Help is need with an Upgrade Project to convert a A2 CAR to a Flatop

af22raptor · #1 01-09-12, 01:19

I have a Bushmaster 11.5 inch Heavy Barrel with a 5.5 CAR Flash Hider that has been worked over and its very accurate and reliable after several growing pains. I purchased the carbine back in 1999 and the upper receiver is a A2 without m4 feed ramps. Now here is my issue I would like to swap out the A2 upper to a Flat top but since the barrel does not have the M4 feed ramp on the barrel extension I either have to get a new barrel extension plus the tool to do so plus the receiver. I would like to just do a upper receiver swap and keep the cost to a minimum since I am also working on a 18 inch SPR clone with all the bells and whistles. Any one know of someone selling a solid A3 upper without the M4 feed ramps?

thanks.

Iraqgunz · #2 01-09-12, 01:55

Since you are bound and determined to keep the BM barrel.

http://www.tacticalinc.com/flat-uppe...le-p-1133.html

Quote:

Originally Posted by af22raptor

I have a Bushmaster 11.5 inch Heavy Barrel with a 5.5 CAR Flash Hider that has been worked over and its very accurate and reliable after several growing pains. I purchased the carbine back in 1999 and the upper receiver is a A2 without m4 feed ramps. Now here is my issue I would like to swap out the A2 upper to a Flat top but since the barrel does not have the M4 feed ramp on the barrel extension I either have to get a new barrel extension plus the tool to do so plus the receiver. I would like to just do a upper receiver swap and keep the cost to a minimum since I am also working on a 18 inch SPR clone with all the bells and whistles. Any one know of someone selling a solid A3 upper without the M4 feed ramps?

thanks.

karlb · #3 01-10-12, 12:41

I've used this $89 RRA reciever recently to do much the same thing.
http://www.pkfirearms.com/Upper_Receivers/25/c

m16 · #4 01-10-12, 13:53

Do you have a sight base pinned to that barrel?

Cause it's probably not F-marked, you might need a taller front sight post.

af22raptor · #5 01-10-12, 14:16

I want to thank Iraqgunz and karlb for the links. M16 the front base is not a F and I know that it would be an issue to use the iron sight but I have an extra Samson rifle length rail handguard and I was thinking that it might be cool to have the rail over the 16 inch barrel with Magpul Mbus front and rear sight. I was also considering getting one of the flip front base from YHM that are bolted on because this upper would be setup mainly for Home Defense, Range, and backup for 3g.

When I first got the carbine it was a mess it could not fire more than 3 rds before it stopped but after 3 trips back to BM and letting a Salty Gunny Armorer take a look at it the carbine works like a Swiss timepiece now. The main issue was a undersized gas hole in the barrel.

GI_Jared · #6 01-11-12, 13:35

Range Tool as A3 stripped uppers without M4 feedramps for $57. I recently purchased the M4 feedramp version from them and the quality looks the same as any other Mil-Spec reciever.
http://www.rangetool.com/index.php?p...mart&Itemid=20

elephantrider · #7 01-11-12, 22:16

Would it not be possible to swap to to an M4 flatop upper with feedramps and simply grind some feedramps into the existing barrel extension? Then you would have the flatop with the M4 feedramps.

af22raptor · #8 01-11-12, 22:56

Quote:

Originally Posted by elephantrider

Would it not be possible to swap to to an M4 flatop upper with feedramps and simply grind some feedramps into the existing barrel extension? Then you would have the flatop with the M4 feedramps.

I considered upgrading the barrel extension so that I could use a M4 feed ramp upper but but the extra cost of the extension and wrench was going to be more than what I wanted to spend on this upper since the upper was tuned by a Gunny buddy and works flawlessly. I keep going back and forth on changing the gas port to a low profile so that I can use a set of Magpul MBUS that I have but I think that I will keep it with the A2 front sight base and maybe change it out to a flip later.

Skintop911 · #9 01-11-12, 22:56

Quote:

Originally Posted by elephantrider

Would it not be possible to swap to to an M4 flatop upper with feedramps and simply grind some feedramps into the existing barrel extension? Then you would have the flatop with the M4 feedramps.

Don't do that. WECSOG never makes things better.

I've done a number of these conversions. Get an upper that matches your barrel extension. You will probably need a taller FSP. Test fire the gun. Follow the normal PM and assembly precautions discussed elsewhere here at M4C.

markm · #10 01-12-12, 11:34

Quote:

Originally Posted by af22raptor

I considered upgrading the barrel extension so that I could use a M4 feed ramp upper but but the extra cost of the extension and wrench was going to be more than what I wanted to spend on this upper

You can't do that anyway... The gas port is drilled after TDC is determined by the final position of the Barrel Extension. Changing extensions would put the gas port somewhere else.

To make this work you'd spend more than the cost of a good upper half... BCM, DD, etc.

elephantrider · #11 01-12-12, 21:01

Quote:

Originally Posted by markm

You can't do that anyway... The gas port is drilled after TDC is determined by the final position of the Barrel Extension. Changing extensions would put the gas port somewhere else.

To make this work you'd spend more than the cost of a good upper half... BCM, DD, etc.

Right. But would it be possible to just grind some feedramps into the existing barrel extension with some careful dremel work?

Col_Crocs · #12 01-13-12, 00:49

Have you considered just selling that upper and getting a 16" upper in the config you want?

af22raptor · #13 01-13-12, 01:09

Quote:

Originally Posted by Col_Crocs

Have you considered just selling that upper and getting a 16" upper in the config you want?

I have but this was the original upper for this carbine and holds lots of good memories of a buddy that is no longer here. I currently have 2 lowers but 4 uppers and I am working on a special project a SPR MK12 style rifle that I can use for 3 gun matches. I like to DIY so I try to get as much knowledge from people that know the subject that I bounce ideas and with their help I choose the parts run them by a couple of buddies then if I have not made any mistakes order the parts and have an assembling party.

Tweak · #14 01-13-12, 02:09

just buy a flattop without the ramps.

rob_s · #15 01-13-12, 06:18

Quote:

Originally Posted by elephantrider

Right. But would it be possible to just grind some feedramps into the existing barrel extension with some careful dremel work?

Lot's of things are possible. Far less are advisable.

wetidlerjr · #16 01-13-12, 11:09

Quote:

Originally Posted by elephantrider

Right. But would it be possible to just grind some feedramps into the existing barrel extension with some careful dremel work?

Back away from the Dremel!