball is in relation to the stock. With no scope on the rifle, my eyeball is alligned with the arrow in the adjacent photo. When the scope ON the rifle. you can see that the scope is too long.

Eye Relief

If you’ve never used a scope before, the let me introduce you to eye relief.  Eye Relief is the distance your eye must be from the rear of the scope in order to get the full field of view. In addition, if your eye is too close to the scope, it will smack you in the forehead when the gun is fired. A semi-circular cut in the middle of the forehead is a sure sign that the shooter was too close to the scope. As you can see by the accompanying photo, there is ZERO eye relief with this scope mounted on my PTR91.

Scope Length + Cocking Handle Clearance + Eye Relief

Measure the distance from the cocking handle to the spot on the stock aligned with where your eye would be. That distance MUST be greater than the sum of:

  • Scope length
  • Clearance for the cocking handle (at least .5 inch)
  • The scope’s Eye Relief

I found that distance to be 15 inches for me.  Subtract a half inch for cocking handle clearance and the result is that the length of the scope plus the scope’s eye relief must be no greater than 14.5 inches.

Time to Start Shopping

I quickly found that while there were several 1-4x scopes that would fit, there were no decent 3-9x scopes short enough to meet this requirement. Bummer. That meant that I would have to settle for a 1-4x scope.  Or would it?  Suppose I could add a little length to the stock?

Stock extension

The folks at E&L Manufacturing make this stock extension designed specifically for the HK91. It is adjustable and can be configured to add .5, 1, or 1.5 inches to the length of the stock. I’ve put one on my JLD PTR91 and it works well.  It’s very sturdy.

With the 1.5-inch stock extension in place, the 14.5-inch max dimension now becomes 16 inches. I now have a lot of options for scope.

There is no shortage of 3-9x scope choices. Some things I’ve learned about low-cost scopes:

  • In the sub-$100 price range, a scope should be expected to do one thing and one thing only: hold zero.
  • When reticle illumination is offered on a low-cost scope it is usually poorly executed.
  • As Ilya Koshkin says on Optics Thoughts, life is too short to be using a Barska/Leapers/BSA/NC Star etc. I’ve read enough poor reviews to confirm this.

Vortex Diamondback 3-9×40

HK91 PTR91 Scope

Vortex Diamondback 3-9×40

In the end, I chose the Vortex Diamondback 3-9×40 with the Dead-Hold Bullet Drop Compensator (BDC) reticle ($199).


  • It is the shortest (11.6 inches) 3-9x scope of decent quality.
  • Ilya Koshkin of Optics Thoughts gives it high praise, particular for image quality, field of view, and low-light performance.
  • Came up as the best scope in this side-by-side comparison with other similar scopes.
  • A search of the ‘net for comments and reviews reveals a lot of praise and almost no criticisms.

Click Here to Read About:
Mounting a Scope On Your HK91 or PTR91

Comments (8)

Trackback URL | Comments RSS Feed

  1. Earl Paige says:

    What rings did you use?

  2. John Minker says:

    Thank you for providing this information. I plan to model this setup exactly. Can you please tell me which scope mount you ended up with? Potentially the make and model, as well as which version of the Burris Signature Rings? I suspect the low ones, right?

    • Dave Barnhart says:

      I used a .5 inch picatinny rail riser. I mounted the Burris Signature Rings on that. The rings are the High Signature Zee rings, number 420530.

  3. John Minker says:


    Thanks so much for the info. I have found the rings for sale here;

    Would it be possible to identify, perhaps a link to the rail riser for me?

    Thanks Again!!

  4. Mirage says:

    I have an MFI low profile rail with medium TPS rings mounting a Luepold VX3 4.5-14x40mm LR (No.: 11520) Scope… Excellent combo in my opinion… Clears charging handle easily, Good eye relief, and never any scope eye…

  5. caveman says:

    Get the scope mount made for that rifle, “claw mount” you will have no issues with the cocking handle at all. Purchase a great scope. not some junk that every time you move it or bump it it goes off zero like Tasco. Get a Zeiss or as good, you want to hit what you aim at. Go to HKparts to get what you need. I have been firing HK all my life, If you get HK get HK parts and accessories.

  6. Lance says:

    I’m shopping for a scope for my PTR right now. I’m leaning towards the Vortex Viper PST series.

    Ps. The ACOG is designed to be shot at close distance with the Bindon Aiming Concept, making the magnification irrelevant when both eyes are open.

Leave a Reply

Your email address will not be published. Required fields are marked *