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 2^nd 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 (12^th 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 12^nd 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 (12^th 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 2^nd 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 16^nd andSaturday August 17^th, 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 (12^th 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.