Doug Rogers’ BSA R-10 Tune Doubles The Shot Count

The graph below shows the comparison between the gun as tested by HAM (blue diamonds) and after Doug’s BSA R-10 Tune (red disks). As you can see, Doug’s tune both flattened-out the shot curve and doubled the number of consistent shots per fill.

BSA R-10 Tune Doubles The Shot Count

WOW!!! That’s an outstanding result and it’s easy to do! Here’s the full story…

BSA R-10 Tune Background

In the recent Hard Air Magazine test review of the BSA R-10 SE, the test gun performed to the manufacturer’s claims. It earned a HAM Gold Award with a score of 93%. However HAM Tester Doug Rogers and myself both felt that it had more to give. Somehow…


In fact, Doug liked the review gun so much that he was thinking of buying it for himself. (HAM always sends back review guns, we don’t keep them unless specifically requested by the supplier).

Of course, it’s the greatest possible recommendation when the reviewer actually wants to buy a product. And don’t forget that Doug has tested a ton of high-end PCPs. He’s not easily impressed.

So Doug and I had a conversation. Here’s how it went:

Steve: Doug, I know you love that R-10 SE, but we have to send it back to AoA now.

Doug: Yeah I know, but I’d like to buy it. At least, I would if the performance were just a little better.

Steve: Well, it’s pretty clear from the HAM review’s shootdown curve that the hammer spring tension is set too high from the factory. AoA said that we could look inside if we want. I think that – if you could reduce hammer spring tension – it would make an improvement. What are you aiming for? More shots per fill or more power?

Doug: Both, of course!

Steve: OK, good luck with that. I’m off on vacation…

BSA R-10 Tune Test Methodology

So Doug set to work. The HAM test review shutdown curve gave him some base data to use. As you can see, there were just 28 consistent shots. Let’s be generous and say 30! This was followed by a big spike in FPS before the regulator set point was reached at around shot 40.

The HAM test shutdown curve was produced using 15.89 Grain H&N Baracuda 15 pellets (graph above). As Doug proposed to shoot 18.13 Grain JSB Exact Jumbo Heavy pellets in “his” R-10 SE, he first shot an initial 10-shot string with these JSBs. This gave him a new factory settings reference to work from.

Following that, Doug opened-up the R-10. It was very simple. After the normal safety checks – clear and de-gas the gun – he carefully removed the stock. (Gotta look after that beautiful wood!)

Doug Rogers’ BSA R-10 Tune Doubles The Shot Count

Finger pressure alone was required to unscrew the cap in the back of the action, giving access to the hammer spring adjuster.

Doug Rogers’ BSA R-10 Tune Doubles The Shot Count

Doug’s next finding was that the hammer spring adjuster had been cranked FULL IN at the factory. So maximum hammer spring tension was already being applied. There was only one way to go. Back out!

WARNING: Note that the hammer spring adjuster uses a very fine thread. Doug advises extreme caution before and when making any rotation, especially as the adjuster on this gun had been screwed-in BEYOND the threads and needed to be very carefully re-engaged. HAM takes no responsibility for cross-threading problems should you elect to do this!

Doug Rogers’ BSA R-10 Tune Doubles The Shot Count

The hammer spring adjuster required the use of a very wide slot-head screwdriver to adjust. Fortunately he had one to hand.

Doug Rogers’ BSA R-10 Tune Doubles The Shot Count

Next Doug screwed-out the hammer spring adjuster by two complete (360 degree) turns. Then he put the stock back on and fired a 20-shot string across the chronograph.

This process was repeated but with a change of just one complete turn between each string. Doug continued until the hammer spring adjuster was backed-out seven turns from the factory (full in) setting.

Doug analyzed the Chrony printouts to decide on the best settings for his BSA R-10 tune. Then he re-set the adjuster to that point – five turns out – and fired a complete string.

Oh, of course the HPA bottle was refilled before each string. The 18.13 Grain JSB Exact Jumbo Heavy pellets all came from the same tin and Doug shot at a consistent, slow, rate in his indoor range for strict “apples to apples” data.

Let’s take a look at what he found….

BSA R-10 Tune Results And Analysis

Here’s the first, 10-shot, string using the JSBs at factory settings. Just for reference.


Next, Doug backed-off the hammer spring adjuster by two turns and shot the first 20-shot string.


Now for three turns out. The first shot was fast, but the angle of the curve is flattening.


Four turns out showed a fast first shot, plus a slow second shot. Plus, there was an unexpected surprise at shot 16.


Now five turns out. The first two shots are slow. Plus, this time there’s another pesky slow shot at shot 17. But it’s clear that the shot curve has now really flattened out with multiple shots at around 850 FPS.


Backing-out six turns and things really went wild!!! Now we see consecutive fast and slow shots with a spread of 40 – 50 FPS between them. What’s causing this? We have no idea!


Just for grins, Doug then went to seven turns out on the hammer spring. Hmmm, there’s that pattern again.


Taking account of all this test data, Doug tightened back up to five turns out on the hammer spring adjuster and made 60 shots. That’s shown in the graph below.

As you can see, he has completely smoothed-out the shot curve and it’s clear that shot 60 represents about the end of the consistent shots. Doug has doubled the shot count per fill!

BSA R-10 Tune Doubles The Shot Count

The average Muzzle Energy is now 29.22 Ft/Lbs and would be higher if it weren’t for those pesky two slow shots. That compares to 25.59 Ft/Lbs in the HAM test in factory configuration.

BSA R-10 Tune Conclusions

Doug’s tune gives an increase of 14% in power – as he wanted. Yes it’s fair to say that some of that increase is due to shooting heavier pellets. But it’s still more power at around the same Muzzle Velocity!

If you take this average Muzzle Energy and multiply it by the number of consistent shots, the total Muzzle Energy is 1,753.2 Ft/Lbs for Doug’s tune. Making the same calculation for the same gun in factory tune in the HAM test review, the value is 767.7 Ft/Lbs. That’s an increase of 228%!!!

BSA R-10 Tune Doubles The Shot Count

So Doug achieved his goal of more power and more – make that a lot more – consistent shots. But there’s still the issue of the slow shots that begin at random with the hammer spring adjuster four turns out.

Doug’s next step will be to try to understand and fix that phenomenon. It’s a reminder that there’s always something to learn with airguns for all of us! But he’s already delighted with the results.

Suggestions are welcomed in the HAM Community!

“Your mileage may vary”, of course, should you try this. But I think Doug may be buying this BSA R-10 SE after all…

BSA R10 SE Walnut HP Thumbhole