What caused a change in group size?

[Morgan321]

In the picture below. Left target is 2 weeks ago, right one is today. I didn't change anything.

I shot some of my "standardization" ammo, it was still under 1 moa with no change from previous performance(ie. tells me the gun hasn't changed). Conditions were same temp, same range, and very close barometric pressure. Both were at 100 Yds. Same press, same components loaded the same way, etc.

Ideas? I'm leaning towards the first one was a fluke because I have no explanation.

 

[M40_A1]

Everyone has off days. But,........

What was your cleaning regimen before each group shown? How many rounds were fired from the time you cleaned to the time you fired the groups shown? Was your shooting cadence the same? You say you didn't change any thing, yet your targets are not alike. That alone can make a difference, though probably not as much as we're seeing, but some.

 

[bjay]

With that vertical..my firs suspect would be temperature...but i too beleive we got those days where "shitty" outcome with same ammo even unclean barrel from last shooting..

 

[wvlapua]

If you cleaned between sessions, there may have been some residual solvent or oil in the chamber.

 

[Morgan321]

Didn't clean the barrel in between. I'm not a cleaner, I cleaned the barrel real good once and the gun shot poorly for the next 20-30 rounds so I rarely clean the barrel(factory 700 skinny barrel). The components were all from the same packages. Brass was prepped the same and even primed all at the same time.

On the second day the cold bore shot was the lower most shot, even neglecting that it got worse.
The "control" ammo performed slightly better than normal with two 5-shot groups tighter than usual, making me suspect the ammo rather than myself or the gun.

So I'm not wasting time and money on this node, the next lower node performed great. I had hoped to get the same performance at this higher node for better performance at long ranges, but apparently it is not to be.

 

[ptaylortx]

I have this problem with my 300 win R700 and RL22. It's .5 moa @85 deg and 1 moa @ 45 deg. I'm going to work up a load with H4831sc. Hodgdon is far less temp sensitive.

 

[09cs]

Could have been you just had an off day or your rifle needs to be cleaned.

 

[Engine 22]

Its difficult to say with seeing only 2 groups, but I'm going to say its you. Like stated before, we all have our "off days." Possibilities can include caffeine on board, (or lack there of ) hangover, flinching, stress, etc...
Share your next group, with all things the same, and let us see where it goes. Good luck.

 

[samnev]

My AIAW went form shooting 0.25 moa groups to 0.75 moa groups after I cleaned it at 200 rounds. Since you didn't clean your rifle I suspect either a change in wind conditions at the target compared to your shooting position. I always tie a piece of ribbon on my target to gauge the wind conditions there. 2nd you might not be getting on the stock in the same place which can cause the vertical stringing shown in your 2nd group. Or you just had a bad day.

 

[culater]

I think you answer your own question with (factory 700 skinny barrel). Also do you make sure your powder lot is all the same numbers when you buy it. Each lot will shoot different
from lot to lot. Try shooting 1 shot per min so your skinny barrel has time to cool. Try this out, have you rounds ready next to you and when you shoot, follow threw by staying on the rifle and load the next round and shoot an repeat.

 

[Drifter™]

Obviously, you shot two different styles of targets on different days.

Changing target styles and / or colors can change the way a shooter sees the target, thus affecting POI and / or group size. (If you don't believe this, put up two different targets side by side, then shoot and observe the results.) Lighting (sunny vs overcast) can also be a factor.

 

[40xs]

It appears that your "zero" hasn't changed, only your grouping. I would suggest checking all the points on your firing technique, etc.

 

[427Cobra]

WTF, 48.8 of IMR4895 pushing a 175

 

[mb3]

In the picture below. Left target is 2 weeks ago, right one is today. I didn't change anything.

I shot some of my "standardization" ammo, it was still under 1 moa with no change from previous performance(ie. tells me the gun hasn't changed). Conditions were same temp, same range, and very close barometric pressure. Both were at 100 Yds. Same press, same components loaded the same way, etc.

Ideas? I'm leaning towards the first one was a fluke because I have no explanation.

Tough to say without more detailed inspection but, that is a big change for 100 yards- without anything changing in your weapon or ammo. Normally when I see a group size change like that in a previously consistent rifle I start with checking the setup. I usually find the culprit to be the action screws, and as a general rule I check the torque once a quarter.

 

[Morgan321]

I appreciate the input, here are two other loads I shot at the same time as the bad group above. These two loads shoot like this all the time and are very consistent.

In other words, the rifle and myself were operating normally. Not sure what was going on but I'm going to fine tune the 46.4 load and stick with it for now.

 

[maggitas]

got a few questions.

1. Are you experiencing any "Sticky" bolt issues?
2. What length are you loading the 175 Gr ammo to
3. What primers are you using.

 

[Morgan321]

About 1 in 20 cases are difficult to close the bolt. I neck sized only, 1 full length size and the hard to chamber cases are smooth as silk. No bolt lift issues.

The 168 Amax rounds I made 3.26 and the 175 smk are 3.33.

Primers are fed LR in the Amax rounds and Fed LR magnum in the smk rounds.

 

[AIdog]

Check ur runout...

 

[maggitas]

I was thinking you may be loading into the lands and you may be getting some pressure spike. do you know your seating depth on the rifle? You could have a bad batch of primers as well. If none of these solves your problem then I would have to say you need to check the runout of your brass.

 

[Morgan321]

The ammo was all loaded the same, no change in oal. Primers were from the same box. Brass is all from the same lot and even the same physical case.

 

[AIdog]

One thing about shooting is that there are no flukes things happen for a reason usually to teach u something you didn't know before... something is wrong with either your ammunition, rifle, or your technique. Seems that u have ruled out that your technique is not at error so that leaves your rifle or the ammo. Clean your rifle, torque action screws, throat erosion, etc. As for your "hard to chamber" rounds I believe runout (bullet/case) is the culprit. Next time a hard to chamber round is identified extract it and see what might be causing it to not chamber smooth. There will be scrapes somewhere on the round. Another thought is u might have to find another load that is acceptable for you.

 

[jbailey]

WTF, 48.8 of IMR4895 pushing a 175

Assume this is for a 30-06 (would be way hot for a 308 )

OP - this is 5 rounds... maybe you pulled the 2 that impacted low for whatever reason. Don't sweat this too much. Try another 10 rds and if it still shots like sh*t, start to worry. Don't get stressed out

 

[DamnDave]

Everyone has bad days at the range.

 

[Benchguy57]

I'm thinking that it's a very good chance it's operator error.
As we have all had bad days on the range, plus the different target makes for a different view as well through your scope.
Did you use the same magnification both times?
If I were you I would give it one more try and if you have similar results, scrap the load.
Just my .02

Good luck to you.




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