Airgun Erratic shotfall
Three things mess up consistent shotfall in a spring airgun.
1. The shooter.
2. The pellets.
3. The rubbish scopes and mounts sold as suitable for airguns.
1. The shooter
Bad holding of a weapon is the single most common reason for missing the shot.
With spring powered airguns it is vital to hold the rifle consistently to ensure that the rifle "rings" the same way everytime.
Spring powered rifles are amazing. They subject you to a number of jerks during it´s firing cycle which cause the springer to thrash round in your hands like a mad thing. The novice will always try and fight this effect.
The trigger releases and the sear lets a couple of hundred weight of spring pressure loose. This is the start of the game. The piston flies forward. It's never an equal and opposite force and generally it jerks the rifle back into your shoulder.
The piston compresses enough air to form a cushion, which bounces the piston back the way it came from. The spring overcomes this bounce forcing the compressed air onto the base of the pellet. The pellet flies out the barrel hopefully before the piston stops with a controlled crash an the end of it's travel. This is followed by a jet of compressed air giving a jet effect push back into your shoulder.
Net result, little true recoil, and the gun appears to want to fly down, back up and forward out of your hands.
You cannot fight this effect. It is just too strong. If you try, the gun will shoot wildly so:
The golden rules about holding a spring gun are:
Hold the rifle gently and lightly against your shoulder.
Do not grip the stock with your trigger hand, lightly curl round it.
Support the fore end where the gun balances. Do not grip it rather cradle it. Use a glove to avoid slip.
Keep your elbow under the gun stock and not in the classic tripod stance of firearm shooters.
NEVER rest the gun on a solid surface. It will jump uncontrollably.
Even bean or sand bags can be too hard and the airgun bounces round a treat when using them.
Slings sort of help but only to support the weight. Don´t use a sling to pull the rifle back into the shoulder.
Learn how to shoot the way Field target shooters do. Their sitting positions are the most stable way to support a "springer".
2. The pellets
Are all pellets the same and does it matter what you feed your rifle on?
The answer is an emphatic YES. the pellet may be too long, too short, too hard, or too heavy for your rifle.
Manufacturers generally recommend what lead to shoot with but you should try out every type, size, weight, and shape you can and carefully chart each test. Its going to be expensive but if you want accuracy you owe it to yourself to feed the rifle with the best (which does not necessarily mean the most expensive) pellets. A quick example. I use Bisley Magnums in my Harrier. Accuracy is better than 1/4 inch groups over 25 yards in an indoor range. I put a shorter different design pellet (Webley Hustlers) and the shot fall changes by a good 1/2 inch up and to the right. Group sizes increase to 1/2 inch groups. I also use a HW35 spring carbine. It likes both pellets but the Bisley shoots low by 1/2 inch at 25 yards. The Webley is bang on and holds a good 3/8 of an inch group at 25 yards (indoors). It is a bit of a bind having to use two types of ammunition but as accuracy is everything it has turned out to be a necessity.
Pellet Shapes.
Which you choose is down to what you want to shoot.
The term Diablo is sometimes used with pellet shapes but the word Diablo lends it self more to the shape of the waist than the pointy bit on the front but why have the waist in the first place?
A number of reasons.
The peculiar shape looks like a badminton shuttle cock. The one thing great thing about that shape is it is self stabilizing. It works in pellets too according to the experts but again, deform the shape and wobbling it will go.
Less metal to metal contact means that energy is not lost pushing the pellet along the barrel.
The skirt or bottom rim should fill the lands and grooves of the rifling and make a perfect gas seal. If it does not, air leaks round the pellet and you lose speed. The slam of air pressure onto the base of the pellet also causes the skirt to expand and improves the seal BUT, too hard a pellet and this does not happen, too soft a pellet and the pressure could blow a hole in the skirt and deform the pellet shape. Deformation leads to bad stability and lose of accuracy.
Pointed style pellets are built for penetration. They burrow deep BUT unless they hit a vital organ, damage to the target is minor. Hollow points are really only useful with FAC rated airguns. This is because they do not build up the bubble of air in the cup necessary to 'explode' the target at lower powers. In the UK and with 12 ftlb limits, they are about as effective as a good dome head pellet.
The ogival (sort of pointed arch) nose is the best compromise for penetration and shock transfer. The experts ideal pellet shape is a length to diameter ratio of roughly 3:1 to 4:1, with ogival nose. The hollow tail keeps the weight forward.
Calibre and speed.
Basically .177 flies at the highest velocity for a given amount of airgun energy. Don't be worried about exceeding the sound barrier though as to get the pellet to exceed 1080 fps would need 16 ftlbs (ish) of force which is way over the legal limit of 12 ftlbs in the UK. IF you did exceed it though, you would hear the crack of supersonic speed and then have the pleasure of watching your pellet wildly tumbling and landing anywhere but where you want it to.
The .20 (5mm) pellet is much better than the .177. It flies as flat but hits round 40% harder.
The .22 (5.5mm) is generally the choice of hunters. Good thump but it flies in a higher trajectory, slower, and is less affected more by wind drift.
At close range it is impressive at knocking down rabbits whereas the .177 just goes through the target.
The .25 (6.3mm) is unbeatable in knock-down force. It's effectiveness is lost on a 12ftlb legal limit airgun. Strongly recommended for FAC rated airguns though.
Pellets are made from lead (Pb).
The best ones have a little hardener mixed in called Antimony BUT NOT MUCH. Occasionally they are coated in lubricant. Don't be tempted to add your own. A little goes a very long way and getting it wrong could render a complete tin inaccurate. There are casting moulds for pellets out there but they tend to make bullet shapes more than waisted shapes. You can buy a swager kit for stamping out pellets but in the long run it is possibly the best idea to buy the best that you can afford.
Care of pellets.
Damage is a big NO NO. The accuracy of a pellet is in its shape. It spins in a barrel but once released into the outside world, any unbalance will induce a wobble. Result, you miss. Plastic or foam lined 'tins' are the best way to buy them. Don't just load your pockets. Fluff and other debris, coins for damage, and moisture will all damage the delicate lead shapes. In case you think I am joking about the delicate shape, consider that the soft lead is designed to hopefully expand on impact and transfer all its energy to the target.
That's fine as lead Pb is very soft BUT if you deform it by denting, scratching or any other sort of deformation it's accuracy suffers.
Oil and lubes.
They can improve performance dramatically BUT too much of a good thing is bad. If you can see the lube or oil, there is too much on the pellet.
Pellet To Barrel Fit
Too loose and the pellet does not grip the rifling enough and the pellet is able to slide out of the barrel with the minimum of force. You need the correct level of resistance to allow the air pressure to reach a peak before the pellet exits from the barrel. Again too loose and the pellet can tumble in the barrel. Too tight and you have real problems. The head will be crushed, the pellet will most likely be shaved a little by the rifling forget accuracy! The air pressure will have to force the pellet along the barrel and you will lose power in friction and heat.
Air resistance increases with the cube of a pellet's speed. Doubling the pellets speed actually makes the air resistance 8X more. In real terms, the faster the pellet, the quicker it slows down.
Wind and pellets.
The bigger and slower the pellet, the less wind blows them round. Its all to do with something the experts call ballistic coefficient. Bottom line, the heavier the pellet the better when in the field. (Wind does not deflect a brick as much as a feather).
3. Rubbish Scopes.
The forces on a scope when mounted on a spring rifle are incredible. Anyone who has shot a spring airgun knows too well the effect of scope creep. This is where the recoil is so fierce that the mount moves backwards with every shot. Rubber shock absorbing mounts claim to help but they only ease the problem never cure it fully. Optics tend to be cheap and nasty with adjustment screws that interact and work against spring tensioners never fully locking the reticle lens or tube in place.
If you own a spring airgun forget the cheap option. Buy full bore rated scopes and the best mounts you can. Fit slide locks behind the scope mount but don't forget to loosen the scope mount every so often as the recoil force will "tension" the scope mounts against the slide stops. This in time will "flex" the scope tube and change the shotfall.
Finally, a spring airgun is generally a robust bit of kit that takes abuse well. Cheap to "feed" and great for small game. It will never be as accurate as a precharged Pneumatic though and in the UK with the pathetic 12ft lb limit you need to put your pellet on the right spot everytime to avoid bad kills.
Hope this helps.
