Today Doug Wall conducts some initial testing with his regulated Gen. 1 Barra 1100z in .177 Caliber. This follows-on from the regulator installation in the previous part of this series.
Background
In this article, we’ll explore the performance of my newly-regulated, 0.177 gun. The reg. was set to about 1,700 PSI, so I’ll be doing tests to see what kind of velocity I get. With different hammer spring settings, I’m expecting to see some differences in air usage.
Based on what I was seeing as I was installing the regulator, there may be some hammer free flight below about 5 turns in, which should increase shot count.
When I started doing the testing, I noticed that the velocity has crept down a bit. The testing right after installing the regulator gave me about 950 FPS, and 19 Ft/Lbs. Now it’s giving me about 930 FPS (16 Ft/Lbs). I’m guessing that the seals in the regulator may have settled a bit, so I’ll adjust the pressure upwards a little bit.
To adjust the pressure, degas the gun, open up the end cap, and reach down to adjust the regulator with the long regulator tool that I made, or a very long screwdriver.
I adjusted the pressure to about 1,900 PSI, and the velocity is back into the 950 FPS region that I was looking for.
Regulated Barra 1100z Testing
These test will all start with a full, 3000 PSI fill and run down to 1,400 PSI – as observed on the built-in pressure gauge. The pellets will be the same H&N Baracuda 8 (8.44 gr) that were used for the other tests in the 0.177 configuration.
The first series is with the hammer spring turned in 4 turns from the flush position. From the graph below, you can see that the velocity starts to drop off after shot 38. Meanwhile the pressure dropped below the 1,900 PSI set point, to about 1,700 PSI.
The total energy for this series was 648.96 Ft/Lbs across all 38 shots. (Shame about that high first shot!). The average of the 37 consistent shots was 17.10 Ft/Lbs.
For the second series of tests, the hammer spring was turned-in 5 turns from the flush position. From this graph, you can see the velocity and pressure dropping off from shot 32. The total energy for this series was 650.49 Ft/Lbs. The average of the 31 consistent shots was 16.93 Ft/Lbs.
The third series is with the hammer spring turned in 6 turns from the flush position. Now the velocity and pressure start to drop off after 27 shots. The total energy for this series was 565.53 FPS. The average of the 27 consistent shots was 16.84 Ft/Lbs.
Here’s a summary, combining all the graphs together.
Regulated Barra 1100z Testing – Conclusions
We can see from this short set of tests, that regulated does not mean optimized! The 4 turns in position for the hammer spring gave 40% more shots than the 6 turns in position! The total energy varies as well.
This type of change in a regulated gun is pretty indicative of air wastage. That may be from hammer bounce. In an unregulated gun, the hammer spring tension settings will also affect the velocity, up to a certain point, as we saw in previous tests.
In the next part of this series, I will change the hammer from a Gen 1 hammer, to a Gen 2 hammer. Barra has informed me that the Gen 2 hammer has some features to minimize or eliminate hammer bounce, which could be the real key to a lot of performance issues.
Stay tuned for part 6!
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Barra 1100z Air Rifle
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