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All Springer/NP/PCP Air Gun Discussion General > Czech & Russian Air Guns
Air Venturi AV-46M Review
Dale O:
Old topic I know. but rather than start a new topic I felt posting here is more fitting. My AV-46M arrived yesterday and I'm getting 415 fps. That being the case I'll go ahead and make the adjustment to the piston TDC as posted here. To get be in the 480 - 500 fps range how many clicks should I add to the piston stroke would you say?
subscriber:
Dale,
I would try two increments (half a revolution). It may not be possible to get all the way to 500 FPS by means of just the piston length adjustment.
What pellets you are using? Have tried adding a drop of oil to the piston seal before measuring the velocity?
Something that seems to help is conditioning the piston seal by exercising it: Open the cocking arm fully to set the valve. Then almost close the cocking arm to full compression. Rather than going so far as to latch the lever closed, let it spring back on compression about 20 degrees, then reclose it to almost latch. Do that at about one second intervals or a bit faster, 10 or 20 times in a row. This heats and softens to piston seal to better conform to the compression cylinder. I would only do this if I am confident about the lubrication at the piston seal.
If you shoot the pistol over a crony after some time in storage, you will notice the velocity drift up a bit, over the first 10 to 20 shots, or so. This is the piston seal conditioning from actual use. You can hurry that up, by doing the above exercise.
If you go too far with the piston length adjustment, the piston seal will run into the front wall of the compression chamber. Depending on how far it tries to compress the piston seal, you may feel some additional resistance at the end of the stroke. Mine started out that way, but the seal took a set, and extra force went away after some time.
If it feels like you are going to break something, then back off the piston length setting by one increment.
You can also increase compression by adding a rubber band into the cavity in the piston seal, like this GTA user: www.gatewaytoairguns.org/GTA/index.php?topic=153388.msg156094214#msg156094214
When you store your 46M, do not latch the breech closed all the way. That is to avoid squashing the breech seals over time, which seems like a leak point on these pistols, costing performance.
Do not dry fire the pistol without first latching the breech all the way closed. Dry firing with the breech slightly open tends to launch the breech seals to an inconvenient location for retrieval. Ask me how I know :) . It is not possible to dry fire with the breech fully open.
Hope this helps.
Dale O:
Thanks for the reply! I'm using 7.0 gr Meisterkugeln, I have R10 match in 7.0 coming today. Maybe I'll shot the pistol as is for awhile to see if velocity goes up a bit and to break in the seal. Or is it better to make the TDC adjustment now and let the seal break in?
Also, is 450 fps a more realistic number with this pistol? I'm fine with that as well.
Thanks Again!
Dale O:
Well, while drinking my coffee I decided to go ahead and raise the TDC of the piston. The process only took 15 minutes or so and I'm now at 445 fps with my first 10 shots after. I increased TDC by 2 clicks = 1/2 turn on the piston. I'm going to leave it here since there is no binding at the end of the compression stroke and I don't want to push it by adding one more click at this time. Maybe after 1000 shots I'll add that extra click and perhaps even the rubber band in the seal groove and see if I can get to 500 fps.
So far very pleased with this pistol!
subscriber:
The question of velocity is a tricky one, because those writing specs like to exaggerate. More important than absolute velocity is consistent velocity: Yet, I think that there is a split between those stating that 400 FPS is fast enough for a 10 meter target pistol, and those saying they want the advertised velocity.
Here is Pyramyd Air's test video of the original 46M. They got 428 FPS with 7.56 grain lead pellets. That predicts about 445 FPS with a 7 grain pellet. That produces 3 foot.pounds:
Here is a historical PA blog post on the topic; suggesting closer to 500 FPS with 7 grain pellets:
www.pyramydair.com/blog/2006/3/izh-46-target-pistol/
--- Quote ---The 46M is powerful!
I own a standard model 46, which may not be available any longer. The 46M that replaced it has a longer pump stroke for higher pressures that deliver about 50 to 70 f.p.s. higher velocity with target pellets. Side-by-side, you can tell the M model is a trifle harder to pump. When it’s by itself, you’ll never notice the difference. I would love to trade up to an M, even though my 8-year-old model 46 still functions fine. My 46 gets about 430 f.p.s. with RWS R-10 Match Pellets (light). A 46M will get 480 to 500 f.p.s. with the same pellet.
--- End quote ---
PA specs your AV 46M at 480 FPS - click specification tab: https://www.pyramydair.com/product/air-venturi-av-46m-match-air-pistol?m=5257
I like the cleaner hole a wadcutter makes at 500 FPS relative to 400. Sure, you can back up the target with a stiff card material to get a clean hole. I also think that a velocity variation of 10 FPS on 400 FP produces more vertical drift than the same 10 FPS variation at 500 FPS.
From the sound of it, you could try another "click" on your piston adjustment, and back it off again if you do not like it. The piston seal is soft and will deform, if you overdo it. Just don't try for 4 clicks. Rather add the elastic band to take up open air volume.
What I can tell you is that more compression means more peak cocking force. If you like it easy at 440 FPS, then perhaps chasing another 40 FPS at the expense of easy cocking is not what you want.
I notice that a dab of molly grease on the cocking cam surfaces reduces cocking force noticeably. The last time I measured the FPS on my 46M it was producing 4 foot.lb. So, it understandably would require more cocking force, because the extra pellet energy has to come from somewhere.
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