Results 1 to 8 of 8

Thread: Increase Gamo Shadow 640 velocity?

  1. #1
    Inactive Member

    User Info Menu

    Default Increase Gamo Shadow 640 velocity?

    Howzit guys. Im new to the forum and also my first thread. Ive searched on increasing power on a Gamo shadow 640 or actually increasing power on any 500-650 fps spring rifles.
    So I got a Shadow 640 the other day and I love to do my own thing shooting 40m to 50m sometimes play around and try further distance with my 2 power rifles.
    I like to try new DIY stuff and I am an qualified artisan so I do have my basics in mechanics and all sorts but I was maybe thinking instead of selling the 640 which is still like new only fired 10 pellets... I want to try and get this 640 to around 900-1000fps just as a way to keep me busy and out of trouble.
    My father in law use to know Vince very well and use to get his rifles done by him and I know everyone recommends gas ram. And I honestly do agree that gas ram is really nice but I want to keep it spring only.
    I was wondering if I actually add in a little piece of spring ( which is actually a backyard idea ) would it actually work?? Not add in to try and push limits but add in just to reach that slight jump in power.. or....... even buy a new Gamo Shadow 1000 spring and replace it with the current spring? Will the fit be right regarding size ? Ive tried to search it aswell but got no info on that.
    This might have been asked before and please accept my apology in advance if there has been a similiar thread. And Sorry if its a dumb question I am just really interested to know if either of those will actually work and what Is needed.
    Thanks guys. Hope you guys can give me some advise on those ideas.
    Sign Up To Air Rifle SA Forums

  2. #2
    Marksman
    Forum Sponsor

    User Info Menu

    Default

    Welcome to the forum Boet.

    Now here's my 2c regarding juicing up the power... 1000fps may be achievable with your 640, but in another universe or 3km below sea level.

    The reasons behind this are that the rifle is a small bore with a small stroke piston. Velocity is determined by how much air can be compressed behind the pellet in order to move it forward. If you've only got a small amount of air to compress, you only get a small amount of force to propel the pellet.

    You can increase this force slightly by adding some preload on the form of washers on the fore end and back end of the spring in order to increase the tension in the spring when it is cocked. This results in the spring releasing its energy forwards quicker and compressing the air more at the expense of shot cycle quality. This normally can increase the power around 5% without any real notice in the shot cycle quality.

    You can do a basic lube and tune as well and if you really really want to, changing the spring guide to make it fit like a glove and making a tophat for the piston. The physics behind this is simple. Polished spring ends reduce the friction against the guide and piston which translates into a smoother uncoiling of the spring when the trigger is pulled. A proper fitting spring guide and tophat allow the spring to transfer its force more laterally as opposed to in all directions.

    I've been down the same route you have trying to squeeze more out of your rifle. In the end I just bought a more powerful one if I wanted to do real shooting. The 640 is great for bell target shooting and backyard plinking, but after 25m you're going to notice those slower speeds and accuracy will be affected.
    Sign Up To Air Rifle SA Forums

  3. #3
    Sharp Shooter

    User Info Menu

    Default

    from 640 to 1000fps is a long shot, maybe 700fps is a more realistic goal... my opinion is sell it and buy yourself another (more poweful) pellet gun at the pawn shop to keep yourself busy with.
    Sign Up To Air Rifle SA Forums

  4. #4
    Inactive Member

    User Info Menu

    Default

    Quote Originally Posted by The_Thomas View Post
    Welcome to the forum Boet.

    Now here's my 2c regarding juicing up the power... 1000fps may be achievable with your 640, but in another universe or 3km below sea level.

    The reasons behind this are that the rifle is a small bore with a small stroke piston. Velocity is determined by how much air can be compressed behind the pellet in order to move it forward. If you've only got a small amount of air to compress, you only get a small amount of force to propel the pellet.

    You can increase this force slightly by adding some preload on the form of washers on the fore end and back end of the spring in order to increase the tension in the spring when it is cocked. This results in the spring releasing its energy forwards quicker and compressing the air more at the expense of shot cycle quality. This normally can increase the power around 5% without any real notice in the shot cycle quality.

    You can do a basic lube and tune as well and if you really really want to, changing the spring guide to make it fit like a glove and making a tophat for the piston. The physics behind this is simple. Polished spring ends reduce the friction against the guide and piston which translates into a smoother uncoiling of the spring when the trigger is pulled. A proper fitting spring guide and tophat allow the spring to transfer its force more laterally as opposed to in all directions.

    I've been down the same route you have trying to squeeze more out of your rifle. In the end I just bought a more powerful one if I wanted to do real shooting. The 640 is great for bell target shooting and backyard plinking, but after 25m you're going to notice those slower speeds and accuracy will be affected.
    Dude thank you for this..
    Made it very clear and makes complete sense what you are saying.
    I actually sat down today and played around at 30meters..actually 32meters..And I was amazed... After sighting scope eventually I managed to group 6 shots in the centre which i didnt expect at all. I thought the pellet would be dropping by then.This little rifle keeps on impressing me. I do have other rifles with high velocity which I use but just thought to make a project out of this and see what could be done. even modify a Hammeli silencer on today just for the look LOL. I will defnitily try the washer and polish you suggested.
    Again thanks for the advise. Highly appreciate it.
    Sign Up To Air Rifle SA Forums

  5. #5
    Inactive Member

    User Info Menu

    Default

    Quote Originally Posted by Kw2112 View Post
    from 640 to 1000fps is a long shot, maybe 700fps is a more realistic goal... my opinion is sell it and buy yourself another (more poweful) pellet gun at the pawn shop to keep yourself busy with.
    Guess I will put it up for sale as I have other rifles that are high power and that I use to shoot distance
    Just wanted to see and make a little project out of it. Like I said even modified a Hammerli silencer on for some looks LOL
    Sign Up To Air Rifle SA Forums

  6. #6
    Sharp Shooter

    User Info Menu

    Default

    It's far easier to buy a high powered air rifle and tune it down for smoothness and accuracy then to buy a low powered air rifle and to try and tune it up - just something to remember, that's why I'm buying a walther parrus and not a walther terrus .
    Sign Up To Air Rifle SA Forums

  7. #7
    Sharp Shooter

    User Info Menu

    Default

    I also had a 600fps industries brand rifle that I planned on "building up" but soon realized I was wasting my time so I traded it for a run down Hatsan mod.55 which I fixed up (particularly enjoyed sanding the stock down and staining the wood to make it a unique colour) at the end of the day I sold it for a decent amount, I now have a Hatsan mod.85 as my next project.
    Sign Up To Air Rifle SA Forums

  8. #8
    Inactive Member

    User Info Menu

    Default

    Quote Originally Posted by gordon View Post
    It's far easier to buy a high powered air rifle and tune it down for smoothness and accuracy then to buy a low powered air rifle and to try and tune it up - just something to remember, that's why I'm buying a walther parrus and not a walther terrus .
    Very true yes. I just thought taking it on and trying just because i love doing it and trying new tricks. If it fails oh well onto the next LOL

    Quote Originally Posted by Kw2112 View Post
    I also had a 600fps industries brand rifle that I planned on "building up" but soon realized I was wasting my time so I traded it for a run down Hatsan mod.55 which I fixed up (particularly enjoyed sanding the stock down and staining the wood to make it a unique colour) at the end of the day I sold it for a decent amount, I now have a Hatsan mod.85 as my next project.
    Ive got a Hatsan MOD70 and I absolutely love it. I have this urg to get a Hatsan 105x torpedo as a project and dont know why because Im not a major fan of under levers but just attracts me everytime I see one
    Sign Up To Air Rifle SA Forums


Similar Threads

  1. Newbie wants to buy a Gamo SHadow 640
    By VeerVortex in forum Airgun Discussions
    Replies: 2
    Last Post: 16-04-06, 09:30

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Friends of Air Rifle SA