Flabergasted and dumbfounded

[johnnyk]

Guys, need your inputs on this one.

Two weeks ago, I went to a nearby field we shoot at, set up my target for 1000yds and after plugging in the needed info in to my phone (using Strelok) I adjusted the scope as specified. I settled in and put 3 rounds just right of the bull by 4". Heighth was perfect and the group ran, 10-11". Not great, but I was satisfied because I completed what I went to do. I didn't rush but the actual shooting only took about a minute. Purpose shooting, I guess you could say. I was shooting my Savage 112 VLP, 6.5-284 Norma, handloads of 140gn A-Max, 59.0gn Retumbo, BR2's and Lapua brass (3038fps). Scope is a NightForce NXS 5.5-22x56 MOAR recticle.

Anyway, today my shooting partner and I started out at 1000ys and my bullets are hitting the target sideways. He's shooting a .308/168gn (Lake City Match ammo) and his are drilling holes like normal. What the.... Groups weren't much as you'd expect with bullets flying like that. My partner, meanwhile was doing about like normal with an occasional 5" group. Every now and then I would get one or two bullets in a group that actually flew true and didn't tumble.

Come ups were pretty straight forward at that first distance and the variable 5-10 mph wind took us both a couple groups to figure out but we settled in quickly. My app called for 20.37 MOA and I dialed 3 MOA for wind. We shot several groups here and then moved to 1100yds.

This is where confusion/frustration really set in. At 1100 my app called for 24.44 MOA and I dialed 4 for wind. My first group was dead on with the wind but approx. 2ft low!? and all three were sideways. I shot 3-4 more groups with similar results. On the last group, none of the bullet tumbled but was still low.

I didn't try to adjust my come ups at 1100yds, I guess because I trusted my apps data. I have run the numbers and data over and over and I come up with the same results. I also ran it through JBM and pretty much the same.

It was 82 deg, pressure was 30.04, alt. 69', zero range 300yds, BC .585. Not sure if I'm leaving anything out but if anything comes to mind or if anyone has experienced anything like this please chime in. I'm really puzzled as to why bullets were tumbling. The morning atmosphere was overcast and kinda "fuzzy", no mirage initially but crazy at 1100yds@ 12:00pm.

Help!! JohnnyK.

 

[Lefty7mmstw]

same batch of ammo for both the good hits the one week and the sideways hits later on???

 

[Mikecr]

Weird problem..
I don't see how supersonic bullets can tumble so far out. In my experience tumbling happens while gyroscopic stability is lowest, which is very near the origin(<50yds), and hitting much beyond that is out.

 

[Lefty7mmstw]

bounce in's???

 

[tbrice23]

Johnny, how many rounds have you shot since cleaning?


Incidentally,
Today my load of 140 vld 57.6 gr Retumbo 210m, which usually runs .2 to .5 MOA in 30° to 60° shot .6 to 1 moa in 78° in a Criterion bbl.

So I came home and decided to deep clean to bare metal and see what happens. I usually clean up to 50% completely clean.
I'm also going to go back .5 grains for next range trip.

My bore scope 45° mirror won't fit into the bore but the tube will fit but it's hard to see a carbon ring without the mirror. I'm hind of thinking I might be developing a carbon ring in the throat. No key-holing though.

 

[johnnyk]

Lefty7mmstw; Exact same ammo. No bounce-in's for sure. Very dusty dirt path and we spot each other.

tbrice23; Deep cleaned it before leaving to go shoot. No carbon or copper left that I could tell. I use an ammonia based cleaner and patches went from carbon dirty, slight blue tinge to totally white within 9 patches. What are some tings I can do to look for a carbon ring? If I do have one, how do I rid my barrel of it?

Mikecr; I agree, velocity should still have been 1550-1700fps, guesstimated, at 1000-1100yds. That's definately supersonic.

JohnnyK.

 

[BountyHunter]

Pull a bullet and reweigh the charge. Sounds like some charges were light.

 

[tbrice23]

Quote Johnnyk

tbrice23; Deep cleaned it before leaving to go shoot. No carbon or copper left that I could tell. I use an ammonia based cleaner and patches went from carbon dirty, slight blue tinge to totally white within 9 patches. What are some tings I can do to look for a carbon ring? If I do have one, how do I rid my barrel of it?


JohnnyK.[/QUOTE]

Barrow a buddy's bores scope or drag a patch and brush back through and you might feel more resistance neer the throat. Supposedly it is a hardened carbon GLAZE. Carbon deposits accumulated and repeayedly subjected to the highest pressures outside of the chamber.

The reason I ask is that I know how dirty Retumbo burns in this particular chambering.
It has been suggested using ISSO or some other mild abrasive only in the throat area, but I can't bring myself to do that. But I will suggest Boretech C4 carbon remover.

 

[Greyfox]

I have experienced this with plastic tipped bullets and would try a Berger or JLK 140. The keyholing is due to the bullet being destabilized. I'm not sure if this is the problem but it's possible that the plastic tip on the Amax is either cocking, deforming, or detaching during firing or chambering effecting the stabilization of the bullet.

 

[Mikecr]

Here's the thing though; gyroscopic stability increases as bullets get further down range(unless dynamically unstable), and the greatest moments to instability happen right at bullet release(while displacement per turn is highest). With a gyroscopic stability issue, the bullet would either tumble immediately or dampen out very early on.

The bullet here would likely have to hit something en-route, as it reached long distance, and there seems no cause for dynamic instability at that distance.

 

[J E Custom]

What is your barrel twist ? you may be on the ragged edge of stability with the twist and bullet combo.

Just a thought.

J E CUSTOM

 

[Greyfox]

The Savage 6.5x284's (and other6.5's) are 1:8 twist and mine snd others I have seen have no problem stabilizing 140 gr Berger/JLK's out to 1000+ yards. Looking at the OP's probem, I would go to the bullet first unless another problem with the barrel is obvious, like a damaged crown, etc.

 

[westcliffe01]

Is there any possibility that the bullet may be striking grass or brush either near the shooting position or near the target ? Often at the shooting position the scope may have a clear field of view when the barrel does not...

 

[bdpayne2000]

I am with Lefty and Westcliffe. They some way got deflected or bounced in. What makes me think this? Been there done that exact same thing. Chased all kinds of other things before my buddy and I based on some good feedback on this site figured it out. May be something else but don't dismiss it without really studying everything.