Two distinctive groups on paper

[Michaël T]

Hello
today at the range I encountered a problem I have no clue how to fix it without burning up my barrel and bullet supply

I shot five round group and develop two distinctive groups one on top of another with three(3) shots together and the other two(2) together

can anyone please explain what happened and how to fix?

thanks,

Michael

 

[snert]

What rifle?

 

[Tim Singleton]

I'm guessing you are hand loading. I have no idea what caliber.
But for me and my rifle snake eyes means I'm to hot.

 

[chkunz]

You only have one group, keep shooting more rounds and you will fill in the gap. Problem solved. That sounds very sarcastic but with the limited information you provided that is about all anyone can do with analysis.

 

[Michaël T]

rifle is a 223 ar15 with 20" barrel
handloads too hot?

 

[Dusty Stevens]

What did the windflags do between those 2 groups?

 

[Michaël T]

7.00 pm est
absolutely calm zero wind

 

[TRG]

The easiest explanation would be a variance in cheek pressure. This is particularly true if you are using an eared rear bag. Rebuild how your gettting into the gun after each shot. Establish your NPA by moving the gun not by pushing it with your cheek. Be conscious of your cheek pressure on each shot and do not use cheek pressure to raise the elevation in establishing your POA. Fire ten round groups rather than five.

 

[SDWhirlwind]

Parallax? Seems too far apart for parallax but then if you aren't used to shooting an AR, aren't getting the same cheek weld, have a chitty scope and depending on scope height it could vary well be. But then I tain't the brightest bulb in the string!!

Maybe I should have asked.....did you shoot one point of impact then the other or shots went in one group or the other??

 

[Michaël T]

the shots were fired at the intersection of the black lines, same point of aim,
cheek weld is possible, but I have shot other handloads (77nosler) that show a well rounded group
these are nosler 80's
first shot was one the horizontal line shot 2/3 were above shot 4 went above shot 1 and 5 went into lowest of the top three

 

[TRG]

The change in performance between two loads is more than a clue. Have you shot both loads in the same session and observed that the 77gr. load has normal dispersal and the 80s show the verticals?

 

[Alex Wheeler]

Adjust your seating depth.

 

[LHSmith]

I'm guessing you are hand loading. I have no idea what caliber.
But for me and my rifle snake eyes means I'm to hot.

My vote also.

 

[Michaël T]

The change in performance between two loads is more than a clue. Have you shot both loads in the same session and observed that the 77gr. load has normal dispersal and the 80s show the verticals?

I had possibly one min in between shooting the 77 and 80's that was a total of 22shots

 

[snert]

I experienced this with a Handi-rifle....ya, after you stop laughing, hear me out.

It would double grioup. I thought it was the closing of the action. I discovered it was rest technique. I suspect you are having a similar isue with an AR platform. Those guns dont tend to "ride the bags" so well...

I honestly think that could be the issue, but if it isn't happening with other loads, then I vote "too hot".

 

[aussiepowderburner]

I had a barrel that did that and was not stable as it heated up.
Stress problem!
Although you have other loads exhibiting round groups so can't be hat?

 

[Mozella]

What barrel twist?

My 1:9 bolt gun shoots ordinary Hornady 75 s just fine but won't shoot Hornady 75 gr A-Max worth a damn; often showing results similar to yours. Heavier bullets of any kind are no good for this particular rifle.

Could it be you're right on the edge of having enough twist to stabilize the heavier bullets?

Perhaps the answer to your problem is simply "Shoot the slightly lighter bullets and be happy".

 

[Michaël T]

barrel is Krieger 7.7 twist
going to range in two hours to try reduced load.

the BR4's don't any sign of excessive pressure

 

[Dusty Stevens]

My 7.7 krieger loves the hornady 75bthp and not much else

 

[wapiti25]

You need to shoot more groups to see a trend. It may be the way the gun ride's the bag's as mentioned by others.