Flat top upper receiver question

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clovis

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Hi,
If I can figure out the problem I have with extraction(see my other tread) on this 16". I would like to get a flat upper receiver for it. I would keep the same barrel with the original front sight/gas block.

I would like to know if the flat upper are all the same regarding sight height. I mean if I buy an ARMS 40 it will be OK for any model flat top upper. I am thinking of ordering an Armalite from Wolverine.

To remove the barrel nut. I have 2 choice. Remove the front sight/gas tube all in once or just unpin the gas tube from the front sight. What is better???

Thanks,
Clovis
 
Really no reason to pull the front sight if you are not changing out the gas block. Just unpin the tube and remove it . Have you got the barrel nut wrench and receiver blocks?
 
You don't need to remove the barrel nut from the barrel to swap receiver.
Just un pin the gas tube. You only need to unscrew the barrel nut from the upper receiver/
 
In the semi-auto world, AR-15A3 and AR-15A4 are the same thing. In the U.S. military M16A3 and M16A4 are different, which has led to some confusion, but as far as you are concerned A3 and A4 are just two different names for a flattop upper.

When flattops were first developed, there was a problem with the initial design, and the rails had to be redesigned a little higher. Throughout the last several years, I have also seen a few instances where a batch of uppers would have trouble fitting standard accessories. RRA was famous for this happening when they were a new player in the market.

In general, I would say that any flattop upper made in the last 10 years by a respectable manufacturer SHOULD have a standard rail height, but there are no guarantees. If you get one that doesn't line up, you should be able to send it back under warrantee.
 
Will he have a problem if he keeps his original front sight? I was told there were different ones for fixed handles and flat-tops (something to do with an "F" marking in the casting?).
 
edon said:
Will he have a problem if he keeps his original front sight? I was told there were different ones for fixed handles and flat-tops (something to do with an "F" marking in the casting?).
Click to expand...

True and maybe, depends on the rear sight. It can be usually be resolved with a different front sight post, if it is a problem with a particular sight.

IIRC, Bushmaster advertises the .040 higher front sight post for this application.
 
This is a good point. I am looking to install an ARMS 40. I will get some of these higher front sight post also. Just in case.

Thanks,
Clovis
 
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