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Author Topic: Air rifle pellets.  (Read 6311 times)

Offline Novagun

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Air rifle pellets.
« on: June 17, 2013, 09:22:58 AM »
Air rifles with few exceptions shoot ammunition called pellets and the peculiar shape is designated Diabolo. Bullets are for powder burning guns.  It has been said that the name Diabolo comes from the shape of a spool used in a foreign game. That name describes the rounded head, the waisted middle and the flared skirt. Pellets with variously shaped heads follow the same fundamental design.  The pellet is not a particularly aerodynamic shape but it is the best discovered so far to cope with the expectations put on it. The pellet head when loaded into the air rifle breach engages the barrel's rifling grooves. This rifling causes the pellet to spin as it travels the length of the barrel and greatly assists stability during flight; just as in a powerful powder burning rifle.

The waist of the pellet does four things. It reduces the weight of the pellet and friction. It also allows for the formation of a skirt at the tail end. That skirt is malleable so that the propelling air pressure behind it causes it to expand against the rifling of the barrel to form an air seal for the compressed air to push against. In doing so the skirt also engages the rifling.

The skirt leaves a hollow portion in the rear of the pellet and this part creates induced drag as the pellet travels through the air. This drag, being at the tail end of the pellet assists with directional stability and with preventing the pellet from tumbling head over tail. The tumble could occur because an air rifle pellet is short compared to it's diameter.

                                               .177 CALIBRE PELLETS

         

1: Crosman Premium Pointed 7.9gr
2: H&N Field Target Trophy 8.6gr
3: Daystate Rangemaster 8.5gr
4: Webly Accupell 7.9gr
5: Champion Fireball 9.0gr
6: Crosman Premier Heavy 10.5gr
7: JSB Predator 8.0gr
8: JSB Exact Express 7.87gr
9: RWS super Field 8.4gr
10: Gamo Pro Match 7.87gr
11: Crossman Destroyer 7.9gr
12: Crosman Premier 7.9gr
13: JSB Exact Diabolo 8.44gr

Pellets are generally made of some alloy of lead and are fairly soft and quite easily distorted. They need to be treated gently and such action as dropping or shaking their container can cause damage. That damage will affect accuracy. Avoid pellets that are too light or too heavy for the particular air rifle because repeated use of the wrong weight range can result in a broken spring. Generally a more powerful rifle such as those termed Magnum need heavy pellets and less powerful perform better with light pellets.   

All pellets are not created equal. Some of the cheap pellets should be avoided completely. They will not damage an air rifle but the production standards are so poor that accuracy is compromised. The saying is that the only good thing about them is the tin. Most pellets are supplied in tins.

Different pellets are made of different alloys and their hardness will vary. There are also variations in head shape and overall weight available in each calibre. Flat headed pellets, called wadcutters, are generally used for accurate short range target shooting. The flat head is meant to cut a clean hole in a target card to assist scoring. Some pellets are pointed to assist penetration and some hollow pointed to improve hitting shock for hunting.

The widely held opinion is that the round headed or dome head pellets are the best for accuracy and for long distance performance. Good quality pellets are associated with brand names. They are Accupels made by or for Webley; JSB made in Czechoslovakia, H & N made in Germany, Crossman Premiers, American but probably made in China. Air Arms made for the Air Arms rifle producers by JSB. Pellets are available in all the common calibres. That short list covers just about all the worthwhile ones. Just to complicate the choice some of the good pellets are rebranded and sold under the name of rifle manufacturers. They can be just as good as the original brand.

Good pellets are well formed and neatly finished. Any pellet that has a rough texture or marks or irregularities left from the forming dies should be avoided. Pellets are cheap enough so there is no need to compromise accuracy by using cheap substandard pellets.

Not only are all pellets not equal but some pellets do not suit a particular air rifle. There can be two identical rifles both shooting pellets out of the same tin but one rifle will shoot with better accuracy than the other. That does not mean that the second rifle is deficient. It just means it works better with a different pellet. There is no way of predicting that and the only way to establish the preferred pellet is by trial and error. Some pellet manufacturers produce sampler packs so that different pellets can be tried. The choice may go further than that and the best pellet for a particular  air rifle might be a different brand altogether.

The reasons for this peculiarity might concern pellet alloy hardness, pellet weight, barrel rifling, bore diameter and a myriad of factors effecting air rifle performance. Air rifles and indeed all firearms striving for accuracy can be affected by small changes in just one factor.

Now is a time to talk briefly about accuracy. It means different things to different people. Some shooters can take a small bird at a range of over 100 metres and up to 140 metres using a well adjusted PCP rifle with a telescopic sight. Most can not do that. Some shooters can shoot 25 pellets at 25 yards and put them all through the same hole.
Some can shoot a cheap single pump target rifle at 10 meters with the same accuracy. Most shooters can not do that and it is just about impossible with a spring powered rifle. Spring powered rifles are nevertheless capable of excellent accuracy and at moderate ranges are capable of shooting a ten shot group with one ragged edge hole. Say 10 mms across. Other air rifles are termed accurate when being able to knock over tin cans  at 15 metres. Accuracy expresses an opinion or a grade of precision and it all depends on the rifle and the expectations and aspirations of the shooter. Most hunters require practical accuracy but not the pin point accuracy of target shooters. The hunting target is much bigger than the 1 mm dot at the centre of a 10 metre air rifle target or the 10 mm bulls eye of a small bore target card.

Different  shooting activity requires different pellets. When hunting quarry such as a magpie with tough feathers the pellet needs to be able to penetrate the feathers so a pointed pellet and even a specialist pellet such as a plastic tipped Predator could be the most effective. With soft fleshed animals like possums and rabbits a pellet that delivers a knock down shock is best so blunter headed pellets will be best. A pointed pellet might just go right through without killing the prey quickly. Just remember that an airgun pellet has limited energy so the game that can be taken is limited in size.

Some shooters use pellets straight out of the tin to good effect. Some shooters wash new pellets and lubricate them with special oils or waxes. Some shooters polish the head of the pellet prior to loading and some warm them up slightly. Some weigh each pellet and group them into weight ranges. Some measure the head size of each pellet very precisely and chose only pellets within a certain size range. Some even roll the pellets down an incline to choose the most consistent skirt diameter  These are personal preferences and add confidence to the shooter. Try it out and see if it works for you.

All diabolo pellets are designed to be shot at speeds below the speed of sound and most perform best at speeds considerably lower than that. The speed of sound is about 1120 feet per second at sea level and varies with altitude and temperature. A pellet to perform to its designed optimum needs to push some air in front of it and disturb that sliding past it as it goes. If a pellet breaks the sound barrier it produces a sharp crack as the shock wave of disturbed air peels away from the nose and it travels with the nose in undisturbed air  dragging a wake behind it. The shock wave and redistribution of drag on the pellet form cause the flight to become unstable. It is further complicated when the pellet slows down and speed drops below the speed of sound. In an air rifle pellet the two events happen quickly so accuracy suffers.

It makes buying an air rifle advertised as being capable of shooting a pellet at 1200 or 1600 feet per second a nonsense. You will end up needing to shoot heavy pellets that the rifle can not push to super sonic speed but may end up with a hard recoiling hard hitting rifle that is hard to shoot accurately. Such rifles, especially spring powered, can be mastered with practice but are violent in their discharge but the laws of physics govern the pellet breaking the sound barrier.

The .177 pellet has the flattest trajectory and it becomes more curved as the calibre and weight of pellet increases. The bigger calibres have the advantage of greater pellet weight that carries its energy better at long range. The weight also makes them less affected by cross winds. Every pellet starts to drop from the intended flight path as soon as it leaves the barrel. The rate of drop which is caused by gravity is the same for every pellet no matter what its weight. 32 feet per second per second. The drop is a function of time and acceleration downwards. If pellets of different weights are fired from the same rifle or better still from a rifle of the same power and at the same target, the heavier pellet will drop more because the power available to propel it will make it travel slower than the lighter one. The heavier pellet will take more time to get to the same target and gravity will affect it for a longer time and pull it down further. From this it is said that a heavier pellet has a loopy trajectory. They all do have a curved flight path but heavy pellets, which are slower, more so just because of the extra time to reach the target. Accuracy is not affected because the setting of the sights and the point aimed at compensate for the curved pellet path or trajectory. 

We have talked about air rifle energy in the chapter on air guns and we have mentioned light and heavy pellets. A medium weight pellet in .177 calibre weighs about 8.5 grains: a pellet in .22 calibre about 14 grains. Grains is a measure of weight in the imperial system and there are 7000 grains to the pound and over 15,000 grains to the kilogram. In the metric system 8.5 grains is 0.6 grams. That is pretty light and you can not feel the weight in the palm of your hand. Just consider that a medium powered air rifle will shoot a .177 pellet at 800 feet per second. That is 545 miles per hour. Keep out of the way!

The little round steel balls called BBs fired out of unrifled guns derive their name from the size of the ball. By the nature of the ball and the gun barrel they are limited in absolute accuracy and range The guns have been produced since the start of air gunning and are still produced new by the timeless brand names of Daisy and Crosman. They are generally quite cheap but some of the specialty models are quite costly.
They have their place in recreational shooting. 

Be aware that a steel BB shot at a hard surface will rebound or richochet because on impact the BB deforms very little and impact energy is transformed to bounce. This is not so marked with a lead pellet because the lead deforms easily and the impact energy is transformed into heat. A very recently deformed pellet can be hot.

There can be just as much fun shooting a tin can with a lesser rifle as taking out the centre of the bullseye with a high quality rifle. However what ever rifle you are shooting a good quality pellet suited to the rifle will facilitate accuracy whereas a poor pellet will destroy it.

Pellet brands.  The commonly available ones.

 Webley Accupells.

These are advertised as probably the worlds most accurate air rifle pellet. In some rifles they might be but not in all. They are made of a hard alloy because the lead has some antimony in it. In .177 they weigh 7.9 grains and about twice that in .22. They are well made and neatly finished and come coated in a lubricant and are considered a very good pellet. The tin they come in has a screw top and is a good secure tin.

Crosman Premier.

These pellets are identical in appearance and weight to Accupels. They come in boxes of 1250. They come in two weights in .177 CPL (light) at 7.9 grains and CPH (heavy) at 10.64. That is a heavy .177 pellet. The boxes have the number of the die in which they were formed printed on the bottom of the box so one can assume that all the pellets are of consistent size. Experience has shown that in the box they are very dirty pellets and some production dust and shavings to be present. They need washing before using and possibly lubricating. The reputation of these pellets is compromised because they are produced in two grades. The boxes with the black stamped label are all made from the same forming die and are consistent in production size. The pellets in the box with the red production stamp are made in  several different dies and are not so consistently formed. The difference in quality commands a different price. 

JSB.

These pellets are made from soft lead. The skirts deform easily and form a good seal with the rifling. They come in two weights for .177 and for .22. In .177 8.44  grains and are called JSB Exact and 7.9 grains for JSB Express. They come in three head sizes 4.50 to 4.53 mms.  In .22 calibre they are 15.89 and 18.13 grains. >25 calibre are 25.39 grains.
These pellets are well regarded by air rifle enthusiasts.

Edgun.

These pellets are made by JSB and rebranded for the Russian specialty air rifle manufacturer Edgun. The pellets are available in the JSB sizes but are reputedly hand sorted for consistent production sizes, as all JSB pellets may be. Reports show that they are very good pellets.
 The difference in these seemingly identical pellets has been discussed to compare the two. That discussion is reproduced to give an understanding of pellet performance.

**I reckon that Edguns shoot just a little bit more consistently or maybe the word should be steadier. Then sometimes I think there is little difference.

##I have an inbox full of customers with that very same conclusion  ;D

**The faulty part of the test is the limitation of the shooter and the inherent inaccuracy of a mid range spring powered rifle.

##All Pellet comparisons should be done with a rifle that is tested and true. I have a lot of faith in all my rifles that at 25m (a good testing range) can stack pellets end on end until the pressure of the cylinder drops below the set regulated pressure.
All pellet comparisons should be done on an adjustable bench rest with little to no contact with the shooter besides the trigger squeeze. An indoor or windless day gives best results.
You need to take the rifle and shooter out of the equation to compare pellets properly.

**There are differences between the JSB and the Edgun. Parked side by side they look the same and my mechanical vernier rule can't really determine any  difference by measuring.
The inclined roll test shows  that JSB Exacts have a bigger skirt or a smaller head.

##My measuring equipment is tested and calibrated regularly and does a fine job of measuring pellets heads and skirts very accurately.  I can tell you that the JSB and Edgun Skirts are within the same tolerances but the heads on the JSBs are undersized to what the labelling on the tin suggests.
Does this make the Edgun pellet better? That depends on your rifles bore size and the velocity it spits it down range.. Again my inbox is full of emails from customers that will answer that question with a definite YES THEY ARE! [BETTER]

**Looking in the back that is up the skirt, the shape inside is different. That makes me think that the weight distribution of the Edguns is different to JSB. By design or just a change of forming die who knows. 

##Correct again, The Edgun brand on the left... the centre of gravity is indeed different on these two pellets.



**This is all very entertaining for the writer but the only test of any consequence is where the hole in the target appears.

##Then let me consult my inbox... this email review is from a customer. He used a non regulated .22 pcp on a windy day at 60m testing another 16gr JSB made Air Arms pellet against the Edgun 16 and 18gr pellets... I know its not a JSB labelled tin but still a JSB produced pellet and an interesting field comparison.

He used sand-bags and a leather butt rest, shooting off a shooting-table in a barn.
Fascinating! See attached results.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXxx


Winchester.

These are small light budget pellets made in New Zealand. They are cheap but quite adequate for short range backyard shooting of tin cans.

Gamo

These pellets are the most commonly available in New Zealand. They are available in a variety of head shapes and weights. The pellets are roughly finished and are truly a budget pellet with budget performance.
The brand includes a very light pellet made of an alloy known as PBA and are called Raptors. Because of their weight they enable very high muzzle velocity but are ineffective as a practical shooting pellet. A conscientious air rifle shooter will completely avoid them as they can cause damage to springs and piston seals in spring powered rifles.

There are other brands of air rifle pellets available, some of which are rebranded from the common manufacturers label. Some of them are very accurate and some not so. All air rifle pellets are cheap to buy when compared to even the small and affordable .22 long rifle ammunition so it is interesting to try anything that catches your eye (and your wallet) Most air rifle shooters experiment to find their favourite pellet and stick to that.   More than a few re- experiment; it is part of the fun and part of learning how to shoot.

The variety available is wide ranging: the choice is yours.

Pellet Shape.

Pellets are produced in a variety of shapes for the head. All of them are derived from three basic shapes but some borrow a little of one shape and add it to another in search of performance.

The three shapes are Flat head - domed head - pointed head, and some of these shapes have a hollow worked into the centre of the head.

Flat heads are used for low powered rifles seeking accuracy at short ranges. The flat head cuts a clean hole in the target to facilitate scoring the Target. The tend to become less stable in their flight at high velocities and long ranges.

Domed head pellets are thought to be the best all round shape. The domed is the most aerodynamic of the three and it performs well at higher muzzle velocity and retains stability at long range. It is considered the most useful pellet for hunting as well as target shooting and are the most commonly used.

Pointed pellets are designed to aid penetration into the target. In some instances the pellet can pass completely through a small animal. They can suffer aerodynamic instability especially if the point is slightly off centre of the axis of the pellet.
« Last Edit: June 06, 2017, 04:06:47 PM by Novagun »