Most common cause: groups opening up?

[AmmoHound]

Not sure if this is a truly dumb question, or only semi-dumb, but here goes.

I have a new Remington 700 Police in 308. I tried some handloads using 168 gr SMKs over IMR-4895, seated 0.010 short of the lands. The first couple of 4-shot groups were fantastic (for me anyway), at 100 yards about .45 inch and .8 inch. But after that, they really opened up, to maybe 1.75" or so.

Those of you with experience, what do you think would be the most likely reason for this? I have some options below, but it may be something else of course.

* barrel not allowed to cool between shots?
* barrel not cleaned between shots?
* handloads have variation in xyz ?
* scope rings or mounts not tight enough, and scope is moving ?
* operator error, just coincidence that all later groups were sloppy?
* I just got lucky on the first two groups?

A bit more info: my handloads were all made using Lake City brass, but not from the same lot; I didn't turn the necks, sort by weight, etc. However each charge was hand-weighed to 0.1 grain. Also I shot some factory 168gr Federal GMM after the good groups, and that didn't group well either. There was zero wind on the day this occurred.

I'm especially interested in opinions from any of you who have actually had this happen, and how you fixed it.


Thanks!

 

[bschneiderheinze]

Clean it

 

[ShtrRdy]

Was the ammo sitting in the sun?

 

[1moaoff]

Is it brand new?
How many rounds on it?
Did you change position?
Was that a normal number of rounds for YOU to shoot?
Do you have rifles that you typically shoot better?

If that was "good for you" meaning not normal" maybe you got lucky and had good form or just good luck at that time. Shooting consistently is not as easy as most people really think. That's why people get excited when things fall just right ut then get frustrated when they dont. The rifle is often less variable than the shooter and ammo.

 

[1moaoff]

That wasnt meant to sound bad. I was trying to be clear.

 

[1moaoff]

The short a.swer is experience and asking questions and learning from others, mostly its finding what works through trial and error

 

[AmmoHound]

Thanks guys.
@ShtrRdy: No, the ammo was in the shade.
@1moaoff: It was only the second range session for the rifle, so essentially brand new. I used the same position (seated from the bench with front and rear rests) throughout. I shot a little under 1 moa with a 270 Winchester the same day, and can do that fairly often with a .22 I own. I don't normally get close to or under 0.5, but then again, this is the most inherently accurate rifle I've owned.

Referring to the advice of @bschneiderheinze ... do the rest of you normally clean the barrel after every shot or group? That seems a bit extreme, but if that's what it takes, I'll give it a try.

 

[bschneiderheinze]

You didn’t specify how long it had been since you cleaned it. Honestly I don’t follow normal break in procedures I shoot 25 rounds on a new barrel and then clean. After that I clean every 500-600 rounds or if it’s convenient in between like 400 rounds if I have time. I have read to many articles saying that overcleaning leads to barrel premature barrel failure. I also only use patches. Both of my 6brs in the 1000-1200 round count shoot in the .3 easy.

 

[ShtrRdy]

What I was wondering is if the ammo was at a different temperature from the "good" group to the "bad" group?

 

[theLBC]

i dunno but i don't think you should have to clean your barrel after 8 shots.
nor do i expect barrel overheating after 2 groups.
that leaves your other choices.

 

[phantomskittles]

Usually first thing I hear recommended and that I agree with is find an experienced shooter to try it to see if the same issue occurs. If it happens with them that rules you out as the cause. The next I do is check torques on everything to make sure nothing is moving that shouldn't. Once those are out of the way you can start worrying about other potential causes.

 

[Stooxie]

Shooter fatigue can set in very quickly and it sneaks up on you. I'm going to say that this affects many "regular guy" shooters, myself included. Obviously pros and those with lots of experience either don't have the problem or practiced enough to overcome it. It can be a combination of flinching, muscle fatigue, shaking and just general impatience or overconfidence.

It took me years to understand this. Finally I can get some damn good groups but I've learned to recognize when my precision shooting abilities are done for the day!

Mindfulness is very useful.

-Stooxie

 

[acudaowner]

the only thing I can say about my not shooting the groups I thought I should shoot is , I did something wrong my cheap ammo did not cause the group to open up , My scope did not do anything It should not have done . I did something or I forgot to do something and It's all my fault and so far that has been the case 98% of my mistakes that and over thinking the shot so far I am really good at that . Just as correcting those mistakes is my job . Shame knowing it still does not keep me from getting mad about the bench being not level or the table top not lying flat , and darn that giant fly that picked my scope to sit on at the minute I am squeezing the trigger . and the wobbly seat .

 

[AmmoHound]

Thanks everyone, this helps. At least I don't have to worry about an obsessive cleaning regimen during a session. I guess I'll focus on my form, and keep the ammo as good as I can make it.

 

[LawnMM]

Barrel may be breaking in, might have to retune your load

 

[RRG]

Check the action screw, maybe it worked loose. It happened to me once.

 

[Cerwinski]

For me the primary cause is getting fatigued. That's why I limit my sessions to 40 rounds or so. Whether you realize it or not shooting a rifle for precision is hard work. Both physically and mentally.

 

[Alan101]

If you can, have a better shooter than yourself try it out. If they have similarly inconsistent groups then its equipment/ammo related. If they have consistent group sizes then it is you. For myself, I usually find that I am problem. Unfortunately

 

[pbatesaz]

From an equipment standpoint, check the action screws, scope mount, parallax adjustment, any muzzle device that may be attached, and if a switch barrel rifle, check that. From a shooter standpoint, fatigue, trigger control and recoil management are the things I would consider. Let us know what you figure out.

 

[308pirate]

I bet your barrel is rougher than a cob in the throat and fouls with copper like crazy.

I would clean the shit out of it with an aggressive copper remover then send a full kit of Tubb Final Finish down through it before using it again.

 

[jego]

How many rounds have been put down the barrel? Is it broke-in? Do what you think is best for barrel break-in procedures.

How did the groups open up? Vertical? If so, perhaps temperature of the rounds, but I have my doubts.

I keep a thermometer (key chain style) on the zipper of my ammo bag, temperatures are recorded in the log book.

I would check the torque of all the components. I wouldn't change anything else until I proved I wasn't the cause. Take her for another spin, concentrate on the fundamentals, keep a good log book. In doing so, if it happens again, you will have more clues as to the cause.

 

[antithesis]

Time to get the torque wrench out. Maybe even a little Loctite.