Today we’re looking at some simple PCP improvements that the enthusiastic airgun owner can try themselves. They’re cheap and easy to do, too…
Our subject is the Diana Skyhawk that we recently reviewed, however many of them could be applied to other PCP air rifles, too.
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Diana Air Rifle Skyhawk PCP Air Rifle, Walnut 0.177
That Skyhawk gun performed very well, earning a HAM Gold Award with a score of 91%. I liked it a lot. But somehow I thought that it could benefit from a little love and attention – the sort that an average enthusiastic owner could provide.
Please note that the aim here is NOT to strip and rebuild the gun. This is emphatically NOT a “professional” upgrade, but simply some “average Joe” changes that can be made within the limitations of the Owner’s Manual and thus not offending against the manufacturer’s warranty.
These simple improvements made a very significant improvements to what was already a very nice air rifle. Also they were enjoyable to do. Hey, what could be wrong with that?
Simple PCP Improvements – Adding A Handstop
One simple, practical way to improve everyday shooting accuracy with any gun is to hold it consistently.
The proliferation of M-LOK slots on many recent air rifles gives us an easy and effective way to to do this. Here’s what we see for the Skyhawk…
I did this with “our” Skyhawk and experienced the difference when shooting straightaway. Now my hand had a set position to push against. It was comfortable and predictable!
I used a Leapers UTG M-Lok UltraSlim Handstop. Mine happened to be in a red anodized finish. But it’s currently available in both black and blue versions for less than 20 Bucks. Recommended!
Simple PCP Improvements – Adjust The Trigger
In Hard Air Magazine reviews, we always test with the trigger “as received”. Just as the gun is shipped to us (or would be to you). But almost all PCP air rifle triggers have an adjustment capability and the Owner’s Manual tells you what to do.
As mentioned in the review, our Skyhaw’s trigger averaged a pull weight of 3 Lbs 15.2 Oz. Most owners would probably prefer a somewhat lighter trigger pull weight. I felt that somewhere around 3 Lbs 0 Oz would be reasonable to aim for.
As the actual sear release was OK, my aim was not to mess with the sear engagement, if possible.
Now the Skyhawk is a bullpup. This means that the trigger has a two-part configuration with the actual trigger blade being remote from the sear assembly. The two parts are joined by a long rod.
The Owner’s Manual gives some instructions. After removing the stock, it’s possible to adjust the sear engagement and/or first stage weight.
As I wanted to lighten the trigger pull weight a little, I decided to follow the “First Stage Weight” instructions.
Removing the stock gave an immediate indication of why the trigger was heavy. Look at that first stage weight adjustment spring!
Before making any adjustments, I made a small, self-adhesive ruler from metric graph paper and taped it to the HPA tube next to the first stage adjustment spring stop block. I then measured the position of that block before changing anything.
The distance from one end of the spring to the other was 9.0 mm, as you can see below.
In addition, I recorded ten trigger pull weights generated during HAM review testing. We use a trusty Lyman Digital Trigger Pull Gauge. This provided a baseline against which to compare our changes.
To adjust the Skyhawk’s pull length, the brass stop block’s setscrew is loosened and the block moved along the trigger connecting rod. Like this…
As with ANY TRIGGER ADJUSTMENTS, it’s vital to make ONE SMALL CHANGE only and measure the result before proceeding further.
So, my first adjustment was to increase the spring length from 9.0 mm to 11.5 mm. Why 11.5 mm? It was just a guess based on how the spring looked…
Although I had been planning to make multiple adjustments, I was pleased – and surprised – to find that this single adjustment reduced the Skyhawk’s trigger pull weight from an average of 3 Lbs 14.7 Oz to 3 Lbs 1.9 Oz.
That was close enough to my aim of a 3 Lb trigger pull weight. Plus the first stage travel now felt much longer and the second stage engagement considerably easier to discern. That was a big improvement!
Testing confirmed that the sear engagement still felt good, the safety still worked and that this adjustment had not made the gun unsafe. Banging the buttpad on the ground (with the gun unloaded, of course!), did not cause it to fire.
While the details of this trigger adjustment are specific to the Skyhawk, the general principals apply to adjusting ANY trigger.
First read the manual (RTFM!). Then decide what you want to achieve. Conduct baseline tests, record the data, make one careful small adjustment, test again, compare the data and don’t make more changes than necessary. Testing for safety is paramount!
Simple PCP Improvements – Stock Improvements
The third simple improvement was to improve the stock. Careful inspection revealed that the stock has some sort of oil finish applied at the factory. Now I’m not a woodworker, but I was hopeful that this could be improved with a gentle application of light mineral oil.
Applying with a cotton patch, I tested a small section of the stock. The result was clear to the eye, even if not so much to the camera!
So, the buttpad and front M-LOK rail were removed, the stock external surfaces wiped all over with the oil and left to dry.
Before re-assembly, I made a spacer from a thin sheet of white plastic. Located between the stock and buttpad, the spacer gives a pleasant effect, I feel. And note how well the wood grain shows now after the oil wipe-over!
As a bonus, this treatment also repaired a couple of small “rubbing marks” that had been inflicted on the stock during shipment. You can see one of them in our photograph of the trigger above (the light patch on the wood in the left of the photograph).
Simple PCP Improvements – Lubrication
The final improvement was the one that required the most thought but actually gave the least result!
As with most Chinese-manufactured PCP air rifles, the Skyhawk was assembled almost completely “dry”. With the exception of some silicone oil on O rings and (maybe) a little grease on the bolt, all other metal-to-metal surfaces have no lubricant at all.
The result certainly works, however there’s that slightly rough feeling that’s crying out for a little love. Particularly the Skyhawk which has more mechanical parts due to the bullpup design. But what to do?
A survey of PCP Owner’s Manuals gave little guidance. Some include no recommendations for lubrication (including Diana). Some recommend using mineral oil, others silicone oil. Some say to use moly paste on the bolt.
But there’s general agreement that too much lubricant is bad and that in no case should this be introduced into the barrel or applied to the hammer. I agree with that.
The other important thing is that ANY petroleum-based lubricant is absolutely NOT to be used due to the risk of explosion at the high pressures used in PCP airguns, plus potential damage to rubber O rings. So, WD40 and many other common lubricants are out.
The course of perfection would be to dismantle the Skyhawk completely and re-assemble with a smear of moly grease on each pivot pin and sliding surface. But we’re looking for an “Average Joe” solution here…
The obvious thought was to apply a drop or two of oil on these pins and surfaces. But silicone oil is not generally recommended for metal-on-metal use (despite the recommendation in some Owner’s Manuals). I wasn’t too keen on the mineral oil idea either. And any oil can attract dirt.
So, I decided to use some moly paste on the bolt. For pivot pins and inaccessible areas, the plan was to use dry graphite lubricant.
Having enough moly paste in stock to last multiple lifetimes, I headed to Home Depot and purchased a small plastic dispenser of dry graphite dry lubricant. It’s sold as being for use with locks.
The tube applicator offered the promise of being able to apply small amounts in a specific location.
So that’s what I did!
I smeared a tiny amount of moly paste to accessible areas of the bolt. Other pivot pins and sliding surfaces were given a light puff of the dry graphite, with any excess wiped off. Some dry firing was then undertaken to help the graphite reach the locations where it was wanted.
Did it work? Well, yes. There’s actually no measurable reduction in cocking effort, for example. But the gun does feel smoother and pleasurable to operate.
So that’s a summary of some cheap, simple PCP improvements that can be applied to your air rifle without invalidating that all-important warranty. I feel that our Skyhawk looks, feels and shoots even better for this effort, plus I enjoyed doing it!
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Diana Air Rifle Skyhawk PCP Air Rifle, Walnut 0.177
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