Cold bore way off consistently

[Luftwolfe]

LWRC MK2 Repr 12.7 Inch with Q-thunderchicken can, using 175g Federal gold metal match, looking through my dope book Ive noticed a repeatable fluke.

First round is often about 2mil high and 2 mil to the left, often resulting in a over the shoulder/ear shot on a 20x12 man steel torso at 330meters.

Once I get about 3 rounds down the pipe the groups tighten into my original zero spot, but its randomly made me guess my dope and last zero, often to the story of wasting a box of ammo to confirm.

I am going to try to see if it happens with the same bullet but in 168grains...any other tips would be helpful, and yes I did warmups before.

 

[alamo5000]

I am not being a smartass here but this sounds more like a statement than a question. Which would most likely be correct, and it would result in you changing your POA for that first shot.

Tracking cold bore shots is definitely a thing.

 

[Luftwolfe]

I wasnt sure if harmonics or ammo could be a culprit, and I have often made many cold bore shots at the distance in the past without recording any strange drift so Im just kinda confused. And also not sure if the cold bore could make such a drastic impact shift, but thanks maybe Ill try a hold next cold bore and if that fails I could just zero to that point and see what the shots after do.

 

[Jrb572]

Are you cleaning it every time before the next range session?

 

[alamo5000]

I wasnt sure if harmonics or ammo could be a culprit, and I have often made many cold bore shots at the distance in the past without recording any strange drift so Im just kinda confused. And also not sure if the cold bore could make such a drastic impact shift, but thanks maybe Ill try a hold next cold bore and if that fails I could just zero to that point and see what the shots after do.

Any of those things could be the problem. If you were shooting whatever ammo/load and it was fine then all of the sudden it changed is one thing. But if you are just trying something out or testing a new gun... there are a million things to consider. The first post wasn't clear on the situation.

In the best of rifles the cold bore will most of the time have a poi shift. With most rifles and most shooters though they are not noticing because they are not trying to notice. An offhand shot at 100 yards while running some drill and using 'sufficient' ammo would not indicate one way or another.

If someone is shooting cheap ammo they won't be able to tell much one way or another (in general). If the POI shifted 1" to those guys they would never know nor care.

If your gun is shifting a couple of mils though, that seems like a lot to me.

 

[Luftwolfe]

Its really hard to read to the trace by myself, maybe ill setup a drone down range hovering next time so I can see how much it misses by. Its somewhere between .5-1.0 mil im pretty sure up and left. This was also not in my logbook until I got my can fixed by Q, they missed a weld and it went flying down range about 3 months ago with less than 1k rounds under it.

This rifle has 300 rounds through it, I have not cleaned the bore yet, should I? I figured 300 was just enough to start a nice carbon build up for consistency

 

[Jrb572]

No don’t clean it. It was just an easy reason it was off for a few shots if you had

 

[alamo5000]

First round is often about 2mil high and 2 mil to the left, often resulting in a over the shoulder/ear shot on a 20x12 man steel torso at 330meters.

Its somewhere between .5-1.0 mil im pretty sure up and left.

This is a major discrepancy in what you are asking...

 

[BCP]

Well match M1As do that shit constantly and it has to do with the bedding and unitizing + barrel stress. Maybe the suppressor you have is part of the problem?

 

[rbutcher]

about 95% of the time, its a cold shooter and not a cold bore problem

 

[MarshallDodge]

about 95% of the time, its a cold shooter and not a cold bore problem

I tend to agree with this. 2 mils is a lot of difference. The worst cold bore rifle I have ever shot was less than 1 MOA.

 

[supercorndogs]

You need to shoot at a piece of paper for your first few shots each time and map your cold bore shots. We can't guess how much you are missing, you shouldn't be guessing how much you are missing. 2 mils would be something major. That is a huge shift. My guess is something else is going on if its that much. You have any pictures of your set up?

 

[smoothy8500]

, looking through my dope book Ive noticed a repeatable fluke....made me guess my dope and last zero, often to the story of wasting a box of ammo to confirm.

Its somewhere between .5-1.0 mil im pretty sure up and left. This was also not in my logbook until I got my can fixed by Q

A lot of guessing and spotty logbook entries...

If you're doing "warm-ups" as you say, then you need to actually track your first rounds on paper and measure.

 

[Back Spin]

The best rifles should not have a cold bore shift. If there is a repeatable cold bore shift, there is a problem that needs to be addressed. Have you shot the gun without the suppressor to see if the problem persists? That would be about the only thing I would suggest prior to sending it back to LWRC. Ammo is too precious to be chasing these problems.

The fact the zero returns after 3 shots or so probably means something is moving back in a consistent place as the gun heats up, but what that thing is may be hard to discern without much trial and error. Case in point, the very first precision gun I got was an AIAT. Cold bore shift of 2 minutes left. Took 5 shots to settle into previous zero. Being new to precision rifles I initially chalked it up to a combo of shooter error and just the way things were with these guns. After much trial and error, as far as I could tell, I discovered the problem. The trigger pack screws were not torqued to spec (one was significantly looser than the other). As soon as I torqued both screws to the same value, the problem went away. It took a bunch of ammo to finally sort it out though.

 

[st1650]

Could perhaps be the scope mount ? Then the recoil from the first round press the cross bolt lug into the pic rail ? Are you using a Larue QD mount?

 

[st1650]

I would also try it without the can just to remove all possible elements

 

[KineticPerformance]

You need to shoot some paper and determine if you really have that large of a shift. That is a huge number. I've had a ton of .308 gassers over the years and never seen one that extreme and they've mostly been KAC with their bullshit can which doesn't always play nice.