AR15 "jump"

[GetReal]

Got a 14.5 P&W 5.56 I want sub MOA accuracy from. When I measure the lands, I get 0.150" jump.

In a 6 ARC (also semi) I'm within 10/1000 of the lands.

I know I can't get near the lands and fit an AR mag in the 5.56 so I'm wondering....

How many get a special AR15 223 / 5.56 barrel spun to be a short jump (under 0.060) to the lands?

(Forgive me, I occasionaly like to shoot gas guns.)

 

[Walt Krafft]

Sierra 77s are very jump tolerant.

 

[M-61]

Got a 14.5 P&W 5.56 I want sub MOA accuracy from. When I measure the lands, I get 0.150" jump.

In a 6 ARC (also semi) I'm within 10/1000 of the lands.

I know I can't get near the lands and fit an AR mag in the 5.56 so I'm wondering....

How many get a special AR15 223 / 5.56 barrel spun to be a short jump (under 0.060) to the lands?

(Forgive me, I occasionaly like to shoot gas guns.)

 

[M-61]

Do you mean freebore?

 

[Gargoyle]

If you are restricted by mag length loading, just forget the DTL/Freebore/jump. Tweak by powder charge, and if you are really serious...square the receiver face and bed the extension with blue loctite or have a cerakoted upper receiver. You want a fit that takes a rubber mallet to seat the barrel extension into the receiver.

Other things are increase buffer weight, add bleed off gas block to smooth out the recoil impulse.

 

[Dusty Stevens]

SBR rifles are hard to group good. Made for kicking in doors.

 

[280ai]

Jump of .060 no big deal (less bbl wear) load 77 gr and have fun my 556 ar (20 inch match 1-8 twist loves 77s)

 

[granite1]

Check out Compass Lake Engineering. They have a chamber offering they call the Compass Lake match. It’s supposed to have a shorter throat than others.

 

[Gargoyle]

SBR rifles are hard to group good. Made for kicking in doors.

Quit being a realist! LOL Just trying to answer the man's question without being a Debbie Downer!

 

[joshb]

Walt nailed it with the Sierra 77. I’ve found the 69 pretty tolerant, too.

 

[WindSurgeon]

I've shot 80 grain in an AR for fclass (single load). The bullets were always better when seated touching the lands (not jammed). If shooting with magazine, that will be your limiting factor.

 

[WildBill3/75]

Walt nailed it with the Sierra 77. I’ve found the 69 pretty tolerant, too.

This.

 

[GetReal]

Walt nailed it with the Sierra 77. I’ve found the 69 pretty tolerant, too.

Using 69 SMK's.

 

[Dave M.]

Quit being a realist! LOL Just trying to answer the man's question without being a Debbie Downer!

Sometimes you gotta tell people the way it is though. Expecting to get sub MOA accuracy consistently from a SBR AR is NOT being very realistic.
Dave

 

[joshb]

Sometimes you gotta tell people the way it is though. Expecting to get sub MOA accuracy consistently from a SBR AR is NOT being very realistic.
Dave

Well.......I have an AR pistol with a 7.5” barrel and a brace that I wanted to shoot under 1” and I figured out how to do it!!
Just use a good front rest, rear bag and place the target at 10 feet. Voila! 3/4” group!

 

[Dave M.]

Well.......I have an AR pistol with a 7.5” barrel and a brace that I wanted to shoot under 1” and I figured out how to do it!!
Just use a good front rest, rear bag and place the target at 10 feet. Voila! 3/4” group!

Lol. I should have clarified “accurately at what distance”….haha.

 

[joshb]

Lol. I should have clarified “accurately at what distance”….haha.

Ok! Same set up at 50 yards with factory PMC ammo gave me a 3 1/2”-4” group.

 

[Clous]

69’s and Varget give me 1/2 MOA in a 16” barrel.

 

[gpoldblue]

Got a 14.5 P&W 5.56 I want sub MOA accuracy from. When I measure the lands, I get 0.150" jump.

In a 6 ARC (also semi) I'm within 10/1000 of the lands.

I know I can't get near the lands and fit an AR mag in the 5.56 so I'm wondering....

How many get a special AR15 223 / 5.56 barrel spun to be a short jump (under 0.060) to the lands?

(Forgive me, I occasionaly like to shoot gas guns.)

Cut the front of your magazine with a Moto-Dremel tool and you can pick up about .020"-.030".......I did.
Be safe....good shooting.

 

[karrarararararar]

I think most of your mag length match bullets are going to be jump tolerant at mag length. As many have stated, 77's and 69's work well. Not a short barrel, but 53gr V-max's are about ¾ moa out of my factory 18" ruger.