Range Report Cold Bore Shot

[dallenvance.gunter]

I'm shooting a 30-378 Weatherby with a 5-20 Huskemaw. My 210 grain Berger VLDs have been shooting .75 MOA groups, but the past couple times I have shot, my cold bore shot is about 3 minutes off of the rest of the group. The shots after are hitting where they need to and are still grouping well. Any ideas on why it's throwing the cold bore so far off?


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[stanley52]

What's your cleaning process look like? (After how many rounds do you clean your bore and what do you do to clean it). Also, try doing some dry fires before your first round. A lot of people cook off a funny first round because they don't focus on fundamentals, the bigger the caliber, the bigger this effect comes into play.

Also, try zeroing your rifle this way, clean it, shoot 4, let it cool for 30mins in the shade. Then shoot 3 rounds with 15mins in between each shot. This will give you your true cold bore zero for hunting applications where your first shot is basically what counts.

 

[dallenvance.gunter]

I'm cleaning between 200 & 250 rounds. I'll try the dry firing and focus on being relaxed, it has a muzzle brake, but I still get a little tense sometimes shooting that gun. I'm pretty new at high performance shooting, so I I need more practice too. Thanks for the advice. I'll experiment some more to really know where my cold bore impact is.


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[Jon Lester]

Lot of my cold bore issues turned out to be cold shooter issues.After the ice was broken i tended to settle. Before shooting your cold bore, dry fire 6-7 shots and see if their is a difference.

 

[USMC 0231]

I agree with Jon. I did an experiment at work with my team. If we dry fired a few times first, our cold bore deviation almost completely away. It's also more about clean or dirty bore first shot.

 

[stanley52]

How many rounds do you have out of that 30-378? I would be willing to bet it doesn't have much life left if you have had several iterations of 200-250 rounds, a shot out barrel can send flyers that look like a POI shift.. But yes I agree it's probably a combination of the barrel being "too" clean and being tense before your first shot. Try not using a bore brush if your use one. Try Hoppes no. 9 wet patch a few times, let it sit for 20mins, dry patch, oil, dry patch, ever 120-150 rounds, and see what that does with your POI. This should make it so 1-2 fouling shots will have you on the money, and your first shot will still be very close. Many other cleaners are too aggressive and clean the barrel to way too much, so that the conditions within the bore are dramatically different from 1st shot to last before cleaning. Definitely listen to the "cold bore" zero" and dry fire advice up above if you want that first shot perfection.

Just my 2 cents

 

[colson]

For me it's all about "Cold Shooter", not "Cold Bore" or "Clean Bore." Like the devil dog said, DRY FIRE.

 

[nwdrifter]

I don't know how you shoot but I will add maybe ammo temp

cold bore ammo temp is one muzzle velocity and if you are loading follow up rounds into a warm chamber and giving them any time to warm up in the chamber the ammo is at a higher temp and will have increased muzzle velocity.

 

[dallenvance.gunter]

Stanley52 I only have about 600 rounds through the rifle, so I hope it has some life left. I know barrel life is detrimental by velocity and caliber, but I've mercer shot anything over 3400 fps out of it. What is the average for barrel life in the bigger magnum rifles?


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[redbullitt]

I vote cold shooter. If it still groups I would bet your barrel is good to go, at least for a little while longer. Barrel life, I am not sure about your rifle. Maybe 2k rounds?
FWIW I have shot out a 243 win barrel. I knew it when it was shot out lol. It was grouping well as usually, then it just started opening up more and more.

I think you will notice when you kill that barrel.

Do the dry fire warm up. I wager you will see a difference.

 

[stanley52]

I vote cold shooter. If it still groups I would bet your barrel is good to go, at least for a little while longer. Barrel life, I am not sure about your rifle. Maybe 2k rounds?
FWIW I have shot out a 243 win barrel. I knew it when it was shot out lol. It was grouping well as usually, then it just started opening up more and more.

I think you will notice when you kill that barrel.

Do the dry fire warm up. I wager you will see a difference.

I have heard of 30-378's having noticeable accuracy degradation after literally a few dozen rounds. I'd say after 600 rounds you're nearing the end of its peak accuracy life. A 300 RUM which has a smaller case capacity is only going to give you about 1000 rounds of peak accuracy, maybe. It's probably a cold shooter/too clean barrel issue. Your barrel should probably still perform, but if you have eliminated all other possibilities then you there becomes a point you must trust yourself and what you are doing. When a barrel is shot out, all accuracy does not go away. When a throat erodes what it does is increase the likelihood of flyers. You still may get some groups that are .25 MOA, but you may also have inexplicable 1 MOA groups.

Edit: just to clarify the barrel life estimations are only my best guesses. I could certainly be misguided and you should probably research it a little more.