ted's hardware

A real gas-eater…

At 10 years, she is the oldest but most fun pellet shooter in our collection. Constructed from iron and wood, this rifle is tough and does not forgive. This article will give some tips how to crank up the muzzle velocity.

First some specs:

Pressure system: 12 gram Co2 capsule
Load system: semi-auto, pump action
Caliber: 177 (4.5 mm)
Total length: 97 cm
Barrel: Precision rifled steel
Weight: 2,9 kg
Safety: Manual safety switch
Muzzle velocity: .177 – 170 m/s (PBA – 190 m/s)
Sight: Standard iron sight
Mag: Build in mag, 14 pellets

First look

I had no idea how to start, as far as I know nobody tried to boost up a G1200 before. There are weapon specialists who can crank up the speed but ask ridicules high prices.

First step is to open her up. There are only 5 screws holding you back.

The inner work is really simple and basic. Most parts are made of iron which makes it very durable and reliable. The only problem that can occur is when loading pellets; they might get stuck in the loading mechanism. There is no real solution for this. Make sure to check your pellets for any damages before loading or try the Gamo Round pellets (8.14 Grain).

The main components are the gas cylinder (1), the pressure spring (2), loading mechanism (3) and the trigger part (4). There is an overload system (5) present in case of jams which works like a charm.
In armed condition, when the trigger is squeezed, it releases the heavy slammer tube which slams onto the ‘gas cylinder’s release needle’. This needle, when pressed, will release a small amount of gas into the main shaft propelling the pellet. To increase the speed of the pellet I made the following three modifications:

Mod 1 – Suppressing the spring

By suppressing the spring with a small iron tube, it will give the spring more tension and therefore more force. I tested a few lengths of tube and came to the conclusion that a length of about 2 cm will give the best result. When the tube is too long, the spring is compressed and releases an excessive force which can result in a damaged gas cylinder. However a tube which is too short won’t give the maximum result

Mod 2 – Broaden the main shaft

When gas is released, it travels through the main shaft into the barrel. Let’s say the shaft is the bandwidth of your internets connection. The more bandwidth, the faster it travels. Therefore I drilled the shaft 0.6 mm more wide, giving it just a bit more space.

Mod 3 – Extending the part that keeps the slammer tube for going too far

When the slammer tube is released, it smashes into the gas needle. There is a long iron bar which takes away a bit of the force on the needle. Of course, this has been done to protect the needle. However I pushed it more to its limit by extending the part with 2 mm.

Some photos of the mods:

Some facts after modding:
- uses more gas
- louder bang
- more nozzle fumes
- more maintenance

These modifications made the Gamo shoot over 250 m/s. It also gained a new nickname: Der Nebelwerfer. Normally you would not see much muzzle fumes, but with these modifications you will see a muzzle fume of about 40 cm! This made it also tricky to measure the muzzle velocity because the fumes interfered with speedometers mounted on the barrel. Luckily we could measure it using a shooting Chrony.

There is only one downside to these modifications; it will use 5x more gas than by default. I am able to shoot one clip (15 pellets) with one 12 gr CO2 capsule. In original condition one capsule is enough for 5 clips.

If you don’t mind a louder bang, big white fumes and the smell of CO2, then these mods might be something for you!

Coming up soon: how to make a full auto shooter of your Gamo 1200!

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