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7mm 197g SMK

Have very limited testing so far but much more to come. A friends 28 Nosler with approximate 0.005" jam and 85.0 gr RL 33 and CCI 250. 1:8.3 twist and 28" Bartlein. Approximately 3100 fps. 4 out of 5 shots were 1.5" at 500 yards. Wasn't sure where shot #5 went due to off target and other bullet holes. Showed a lot of promise for first group. I shoot a 28 Yukon (28 Nosler with shoulder pushed back for a .340" neck) 30" 1:8.3 twist Bartlein. 84 gr RL 33 and CCI 250 and 0.005" jam gave approximately 3100 fps also. Shot 4 shot group around 1.5" and the 5 shot group was 2.5". First group with this bullet and gun combo also. Will try to get to the 3150 fps accuracy node and different seating depths. Believe it will do well with tuning.
 
Yote Hunter said:
Have very limited testing so far but much more to come. A friends 28 Nosler with approximate 0.005" jam and 85.0 gr RL 33 and CCI 250. 1:8.3 twist and 28" Bartlein. Approximately 3100 fps. 4 out of 5 shots were 1.5" at 500 yards. Wasn't sure where shot #5 went due to off target and other bullet holes. Showed a lot of promise for first group. I shoot a 28 Yukon (28 Nosler with shoulder pushed back for a .340" neck) 30" 1:8.3 twist Bartlein. 84 gr RL 33 and CCI 250 and 0.005" jam gave approximately 3100 fps also. Shot 4 shot group around 1.5" and the 5 shot group was 2.5". First group with this bullet and gun combo also. Will try to get to the 3150 fps accuracy node and different seating depths. Believe it will do well with tuning.
Click to expand...
Yote, - Do you think that I'll be able to run the 197 gr in a 28 Nosler with a 1-8.5 twist ? - I have 2 barrels both throated for the 195 Berger and the barrels are 34" in length. - Plan will be to try to use RL-33
Thanks, Ron
 
LA50SHOOTER, There should not be a stability issue with an 8.5" twist. I use an 8.3" as stated. At my elevation and a speed of 3100 fps and elevation of 700' at 70 degree temperature an 8.5" twist Has full stability according to the Berger twist rate calculator. The 197 gr Sierra Matchking has an OAL of 1.667". Use the Berger Twist rate calculator using your elevation and temperature that you intend on shooting in and see if you get a full SG # of 1.5. If not it shows how much your BC is compromised. A stability in the high 1.4xx range is still pretty good.
 
Thanks Yote Hunter. Glad to know that 5 in worked for you for seating depth.

Anyone else trying out this bullet have any input?
 
The reason why I was using 0.005" jam is so I could do a very mild fire form and get headspace correct. Just appeared to work pretty good. Will be trying that again, as well as, 0.010-0.030" jump.
 
Wade I tried the 197,s and the 195,s and could not get them to shoot well enough to take to a match. I tried them in a 8.75 twist and a 8.25 . Regards Ralph
 
Sierra does recommend a 1;75 twist for this bullet. Are they just being overly conservative?
 
Joe R said:
BBTO = Bullet Base To Ogive. I sort my bullets that way.
Lands = Using a Hornady OAL gauge I measure where the bullet touches the lands.
Lands - CBTO = Jump 2.359-2.347= .012
Bore Polished = How many rounds through the barrel when I polished the bore last with Iosso

The number inside the diamond refers to grains of powder. The numbers next to the diamond refer to:
  1. Average muzzle velocity
  2. Standard Deviation
  3. Extreme Spread
  4. Number of Rounds

So for the second target I used 63.0 grains of H-1000 and they had an average muzzle velocity of 2890 fps, standard deviation of 11.5 fps, an extreme spread of 28 fps and I fired 5 rounds on that target.
Click to expand...

Sorry Joe, what caliber is this for, 7RSAUM?
 
Appreciate the clarification. I cogitated on your post for a while but just couldn’t decipher the numbers on my own. Glad I ask because this is useful information.

Hope all is well for you in the Houston, TX area.

Ken
 
Joe and others, if you have shot 180s in the same barrels that you are shooting 197s, how much have you had to drop your load to avoid pressure?

Looking at some calculators, it appears that 1.5-2g should be safe/normal.

Thoughts?
 
Joe R said:
kyreloader,
No, I haven't shot the 180 hybrids in the same barrel that I've used the B195s and S197s. You have to have a lot of freebore to shoot those two bullets and that make's it difficult to shoot the 180s because they would have to jump a whole lot. I don't have much experience with jumping more than .020+ so I'm reluctant to deal with it.

Joe
Click to expand...

Joe, asking the question a different way, your target above is shooting between 62 and 65g of powder, any idea what the same test would be with your 7RSAUM if you were shooting it with the 180g class bullet (irrespective of the freebore and set up)? So you will likely settle between 63-64g of powder with the 197s, any idea where most settle with same powder shooting the 180s?
 
Ackley Kid said:
Thank you kyreloader , what kind of velocity do you get from 284 before you see pressure ?
Click to expand...

AK,

Too early to tell to me honest. I only have 34 rounds down this new barrel (Krieger 1:8 twist). I have gone up to 54.9g of RL26 for 2730 fps without pressure. I have a ladder loaded with H4831SC, but presume it will be much slower. Concerned that if this barrel speeds up like most, I will be closer to 2800 fps with same load. Quickload predicted max powder load based on my current Fclass load is max of 55g at 61K with RL26.

The barrel is still slow though, I shot my 180g load with H4350 that I shoot in my current Fclass rifle (30", 1:9 Brux) that averages 2820 fps and this barrel with the same load averaged 2755 fps (51.1g). (Distance to lands is the same in both rifles).

If I can get a good load at 2700 fps with the 197s, the ballistics of this bullet is better than my current load of pointed Berger Hybrids at 2820 fps (only by 1 inch of wind at 1000 yards in 10 mph wind). Could really argue that the difference is not big enough to be chasing it, but I just think of all of the barely 4s (9s in US) that I had in Canada at the FC Worlds. I was 5 points out of 20th place during the Worlds and wonder how many of those I could have saved with 1 inch.

Sorry to derail your question.
 
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