Advanced Marksmanship Cold bore shot always .2mils high/.1mil left, why?

[JB02]

Question for you, my cold bore shot is always 0.2 mils high and 0.1 mils left. This is sorta convenient to know as a hold over, but I was wondering why this is so? My remaining shots always hit my previous zero. This phenomenon is consistent whether I'm shooting at 100 or 400 yds.

Barrel is a 24" 1/10 MTU .308 Krieger.

Thanks for any insight.

 

[LawnMM]

Re: Cold bore shot always 2mils high/1mil left, why?

If your bore is completely clean and devoid of copper, the rifling are in a different state entirely than after the first shot, or first few shots. As the bullet travels down the barrel, copper from the jacket is pulled off by friction and it begins to fill in some small nooks and cranies in the rifling and inner profile of the barrel.

When subsequent shots move down the barrel, the rifling and copper content in the barrel, are different than with a freshly cleaned barrel. This is why many will advocate you not clean your rifle until accuracy degrades. That way you aren't constantly forcing the metal on metal interaction between the barrel and the projectiles to begin at such a high friction point.

However, at some point all the crap in your barrel will have the same effect from a clean bore shot, but in the opposite direction. It will begin to negatively affect accuracy. FYI I've gone several hundred rounds, 500 and beyond, with no degradation in accuracy.

The clean bore versus fouled can account for a shift in accuracy of the rifle from its zero, but I doubt as much as a mil. Its more likely that you, the shooter, are warming up, and your technique settles in on subsequent shots. That's easy to check, have somebody else shoot your rifle and see if they see the same shift on a 'cold' bore. Clean Vs Fouled has some merit, Cold Vs Warm tends to be the shooter.

 

[Lowlight]

Re: Cold bore shot always 2mils high/1mil left, why?

That is not a clean bore / dirty bore issue, 2 mils is huge something is wrong or you have a heck of a first round flinch...

Get someone else to try it or send it back to the builder because that is bad, and not consistent with how any rifle should be .

 

[JB02]

Re: Cold bore shot always 2mils high/1mil left, why?

Oh boy! Sorry I meant to type 0.2 mils up and 0.1 mils left. It's only a small amount.

It cannot be flinch because it's a heavy rifle with a Badger FTE ... practically no recoil. I can easily hold over .2 mils down and .1 right and I'm dead on for the first shot. Subsequent shots go right to my zero.

My scope tracks fine.

 

[JB02]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">2 mils is huge something is wrong </div></div>

Yes, that would be a true statement if that was the case ;-) But the rifle shoots .25-.375 MOA groups, so I'm not sending it back.

I cleaned it once after shooting the first 50 rounds, and there was no copper fouling. Haven't cleaned it since since it's shooting fine.

 

[Niles Coyote]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

Cycle through about 12 quality dry fires prior to going live, concentrating on your form/technique and advise if it persists.

 

[Lowlight]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

You absolutely can be flinching, people flinch from sound... it's not just recoil that causes a flinch. Many people have a first round flinch which is in fact the reason they see a shift on that first round. It's not a cold bore shift, but a cold shooter shift.

The corrected offset is more consistent with what people see, so the fact its, it certainly could be you.

There are numerous ways you can test this, shoot a different rifle first then go to this rifle. Shoot about 10 rounds before even touching the rifle with a shift.

Secondly, as stated you can be over cleaning it, there is good copper and bad copper, bad copper appears when you get about 1000+ rounds through most 308 rifles... good copper when stripped needs to be replaced, hence the shift from clean to dirty as stated above. So try cleaning it then firing 3 to 5 fouling rounds, put the rifle up and come back too it. if you find at your next range session it doesn't' shift any more you over cleaned it. If it shifted again, it could be you...

Mechanical issues, there are numerous things here, as some systems are just not as good as people expect, hence the deviations seen. Wandering zeros, first round shifts, or multiple rounds walking all point to mechanical issues.

 

[JB02]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

Niles, I'll try dry firing before the first shot, but I just think it's strange that I can hold over my first shot .2/.1 mils and be on target. I've done that twice now. Also, when I haven't held over the cold bore shot the previous two times, the shot was .2 mils up and .1 mils left. Perhaps I'm in denial over flinching, but it's just strange that I can call it.

There are 270 rounds down the pipe, and it's only been cleaned once, after the first 50 shots I did for my sight-in and OCW load workup. So I would be surprised if it was fouling. Since my groups are pretty tight, I'm reluctant to clean it.

My scope tracks fine and the rifle was professionally bedded by Surgeon, so I don't believe those are contributing factors.

Can you comment more on what you mean by "first round shifts"?

 

[Lowlight]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

You're calling it a Cold Bore Shift, hot or cold has very little to do with it.

If it was a heat issue it would walk, not shift. However Shooters cause a Shift...

If you think the system is 100% then the answer is YOU.... you have a Cold Mind Shift as opposed to a Cold Bore Shift.

Problems with the mechanics of the system can cause the first few rounds to deviate, or wander, if that is not the issue, and you say the rifle is fouled when you shoot it, it's not a Clean Bore vs Dirty Bore... if it is not something like a bedding issue, or a defective barrel, that leaves one crucial part of the system... the shooter.

 

[Bruiser_Joe]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

Yes!!!!!! Finally someone said it!!! Frank u r the man lol

 

[Niles Coyote]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

I have had almost the same shift on occasions, I either didn’t mount the stock to my shoulder in the usual location and/or have not relaxed the muscle’s in said shoulder. Dry firing helps me to correct for this and warm up my brain...

 

[Graham]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LT JGB</div><div class="ubbcode-body">I've done that twice now.</div></div>How many cold bore shots have you logged?

 

[JB02]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

Graham, I noticed it after I set my zero from the OCW load, four times on this rifle. I have never noticed this on any of the other rifles I own, but I'm going to look for it the next time I take them out.

My inclination was to believe that it was piss poor technique on my part, but being able to hold over the cold bore shot made me think that there was some other physical phenomenon at work. I'm actually somewhat relieved to read that the problem is most likely me.

I'll consider this a deficiency in my technique that I'll focus on overcoming. Niles, I'll follow your advice and see if that fixes the issue. Also, just to be sure, I'm going to have a couple of my shooting buddies try out the cold bore shot too.

 

[Graham]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

It could be you, but it might not be you. That's why I ask about consistency. I had a rifle that, for three thousand rounds shot a cold bore .3 Mils low every time. Then it stopped. But with that rifle the shots would walk. Have a look at the pic I posted in this Thread:
https://snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1077287

 

[JB02]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Niles Coyote</div><div class="ubbcode-body">Cycle through about 12 quality dry fires prior to going live, concentrating on your form/technique and advise if it persists.</div></div>

Doing this has resolved the issue. All five shots go through the same bughole now.

 

[Lowlight]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LT JGB</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Niles Coyote</div><div class="ubbcode-body">Cycle through about 12 quality dry fires prior to going live, concentrating on your form/technique and advise if it persists.</div></div>

Doing this has resolved the issue. All five shots go through the same bughole now. </div></div>

So the issue with the deviation was YOU the SHOOTER and not a mechanical issue with the rifle.

Cold Body, Cold Mind... Dry fire is the cure.

 

[Graham]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Cold Body, Cold Mind... Dry fire is the cure. </div></div>I knew a girl like that once; and that's what I told her.

 

[JB02]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LT JGB</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Niles Coyote</div><div class="ubbcode-body">Cycle through about 12 quality dry fires prior to going live, concentrating on your form/technique and advise if it persists.</div></div>

Doing this has resolved the issue. All five shots go through the same bughole now. </div></div>

So the issue with the deviation was YOU the SHOOTER and not a mechanical issue with the rifle.

Cold Body, Cold Mind... Dry fire is the cure. </div></div>

Yep, it's part of my "warm up routine." Last three times I've done this all five shots were dead on.

 

[JB02]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Cold Body, Cold Mind... Dry fire is the cure. </div></div>I knew a girl like that once; and that's what I told her.

</div></div>

LOL! That's a line worth remembering!

 

[leadbullet]

Re: Cold bore shot 0.2mils high/0.1mils left, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LCDR JGB</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Cold Body, Cold Mind... Dry fire is the cure. </div></div>I knew a girl like that once; and that's what I told her.

</div></div>

LOL! That's a line worth remembering! </div></div>

epic quote of pure awesomness.