AR15.Com Archives
 Difference between a A3 and a M4 upper?
OhioAstromech  [Member]
1/8/2008 10:59:47 AM
Other than the feed ramp notches on the inside of an M4 Upper Receiver are there any real difference between a A3 and a M4 upper or are the dimensionally identical?

Can a Gunsmith turn an A3 into an M4?

Scot
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PropDoc  [Industry Partner]
1/8/2008 12:32:24 PM
Upper receiver only..............no (except aforemnetioned ramps)
OhioAstromech  [Member]
1/8/2008 1:05:48 PM
Can a Gusmith add those ramps to a A3 to make it a M4 upper?
I purchased the MEGA A3 upper from JC Weaponry at the same time as my lower receiver.
That was before I found out the M4 uppers had the ramps.
Does it matter if I use a A3 upper with a M4 barrel?

Scot
Alpha-Romeo3  [Team Member]
1/8/2008 1:22:39 PM

Originally Posted By OhioAstromech:

Does it matter if I use a A3 upper with a M4 barrel?

Scot


It's OK to use A3 uppers with M4 barrels but not M4 uppers with barrels without M4 feedramps.

See the pic of the A3 upper and M4 barrel combination at the bottom right of this thread.


AR Discussions FAQ & General Information Resource (Read First) tacked thread
Muskyjerk  [Team Member]
1/8/2008 1:24:43 PM
They can add the ramps but your barrel will also need the ramps as well.

look for the feed ramp thread on Thursday....


with regards to adding ramps...they would have to grind the anodized aluminum away. the anodizing give the aluminum a surface hardness similar to stainless steel. so adding the ramps will expose the raw aluminum and wear will increase. I would just trade the upper off.....
jhereg  [Team Member]
1/8/2008 1:28:38 PM

Originally Posted By Alpha-Romeo3:

Originally Posted By OhioAstromech:

Does it matter if I use a A3 upper with a M4 barrel?

Scot


It's OK to use A3 uppers with M4 barrels but not M4 uppers with barrels without M4 feedramps.

See the pic of the A3 upper and M4 barrel combination at the bottom right of this thread.


AR Discussions FAQ & General Information Resource (Read First) tacked thread


I've always heard just the opposite. I have heard you do *NOT* want to use an upper w/o M4 feed ramps w/ a barrel that has them. If you have the feed ramps on the barrel but not on the the upper then you have a lip on the upper for the bullet to catch on.
Alpha-Romeo3  [Team Member]
1/8/2008 1:42:56 PM

Pics of feedramps and uppers from my link



Originally Posted By jhereg:

Originally Posted By Alpha-Romeo3:

Originally Posted By OhioAstromech:

Does it matter if I use a A3 upper with a M4 barrel?

Scot


It's OK to use A3 uppers with M4 barrels but not M4 uppers with barrels without M4 feedramps.

See the pic of the A3 upper and M4 barrel combination at the bottom right of this thread.


AR Discussions FAQ & General Information Resource (Read First) tacked thread


I've always heard just the opposite. I have heard you do *NOT* want to use an upper w/o M4 feed ramps w/ a barrel that has them. If you have the feed ramps on the barrel but not on the the upper then you have a lip on the upper for the bullet to catch on.


If you have feedramp cuts on the upper (M4 upper) and no M4 feedramps on the barrel then you will have a lip on the upper for the bullet tip to catch on, see the pic above that says BAD.
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