Cold bore conundrum!

[Bill Norris]

Agree with Jackie and Bart. If everything mechanical is tight there is something wrong with the load or the barrel is fouling very quickly.

 

[Flyshooter]

Having chambered at least 25 (I suspect more) 6BR zero freebores in 13.5-14 twist and using every major barrel manufacturer except Lija (nothing against Lija).

You more then likely have a mechanical issue or a one off barrel.....

Try this, load up some 55SBK with RL-7 try about 30 grains 10th’s off the lands, then the same using AA2230 about 35 grains and once more using H335 and about 34 grains......this is with Lapua brass and 450’s

Even in some wind one should print an inch or less at 300, the 6BR shoots the best at distance toward the upper end of the pressure envelope.

Remember, 6BR’s are superbly accurate, BUT there are not a PPC which rules the universe at 300 and less......for now anyways.

The above are my go to test loads for every newly chambered 6BR zero freebore and I’ve not had one shoot decently yet......seriously.

One other thing I’ve noticed but can’t say it as fact, pointed bullets will shoot better at distance when not using wind flags.......Seen it enough to alter my loading when shooting steel and we’ve no wind flags to interpret.......especially bad are hollow points that have a large openings......

Oh, and check to see it’s not copper fowled, particularly the last 8-10 inches of the barrel......Good Luck Fella.....I love 6BR’s.

 

[BartsBullets]

Here’s maybe or maybe not a relevant static. At the Tack Drive a 300 meter shoot. The average group size is right at 1.6 inches. Thats pretty much the average for all 4 of the Tack Drivers. Which is 5 groups of 5 shots. With 80 to 99 shooters bringing the best they have.

Bart

 

[Webster]

Hi All,

I trying out a new bullet in my Savage target rifle and am getting the best groups from a cold bore, which I’ve never seen before in any rifle. Usually, the cold bore shot is off a little and then the rifle settles down, but with Bart Avenger 68gr boat-tail bullets, the opposite is happening. The rifle is a Savage Target action with a 26" Shilen stainless select match bull barrel (0 freebore, 14” twist, ratchet groove) in 6BR Norma. I’m using a load that worked well for Bart’s 68 gr Ultra FB and Berger 68gr FB Target. The load was: Lapua cases (annealed), VV N133 29.1gr, CCI BR-4 primers, with bullet seated at jam or 0.005” back from jam.

All the shooting was done at 300 yards with very light wind and a temperature of around 34 F. All the groups were five shots. On the first day (please see Target 1), the first group from a clean, cold bore was around 0.6” ctc, which made me happy. Then the groups started to open up.
View attachment 1500730

I didn’t make much of this behavior until it happened again the next time I shot this rifle a few days later under similar conditions. The first group from a cold, fouled bore was about 1.0” ctc (please see Target 2), and then the groups started opening up. I didn’t the clean the bore before the second session since I only had 20 shots after the last cleaning and was curious to see how the rifle shot these bullets with the bore already fouled. On the second day, the bullets were at jam for the first two groups and 0.005” back from the jam for the last two groups.
View attachment 1500731


I’m wondering if the barrel is expanding slightly when warm, making the bullet fit a bit looser and causing accuracy to drop? Or maybe, the powder/cases warm up a bit in the pre-heated chamber, causing a slightly higher MV, which brings the rifle out of tune? I doubt this is the case since I’ve never seen that much sensitivity to MV in this rifle, but I’m running out of ideas. The only thing I can think of is to try some other powder weights at 300 yards.

If you have seen this before and/or have any ideas what is going on and how to fix it, please let me know.

Thanks,
John

Bench setup and technique may contribute to this?