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Posted: 3/23/2009 5:44:31 PM EDT
I'm looking at purchasing either an 18.5" or 20" barrel from Fulton Armory. Is there going to be much of an accuracy difference in the two barrels? The 20" barrel is .920" and the 18.5" is .875".

Thanks,
Mark
Link Posted: 3/23/2009 5:56:33 PM EDT
Not really. Maybe 40-50 fps at the most.
Link Posted: 3/23/2009 6:01:09 PM EDT
Originally Posted By SilentMark:
I'm looking at purchasing either an 18.5" or 20" barrel from Fulton Armory. Is there going to be much of an accuracy difference in the two barrels? The 20" barrel is .920" and the 18.5" is .875".

Thanks,
Mark


Likely NO accuracy difference. A SLIGHT velocity advantage to the longer barrel. 308 gas gun has a hard time making it to 1000 yards anyway but if you want to try, go with the longer barrel, and preferably, a 24" barrel. If that isn't in your plans, either the 20 or 18.5 would be fine.

-David
Edgewood, NM
Link Posted: 3/23/2009 6:11:59 PM EDT
I'm just looking for something that can reach out to about 500-600 yards at most.

Thanks,
Mark
Link Posted: 3/23/2009 8:31:19 PM EDT
Either will get out to 500 yards with the proper optics and shooting skills.
Link Posted: 3/23/2009 9:01:01 PM EDT
you wont make it to 1k with either, go with 18" the best for 308 unless you need to get to 1K
Link Posted: 3/23/2009 9:03:26 PM EDT
Originally Posted By TaylorWSO:
you wont make it to 1k with either, go with 18" the best for 308 unless you need to get to 1K


Is that just for gas guns? I know that a few boltgun guys are running 18" to 1k without issue.
Link Posted: 3/24/2009 7:37:13 AM EDT
Originally Posted By yekimak:
Originally Posted By TaylorWSO:
you wont make it to 1k with either, go with 18" the best for 308 unless you need to get to 1K


Is that just for gas guns? I know that a few boltgun guys are running 18" to 1k without issue.


The guys running 18" 308 bolt guns are running a SHITLOAD of elevation to get there and they are having SERIOUS wind problems too. It's not about getting the bullet to 1000 yards. Any 308 will do that. It's about getting it there supersonic and hitting something with it. The 18" guys may be hitting something at 1000 yards but it isn't a small target and it isn't windy.

And yes, you can run a bolt gun harder than a gas gun. More powder = faster bullet.

-David
Edgewood, NM
Link Posted: 3/24/2009 8:13:46 AM EDT
Originally Posted By yekimak:
Originally Posted By TaylorWSO:
you wont make it to 1k with either, go with 18" the best for 308 unless you need to get to 1K


Is that just for gas guns? I know that a few boltgun guys are running 18" to 1k without issue.


Are they getting it there accurately or just getting it there?

If they are running 18" and getting super to 1k then they are running hot as hell.
Link Posted: 3/24/2009 11:09:34 AM EDT
Apologies first, I don't have an AR10 or the like, I was solely interested in the topic of barrel length and was extremely curious if things were that different with gas guns.

The owner of the 'hide has mentioned his 18" gun a couple times and IIRC people some were using 155gr Scenars to keep things flatter. I am just trying to get this clear in my head as I was told that I could not do 1k with my 20" bolt gun when I bought it. After getting it I stumbled across a few articles on the subject as well as a subgroup of snubbysnipers. My Range only does 600, but there are some wide open spaces around where (hoping that this present ices age ends soon) I may be able to shoot at longer ranges.

Anyhow, a couple of links.
http://www.sniperschool.com/barrel-length-revisited/
http://www.tacticaloperations.com/SWATbarrel/

The first article is a follow up on a previous article that stated that he was only a couple of MOA off at 1k with a shorter barrel.

THe second article did not talk about shooting distance too much, but said that there was a negligible muzzle velocity between difference between 18" and 20".

Anyhow, I am unsure how this will relate to a gas gun and I hope I did not shit on the thread too much.
Link Posted: 3/24/2009 11:14:05 AM EDT
Originally Posted By yekimak:
Apologies first, I don't have an AR10 or the like, I was solely interested in the topic of barrel length and was extremely curious if things were that different with gas guns.

The owner of the 'hide has mentioned his 18" gun a couple times and IIRC people some were using 155gr Scenars to keep things flatter. I am just trying to get this clear in my head as I was told that I could not do 1k with my 20" bolt gun when I bought it. After getting it I stumbled across a few articles on the subject as well as a subgroup of snubbysnipers. My Range only does 600, but there are some wide open spaces around where (hoping that this present ices age ends soon) I may be able to shoot at longer ranges.

Anyhow, a couple of links.
http://www.sniperschool.com/barrel-length-revisited/
http://www.tacticaloperations.com/SWATbarrel/

The first article is a follow up on a previous article that stated that he was only a couple of MOA off at 1k with a shorter barrel.

THe second article did not talk about shooting distance too much, but said that there was a negligible muzzle velocity between difference between 18" and 20".

Anyhow, I am unsure how this will relate to a gas gun and I hope I did not shit on the thread too much.


A couple of MOA means a couple of FEET at 1K.
Link Posted: 3/24/2009 11:41:29 AM EDT
[Last Edit: 3/24/2009 12:04:08 PM EDT by nmmi9100]
Read the two articles. Doesn't say a damn thing about windage. And Notice, never a word about actual measured muzzle velocities out of the 18" to 20" barrels and not a word about 5 to 10 shot groups at long range (in excess ove 600 yards).

Sure, a shorter barrel is stiffer and more accurate at close range. However, when it gets to bucking wind at long range, that's a different story. High Velocity and High ballistic coefficient make all the difference. You can't get high velocity out of an 18" barrel. Therefore you can't get an 18" barrelled 308 to shoot accurately at 1000 yards unless you only shoot on calm days. Real world shooting doesn't allow you to restrict your shooting to when the wind is calm.

It's a joke to believe 155 gr Scenars will shoot flatter than 175 SMKs out of the same gun at long range. They'll shoot a bit flatter to 500 yards or so, then the heavy bullet will pass the Palma bullets.

And yes, 2 MOA at 1000 yards is a bit over 20 inches. And 5 MOA is a bit over 50 inches. Pretty substantial difference, even in 308.

-David
Edgewood, NM
Link Posted: 3/24/2009 11:58:11 AM EDT
Originally Posted By TaylorWSO:

Originally Posted By yekimak:

Originally Posted By TaylorWSO:

you wont make it to 1k with either, go with 18" the best for 308 unless you need to get to 1K


Is that just for gas guns? I know that a few boltgun guys are running 18" to 1k without issue.


Are they getting it there accurately or just getting it there?

If they are running 18" and getting super to 1k then they are running hot as hell.


Would a "normal" load out of a semi-auto with an 18" bbl still be supersonic at 800m ?

(I'm guessing that it most likely would be ...)

Link Posted: 3/24/2009 12:11:34 PM EDT
Originally Posted By Winn:

Would a "normal" load out of a semi-auto with an 18" bbl still be supersonic at 800m ?

(I'm guessing that it most likely would be ...)



depends on the load but it should be okay, with a nominal 2600'/sec and 168 SMK it will make it
Link Posted: 3/24/2009 12:18:06 PM EDT
Originally Posted By nmmi9100:
Read the two articles. Doesn't say a damn thing about windage. And Notice, never a word about actual measured muzzle velocities out of the 18" to 20" barrels and not a word about 5 to 10 shot groups at long range (in excess ove 600 yards).

Sure, a shorter barrel is stiffer and more accurate at close range. However, when it gets to bucking wind at long range, that's a different story. High Velocity and High ballistic coefficient make all the difference. You can't get high velocity out of an 18" barrel. Therefore you can't get an 18" barrelled 308 to shoot accurately at 1000 yards unless you only shoot on calm days. Real world shooting doesn't allow you to restrict your shooting to when the wind is calm.

It's a joke to believe 155 gr Scenars will shoot flatter than 175 SMKs out of the same gun at long range. They'll shoot a bit flatter to 500 yards or so, then the heavy bullet will pass the Palma bullets.


For the listed reasons are why professional counter-snipers like the Secret Service run 300 Win Mag in long, stiff barrels off a Rem 700 action. They do shoot out to 1200 yards and consider 600 to be short range for their equipment. High velocity and heavy bullets are the key to long range target hitting. Under the FWIW column the USSS has it's own custom gunsmiths and custom handloaders. Handloads are tailored to the locale they're operating at to account for things like air density, etc. They run the Win Mag hot and barrels might last 1000 rds but often less.
Link Posted: 3/24/2009 1:11:20 PM EDT
What makes "supersonic" so critical?

Supersonic in air != supersonic in target
Link Posted: 3/24/2009 1:25:08 PM EDT
Originally Posted By TaylorWSO:
Originally Posted By Winn:

Would a "normal" load out of a semi-auto with an 18" bbl still be supersonic at 800m ?

(I'm guessing that it most likely would be ...)



depends on the load but it should be okay, with a nominal 2600'/sec and 168 SMK it will make it



Find me an 18" barrelled gun that will launch a 168 SMK at 2600 fps. Doesn't exist.

-David
Edgewood, NM
Link Posted: 3/24/2009 1:32:49 PM EDT
Originally Posted By TheAvatar9265ft:
What makes "supersonic" so critical?

Supersonic in air != supersonic in target


Bullets start loosing stability when they get near the speed of sound (transsonic). Pressure waves and stuff.

In air, of course.

-David
Edgewood, Nm
Link Posted: 3/24/2009 1:42:57 PM EDT


Originally Posted By TheAvatar9265ft:
What makes "supersonic" so critical?

Supersonic in air != supersonic in target


The transition between supersonic and sub sonic is rough on the stability of a bullet.


Originally Posted By nmmi9100:
Read the two articles. Doesn't say a damn thing about windage. And Notice, never a word about actual measured muzzle velocities out of the 18" to 20" barrels and not a word about 5 to 10 shot groups at long range (in excess ove 600 yards).

Sure, a shorter barrel is stiffer and more accurate at close range. However, when it gets to bucking wind at long range, that's a different story. High Velocity and High ballistic coefficient make all the difference. You can't get high velocity out of an 18" barrel. Therefore you can't get an 18" barrelled 308 to shoot accurately at 1000 yards unless you only shoot on calm days. Real world shooting doesn't allow you to restrict your shooting to when the wind is calm.

It's a joke to believe 155 gr Scenars will shoot flatter than 175 SMKs out of the same gun at long range. They'll shoot a bit flatter to 500 yards or so, then the heavy bullet will pass the Palma bullets.

And yes, 2 MOA at 1000 yards is a bit over 20 inches. And 5 MOA is a bit over 50 inches. Pretty substantial difference, even in 308.

-David
Edgewood, NM


I am just getting into all this, so if a say something wrong, don't hesitate to correct me here but...

I don't think they said anything about windage because they saw the difference in velocity as negligible. Same with the elevation, they are already cranking 32, what is so bad about cranking 34 for example? When your bullet drop is already ~400 inches, it does not seem to me that 20 more is a big deal, but I may be wrong on that.

Just for kicks here is Lowlight, the guy who runs snipershide... http://www.youtube.com/watch?v=15qj032UJ1I

I found it in this thread on the hide.

I know it is just gongs that he is hitting, so there is no way to measure group size or effectiveness at that range, but it is fun to watch.




Link Posted: 3/24/2009 2:08:21 PM EDT
[Last Edit: 3/24/2009 2:08:47 PM EDT by Luckyorwhat]
Trust me, I know what I'm doing:) Even if it works it's still funny.

Link Posted: 3/24/2009 4:13:00 PM EDT
Originally Posted By nmmi9100:

Originally Posted By TaylorWSO:

Originally Posted By Winn:

Would a "normal" load out of a semi-auto with an 18" bbl still be supersonic at 800m ?

(I'm guessing that it most likely would be ...)


depends on the load but it should be okay, with a nominal 2600'/sec and 168 SMK it will make it


Find me an 18" barrelled gun that will launch a 168 SMK at 2600 fps. Doesn't exist.

-David
Edgewood, NM


So then what would be a "safe bet" in terms of minimum bbl. length with respect to bullets staying supersonic at 800 meters ... with consideration given to "standard loadings" and bullets ranging anywhere from 155 to 175 gr ?

20" bbl minimum ? ... to "ensure" a variety of bullets staying super at 800m

(Never really paid any attention to some of this stuff before)

Link Posted: 3/24/2009 7:11:16 PM EDT
My chrony readings for my 20" Titan is 2530 fps with Black Hills 175gr. According to the JBM ballistics table this should still be supersonic at 1000yds (1176fps @ 1000yds) this is 41.3 MOA of elevation. I have access to a 1050 yd shooting area and will be able to go in about a month and plan on trying out these rounds& some 168 & 178 Amax handloads. I have made hits with 178 Amax handloads from my Polytech M14s( 22"barrel), velocity was around 2550, if I remember correctly.
Link Posted: 3/24/2009 8:18:38 PM EDT
[Last Edit: 3/24/2009 8:20:26 PM EDT by nmmi9100]
The speed of sound varies with altittude and temperature. The denser the air, the faster sound travels.

If I planned to shoot 800 yards or further and was wedded to a 308 WIN, i'd go with a 24" barrel. I'm planning to buy or build a precision 308 this year. May get a Remington 5R and put it in an AICS or might just get an FN-SPR. Either one will have a 24" barrel. My current 1000 yard + guns are an AR-30 338 Lapua and an ALS 50BMG but i'd like to get an 800 yard + gun that is lighter and cheaper to shoot.

-David
Edgewood, NM
Link Posted: 3/28/2009 10:33:35 AM EDT
Originally Posted By nmmi9100:
Originally Posted By TaylorWSO:
Originally Posted By Winn:

Would a "normal" load out of a semi-auto with an 18" bbl still be supersonic at 800m ?

(I'm guessing that it most likely would be ...)



depends on the load but it should be okay, with a nominal 2600'/sec and 168 SMK it will make it



Find me an 18" barrelled gun that will launch a 168 SMK at 2600 fps. Doesn't exist.

-David
Edgewood, NM


That's not unrealistic.

My 18.5 inch Titan lobs factory 168gr FGGM at 2565 fps.

Heck, my 16-inch SOCOM still gets 2500 fps with 168 FGMM.
Better yet, with 165 grain factory-loaded Fed. Bear Claws, the SOCOM gets 2585 fps.

My Titan will consistantly keep 5 rounds in 7 inches at 500 yards using a GripPod and bean bag for support. At 500, my ballistiplex runs out of hash marks.
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