mainspring help

[masterangler-01]

I tried searching for this and couldn't find anything. I just got my receiver back from Pete, and was wondering where do you start from to shorten it. Also how do I know when I have the correct length.

[weasel_master]

Trim until you can charge the gun without having the spring bind. I think I'm around 17 coils. Then fire off a round and see if it ejects. If not, cut a little more off. Keep going until it ejects properly.

[JBaum]

The spring has to be short enough for the ejector button on the rear of the bolt to have a good hit on the buffer nose. Remember that the buffer is spring loaded, and should be able to compress a little, so a little extra needs taken off once the spring is short enough to allow the button to hit and the buffer to compress. Keep it as long as possible, but short enough to work without the bolt smashing the spring together when the buffer compresses. You can get very close to the correct length by using the cocking handle to cycle the action with an empty shell in the bolt face.

It's an individual thing, that has to be matched to the gun. There is no single answer to your question.

[hcpookie]

Do we know the poundage that a main spring needs to work in SA? I've always read "use X number coils" but have never heard how many pounds the spring must be. Obviously there is a weight range, not a certain poundage, and I'd be curious about that. That would certainly help us determine if and when a spring is nearing the end of its life...

[masterangler-01]

Thanks for the help guys.

[Pirate]

Do we know the poundage that a main spring needs to work in SA? I've always read "use X number coils" but have never heard how many pounds the spring must be. Obviously there is a weight range, not a certain poundage, and I'd be curious about that. That would certainly help us determine if and when a spring is nearing the end of its life...

Personally I think it is a good idea to just get a new spring, they are cheap and readily available., specially if you are using one of the kits from angola that have a mix of used parts.

[tony]

Has anyone tried using a double spring set up? A smaller dia. spring inside the orig. to help take up the lost coils and aid in moving the extra weight. I'm just talking out loud, I've just begun looking into this build. Maybe getting a beefier main spring built to specs by a spring company.

[JBaum]

I see the problem with a second spring being where would you put it? The ejector button on the rear of the bolt has to hit the buffer head to eject the shell, so there's no room on the inside of the recoil spring.. There isn't enough room on the outside of the spring - so I don't see where it could fit.

[tony]

I see the problem with a second spring being where would you put it? The ejector button on the rear of the bolt has to hit the buffer head to eject the shell, so there's no room on the inside of the recoil spring.. There isn't enough room on the outside of the spring - so I don't see where it could fit.

I see what you mean. Thanks for the insight. Would you know what the original spring pound be for the main spring, and length in the receiver compressed and released?
Thanks for any info.

[JBaum]

I see what you mean. Thanks for the insight. Would you know what the original spring pound be for the main spring, and length in the receiver compressed and released?
Thanks for any info.

Can't help ya there - I "only" have a full auto ,
and dimensions for a semi would be different.

[bolex]

1)One way you can tell how short your spring needs to be is to press the coils togather and measure that height (known as the solid height of spring). I would place a rod in the center of the spring and compress it. Measure the distance that the spring has to fit in between the bolt and the buffer and make sure that the spring will fit in that space when the bolt is fully back. I'm sure that additional space will be needed for the buffer compression which you can find by compressing the buffer in a vice. I saw that somewhere in the forums. The spring will have to have these additional coils removed to permit the buffer to function. Cut some of the spring coils off and re-measure the solid spring height and match that to the space allowed by the new bolt extension. This would be the most accurate method and give the most spring left after cutting.

2)Or measure the bolt extension length (the change in bolt length) the coil "wire" diameter and divide the coil wire diameter into the change in length, this number could tell you the number of coils that have to be cut off.

Bolt length change/wire diameter = number of coils to cut off.

This would be the easy method but would not be optimized for your weapon.

[striker754]

Trim until your gun ejects reliably. That's how long it needs to be. Simple.

[masterangler-01]

Striker I understand your philosophy but where do I start trimming? How many coils is a good/safe starting point without cutting too much off too soon.

[striker754]

YOu'll probably need quite a few depending on what ammo you use. Its been forever since I touched mine so I couldnt help you with a number. Cut 2 or 3 off and see what it does. I know I cut way more than that off. Yugo ammo still doesn't eject right. Romy does though

[masterangler-01]

Thanks Striker.