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18" Versus 22" Barrel Velocity

This is a discussion on 18" Versus 22" Barrel Velocity within the Ammunition forums, part of the M14 M1A Forum category; Hey Guys, I've been wondering what the Difference in Bullet Speed between the 18" and the 22" M1A's. I did a Search and only found ...


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Old January 18th, 2010, 01:56 PM   #1
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Smile 18" Versus 22" Barrel Velocity

Hey Guys,

I've been wondering what the Difference in Bullet Speed between the 18" and the 22" M1A's.

I did a Search and only found Chrony Results for the 22 Incher:

Tried to Post a link to the 22" here,, but program wouldn't allow it. Sorry.

I'm sure that the 18" Speeds are here somewhere,, but my search's didn't find it.

Should be helpful for those on the Fence and Trying to decide, and for One's in the Future thinking of Modification,
Joe

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Old January 18th, 2010, 02:51 PM   #2
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There is no one right answer for your question. For a 308 I use 35fps per inch. So for a 18 vs 22, lose a 140fps for the 18incher.
No 2 rifle barrels are the same, much-less standard deviation of a given rounds speed.

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Old January 18th, 2010, 03:43 PM   #3
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Originally Posted by Citizen 64 View Post
There is no one right answer for your question. For a 308 I use 35fps per inch. So for a 18 vs 22, lose a 140fps for the 18incher.
No 2 rifle barrels are the same, much-less standard deviation of a given rounds speed.
Hey Citizen,

That sounds about right. I'm thinking as a general rule about 35 to 45 an Inch.

So I'm figureing about 140 to 185 or so. But just a General guess on my part. Might be more,, might be less.

But like you said,, it has many variable's, Temp, Bullet Weight, Rifleing, and I'm sure that the list can go on and on.

SpringField said,, about 40 to 70 fps loss from 18" to 16 1/2 Inch.

I studied the Post on the 18" Chrono,, and it seemed like the 22" Barrel is just about optimum in regards to Factory Stated Bullet Speed.

Looking at the Ammo for sale,, and the Speed's listed for the Different Types and Bullet Weight,, and with the 180 Grain down to right at 2600 fps. Then taking away another 140 to 180 fps ~ That can make a difference in Bullet Flight.

I'm sure that someone has ChronoGraphed the M1A 18 Incher's,, and hopefully they'll post what they found in 308 winchester,
Joe

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Old January 18th, 2010, 04:25 PM   #4
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My go to load for M14/M1a is - LC 97 Match brass, 42grs of H4895, 175 SMK bullet, Fed GM primers.
2650fps from my 22inch M14, and 2425fps from my 16.5 inch M1a.

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Old January 18th, 2010, 07:39 PM   #5
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Quote:
Originally Posted by Citizen 64 View Post
My go to load for M14/M1a is - LC 97 Match brass, 42grs of H4895, 175 SMK bullet, Fed GM primers.
2650fps from my 22inch M14, and 2425fps from my 16.5 inch M1a.
Citizen,

Good information for sure,, and seems to be very accurate.

Much Appreciated,, Thank You.

Hope someone will post on 180 Grain,, as well,, but 175 Grain,, is awful close,
Joe

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Old January 18th, 2010, 08:29 PM   #6
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Slightly Off Topic.

Of general interest: an Army armorer taught me that the larger the bore diameter of the weapon the less effect barrel shortening has because length X pi X the radius squared equals the volume (of the bore).

V/r,

2beers

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Old January 18th, 2010, 10:07 PM   #7
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We'll take your word for it, but I think it basically boils down to there is a smaller percentage of the total bore volume in those 4 inches with a larger bore than a smaller one.

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Old January 18th, 2010, 11:02 PM   #8
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Here is a good article on barrel lengths, accuracy, and velocity. Granted this is dealing with bolt action rifles, but it does have some very good points. http://www.tacticaloperations.com/sw...000/index.html

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Old January 19th, 2010, 05:32 AM   #9
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Austrailian averaged 2680 from my 18'' scout 2725 from my standard.

Federal sent me an email when I inquired about velosity loss of the 168 gr match and was given 15 FPS PER INCH loss from 22 -18

HTH

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Old January 19th, 2010, 06:02 AM   #10
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Austrailian averaged 2680 from my 18'' scout 2725 from my standard.

Federal sent me an email when I inquired about velosity loss of the 168 gr match and was given 15 FPS PER INCH loss from 22 -18

HTH
Standard Deviation for 100rds of Fed. 168GM is over 20fps, depending on lot# of course. It is in my testing the most consistent & accurate commercial load available, and almost impossible to beat by handloading.
That's from my former employers HS Precision's test rig with 24inch barrel & nearly 5 yrs of testing.
If your only losing 11.25fps per inch with that load and your happy with it's accuracy I'd stock-up on one lot # of it and never look back. Quality of your rifles is to be envied as well.

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Old November 14th, 2014, 08:34 PM   #11
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Quote:
Originally Posted by billy2beers View Post
Of general interest: an Army armorer taught me that the larger the bore diameter of the weapon the less effect barrel shortening has because length X pi X the radius squared equals the volume (of the bore).

V/r,

2beers
Respectfully, I believe that the armorer had it backwards. It is my understanding that the smaller the bore diameter, the less effect shortening the barrel has. With that equation, shortening a .308 barrel by an inch would reduce volume significantly more than an equal reduction in .22 LR because the radius is squared. That increases the impact of R geometrically.

I am not certain that my logic applies here. Glancing over the data at ballistics theinch.com does appear to support my theory. At least looking at the drop from 6" down to 4" with most pistol calibers.


Last edited by TheTinMan; November 15th, 2014 at 09:25 AM. Reason: Incorrect apparently
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Old November 15th, 2014, 05:53 AM   #12
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Given medium burning powders, expect 25 fps per inch of barrel.

Slow powders will have a greater difference, fast powders may have less.

The more bore volume you have (larger caliber), the less difference there is.

Thanks from hammonje
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Old November 15th, 2014, 06:24 AM   #13
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Good reference. I know there are some websites that show changes per caliber and per inch even but can't seem to find one atm.

http://www.chuckhawks.com/rifle_barrel.htm

Thanks from NateP
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Old November 15th, 2014, 06:26 AM   #14
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Here ya go. Good website full of useful info.

http://www.ballisticsbytheinch.com/

Thanks from NateP
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Old November 15th, 2014, 06:32 AM   #15
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Another good read.

http://www.thetruthaboutguns.com/201...-and-accuracy/

Thanks from TheTinMan and NateP
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