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Posted: 5/6/2010 1:35:21 PM EDT
I bought an AM15 upper for the M16 and it uses an open bolt FCG. Can I just put the 5.56 upper back on and use it open bolt like the Colt light machine? If so does it use a special bolt or carrier? Thanks
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For the AM15, yes.
The 5.56 open bolt group includes bolt, bolt carrier, hammer, trigger, modified auto sear, and some new, extra parts to achieve open bolt operation. There's a Colt open-bolt conversion setup offered for sale on gunbroker with a complete upper, buffer and FCG. Bids start at $3990, with a buy-it-now of $4900, and the seller claims there are only about 20 fcg's in private hands anywhere in the country. http://www.gunbroker.com/Auction/ViewItem.aspx?Item=167113773 |
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Colt probably holds a patent on the open bolt system, which would preclude anyone but them from making them.
They've shown their love for the civilian market many ways in the past... 
If more conversion parts were available, it's questionable whether they'd be used. The system is reportedly VERY hard on the lower receiver, which isn't a big deal for the military or LE, but a huge risk for the owner of a transferrable. |
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Shrike is closed bolt. Although the inventor mentioned about having a firecontrol setup where semi was closed bolt and full auto would be open bolt. He mentioned this when the Shrike was introduced in the SAR magazine. I think around 2001. I don't think he ever produced those firecontrol parts though.
My Shrike works perfectly. Don't mind the closed bolt either. Shoots really smooth. I personally would never want to run my factory Colt registered receiver in open bolt even in 22LR. I had a deposit on the AM15 but when I found out it was going to be open bolt only I got out immediately. |
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Quoted:
Shrike is closed bolt. Although the inventor mentioned about having a firecontrol setup where semi was closed bolt and full auto would be open bolt. He mentioned this when the Shrike was introduced in the SAR magazine. I think around 2001. I don't think he ever produced those firecontrol parts though. My Shrike works perfectly. Don't mind the closed bolt either. Shoots really smooth. I personally would never want to run my factory Colt registered receiver in open bolt even in 22LR. I had a deposit on the AM15 but when I found out it was going to be open bolt only I got out immediately. The AM15 isn't too bad. The lower doesn't do anything when firing except release the bolt so only the pivot and take down pins are under stress. |
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Quoted:
The AM15 isn't too bad. The lower doesn't do anything when firing except release the bolt so only the pivot and take down pins are under stress. I'm not concerned with the release of the bolt. It is stopping the bolt that is the issue. I know its only a 22LR but you don't have that forward energy being forced on the hammer like on any closed bolt setup. Regardless, the AM15 has bigger issues. It was submitted to ATF to be used w/ the Factory Colt LMG open bolt FCG but they were shipped without the 'sear release' since it is using a FIXED firing pin and firing from an OPEN BOLT........ Study how a real Colt open bolt works: look at the patent: http://www.google.com/patents?id=BEkxAAAAEBAJ&zoom=4&pg=PA3#v=onepage&q&f=false In a real Colt LMG Open bolt setup the firing pin is floating not fixed (just like a regular closed bolt M16). The hammer does hold the bolt back like the AM15 and that is where the similarity ends. On a Colt, the sear release is tripped by the carrier just like a closed bolt and the hammer is released to hit the firing pin. On the AM15, the hammer never gets to go forward, it just bobs up and down to grab the bolt....like how an open bolt UZI or most other open bolt SMG's. |
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Quoted:
Quoted:
The AM15 isn't too bad. The lower doesn't do anything when firing except release the bolt so only the pivot and take down pins are under stress. I'm not concerned with the release of the bolt. It is stopping the bolt that is the issue. I know its only a 22LR but you don't have that forward energy being forced on the hammer like on any closed bolt setup. Regardless, the AM15 has bigger issues. It was submitted to ATF to be used w/ the Factory Colt LMG open bolt FCG but they were shipped without the 'sear release' since it is using a FIXED firing pin and firing from an OPEN BOLT........ Study how a real Colt open bolt works: look at the patent: http://www.google.com/patents?id=BEkxAAAAEBAJ&zoom=4&pg=PA3#v=onepage&q&f=false In a real Colt LMG Open bolt setup the firing pin is floating not fixed (just like a regular closed bolt M16). The hammer does hold the bolt back like the AM15 and that is where the similarity ends. On a Colt, the sear release is tripped by the carrier just like a closed bolt and the hammer is released to hit the firing pin. On the AM15, the hammer never gets to go forward, it just bobs up and down to grab the bolt....like how an open bolt UZI or most other open bolt SMG's. It is an "open bolt" setup with fixed fireing pin and sans sear release but, the bolt is caught at the beginning of it's forward travel (about 1/8 inch of forward travel when caught). I don't belive we'll be seeing the "My RR lower was damaged by my AM15 upper" threads in the future. I did install KNS pins though. 
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