General Purpose Rifle - Barrel Contour (Standard vs Lightweight)

[rlsmith1]

After looking around, I haven't seen any real accuracy tests that consist of a 10 round group, 60-90 rounds shot quickly, followed by another 10 round group. Would be worth it if someone could do this and track accuracy every 100 rounds up to 500 rounds for a couple different barrel profiles from the same manufacturer. I'm still dialing in my gas gun fundamentals so I wouldn't be a good candidate for that. Oh and I don't have anything select fire

I'd love to hear any commentary on standard vs lightweight barrels' accuracy (1) after a string of fire (say 60-90 rounds to heat things up) and (2) how sensitive they are to attaching a suppressor (the one on this gun will be ~14 oz with the muzzle device). I think it is pretty much agreed that lightweight barrels are generally in the same realm of accuracy as their standard weight counterparts for the first few rounds. I'm just wanting to understand at what point does a heavier profile or carbon barrel make sense.

I ask because I am putting together a general purpose 14.5" and I want to keep things as light as possible since I will be running a suppressor, LPVO, light, and laser. For now, I have picked up a cheap (used) standard weight barrel that is in the 31 oz range and it is very useable, but taking half a pound off would be nice. I have also considered a Proof barrel in a standard contour but want to make sure they are durable (most of the barrel will be tucked under a MK8 handguard).

My use case would be everything from defense to coyotes and general training during the day and night. I'm pretty agnostic to stainless vs CM but if I go CM it will be a Criterion Core or Hybrid. I have not owned a lightweight AR barrel before mainly because of sustained accuracy concerns but I don't want to box myself in either.


ETA: I have decided that for my purposes, a ~30oz 14.5" barrel is what I am after

 

[Pappasniper]

If you want to run your gun very hard, 60-90 rounds and want accuracy too, you need a beefy barrel to handle that heat. No question about it, but you might find barrels that can survive it, but not with great accuracy to follow. Beef , its what's for dinner!

PB

 

[Molon]

I think it is pretty much agreed that lightweight barrels are generally in the same realm of accuracy as their standard weight counterparts for the first few rounds.

Where did you get that factoid from?

...

 

[rlsmith1]

If you want to run your gun very hard, 60-90 rounds and want accuracy too, you need a beefy barrel to handle that heat. No question about it, but you might find barrels that can survive it, but not with great accuracy to follow. Beef , its what's for dinner!

PB

Sounds good. Part of what has me thinking of this is when I did the math on what a KAC Mod 2 barrel should weigh, it came out to 25-27 oz on a 14.5" barrel which is more on the lightweight side of things...

Where did you get that factoid from?

...

Interestingly, by reading a few of your posts (which are very informative and I appreciate). It seems that the Core barrel you reviewed was 1 MOA to 1.3 MOA with match ammo and a standard barrel of similar quality is 0.8 MOA to 1.2 MOA. To me, that is "in the realm" of accuracy. Do you have a compiled list of barrels (to include length, weight, mfg, material, and accuracy) that you have tested that you could share?

I'm not claiming to know it all or that "the science is settled" haha

 

[TonyTheTiger]

I vote lightweight. Mostly because I've seen a lot of people wanting accuracy after a 90 round burn down, but I've never seen anyone actually doing that.

 

[rlsmith1]

I vote lightweight. Mostly because I've seen a lot of people wanting accuracy after a 90 round burn down, but I've never seen anyone actually doing that.

I agree, I'm just wondering what the accuracy loss typically is after 90 rounds. Does it open up to 1.5x of where it was? That's a different story than if it goes to 2x or 3x...

 

[Jsp556]

Profile>weight… I’d rather have a heavier barrel with a good profile than a lighter weight option in a government profile.

 

[RUTGERS95]

standard, weight differential is negligent imho

 

[Eli17L]

Didn't the WWSD project come up with a lightweight barrel that retained accuracy after heating up?
Its been to long since I watched it and can't remember the details.

 

[Molon]

Interestingly, by reading a few of your posts

If you want to make statements about what “is pretty much agreed” upon pertaining to the precision of light-weight AR-15 barrels versus standard weight AR-15 barrels you have to do some apples to apples comparisons using significant shot sample sizes. At a minimum, that means the same barrel length, the same steel, the same type of rifling, the same chamber/bore treatment and particularly the same chamber.

For the last thirty years the de facto standard for what constitutes a 16” light-weight AR-15 barrel contour has been the Colt barrel found on the Colt 6520 and 6720. The ubiquitous government profile is what is found on the overwhelming majority of standard weight 16” barrels. Anything outside of those profiles within the same weight category makes the profile itself an uncontrolled variable.


Colt light-weight 6520/6720

Colt government profile 6920

The graphic below shows the results of an accuracy/precision comparison of a Colt 16” HBAR (6721), a Colt 16” government profile barrel (6920) and a Colt 16” light-weight barrel (6520/6720). The graphic shows the results of three 10-shot groups fired in a row at a slow cadence and over-layed on each other to form 30-shot composite groups. The mean-radius metric is used to compare the precision of those different barrel weights so that all 30 shots from each barrel are evaluated in the metric.

The Colt HBAR was the most accurate/precise barrel with a mean radius of 0.32”. The Colt light-weight barrel was the least accurate with a mean radius of 0.58” and the accuracy of the Colt standard weight barrel was in-between those two barrels.

.....





…..

 

[rlsmith1]

If you want to make statements about what “is pretty much agreed” upon pertaining to the precision of light-weight AR-15 barrels versus standard weight AR-15 barrels you have to do some apples to apples comparisons using significant shot sample sizes. At a minimum, that means the same barrel length, the same steel, the same type of rifling, the same chamber/bore treatment and particularly the same chamber.

For the last thirty years the de facto standard for what constitutes a 16” light-weight AR-15 barrel contour has been the Colt barrel found on the Colt 6520 and 6720. The ubiquitous government profile is what is found on the overwhelming majority of standard weight 16” barrels. Anything outside of those profiles within the same weight category makes the profile itself an uncontrolled variable.


Colt light-weight 6520/6720

Colt government profile 6920

The graphic below shows the results of an accuracy/precision comparison of a Colt 16” HBAR (6721), a Colt 16” government profile barrel (6920) and a Colt 16” light-weight barrel (6520/6720). The graphic shows the results of three 10-shot groups fired in a row at a slow cadence and over-layed on each other to form 30-shot composite groups. The mean-radius metric is used to compare the precision of those different barrel weights so that all 30 shots from each barrel are evaluated in the metric.

The Colt HBAR was the most accurate/precise barrel with a mean radius of 0.32”. The Colt light-weight barrel was the least accurate with a mean radius of 0.58” and the accuracy of the Colt standard weight barrel was in-between those two barrels.

.....





…..

Now we are getting somewhere! Love this data, thanks for sharing and compiling.

I don’t know if this is an appropriate conclusion to draw, but it looks like most of the shots that opened up the lightweight composite group were in the 3rd string of fire. The other profiles seems to be more evenly dispersed.

Was each barrel allowed to cool to ambient temp between groups?

I would be extremely interested to see these same results if you ever have the chance to shoot Criterion Core, Hybrid and HBAR barrels. I would be curious to see if their claims of intelligent weight distribution on the Core result in better performance.

Based on the data above, standard profile is likely what I’m looking for

 

[Vynz]

My take away from Molon’s post is probably incorrect but 30 rounds in 0.58” from an AR-15 at 100yards from a lightweight barrel is outstanding. I don’t compete so I can’t speak from that context but there is no hunting context I’ve experienced where 3 strings of 10 shots around 0.5” at 100yards is even close to a performance requirement. When shooting an living things, they all tend to run around after the first shot.

 

[RUTGERS95]

My take away from Molon’s post is probably incorrect but 30 rounds in 0.58” from an AR-15 at 100yards from a lightweight barrel is outstanding. I don’t compete so I can’t speak from that context but there is no hunting context I’ve experienced where 3 strings of 10 shots around 0.5” at 100yards is even close to a performance requirement. When shooting an living things, they all tend to run around after the first shot.

Modern ARs are light years ahead of 20-30yrs ago for reliability and accuracy. I've yet to find one that would not serve 99% of purpose if needed. People looking for perfection are always dissappointed

 

[Vynz]

Modern ARs are light years ahead of 20-30yrs ago for reliability and accuracy. I've yet to find one that would not serve 99% of purpose if needed. People looking for perfection are always dissappointed

I agree. I’d go so far as to say most people are blind to real world perfection because they are chasing a fantasy. It’s similar to what I hear sword people say - I want a Katana strong enough to cut a car in half, sharp enough to cut a silk scarf falling onto it, durable enough to never loose its edge and weight 0.5lbs so I never have to do arm day.

 

[mheimer_45]

What are your accuracy expectations. 60-90 rounds isn’t coyote hunting or prairie dog hunting (Atleast not where I live). If your looking at man sized targets about anything will do.

 

[rlsmith1]

My take away from Molon’s post is probably incorrect but 30 rounds in 0.58” from an AR-15 at 100yards from a lightweight barrel is outstanding. I don’t compete so I can’t speak from that context but there is no hunting context I’ve experienced where 3 strings of 10 shots around 0.5” at 100yards is even close to a performance requirement. When shooting an living things, they all tend to run around after the first shot.

I agree with the above, but what he’s showing is mean radius. Double that for how groups are usually measured (about 1.2” in this case). Still not bad though

 

[r.tenorio671]

....2 to 3 30rd mags in a short period of time..... I'd go beefier barrel. I'd look at shaving weight in the selection of LVPO, light, suppressor, handguard, etc.

 

[Frank Green]

If you want to run your gun very hard, 60-90 rounds and want accuracy too, you need a beefy barrel to handle that heat. No question about it, but you might find barrels that can survive it, but not with great accuracy to follow. Beef , its what's for dinner!

PB

It's not just the contour/heavier weight that will help you. It goes back to the quality of the barrel and the way it's been manufactured.

Button and hammer forged barrels work against you and it gets worse with a lighter weight contour and or if you do fluting and muzzle threading. Because of the way these barrels are made....as you turn it smaller/lighter and or flute it etc...the bore ends up opening up on you. Changing in size.

Cut rifled barrels don't have that problem as we don't work harden the bore and or induce stress into the blank.

Four things make a good barrel. Bore and groove uniformity over the entire length of the barrel, twist uniformity and the straighter the barrel and more stress free it is the more forgiving it is going to be when it comes to accuracy and consistency. This applies to bolt guns and gas guns as well.

The attached sketch was an inspection we did on a button rifled 308w AR10 barrel. The barrel was fluted. The barrel after all the finished work got done to it then got melonite treated. Several barrels got overnighted to me. I had to do a quick gage of the bore and overnight the barrel back to the shop doing the melonite treatment. Then they got overnighted back to me for the follow up measurements and I had to overnight the barrels back to them again. So sorry for the chicken scratch writing/drawing. This will give you an idea of before and after on a AR platform and a button rifled barrel blank.

Later, Frank
Bartlein Barrels

 

[Frank Green]

 

[Frank Green]

I was able to post it as a pic by itself instead of an attachment.

I'm not hacking on the melonite treatment process. This all has to do with the quality of the material and how the barrel is made. Those dimensions shouldn't be changing like that.

The closer the machine work gets to the center of the bore/wall thickness....as button rifling doesn't remove the material it displaces the material. All of that stress has to go some where. When you do the finish machine work like fluting, contouring, threading the muzzle etc.. the closer you get as you cut into the wall thickness of the barrel....it will have an effect on the bore changing more often then most people think.

So you have to ask yourself some questions. What is your accuracy requirement? How hot you going to get the barrel etc....

I love this picture as it shows how the steel gets pushed/moved around when the button goes into the blank.

Later, Frank

 

[rlsmith1]

@Frank Green this is great perspective and those measurements are awesome to see. Crazy pic as well... Really appreciate the input, will chew on this for sure. Thanks!

 

[Molon]

I don’t know if this is an appropriate conclusion to draw, but it looks like most of the shots that opened up the lightweight composite group were in the 3rd string of fire. The other profiles seems to be more evenly dispersed.

Was each barrel allowed to cool to ambient temp between groups?

I would be extremely interested to see these same results if you ever have the chance to shoot Criterion Core, Hybrid and HBAR barrels. I would be curious to see if their claims of intelligent weight distribution on the Core result in better performance.

Incorrect. While the outlying shot in the left upper quadrant is from group number three, the outlier in the right lower quadrant is from group number one.

There is no need to "allow each barrel to cool to ambient temp between groups" because all the shoots were fired in a slow cadence, so heat build-up was not a factor.



Results from my 16" Criterion CORE barrel . . .

Criterion 16” CORE Barrel Accuracy Evaluation

Well over a decade ago, the late John Noveske was the impetus for bringing modern AR-15 barrel profiles to the civilian market. His 16" CHF N4 barrel profile has the same weight as a government profile barrel of the same length, but it has a more intelligently designed contour that places more of the weight of the barrel from the chamber to the gas block journal and does away with the M203 cut-outs.

Over the last several years we’ve seen the emergence of barrels produced by multiple manufacturers with the specific objectives of balancing weight distribution, heat absorption and handling characteristics while at the same time endeavoring to improve upon the accuracy/precision of old school barrel profiles of similar weight. Criterion Barrels CORE series of barrels is a prime example of this modern approach to profiles for AR-15 barrels.


The Criterion 16” CORE barrel reviewed for this article has a stripped weight of exactly 1 pound, 12.0 ounces. This is the same weight as a Colt 16” government profile barrel. As with the Noveske CHF N4 barrel, the CORE barrel profile has done away with the useless M203 cutouts. More of the barrel material has been shifted to the aft of the barrel for a “continuous taper” profile. The gas block journal for the CORE barrel is 0.625”.


The 16” CORE barrel . . .

The barrel stamp reads: CRITERION 223 WYLDE 1-8

The date code on this barrel reads: 08/21.

The CORE barrel is button-rifled and the bore is hand-lapped. The bore and chamber are chrome-lined. As pictured above, the barrel has a 223 Wylde chamber, a 1:8” twist and utilizes a mid-length gas system. The gas port diameter gauged at 0.078”.

The gas block journal has a single dimple contralateral to the gas port.

The barrel extension has M4 feed-ramps, although it is not marked as such like a Colt barrel extension.

The crown . . .

I installed the Criterion 16” CORE barrel in a new Colt cage-code M4 upper receiver and free-floated the barrel with a Geissele MK16 rail. A new JP Enterprises EnhancedBolt closed on a 1.4646” headspace gauge and did not close on a 1.4666” headspace gauge.

I conducted an accuracy (technically, precision) evaluation of the Criterion 16” CORE barrel from my bench-rest set-up following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any group reduction techniques (e.g. fliers, target movement, Butterfly Shots).

The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Pictures of shot-groups are posted for documentation.

All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The free-float hand-guard of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was used. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.

The Wind Probe . . .

The accuracy evaluation of this barrel began with factory loaded Federal 77 grain Gold Medal Match ammunition. One of the first groups fired from this barrel had an extreme spread of 0.18”. That group is pictured below.

The very next group fired from this barrel had an extreme spread of 1.5”. That 10-shot group is pictured below.

A 10-shot group with an extreme spread of 1.5” is perfectly acceptable for a 16” chrome-lined AR-15 barrel with a weight of 1 pound, 12 ounces. However, this barrel isn’t broken-in yet. The bore-scope image shown below was taken prior to any shots being fired. It shows the tooling marks on the lands in the leade, which run perpendicular to the direction of bullet travel.

For the barrel to shoot to it’s potential, the sharp edges of these tool marks need to be “burnished” out. So, I continued shooting 10-shot groups using a variety of factory loads and hand-loads.

For comparison, the bore scope view shown below is from the leade of a Colt M4A1 SOCOM barrel that's been fully broken-in.

As the fired round-count for the CORE barrel approached 150, the size of the groups shrank and became more consistent. At this point, I fired the three 10-shot groups “of record” using one of my standard match-grade hand-loads topped with Sierra 55 grain BlitzKings. When fired from my Krieger barreled AR-15s, this load has produced ½ MOA 10-shot groups at 100 yards.

The three, 10-shot groups fired in a row from the Criterion 16” CORE barrel from a distance of 100 yards had the following extreme spreads:

1.15”

1.09”

1.13”

for an average 10-shot group extreme spread of 1.12”. The three, 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius of the 30-shot composite group was 0.39”.



The smallest 10-shot group . . .

The 30-shot composite group . . .

…

 

[Molon]

My take away from Molon’s post is probably incorrect but 30 rounds in 0.58” from an AR-15 at 100yards from a lightweight barrel is outstanding.

That is incorrect. The results I posted above were for the mean radius, not the extreme spread. The "rule of thumb" for comparing the mean radius to the extreme spread is to multiple the mean radius times three to obtain a high probability of the extreme spread for averages of 10-shot groups. (There's more to it than that, but the rule of thumb works well enough for this discussion.)

The results listed below are from another 16" Colt light-weight barrel.

Six 10-shot groups were fired in a row in a slow cadence. Those groups had extreme spreads of:

1.18”

1.92”

1.28”

2.53”

0.96”

2.24”

for an average extreme spread of 1.69”. Using RSI Shooting Lab, I over-layed all six groups on each other to form a 60-shot composite group. The composite group had a mean radius of 0.56”.

.....

 

[Molon]

I agree with the above, but what he’s showing is mean radius. Double that for how groups are usually measured

Triple that. See my above post.

....

 

[Vynz]

Maybe I’m just too easily pleased but even triple at 1.69MOA still seems spectacular for the hunting I do.

 

[rlsmith1]

Incorrect. While the outlying shot in the left upper quadrant is from group number three, the outlier in the right lower quadrant is from group number one.

There is no need to "allow each barrel to cool to ambient temp between groups" because all the shoots were fired in a slow cadence, so heat build-up was not a factor.

Really trying to understand here then... What would your conclusion be?

For the lightweight barrel below, most extreme outer impacts are mostly from either 2 or 3 (with most of them being from group 3). Essentially, if I look at the composite group and visualize taking the third group out, the mean radius should decrease. Interestingly, the outer impacts are more evenly dispersed for the M4 and HBAR barrels.

Maybe I'm overthinking it and want barrel heat to be an issue when the real issue is simply the barrel profile (and per Frank's comments, barrel quality)

 

[rlsmith1]

Also, why no love for carbon barrels in this application? Cost not being a factor...

 

[Frank Green]

Also, why no love for carbon barrels in this application? Cost not being a factor...

Are you talking chrome moly steel barrels vs stainless steel barrels?

I've got nothing against CM steel barrels. Shoot just as good as SS barrels and no difference in barrel life. I've had plenty match rifles both service rifles and bolt gun match rifles with CM barrels and where just hammers.

The CM isn't as forgiving when it comes to rust/corrosion.

So nothing to be gained by using a CM barrel at all.

 

[rlsmith1]

Are you talking chrome moly steel barrels vs stainless steel barrels?

I've got nothing against CM steel barrels. Shoot just as good as SS barrels and no difference in barrel life. I've had plenty match rifles both service rifles and bolt gun match rifles with CM barrels and where just hammers.

The CM isn't as forgiving when it comes to rust/corrosion.

So nothing to be gained by using a CM barrel at all.

Sorry, no I was wondering why more haven't voted for the carbon barrel which on paper give the best of both worlds. I know a lot goes into making a great steel barrel, let alone a steel / carbon barrel combo

 

[dms416]

It's not just the contour/heavier weight that will help you. It goes back to the quality of the barrel and the way it's been manufactured.

Button and hammer forged barrels work against you and it gets worse with a lighter weight contour and or if you do fluting and muzzle threading. Because of the way these barrels are made....as you turn it smaller/lighter and or flute it etc...the bore ends up opening up on you. Changing in size.

Later, Frank
Bartlein Barrels

In the myriad of CHF barrels I've had, be they Hodge, FN, DD, HK each individual barrel has its own unique personality.
You could wind up with a 1-1.5 MOA that will eat and love anything, one that doesn't print ANYTHING under 2.5 MOA, or something more picky and choosy.
Even the less-thick HK 416 barrels manage heat pretty well. Beyond them, it's a complete crap shoot. Some will walk in less than a mag. Others will hold true even when you can't hang onto the handguard without gloves.

From what I can tell, ya just don't know till ya know...which can be very frustrating.

 

[TonyTheTiger]

Sorry, no I was wondering why more haven't voted for the carbon barrel which on paper give the best of both worlds. I know a lot goes into making a great steel barrel, let alone a steel / carbon barrel combo

Because CF barrels are shit for high volume shooting.

 

[rlsmith1]

Because CF barrels are shit for high volume shooting.

Please elaborate

 

[TonyTheTiger]

Please elaborate

Around 2018 (IIRC) a bunch of 3 gunners got on the CF barrel bandwagon. Every single guy I talked to had significant stringing issues. The next season the CF barrels were replaced because they had all been smoked at less than 5k rounds. The one guy I know who still has one has problems with bullets coming apart after 40-50 rounds.

 

[rlsmith1]

Very interesting... Curious if newer barrels still have these issues? Burning barrels after 5k rounds isn't great for a small frame

 

[TonyTheTiger]

Very interesting... Curious if newer barrels still have these issues? Burning barrels after 5k rounds isn't great for a small frame

No idea, everyone I know gave up on them and aren't willing to give them another shot.
Not sure what the upsides are. Double the price, half the lifespan, same weight as a light profile steel barrel with more stringing from heat.

 

[Frank Green]

Guns like the HK416 with the gas piston system....are also prone to more accuracy issues. You have moving parts that cause harmonic and vibration issues. So they will be more inconsistent in terms of accuracy and how good the accuracy can be vs a gas impingement system like a standard M16?M4 gun.

 

[Northman623]

You may find this helpful. https://soldiersystems.net/2018/05/...s-system-testing-shows-increased-performance/ It you want answers that are based on anything other than opinions you should seek out people that actually do real testing. There is way more research along this path than you may realize. No need to complicate it.

https://static1.squarespace.com/static/597679b68419c2bc1f2f8ef1/t/598390fdb8a79b354102d3fb/1501794563797/CRANE+Test+Data+Mk18.pdf

https://apps.dtic.mil/sti/pdfs/ADA317929.pdf

The Story of the Government Profile Barrel - Everyday Marksman

The government profile barrel for the AR-15 is often mystery. Why would anyone design it to be skinny in the rear and wide in the front. Let's explore.

www.everydaymarksman.co

 

[dms416]

Guns like the HK416 with the gas piston system....are also prone to more accuracy issues. You have moving parts that cause harmonic and vibration issues. So they will be more inconsistent in terms of accuracy and how good the accuracy can be vs a gas impingement system like a standard M16?M4 gun.

While I greatly respect your knowledge,
This has not been the case at all in the dozen 416s if gotten to shoot over the course of a decade. They have been ridiculously accurate guns/barrels

 

[RUTGERS95]

Guns like the HK416 with the gas piston system....are also prone to more accuracy issues. You have moving parts that cause harmonic and vibration issues. So they will be more inconsistent in terms of accuracy and how good the accuracy can be vs a gas impingement system like a standard M16?M4 gun.

stop, just stop

single shots this is already proven false
fast follow up shots it's muscle memory and practice like anything else

 

[rlsmith1]

You may find this helpful. https://soldiersystems.net/2018/05/...s-system-testing-shows-increased-performance/ It you want answers that are based on anything other than opinions you should seek out people that actually do real testing. There is way more research along this path than you may realize. No need to complicate it.

https://static1.squarespace.com/static/597679b68419c2bc1f2f8ef1/t/598390fdb8a79b354102d3fb/1501794563797/CRANE+Test+Data+Mk18.pdf

Kind of irrelevant here... It's pretty much decided I'll run a midlength in a 14.5 for more reasons than just accuracy

 

[Northman623]

My post was made to point you in a direction. That would be Crane. Nobody beats a dead horse like they do. All the data has been developed in a lab for exactly what your talking about. I wouldn't trust anecdotal evidence, to many variables to draw a useful conclusion from.

 

[Frank Green]

While I greatly respect your knowledge,
This has not been the case at all in the dozen 416s if gotten to shoot over the course of a decade. They have been ridiculously accurate guns/barrels

I should've thrown in there an accuracy spec./requirement. What have you seen from an accuracy point of view?

I'm coming at it from a hard core accuracy side of things.

I've never seen data and or a piston gun that and I'll set the bar at shoot 1/2 to 3/4moa and due it consistently. Good ammo...good barrel.

Didn't mean to derail the thread that wasn't my intention.

From a combat reliability standpoint...I vote piston gun.

 

[TurboTrout]

General rifle as in??

If it’s hanging around a truck, or something, get something heavy

If you’re talking general like you’re walking miles with it, light

 

[Vynz]

This thread has some very high end experts posting in it with a bunch of great information. Could you add some context to this for people who aren’t as dialed in. Is this something for the guy shooting factory match who is looking at flags for wind estimations? Is it for guys doing handlods with 2fps SD, a kestrel and laser range finder? At what point do these barrel features really show their effects?

 

[rlsmith1]

Not sure if you're asking me or the people giving the advice... I tried to state in my original post what I'd like to do with this gun, just about everything! Below is my thought process / experience.

Weight: Needs to be as reasonable as a rifle can be with an LPVO (clip on thermal at night), laser, light and suppressor without sacrificing performance (hence the accuracy question)
Barrel: To me, 14.5" is a good balance of ballistic performance and maneuverability. If I really want to be maneuverable, I'll take the suppressor off. I really like the 12.5" barrels but for my distances (flat Midwest state), it just doesn't quite cut it (I know, guys shoot 600yds+ with 12.5's all the time)
Accuracy: Day or night, make accurate shots from 5 to 500 yards. Any further and I'll grab a large frame AR. Overall, a MOA rifle would be what I'm after, no real need to do 1/2 MOA but if I can get there reasonably then it will only make my job easier
Firing Schedule: It won't be a machinegun but I'm willing to carry an extra 6 oz of barrel if it lets me shoot accurately longer (and potentially more accurate from the start)

I really appreciate the experience in this thread and I don't mind if we hash out the DI vs Piston while we are at it . Personally I'm happy with my DI guns because if I get to where I wish I had a piston, I'll also wish I had a beltfed

 

[dms416]

I should've thrown in there an accuracy spec./requirement. What have you seen from an accuracy point of view?

I'm coming at it from a hard core accuracy side of things.

I've never seen data and or a piston gun that and I'll set the bar at shoot 1/2 to 3/4moa and due it consistently. Good ammo...good barrel.

Didn't mean to derail the thread that wasn't my intention.

From a combat reliability standpoint...I vote piston gun.

At least in the case of the HK stuff, it's in line with your comment about barrel quality. I and many others believe the success of the platform is not due to the op rod but the material package and barrel. I honestly can't speak on all op-rod piston guns as they aren't all the same.

In the context of what they are, they aren't hard to eek out MOA consistently. "Context" being that this is with OEM trigger, 2004/5 guns maybe getting a 1.1-4x24 Short Dot shooting factory ammo. In recent years, it's maybe upgraded to a 1-8x24 and with a Geissele. I honestly don't know what I could do with a PRS stock, handloads, proper optic. Could it get down to 1/2 MOA on the best of the best...probably.

With the exception of one dude's 20" 416 upper that shot Swiss Ruag 3/4 of an inch, I had a Geissele trigger and a 3-20x50 US as the optic:

While a bit thicker but still having chrome lining like the 416's (the US MR556's are not) the MR223a3's are very impressive. A colleague posted an impressive 100-round sub-MOA group with his 16" gun and a 6x Kahles on top:

Internally under a scope, the HK barrels look almost as slick as stainless match barrels compared to other CHF varieties.
If compared to a somewhat parallel like a Mk12 or 16" recon, I would quantify it as such:
The best HK is 85-90% of the accuracy of the comparable stainless
Most other CHF's, I'm happy with being able to jam 10x rounds well inside a B8 x-ring at 100y.

 

[GUNNER10]

After looking around, I haven't seen any real accuracy tests that consist of a 10 round group, 60-90 rounds shot quickly, followed by another 10 round group. Would be worth it if someone could do this and track accuracy every 100 rounds up to 500 rounds for a couple different barrel profiles from the same manufacturer. I'm still dialing in my gas gun fundamentals so I wouldn't be a good candidate for that. Oh and I don't have anything select fire

I'd love to hear any commentary on standard vs lightweight barrels' accuracy (1) after a string of fire (say 60-90 rounds to heat things up) and (2) how sensitive they are to attaching a suppressor (the one on this gun will be ~14 oz with the muzzle device). I think it is pretty much agreed that lightweight barrels are generally in the same realm of accuracy as their standard weight counterparts for the first few rounds. I'm just wanting to understand at what point does a heavier profile or carbon barrel make sense.

I ask because I am putting together a general purpose 14.5" and I want to keep things as light as possible since I will be running a suppressor, LPVO, light, and laser. For now, I have picked up a cheap (used) standard weight barrel that is in the 31 oz range and it is very useable, but taking half a pound off would be nice. I have also considered a Proof barrel in a standard contour but want to make sure they are durable (most of the barrel will be tucked under a MK8 handguard).

My use case would be everything from defense to coyotes and general training during the day and night. I'm pretty agnostic to stainless vs CM but if I go CM it will be a Criterion Core or Hybrid. I have not owned a lightweight AR barrel before mainly because of sustained accuracy concerns but I don't want to box myself in either

Anecdotally,

I would lean towards a heavier profile with a good sling, but it really depends on what you shooting. if you are shooting man sized steel, a LW barrel would do fine. If you are shooting for groups not so much.

 

[GUNNER10]

Not sure if you're asking me or the people giving the advice... I tried to state in my original post what I'd like to do with this gun, just about everything! Below is my thought process / experience.

Weight: Needs to be as reasonable as a rifle can be with an LPVO (clip on thermal at night), laser, light and suppressor without sacrificing performance (hence the accuracy question)
Barrel: To me, 14.5" is a good balance of ballistic performance and maneuverability. If I really want to be maneuverable, I'll take the suppressor off. I really like the 12.5" barrels but for my distances (flat Midwest state), it just doesn't quite cut it (I know, guys shoot 600yds+ with 12.5's all the time)
Accuracy: Day or night, make accurate shots from 5 to 500 yards. Any further and I'll grab a large frame AR. Overall, a MOA rifle would be what I'm after, no real need to do 1/2 MOA but if I can get there reasonably then it will only make my job easier
Firing Schedule: It won't be a machinegun but I'm willing to carry an extra 6 oz of barrel if it lets me shoot accurately longer (and potentially more accurate from the start)

I really appreciate the experience in this thread and I don't mind if we hash out the DI vs Piston while we are at it . Personally I'm happy with my DI guns because if I get to where I wish I had a piston, I'll also wish I had a beltfed

Have you considered getting a decent tripod to mitigate some of the issues with weight and shooting at night?

 

[rlsmith1]

Have you considered getting a decent tripod to mitigate some of the issues with weight and shooting at night?

I actually already have one and it’s one of the better purchases I’ve made for shooting at night. I’d rather not be reliant on that if I don’t have to though (but it’s like a portable shooting bench)

 

[Molon]

Really trying to understand here then... What would your conclusion be?

For the lightweight barrel below, most extreme outer impacts are mostly from either 2 or 3 (with most of them being from group 3). Essentially, if I look at the composite group and visualize taking the third group out, the mean radius should decrease. Interestingly, the outer impacts are more evenly dispersed for the M4 and HBAR barrels.

Maybe I'm overthinking it and want barrel heat to be an issue when the real issue is simply the barrel profile (and per Frank's comments, barrel quality)

You're trying to see something that just isn't the case and ignoring the data that doesn't fit your preconceived notion. As I stated above, heat build-up was not an issue for those groups because all of the shots were fired in a slow cadence. If your hypothesis was correct, then the smallest group that could possibly be obtained with the light-weight barrel would be the first group fired and group sizes would get progressively larger with each succeeding group with the last group fired being the largest group, yet that's just not what happens on a regular basis.

Here's the data that I posted above from a different Colt 16" light-weight barrel from six 10-shot groups fired in a row in a slow cadence.

Six 10-shot groups were fired in a row in a slow cadence. Those groups had extreme spreads of:

1.18”

1.92”

1.28”

2.53”

0.96”

2.24”

for an average extreme spread of 1.69”. Using RSI Shooting Lab, I over-layed all six groups on each other to form a 60-shot composite group. The composite group had a mean radius of 0.56”.

If your hypothesis was correct, the first group would have had the smallest extreme spread, but that wasn't the case. The fifth group had the smallest extreme spread.

If your hypothesis was correct, the third group would have had a larger extreme spread than the second group, but that wasn't what happened.

If your hypothesis was correct, the sixth group would have had the largest extreme spread, but that wasn't the case. The fourth group had the largest extreme spread.

In the first example that I posted that only had three 10-shot groups, it was just the "luck of the draw" for that particular set of groups.




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