Sierra 197gr for the 284

[Joe R]

Any updates on how this bullet went in 8.5" 284?

I can't get the Sierra 197 to shoot in my 7SAUM. But I'm not giving up. My barrel is an 8 twist and after talking to Sierra's techs, they say that in 80 degrees temp I would be OK, below 80 degrees they are uncertain. I was hoping that pushing them over 2900 would stabilize them, but looks like it's not happening. My batch of 197 shows them to have only 3-5K (bullet base to ogive) difference to the Berger 195, but the Sierra are 40-50K longer overall.

 

[Berger.Fan222]

I can't get the Sierra 197 to shoot in my 7SAUM. But I'm not giving up. My barrel is an 8 twist and after talking to Sierra's techs, they say that in 80 degrees temp I would be OK, below 80 degrees they are uncertain. I was hoping that pushing them over 2900 would stabilize them, but looks like it's not happening. My batch of 197 shows them to have only 3-5K difference to the Berger 195, but the Sierra are 40-50K longer overall.

View attachment 1004382

The bullets are clearly stable. Unstable bullets make keyholes in the paper. Round holes are THE proper indicator of stability (Sg > 1.0). I've seen bullets with marginal stability (1.0 < Sg < 1.4) shoot a lot of great groups in my life. The downsides of marginal stability are lower effective BC and possible tumbling under varying conditions.

More likely, your barrel just doesn't like the bullets in the load you are using. You might try a different powder or adjusting seating depth (the usual tricks), or you might just decide your barrel doesn't shoot that bullet well.

Sg does not just depend on velocity, twist rate, and temperature for a given bullet: it depends most strongly on atmospheric pressure. You can get away with things at low pressures (higher altitudes) that you cannot do at sea level. I've seen 69 grain bullets shot in a 1 in 12" .223 Remington. Everyone thinks that will not work, but it works well at 5000 ft.

The JBM Stability calculator is very good and incorporates all these effects.
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

 

[DocUSMCRetired]

Have you tried giving them more jump?

 

[sparker]

I can't get the Sierra 197 to shoot in my 7SAUM. But I'm not giving up. My barrel is an 8 twist and after talking to Sierra's techs, they say that in 80 degrees temp I would be OK, below 80 degrees they are uncertain. I was hoping that pushing them over 2900 would stabilize them, but looks like it's not happening. My batch of 197 shows them to have only 3-5K (bullet base to ogive) difference to the Berger 195, but the Sierra are 40-50K longer overall.

View attachment 1004382

Is the velocity for the Bergers 2866 or 2966? If the former, try the Sierras at that velocity.

 

[Joe R]

Is the velocity for the Bergers 2866 or 2966? If the former, try the Sierras at that velocity.

The Bergers are going 2,966. I know, it's a hot load. Yes, I'm planning on trying to push them to the same velocity as the Berger so I can compare apples to apples. But I'm compressing pretty hard.

Have you tried giving them more jump?

The number inside the diamond is the CBTO (Case Base To Ogive) measurement. I'm also running into the lands and I'm not sure I want it extended.

Joe

 

[sparker]

The Bergers are going 2,966. I know, it's a hot load. Yes, I'm planning on trying to push them to the same velocity as the Berger so I can compare apples to apples. But I'm compressing pretty hard.



The number inside the diamond is the CBTO (Case Base To Ogive) measurement.

Joe

My guess, the compression of the load is causing accuracy issues. Also, the 2966 value for the Bergers could be the beginning of that node. As a great many barrels 28-30" have a node that starts 2950+ and continues to 3050 or so. None of the Sierra values are in that window.

 

[Bryan Z.]

Tried them last week in a 7tw 28 inch Krieger using 4831SC at .015 jump. Groups looked good. I had no pressure signs up to 48gr so I am going to go up from there and then chrono the most accurate load

 

[Bryan Z.]

Tried them last week in a 7tw 28 inch Krieger using 4831SC at .015 jump. Groups looked good. I had no pressure signs up to 48gr so I am going to go up from there and then chrono the most accurate load

Just went up to 52.4 of RL26 with good accuracy and no pressure signs. I am planning to work up some more tomorrow and chrono the 52.2 load. Chrono data to come. I’m shooting free recoil from the bench so I have no recoil issues yet unlike my 30BR that I have to shoulder otherwise it would smack me in the face

 

[MattPeetz]

Just went up to 52.4 of RL26 with good accuracy and no pressure signs. I am planning to work up some more tomorrow and chrono the 52.2 load. Chrono data to come. I’m shooting free recoil from the bench so I have no recoil issues yet unlike my 30BR that I have to shoulder otherwise it would smack me in the face

Damn you are such a tease. Hahahahaha
So much talk of gonna chrony this and chrony that but no data. Lol

 

[Bryan Z.]

Damn you are such a tease. Hahahahaha
So much talk of gonna chrony this and chrony that but no data. Lol

Send me a lab radar and I’ll get err done! I just chrono’d the 52.2 gr of RL26 and got 2550 f/ps sd=6 with a 5 shot string. Superb accuracy and no pressure signs at all. I’m gonna work up to 53 now and just keep working up if I don’t see pressure signs. I’m thinking I can get up to 2600 but we will see. I did a WEZ analysis on drift in a 10mph 90 degree cross wind and the 2550 shows a very slight advantage (1 inch) over a 184 hybrid going 2800 but the drop is 25 inches lower on the 197SMK. Since I’m still shooting from the bench free recoil style, the recoil on the 197 is very manageable. I will test the recoil from prone at 600. Since I am in the PacificNW where we shoot from a grass bed, I expect the rear bag to go out of alignment easily from a free recoil style but we will see. I’ll also test from a shouldered style too.

 

[MattPeetz]

Send me a lab radar and I’ll get err done! I just chrono’d the 52.2 gr of RL26 and got 2550 f/ps sd=6 with a 5 shot string. Superb accuracy and no pressure signs at all. I’m gonna work up to 53 now and just keep working up if I don’t see pressure signs. I’m thinking I can get up to 2600 but we will see. I did a WEZ analysis on drift in a 10mph 90 degree cross wind and the 2550 shows a very slight advantage (1 inch) over a 184 hybrid going 2800 but the drop is 25 inches lower on the 197SMK. Since I’m still shooting from the bench free recoil style, the recoil on the 197 is very manageable. I will test the recoil from prone at 600. Since I am in the PacificNW where we shoot from a grass bed, I expect the rear bag to go out of alignment easily from a free recoil style but we will see. I’ll also test from a shouldered style too.

Just load one extra of each charge and then run those over chrony when testing is done. Run the 184’s at 2840-2900. Most are running them that fast. The 1” isn’t worth the extra work to control the gun but we are all different. Hahaha.

 

[Bryan Z.]

Just load one extra of each charge and then run those over chrony when testing is done. Run the 184’s at 2840-2900. Most are running them that fast. The 1” isn’t worth the extra work to control the gun but we are all different. Hahaha.

Good suggestion. This is my first foray into .284 Win and I started with a friend giving me 1000 of the SMK197s so the cheap side of me wants to run these until I run out. Perhaps I’ll go back to taking 100mg of Anadrol a day and bench pressing 450lbs to bulk up my chest and shoulder for the punishment? Lol! If these things are too much recoil, I’ll swiftly spend the coin and switch to the 184s.

I did work up to 54gr today with no pressure signs and I’m loaded to 56 now for the next time I hit the range. The saga continues...

 

[Bryan Z.]

Went out on a snowy day to resume load dev. Worked up to 55.6 of RL26. 55.2 looked a winner. Gonna load a few of those to chrono and keep working up since I didn’t notice signs of pressure.

 

[Bryan Z.]

Went out on a snowy day to resume load dev. Worked up to 55.6 of RL26. 55.2 looked a winner. Gonna load a few of those to chrono and keep working up since I didn’t notice signs of pressure.

So I shot 5 of the 55.2 and chrono’d them at 2702 (6). Good speed and grouping. I’m loading up to 56 right now and will report back.

 

[Bryan Z.]

I am going to go with the 55.2 load (2702 fps) given that working beyond 56 showed pressure signs. The 55.8 load did show the same accuracy as the 55.2 but was too close to the high pressure loads when I went to 56 and above. I am not sure that the little added velocity of the 55.8 load will have any significant advantage over the 55.2. I performed a ballistics analysis comparing the 55.2 load to a Berger 184 and here is what I found:

197SMK; 2702f/ps; bullet length 1.716; 7tw; G1 .780; calc spin drift; sight height 2; 59 degrees; 29.92hg; 0 humidity; 10mph 3oclock cross wind

Range Velocity Energy Trajectory TOF Drift
(yards) (fps) (ft-lb) (inches) (sec) (inches)
0 2702 3193 -2.00 0.0000 0.00
100 2585 2922 0.00 0.1135 -0.37
200 2471 2670 -3.20 0.2322 -1.53
300 2360 2436 -12.10 0.3564 -3.55
400 2252 2217 -27.25 0.4866 -6.47
500 2146 2015 -49.25 0.6230 -10.37
600 2044 1827 -78.80 0.7662 -15.30
700 1944 1654 -116.68 0.9167 -21.34
800 1848 1494 -163.76 1.0750 -28.56
900 1755 1347 -221.03 1.2416 -37.03
1000 1665 1213 -289.59 1.4171 -46.84

Berger 184; 2850f/ps; bullet length 1.575; 9tw; G1 .695; calc spin drift; sight height 2; 59 degrees; 29.92hg; 0 humidity; 10mph 3oclock cross wind

Range Velocity Energy Trajectory TOF Drift
(yards) (fps) (ft-lb) (inches) (sec) (inches)
0 2850 3318 -2.00 0.0000 0.00
100 2714 3010 -0.00 0.1078 -0.40
200 2583 2725 -2.72 0.2211 -1.67
300 2455 2463 -10.65 0.3403 -3.87
400 2331 2220 -24.36 0.4656 -7.07
500 2211 1997 -44.46 0.5978 -11.35
600 2094 1791 -71.68 0.7372 -16.78
700 1981 1603 -106.83 0.8845 -23.46
800 1872 1431 -150.85 1.0403 -31.47
900 1766 1275 -204.81 1.2053 -40.92
1000 1666 1133 -269.91 1.3802 -51.92

 

[rogina]

So I shot 5 of the 55.2 and chrono’d them at 2702 (6). Good speed and grouping. I’m loading up to 56 right now and will report back.

I am shooting a 284 with a 28 inch barrel, r26 powder, cci200 primers, 180 grain sierras. I can shoot 2.00 inch groups at 1000 yards. I am shooting at 1800 yards now with groups that have only 4 to 5 inches of windage but 12 to 24 inches of vertical. What can I do to get rid of some of this vertical?

 

[Bryan Z.]

I am shooting a 284 with a 28 inch barrel, r26 powder, cci200 primers, 180 grain sierras. I can shoot 2.00 inch groups at 1000 yards. I am shooting at 1800 yards now with groups that have only 4 to 5 inches of windage but 12 to 24 inches of vertical. What can I do to get rid of some of this vertical?

The two strategies I take are:
1. Chrono and check my standard deviation and extreme spread. If one or both are high, then find a load that reduces them to a low single digit; and/or
2. Vary the charge weight. If it’s a mild to moderate load, go up a little in increments until the vertical reduces to an acceptable level. If it’s a hot load, consider dropping the charge and testing.
These are two things I do to reduce vertical. I would check with others though because they may have some great words of wisdom.

 

[JFrank]

I am shooting a 284 with a 28 inch barrel, r26 powder, cci200 primers, 180 grain sierras. I can shoot 2.00 inch groups at 1000 yards. I am shooting at 1800 yards now with groups that have only 4 to 5 inches of windage but 12 to 24 inches of vertical. What can I do to get rid of some of this vertical?

Hells Bell’s
I want to hear more about these Thousand yard 2 inch groups ?

 

[rogina]

Hells Bell’s
I want to hear more about these Thousand yard 2 inch groups ?

I shot two. One was a 4 shot and one was a 3 shot. I haven't shot this rifle much at 1000 yards to save barrel. I built this rifle to shoot 2000 yards. I shot at 2000 yards yesterday. One 3 shot group was 17 inches and one was 20 inches. I was very happy. I had the bad verticle at 1800 yards and I think most of it was from the conditions. I was shooting in a 8 0'clock wind of about 3 to 5 mph.

 

[rogina]

The two strategies I take are:
1. Chrono and check my standard deviation and extreme spread. If one or both are high, then find a load that reduces them to a low single digit; and/or
2. Vary the charge weight. If it’s a mild to moderate load, go up a little in increments until the vertical reduces to an acceptable level. If it’s a hot load, consider dropping the charge and testing.
These are two things I do to reduce vertical. I would check with others though because they may have some great words of wisdom.

Thanks.