Can someone explain this?

[kraig]

The only time I've ever had the problem of cold groups being 1/2 the size of hot bore groups was when my Savage BVSS in 7mag had part of the stock just barely touching the barrel. If I let it cool between shots it would shoot 1/2 moa easy, if I tried to do a 5 shot group, shot number 3 would move out past 1 moa every time and 4th & 5th shot were worse.

I've not had that problem with my Savage 110 25-06 nor my Encore 25-06 and I shoot the Nosler 117g bullets loaded with H4831sc. I've really never done more than 3 round groups with them so a 1/2moa group doesn't mean much statistically. It didn't take a while to get the charge weight and seating depth just right for the heavy bullets vs. something down closer to 100g. The lighter bullets in 25cal seemed to be easier to group but I wanted to shoot the heavier ones so I kept at it until I got what I needed.

 

[DJ Fergus]

The guys I know that shoot 25-06 all shoot 100 gr. and under bc of lost accuracy +100 gr

Yeah, I think some folks do fine with 100 & over in the 10 twist barrels but most of the 10 twist barrels I have saw will shoot lighter than 100 better.

 

[DSheetz]

In my limited experience I have noticed that some rifles like one brand of bullet of the same weight over other brands and one powder brand or burn rate powder over others . Making it fun and challenging to find the right combination that performs in our rifles .I think it may be a lot of things that play into this , the manufacturing process,shape of the bullet type of metal used ect. as well as how the barrel was made of what metal , the twist rate , number of rifles how well it was done each lot of metal has small amounts of variances in it's composition and manufacturing causing a difference in how it reacts to the process of being turned into the final product . A powder has the same variances from lot to lot one lot may burn a slight bit faster or slower then the last ,or next one depending on the measurements of the different components being off just a slight amount as well as the temperature , humidity during manufacturing shipping and storage . Today most manufactures have tighter quality control then ever before making for more constant products then ever before

 

[DSheetz]

I had a bad re-barrel job one time the bore wasn't true to the outside diameter of the barrel so the first shot was 3 " left , the second was right on then the 3rd was 3" to the right after that all shots were a good group uneven heating of the barrel moving it slightly side to side .

 

[Orange Dust]

We always shot a 117 Sierra in a 25-06. Wild guess is not enough clearance in the barrel float. Spotter barrels need even more than a hb. YMMV, but I have never had an issue with cold bore shots shooting different from the others with HBN coated bullets. I've had such good luck with this I will not hunt with an uncoated bullet in a long range rifle.

 

[John 264]

I was thinking today about something I ran into about 7-8 years ago when trying to work up a load for a 25-06 and have saw a similar thing happen with a 300 win mag. I was trying to get 1/2 moa three shot from a sporter rem 700 25-06 with 110 accubonds. Bedded & floated in a fiberglass stock. I never could do much better than 1.25 moa with those bullets in one setting or in one day. I now shoot 80gr Barnes into consistent sub .5 moa but don't really use the rifle much any more. I believe a combination of heat & not enough twist (factory 10 twist barrel) was contributing factors for lack luster performance with heavier bullets. What really bewildered me about the 110 accubonds & also 115 partitions in that rifle is that they would print near half moa on cold bore shots if I would make three separate cold bore shots over a course of three separate days, one shot per day. I repeated that @ 100 and also at 500 yds. And that was on an uncleaned overnight cold bore. Any thing more than one shot per day at I got 1.25 moa. I eventually went to the Barnes 80gr, shot great I and moved on. Have any of you fellows saw anything like that?

The guys I know that shoot 25-06 all shoot 100 gr. and under bc of lost accuracy +100 gr

There are many different factors that can and will cause the accuracy problems you are experiencing because a 1/10 twist will stabilize the 110 thru 120 it could be the bedding the powder the crown it could be the primer the brass the trigger or the bullets they are not the best in that weight range (what kind of brass are you using) you need to weigh it and sort it in 1 gr lots that can make a big difference

 

[John 264]

I had a bad re-barrel job one time the bore wasn't true to the outside diameter of the barrel so the first shot was 3 " left , the second was right on then the 3rd was 3" to the right after that all shots were a good group uneven heating of the barrel moving it slightly side to side .

Did you know that 8 out of 10 factory barrels the hole is not in the center so much so you can see it with the naked eye that doesn't mean that they will not shoot good groups

 

[flashhole]

My 25-06 is a Ruger #1V with the bull barrel. During load development I discovered what you may be experiencing, first shot out of a clean cold barrel was very consistent. Other shots in the same session walked a bit as the barrel heated up. With mine it is absolutely predictable, down and to the right.

Sweet spots are there with both light and heavy bullets. It likes 87 grain Sierras and Noslers. It likes Nosler 115 grain Ballistic Tips and Sierra 120 grain Hollow Points. Could never find a load it liked with 117 grain bullets.

H-4831 and Retumbo have been the go-to powders with light and heavy bullets.

Never had any success with H-1000 in this caliber. Reloader 25 is a bit temperature sensitive but accurate.

Primers didn't seem to make any difference in accuracy. I ended up using Magnum primers because it was a good fit to the tall powder column and I used to live in a cold climate.

I bought my 25-06 thinking it would do double duty as a varmint and deer gun. It really shines with the heavier bullets and a 25 cal is way overkill for varmints. It will blow a groundhog, opossum and skunk completely in half. It will really tear up a coyote as well. I like the controlled expansion bullets on deer. Huge impact shock but cuts a clean hole.

 

[Mc Fraser]

Assuming we are talking about 100uds shots can one run out of twist?

 

[MagnumManiac]

I also use magnum primers, have tried CCI, Federal and Winchester.
Winchester gave me the tightest groups with 99% of my loads.
I only shoot/load one bullet in all but one rifle, the Ruger and Rem use the 110gr Accubond and the Kimber loves the 115gr Partition.

I have shot rabbits and hares with the Sierra 75gr HP, red mist, hide and guts was all that was found after shooting them in the head FRONT ON.........yes, it ripped the hide and guts out with front on head shots right down the back past tge shoulder. How this occurs I am unsure, but seen it numerous times.

Cheers.

 

[just country]

morning, I have used the 4831 powders in
2506, 270w, 3006, 7mm, 243, 257, and a few more.
with the heavier bullets works just fine.
justme gbot tum

 

[Bravo 4]

I've had (issued) rifles that would consistently have what some folks call a "cold bore flier". If I have to shoot that ammo through the rifle (as with military issue) I do not call it that, the others are the fliers as the first round is the one that matters most. I would check it to make sure it printed that first round (as you did) consistently to the same poi and keep that documented, and then where the others grouped. Also do this with a clean cold bore as you never know when something unforeseen may happen and you need to clean the barrel, and be somewhere that fouling shots are undesirable.
Now since I have to shoot certain ammo through these rifles I noticed with some under "hypothetical situations" (because altering ammo is against regulation) that if I changed the seating depth a bit (as mentioned by another poster) that sometimes the rifles would group better and the supposed fliers would/may be eliminated almost entirely. Since we are talking "hypothetically" I may have even had a hand held press that I carried to adjust seating depth a little for each rifle and kept it documented in each rifles' data book.
Hypothetically speaking of course.

 

[azsugarbear]

I have found peculiarities in several of my rifles - things that just can't be explained. I have taken to calling them "gremlins in the system". I had Kirby Allen build me a custom 6.5-06 AI back in 2009. It was designed with a 1 in 8 twist barrel to shoot heavier bullets - specifically the Berger 140 VLD's. Try as I might, I just could not get the accuracy I new the rifle was capable of with those bullets. I finally switched to the 130 gr. accubond and started shooting 1/2 MOA with two different powders. I developed a second load with 160 gr. Matrix VLD's. Same results. Just for grins and giggles, I went back to the 140 gr. Bergers. Nope. My rifle just didn't like them.

There is no logical reason why I can't feed this rifle a diet of Berger VLD's. It's just gremlins in the system.

 

[DSheetz]

azsugarbear , that same rifle might shoot 140's of a different brand just fine I've seen that in some of mine also.