ordering a barrel... I'm confused guys!

[Skullboy]

They found a significant advantage to a 6 groove, 1:10 twist bbl for shooting M118LR (I believe this is lake city 173gn). I

M118LR uses a Sierra 175 gr. HPBT Matchling bullet.The 173 gr. FMJBT was used in the Original M118 match ammo and hasn't been used since.

A 6 groove barrel is better for the thin jacketed "Match" bullets.This is the route to go for the best overall accuracy.

A 4 Groove barrel is better suited to thicker jacketed FMJ type bullets.However the thinner jacketed match bullets can shoot pretty darn good out of these barrel.......... This is the route to go for a Service "match" Rifle using issue type ammo, or if you want to shoot surplus ammo.

Basically, shooting the thicker jacketed bullets in a 6 groove barrel will cause the barrel to copper foul and "clog" the grooves/lands.

I learned this info from experience with M14 match rifles and from my M14 Sensai Hungry.

SKBY.

 

[roberti11]

M118LR uses a Sierra 175 gr. HPBT Matchling bullet.The 173 gr. FMJBT was used in the Original M118 match ammo and hasn't been used since.

A 6 groove barrel is better for the thin jacketed "Match" bullets.This is the route to go for the best overall accuracy.

A 4 Groove barrel is better suited to thicker jacketed FMJ type bullets.However the thinner jacketed match bullets can shoot pretty darn good out of these barrel.......... This is the route to go for a Service "match" Rifle using issue type ammo, or if you want to shoot surplus ammo.

Basically, shooting the thicker jacketed bullets in a 6 groove barrel will cause the barrel to copper foul and "clog" the grooves/lands.

I learned this info from experience with M14 match rifles and from my M14 Sensai Hungry.

SKBY.

Thanks, I wrote from memory, I re-read the article last nite, they were using black hills 175gn.

It is a 18.5 inch bbl and they compared it to the M24 5 groove 1:11.25 twist bbl, and the M40A3 1:12 twist. With a 18.5 inch bbl the 1:10 6 groove Hart bbl had a clear superiority, they claimed that it could be accurate to 1000 yards (I know, 20 inch bbl???).

Nonetheless, the Defence advance research project agency (DARPA), was impressed enough that this rifle was accelerated into use, and now serves in the front line. I am not sure if the bbl was a standard 26 inches if the 6 groove bbl would still stand out as much. I also cannot tell from reading if the real magic was the 1:10 twist, or the 6 grooves, or both?

 

[Mystic Precision]

Me thinks the real magic is the HART barrel no matter the configuration.

True BR quality barrels shoot very well. There is all sorts of talk about twist and groove configurations. The quality of manf matters much more then the rifling specs.

The furthest I have seen accurate fire with a 175grMK load is just under 1400yds. Bullet fell apart beyond 1400yds.

Jerry

 

[roberti11]

Xm3

Me thinks the real magic is the HART barrel no matter the configuration.

True BR quality barrels shoot very well. There is all sorts of talk about twist and groove configurations. The quality of manf matters much more then the rifling specs.

The furthest I have seen accurate fire with a 175grMK load is just under 1400yds. Bullet fell apart beyond 1400yds.

Jerry

I did not realize they put the article in the public domain.

Here it is for those who want to read it:

http://www.precisionshooting.com/psm_2007_11_frame.html

 

[Mystic Precision]

Read the article focusing on the ballistics claims.

Barrels with a slow twist failing at 600yds if shortened...?????? Bullets tumbling? Poor Accuracy? What?

Shorterning a barrel certainly has an effect on muzzle velocity. From 26" to 18.5", you will see up to 200fps difference. Going from 2700fps to 2500fps really make the bullet fall apart at 600yds?

So at 2700fps, you can go beyond 1300yds. But at 2400/2500fps, you can't go much past 600yds? Something doesn't quite add up.

Was a nice ad for the makers of this rifle though. A little bit hollywood.

Did like the fact that they promoted the lighter rifle 13lbs vs 18ish lbs. Fact that it should be more like 10lbs is moot.

As always, YMMV,

Jerry

 

[Leeper]

Isn't that a well researched and unbiased article though! I'm surprised Precision Shooting would print such drivel unless it was a paid advertisement. Was it a paid for ad?
Anyone with a significant amount of experience in accuracy matters is not too inclined to trumpet the virtues of any particular rifling form over all others. It appears that 6 groove barrels with lands about 1/2 the width of the grooves will provide about all the accuracy we can get out of a barrel. It also appears that this level of accuracy can be matched with about any other number and configuration of lands and grooves, within reason. When a given configuration is capable of providing accuracy of under 1/10 MOA (assuming the use of bullets capable of doing this), it's not likely any other configuration is going to be demonstrably superior.
At long range, bullets have to be spun fast enough to remain stable. I've seen no evidence that a twist of more than 12" is necessary for this with 175 grain bullets. This "artcle" is not evidence. Regards, Bill.