Inconsistent Velocity

[dnb86]

wouldn't hurt to try a new OCW test with the new brass and then try a seating depth test or even change primers if you dare to venture down that road

 

[RockZ]

Do what Bob said.. then do a seating test to dial it in!

 

[Salmonhead]

I've had two Caldwell chronographs and they varried wildly. Id use them simultaneously and consistently get about 70fps less from one of them. They were really bad when the sun was lower in the evening or if it was partly cloudy. Readings all over the place with known loads.

I've also had poor results with winchester brass on at least three occasions with different chamberings. If the fire formed brass doesn't start behaving, I would switch to adg or Peterson.

I also wouldn't be messing with 5/8" results from a stock Tikka barrel thats 10 years old. I'm my opinion, to drop that group, you'll need a new custom barrel.

I also think your charge weight is several grains light. But if you're happy with 2700, it won't hurt anything. You're leaving an easy 250 to 300 fps on the table if you feel you could use the velocity.

 

[Lefty7mmstw]

The Tikka rifles don't seem to be too fast in 7 rem. The one my kid shoots is running 3,000 fps with a 140 Sierra pro hunter and 68 rl22 in ww brass lit by a 215. However, the accuracy is there and the uniformity is usually in the 20's for x..
I suspect a powder switch may be in order, but h4831 sc is usually rather good at being lit with a 215, albeit a bit slow vel. wise. If you could snag a # of 560 or 565 you might get an improvement, but that's just a guess. I've run 4831 sc vs. mil. surp h4831 in my old 300win and she dumped 150 fps (vs the old powder) when pressured out with a 180. I switched to 7828 and got most of my vel. back.

 

[BlazerBeam]

Was the barrel clean when you started shooting? That velocity string looks like a clean barrel getting fouled in.

 

[Horse1]

Was the barrel clean when you started shooting? That velocity string looks like a clean barrel getting fouled in.

That was my 1st thought as well. Also as mentioned earlier, virgin brass is unlikely to yield consistently low ES/SD.

 

[geraldhawaii]

KH Outdoors, Thank you for the advice. Although I've had the rifle for some time, I estimate only about 300 - 350 rounds went through it. I only use it for hunting. Had good luck at the beginning on finding the load, so not very many bullets were used to develop the load. Everytime, I changed scope or remounted a scope, it would shoot 5/8 inch groups with the same load. Only tinkered with a few other bullet heads, and couldn't get the same accuracy, only 1 inch groups at 100 yards. I just shot my old loads though it yesterday, and a 3 shot group at 100 yards was 3/8 inch with a dirty barrel. Shot it after hunting the whole day, and put down 3 deer with the old loads, all one shot kills, at 60 yards, 100 yards, and 75 yards. So it can't be the rifle, just my inexperience with trying new loads.
Again, I really appreciate everyone sharing their knowledge and personal experience. I usally follow manual loads, and don't deviate much from the manual.

 

[geraldhawaii]

Salmonhead, yes, my Caldwell always has error readings or show velocities that I know are totally wrong when there is a heavy overcast.
I appreciate all of the advice.
Aloha!!!

 

[Full time hunter]

I had a Caldwell also. Same results. Constantly inconsistent readings or no reading at all. I gave it away and bought a Magnetospeed. Inconsistent problems gone. I get readings every time now. The guy I gave it to hated it also.

 

[baldhunter]

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• #17

I've had two Caldwell chronographs and they varried wildly. Id use them simultaneously and consistently get about 70fps less from one of them. They were really bad when the sun was lower in the evening or if it was partly cloudy. Readings all over the place with known loads.

I have experienced this issue as well with other chronographs.It's how the chronograph sees the bullet as it crosses over two eyes.Just a fraction of difference can really change the velocity difference.I've had better consistency reading shooting downrange in a North or South direction as opposed to shooting in an East or West direction,especially in early and late shooting.It drove me crazy until I figured this out.I bought a Magneto after that if I want to check velocities.I found the Magneto speed can affect your group size,so if I want to check groups and velocity at the same time,I use my ProChrono and verify my velocity reading with the Magneto speed.I have two places I can shoot at my range.One is shooting towards the East.I only use my Magneto speed there.With my ProChrono,if I shoot there early in the morning,I've seen as much as a 100fps difference in just one hour with the same rifle and load due to the sun casting a shadow across the eyes on the chronograph.I can go the the other range where I'm shooting towards the North and the velocities don't change because the sun rays are shining across the side of the chronograph so the eyes can see the bullet equally and are comparable with the Magneto speed.

 

[VinceMule]

I have shot Rem brass forever with fantastic accuracy in my 7 Mags, and have New Win to load when my Rem runs out. Primer pockets do not hold up as well in the Remington, but these are hunting rifles, not target rifles.

I run warm loads in all my 7 Rem mags, and this is where the best accuracy is of 3/8" and smaller groups at 100 yards. Even in new brass, the groups are small, but I am aware that there may be a flyer out of the group, 3/8".

OP, your load is light, and this worries me on fire-forming brass. Fire forming with minimal loads can lead to excessive case stretching. I am not saying that you are getting excessive case stretching with your load, but I would use a 35-caliber ogive gauge on your caliper and measure the headspace length from the base of the case to the shoulder to see if you are getting erratic results.

I hope you take Bob Wright's post to heart, he is spot on.

Tikkas have some long freebore, and this is a good and bad thing. You can run some higher pressures as the long leade drops pressures around 5000 cup, but you will have to up your charge. The standard freebore length in SAAMi spec chambers is .110 which is fairly short, but I can not say what CIP European spec is for the Tikka.

Your 160g should be running around 2950-3050, but every barrel is different.
I run these loads in Remington 700's with 160g:
61g of H4350, work up to this load with Rem 9 1/2 primers in Rem brass
65g of R#22, This is a warm load in Rem and use cci 250 in Rem brass
68g of R#25 with a Winchester Mag primer, work up to this load
71g of Retumbo with a fed 215, work up to this load

Fire forming the new Winchester brass, run it through a neck sizer, put a heavy chamfer on the inside of the case mouth, de-burr the outside, and work up a load. The process used for long-range shooting would involve fire forming your brass, but for 300-yard and under hunting, this would not be necessary. That Winchester brass will take some pressure.

I found that full-length sizing on every firing in the 7 Mag ALWAYS produced the best accuracy.

Those Light Weight Tikka's in 7 Mag has some recoil, and I would have a Gentry muzzle break put on the barrel before I ever pulled the trigger, reducing recoil to 243 Win levels.

The best accuracy will not be far off from what is the Max load for the rifle. For deer, some in my family shoot a lot of the Sierra 160g BTSP which is one heck of a short range(350 yd and under) deer bullet from all angles. The Sierra 160g HP Game King is one heck of a tough bullet, 160g Partitions are for elk.

OP, I hope this helps.

 

[xsn10s]

What's the max distance for hunting with this rifle?

 

[geraldhawaii]

Baldhunter, yep, that is why I'm looking to purchase a magneto, when they become available. Vincemule, the load I am currently using is from an old Nosler reloading book, and at that time, I believe was the max load. Thank you for the load info. XSN10s, I've shot deer and goats at just under 400 yards with this load and rifle. Don't plan to shoot much further than that with this rifle. Again, thank you all for the info, I always appreciate new knowledge and advice.
Aloha!!!

 

[xsn10s]

XSN10s, I've shot deer and goats at just under 400 yards with this load and rifle. Don't plan to shoot much further than that with this rifle.

Honestly at those distances I'd shoot out to 400 yards, maybe 500 yards and see how it groups. Then you'll know what you're dealing with.