Mounting A Crossbow Sight, Cantilever Style

When an elderly hunter showed up at my shop with an older PSE 150pount crossbow, he wanted to know if it was possible to have a scope mounted on it. He had an older Weaver V-4.5 scope with tipoff mount purchased at a garage sale and this must have given him the idea to have it mounted on his crossbow. Before contacting me, he had approached three other gunsmiths and they all refused the job. As we examined the older, very well made, PSE crossbow together, I could see why the others turned the job down.

The old crossbow had integral open sights with no place for a scope base. Yet, with eager expression he beckoned, "Do you think you could do it?" I did see a ray of hope in mounting a scope when I realized that I could cut off the open sights and mill the top of the very rigid cocking mechanism parallel to the main beam of the bow.

I would need to fabricate a double angled bracket that would The customer’s older Weaver V-4.5 scope is shown here with Redfield scope base and rings. bridge this surface and be anchored downward to a fl at, rigid surface on the rear of the receiver. I cut a narrow piece of stiff paper to show him approximately what such apart would look like as it would serve as an interface where the open sight would be cut off and anew scope There was no place for a scope mount on this older crossbow.

base attached to it. There would be no turning back once I started and his open sights would be history. He said, "If you think you can do it, go for it." Whereupon the job was in my hands. Cantilever Scope Bracket As mentioned, making a precisionfit cantilever bracket would be the key to attaching a scope base on this crossbow. I used a length of 1/4 x 1inch hot-rolled steel for the job. With a template of formable, stiff fabric, the proper bend points were marked.

The angles were formed by making a deep "V" in the metal and heat bending them. Silver solder was used to fi ll the cracks to retain the stiffness of the part. The attachment holes at the receiver base were marked first with the cantilever in place over the fl at surface of the cocking mechanism. This shelf-like projection is very solid as an integral part of the trigger and sear assembly. At the rear receiver base I drilled and tapped for two 10-24 countersunk screws. At the top I countersunk two 8-40 screws.

Checking the parallel of the top of the cantilever with the main crossbow beam showed good alignment. The next step was fitting a one-piece scope base to the top surface of the cantilever bracket. I chose a Redfield Jr. dovetail base because it fit the hole pattern of the cantilever surface. The Redfield base required milling to achieve proper parallel alignment with the main beam. The scope base was then attached to the cantilever bracket using four of Brownells 8-40 screws from their Tactical Scope Mounting Kit.

I installed one additional screw at the junction of the windage screws for a most solid application. A check of the parallels proved out perfectly. It appeared to be all systems go. The sear is shown in the slot used to anchor the drawn bowstring. At this stage there was a short interruption. This involved making and fitting a lug at the rear vertical leg of the cantilever bracket. This lug would form the anchor for the Rope Cocking Aid, which I anticipated a need for in cocking the bow.

While the 74-year old hunter who owns this bow could cock it, he found the procedure increasingly difficult and I couldn’t foresee him doing it for very long at his age. I also made a special rope cocking aid which reduces pull weight by 50%. I will cover this project in a separate article. Mounting and Sighting As a package, the customer wanted his older Weaver V-4.5 scope used

Two additional screws were used in this application. on this job. It turned out to be a good choice being short and compact with a small objective lens that wouldn’t interfere with the bowstring or arrow fl etching in any way. I chose to use Redfield Jr. low rings, which worked out perfectly in viewing through the scope. Eye relief was perfect as the cheek makes contact with the stock. The old scope was equipped with a Perma-Center reticle, which was also quite appropriate.

Some of the older Weavers didn’t have this feature. Test Firing and Sighting-in If you’ve done your homework, sighting-in with an optic is an easy task. One of the worst case scenarios is to discover a scope runs out of windage or elevation adjustment. The Weaver scope was near perfect in this area and almost center of adjustment with the new cantilever system. I sight my crossbows for 25-yard zero and make allowance for shots greater or lesser than this range.

All too many hunters using a crossbow believe the arrow shoots with a flatter trajectory than it does. For example, the 150-lb. peak weight PSE crossbow trajectory as zeroed with a 488 grain broadhead-tipped bolt at 25-yards is as follows: 14 yards/+ 4 ½"; 25 yards/0"; 30 yards/-6"; 35 yards/-12"; 40 yards/-21". Taking shots beyond 40 yards by the lesser experienced crossbow hunter is not be recommended. The PSE crossbow shot very well with the simple plastic V-shaped front arrow rest and a nocked bolt.

Most modern-day crossbows have a channel to guide the bolt/arrow as it moves down the beam. Bolts are not nocked on the string as they are pushed straight down the channel. Conclusion All the thought and effort put into this very different scope mounting system worked out well. In some circumstances, making money is not the entire issue.

I knew, as I made a tentative quote, that more time would be involved in mounting the crossbow scope but seeing a happy customer and a job turn out better than expected has always been rewarding to me. AG