Go Back   Maryland Shooters > The Arsenal > Rifles
Don't Have An Account? Register Here

Join MD Shooters

Reply
 
Thread Tools Display Modes
Old September 25th, 2018, 02:07 PM #11
Boats's Avatar
Boats Boats is offline
Booze, Bikes n Boomsticks
 
Join Date: Mar 2012
Posts: 372
Boats Boats is offline
Booze, Bikes n Boomsticks
Boats's Avatar
 
Join Date: Mar 2012
Posts: 372
TTAG covered this with an actual scientific test.


https://www.thetruthaboutguns.com/20...ccuracy/lready covered, the accuracy difference of long vs short barrels is a myth.

So did rifle shooter


https://rifleshooter.com/2014/12/308...ty-28-to-16-5/

The difference is velocity, which in long range shooting means the bullet hits transonic velocity sooner, which is the biggest influencing factor on long range accuracy. However, even on the extremes, the difference on velocity between a 28"barrel and a 16.5" barrel is about 300 fps.

Honestly, working up the right load that works best with your barrel and action is more important than agonizing over barrel length.

From a personal standpoint, I have found that Australian Outback .308 nets me sub-moa at 200 yds out of a 16.5"aAR10 and is still super Sonic at 700yds. It even does 1"groups @ 100 out of a Springer Socom II, which previously struggled to do 4" at the same range with XM20C
__________________
The contents of the above post may not be safe for children, expectant mothers, or the elderly. The above post should probably not be taken seriously but should be taken with a quart of whisky. Misuse of the above post may cause rash, infection, joint pain, bleeding gums, car trouble, bad weather, black mold and/or anal seepage.
Boats is offline   Reply With Quote
Old September 25th, 2018, 02:17 PM #12
OLM-Medic's Avatar
OLM-Medic OLM-Medic is offline
Senior Member
 
Join Date: May 2010
Location: Pennsylvania
Posts: 4,004
OLM-Medic OLM-Medic is offline
Senior Member
OLM-Medic's Avatar
 
Join Date: May 2010
Location: Pennsylvania
Posts: 4,004
I'm not a fan of longer barrels.

A lot of people have shown me that 16" , 14.5" and sometimes even 12.5" .223 barrels can still do fine at internediate range. I regret getting a 18" .223 barrel at all.

It does cause less velocity, which means more drop and more wind influence, and thus more narrow margin of error in theory, but not by a lot.

It also will effect the range at which your bullet turns trans sonic (which means barely supersonic), which is the most unstable part of flight.

I wouldn't worry about any of this unless you're going longer ranges, like >600y.
OLM-Medic is offline   Reply With Quote
Old September 25th, 2018, 02:41 PM #13
squaregrouper's Avatar
squaregrouper squaregrouper is online now
Vote SG For King
 
Join Date: Sep 2009
Location: Pikesville, Peoples Republik Of Marylandistan
Posts: 7,930
Images: 1
squaregrouper squaregrouper is online now
Vote SG For King
squaregrouper's Avatar
 
Join Date: Sep 2009
Location: Pikesville, Peoples Republik Of Marylandistan
Posts: 7,930
Images: 1
Quote:
Originally Posted by danb View Post
Everyone knows Mini-14 is a tack driving all powerful sniper rifle as seen in movies and video games.
Well, duh...
Attached Images
 
__________________
Nothing posted on this forum should be considered legal advice. If you are in need of legal advice, I advise you to seek your own counsel. Hell, I'm not even a lawyer, but this got your attention.
squaregrouper is online now   Reply With Quote
Old September 25th, 2018, 02:45 PM #14
moose&squirrel moose&squirrel is offline
Junior Member
 
Join Date: Aug 2018
Posts: 28
moose&squirrel moose&squirrel is offline
Junior Member
 
Join Date: Aug 2018
Posts: 28
Quote:
Originally Posted by E.Shell View Post
The term "Accuracy" is often interchanged with "Precision".

A longer barrel may prove more accurate, in that holding a consistent point of aim may be easier due to increased mass and/or sight radius.

A shorter barrel is often more precise, because for any given diameter or profile, making the barrel shorter makes it stiffer and thus less reactive.

You can see evidence of this by noticing most benchrest rifles have shorter barrels that are stiffer and more precise, while most position rifles are longer and heavier so the shooter can control them better and/or to provide a longer sight radius, both helping to achieve better accuracy.

That said, I have seen several 16" .308s shoot sub-MOA groups out to 1,200 yards. It is mostly a function of barrel quality, but the shooter really has to be focused to shoot a short rifle from field positions with repeatable precision.

One aspect of long range accuracy one will give up with a shorter barrel is that the reduction in muzzle velocity means longer flight time and more sensitivity to conditions. On a known distance course, extra drop isn't a big issue. Conversely, on an unknown distance course, when shooting your own range estimates, increased drop places greater emphasis on your ability to correctly range targets and tends to compound your errors. Wind drift will be greater on any type course and giving up velocity means your drift will be worse and your calls have to be better.
1200 yards? I doubt I could see a target at 1200 yards out of Mount Palomar's telescope!
moose&squirrel is offline   Reply With Quote
Old September 25th, 2018, 02:55 PM #15
danb's Avatar
danb danb is offline
nope nope nope nope
 
Join Date: Feb 2013
Location: Howard County
Posts: 16,427
danb danb is offline
nope nope nope nope
danb's Avatar
 
Join Date: Feb 2013
Location: Howard County
Posts: 16,427
Quote:
Originally Posted by squaregrouper View Post
Well, duh...
I see your George Peppard and raise you George Clooney. Fool!

danb is offline   Reply With Quote
Old September 25th, 2018, 04:32 PM #16
OLM-Medic's Avatar
OLM-Medic OLM-Medic is offline
Senior Member
 
Join Date: May 2010
Location: Pennsylvania
Posts: 4,004
OLM-Medic OLM-Medic is offline
Senior Member
OLM-Medic's Avatar
 
Join Date: May 2010
Location: Pennsylvania
Posts: 4,004
Quote:
Originally Posted by moose&squirrel View Post
1200 yards? I doubt I could see a target at 1200 yards out of Mount Palomar's telescope!
I bet you could see it with a regular 12x scope
OLM-Medic is offline   Reply With Quote
Old September 26th, 2018, 12:35 AM #17
K-43's Avatar
K-43 K-43 is offline
East of Wonder Woman
 
Join Date: Oct 2010
Location: PG
Posts: 842
K-43 K-43 is offline
East of Wonder Woman
K-43's Avatar
 
Join Date: Oct 2010
Location: PG
Posts: 842
Quote:
Originally Posted by danb View Post
I see your George Peppard and raise you George Clooney. Fool!
You can't raise with and anti-2A Libtard.
__________________
No Pollo a la Brasa MCC
K-43 is offline   Reply With Quote
Old September 26th, 2018, 09:50 AM #18
E.Shell's Avatar
E.Shell E.Shell is offline
Senior Member
 
Join Date: Feb 2007
Location: AA & DorCo
Posts: 5,986
E.Shell E.Shell is offline
Senior Member
E.Shell's Avatar
 
Join Date: Feb 2007
Location: AA & DorCo
Posts: 5,986
Quote:
Originally Posted by Boats View Post
TTAG covered this with an actual scientific test.

https://www.thetruthaboutguns.com/20...ccuracy/lready covered, the accuracy difference of long vs short barrels is a myth.
Bad link, maybe dropped or moved...

The title of the article does beg the question: Are we actually talking about "accuracy" or "precision"?

If we are talking about "precision", then no, barrel (and installation) quality is the prevailing factor and length is a minor factor. I had said this in my post above. In benchrest where PRECISION is the goal and precision is measured in thousandths of an inch and not MOA, the trend went to shorter, more rigid barrels 20 years ago. You won't find one on the line right now more than about 21 or 22". Those guys really do know a bunch about precision.

If we are talking about "accuracy", a completely different concept than "precision", then in order to believe there is no difference in barrel length, we would have to believe that, with equal quality barrels, it is just as easy to shoot good groups unsupported with a 16" barrel as it would be with a 26" barrel. I would reject this notion. The 26" barrel provides greater mass out front and is far less reactive to handling issues. If we use iron sights, then the longer barrel provides an even greater ACCURACY advantage by having a longer sight radius. Don't see many high power competitors sporting 16" HBARs, although they are much easier to carry...

So again, what are you talking about, accuracy or precision?
Yeah, I saw that when it was published... I didn't really know how to take the data, but if you pick it apart, there is some useful info.

On one hand, I'd like to just toss it out, because 5 round groups of non-match ammo tells us almost nothing and we cannot access the raw data, only some dubious averages. When we have milsurp type ammo, or ammo emulating ball ammo, we normally have very poor velocity control because velocity control isn't the critical parameter. Feeding through auto and semi-auto rifles and going BANG every time is vastly more important, just for starters. Durability, temperature stability, waterproofing...anything but precise velocity control, but hey, let's use this this crap as a test control anyway, LOL.

IMO, the only ammo worth looking at in that test is the FGMM 168. I have found FGMM 168s to reliably deliver 7-9 fps SD numbers through full length rifles and that should be close enough to provide meaningful results.

On the other hand, the sparse and poorly presented data actually does prove one of my points too.

FWIW, I currently have a LabRadar chronograph and also have a Magneto-Speed that I used before that, and before the Magneto-Speed I used a borrowed Ohler 35p quite a bit. I have also had a couple of the junk chronographs. We have chronographed many rounds of ammo through hundreds of rifles, both in load development and in ballistic analysis. The statements I had made above are grounded in facts and field evidence.

The missing raw test data is extremely important here, as evidenced by the otherwise unexplained jumps in velocity. It is simply not logical to accept that between 20" and 19" we lost 33 fps, but only lost 9 fps between 19" and 18", but THEN, we lost 42 fps between 18" and 17". CLEARLY, the data is flawed, and in at least two ways. That's OK though, we'll play it out with YOUR data source anyway.

First flaw is that the 5 round sample size is insufficient and greater samples will help to smooth out these obvious aberrations. Seriously, for another hundred bucks worth of ammo, we could have really seen something valid.

The next flaw, as I had mentioned above, ES and SD numbers start to get BIG when the barrel gets too short and the erratic test results are suspect. Big velocity deviations mean that some rounds depart pretty far from the median value. When we start getting rounds that jump away from the average, the average is skewed and of little scientific value in this context. All it takes is one or two rounds from the rather limited 5 round sample to move the average away from the median value, so when we see ridiculous jumps in velocity, as shown in the test results, we are seeing the effects of increased deviation. This sorta proves my point regarding increasing deviation in shorter barrels.

Question: How is this, albeit limited, information not showing us excessive deviation?

Looking at velocity loss per inch, but trying to make these numbers make sense is a bit of a stretch, but we can try.

If we took any three consecutive numbers and smoothed the average - like if we take the 20 to 19, the 19 to 18, then the 18 to 17, we would have a SLIGHTLY better picture of what was going on, and we have an average loss of 29 fps per inch in this barrel length span. If we go to the 28 to 27, then the 27 to 26, then the 26 to 25, we get an average of 16 fps per inch in this barrel length span. This sorta proves my point about losing increasing amounts of velocity as we get to the short end.

Question: How can we say that velocity loss is linear throughout a barrel length range of 16" to 26" when there is a demonstrable difference?

Thank you for linking the data we could use to demonstrate what's happening.

If you were to read my posts above, you will see that this is EXACTLY what I had said was going on. This would take far less analysis and be much easier to see were the raw data published instead of relying on averages based on statistically marginal sample sizes.
Quote:
The difference is velocity, which in long range shooting means the bullet hits transonic velocity sooner, which is the biggest influencing factor on long range accuracy.
While crossing the transonic boundary does upset some bullets and is generally considered detrimental to precision (and consequently accuracy), the effects are often overrated. We shoot FGMM 175s to 1,200 yards and many 16" 7.62/.308 rifles have no trouble keeping sub-MOA groups. According to the ballistic calcs, we went transonic (generally accepted to be about 1,125 fps (https://en.wikipedia.org/wiki/Transonic)) back at 850 yards. I would suggest that in theory, there is no difference between theory and field testing, but field testing often proves otherwise.

If we did exactly the same thing with the Sierra 168s (as loaded by FGMM) we would typically destabilize shortly after going transonic and we would be lucky to hit a 12 x 16" target at 900 AT ALL.
Quote:
However, even on the extremes, the difference on velocity between a 28"barrel and a 16.5" barrel is about 300 fps.
Which is like changing cartridges. ADD 300 fps to a .308 and you have a .300 WinMag. Take 300 away and it's a .30-30...
Quote:
Honestly, working up the right load that works best with your barrel and action is more important than agonizing over barrel length.
Good advice if one already has the barrel. When choosing barrel length, it's nice to have correct information to balance one's needs between a light handy rifle and one capable of enhanced long range performance.
__________________
The beatings will continue until morale improves.

"None are so hopelessly enslaved as those who falsely believe they are free" - J. W. Von Goethe
E.Shell is offline   Reply With Quote
Old September 26th, 2018, 09:54 AM #19
E.Shell's Avatar
E.Shell E.Shell is offline
Senior Member
 
Join Date: Feb 2007
Location: AA & DorCo
Posts: 5,986
E.Shell E.Shell is offline
Senior Member
E.Shell's Avatar
 
Join Date: Feb 2007
Location: AA & DorCo
Posts: 5,986
Quote:
Quote:
Originally Posted by moose&squirrel View Post
1200 yards? I doubt I could see a target at 1200 yards out of Mount Palomar's telescope!
Quote:
Originally Posted by OLM-Medic View Post
I bet you could see it with a regular 12x scope
Yup, you can. A lot of the milspec and SWAT guys run 10x max and we make hits with that just fine. Hell, you can almost see it with the nekid eye.
__________________
The beatings will continue until morale improves.

"None are so hopelessly enslaved as those who falsely believe they are free" - J. W. Von Goethe
E.Shell is offline   Reply With Quote
Old September 26th, 2018, 06:49 PM #20
lazarus lazarus is offline
Senior Member
 
Join Date: Jun 2015
Posts: 3,746
lazarus lazarus is offline
Senior Member
 
Join Date: Jun 2015
Posts: 3,746
Quote:
Originally Posted by E.Shell View Post
The term "Accuracy" is often interchanged with "Precision".

A longer barrel may prove more accurate, in that holding a consistent point of aim may be easier due to increased mass and/or sight radius.

A shorter barrel is often more precise, because for any given diameter or profile, making the barrel shorter makes it stiffer and thus less reactive.

You can see evidence of this by noticing most benchrest rifles have shorter barrels that are stiffer and more precise, while most position rifles are longer and heavier so the shooter can control them better and/or to provide a longer sight radius, both helping to achieve better accuracy.

That said, I have seen several 16" .308s shoot sub-MOA groups out to 1,200 yards. It is mostly a function of barrel quality, but the shooter really has to be focused to shoot a short rifle from field positions with repeatable precision.

One aspect of long range accuracy one will give up with a shorter barrel is that the reduction in muzzle velocity means longer flight time and more sensitivity to conditions. On a known distance course, extra drop isn't a big issue. Conversely, on an unknown distance course, when shooting your own range estimates, increased drop places greater emphasis on your ability to correctly range targets and tends to compound your errors. Wind drift will be greater on any type course and giving up velocity means your drift will be worse and your calls have to be better.
Your last. Now, for target shooting with known ranges or a laser range finder there is really only wind effect that influences precision. However for practical shooting a longer barrel, with higher velocity, means the round is flatter reducing the impact of error from the shooter on estimating range quickly (and possibly inaccurately) as well as wind drift.

The difference in practical accuracy between 16” and 18” is likely to be minimal even at reasonably long ranges.

I am building an 18” AR-10 instead of 16” for many reasons though. The 50fps extra muzzle velocity is just that tiny bit of extra energy at the target, slight bit flatter shooting, slight but less wind drift, slightly easier to hold steady off hand and field positions and a fair amount reduced muzzle blast (IMHO there is a noticeable difference between a 16” and 18” .308 barrel for blast)

I’d go 20” for more of all of that, but as this is going to be a hunting rifle, there I feel like I am compromising more on weight and difficulty maneuvering in brush outweighing the other benefits I am gaining. Why I went with a 18” for my 6.5 grendel AR-15
lazarus is offline   Reply With Quote
Reply

  Home Page > Forum List > The Arsenal > Rifles


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 01:06 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
2018, Congregate Media, LP Privacy Policy Terms of Service