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So what the hell was the Army Ordinance Board thinking when they

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So what the hell was the Army Ordinance Board thinking when they redesigned the A1? I cant think of a rational reason that the A2 profile is improved
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>>27554681
they found that soldiers were using their rifles to poke things and pry things (doors, windows, et c) that they were supposed to use entrenching tools for. this bent the light-weight barrel enough to notice at 300 meters.

the profile was thickened under and after the FSB to alleviate this.

because the area under the handguards needed to cool rapidly, the profile was retained at a small diameter. they did increase the length before the "bend" in the gas tube though, in order to ease manufacture. other changes include a new crush washer instead of a split ring, and an improved flash hider and standard twist rate.
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>>27554681
Retards where using the 3 prong and prying shit. That's why they went to the A1 birdcage (and to alleviate shit catching it).

People were retardedly bending the barrel and that solved this problem. Hence why it was thickened from the FSB to the barrel.

They didn't do the modern govt or whatever where it's thicker under the handguards, because the AR was still trying to be the wonderfully light weapon.

The A2 birdcage has the solid portion to reduce dust signitures and shit.
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>>27554723
>>27554681
there are other advantages as well:

the thicker profile at the front moves the point of balance forward, and with the change from rugged field sights to more occluded target sights, the "hang" of the rifle is balanced more evenly front/back.

the position of the gas port at the front meant that the barrel heated unevenly when fired automatically for long periods of time. a thicker portion of the barrel at the front would heat slower, allowing better "suppressing fire" temporarily from normal rifles until an actual automatic rifleman can be moved into position.

trust me, the government is loath to spend money on things like "safety" or "improvement" unless theres a serious need for it and even then, it has to be cheap enough.
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>>27554767
>They didn't do the modern govt or whatever where it's thicker under the handguards, because the AR was still trying to be the wonderfully light weapon.

>modern govt

the A2, A3, and A4 all have the same barrel profile. the "HBAR" was an outgrowth of Colt's attempts at making an M16 SAW variation that went no where.

the "medium contour", (not to be confused with medium length, barrel is a purely commercial invention.

the only "HBAR" barrel for the M16 family was the SOCOM barrel for the M4 for the 1990's was specifically for SF and SOF to be able to possibly sustain firefights without significant heat damage to the barrel.
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>>27554796
You're not wrong per say, because it *does* tend to make the weapon handier.

But, it's a mix between 'bending' the barrel when shooting long distances, and grunts being tards that can break a ball bearing.

>A rifle with more durable plastic parts and barrel which will take a beating during bayonet training and extended field exercises.

Is the main reason they went to the A2 profile up front. "Bending" from slinging in too heavy and bipod use, was what the marines were complaining and worried about.

Interestingly, the A1, during some independent testing, actually faired better then the A2. But, it might have to deal more with ammo choice.

>The M16A2 is less accurate out to ranges of 500 meters. Independent
testing conducted by the National Rifle Association, firing five groups of five rounds each at a range of 200 yards, resulted in the following average group sizes:
>Ml6A1/M193 - 3.82"
>M16A2/XM855 - 5.38"

Okayish source because I'm too lazy to dig up some great ones.


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>>27554812
Thanks fam, my knowledge of ar's ends at the weird prototype A2 that is actually a A1 gun with A2 furniture, and a burst setting.

I must have been thinking of the SOCOM contour.
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>>27554894
>>The M16A2 is less accurate out to ranges of 500 meters. Independent
>testing conducted by the National Rifle Association, firing five groups of five rounds each at a range of 200 yards, resulted in the following average group sizes:
>>Ml6A1/M193 - 3.82"
>>M16A2/XM855 - 5.38"

the A1 with a 1:12 twist and 55gr M193 ammunition were designed for each other. the A2 1:7 twist was a comprose for the M856 tracer which was much longer than the old M196 tracer. the ideal twist for the 62gr SS109 is either 1:8 or 1:8.5 depending on velocity. 1:9 is a common commercial twist because it works best with M855, and it's doubtful most civvies would shoot tracers. 1:10 is ideal for heavier 69gr match bullets (or if you're Swiss).
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>>27554940
>>27554894
basically the A2 is "less accurate", i.e. less consistent because of the compromise in twist rate, not because of the barrel profile.

you "a1 with a2" furniture is likely the XM16A1E1 or the Colt model 645 (bought by the USMC in the early 1980's). the M16A1 is the adopted name for the Colt model 701.
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>>27554894
>per say
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>>27554894
Forgot link.
>http://www.dtic.mil/dtic/tr/fulltext/u2/a168577.pdf

What's fascinating is 10% of xm16e1 barrels in 'Nam would require replacement every three months. KEK.

http://www.dtic.mil/dtic/tr/fulltext/u2/a953117.pdf

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>>27554940
>the A1 with a 1:12 twist and 55gr M193 ammunition were designed for each other. the A2 1:7 twist was a comprose for the M856 tracer which was much longer than the old M196 tracer. the ideal twist for the 62gr SS109 is either 1:8 or 1:8.5 depending on velocity. 1:9 is a common commercial twist because it works best with M855, and it's doubtful most civvies would shoot tracers. 1:10 is ideal for heavier 69gr match bullets (or if you're Swiss).

Very very aware of this, hence why I didn't mention anything about their 'reliability' testing. Just chuckling at some minor test done 60 years ago is all.

>>27554974
There were several varients of the xm16a1e1's floating around, ranging from a1 rear irons, and a squared front post, all the way to a2 uppers with an a1 pistol grip. Really depends.

But, I'm now reading about using a xm16a1 to shoot tent stakes into frozen ground.
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>>27554723
>>27554767
Fun fact about the whole 'prying shit with your barrels' thing: the barrels most likely weren't bent at all, it was just the gov't fucking up again.
everydaymarksman.wordpress.com/2015/04/23/origin-of-the-government-profile-barrel/
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>>27555044
>There were several varients of the xm16a1e1's floating around, ranging from a1 rear irons, and a squared front post, all the way to a2 uppers with an a1 pistol grip. Really depends.
and you know why? because the XM and E desginations were test adoptions. there were some 30 or 40 variations that were distinct colt models. use the colt model numbers if you want to see the complete change history rather than what the government adopted.

also the Army, Air Force, and USMC had different contracts for the same adoption name (XM16A1E1). So you could have 3 XM16A1E1, one each from each branch, and have them be completely different colt models. (model 645, 653, and 650)
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>>27555109
that's not a fuck up on the part of the government, that's someone not actually inspecting why the drop gauge failed and assumed a failure. still though, the weight at the front is still a marginal improvement by most accounts.
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>>27555137
They accepted a design based on a fuck up i.e. they did fuck up themselves.
I'm just throwing some light at the thing, no need to get all up in arms about semantics. Oh, and I'm certainly not delving into that silly argument whether it is slightly better or not.
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>>27555109
>The A2 barrel was created by mistake and has no real reason to exist.
Fucking knew it. None of the barrel bending/crowbar myths made sense to me. Always had a feeling true light barrel AR's felt better to me.
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>>27555137

no. stop saying this. unless you are an old fudd shooting from a benchrest at 500m, having the center of mass further forward is A BAD THING.
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>>27555222
I read this on arfcom awhile back
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>>27554940
Lightweight, flexible barrels were found to be more effectively accurate as they deal with harmonics better than stiffer, heavy-contoured barrels.
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