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oneshot1979

Springer recoil wrecking scopes.

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As the title says really.

Decided to dig out a couple old springers from the cupboard for some plinking fun. One of them is a 74-78 BSA mercury that I grew up with and hasn't been used in over 10 years plus so first job was to strip down and inspect it. Gave it a good once over, new breech seal, deburr and polish up inside etc. Also got carried away and did away with the knackered nylon piston and with no new part to hand quickly turned up a phosphor bronze piston and fitted a new "O" ring. Reassembled with original spring and ran 20-30 lube saturated pellets through. Quick clean of the barrel and then remounted original ASI 4x32 scope that's been on it the last 20 years and settled down to zero it. Using Accupels started to get nice tidy groups straight away so started adjusting point of aim to correct zero but after 20 or so pellets the groups started have really random flyers, two inches off target and more. Sat back and scratched my head and noticed the cross hairs looked a little canted off, was sure I had them level, ho hum readjust and try again. 10 shots later cross hairs have canted again. Now I'd marked the scope so I know it's not turning in the rings, must be a fault in the old scope I thought. Pulled scope off and decided sod it. Stripped down the rear of the scope (nothing to lose) and had a look. Turns out the loctite holding the cross hair reticule had let go allowing it to rotate. Mutter mutter. Back to the cupboard, no practical spare scope available.... Brainwave. Quickly whip the EIB 6x40 scope off of the .22WMR and onto the Mercury. Boresighted to save wasting pellets and tried zeroing again. SAME DAMN THING. Good tidy groups, sudden flyers and low and behold cross hair canted. Two scopes wrecked in under 50-60 pellets. Now that EIB scope has been on the .22WMR for the best part of 15yrs and seen some heavy use onfoot and in vehicles she's the go to gun for anything close enough to be heard from the kitchen window and has been bounced dropped and knocked and never moved off zero enough to make me worry but 20-30 shots on a sodding spring gun and the reticule is knackered. Am I missing something ? Can the forces in the recoil of a Springer really be worse than that of a .22WMR. Really not in the mood to wreck another scope just to prove a point, plus all the others available in the cabinet are considerably dearer than the two I've wrecked so far. Thoughts from the collective please ?

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Yes the recoil effect of even a pretty mild springer is 5x  worse than a . 308 .

The reason .is that its backwards AND forwards   .like a whip

.cf.guns ,  shot guns etc its just backwards .the springer recoil  changes direction very fast and violently .hence the damage . First it goes backwards (recoil ) then it goes forwards  this motion is called surge .

 

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I had this years ago with my Webley tracker, I had a Nikko Stirling on it, I would constantly loose zero, the cross hairs didn't cant like you've had but I'd have to re zero.

It went back under warranty,  they phoned up saying there was no problem on a .243, i explained it was on a Springer, re test and got a new scope, which I swapped for a Tasco.

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Yep had it on an old airsporter, did 3 scopes in as many weeks. As you said one had been on a 22 - 250 if I remember rightly. 

 

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So what are my options then? Would the piston weight really make that much difference?. Is there any other way if damping it?. Is there a particular scope that's better suited to the abuse? Could I convert to a gas ram. I know it's only an old BSA but it has sentimental value and if I can get it reliable would be a great thing to pass down to my girls.

 

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The weight of the piston is every thing when it comes to springer tuning .

Actually .its probably too light .Briefly what happens is

the piston is released by the trigger and accelerstes forwards compressing the air in front of it .this forwards movement has an opposite and equal rearward movement felt as recoil of the stock.the heavier the piston .the slower it will be but longer in time and length. As the piston  compresses the air the pressure bulids very quickly raising the compressed air temp to around 200  degree  c .

The air cannot escape the compression chamber quick enough due to the narrow exit hole to the barrel known as the transfer port . (2 -3 mm ish ) so the piston bounces off the compressed air and travels backwards ( this has an equal /opposite reaction ) and the stock moves forwards  - hence the surge and whip effect .

The lighter the piston the lower the recoil but greater the surge  .also the sooner the piston bounces off the comressed air . (Which may not be high enough to get much energy into the pellet )  At  some point during the recoil  phase the pellet  starts to move in the barrel and exit during the surge phase ..as the barrel flips upwards  then downwards .

 

 

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If its shooting smooth and consistent can you not use open sights?

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The ideal tune is for a springer is when all the elements are perfectly balanced and the piston comes down the cylinder at the correct speed with correct  spring tension behind it ..it compresses the air at such a rate and to a pressure that the piston is slowed down to a stop with very /no bounce .this allows the pressure to build  and then escape through the tp .driving the pellet .

All the elements must be in harmony for this to happen and there are a lot of different elements  .change a small one (pellet size ) and you get a small change .change a big one like spring preload  and you get a larger change - like dropped energy and more recoil .

Change a massive element like piston weight and it can wreck scopes its that far out of tune  

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I have seen on a number of occasions people talking about putting a stronger spring in the gun to give it more power, is it possible that the op gun has had an stronger spring fitted?

Never quite understood how a stronger spring could give an airgun more power, always thought it was volume that increased power.

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Original spring, removed degreased checked over and refitted. Work the action for good 5mins to compress and release spring to condition as such after so long stood up. It has to be the piston. It's the only thing that's changed. A little googling had suggested a slightly heavy piston would bring the performance up. The old nylon one was cracked up and worn beyond repair so fashioned one out of what I had available. Will have to source some nylon and try again. Iron sights were removed long ago and lost in the mists of time. Might look into the red dot idea. Once it's sorted the missus and eldest have expressed interest in using it to keep the bird feeders free if vermin so a simple sight may suit them more. Will pull it apart later........

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The original piston heads were aluminium, BSA changed them to nylon at some point. Each one I have repaired, the nylon piston head was swollen and jammed in the cylinder. The answer was to replace it with an aluminium one. Phosphor bronze might be too heavy, although you probably have one of the most expensive piston heads in existence 😂.

As Old'un suggested, sometimes a stronger spring isn't the best answer to the quest for more power.

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