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$235 bare upper m4 style

751 Views 5 Replies 3 Participants Last post by  4thIDvet, 
j427x
Custom 16" 1x9 5.56 Chrome Moly Carbine Upper NO Bolt/Carrier or Charging Handle

fairly inexpensive m4 upper. no bolt or charging handle.

not quite as mall ninja-ish as the DSA for $275 but should make a decent m4-forgerie for little $$

probably run like a clock with the LMT bolt carrier or other bcg and a cheap $15 charging handle.
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4thIDvet
O.K.. So not getting to technical for a new Mall Ninja. :)
How the hell do you head space these things?
Or do you just slam dance the bolt in and start busting caps. :)
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Lunyfringe
on the AR platform, headspace is determined by the barrel extension..
which is normally part of the barrel on an AR, it's unusual to get a barrel without one already headspaced- and this kit has a headspaced barrel

as long as the bolt is "in spec" then the headspacing will be correct... some barrel vendors include a bolt, to ensure the headspace is correct (or more to the point, accurate to match grade)

I personally don't like the common practice that many have of selling uppers without the bolt/BCG or charging handle.. the bolt should be matched to the barrel, but that's just my opinion, I don't have any evidence that it leads to problems..
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j427x
the barrel extension is head-space matched to the barrel to a standard sized bolt. if all parts are in tolerance and are running the same head-space they are in effect all the same.

the idea of including a bolt on a new ar barrel is to prevent some gommer from slapping a old bolt that is worn in there.

some barrel makers do sometimes head-space to a non-standard size. i think this is more to sell you THEIR bolt than anything else. you never see this of GI type barrels though.

a friend of mine has checked thousands of these GI barrels over the years. he claims to have never found a new one that was "out".


i have only done a few hundred on my go-no go nato set. i have never had one fail the test yet. if you buy a barrel set up and a quality bolt and it don't fit--you better go buy some lotto tickets!
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Lunyfringe
j427x said:
the idea of including a bolt on a new ar barrel is to prevent some gommer from slapping a old bolt that is worn in there.

some barrel makers do sometimes head-space to a non-standard size. i think this is more to sell you THEIR bolt than anything else. you never see this of GI type barrels though.
Click to expand...
anytime you're talking about barrels chambered in 5.56 (GI spec), then there's no issue... I hear about people using old bolts all the time.. I don't like the practice, but I don't hear of it causing an issue...

I usually see 2 reasons why a bolt is included with a barrel on the AR15 platform:
1) non-standard calibers requiring custom bolt: .50 Beowulf, 6.5 Grendel, etc...
2) tightest possible tolerances for match performance:

There are 5.56 GI level tolerances, .223 level tolerances (or wylde chamber), and then there are match grade... there is more to match grade than go/no-go.. they lap the bolt to the extension, to ensure even engagement of the lugs.. total overkill in all but competition matches- even then, they're trying to get the last fractions of MOA out of a rifle at that point.. and they custom load to match OAL so the bullet is just starting to engage the throat when chambered.

5.56 spec calls for 25 thousands longer freebore length (leade) than .223 to ensure reliability, but it means that the bullet is in a loose chamber- could be up to 25 thou before the bullet is engaged into rifling. Wylde chamber tightens this up, while still maintaining compatibility with 5.56

will it function safely with any in-spec bolt? yes..
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4thIDvet
Thank you guys.

Just caught this on the headspacing. Interesting Thank You.
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