Chrony Results: Stock Beeman P17

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pcmccoy

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Apr 25, 2016
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Just purchased a chronograph (ProChrono Digital, after reading lots of reviews). Seems to work well, I'm happy with it. I'll be doing some experimenting and wish to share the data. I understand the parallax issues with indoor lighting that can cause a systematic error of falsely elevated velocity readings. I am using the light kit indoors for testing in an otherwise dark room.

The Beeman P17 is well known for its low price point, fair trigger, and surprising accuracy. There are several excellent threads elsewhere discussing this airgun e.g.: http://www.gatewaytoairguns.org/GTA/index.php?topic=49115.0

I have been curious if it lived up to its reputation. It is marketed as a 410 fps pistol. I have a stock P17 with less than 200 pellets through it....and a shiny new chronograph. I need wonder no longer: (I'm shooting JSB Exact Express 7.87 gn pellets)
  1. 415
  2. 416
  3. 414
  4. 415
  5. 412
  6. 415
  7. 414
  8. 414
  9. 412
  10. 415
    [/LIST=1]
    High: 416 Low: 412
    Avg: 414
    Es: 4
    Sd: 1.32 (thanks gamyrick.)

    Looks good to me.

 
I have had my p17 for several years now and have made no modifications to the powerplant (except replacing old o rings) and it does not shoot nearly that hot. 388 fps from a 5 shot average using crosman 7.4 grain wadcutters. My shots were also extremely consistent. I wonder why i am only getting 3.35 Joules while you managed over 4. 
 
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This is just a sample of velocity from my P17:

RWS Basic 7 gr. (actual weight is 7.3 to 7.5 gr.) - 424.3 fps
RWS R10 7 gr. - 432.1 fps
Crosman 7.9 gr. H.P. - 406.0 fps
H&N Match Green 5.2 gr. - 483.3 fps

Another P17 I checked was averaging about 10 fps range slower velocities.

Another P17 I checked was averaging about 30 fps range slower velocities.

Luck of the draw I guess.
 
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I wonder what causes the difference in energy. Maybe on some p17s the seal between the barrel and the air chamber leaks a little. or maybe something to do with the gap between the end of the piston and the end of the air cylinder when the gun is closed. smaller gap --> higher pressure --> more energy on the pellet.
Very weird that there is so much variation.
 
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Difference in energy is probably just due to size difference in the pellets. OP said he was using JSB’s, follow ups stated they were using crosman & h&n pellets. In my lgv I get about 2 ft lbs more using JSBs due to softer lead and looser fit over the crosman/h&n pellets leading to higher fps. Prob get more fps with the JSBs. Just my 2cents...which is probably about all it’s worth...
 
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I retested all 3 P17's using JSB Exact Express 7.87 gr. dome pellets this morning. Pellets sorted by visual inspection, weight - (7.80 - 7.89 grain), head diameter - (4.50) and rolling radius the same.

P17 #1 - 413.1 fps avg.
413.2 - High
409.8 - Low

P17 #2 - 398.2 fps avg.
398.8 - High
397.2 - Low

P17 #3 - 397.5 fps avg.
402.4 - High
393.7- Low

I have been experimenting with #3, as the velocity compared with the other 2 P17's was about 30 fps lower. I moved the barrel toward the breech O Ring some and the velocity increased to where it's the same as #2. The adjustment isn't precise, it is a hit or miss adjustment. I wish someone would make precision cut washers, that goes on the end of the barrel, of .001, .002, .003 and .005" thickness to adjust the barrel to O Ring.

After the velocity tests, this morning, I again readjusted the barrel to breech O Ring, on #3, and the velocity again increased to almost match #1.

Before adjustment:
397.5 fps avg.
402.4 - High
393.7- Low

After adjustment:
410.3 fps avg.
411.5 - High
409.4 - Low

#1 is the most accurate, at 10 meters, averaging .218 C to C 5 shot groups (scope and off sandbags), #2 shoots about 1/10" larger groups with the pellets it likes. #3 however, won't do any better than around 1/2" groups regardless of pellets used. Pellets fall easily into the chamber of #3. I no longer have access to longer ranges and the longest distance I have now is 20 yards. #1 averages .515" (10 shot groups, scope and sandbags) at 20 yards. I haven't had a chance with the other two as I have to choose a day that has no wind blowing.

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This is a pasted post I made regarding mine, posted on another forum:

I see that this is an older posting, but I just picked up a 2004 on a trade and figured I'd add my 2 cents:

Seems like a solid value. Mine was clocking at 425 fps with Hobbies, but accuracy with 6 different kinds of ammo was disappointing (maybe a bad barrel on this one?)

I took a spare CR MK-1 barrel and turned it on a lathe to fit. Accuracy improved immensely, and .22 cal pells are WAY easier to load. Velocity is still a decent 340 fps, and it really bounces those cans around.

Here's a few problems I had, and how I fixed them..

Difficult loading: 
(This with the stock .177 bbl) The barrel is EZ to remove. A plate and two screws hold it in place. Remove the barrel and chamfer the breech lightly with a chamfering tool. This creates a lead-in that facilitates loading.

Rear sight elevation screw un-screws during use:
A tiny amount of "Gorilla Glue" on the end of a tooth pick. Sight can still be adjusted, but stays put.

Pins in the frame start 'walking' out while shooting:
Tried loctite and then G glue. Neither worked for very long. Took four 2-56 x 1/8" set screws and screwed these into the small holes inside the frame until they contacted the wayward pins.

Barrel bore slightly misaligned with outlet port:
If you have access to a chronograph, load and clock the velocity. Then, remove the plate which clamps the barrel in place. Pull the breech-end of the barrel out of the frame just slightly. Load and clock it again.

A higher velocity means that the bore is not perfectly aligned with the outlet port when the clamp is in place,
I fixed mine with three layers of small shims, cut from a plastic playing card. Velocity is now maxed.

(Also of note, the barrel can be adjust forward and backwards by loosening the clamping plate, make sure it's back far enough to make good contact with the O ring breech seal. Too far forward, and you'll lose velocity due to a poor seal)

This is minor, but I found the sight picture improved by the application of some ivory-colored nail polish on the front sight post.

Really liking this little thumper. Have around 50 different air guns, and this is my favorite 'grasshopper' gun!

Best Regards,
Skillet
 
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