POA / POI change, barrel heated?

[valise]

Gathering my thoughts and pics here to see if I understand this correctly.

I seem to be ok at 25y.
I seem to be ok at 50y
But at 100y I’m all over,

My question is the variable at 100y barrel heat and / or proper shooting (bipod) technique? The ‘evidence’ is as follows:

Ruger 77/17 hm2, 20’’ factory barrel
USO 1.8x10, JNG MOA reticle, with EREK knob and US#3 windage
Atlas bipod.

The following targets were shooting from a bench. The scope and bipod are new to me. Previously was shooting the rifle in a scout set up with a another barrel so no comparison to be made there.

Had previously gone out with the scope and sighted it in but was having some trouble getting the reticle low enough [SH http://www.snipershide.com/forum/ubbthre...351#Post2576351 ] and now have a suspicion, or question based on today’s experience.

Sh.1 Pic

25 yard, sighter in lower left. POA is red dot, hit 1’’ low at 25y, which is consistent with where I left off from the last sighting. Ran a group placing POA at two hashes low (raising reticle, 2 hashes or 2 moa) and make a dandy little group.



Sh.2 pic

Move to 50y. Shoot group in center as POA=POI. Looked a little left and high. Moved to upper left dot as POA to play adjustments for a 50y Zero, went wrong direction, corrected by adj3. Moved to upper right dot as POA, still a little left and high. Moved to lower left, slowed down a bit and satisfied with 50y shot group as ‘Zero.’



Sh.3 pic

Moved to 100y with no further adjustments to scope. Now hitting what looks like 1-2 inches high. WHY is the rifle shooting higher at 100y than at 50y? Barrel heating up???

Moving to lower left dot, I play around and use one reticle hash high POA at red dot and group. Alright, but not great.



Sh.4 pic

I’m trying to learn something so I can apply it to bunny hunting in the field – so I move the target back in to 50y.

Started at upper right, it’s 1 inch high at 50. Looking back, it’s not much different than in Sh.2, but I really want to understand where this is hitting at different ranges, AND hit POA as POI.

Move to lower right dot. Adjust EREK knob to for better POA / POI and shoot lower right dot – very satisfied. Move to lower left dod, confirm POA/POI, reasonably satisfied.

Move same target to 25y so I understand distance change to POA / POI.
Shot upper left dot, it’s just a little bit low but I can live with that variable in the field (but it looks 1 to 1.5 hash / MOA low in the scope).

Next run it back out to 100y without changing anything on the scope…and use a larger target, and here’s where my QUESTION starts to come into play.



Sh.5

Shot center dot as POA…
I’m hitting 1 to 2 inches low which seems about right for 17hm2 drop…BUT RISES to POA/POI as I progress through the 10 shot string. Barrel cooled during change over and warmed up during string shoot???

Shot upper right dot as POA and hits moved higher yet, 1 to 2 inches high. (This connects back to my original problem with sighting in the scope hitting 4 inches high at 100 yards).

Move to lower right dot as using 1 MOA reticle hash high (lower scope) and it goes low…I’m confused now. Move to lower left dot as POA and it does still hit 1 inch high….and wrap it up feeling like I don’t really know what I’m doing.

So my question as stated at the beginning…is the variable at 100y barrel heat, and / or proper shooting (bipod) technique? For a hunting rifle do a 'cold zero' instead of a warmed target zero?

 

[thickstrings]

Re: POA / POI change, barrel heated?

Just my opinion, but, technique seems to show at longer distances...Try without the pod on a decent rest with a rear bag. Try the same dope from your 50yrd. groups...They should all group at 100 yrds., just in a different spot, barring wind as a factor..which would give side to side differences.I don't think heat is a factor, as it would probably show up at 50yrds as well.

 

[valise]

Re: POA / POI change, barrel heated?

I'm sure most of this is me, either in technique or shooting too fast (+heat as the barrel is warm to the touch) but appreciate the replies so that I keep an eye out for anything else that needs to be considered.

To the points raised:

I was probably shooting as fast as 30 rounds in 10 minutes, then the range calls cease fire at 15 minutes for targets - so I'm probably going a little faster than a "properly executing" pace. I'll try this change of pace first.

This is a newish barrel with only ~200 rounds. Since I haven't cleaned it at all, I'm not over cleaning. Since it shoots nicely in closer but shows problems out farther I wasn't suspecting fouling but it's coming on time to swab it once.

For ammo I bought several cases of 17hm2 when I got the rifle and at least stick to a single batch & maker during a session. I have found that most 17hm2 is pretty consistent.

The USO parallax setting goes down to 30y (and visually feels focused) and seems to track properly. Being new to this, I like to overcorrect to really see the adjustment working until I understand it better, then can refine with smaller corrections.

I'll start with slow shooting, say 5 round groups, that will hopefully result in similiar locations to the established target ranges - this would address heat (and some technique). If I still have a problem I'll borrow a good rifle rest and try again, at a slow pace - this would address technique.

If I understand correctly!

 

[Dylan in AZ]

Re: POA / POI change, barrel heated?

Valise,

I see you are here in Arizona! And from the range proceedures you describe I assume you shoot at the Rio Salado Shooting range?

Anyways, a few things come to mind all of which may not be the problem but are worth looking into:

Is the barrel truly free floated? Meaning, can you slide a piece of paper from the muzzle all the way back to the action without getting any binding or stopping. If the barrel isn't free floated then you may have a pressure point built into the stock that applies a different type of pressure unto the barrel with small changes/imperfections in form that can be associated with a bi-pod. This may not be an issue but I would suggest shooting it off of a front and rear shooting rest to eliminate shooters error as much as you can. This may tell you if it is the indian or his arrow. And as I'm sure you knew, don't bother with the rests provided at the shooting range (if I was correct in where you shoot at) because they usually aren't stable and will yield less than ideal results.

Also, I don't believe that you are shooting "too fast" but you may want to slow it down as much as you can stand to see if it makes any improvements. I do not see how this could possibly bring your POI in so many directions. It is very unusual what you have described to us I feel.

If you haven't already, have an experienced shooter (not nocking your abilities, just trying to add suggestions as help) get behind the rifle and see what happens when they shoot. Don't just ask the guy next to you or anything like that but see if you can meet up with someone who does well at local competitions and what not. Or even meet up with someone here to see if they can help you out.

But all that being said, my guess is still that there is a contact point on the barrel somewhere which is causing your problems. I may be wrong but I do have a gut feeling. If all else fails look into bedding the action into the stock, and if that doesn't work, then all I can suggest is that you take it to a local smith and have him look it over and see if he can figure the problem out.

Good luck,
-Dylan

 

[valise]

Re: POA / POI change, barrel heated?

We're just pre-monsoon here which means calm mornings and afternoon thunderstorms....good range time for two targets.

50y zero, five shot group, then waited for 15 minute cease fire interveral to move the target.
Same ammo, rifle, bipod, scope and range (Prescott actually).

Started at 25, same target at 50, then same target at 100.
At 100y I could see 2.5 inches of wind drift.


Then decided to reverse it.

Target at 100 - able to correct wind drift with hold, same target at 50, same target at 25.

As I see it...
I can put the first hash mark low of the MOA reticle on the target at 25y and it's good.
At 50y I'm a trace high on my zero.
At 100y I do not yet have the skill to call a true measure of accuracy. Hit's rise as I fire and barrel heats.

The rifle is neither free floated or bedded, but what I've read on the Ruger 77/22 is mixed results to no change. I would like to lighten the factory trigger some.

Since this slow fire is more akin to bunny hunting I think this is good enough out to 50y.
I can practice slow fire technique at 100y in preparation for big game hunting.

 

[SmallBoreSnipers]

Re: POA / POI change, barrel heated?

I was right on at 50 when I got my boyd's stock but horrible at 100. Just had to sand out the barrel channel a little bit and that fixed it completely. Also my POI starts to walk down on me if the barrel gets too hot, but I'm talking about the high velocity of the .17 HMR.

 

[00Buck]

Re: POA / POI change, barrel heated?

Do you have much experience with shooting targets in general? Any other rifles that you shoot?

I would take the advice of others on here and see if you can get a friend (who has established shooting skills) to shoot the rifle and see how it does. That should give an indication if it is something in your particular shooting process, or if the rifle has an issue that you need to look into. I don't know much about the HM2 but I would think it should group much tighter than what you are seeing, and certainly be more consistent.

By the way, until you can establish a solid zero I would stay away from using the reticle for hold. You just start to cause confusion by doing so.