Thursday, August 17, 2017

Shooting a spring powered air rifle


To an Airgun Friend
I was aked the other day why an airgunner could not shoot his new Gamo and well as his "Old .20 caliber".   This is my response.


Those .20 caliber pump air rifles of our youth were the high point of American air rifles, and they still influence our approach to air rifles.

Those air rifles shot with a simple mechanism. A spring and a hammer are retained by a trigger. Release the trigger and the hammer strikes the firing valve stem, opening the valve, and air rushes into the barrel, propelling the pellet out the barrel. The power came from a pump built into the rifle. The pump pressurized the air before the shot is fired.

A century of shooting these air rifles left American airguners with a sense that an air rifle was like a scaled down .22 rim fire.  Now that spring/piston airguns have become popular, that sense has been challenged. With spring powered guns, like your Gamo, some new shooting techniques are needed for good results.



Spring/piston airguns have an entirely different firing cycle. They carry their pump behind the pellet rather than under the barrel. Well before the shot, a spring is compressed behind a piston. The spring drives the piston to compress the air after the trigger has been released. There are no valves, just two seals that only hold pressure for micro seconds. This is an elegant system, but elegance comes with a price.


The pellet doesn’t leave the barrel before near the end of the piston’s stroke. The piston can bounce off a rebounding wave of compressed air near the end of the compression cycle before it is finally stopped by the end of the cylinder.  This sets up forces that weren’t there in that .20 pump air rifle, and they all happen before the pellet leaves the barrel

You can shoot that .20 like a .22 rim fire. Hold it firmly from trigger squeeze to follow through. Steady the rifle on a tree trunk or a fencepost and it will reward you with a good shot. Shoot a springer that way and your heart will be broken. Springers aren’t bad. It only means that your shooting technique has to accommodate the springer’s Newtonian world of action and reaction.

Isolate the action reaction cycle with your hands. Grasp the rifle lightly. Let it pulse in your hands during the shot cycle. Don’t rest it on a hard surface unless your hand is between the gun and that surface. Generations of airgun hunters and plinkers in Europe have done excellent shooting with spring piston airguns, and you will too.

Good shooting,

Ron

Wednesday, March 29, 2017

Arimo Dave's question

Arimo Dave had a question about my 30 shot group:


Ron,
So, did you get all thirty shots off in 25 seconds?  😜

One question I have is why are your velocities a bit on the low side?

Dave.


My response:

25 seconds is a milestone yet to be achieved.

Velocities started out at in the 850 860 range which is said to be ideal though the pellet in those statements are usually 18.1. I an out of 18.1s right now so I used the 15.8s. This barrel is suppose to be tight and velocities should be expected to go down.

I have not re-tuned the gun since installing the barrel. The thirty shot string was suppose to be the first step i re-tuning. Next time I'll try 3, 10 shot strings.

Tuesday, March 28, 2017

JSB 16.89 pellets in the Marmot Militia barrel

My plan was to shoot 30 shots at a single target and measure the velocity of each shot.The velocity part didn’t work out,but the 30 shot group blew my socks off.

What first caught my eye was the roundness of the group even with an extreme spread of over 50 feet per second. 



I used a target Arimo Dave made to represent the short range stang shooting target used in Norway. Dave made this target to be set at 30 yards, so that is where I paced it. Score is hit or miss and hits within the white line are used like an X count for breaking ties. The target measures 1.5 inches across at the base.


All sots went into hole .8 inches tall and 0.7 inches wide. Cross wends and dropping velocities egged it out a little. My chronograph did not record all the velocities, but looking at the screen I saw a high on 861 and the last shot was 511 fps.The starting fill was 2700 psi. Measuring the group center to center I get 0.58.


Watching the each pellet rise vertically and disappear through the hole in the target was nothing short of confidence inspiring. This may well be the most consistently shooting airgun I have. I am looking forward to shooting it in our 16 target speed silhouette shoot and our 32 shot sporting rifle match.


I shot this group from the bench with a scope. When we shoot this target it will be in position and with iron sights. Stay tuned to http://idahoairguns.blogspot.com/ for the match results.

Ron

Thursday, March 23, 2017

First groups with Marmot Militia .22 hammer forged barrel

Target is a 50 foot international small bore, A-36


I have been shooting JSB 18.1 pellets getting ready to shoot the silhouette speed shoot form EBR. With our monthly club benchrest match I found that I only had about 30 left. I went through my pellet supply and found JSB 15.89, BSA 16 gr Wolverines, and Baracuda Match.  All good candidates for for my new barrel.

I shot 2, 5 shot groups with each pellet. This would let me see if there was going to be a change in point of impact over a 30 shot string.

JSBs really stood out with a 0.45 and a 0.28 inch groups. All the rest were grouped around 0.6 inch. Only one group hit the one MOA criteria, and we will have to see how it holds up in further shooting. All the pellets were lubed with Wixson's honey.  

At the end of 30 shots I shot 6 ⅕ chickens at 25Y to see if the POI had changed. All six hits were in the center of the chickens. This suggests 40 shots from one fill !!!!

Ron

Monday, March 13, 2017

Marauder Field and Target

Chickens at 25 yards. Four hits on the leg and one body hit after adjusting the elevation. These are the same size targets as Extreme Benchrest. 



Crosman announced that they were addressing the .22 barrel situation at about the time I bought a Marmot Militia barrel for my .22 Armada. This barrel along with a regulator was going to become available in a new Marauder variant called the Field and Target.


This has happened to me before. I converted a 1760 to compressed air just in time for Crosman to announce the Discovery which filled to a higher pressure and cost $100 less than my conversion.


This week, Crosman sent an email to an airgun forum poster saying that they were not “moving forward at this time” on the Field and Target.


When the Field and Target was announced at the Shot Show in January, the wise posters felt that the new rifle wouldn’t be for sale until April or May, I don’t think this affects my decision to buy an aftermarket barrel. Also I would not be surprised if the new Crosman barrel didn’t show up as a replacement part for six months after the release of the new rifle. I plan to shoot the Armada at Extreme Benchrest, and I need to practice with it starting as soon as the receding winter snowpack lets me.


By the way, the new barrel form Marmot Militia is looking very good.

Pigs at 35 yards. Left two shots. Right three shots.


Ron

Wednesday, March 1, 2017

Installation and first shooting of Hammer forged barrel



The new barrel arrived all shiny and bright and I re-read Jim’s web site where he guaranteed ½ inch groups at 60 yards. This would put the Armada at the top of my airgun totem, and make me a fulfilled air gunner.



My new toy won't do all those wonderful things if I don’t install it and the time had come to face what ever wrenches and o-rings and other defugalities stood in the way of soothing my super gun to be.


The Armada is a special case because I had to take the hand rail off before I could remove the stock from the air cylinder and barrel assembly. I did this once before when I tuned the rifle. Getting the stock off resembles a wood block puzzle, and is not hard as long as you remember that the first step in to remove the tiny set screws under the front of the hand rail. This screw secures the bracket that goes around the front of the air cylinder.


Barrel installation is not hard or time consuming. Set aside enough time to do the job without being rushed. I spent two hours on it and that includes cleaning the barrel once before installation and once after function firing it 20 times into a snow bank.to make sure the magazines worked OK.


All back together I had to see if the $210 was going to pay off. I could shoot across 50 yards of snow to a spot where I had some metallic silhouettes set up.  I mounted the Center point 4-16 scope that came with the rifle. Shooting Hunter Field Target style with a seat and a bipod, I sighted in and hit 6 chickens with 6 consecutive shots. On a steel plate I shot a 4 shot group that measured slightly over ½ inch. This barrel is going to earn its keep,


The next day it snowed 21 inches and canceled our benchrest match.


More to come.

Ron

Thursday, February 23, 2017

Why mod a marauder?



Nothing attracts aftermarket parts like a successful product. The AR-15, Ruger 10-22 and the 1911 pistol are popular rguns with good designs and engineered for mass production they are naturals for add on parts. Add CANC machinery and an industry is borne. Zowee!

The Benjamin Marauder, Crossman’s flagship precharged air rifle, is the most popular precharged air rifle in America. The Marauder shoots well, has great features and is user adjustable to fill many airgining roles, but it has an Achilles heel. The .22 version suffers from indifferent accuracy. Some shoot well often grouping into one inch at fifty yards, and others couldn’t hit a two pound coffee can at that distance. The rest are somewhere in between, and is seems to be a function of the barrel. It is really unknown what the overall average accuracy of .22 Marauders is. I think that overall customer satisfaction wasn’t high, the Marauder would not be as popular as it is.

Twenty two caliber air rifles have been Crosman’ bread and butter since their first air rifle in 1923. The Armada I shoot is a winner if the “barrel lottery” with 50 yard groups seesawing between ¾ and 1 ¼ inch.

Owners of Marauders/Armadas are spoiled for choice by the aftermarket parts selection. We are always thinking, “What part would turn my air rifle into a super gun”?
I chose an aftermarket barrel because accuracy was my priority. Other parts can increase the power, or extend the shoot count. Most of my shots are taken at 50 yards and further. Every time I shot a ¾ inch groupe, I said,”Why can’t I do this every time”?

Next time, Well Ron, how does it shoot?