What's going on here?

[Jefe's Dope]

I recently purchased 20 pieces of once fired Alpha OCD 6GT brass to supplement the 200 pieces (199 after sacrificing one piece to an AMP annealer) that I had purchased prior for my new 6GT barrel. I decided to load up the 20 pieces with a similar load, although different bullet, to my other pieces and "fire form" them to my chamber prior to annealing and adding to the rotation of my other 199 pieces. Those are all on their third firing after annealing after two firings since new. All was going well, see below, until the last 7-8 rounds fired. As you can see, the last seven rounds began to move down. I had the Magnetospeed attached and there was essentially no change in speed. My initial fear was 1. that there was a baffle strike, 2. Magnetospeed strike, or 3. the reticle in my scope had moved. I decided to take the rifle back to the range and shoot some rounds of known quality to see what I could find after inspecting the baffles on the suppressor and the Magnetospeed wand with no indication of any kind of strike.

Continued below pic.

After shooting the first five rounds, I was relieved to see that my zero had actually not changed and all looked good. Until I shot the second five rounds which seemed to move again. (see below). I continued with another five rounds after making minor adjustments to elevation and windage (after turning the turrets a few rotations and returning them to the 'new' zero) and the group tightened back up but moved to where I had adjusted. Then I returned my turrets to the old "zero" and all was well again for the last two groups of five rounds.

So, what's going on? Is it just me and my POI changing due to slight adjustment for the different target via Chris Way's POA/POI change due to different angle of sight from the shooter? I've always noticed a slight change of POI with the different dots in the past as well. I've 'decided' that it was due to the slight angle of change in POA due to not moving my position, just adjusting the rifle on the bench, again via Chris Way's observations/teachings.

 

[supercorndogs]

POI seems too me to usually trued down when I shoot strings with a magneto attached. In the attached picture the long string is all the charges shot over a magneto speed at the target above. You can see the charges don't string down like that when shot without the magneto attached. Not saying its a thing for sure, but i feel like I have seen it a few times.

 

[RegionRat]

my new 6GT barrel

Can you describe the rig a little in terms of bbl profile?
Some bbl profiles heat up fast and drift, others wouldn't show that tendency in so few shots.

Since you already stated there was no trend in speed, I would also ask if there is any evidence of a stock screw coming loose or the scope mount coming loose?

I'm a fan of the MS, but don't like to judge target performance when one is mounted on a medium or lightweight bbl that tends to make it come loose.

 

[Jefe's Dope]

Can you describe the rig a little in terms of bbl profile?
Some bbl profiles heat up fast and drift, others wouldn't show that tendency in so few shots.

Since you already stated there was no trend in speed, I would also ask if there is any evidence of a stock screw coming loose or the scope mount coming loose?

I'm a fan of the MS, but don't like to judge target performance when one is mounted on a medium or lightweight bbl that tends to make it come loose.

Heavy profile barrel. The MS was attached to the chassis, not directly on the barrel. I intended to check the action screws but did not. Thanks for pointing that out.

 

[Aftermath]

Also, are you positive the barrel is free floated and not touching anything?

 

[Dstoenner]

It could also be your throat is carboned up. Or worse yet your barrel died. I would see this with barrels at end of life although it was usually at about the 40 round mark after cleaning

David

 

[Jefe's Dope]

Also, are you positive the barrel is free floated and not touching anything?

It is.

 

[Jefe's Dope]

It could also be your throat is carboned up. Or worse yet your barrel died. I would see this with barrels at end of life although it was usually at about the 40 round mark after cleaning

David

Just passed 500 total rounds recently. And cleaned it recently as well.

 

[RegionRat]

Borescopes used to be an expensive rareity, but now they are cheap, portable, and easy to use.

Most of the time if I throw the range tools in the truck, I have the borescope with me. It gets pulled out at the club a lot and has had an impact on many folks.

I would study that bore. I doubt anything will come of it, but best to cross that off the list than to have it bite you.

 

[Jefe's Dope]

Borescopes used to be an expensive rareity, but now they are cheap, portable, and easy to use.

Most of the time if I throw the range tools in the truck, I have the borescope with me. It gets pulled out at the club a lot and has had an impact on many folks.

I would study that bore. I doubt anything will come of it, but best to cross that off the list than to have it bite you.

Already have a borescope. Will give it a look.