Analyzing progressively worse groups

[Zell959 40]

I headed to Cherry Ridge on Sat morning with the specific goal of shooting 4 comparably good 5 shot groups to kind of prove to myself that I hadn't simply cherry picked the handful of good groups I've taped up over my reloading bench. That isn't exactly what I ended up doing, and I'd be interested in anyone's feedback or thoughts on what I should take away from the results. Range is 100yds and I was benchrest shooting my BCM 16" SS barrel AR w/Trijicon TR24. Ammo was all from the same batch of 77gr reloads I made at the same time & used the same lot of spent brass for.

 

 

 

I shot the plates top to bottom, right to left. I.E., the first two groups started off pretty good, but the next two were noticably worse. I don't believe it was my barrel getting hot, as it was a relatively brisk 37 degrees and I was taking 5-10 seconds a shot and around 3 minutes in between strings. I also don't feel like I was doing much differently in each string. None of the groups felt less comfortable than another. Overall placement on the plate also doesn't really change, so I don't feel like I can blame wind or anything like that.

 

Yet, it would seem that something changed. It's not as if the larger groups are just being thrown open by a single flyer.

 

My only other thought would be that nothing really went wrong and I just need to think of all 4 groups as 'valid' indicators of the accuracy my rifle & reloads are capable of, which would be a little dissapointing as the bottom right's extreme spread was over 2".

[Pew Pew Plates 358]

Combo of changing firearm temp, eye fatigue, you getting cold, etc. 5-10 seconds between shots is nothing. When I want the maximum from my 700 I wait 2 minutes between each round and 10 minutes min inbetween groups if I want to be consistant. Also you dont have a clearly defined aiming point which makes your eye fatigue even more likely. Depending on your sighting arrangement, aim small miss small. Those plates are massive targets. At 100 yards I shoot 1" diamonds which are great because you can ensure you rifle isnt canted by checking to see that each crosshair goes over a point of the diamond.

[Vlad G 345]

1) Is you barrel free floated?

2) Is it really?

3) What are you using as a rest (bags, bipod?)

[Ronald Silver 2]

That is pretty bad.

I personally would've just gone with plain paper plates instead of that horrific pattern...

[lunker 274]

Is it possible your load changed as you loaded it (i.e. more/less powder, seating depth, crimp, etc). Next time, to randomize the ammo factor, pull from different spot in the ammo box, or mix up the ammo first. Just a thought if all else fails.

[Pizza Bob 1,488]

I think that glennp and Vlad G both have credible reasons. The ones I find most likely are Glenn's fatigue and aiming point reasons and Vlad's free float and shooting rest reasons.

 

Glann's are self explanatory, but Vlad's may bear some comment. If the barrel is not free floated, as it heats up the degree of interference at the pressure (contact) point changes as does your POI. As for the rest - shooting with a bipod can be tricky. For absolute best accuracy the bipod has to be "loaded" the same for each shot. Different loadings of the bipod can cause different barrel harmonics that can change the POI. Situation is exacerbated if the barrel not free floated.

 

To "load" the bipod, I pull the stock into my shoulder and then apply slight forward pressure to preload the bipod. You try to do it exactly the same for each shot. Better accuracy will be had shooting over a bench rest with sand bags.

 

Good luck.

 

Adios,

 

Pizza Bob

[Zell959 40]

Appreciate the feedback all.

 

Eye fatigue may be part of it. I'm gonna see if I can come up with something with a high contrast point of aim that might make things easier on subsequent attempts.

 

On Vlad G's questions

1 & 2 - Yes. I'm using this upper from BCM

 

3 - It was the front bag of the Caldwell Deadshot shooting bag combo.

[Vlad G 345]

Make sure there is no contact between the gas block and the hand guard, sometime clearance is not what that great.

[vortex0178 3]

Maybe try a better rest? I usually go Sat mornings but I'm on the pistol range; if you'd like, you can borrow my Rock rest and Protektor bags. PM me if you wanna give it a try.

[JimmyAGR 54]

I have a lead sled rest that I would be happy to loan you, then you can tell if it your rifle or the shooter.

[Pew Pew Plates 358]

A little pro-tip, if you are firing with a bipod off a bench pop some pill bottle caps under the feet so they dont grab on anything and they slide the same under recoil, every time.

[Zell959 40]

Appreciate the comments guys. The feedback was helpful. I'm gonna look to put together a fresh batch of 20 reloads, try to find a target with more contrast that will mesh well with my reticle and give it another go relatively soon. I'll also increase the time inbetween shots & strings, per glennp's thoughts.

 

Maybe try a better rest? I usually go Sat mornings but I'm on the pistol range; if you'd like, you can borrow my Rock rest and Protektor bags. PM me if you wanna give it a try.

I have a lead sled rest that I would be happy to loan you, then you can tell if it your rifle or the shooter.

 

Thank you. I'll likely end up taking one or both of you up on the offers, once I get everything together.

[KpdPipes 388]

Appreciate the comments guys. The feedback was helpful. I'm gonna look to put together a fresh batch of 20 reloads, try to find a target with more contrast that will mesh well with my reticle and give it another go relatively soon. I'll also increase the time inbetween shots & strings, per glennp's thoughts.

 

 

 

 

Thank you. I'll likely end up taking one or both of you up on the offers, once I get everything together.

One other thing, is to take some more time.. Shoot your first 5 round group, then Open the rifle up, take the BCG out, and let it cool completely, then shoot another.. the way they opened up it looks like barrel heating, probably coupled with one or two other issues.