Rifle Changes Favorite Ammo

[crkckr]

While it might be improbable on 2 rifles at the same time, I would suggest you check both your bases and rings for security. When I mount a scope now I use red locktite, especially on something like my .338 WM. I had the exact same thing happen and it turned out to be loose bases.

Of course, reviewing your shooting hold should be done, too. Draping yourself over the rifle and holding things down nice and tight one time while essentially free recoiling the next can also give similar results. Big humidity jumps can do it too, so check bedding & stock screw torque. Just make sure you do just one thing at a time or you may find it fixed but not know exactly how or why!
Cheers,
crkckr

 

[johnrmorgan]

I had an issue with a rifle not grouping with proven loads and finally narrowed it down to not setting my parallax after a previous data collection sessio.

 

[Frog4aday]

<SNIPPED STUFF> You mentioned wind. Depending on which bullets, wind can have a big effect on bullet flight and POI, even at 200 yards. <SNIPPED STUFF>

I agree with Mr. Kenyon - most logical issue is WIND. It is the devil. Especially if the gun shoots good this trip, bad next time, then good again. It is either YOU or it is the WIND. Scope bases or rings coming loose wouldn't be 'good' again next trip to the range. But that wind...she is a tricky lass. She'll mess with your mind...and bullets pretty effectively at times.

 

[Dirtrax]

Good days, bad days, windy days. You can have either on windy days if you know how they effect your shooting. What do you mean by "all over the target"?

 

[Wolf76]

Do you clean your guns between sessions?

 

[Kansaswoodguy]

I'd say cleaning is the culprit I don't clean the bores very often and never before a hunting trip I need to know where that bullet is going this is particularly important with many factory barrels stripping the copper can cause accuracy issues. I have a older AR-15 that can regularly shoot 3/4 to 1 moa the last time I cleaned it took very nearly 40 rounds to foul the barrel before it would start shooting tight groups again this gun is a little of an exstream but you get the idea cleaning is not always a good thing.

 

[FEENIX]

Shooter?
Rifle position?
You mentioned wind. Depending on which bullets, wind can have a big effect on bullet flight and POI, even at 200 yards.
You also mentioned temperature changes. Powder can be temp sensitive. Meaning velocity changes which could be pushing out of an accuracy node with barrel harmonics.
As for rifle.cleaning, if it shoots good one week, then poor the next, then back to good, I would not say it is barrel cleaning. Unless you cleaned in the middle. I don't clean until my groups start to open up. Anywhere from 60 to 600 rounds depending on the rifle/powder/bullet combo.

Agreed! The "NUT" behind the trigger remains the biggest factor.

 

[FEENIX]

I should have stated, I use off the shelf ammo. Once I find what my gun likes, I'll buy 15 boxes.

Factory ammo with different lot # can make a huge difference. Below are pictures of two groupings at 200 yards shot out of 6.5 CM using Winchester 125g deer season XP ...

(3-shot group at 200 yards)

(5-shot group at 200 yards)

 

[bigtuna431]

So what happened on the 4th..5th.. trip to the range?? If you're still good, mark it up to just having a bad day....

 

[DartonJager]

I am by profession a maintenance electrician that fixes electrical and often mechanical equipment in emergency brake down situations under very high stress time compressed conditions.

I often encounter equipment that was previously running perfectly that suddenly for reasons unknown stops working. AS a matter of absolute must I keep myself informed of when ever ANYONE does any work on any equipment I am responsible for.

I can not tell you how many times after I read the maintenance logs for a given piece of equipment that detail someone has changed or fixed a malfunctioning electrical component and shortly there after that same piece of equipment stops working unless I am certain of the cause I will instantly check the component that was replaced or worked on and FAR more often than not it is the cause for the break down.

My point being if your rifle was shooting great then shoots poorly then once again returns to the same level of accuracy as before and you are still using the same optics and ammo (lot #) then the only external factor left that can affect accuracy to the degree you experienced is you the shooter or some other external factor other than the rifle, optics or ammo.

 

[Frog4aday]

Are your guns sitting in wood stocks? If so, i think this was good insight:

<SNIPPED STUFF> Big humidity jumps can do it too...Cheers, crkckr

So far my favorite theories are wind, humidity, firing different lot #s of ammo, and the operator just having an "off" day.

If you figure it out, come back & let us know what it was. Then we all learn something.