Weak AR15 Trigger Spring for 7.62X39 Rounds

Motobie · November 10, 2008, 02:04 PM

Hi folks. I have an AR15 that is chambered for the 7.62X39 cartridge. When I use Wolf or any Russian steel cartridges, I would have at least one failure to fire out of a box of 20. Sometimes I would have three misfires out of a box. The indentation on the primer looks normal and deep enough. There are no misfires when I use American made brass cartridges. Stuff I buy from Remington and Winchester has been 100% reliable.

I have heard somewhere that a stronger spring would help solve this problem. Where can I get such springs? Do I need to do something else to make my AR more reliable with Russian ammos? Thanks for any help.

Scorch · November 10, 2008, 11:50 PM

I seriously doubt it's the hammer spring (you called it a trigger spring, but the trigger spring doesn't affect how hard the hammer hits the firing pin). My guess would be either the dimensions of the cartridge casing is very liberal to prevent problems chambering in dirty chambers, or the firing pin protrusion is very short on your rifle. Maybe both.

sadsack · November 11, 2008, 04:12 AM

I have the same problem with my AR. I used clymer head space guages when I chambered it, and it works fine with commercial brass loads. Is there a safe way to lenthen the firing pin protrusion? Or is there another solution?

SRG · November 11, 2008, 12:06 PM

Go over to AR15.com or M4Carbine.net and do a search or ask the question. It seems to me that I recall folks having to get longer firing pins if they were going to be shooting the Wolf stuff.

Motobie · November 11, 2008, 05:12 PM

Scorch, you're right. It's the hammer spring. I remember someone wrote about this issue saying that a stronger spring would help. I'm looking for a stronger spring but don't know who would sell that. A hammer spring replacement is a cheap and safe solution that's worth a try.

Sadsack, messing around with the pin is riskier and may have terrible consequences so, it's better to try a replacement spring first. So that's what I'm looking for.

sadsack · November 29, 2008, 02:50 AM

New spring fixed it. When I added adjustment tabs to the trigger and hammer, I bent the hammer spring to help lighten the trigger pull. I had forgotten about doing that. I had always shot reloaded or commercial ammo and had no problems, so I never even thought about the spring.

Thanks for your help.

November 10, 2008, 02:04 PM	#1
Motobie Member Join Date: May 12, 2007 Posts: 40	Weak AR15 Trigger Spring for 7.62X39 Rounds Hi folks. I have an AR15 that is chambered for the 7.62X39 cartridge. When I use Wolf or any Russian steel cartridges, I would have at least one failure to fire out of a box of 20. Sometimes I would have three misfires out of a box. The indentation on the primer looks normal and deep enough. There are no misfires when I use American made brass cartridges. Stuff I buy from Remington and Winchester has been 100% reliable. I have heard somewhere that a stronger spring would help solve this problem. Where can I get such springs? Do I need to do something else to make my AR more reliable with Russian ammos? Thanks for any help.

November 10, 2008, 11:50 PM	#2
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	I seriously doubt it's the hammer spring (you called it a trigger spring, but the trigger spring doesn't affect how hard the hammer hits the firing pin). My guess would be either the dimensions of the cartridge casing is very liberal to prevent problems chambering in dirty chambers, or the firing pin protrusion is very short on your rifle. Maybe both. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

November 11, 2008, 12:06 PM	#4
SRG Member Join Date: October 12, 2005 Location: Prescott, AZ. Posts: 73	Go over to AR15.com or M4Carbine.net and do a search or ask the question. It seems to me that I recall folks having to get longer firing pins if they were going to be shooting the Wolf stuff. __________________ Gunsmith/Machinist

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November 11, 2008, 04:12 AM	#3
sadsack Senior Member Join Date: February 4, 2006 Posts: 206	I have the same problem with my AR. I used clymer head space guages when I chambered it, and it works fine with commercial brass loads. Is there a safe way to lenthen the firing pin protrusion? Or is there another solution?

November 11, 2008, 05:12 PM	#5
Motobie Member Join Date: May 12, 2007 Posts: 40	Scorch, you're right. It's the hammer spring. I remember someone wrote about this issue saying that a stronger spring would help. I'm looking for a stronger spring but don't know who would sell that. A hammer spring replacement is a cheap and safe solution that's worth a try. Sadsack, messing around with the pin is riskier and may have terrible consequences so, it's better to try a replacement spring first. So that's what I'm looking for.

November 29, 2008, 02:50 AM	#6
sadsack Senior Member Join Date: February 4, 2006 Posts: 206	New spring fixed it. When I added adjustment tabs to the trigger and hammer, I bent the hammer spring to help lighten the trigger pull. I had forgotten about doing that. I had always shot reloaded or commercial ammo and had no problems, so I never even thought about the spring. Thanks for your help.