Recently found myself desiring a ‘powerful’ bullpup style .177. Looking around, I found I liked the look of the new P35X. Not too much info on this gun that isn’t limited to 12 fpe or translating. I am no stranger to the Snowpeak (and progeny) ‘barrel lottery.’ I just tell myself, fine, if it stinks I’ll re-barrel it. With the 65cc plenum and longer runway (~530 mm) I hoped to get 30 to 32 fpe. In artillery, barrels are sometimes listed as multiples of the caliber, making this a .177/118 where the .22 variant would be about .22/96. Why bring this up? Caliber relative to barrel length. My armchair calculations suggested that I could be getting around 30 fpe without a lot of pressure.
Back when dinosaurs roamed the earth, and springers were top shelf aspirations while MSPs were the norm, very strong performance in .177 was about 16 fpe. Even today springers exceeding 20 fpe in .177 are pretty uncommon. At the expected performance of about 30 fpe we’ll probably be looking for slugs in order to perform well. Maybe some of the super heavy (beyond 10.x gr) pellets will be alright. I did test JSB 10.3s for the first shots and they averaged just over 1050 fps, so yeah, heavier is likely a good idea.
The box arrived in good shape. The barrel needed the requisite cleaning, lots of crud in there. The wood grain is attractive on my example. I mounted a DNT ThermNight 225, a DonnyFL Yokozuna, and stuffed the foam from 3 foam hair curlers over the barrel in the shroud to slow the air coming back out the perforated shroud. It is stupidly quiet this way, the action is much louder to the ear than anything else in the shot cycle.
Turns out I get 29.2 fpe with JSB Beasts (16.2 gr) with the factory settings. So we’re close to 30 fpe. Seems the reg is right around 1750 psi on my example, so performance headroom on the regulator is there. As has been reported with the P35, P15, and variants the hammer spring seems to runs out of adjustability before the regulator maxes out. Mine was set with about 1/2 turn left of increasing preload before bottoming out. Since I wanted to see some high fpe, I maxed the hammer and then backed off a tiny bit.
With the JSB KO 13.43 slugs I get right at 60 shots before it falls off the regulator. Velocity just gracefully falls as we drop below the regulator pressure. So 5 magazines before we need a refill.
Below is listed the projectile weight versus energy for pellets (average of 11 shots/1 magazine).
Weight Energy Projectile
10.3 24.63 FX Pellet
13.4 27.38 FX Pellet
15.42 27.99 Gamo G-Hammer
15.74 28.26 H&N Rabbit Magnum II
16.1 28.39 Seneca Domes
16.2 29.17 JSB Beast
The Seneca Domes were the most accurate with this tune, though the Beasts and Rabbit Magnum II were very acceptable.
Below is listed the projectile weight versus energy for slugs (average of 11 shots/1 magazine).
Weight Energy Projectile
13 27.03 Zan
13.43 26.73 JSB KO
15 25.78 NSA
16 27.14 H&N
16 27.72 Zan
18 26.13 Wildman
20 26.88 H&N
20 26.51 Zan
The JSB KOs shot very well. However, the H&N 20gr really shined. The first 4 shots all went through a barely enlarging hole and the following 7 whittled that hole a bit bigger except one shot that wandered just enough to oblong the hole - probably me. Shooting at 25 yards has me shooting sub-sub dime sized 11 shot groups for everything but the 15gr NSAs, it appears this barrel does not get along with those slugs, at least with this tune. In my experience with SPA barrels, they tend to like either the super-light or super-heavy stuff. Someday I’ll write up my experiences with my loveably schizophrenic Notos.
In the graph you can clearly see the slug weight versus energy curve is significantly behind the pellets. I conclude from the chart that we’re best off if we have projectiles in the 16gr range. Sometime this winter I’ll open it up and see if I can get that 32fpe with 16gr at around 950.
Back when dinosaurs roamed the earth, and springers were top shelf aspirations while MSPs were the norm, very strong performance in .177 was about 16 fpe. Even today springers exceeding 20 fpe in .177 are pretty uncommon. At the expected performance of about 30 fpe we’ll probably be looking for slugs in order to perform well. Maybe some of the super heavy (beyond 10.x gr) pellets will be alright. I did test JSB 10.3s for the first shots and they averaged just over 1050 fps, so yeah, heavier is likely a good idea.
The box arrived in good shape. The barrel needed the requisite cleaning, lots of crud in there. The wood grain is attractive on my example. I mounted a DNT ThermNight 225, a DonnyFL Yokozuna, and stuffed the foam from 3 foam hair curlers over the barrel in the shroud to slow the air coming back out the perforated shroud. It is stupidly quiet this way, the action is much louder to the ear than anything else in the shot cycle.
Turns out I get 29.2 fpe with JSB Beasts (16.2 gr) with the factory settings. So we’re close to 30 fpe. Seems the reg is right around 1750 psi on my example, so performance headroom on the regulator is there. As has been reported with the P35, P15, and variants the hammer spring seems to runs out of adjustability before the regulator maxes out. Mine was set with about 1/2 turn left of increasing preload before bottoming out. Since I wanted to see some high fpe, I maxed the hammer and then backed off a tiny bit.
With the JSB KO 13.43 slugs I get right at 60 shots before it falls off the regulator. Velocity just gracefully falls as we drop below the regulator pressure. So 5 magazines before we need a refill.
Below is listed the projectile weight versus energy for pellets (average of 11 shots/1 magazine).
Weight Energy Projectile
10.3 24.63 FX Pellet
13.4 27.38 FX Pellet
15.42 27.99 Gamo G-Hammer
15.74 28.26 H&N Rabbit Magnum II
16.1 28.39 Seneca Domes
16.2 29.17 JSB Beast
The Seneca Domes were the most accurate with this tune, though the Beasts and Rabbit Magnum II were very acceptable.
Below is listed the projectile weight versus energy for slugs (average of 11 shots/1 magazine).
Weight Energy Projectile
13 27.03 Zan
13.43 26.73 JSB KO
15 25.78 NSA
16 27.14 H&N
16 27.72 Zan
18 26.13 Wildman
20 26.88 H&N
20 26.51 Zan
The JSB KOs shot very well. However, the H&N 20gr really shined. The first 4 shots all went through a barely enlarging hole and the following 7 whittled that hole a bit bigger except one shot that wandered just enough to oblong the hole - probably me. Shooting at 25 yards has me shooting sub-sub dime sized 11 shot groups for everything but the 15gr NSAs, it appears this barrel does not get along with those slugs, at least with this tune. In my experience with SPA barrels, they tend to like either the super-light or super-heavy stuff. Someday I’ll write up my experiences with my loveably schizophrenic Notos.
In the graph you can clearly see the slug weight versus energy curve is significantly behind the pellets. I conclude from the chart that we’re best off if we have projectiles in the 16gr range. Sometime this winter I’ll open it up and see if I can get that 32fpe with 16gr at around 950.
