GTA
All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => China/Asian AirGun Gate => Topic started by: Airnut on April 01, 2018, 02:55:29 PM
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Hello
my guestion is what are the pros and cons of adding more pre load to the main spring?
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Too much pre-load can cause a condition that loads the spring so much that the rifle won't cock. I believe that it is called 'coil bind' or something. Extra pre-load can increase the harshness of the shot.
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The preload can be increased slightly to increase power and get the gun shooting at a specific level of performance. It can also increase the roughness of the shot cycle and make the gun more difficult to shoot accurately.
This is commonly done by adding one or two washers inside the compression tube as spring spacers. Since the spring length is already close to the maximum for a given gun, adding spacers can result in the spring becoming coil bound or completely compressed before the sear latches. In other words, it will no longer cock, precisely as suggested by Gene.
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Thanks! That confirms what I thought. My stock air magnum(22 cal.) shot a little weak out the box only 750 fps with a 9.9 pba pellet so I installed a breech kit and replaced the piston seal (vortex) installed three washers and lubed it up. That made it much better(1153 fps) but the spread was as much as 123 fps. and stdev was 52.1. So I then installed a pg2 kit with the same shims and lost 25 fps in velocity but the spread (30 ) and stdev(11.7) was much better and a lot smoother. So now I am pondering installing another shim or ordering a custom spring. the stock spring had a 40 coil count and the pg2 spring was 38 coil or am I wasting my time? my train of thought is the faster the velocity is i can shoot a heavier pellet to get the velocity down to about 850-900 fps. if that makes any sense?
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There is more involved here than spring lengths and spacers. The diameter of the wire used to wind the spring has a great effect on the power of the gun, not just the number of coils. Thicker wire will necessitate fewer coils before binding when cocked. Thicker wire generally yields more power and a more harsh recoil.
The fit of the piston seal in the compression tube has a great effect on power, consistency, and accuracy as well. It should take two to three pounds of force to push piston and seal through the compression tube. If less force is required you can damage things by the piston slamming the seal into the end of the compression tube. Too much force required will slow the movement of the piston resulting in lower power. It can also set up a vibration as the piston travels through the compression tube, affecting accuracy.
It is wise to keep pellet velocity a bit below the speed of sound to maintain accuracy.
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Hum and the plot thickens! I may want to leave well enough alone. Its shooting a 18.5 grain pellet avg. 842 fps 29.16 ft.pounds and is very accurate at 40 yards.
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Hum and the plot thickens! I may want to leave well enough alone. Its shooting a 18.5 grain pellet avg. 842 fps 29.16 ft.pounds and is very accurate at 40 yards.
I would shoot it like that. As long as you are happy with the accuracy, 29 ft.lbs is a very powerful springer.
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Thanks Gene!
I think I will take your advice!
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Hum and the plot thickens! I may want to leave well enough alone. Its shooting a 18.5 grain pellet avg. 842 fps 29.16 ft.pounds and is very accurate at 40 yards.
So sounds like the new spring has really got your RAM pushing that lead.18.3 great pellets doing 850 ish is in my opinion great.Just hope I can expect that from mine.That should do quite a job on crows and other pest I plan on confronting.My your good fortunes continue and enjoy your lead slinging. ~Cane Sniper 125
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Hum and the plot thickens! I may want to leave well enough alone. Its shooting a 18.5 grain pellet avg. 842 fps 29.16 ft.pounds and is very accurate at 40 yards.
So sounds like the new spring has really got your RAM pushing that lead.18.3 great pellets doing 850 ish is in my opinion great.Just hope I can expect that from mine.That should do quite a job on crows and other pest I plan on confronting.My your good fortunes continue and enjoy your lead slinging. ~Cane Sniper 125
Thanks Cane!
Judging from your post it sounds like you have or are planing on getting a RAM?
They are great for hunting after you get them shooting their best, and that takes some work!
Totaly love mine now but that wasnt allways the case.
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Swept volume of the 350/Air Magnum is 70.8 (cm3). You are reporting velocities that would put it in the realm of the Hatsan 125 (swept volume around 79). My Diana 350 with a Vortek spring and Tinbum kit is at around 830 fps with FTT's (14.7 gr). These guns at factory power tend to do 22-24 fpe. You are getting around 29. Not sure where you're getting all that power but I doubt seriously you will squeeze any more out of that platform. I'd leave well enough alone. Just my $.02.
https://www.gatewaytoairguns.org/GTA/index.php?topic=26322.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=26322.0)
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Well here we are after about 700 pellets through my Ram. I shot it throu the chrony yesterday and here are the results 18.5 grains at sea level 27 Fp that is down from last test (29.16) I think the drop in fp is because when tested the first time must of had some dieseling going on! Still shoots very accurate and the crows hate it.