Indians For Guns

I made some modification on my airgun to increase stroke length by almost 12mm. Earlier the stroke length of the airgun is 7.5cm. After the mod the stroke length increased to 8.7 cm which is approx 16% increase in the swept volume.
Caution to our fellow members: Those who are not willing to take risk or not confident with what they are doing..plz dont spoil your gun.
Level of skill required: Medium
Tools required:Mill Flat file(b@$*@*d) double cut, Fine, friendly neighborhood welder, emery sheets, some damaged HSS drill bit(2 or 3mm dia).
1.The first and foremost task is to determine the distance between the piston and the cocking slot hole. This will give the maximum possible increase in stroke length. Do not worry if the steel piston is behind this hole. The washer lip should be above the hole to compress the air.

2. You must shorten and strengthen the piston sear. Higher compression of the spring leads to higher stress on the sear. Start filing the piston rod atleast 1 cm similar to the existing slot. In this case I filed around 12mm to half-round and welded the rear portion by 12mm. This makes the sear shorter by 12mm. Inorder to improve the wear resistance I welded a drill bit on the sear hence it can maintain higher spring stress. The extra length were cut-off and sanded down with emery sheet.
3. Dry set your gun means do not put the spring. Just put the piston and the trigger set inside and try to cock the gun. I have found two issues here. The cocking arm is short by 2~3 mm to lock the sear after filling sup some material in the piston cocking slot. Manually push the piston down to lock. Later try to lock the barrel to the breech. I found the piston slot on the top preventing the cocking rod to come back. The clearance needed was about 4mm. Note down your observations.
4. Extend the cocking arm. I welded some extra material on the cocking rod where it pushes the piston down. The extra material is around 5mm in length. using a flat file carefully match with the existing "T" shape slot. Once done remove the material from the other side by 4mm. This makes a gap between piston top slot and cocking arm when locked.
5. Check for any obstructions during cocking. I had an obstruction with a barrel touching the receiver, so I cut a groove 2mm in depth and 2 mm wide.
6. Fix in your stock and check any wood material is obstructing the movement. If any chisel as necessary.

Comments & suggestions welcome.

Happy modding,
Vijay

great job Vijay......which gun is this.....what is the volume now and what was it before..after firing about 100 odd shots please let us know the increase in fps.....also, have you retained the same spring?.....

regards

p k jeetesh

I dont have much time to do further enhancement. Earlier the stainless steel welded sear got sheared off and I have replaced with HSS drill bit. Here is the picture. Once the gun is back to shape I will post with some more details.

Congratulations. Fantastic work.

M.

Thankyou all.. I am using the same spring at the moment which is a lot canted as the spring guide thickness is less the ID of the spring. After welded with drill bit I yet to put together and test the rifle. It will be done by this week. I have soaked up few leather seals which will be tested along. There is less twang and recoil as the spring compresses more. Irrespective of the spring power the optimal compression is 90% of its compressible length. Hence few washers will be added to get close to 90% of the spring compression. In a day or two the barrel will be cut by 1 or .5cm for recrowning. I am currently making some changes in the trigger to resist sidewise play. This is the main culprit for the accidental fire and unpredictable lever travel. Also using stronger trigger spring with radial sears will make the locking system positive,smooth and longer trigger pull.

Cheers
Vijay

Coool Job man, well done.

What is ur Airgun make, Is it IHP

sa_ali wrote:Coool Job man, well done.

What is ur Airgun make, Is it IHP

Its model 35 commando.

Final Update: All set except the locking bolt which will be fabricated. The accuracy is no good as I have replaced with 6mm allen bolt with shim. The stock is stripped for rose-wood stain and matt wood finish. As you can clearly see the broken stock joined by brass screw. The crack line will disappear after adding the color and putty. The power is bit high now and finally the gun performs to my taste. Cocking is smooth and no auto fire. Trigger is lighter and crisp but not comparable with 2 stage but breaks without any effort. Other areas to be improved could be replacing the compression tube with custom seamless tube with maccarri spring and apex seal . But I could make a much powerful and efficient design . The barrel is poor so its not worth the effort. Tommy, IHP gun owners can try to make long and powerful compression tube as the barrel quality is good.
Break open the barrel and look at the angle cocking slot engages with piston Maximum travel to engage the sear. 12~13mm more travel Coconut shell cracked in three shots.
Contact me if anybody willing to increase stroke / improve their airgun. I am ready to help .

Cheers,
Vijay

Excellent job guruji.
Hardly can see anyone devoted to improve the Indian toy and more so share piece by piece to us. Hats off to you!

tirths wrote:Excellent job guruji.
Hardly can see anyone devoted to improve the Indian toy and more so share piece by piece to us. Hats off to you!

Thankyou sirji.. But i am certainly not a guruji in airgunning. Just last year november I start using airgun. Somehow the brands which I have come across are pretty poor including IHP. The internal dimensions are way off and also the performance. I just tried to improve these areas to make the gun consistent to shoot. These are not exotic materials so anybody can dismantle without fear and start working provided they are confident with what they are doing. That is why i am telling everybody this is not a difficult task to achieve. I am representing each and every changes made in my gun so that if anyone interested can take up the job. Also cost wise its pretty damn cheap. Apart from my experiment expenses, I will provide the actual cost breakup.

cocking arm extension - Rs 10
Honing the cylinder - Rs 100 (I could have done better than him)
broken stock fixing - Rs 45 (epoxy, brass screw)
New spring - Rs 150
Barrel slot cut for cocking - Rs 10
shortening the piston sear - Rs 80
minor improvements in trigger- Nil
leather seal - Rs 2 (Kerosene stove no.3 washer)
butyl breech seal - Nil

Regards,
Vijay

airgun guru Vijaycool ji If you have used JM seal Results would have been far better rest tirths can tell about that .

jaz wrote:airgun guru Vijaycool ji If you have used JM seal Results would have been far better rest tirths can tell about that .

Apex seals are good to coverup the cylinder ovality and slight irregualarity. But i am not sure it will cover the air leak due to the seam. This is the only culprit now in that airgun

Guys..I dont have this gun anymore . She is beautifully dressed in Rosewood finish and given to my in-law. He is trying to figure out the crack in the stock. Nobody could able to identify the broken stock. He is a happy person and everyone tried the gun commented about the power. Its really powerful beast relubed with some Moly and reasonably accurate. I edited by mod. It can zip through thick Pesticide tins at 15 yards. My hunt for another gun begins ofcourse it will be modded .
I really can not forget my first gun. She taught me how to shoot and also how to repair. It will be very hard to find a gun like this which gave some problems in each and every areas such as broken stock, Improper compression tube, Key-holeing barrels, slipping sear and so on.. . This gave me the encouragement and made me open the gun and work on the defective areas and understand the concept of airgun..Thankyou and bye--bye--baby.

Happy shooting,
Vijay

Great Post Vijay!

Good Going Vijay..in-laws..vow arent they the ones who should be getting you say IHP o rmay be return the gun..LOL

Do post often...about ready to go for Diana et al are you member of any shooting club do become one?...good luck

Best