Main Spring Busted

It was two weeks ago. A few of us went plinking and the agenda for the day was “shoot, shoot and shoot” 🙂 . After a lot of casual pinking came the serious part. I was very determined to hit the bulls eye and at a very descent distance. I leveled my rifle….set my sights….was very confident that the result of this shot would be the bench mark to follow for the day. As I squeezed the trigger, apart from my finger, my whole body froze momentarily to ensure the least possible deviation of my aim and ……Bang!!! A loud noise from my gun just like a .22 hornet. That wasn’t right. I knew it was not supposed to sound like that. I instantly knew for sure that this sound spelt bad news. This bang was very abnormal unlike the others before it. Everyone’s face turned to me with a big question mark. On opening the breech area of the BAM B40, the rifle in question, I found the pellet stuck close to the breech washer which caused a blank fire. Intriguing indeed! I still don’t have a clue how on earth this happened.

After removing the pellet, I went ahead and shot a few more rounds. I noticed that the firing cycle not as smooth as it was earlier. While cocking the gun, one thing was obvious. While pulling the under lever to cock the gun, the immediate resistance had reduced by about 3 to 4 inch. I could also feel some metal friction. It dawned on me that the only explanation to this sound was a broken spring. What was interesting however was that the Point of Impact of the pellet had not changed.

Back home and a week later, I at last fond time to dismantle the gun over the weekend. And yes, exactly what I thought. The spring was busted. What surprised me though was that the spring wire was fat and one could never have guessed that one blank shot could have caused this. Perhaps the spring was highly stressed due to buckling as the stock guide was not a good fit for the spring (please refer to the topic “Spring Guide! What is it” for a better understanding on this subject), or the stress was not properly removed during the spring manufacturing process.

Spring Busted

The Seal seemed to be okay. Not a single scratch could be found.

Seal Profile view

I have now replaced the seal with an Apex seal but could not find a replacement stock spring. I’ll soon have one custom made for a perfect fit. The existing stock spring has a 3.32mm wire dia. The spring I have designed will have a 3.2mm dia to get more tensile strength while simultaneously softening the cocking effort.


6 responses

  1. > Chinese Spring – is it?
    > Yes. It’s a case of improper removal of stress.
    > Would a spring ‘Front Guide’ made of a resilient polymer have saved the situation?
    > Best wishes for ur spring – interested to know the outcome.

  2. Good thought! May be yes Not sure tough, just little of cushioning can absorb that spring force of nearly 340 lbs?

  3. A bit of research which confirms me that stock spring of B40 that is where wire diameter is 3.32 is not at all a proper spring. A bit of change ID will heavily effect on tolerance thus failure of spring’s intended force.

  4. Cant believe yor BAM’s down. The gun was a real pleasue to shoot. Hope she gets well soon 🙂

    1. It was broken then also when you are testifying the gun. You couldn’t understand because you are unaware about the smoothness it had.

      By the way, I have installed a new spring. Will share the review.

  5. Hi,
    > What make of new spring did you install? Was it easily available in the market?
    > Did U also change the spring guide?

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