How to stop cold bore shift?

[TackDriver284]

Took the 300 Win Mag out today, I loaded just 3 rounds after changing seat depth another .020" deeper, total depth is .040". Using 200 Accubonds and H4831 with 2X fired Norma brass.
A few days ago, first shot was at 12 o clock high about 1 inch, then 2nd and remaining rounds shot right and low at an inch @ 100 at 2 o clock, this morning it did the same thing, and previously did the same thing with H1000. This is getting on my nerves. Barrel was cleaned prior to shooting 20 rounds. How do I eliminate the cold bore shift?
Do I seat deeper?
Do I switch to 180 Accubonds from 200 Accubonds?
Do I switch from Norma brass to Lapua brass?
Tinker with the action screws, loosen it and retighten? Sequence and torque specs? I believe its pillar bedded.


Nilgai hunt is on the 13th of January. I like to be ready for it.

 

[wildman]

I fought this off and on for a good while with a 7-08 i just kept shooting and it finally went away first would a 1/2 to a inch out of group next 2 would be cutting bullet holes .I think it has a lot to do with barrel fauling .

 

[RL338]

This is the selling point behind HBN bullet coating. Your first clean bore shot stays in the group. I’ve tried it and since moved on.
How many rounds does your barrel have on it? Not quite the fire breather as my 30-378 , which developed that same issue. What I started doing after I cleaned the barrel was working the first few inches of the barrel with JB paste. Smoothing out the fire cracking did help on first clean bore shot.

 

[bdbrown66]

Make the first shot count.

 

[TackDriver284]

This is the selling point behind HBN bullet coating. Your first clean bore shot stays in the group. I’ve tried it and since moved on.
How many rounds does your barrel have on it? Not quite the fire breather as my 30-378 , which developed that same issue. What I started doing after I cleaned the barrel was working the first few inches of the barrel with JB paste. Smoothing out the fire cracking did help on first clean bore shot.

I do have some fire cracking in the throat and maybe an inch out in the bore, but its not that awful. Not sure on how many rounds in the tube, probably about 500 give or take.

 

[jimbires]

this is a tough one . I'm not sure what causes it , or how to fix it . I've JB'd the throat , I've shot a clean lightly lubed barrel , I've dry patched a clean barrel before going shooting ,I've let the barrel fouled , I've dry patched the fouled barrel , I've tried different cleaning products and regimens , never fixed it . I've had the bolt apart and cleaned it up inside , and the firing pin . if I remember right I have (had) a couple rifles that put the cold bore round in the group , but now after many rounds , I don't think any of mine will do that . I'm not sure if it's barrel wear , barrel stress , or what it is . I really don't think it's ammo related.

I'm watching this one with great interest . I'd sure like to see someone tell us what's causing this .

 

[TackDriver284]

Readjust the pillar bed action screws? What is the sequence and torque specs?
I could start with that, and change my brass and bullets back to 180 Accubonds and see

 

[jimbires]

a remington , or clone action , if it's pillar bedded 65 in lbs . if it's not , I think it's 30 in lbs

 

[JD338]

a remington , or clone action , if it's pillar bedded 65 in lbs . if it's not , I think it's 30 in lbs

That's correct for pillar bedding. Conventional wood stocks I torque to 25-30 in lbs.

JD338

 

[TackDriver284]

a remington , or clone action , if it's pillar bedded 65 in lbs . if it's not , I think it's 30 in lbs

Front screw first then rear?

 

[flyingagg]

Front screw first then rear?

Yes. start at 20 in lbs, front then rear...continue to 65 in lbs. Posted in LRH the procedure from a late member

 

[TackDriver284]

Yes. start at 20 in lbs, front then rear...continue to 65 in lbs. Posted in LRH the procedure from a late member

Done, stood the rifle up after loosening, a little smack on the butt and pushed the barrel down to keep the lug against the stock, then started front screw at 20 in lb, then rear, front again at 40 inch lbs, same sequence and final at 65 inch lbs. Thanks

 

[TackDriver284]

Ditched the 200 Accubonds and H4831, got no time to play with it, going back to my old load with 180 Accubonds and RL22, only got a pound left. Notes shows speed at 3175 fps with 74.4 grains. Still have a pound of RL 26 as well. Hope that cold bore goes away.

 

[TNBillyEarl]

TackMan - I did every thing mentioned above and then some on my mountain 700 7mm08. I literally spent 3+ years on this cold bore problem. My rifle did this from day one, clean/dirty/or in between. I finally found two solutions: 1) I shot the same target 24 hours later and again 24 hours later getting a nice little clover, and then 2) I finally found a load with 140g BT or AB's using Varget. It wasn't seating depth, or action screw ft/lbs, or pillars, or cleaning, or bedding, or even barrel heat. It's just a form of sorcery of which I am not familiar.

-B

 

[RL338]

Has this rifle displayed this problem with other bullet or just these 200gr AB?
Either way it sounds like you got a good back up load.

 

[TackDriver284]

Has this rifle displayed this problem with other bullet or just these 200gr AB?
Either way it sounds like you got a good back up load.

I have not seen it do cold bore shifts before.

 

[300WSM]

I fought this off and on for a good while with a 7-08 i just kept shooting and it finally went away first would a 1/2 to a inch out of group next 2 would be cutting bullet holes .I think it has a lot to do with barrel fauling .

This.
And..
Just my opinion but the hot and cold thing get seriously over blown.
To each their own but there is heat and then there is real HEAT...which bolt guns won't/can't see.
Automatic heat will have an impact which bolt guns simply cant get that hot.

Fouling is a huge ordeal.
some guns worse than ithers.

I had a 7 odd 8 that woild put 17 rounds one ragged hole.
shot #18 would start walking. Every time with that particular load. 1-17..no problem.
shot 18....
starts walking.
I'd be more concerned with that than your cold bbl suspicion.

Thats just my opinion...

Good luck

 

[sako2]

Lapping the barrel may help.

 

[TackDriver284]

Went out again to the range to test my old load from 4 years ago after ditching the 200 Accubonds / H4831 because of cold bore shifts. I used 180 Accubonds / Norma brass, CCI 250, and RL22. I used someone else's paper target that was on the board. Ignore the smaller holes with the circles and x's. First shot was on the tip of the small diamond on the right which is cold bore, 2nd was above and 3rd shot was back in the same hole as the cold bore. I waited a minute between shots, 2nd three round group is on 2nd picture, first and second shot in the same hole at the tip of the diamond again, and third shot slightly above it, 3rd three round group POI is slightly moving away from the tip of the diamond. I did not see any cold bore shift today, cold bore is within the groups.
Velocity:
74.4 - 3125, 3134, 3134
74.7 - 3125, 3130, 3126
75 - 3127, 3125, 3168

The 3168 fps case will be sent to the sighters pile until I check it out some other day. Not sure why the velocity spiked. The test seems to be going on the right track to figure out the cold bore issue, but it does not mean its confirmed until I redo loading more rounds of 74.7 grains and its .020" off the lands, I have no interest in tweaking this load at this point, the load seems good to me and ES is fantastic, but one thing I don't like is temp swings. I have no intention to increase the charge of RL 22 because I don't want pressure spikes in the hot dog days of summer. It's 68 degrees out right now. I pulled the target back to get a better view of the impacts on the cardboard. Not shabby.

 

[flyingagg]

Went out again to the range to test my old load from 4 years ago after ditching the 200 Accubonds / H4831 because of cold bore shifts. I used 180 Accubonds / Norma brass, CCI 250, and RL22. I used someone else's paper target that was on the board. Ignore the smaller holes with the circles and x's. First shot was on the tip of the small diamond on the right which is cold bore, 2nd was above and 3rd shot was back in the same hole as the cold bore. I waited a minute between shots, 2nd three round group is on 2nd picture, first and second shot in the same hole at the tip of the diamond again, and third shot slightly above it, 3rd three round group POI is slightly moving away from the tip of the diamond. I did not see any cold bore shift today, cold bore is within the groups.
Velocity:
74.4 - 3125, 3134, 3134
74.7 - 3125, 3130, 3126
75 - 3127, 3125, 3168

The 3168 fps case will be sent to the sighters pile until I check it out some other day. Not sure why the velocity spiked. The test seems to be going on the right track to figure out the cold bore issue, but it does not mean its confirmed until I redo loading more rounds of 74.7 grains and its .020" off the lands, I have no interest in tweaking this load at this point, the load seems good to me and ES is fantastic, but one thing I don't like is temp swings. I have no intention to increase the charge of RL 22 because I don't want pressure spikes in the hot dog days of summer. It's 68 degrees out right now. I pulled the target back to get a better view of the impacts on the cardboard. Not shabby.

I would stick with that for now and hunt. I would check it in the summer. I use RL 22 with AB in my 300WBY with great success. I do not think it’s as temperature sensitive as people say.