Documented results from replacing the 12 FV factory stock with an Oryx Chassis

[CFJunkie]

LuvmyLRP asked a question on the 12 FV 6.5mm Creedmoor thread about why I had been able to get 77 SMKs to shoot so well in my 12 FV .223.
I answered him on that thread but felt the answer should also be shared with you all who are interested in this thread which contains the data on the 12 FV .223 in the Oryx chassis.

Here is how I responded:


"Actually, it is hard for me to believe 77 gr bullets will even stabilize in a 1:9 twist, too!
Everything I have heard for years and years says they won't, and even Sierra says they won't, but when I tried them, I was astounded by the results.
I never expected the 77 gr SMKs or the TMKs to group at all, and they wound out shooting better than any other bullets I have shot from 50 grains to 70 grains with this rifle.
The 69 SMKs and 69 TMKs shoot well in the 12 FV .223, but the 77 SMKs and TMKs shoot even better.

Since I started shooting 77 grain bullets, my overall average improved from 0.362 to 0.320.
My average with the 77 grain SMK and TMK bullets is 0.285.
I can't explain it, I can only report the results.

However, I expect it has a lot to do with loading the 77 gr bullets out to 0.020 off the lands.
The Sierra recommended seating depth for both bullets is 2.260.
I am shooting the SMKs at 2.290 to 2.303 and the TMKs at 2.335 to 2.345 to get the best results with my chamber depth.
The TMK tips make using O.A.L. a bit more complicated because the tip adds at least 0.050 to the O.A.L.
I questioned Savage about how they came up with the 2.260 recommendation and asked it the limits of an AR magazine had anything to do with it.
The response from their rep was that the AR mag limits probably had something to do with it.

The 77 SMKs averaged 0.395 when the O.A.L. was 2.280 or less.
The same powder and bullet averaged 0.251 when the O.A.L was between 2.296 and 2.301.
The 77 TMKs averaged 0.275 when the O.A.L. was between 2.330 and 2.345.
When I moved the 77 TMK O.A.L out 2.350 to 2.353, the O.A.L was 0.330.
When I moved the O.A.L. back to 2.293, the 77 TMKs averaged 0.289.

I think finding out where to seat them makes a difference but I honestly can't explain why they even stabilize.
It is pretty clear to me that with this particular rifle, the position of the bullets re the lands is pretty important."

[CFJunkie]

I just posted the following on the wrong thread - the 6.5mm Creedmoor thread with the Oryx stock.
It actually belongs on this thread. Sorry for the confusion.

Here are more results with the Savage 12 FV .223 with the Oryx chassis using the 36X single power Sightron 1-inch tube scope with a target dot reticle. The action screws were torqued to 60 in.-lbs. prior to this session to match the Oryx chassis torque specs.

This session, held in Northern Virginia at 100 yards on Friday, Aug 2nd again tested the 77 gr TMK bullets with IMR4166 powder. Temperatures on Friday, after a very rainy early morning from about 4 AM to 7 AM, were from 73 to 75 degrees from 8 AM to 10 AM with winds from calm to 3 mph. Altitude of the range is 250 feet above sea level.

All the loads were shot using Lapua brass using Remington 7 ½ small rifle primers. All bullets were loaded to achieve a 1.361 msec. exit time (12th reflection) to stay well under Pmax using the 77 grain bullets with IMR4166 powder. The 1.361 exit time should be the sweet spot for a 26-inch 3% carbon steel barrel with a 0.040-inch recessed crown.

For this session, I loaded IMR4166 Enduron powder and 77 grain Tipped Match King #7177 bullets with the seating depths for the 77 grain bullets to achieve the a jump to the rifling – 0.030 to 0.020 – and then adjusted the seating depth by less than 0.005 thousandths to achieve the 1.361 exit time to accommodate variations in the brass trim length. As a result, all the loads are quite similar with only slight variations in seating depth and trim length.

The load description field shows the powder and charge, the O.A.L., the trim length, and the bullet exit time from the 26-inch barrel.



# Grps
Load Description
Bullet
Weight
Velocity
Average
Median
St Dev
1
2
3
4


4
IMR4166 21.0 gr 2.343 1.749 wf 1.361 * 73/73 deg. F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2539
0.244
0.258
0.050
0.174
0.248
0.267
0.288


4
IMR4166 21.0 gr 2.340 1.746 wf 1.361 * 73/72 deg. F. Rem 7 ½ Oryx 60 in-lbs.
Sierra TMK #7177
77
2539
0.210
0.217
0.020
0.180
0.216
0.225
0.218


4
IMR4166 21.0 gr 2.338 1.745 wf 1.361 * 75/74deg. F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2539
0.301
0.311
0.034
0.252
0.310
0.311
.0330


4
IMR4166 21.0 gr 2.336 1.742 wf 1.361 * 77/77 deg, F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2539
0.303
.0301
0.019
0.282
0.298
0.303
0.327


16




0.264
0.275
0.050























Today’s session started out very well, but I changed rifles after the second load and shot a CZ 527 Varmint with a 1:9 twist and the same scope model as is on the Savage 12 FV .223 Oryx. I put the 12 FV aside to cool the barrel and shot a load with the CZ. Then I switched back to the 12 FV and shot the third load and switched back to the CZ again and shot another load. Finally, I switched to the 12 FV and shot the last load.

I think the switching from the Oryx chassis to a traditional target rifle might have caused an issue getting back into position with the Oryx chassis. The results weren’t terrible but there was a definite difference between the first two loads and the last two loads.

I find that the Oryx chassis with the pistol grip takes a bit of getting used to when you switch from a normal stock. The more traditional stock on the CZ is lighter and the trigger has a heavier pull (just over 3 lbs.) than the Savage Accu-trigger that came from the factory with a pull of 1 lb. 11 oz.

The CZ 527 was also being tested using the same 77 TMK bullets but the CZ loads were tuned to match a 1.256 exit time for the 24-inch barrel.

The CZ averaged 0.302 for 8 groups with the same powder and bullets. The CZ’s first load averaged 0.288 for 4 groups and the second load averaged 0.316 for 4 groups. Not bad for a rifle with over 8,000 rounds down the barrel. The groups tracked the general loss of performance for the 12 FV Oryx chassis so it might just have been the shooter losing concentration.

[CFJunkie]

Here are more results with the Savage 12 FV .223 with the Oryx chassis using the 36X single power Sightron 1-inch tube scope with a target dot reticle. The action screws were torqued to 60 in.-lbs. prior to this session to match the Oryx chassis torque specs.
This session, held in Northern Virginia at 100 yards on Friday, Aug 12nd again tested the 77 gr TMK bullets with IMR4166 powder. Temperatures on Monday were from 85 to 90 degrees from 10 AM to 2 PM with winds from 8 to 9 mph. Altitude of the range is 250 feet above sea level.

All the loads were shot using Lapua brass using Remington 7 ½ small rifle primers. All bullets were loaded to achieve a 1.361 msec. exit time (12th reflection) to stay well under Pmax using the 77 grain bullets with IMR4166 powder. The 1.361 exit time should be the sweet spot for a 26-inch 3% carbon steel barrel with a 0.040-inch recessed crown.

For this session, I loaded IMR4166 Enduron powder and 77 grain Tipped Match King #7177 bullets with the seating depths for the 77 grain bullets to achieve the a jump to the rifling – 0.030 to 0.020 – and then adjusted the seating depth by less than 0.005 thousandths to achieve the 1.361 exit time to accommodate variations in the brass trim length. As a result, all the loads are quite similar with only slight variations in seating depth and trim length.

The load description field shows the powder and charge, the O.A.L., the trim length, and the bullet exit time from the 26-inch barrel.



# Grps
Load Description
Bullet
Weight
Velocity
Average
Median
St Dev
1
2
3
4


4
IMR4166 21.0 gr 2.342 1.749 wf 1.361 * 85/85 deg. F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2540
0.325
0.329
0.071
0.257
0.271
0.386
0.387


4
IMR4166 21.0 gr 2.339 1.746 wf 1.361 * 88/85 deg. F. Rem 7 ½ Oryx 60 in-lbs.
Sierra TMK #7177
77
2540
0.246
0.252
0.015
0.224
0.249
0.255
0.256


4
IMR4166 21.0 gr 2.337 1.744 wf 1.361 * 88/87deg. F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2540
0.273
0.268
0.038
0.236
0.249
0.286
.0321


4
IMR4166 21.0 gr 2.334 1.741 wf 1.361 * 90/90 deg, F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2540
0.274
0.284
0.031
0.231
0.272
0.296
0.298


16




0.280
0.264
0.049






















Today’s session started out poorly with two pretty large groups, but I managed to get things back together and settled down and shoot pretty consistently. I had shot the 12 FV 6.5mm Creedmoor right before switching to the 12 FV .223 so changing rifles and scopes might have had something to do with it.

I don’t believe the winds around 9 mph made much of a difference in the averages. They did change direction later in the session but initially were directly coming from behind the firing line. They moved to left to right towards the end of the session but never lost their velocity. There was some gusting but I didn’t notice much of an impact on the POI. My screw ups, not the wind, caused most of the dispersions.

The results weren’t terrible but there was a definite difference between the first two larger groups in the .380s and the rest of the session with the .223. Loads were basically all the same so I blame most of the variations on the shooter, not the conditions. I tend to have to fight to get myself to concentrate and then I concentrate less as the session wears on and I gain confidence and become complacent.

For this session, the 12 FV averaged 0.280 for 16 groups, even with the two groups in the high .380s. The last session on Aug 2nd averaged 0.364 for 16 groups and none of the groups were larger than 0.330 and no load averaged more than 0.303.


It doesn’t take much to mess up a load and session average.

[CFJunkie]

Here are more results with the Savage 12 FV .223 with theOryx chassis using the 36X single power Sightron 1-inch tube scope with atarget dot reticle. The action screwswere torqued to 60 in.-lbs. prior to this session to match the Oryx chassistorque specs.
I shot in two sessions on Friday, Aug 16nd andSaturday August 17th, both in Northern Virginia at 100 yards testingmore of the 77 gr TMK #7166 and 77 SMK #9377 bullets with IMR4166 powder. Temperatures on Friday and Saturday morningwere both 74 to 77 degrees from 8 to 10 AM with winds from 3 to 5 mph. Altitude of the range is 250 feet above sealevel. Humidity was out of sight though. Saturday morning was so foggy at 7 AM that wecouldn’t see the 100-yard line. Fortunately, the fog cleared off enough to be about to shoot when therange was opened at 8 AM.
All the loads were shot using Lapua brass using Remington 7½ small rifle primers. All bullets were loaded to achieve a 1.361 msec. exittime (12th reflection) to stay well under Pmax using the 77 grainbullets with IMR4166 powder. The 1.361exit time should be the sweet spot for a 26-inch 3% carbon steel barrel with a0.040-inch recessed crown.
Although the bullets were of two types, the loads are quitesimilar with only slight variations in seating depth and trim length to accommodatethe bullet themselves and their specific seating depths to achieve a 0.020 jump.
The load description field shows the powder and charge,the O.A.L., the trim length, and the bullet exit time from the 26-inch barrel.




# Grps


Load Description


Bullet


Weight


Velocity


Average


Median


St Dev


1


2


3


4




4
IMR4166 21.0 gr 2.340 1.747 wf 1.361 * 74/76 deg. F. Rem 7 ½ Oryx 60 in.-lbs.



Sierra TMK #7177


77


2540


0..252


0..260


0.063


0.170


0.244


0.275


0.319




4
IMR4166 21.0 gr 2.337 1.744 wf 1.361 * 77/77 deg. F. Rem 7 ½ Oryx 60 in-lbs.



Sierra TMK #7177


77


2540


0.306


0.280


0.066


0.260


0.278


0.282


0.403




4
IMR4166 21.0 gr 2.309 1.743 wf 1.361 * 80/77deg. F. Rem 7 ½ Oryx 60 in.-lbs.



Sierra SMK #9377


77


2546


0.329


0.309


0.119


0.228


0.233


0.385


0.470




4
IMR4166 21.0 gr 2.304 1.739 wf 1.361 * 83/77 deg, F. Rem 7 ½ Oryx 60 in.-lbs.



Sierra SMK #9377


77


2546


0.254


0.258


0.021


0.278


0.245


0.270


0.272




16













0.285


0.271


0.076













































The second load of TMKs were really impacted by the lastgroup of .403. Up until that group, myfirst three groups were averaging a respectable 0.273. That just shows how shooter induced variationscan ruin good data. It was my last groupon Saturday and I was trying to get it shot before a cease fire so I couldleave to go home.
The third load had an even worse group at 0.470 that startedthe day on Saturday as the fog was lifting. I don’t think the fog had anything to do with it. It was all me. But I managed to get back to consistency forthe last 6 groups with this rifle.
(R83:V83)

[charlie b]

Nice shooting. I really hate those last bullets that ruin a really nice group. Shoot 4 into an enlarged hole and then have the last one off. :(

How you you get your bullets seated that far out. Mine are at 2.28 with a .020 jump to the lands. Loaded touching the lands they are at 2.30. I have close to 2000rnds through my barrel.

[CFJunkie]

Those are base to tip O.A.L. measurements. The TMKs have pretty long tips. The SMKs are not as long and the tips aren't as far into the rifling. I have measured the chamber and set the seating depth accordingly.
When I reload, I actually measure all my loads from cartridge base to ogive so I can be sure I am creating a consistent jump.
I publish the data with the base to tip (O.A.L.) measurement to allow readers to compare with the SAAMI recommended O.A.L.

[charlie b]

Thanks. Yep, mine are tip to base, 77gn SMK's. If I set them to 2.300 I am touching the lands. I wonder if Savage started cutting .223 throats a little longer.

I know it is not a whole lot of difference, as long as the jump to lands is consistent.

[CFJunkie]

My 12 FV .223 has almost the same chamber depth as one of my range buddy's 12 FV .223.
My loads for the 77 SMKs are at 2.298 to 2.309 and the 2.309 is about 0.009 off the lands and is the deepest I have seated the bullets out.
The 77 TMKs have a longer tip, so the O.A.L.s are longer
but the cartridge base to ogive is almost the same as for the 77 SMKs.
O.A.L.s of 2.339 to 2.340 are around the 0.020 jump with the 77 TMKs and I have loaded out to a longs as 2.353 just to see if getting closer to the lands improves accuracy. It didn't. The best loads, under 0.250, are all between 2.339 and 2.343 O.A.L. The next best loads, groups around 0.260, are about 0.005 closer or further from the lands.

Our chambers really aren't that much different.
It is very possible that you have a slightly shorter chamber.
When a chamber cutting reamer wears, they would have to reset their cutting depth for the new reamer. It is possible that the reamer for your barrel was a bit shorter and they didn't adjust it enough.
Actually, your chamber is closer to SAAMI specs than ours.

I have about 1,600 rounds down my 12 FV .223 barrel, but I don't see the same rate of wear on the .223 chamber that I have seen with the 6.5mm Creedmoor after about the same number of rounds (0.036 deeper than when it was new).

[charlie b]

Yeah, they are close enough to not be unusual. I could blame it on my having an Axis instead of a 110 series, but, I understand that all the barrels are treated the same, regardless of final model they are installed on. Regardless, as long as mine shoots as well as it does the shorter throat doesn't bother me.

[CFJunkie]

I wouldn't be worried, I would consider it an extra value because it will add life to your barrel by giving you more steel to erode.

My first Savage .308 had a chamber that was 0.080 longer than SAAMI from the factory. I shot 6500 rounds and the chamber eroded by another 0.090 making me seat the bullets out longer and longer to maintain the jump. After 6,500 rounds I was seating the rounds out at 2.970 compared to the SAAMI 2.800 recommended O.A.L.
At that O.A.L. I couldn't maintain consistent neck tension and had to rebarrel. I figure that deep chamber cost me about 5000 rounds of use.
I consider consider a short chamber a gift instead of a problem.

[charlie b]

Thanks. Right now I kinda feel the same way since this barrel shoots so well.

[CFJunkie]

I tried another experiment with the Savage 12 FV .223 with the Oryx chassis using the 36X single power Sightron 1-inch tube scope with a target dot reticle. The action screws were torqued to 60 in.-lbs. prior to this session to match the Oryx chassis torque specs.

I shot in two sessions on Thursday, Aug 16nd and Saturday August 22nd in Northern Virginia at 100 yards testing 69 gr TMK #7169 and 69 SMK #1380 bullets with IMR4166 powder and Remington 7 ½ BR primers. Somewhat uniquely, the 69 grain bullets with IMR4116 powder allow a range of loads that include both the 10th and 12th reflection exit times without exceeding Pmax. The 60 and 69 grain bullets are about the only bullet weights that can manage that. The test was to try one load of each at the 10th reflection exit time (1.134 msec. around 2584 to 2590 fps) and one load of each at the 12th reflection exit time (1.361 msec. at 2954 to 2589 fps) and them compare the results. Those exit times should be the sweet spots for a 26-inch 3% carbon steel barrel with a 0.040-inch recessed crown. (Estimated pressure and exit times were obtained from QuickLOAD.)

Temperatures on Friday and Saturday morning were both 75 to 85 degrees with standard high humidity from 8 to 10:30 AM with winds from 3 to 5 mph. Altitude of the range is 250 feet above sea level.
Although the bullets were of two types, the loads at each end of the range were quite similar with only slight variations in seating depth and trim length to accommodate the bullet themselves and their specific seating depths to achieve a 0.020 jump.
Even though the muzzle velocity of the 10th reflection averaged 374 fps higher than the 12th reflection and the pressure averaged 19,588 psi higher, there were no difference in pressure signs on the primers and no difference in the feel of the bolt on extraction.

The load description field shows the powder and charge, the O.A.L., the trim length, and the bullet exit time from the 26-inch barrel.



# Grps

Load Description

Bullet

Weight

Velocity

Average

Median

St Dev

1

2

3

4



4

IMR4166 21.3 gr 2.348 1.747 wf 1.361 * 75/76 deg. F. Rem 7 ½ Oryx 60 in.-lbs. 37361 psi

Sierra TMK #7169

69

2581

0..266

0..266

0.038

0.219

0.264

0.267

0.313



4

IMR4166 24.4 gr 2.344 1.744 wf 1.134 * 79/78 deg. F. Rem 7 ½ Oryx 60 in-lbs. 57246 psi

Sierra TMK #7169

69

2954

0.323

0.333

0.093

0.211

0.285

0.381

0.416



4

IMR4166 21.7 gr 2.336 1.742 wf 1.361 * 83/82 deg. F. Rem 7 ½ Oryx 60 in.-lbs. 37456 psi

Sierra SMK #1380

69

2594

0.276

0.290

0.041

0.215

0.288

0.292

0.308



4

IMR4166 21.0 gr 2.304 1.739 wf 1.134 * 83/77 deg, F. Rem 7 ½ Oryx 60 in.-lbs. 56747 psi

Sierra SMK #1380

69

2569

0.277

0.281

0.035

0.233

0.266

0.295

0.313



16









0.285

0.287

0.056







































The second load of TMKs were really impacted by the last groups of .416. Up until that group, the first three groups were averaging a somewhat respectable 0.292. The POI for the 10th reflection loads was 4 ½ inches higher than the 12th reflection loads. I expected some change in the POI but I was really surprised it was that much for a 375-fps change in muzzle velocity. That may have broken my concentration a bit, but I don’t think it caused the two larger groups testing that particular load although it was the first 10th reflection load tested.
That again shows how shooter induced variations can ruin good data. I have no explanation for that result, other than an error by the nut behind the trigger.
Comparing the results by 10th and 12th reflection time:
I gathered the data for each reflection time so I could compare the results by reflection time.
With the 0.416 group:


Refl.

Exit Time

Average

Median

St Dev



10th

1.134

0.300

0.290

0.070



12th

1.361

0.271

0.278

0.037




Delta

0.029

0.013

0.032




Excluding the 0.416 group:


Refl.

Exit Time

Average

Median

St Dev



10th

1.134

0.283

0.285

0.056



12th

1.361

0.271

0.278

0.037




Delta

0.013

0.008

0.018















The results, with and without the single 0.416 group that bothered me so much, really didn’t show a marked difference in results for the different reflections, given that the number of groups for each reflection was only 8 (with the 0.416 group) and 7 and 8 (without the 0.416 group). The differences between the combined data for the two reflections (even when including the 0.416 group) is within the normal variation in data for almost identical loads with the same velocity and pressure the I have been reporting.

[charlie b]

Interesting results.

Have you ever overlayed (or plotted) shot groups to see what a 20round (or more) shot group would look like? I find that extremely interesting sometimes. If everything is going well and shooting is consistent the overall group size does not change much, but, it will start to show that nice bell curve distribution.

[DesertDug]

"POI for the 10th reflection loads was 4 ½ inches higher than the 12th reflection loads"- this is very surprising and I would not have expected such a change as well.

[CFJunkie]

charlie b, I have shot 25-round groups into a 0.6 inches ragged hole, multiple times, even though barrel heating dropped the POI between 1/4 to 1/2 an inch toward the end of about 7 to 8 shots. I wait for the barrel to cool a couple of times and finish the group. I even aimed slightly to the right and left so I could identify the individual groups of 8 so I could measure them too.

DesertDug, I didn't think 375 fps would have made that much difference in POI.
The first group was a 12th reflection group and it was dead on the POA.
I figured the POI would be higher for the 10th reflection so I chose a 0.7 inch diamond at the bottom of a 8 1/2 by 11 inch target I print myself.
Fortunately, there was enough room for the group to hit at a higher diamond, so I just kept the POA at the bottom and let the groups print at the top.
When I went back to shooting the 12th reflection, the next load was right at the POA, so it wasn't a scope issue.
Then I shot the next 10th reflection and the POI was right back to being high.
I guess I have to get out my ballistic calculator and see what was happening.

[charlie b]

I understand about the group size. If you took that 20 round group and broke it up into 5round groups you'd probably still have a few in the 0.3" range or less.

I would expect the POI to change a bit but the 4" does surprise me too. My ballistics table says there is less than 1" difference in drop at 100yd for a 400fps change in vel. Curious.

[CFJunkie]

I just took the data from QuickLOAD and entered it into QuickLOAD Target.
The 69 TMKs should have been 1.27 inches higher.
The 69 SMKs should have been 0.78 inches higher.

I still can't explain it but I know where I aimed and where the bullets impacted.
The 12th reflection POA was at the middle row diamond crosshair aim point and hit just about right at the middle row crosshairs for both the 69 TMKs and the 69 SMKs.
The 10th reflection POA was at the bottom row diamond crosshairs (2 5/16 lower) but hit almost at the upper row diamond crosshair aim point.

Actual measurements from the target show:
The 10th reflection for the 69 TMK's POI was 4.25 inches higher than the 12 Reflection POA at the bottom row diamond crosshair.
The 10th reflection for the 69 SMK's POI was 4.75 inches higher than the 12th reflection POA at the bottom row diamond crosshair.
The relative positions for the TMKs and SMKs is the opposite of what the ballistic calculator in QuickTarget predicted.

[charlie b]

I believe you. I've had curious POI changes in the past as well and I never figured it out. I just figured it was in my shooting, much like pistols where higher velocity bullets hit lower than low vel bullets due to the time in the barrel and recoil.

Yours is different since you have clearly shot loads with this kind of vel difference before without a huge change in POI.

[hamiltonkiler]

Again not a scientist but I am still weirded out with my real DOPE. They shoot way hotter than they could possibly be. Or the trajectory is flatter..


Sent from my iPhone using Tapatalk

[CFJunkie]

Here are more results with the Savage 12 FV .223 with the Oryx chassis using the 36X single power Sightron 1-inch tube scope with a target dot reticle. The action screws were torqued to 60 in.-lbs. prior to this session to match the Oryx chassis torque specs.

This session, held in Northern Virginia at 100 yards on Tuesday, Aug 27th at temperatures from 67 to 69 degrees from 8 AM to 10:30 AMM with winds from 3 to 5 mph with some misting rain at times. Altitude of the range is 250 feet above sea level.

All the loads were shot using Lapua brass using Remington 7 ½ small rifle primers. All bullets were loaded to achieve a 1.361 msec. exit time (12th reflection) to stay well under Pmax using the 77 grain bullets with IMR4166 powder. The 1.361 exit time should be the sweet spot for a 26-inch 3% carbon steel barrel with a 0.040-inch recessed crown.

For this session, I loaded IMR4166 Enduron powder and 77 grain Tipped Match King #7177 bullets with the seating depths for the 77 grain bullets to achieve the a jump to the rifling – 0.030 to 0.020 – and then adjusted the seating depth by less than 0.005 thousandths to achieve the 1.361 exit time to accommodate variations in the brass trim length. As a result, all the loads are quite similar with only slight variations in seating depth and trim length.

The load description field shows the powder and charge, the O.A.L., the trim length, and the bullet exit time from the 26-inch barrel.



# Grps

Load Description

Bullet

Weight

Velocity

Average

Median

St Dev

1

2

3

4



5

IMR4166 21.0 gr 2.340 1.746 wf 1.361 * 67/66 deg. F. Rem 7 ½ Oryx 60 in.-lbs.

Sierra TMK #7177

77

2539

0.207

0..174

0.055

0.161

0.167

0.174

0.250



4

IMR4166 21.0 gr 2.338 1.744 wf 1.361 * 69/68 deg. F. Rem 7 ½ Oryx 60 in-lbs.

Sierra TMK #7177

77

2539

0.238

0.236

0.068

0.163

0.202

0.269

0.316



4

IMR4166 21.0 gr 2.336 1.742 wf 1.361 * 71/69 deg. F. Rem 7 ½ Oryx 60 in.-lbs.

Sierra TMK #7177

77

2539

0.310

0.279

0.129

0.193

0.247

0.310

0.489



4

IMR4166 21.0 gr 2.333 1.739 wf 1.361 * 73/69 deg, F. Rem 7 ½ Oryx 60 in.-lbs.

Sierra TMK #7177

77

2539

0.332

0.331

0.033

0.299

0.300

0.353

0.366



17









0.268

0.264

0.049











.










For this session, the 12 FV averaged 0.268 for 17 groups. I shot a 5th group on the first load at 0.282 that somehow won’t show in the table above. That group is included in the 0.207 load average.

As you can see, there was a marked difference in performance after the second load. The range officer on duty asked me to help a new shooter with a new rifle on an adjacent lane to get his new scope on paper. After finding that his scope mounts were loose and torqueing them, I helped him get on paper and adjust his scope. I never quite got back to the same level of concentration after that. The last load was rushed trying to make up time lost so I could finish on my schedule. I think you can see what happens to my accuracy when I rush. The last group on the third load had one flyer and the entire 4th load was mediocre across the board.

It’s too bad I couldn’t maintain the concentration that I have for the first load. I was really in the groove for the first 8 groups then things started to go downhill.

Including this session, the TMK and SMK session summaries are shown below:

Date ---- Avg. --- # Grps - SMK Avg. - # Grps.
July 19 - 0.278 --- 16 ------ .240 ------ 4
July 26 – 0.280 –- 16
Aug 2 – 0.264 ---- 16
Aug 12 – 0.280 -- 16
Aug 17 – 0.279 --- 8 ------- 0.298 ----- 8
Aug 22 – 0.295 --- 8 ------- 0.276 ----- 8
Aug 27 – 0.268 -- 17
Avg. ---- 0.275 – 108 ------ 0.278 ---- 20

TMK Median was 0.273 & the SMK Median was 0.272.
Min TMK load averaged 0.263 (-0.013) - Min SMK load averaged 0.240 (-0.038)
Max TMK load averaged 0.295 (+0.019) - Min SMK load averaged 0.298 (+0.020

The two 77 grain Sierra Match King and Tipped Match King bullets are performing pretty much the same and I suspect that the variations are more due to shooter induced variations than bullet performance.

All the groups of the 77 gr TMKs and 77 Gr SMKs were shot with IMR4166 powder and those two powder-bullet combinations ranked 1 & 2 respectively out of all the powder bullet combinations shot with this rifle. I still think that it is incredible that two 77 gr bullets have the best averages when they aren’t even supposed to stabilize in the 1:9 twist barrel on this rifle.