The AR15

[paul73]

Probably another coyote gun. I haven't gotten into the mag dump type shooting. Although I can't see why I couldn't do that with this.

If I do it I would likely fit it with an 18 inch barrel. My current one is 20. Bipod up front and an arca rail close to the balance point for a tripod. Decent scope with exposed turret for elevation. I'm still going back and forth regarding a suppressor. Likely a dedicated 223 can.

18 is kinda a waste. a heavy contour 20" is good for precision, but for something to handle and agile you want either 16 or 14.5" with a pinned can adapter to make it into full 16" per regulations.

or go one level deeper into the rabbit hole and get this one in 10.7" .223, as it is quite amazing, and use it with a 'brace'.

View: https://www.youtube.com/watch?v=5vAZ1PNuaWs

 

[paul73]

I don't believe any of my builds have been headspaced. Is it that critical?

depends upon how aggressively you match and mix brands. aero on aero or aero on BA does not need much checks at all.

 

[PappyM3]

depends upon how aggressively you match and mix brands. aero on aero or aero on BA does not need much checks at all.

A need to headspace doesn’t have anything to do with whether your barrel, receiver, and bolt are all the same manufacturer or not. They are all building to the TDP, and I can also guarantee the vast majority aren’t using their own barrel extensions anyway.

I don't believe any of my builds have been headspaced. Is it that critical?

You should. A bolt/barrel extension could easily be out of spec and missed by QC (or if there is no QC like PSA).

If you want to replace a barrel, bolt, or build an upper, you should own headspace gauges in the caliber you’re building. The biggest annoyance is removing the ejector to do the check. One of these days I will have my gauges milled to allow the ejector to remain in place.

That said, very few people actually check headspace on AR builds. The risks are pretty low, even with an out of spec headspace. You may not be able to chamber ammo, or you could have increased parts wear, or start popping primers, hard to extract brass or rip rims off brass. Very low risk of catastrophic failure destroying the gun or injuring you. It’s not an M2 .50 cal.

I bet a lot of cheaper gun manufacturers, like PSA, don’t check headspace either.

I have zero concern with throwing in spare bolts into my guns are the range without checking headspace. But when building at home, yes I check because it is just one step in the correct process to ensure a good build.

 

[G4Y4HK]

A need to headspace doesn’t have anything to do with whether your barrel, receiver, and bolt are all the same manufacturer or not.



You should. A bolt/barrel extension could easily be out of spec and missed by QC (or if there is no QC like PSA).

If you want to replace a barrel, bolt, or build an upper, you should own headspace gauges in the caliber you’re building. The biggest annoyance is removing the ejector to do the check. One of these days I will have my gauges milled to allow the ejector to remain in place.

That said, very few people actually check headspace on AR builds. The risks are pretty low, even with an out of spec headspace. You may not be able to chamber ammo, or you could have increased parts wear, or start popping primers, hard to extract brass or rip rims off brass. Very low risk of catastrophic failure destroying the gun or injuring you. It’s not an M2 .50 cal.

I have zero concern with throwing in spare bolts into my guns are the range without checking headspace. But when building at home, yes I check because it is just one step in the correct process to ensure a good build.

What's the rule of thumb?

new upper, new bolt = rifle is fine
new upper, used bolt = rifle is fine
used upper, new bolt = rifle is fine
used upper, used bolt [from another rifle] = check yo head

 

[PappyM3]

What's the rule of thumb?

new upper, new bolt = rifle is fine
new upper, used bolt = rifle is fine
used upper, new bolt = rifle is fine
used upper, used bolt [from another rifle] = check yo head

Any well used bolt should be checked. Whether it’s a new upper or not. The bolt face can wear with increased setback over time due to the pressures.

Edit: if it’s a few hundred rounds used, I wouldn’t worry. If it’s a few thousand, hell yeah double check.

 

[Soundwave]

The only 5.56 rifle upper I completely put together myself was headspaced by the shop that did the P&W actually. But when I had them do my .308 they didn't have the gauge...

 

[LakeTrout]

18 is kinda a waste.

how is 18 a waste? Some 18s get just about the same velocity as 20” barrels, while saving 2” of length, and some weight. And they’re a significant improvement in velocity over 16s. And you can reliably use a rifle length gas system in the 18s. If anything, they’re less wasteful than 20s for about the same performance.

 

[PappyM3]

how is 18 a waste? Some 18s get just about the same velocity as 20” barrels, while saving 2” of length, and some weight. And they’re a significant improvement in velocity over 16s.

There is some overlap of velocities, because every barrel is different. But a fast 20” will be faster than a fast 18”. We could also say an 18” is a waste because some 16” are just as fast as some 18”. The reality is there will always be a right-shifted bell curve of velocities per barrel length as the lengths get longer. One just needs to know what minimum average velocity they’re looking for.

Lots of people like 18” because of the Mk12. But the Mk12 was only 18” because of procurement rules BS. They wanted 20”.

All that said, for some, the balance of velocity to length in an 18” fits their needs/wants trade space.

I’m just saying that “some 18”s are as fast as some 20”s is kind of a bunk argument. It’s pretty impossible to know if you’re getting a fast-for-length barrel when you buy it.

I do think 18” is great for being the shortest barrel length for reliable use of a smooth rifle length gas system.

 

[45BPCR]

AR's are fun guns.
Kinda like Barbie dolls for men.

I have 4.

An old A2 Bushmaster DCM lead filled one made in Windham
A DPMS LR308T I bought during the height of the Obama gun ban hysteria for short money.
A PSA I built on one of their MAGA lowers. I use laser engraved 30 rnd MAGAzines with that one.
And a suppressed 300BLK built on an Anderson lower labeled "Ghost Gun", it wears a High Standard 16" upper.
I've knocked over 50lb. rams at 500 meters easily with all of them including the 300BLK with subs.

Their not usually my first choice when opening the gun safes.
And I smile at my Mini14 nestled in among them, as it runs on anything.

 

[FC Magic]

I have a Gucci rifle I picked up here (thank you, Igor!) for a great price. When I asked about it, the guy I bought it from said it shoots just like other ARs but it weighs about half as much. Like all things where weight and composition of materials are a consideration, a difference in ounces is represented by a difference of $100's if not $1000s.

 

[paul73]

how is 18 a waste? Some 18s get just about the same velocity as 20” barrels, while saving 2” of length, and some weight. And they’re a significant improvement in velocity over 16s. And you can reliably use a rifle length gas system in the 18s. If anything, they’re less wasteful than 20s for about the same performance.

If you can handle 18, then you can handle 20.
Where 20 is too much, 16 works. And 14.5 works as well as 16 does in most cases.
18 is still neither here nor there.

18 works well for .308 where shorter barrels become more of an issue.

In majority of cases it is still just a 15min swap task to replace a barrel. Not much stuff to fight about.

 

[LakeTrout]

There is some overlap of velocities, because every barrel is different. But a fast 20” will be faster than a fast 18”. We could also say an 18” is a waste because some 16” are just as fast as some 18”. The reality is there will always be a right-shifted bell curve of velocities per barrel length as the lengths get longer. One just needs to know what minimum average velocity they’re looking for.

Lots of people like 18” because of the Mk12. But the Mk12 was only 18” because of procurement rules BS. They wanted 20”.

All that said, for some, the balance of velocity to length in an 18” fits their needs/wants trade space.

I’m just saying that “some 18”s are as fast as some 20”s is kind of a bunk argument. It’s pretty impossible to know if you’re getting a fast-for-length barrel when you buy it.

I do think 18” is great for being the shortest barrel length for reliable use of a smooth rifle length gas system.

I can only speak for maybe 10 or so 16” ARs a couple 18s and a couple 20s that I’ve seen first hand through a chrono. So, that’s not a big sample size compared to some others. But what I’ve seen is a couple hundred or so fps difference between the 16 and 18s and twenty to sixty-ish between the 18s and 20s.

So to me, the 18s are a big enough improvement over the 16s to jump to, depending on the purpose of the rifle. And they’re also close enough to the 20s where the length and weight savings of the 18s are attractive for a lot of those purposes. Bench shooting, then there’s no reason to go to the 18s. But I think the 18s are attractive for many practical purposes and also the rifle length system is nice too. I certainly wouldn’t call an 18 wasteful. For the minimal gain in FPS of a 20 and the same length gas system, I think calling the 20 “wasteful” may make more sense but only for certain purposes for these rifles. I wouldn’t call a 20-60 fps gain at the cost of 2” and a little bit of weight wasteful for many applications. Just depends on what the purpose of the rifle is.

 

[LakeTrout]

If you can handle 18, then you can handle 20.
Where 20 is too much, 16 works. And 14.5 works as well as 16 does in most cases.
18 is still neither here nor there.

18 works well for .308 where shorter barrels become more of an issue.

In majority of cases it is still just a 15min swap task to replace a barrel. Not much stuff to fight about.

I respect your opinion on this and see your point but there is, what I would consider, a significant improvement in velocity of an 18 vs. a 16, and not a significant improvement between an 18 and a 20, for what I think the majority of people own AR15s for. For certain competitions, some types of hunting, DMR setups, etc. I would agree with you that you might as well do 20. But for an all around rifle, I think that extra 2” is a waste and probably not adding much to the effectiveness of the cartridge. Just my opinion.

 

[Bodhisattva]

The velocity difference between an 18 and a 20 is going to be negligible. Where the advantage of a 20 over an 18 will be with bullet weight. With a 20 you can get the lighter bullets up to higher velocity to maintain lethality. If you go with an 18 you’re going to want to use heavier bullets to maintain lethality at distance. But with an 18, it’s not as critical as it would be with a say a 14.5 and under.

Identifying your intended engagement distances will be the first thing you want to figure out. Then you can start to figure out what barrel length, bullet weight, etc etc.

The beauty of the platform is you don’t even have to get wild with the barrel to get great accuracy with higher quality ammo. Yeah, you’re going to want something better than a PSA/BCA barrel. But you can get great results out of a Rosco or Ballistic Advantage barrel. Just keep in mind BA barrels tend to be a little over gassed.

 

[LakeTrout]

Where the advantage of a 20 over an 18 will be with bullet weight. With a 20 you can get the lighter bullets up to higher velocity to maintain lethality. If you go with an 18 you’re going to want to use heavier bullets to maintain lethality at distance

Its literally 40-50 fps average difference with lighter bullets, in my experience, between 18 and 20”.

Not trying to be snarky, but do you have real world experience with lighter bullets in both through a chrono? Or did you read something on the Internet? The difference of 50 FPS is not something that would qualify as needing a heavier bullet to maintain the same performance at greater distance, practically speaking. In my opinion at least.

 

[Bodhisattva]

I realize there is only a negligible difference between to the two. Hence why I stated it. The difference I’m talking about is in regards to 55gr bullets specifically. Probably should have made that more clear.

I’m at work and trying to convey what I’m saying in the shortest span possible and in between calls.

 

[peterk123]

Has anybody used bullet weights of 50 grains or less in a 223? What barrel twist would be required?

 

[PappyM3]

The velocity difference between an 18 and a 20 is going to be negligible. Where the advantage of a 20 over an 18 will be with bullet weight. With a 20 you can get the lighter bullets up to higher velocity to maintain lethality. If you go with an 18 you’re going to want to use heavier bullets to maintain lethality at distance. But with an 18, it’s not as critical as it would be with a say a 14.5 and under.
…

~50-100 fps depending on bullet weight and powder. Same difference as between 16” and 18”. Below 16” there tends to be a sharper curve for 5.56.

A 20” vs an 18” will get you ~25-50 yards further fragmentation range for any given bullet. Same as 18” vs 16”.

It’s all a trade space on external and terminal ballistics for a desired bullet vs barrel length and maneuverability.

Data using various velocity reports from around the internet along with my own, averaged out.

 

[PappyM3]

It’s literally 40-50 fps average difference with lighter bullets, in my experience, between 18 and 20”.

Crowdsourced chrono data indicates that is on the low end of a difference. For .223, yeah 50fps is pretty common for 55gr between 18/20”. But for 5.56, the spread can get up to 100fps between the two lengths for 55gr.

Edit: to be more accurate about looking at the same spot in the bell curves, 20” seems to be about 3,300 on the high end and 18” about 3,220. So, 80fps difference when accounting for equally fast barrels.

Has anybody used bullet weights of 50 grains or less in a 223? What barrel twist would be required?

If it’s a quality bullet, 1:7 will work fine. If it’s a cheap bullet, 1:9 would be better for more precision.

But you could go as slow as a 1:12 twist for those light bullets.