Same handload different grouping issue

[farmboykjb5.9]

Hi all, just wondering if anybody would know what would cause a new gun to shoot 1/2"-5/8" group then ten minuets later load the same handload and shoot again and it jumps out to 1.5"- 1.75 group? I have 3 different guns that are doing this which includes
Rock River predator hp 308,
My own built 6.5 Grendel (not cheap built either),
And a Ruger M77 Hawkeye predator in 6.5 creedmore which is making me the maddest cause my brother has the same exact gun and his shoots any handload good and mine is temperamental.
Scope mounts are torqued to spec, rings are lapped and torqued to spec,
there's no stock to barrel contact.
A box of factory were used in each gun for break in before starting to handload. Any help would be greatly appreciated, thanks

 

[elf]

If 3 different guns do the same thing, I would not blame the firearms or ammo. I think you should check your rest, shooting table, and maybe your shooting position, etc.

 

[Deputy819]

How did the rifle (s) group with factory ammo during the break-in?
Are you using brand new brass or once fired brass now that you're handloading for them? The rifle (s) will shoot differently if the changes in brass (new vs fired) aren't accounted for.

 

[farmboykjb5.9]

Definitely not the shooting rest, the 308 I thought maybe the brass too cause I got it from one of the local police departments which all shoot Remington bolt guns so I can understand that but the creedmore and Grendel are new brass and the creedmore shoots factory about 1.25" consistently and the Grendel shoots 7/8" consistently with factory.

 

[Hatrick]

Let someone else shoot it.

 

[farmboykjb5.9]

All ready have, I could see if i was one of the wanna be shooters that just started shooting but I've been shooting for 26 years and handloading since I was 13 years old.

 

[Hatrick]

Please don't be mad. I took it from your post that the primers, brass,powder, bullets, barrel temperature, barrel fouled or clean, outside temperature, elevation, and shooting site were the same. It is happening in three of your rifles. The only common denominator is the person pressing the trigger. Tom

 

[farmboykjb5.9]

Yes everything is the same, I have a shooting range at my house so I can load and shoot all day long if I want. I have close to 50 rifles so these 3 just keep getting pushed a side cause I'm fed up with them, they might leave but I love the creedmore for being a factory rifle.

 

[Rhett Crider]

Since these are all new rifles and it sounds like you've already put a few rounds through them, it could be your barrels speeding up since they're breaking in. And if they are sporter contours. Need to chrono your shots and possibly redevelope your load for each one.

 

[farmboykjb5.9]

I agree with that, but my Grendel for instance I shot a box of factory then loaded 3 different handloads, the first load shot 3/4" group, the second shot 5/8" group and the 3rd shot about 1.5" so i loaded the load that shot good up again and it jumped to 1.5". Tried it again and same thing. I have numerous loads that will shoot 7/8" group but can't get it any tighter. The factory were 123 sst and my handloads are with the sst

 

[jasent]

Has this happened on multiple outings? Could just be shooter fatigue

 

[Rhett Crider]

Clean your barrels real good and chrono your loads. Still sounds like your losing your node. I like the original Magneto Speed chrono. It doesn't seem to loosen w/ recoil like the MS-V3.

 

[User4302021]

Yes everything is the same, I have a shooting range at my house so I can load and shoot all day long if I want. I have close to 50 rifles so these 3 just keep getting pushed a side cause I'm fed up with them, they might leave but I love the creedmore for being a factory rifle.

I'll bet you are a pretty good shooter, and I'll take your word you are a competent handloader.

The only other thing all these rifles share is environmental conditions. Changing light and mirage can make a group go from 0.5MOA to 1.5MOA. And it can happen very quickly, I've seen it on more than one occasion. The air suddenly reaches a temp that increases mirage dramatically, the sun comes out from behind a cloud...it goes on.

The only way to eliminate this as a possible factor is to shoot them in heavy overcast or as early as possible in the morning. That will tell the tale.

 

[farmboykjb5.9]

Has this happened on multiple outings? Could just be shooter fatigue

No definitely not, a couple of the guns I've been messing with here and there for a couple years now