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Posted: 9/30/2015 8:16:32 PM EDT
Hey all, does anyone know if on the early RPB mac 10's open bolt semi-auto's if it's just the bolt & upper components that allow it to fire from an open bolt or does the lower receiver frame any different from a closed bolt SA Mac???
Also is obtaining a lower flat and jig to bend & weld lower considered the same as an 80 or 100% AR lower, meaning ok to build and have with no serial #, I'm in a state where pistols/rifles are not registered.

Thanks Jim
Link Posted: 9/30/2015 11:00:49 PM EDT
[#1]
IIRC the open bolt and closed bolt semi receivers are different. Something about a different type sear block attached to the inside of the receiver so it's impossible to fit a FA upper. I might be wrong it's been a long time.
Edit: lower receiver.
Link Posted: 9/30/2015 11:41:48 PM EDT
[#2]
No.. Lower Too.
Link Posted: 10/1/2015 9:23:35 AM EDT
[#3]
Ok so it's the OB lower as well that's different, on the flats they all look alike. But I think the m10 45 & M11-9 RPB's are the same lower, it just the M11a1 380 that's smaller in width I believe.
Link Posted: 10/1/2015 5:00:40 PM EDT
[#4]
The fire control parts on the OB lower is instead on a U-channel that is welded to the lower so the FA parts cannot be installed.  Otherwise, all the parts are the same as the SMG.
Link Posted: 10/1/2015 5:16:17 PM EDT
[#5]
I found out today it's call a sear carriage the SA open bolts have welded into the frame. So this idea I had is going no where. Back to finding a decent open bolt SA for a realistic price.
Thanks guys.
Link Posted: 10/2/2015 10:44:36 PM EDT
[#6]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I found out today it's call a sear carriage the SA open bolts have welded into the frame. So this idea I had is going no where. Back to finding a decent open bolt SA for a realistic price.
Thanks guys.
View Quote


Building a new OB Semi-auto is illegal and a good way to end up in prison.
Link Posted: 10/3/2015 7:44:01 AM EDT
[#7]



Discussion ForumsJump to Quoted PostQuote History
Quoted:
Building a new OB Semi-auto is illegal and a good way to end up in prison.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:



I found out today it's call a sear carriage the SA open bolts have welded into the frame. So this idea I had is going no where. Back to finding a decent open bolt SA for a realistic price.



Thanks guys.

Building a new OB Semi-auto is illegal and a good way to end up in prison.
Yeah I'll +1 that. Nothing wrong with learning but I got the impression it was a project idea. I've seen a couple for sale before locally for probably $500-$600
 
Link Posted: 10/3/2015 10:45:17 PM EDT
[#8]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Yeah I'll +1 that. Nothing wrong with learning but I got the impression it was a project idea. I've seen a couple for sale before locally for probably $500-$600  
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
Quoted:
I found out today it's call a sear carriage the SA open bolts have welded into the frame. So this idea I had is going no where. Back to finding a decent open bolt SA for a realistic price.
Thanks guys.


Building a new OB Semi-auto is illegal and a good way to end up in prison.
Yeah I'll +1 that. Nothing wrong with learning but I got the impression it was a project idea. I've seen a couple for sale before locally for probably $500-$600  


OB macs are not $500-600 I'll buy 10, they sell on avg $1500.00 & up. unless completely hammered.

and my idea was to find an existing lower but had to be sure between rpb, swd/cobray what the lower receiver differences where if any bc I found complete new OB upper parts kits less barrel & receiver. If I buy an existing lower it's not considered a new OB SA build. the lower I saw for sale was closed bolt, no sear carriage, so wouldn't have worked or been legal with that used lower.
My total cost would have been $700 instead of $1700 cost.
Link Posted: 10/3/2015 11:40:20 PM EDT
[#9]

Discussion ForumsJump to Quoted PostQuote History
Quoted:
OB macs are not $500-600 I'll buy 10, they sell on avg $1500.00 & up. unless completely hammered.



and my idea was to find an existing lower but had to be sure between rpb, swd/cobray what the lower receiver differences where if any bc I found complete new OB upper parts kits less barrel & receiver. If I buy an existing lower it's not considered a new OB SA build. the lower I saw for sale was closed bolt, no sear carriage, so wouldn't have worked or been legal with that used lower.

My total cost would have been $700 instead of $1700 cost.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:



Quoted:


Quoted:


Quoted:

I found out today it's call a sear carriage the SA open bolts have welded into the frame. So this idea I had is going no where. Back to finding a decent open bolt SA for a realistic price.

Thanks guys.




Building a new OB Semi-auto is illegal and a good way to end up in prison.
Yeah I'll +1 that. Nothing wrong with learning but I got the impression it was a project idea. I've seen a couple for sale before locally for probably $500-$600  




OB macs are not $500-600 I'll buy 10, they sell on avg $1500.00 & up. unless completely hammered.



and my idea was to find an existing lower but had to be sure between rpb, swd/cobray what the lower receiver differences where if any bc I found complete new OB upper parts kits less barrel & receiver. If I buy an existing lower it's not considered a new OB SA build. the lower I saw for sale was closed bolt, no sear carriage, so wouldn't have worked or been legal with that used lower.

My total cost would have been $700 instead of $1700 cost.
I've seen 2 open bolts sell on our local gun trader and the guys were asking around 500-600 for them. And they had open bolt in all caps in the ad, they sold fast, but just saying you might keep your eye open

 
Link Posted: 10/5/2015 12:04:46 PM EDT
[#10]
I'm sure they did sell fast , well I check GB which is tough overpriced or bidding idiots drive price to high.(cause they gotta have it now), I check local traders but not much in them, even local pawn/gunshops only find newer mpa's. Nice guns, but not collectable OB SA.
Link Posted: 10/7/2015 9:52:53 PM EDT
[#11]
GOT ONE!!!!!!!!!!!!!!
I won  a bid on GB for $706.01 unreal, the seller had it listed as Cobray m11a1 and start price as what a cobray m12 would go for, But clearly in pics and on gun was RPB Industries sm 11a1.and it's OB in all pics, so I bid, another guy bid it to $701 I got it for $5.00 more, never thought that would happen, the cheapest on there is $1500.00 BIN price. I can't wait, I'm picking up a closed bolt like new tomorrow and probably this one next week, too bad they don't take the same mags.  Yeee Haaa!!!!!!!!!!!!!!!
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