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

[CFJunkie]

I figured that you all might like to see the results of changing a Savage plastic stock to an Oryx chassis.
After finally getting rings that would get the Sightron scope high enough to be able to get a cheek weld on the straight (no drop) rear stock on the Oryx, I took it to the range this morning to see whether the cost of the stock change and the rings would pay off in accuracy.
I had two objectives in changing the stock on a Savage 12 FV .223 that cost $ 320 at Cabela’s. It shot pretty well out of the box as you can tell in my thread that documented its performance since mid-March of this year at http://www.savageshooters.com/showthread.php?63914-First-results-with-new-12-FV-223. The rifle has a Sightron 36X target scope with a 1/8 MOA target dot reticle mounted on it



The hidden magazine with the magazine shortened to keep the .223 rounds forward in the mag so they would feed was difficult for me to load easily. I wanted a detachable magazine so I didn’t have to struggle with loading, especially with arthritic fingers.
The factory plastic stock has no aluminum bedding posts and no aluminum rail to stiffen it so it tends to flex. While the .223 has minimal recoil, I could still feel the stock flexing.


I purchased an Oryx stock, with a .223 AICS polymer magazine and extra spacers for the rear pad because I have long arms and adjustable stocks have proven valuable in getting the right fit. I also purchased a front sling swivel to mount my Sinclair F-Class bipod. Total cost, including shipping was 488.96.

The following are the results with the Savage 12 .223 with the new stock, shot in Northern Virginia on Wednesday morning, July 3nd at 100 yards. Temperatures were from 74 to 86 degrees with winds from calm to 3 mph. Altitude of the range is 250 feet above sea level.

All rounds were shot using Lapua brass and CCI BR-4 primers with an 36x42mm Sightron fixed magnification target scope with a target dot reticle. All bullets were loaded to achieve a 1.360 msec. exit time which should be the sweet spot for a 26-inch 3% carbon steel barrel with a 0.040-inch recessed crown. The action screws were torqued to 60 in.-lbs. per the Oryx directions prior to this session.
For this session, I loaded IMR4166 Enduron powder and I planned the seating depths so all the different bullets would achieve the same jump to the rifling – 0.020 – and then adjusted the seating depth by less than 0.005 thousandths to achieve the 1.360 exit time.

Over the last two sessions with the 12 FV with the factory barrel, I tested its accuracy with 77 grain Sierra SMK and TMK bullets with two different primers at different sessions. Today I not only wanted to see if the new chassis would perform, but I decided to also test the performance of primers on the same day with the same loads to see if there was a measurable difference.

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 21.1 gr 2.301 1.757 wf 1.360 * 74/77 deg. F. 35 in.-lbs. CCI BR-4

Sierra SMK #9377

77

2543

0.237

0.238

0.014

0.220

0.237

0.239

0.253



3

IMR4166 21.1 gr 2.300 1.755 wf 1.360 * 82/80 deg. F. 35 in.-lbs. Rem 7.5 BR

Sierra SMK #9377

77

2543

0.254

0.258

0.021

0.245

0.258

0.272





4

IMR4166 21.0 gr 2.345 1.783 wf 1.360 * 85/84 deg. F. 35 in.-lbs. CCI BR-4

Sierra TMK #7177

77

2540

0.276

0.290

0.041

0.215

0.288

0.292

0.308



4

IMR4166 21.0 gr 2.345 1.783 wf 1.360 * 85/84 deg. F. 35 in.-lbs. Rem 7.5 BR

Sierra TMK #7177

77

2540

.270

.257

.052

0.223

0.247

0.267

0.343



15









0.260

0.253

0.0035







































Comparison of Factory Stock with Oryx Chassis with Equivalent Bullets



















Factory







Oryx Chassis







Bullets

Avg.

Median

St Dev

# Grps.

Avg.

Median

St Dev

# Grps.



Sierra Match King # 9377

0.344

0.327

0.118

11

0.256

0.258

0.017

7



Sierra Tipped Match King #7177

0.280

0.274

0.043

12

0.273

0.278

0.044

8




Comment: The earliest sessions with the 77 SMK bullets were somewhat of an anomaly because the initial tests with the heavy bullets were at the Sierra recommended O.A.L. Later loads were loaded out so the jump was around 0.020 and the performance improved immensely.

Other than the initial results with the SMK bullets in the factory stock, the results for the 77 TMK bullets, which were seated out to minimize the jump from the outset, don’t show any statistically significant performance improvements with the Oryx chassis. However, shooting with the Oryx chassis did provide a feeling of set-up consistency and absolutely no stock flexing. But regardless of feeling more stable, the results didn’t show significant improvement in accuracy.

[celltech]

And the Oryx looks a lot cooler...

[CFJunkie]

I figured you would like to see the finished swap.

6185
The 12 FV .223 with the Oryx chassis is in the foreground.
A 12 FV 6.5mm Creedmoor with the factory chassis is in the background.
Except for the scope and the caliber of the bore, the two rifles looked identical when they came from the factory.

Here is a closer look at the Sinclair Gen 3 F-Class bipod that is attached to the Oryx sling swivel (extra) and the Protektor rear bag that I use as my load testing set up.
6186

[CFJunkie]

celltech

'Looking cool' and being over $ 550 more expensive (considering the extra high rings for the scope) didn't make the groups any smaller.
It all depends upon what matters to the shooter.

[celltech]

Guess I should have put a funny emoji after my comment :cool: While not the prettiest things in the world I have no doubt the factory stock can be capable of great things...I just personally never liked them. I have a pair of Oryx on 12FVs in .223 and .243 and I *love* them. Getting the external mag alone was worth the price.

6187

At least you can be reasonably sure it's not the stock introducing issues into your setup. Happy Shooting...

[CFJunkie]

I agree that the detachable magazine is a great improvement over trying to fit 2.300 and 2.340 O.A.L. rounds with 77 grain bullets into the hidden magazine with a 1/2 inch flange on the bolt that shortens the space in the ejection port and squeezing the round under a scope.
Having a detachable mag to load is a great improvement for the .223 and the mag has room for up to 2.500 O.A.L.
Actually, the 6.5mm Creedmoor is easier to load even though the scope on its mount has a 30mm tube and the rounds are up to 2.860 O.A.L. Not having that bolt flange gives just enough room to load the rounds easily, at least for me.
I am going to switch the Oryx to the 6.5 Creedmoor next week to see if the added stiffness helps with the larger caliber, assuming the NightForce scope with the high rings is high enough to let me shoot with the cheek piece at its lowest position.
If it does, I might get another Oryx chassis for it.

[varget204]

Just curious,what is reason for bipod being backward ?.Would imagine all groups will get better,the more you get used to shooting chassis.Also wanted to thank you,saw your earlier posts of groups you shot w/ the Sinclair F-class bipod,so i bought one for my 6 creedmoor,like it better than my Harris BRM's

[CFJunkie]

varget204,

Glad you like your F-class bipod and that you are getting such great results with your 12 FV 6.5mm Creedmoor.

As you an probably see, both my F Class bipods have the azimuth adjuster and it is easier to get at if the adjustment lever to level the stock in the bipod is toward the front.
You probably can see that I have a level on the scope to make sure my rifle isn't canted. I use that to level the stock when I put on the bipod and never touch the level adjustment again.
But I often adjust the azimuth all during a session, so I like to be able to get at the adjuster while I am looking through the scope.
I thought that is the way the bipod was designed to be used, but what do I know.


I don't think there is a front and back to the F-Class bipod, unlike a folding bipod like a Harris that could fold up on you if mounted the wrong way when you did the forward pressure move to keep the bipod from hopping.

[david12601]

I too bought the oryx.....my new build in 6x47 lapua had a 1 piece med height dednutz mount. .......it is way too low for me to use the headrest the way it is supposed too ......what height rings did you go with if you have some height measurements that would help a lot. Thanks

[CFJunkie]

Switched the Oryx to the 6.5mm Creedmoor with the 8-32x56 NightForce 30mm tube scope with high rings.
I can get a comfortable cheek weld with the cheek piece abut 1/2 inch off the minimum setting. It looks like high rings would work with your scope if it has a 30mm tube.
It might even work with high rings with a 1-inch scope like the Sightron II but I didn't want to chance it. If you have them, try them.

Hopefully I can try the Oryx chassis at the range tomorrow when am RSO if there are no other shooters present. It is supposed rain about mid-day when I take over the range so I might be in luck.
Otherwise, I'll try it on Tuesday morning.

[PaddyD]

My experience with plastic stocks has been terrible. Back around 1994 or so I bought a new 110FP in 308W. Out of the box that thing just wouldn't shoot. It really struggled to get under 2moa. Some epoxy bedding helped a little, but not much. Then I went out and bought an inexpensive Choate Varminter stock with aluminum bedding and she now shoots .3" on average and has shot down into the low 2's with 175 SMK and IMR4064. I haven't examined the newer plastics, but I can assure you the older ones were/are pure junk.

[CFJunkie]

PaddyD,

Good to hear from you again.

I had an old 2008 vintage plastic Savage factory stock that came on my first Savage, a .308, that shot well enough to convince my son and several shooting buddies to buy Savages.
I have no experience with Savage plastic stocks before that one.
That was before Savage started selling the Accu-stock, or right about when the Accu-stock was introduced. After that first plastic stock, I chose the Accu-stock or special stock versions for my Savages (I have an HS Precision stock on my 12 LRP) until I bought the two bargain 12 FVs with plastic stocks from Cabela's.

The last two plastic stocks were good enough to average in the mid 0.3s but I did feel them flex, especially the 6.5mm Creedmoor. I did notice that 6.5mm stock needed the action screws torqued to 35 in.-lbs. before each session to maintain accuracy. The other, in .223, shot with about the same accuracy without messing with the action screws, perhaps because of the lighter recoil.

[CFJunkie]

More data from the 12 FV .223 mounted on an Oryx chassis.
The following are the results shot in Northern Virginia on Tuesday morning, July 9th at 100 yards. Temperatures were from 73 to 76 degrees with winds from calm to 3 mph. Altitude of the range is 250 feet above sea level.

All rounds were shot using Lapua brass and Remington 7.5 bench rest primers with an 36x42mm Sightron fixed magnification target scope with a target dot reticle. This session I concentrated on 69 grain Sierra SMK and TMK bullets. Each type bullet was loaded to achieve a 1.360 msec. exit time which is the 12th reflection at the chamber and to achieve a 1.133 exit time which is the 10th reflection at the chamber. Either should be the sweet spot for a 26-inch 3% carbon steel barrel with a 0.040-inch recessed crown. The action screws were torqued to 60 in.-lbs. per the Oryx directions prior to this session.
For this session, I loaded IMR4166 Enduron powder and I planned the seating depths so all the different bullets would achieve the same jump to the rifling – 0.020 – and then adjusted the seating depth by less than 0.005 thousandths to achieve each desired exit time.
Both the 10th reflection loads were around 57,200 psi so I was extra careful to watch for pressure signs. Both the 12th reflection loads were around 37, 800 psi so I was obviously not concerned with high pressure.
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 21.4 gr 2.280 1.751 wf 1.359 * 73/74 deg. F. 60 in.-lbs. Oryx Rem 7.5 BR
Sierra SMK #1380
69
2586
0.262
0.251
0.060
0.200
0.235
0.268
0.345


3
IMR4166 24.5 gr 2.274 1.746 wf 1.133 * 77/76 deg. F. 60 in.-lbs. Oryx Rem 7.5 BR
Sierra SMK #1380
69
2958
0.367
0.305
0.117
0.295
0.305
0.502



4
IMR4166 21.2 gr 2.330 1.752 wf 1.359 * 70/68 deg. F. 60 in.-lbs. Oryx Rem 7.5 BR
Sierra TMK #7169
69
2578
0.248
0.269
0.050
0.174
0.266
0.272
0.280


3
IMR4166 24.3 gr 2.330 1.749 wf 1.133 * 76/75 deg. F. 60 in.-lbs. Oryx Rem 7.5 BR
Sierra TMK #7169
69
2955
.271
.272
.010
0.261
0.272
0.281



14




0.283
0.272
0.076





















There were no difference in pressure indications between the 12th reflection and 10th reflection loads so my pressure concerns were premature.



Comparison of Factory Stock with Oryx Chassis with Equivalent Bullets










Factory



Oryx Chassis




Bullets
Avg.
Median
St Dev
# Grps.
Avg.
Median
St Dev
# Grps.


Sierra Match King # 1380
0.329
0.303
0.087
10
0.307
0.295
0.098
7


Sierra Tipped Match King #7169
0.304
0.288
0.061
12
0.258
0.272
0.038
7



Comment: The 10th reflection test with the SMK bullets had one bad group that was shooter induced. The other two groups averaged 0.300 which was more indicative.
Both the 10th and 12th reflection tests with the TMKs and the 12th reflection test with the SMKs were very consistent and probably represents what that both bullets will do.

[CFJunkie]

Here are the results of another session with the 12 FV .223 mounted in 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 meet the Oryx chassis torque specs.

The session took place in Northern Virginia on Monday morning, July 14 at 100 yards. Temperatures on Monday were from 74 to 79 degrees with winds from 2 to 4 mph. Altitude of the range is 250 feet above sea level.

All the loads were shot using Lapua brass with Remington 7 ½ small rifle primers. All bullets were loaded to achieve a 1.359 to 1.360 msec. exit time (12th reflection) to stay under Pmax using the 77 grain bullets with IMR4166 powder.
The 1.359 to 1.360 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 I planned the seating depths for three of the four the 77 grain bullets to achieve the a jump to the rifling – 0.020 – and then adjusted the seating depth by less than 0.005 thousandths to achieve the 1.359 to 1.360 exit time to accommodate variations in the brass trim length.

For one load with the TMK bullets, load 3 of the 4 shown, as an experiment, I set the jump back to 0.067 for the TMK bullets to see what effect it had on group size. The other two TMK loads have jumps from 0.023 to 0.018. That load has the largest load average of 0.289.

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 21.1 gr 2.296 1.752 wf 1.360 * 71/74 deg. F. Oryx 60 in.-lbs.
Sierra SMK #9377
77
2544
0.240
0.238
0.007
0.233
0.238
0.238
0.250


4
IMR4166 21.0 gr 2.340 1.750 wf 1.359 * 74/75 deg. F. Oryx 60 in-lbs.
Sierra TMK #7177
77
2541
0.240
0.253
0.067
0.147
0.242
0.264
0.306


4
IMR4166 21.1 gr 2.293 1.748 wf 1.360 * 77/77 deg. F. Oryx 60 in.-lbs.
Sierra TMK #7177
77
2543
0.289
0.290
.0042
0.242
0.264
0.316
0.332


3
IMR4166 21.0 gr 2.335 1.745 wf 1.360 * 79/79 deg, F. Oryx 60 in.-lbs.
Sierra TMK #7177
77
2541
0.261

0.295

0.067

.0183

0.295

.0304



15




0.257
0.250
0.050


























Previous results with Sierra 77 gr SMK #9377 bullets with IMR4166 powder and Rem 7 ½ primers averaged 0.256 for 7 groups. Today’s results with the same bullet, powder and primer averaged 0.240 for 4 groups.
Previous results with Sierra 77 gr TMK #7177 bullets with IMR4166 powder and Remington 7 ½ primers averaged 0.273 for 8 groups. Today’s results with the same bullet, powder, primer averaged 0.263 for 11 groups.

Here are comparisons of the performance with Savage factory plastic stock versus the Oryx chassis

Comparison of 12 FV .223 Factory Stock with Oryx Chassis
--------------------------------------Savage Factory Plastic ----------------- Oryx Chassis
-------Bullets ---------------------- Avg. - Median St Dev # Grps. - Avg.-- Median - St Dev # Grps. -- Delta % Improv.
Sierra Match King # 1380 ------- 0.329 - 0.303 - 0.087 -- 10 ---0.307 - 0.295 -- 0.098 ----- 7 ----- 0.022 -- 6.7%
Sierra Tipped Match King #7169 0.304 - 0.288 - 0.061 -- 12 --- 0.258 - 0.272 -- 0.038 ----- 7 ----- 0.046 -- 15.2%
Sierra Match King # 9377 ------- 0.344 - 0.327 - 0.118 -- 11 --- 0.250 - 0.245 -- 0.016 ---- 11 ---- 0.094 -- 27.3%
Sierra Tipped Match King #7177 0.280 - 0.274 - 0.043 -- 12 --- 0.267 - 0.267 -- 0.051 ---- 19 ----- 0.012 -- 4.4%
------------------------------------ 0.313 - 0.289 - 0.082 -- 45 --- 0.269 - 0.267 -- 0.055 ---- 33 ----- 0.044 -- 13.9% w Oryx

Comparison of 12 FV .223 with CCI BR-4 versus Remington 7 1/2 Primers - equivalent Jump
----------------------------------------CCI BR-4 primers -----------------Remington 7 1/2 Primers
------------Bullets ------------------- Avg. Median St Dev # Grps. -----Avg. Median St Dev # Grps. Delta % Improv.
Sierra Match King # 1380--------- 0.399 0.422 - 0.078 -- 3 -------0.303 - 0.287 0.084 --- 14 -- 0.096 -- 24.2%
Sierra Tipped Match King #7169 0.354 0.339 -- 0.065 --- 5 -------0.264 - 0.272 0.030 -- 14 --- 0.090 -- 25.5%
Sierra Match King # 9377 --------0.352 0.287 -- 0.140 --- 8 -------0.265 - 0.250 0.038 -- 15 -- 0.087 -- 24.7%
Sierra Tipped Match King #7177 0.278 0.290 -- 0.044 --- 8 -------0.270 -- 0.267 0.050 -- 23 -- 0.007 --- 2.7%
-------------------------------------0.333 0.308 -- 0.098 -- 24 ------0.274 -- 0.270 0.055 --- 66 -- 0.059 -- 17.7% w Rem 7.5

[CFJunkie]

Here are the latest 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 meet the Oryx chassis torque specs.
The session took place in Northern Virginia on Friday morning, July 19 at 100 yards. Temperatures on Friday were typical for a Virginia summer ranging from 79 to 91 degrees from 8 AM to 11 AM with winds from 2 to 5 mph. The combination of high humidity and temperature put the ‘felt temperature ranges’ just at the ‘heat alert’ range at 100 degrees by 11 AM so I made sure I was finished before the temperatures got that high. Fortunately, our range has the firing line under a roof so it never got over 86 deg. F. in the shade. Altitude of the range is 250 feet above sea level.
All the loads were shot using Lapua brass with Remington 7 ½ small rifle primers. All bullets were loaded to achieve a 1.359 to 1.360 msec. exit time (12th reflection) to stay under Pmax using the 77 grain bullets with IMR4166 powder. The 1.359 to 1.360 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 1.359 to 1.360 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 2.340 1.750 wf 1.359 * 83/82 deg. F. CCI BR-4 Oryx 60 in.-lbs.
Sierra TMK #7177
77
2541
0.256
0.236
0.043
0.230
0.236
0.236
0.321


4
IMR4166 21.0 gr 2.337 1.748 wf 1.359 * 86/82 deg. F. CCI BR-4 Oryx 60 in-lbs.
Sierra TMK #7177
77
2541
0.267
0.266
0.016
0.249
0.265
.0266
0.288


4
IMR4166 21.1 gr 2.353 1.745 wf 1.359 * 90/84 deg. F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2545
0.278
0.282
0.038
0.229
0.277
0.286
0.320


4
IMR4166 21.1 gr 2.351 1.743 wf 1.359 * 92/86 deg, F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2545
0.310
0.306
0.024
0.285
0.302
0.309
0.343


16




0.278
0.281
0.035
























I was surprised that the CCI BR-4 primers out performed the Remington 7.5 primers by a slight margin today, especially since the Remington primers were shot in rounds that were seated out at the preferred O.A.L. to get the jump closest to the 0.020 jump at which the TMKs usually perform best.
It could have been the shooter losing concentration in the heat, but it didn’t seem to be affecting me all that much.
I allowed the rifle to cool down after the barrel temperature got around 130 deg. F. on the LCD temperature strip I have on the barrel. It was never calibrated, but it did ensure that the barrel temperature didn’t get too high with any load.
The overall 5-round group average has improved from 0.351 to 0.322 since mounting the Oryx chassis and shooting the 77 grain SMK and TMK bullets in the 1:9 twist barrel (averaging 0.271 primarily with 69 and 77 grain bullets). Prior to trying the bullets that are universally believed to be unstable in a 1:9 twist barrel, the overall group average for bullets from 50 to 70 grains was 0.362.

Bullet Weight Performance Ranked By Average
Weight Avg.- Median St Dev # Grps. Rank
-- 77 - 0.281 0.267 - 0.065 -- 70 ---- 1
-- 69 - 0.313 0.286 - 0.083 -- 39 ---- 2
-- 55 - 0.343 0.305 - 0.094 --- 4 ---- 3
-- 52 - 0.366 0.382 -0.079 -- 11 ---- 4
-- 53 - 0.376 0.366 - 0.082 --- 8 ---- 5
-- 50 - 0.390 0.392 - 0.064 --- 3 ---- 6
-- 60 - 0.487 0.487 - ------ --- 1 ---- 7
-- 70 - 0.619 0.670 - 0.189 --- 4 ---- 8
-- 68 - 0.653 0.653 - 0.001 --- 2 ---- 9
- All -- 0.322 0.288 - 0.106 - 142

[charlie b]

The 1:9 twist and 77gn bullets surprised me too. I believed the Sierra packaging and did not think they would stabilize. Then another person on the forum talked about shooting matches at 600yd with the 77gn bullets so I decided to try them. Instant success. Bonus is I can shoot to longer ranges than I thought I could with a .223. Even my poor shooting gets less than MOA at 600yd. It is also teaching me a lot about wind. :)

[CFJunkie]

I learned about wind shooting years ago both .22LR and .17 HMR in the wind at 100 yards.
I can't say I every got really good at it, but I learned a lot about Kentucky windage and I am still pretty good at holding off to get a bullet back into a group.
It is amazing how well you can judge where a bullet is going to land when you have to beat the wind.

These days it is easier to just shoot in the morning before the wind really gets too brisk.

[charlie b]

Yep, I try and shoot early mornings, but, I like to be able to shoot and hit when the wind is blowing as well.

[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, July 26th again tested the 77 gr TMK bullets with both Remington 7 ½ primers and CCI BR-4 primers. Temperatures on Friday were about 9 to 13 degrees cooler than the last session ranging from 71 to 77 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 but with two loads using Remington 7 ½ small rifle primers and two loads using CCI BR-4 primers. All bullets were loaded to achieve a 1.360 to 1.361 msec. exit time (12th reflection) to stay under Pmax using the 77 grain bullets with IMR4166 powder. The 1.360 to 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, so I could compare the results for each primer with the last session results, 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 1.360 to 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 1.750 wf 1.361 * 70/71 deg. F. Rem 7 ½ Oryx 60 in.-lbs.
Sierra TMK #7177
77
2540
0.246
0.290
0.104
0.091
0.293
0.287
0.313


4
IMR4166 21.0 gr 2.340 1.746 wf 1.361 * 73/72 deg. F. CCI BR-4 Oryx 60 in-lbs.
Sierra TMK #7177
77
2539
0.290
0.295
0.034
0.248
0.276
0.313
0.322


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
2540
0.273
0.262
0.034
0.247
0.252
0.272
.0321


4
IMR4166 21.0 gr 2.336 1.742 wf 1.361 * 77/77 deg, F. CCI BR-4 Oryx 60 in.-lbs.
Sierra TMK #7177
77
2539
0.312
.0313
0.065
0.247
0.265
0.361
0.375


16




0.280
0.282
0.064






















The first group listed for the first load was actually my second group of the day. After shooting the first 5-round group about normally, I really got focused and put 4 rounds in one hole and the last one slightly higher to expand the hole. Then I got overconfident and proceeded to shoot about like I usually do – adequate but not spectacular.
The Remington 7 ½ primers seemed to shoot better than the CCI BR-4 primers overall, but I can’t say why. The CCI BR-4 groups are were slightly bigger with most bullets.
Today-----Rem 7 ½ --- CCU BR-4
Average -- 0.260 ------- 0.301
Median -- 0.280 -------- 0.295
St Dev --- 0.073 ---------0.050
Overall – all bullets
Average -- 0.282 ------- 0.306
Median -- 0.272 -------- 0.291
St Dev --- 0.056 ---------0.090
# Grps --- 82 ------------- 40
Overall – 77 gr bullets
Average -- 0.276 ------- 0.310
Median -- 0.266 -------- 0.284
St Dev --- 0.046 ---------0.096
# Grps --- 54 ------------- 32

[CFJunkie]

I liked the results during yesterday’s session, Friday July 26th, that I loaded 50 rounds with the first load I shot yesterday and went back on Saturday morning, July 27th, to see if that load could duplicate the same results.
The load was IMR4166 21.0 gr 2.343 1.750 wf 1.361 * 70/71 deg. F. Rem 7 ½ Oryx 60 in.-lbs. with 77 gr Sierra Tipped Match King # 7177 bullets @ 2540 fps.
I shot 8 groups with the following results.



--- Avg. -- Median -- St Dev --- -1------- 2------- 3-------- 4 -------- 5 ------- 6 -------- 7 --------- 8 ---
0.299 ---- 0.265 ----- 0.061 ----0.239 -0.245 – 0.261 – 0.264 – 0.265 – 0.364 – 0.365 – 0.385

Compared to yesterday’s 0.246 average with this load, today’s results don’t look too good.
However, there was one incredible group that I shot yesterday that made all the difference. Without that 0.091 group, yesterday’s load averaged 0.297 which is just about what the same load averaged today.
That would tend to make me believe that yesterday’s one incredible group was an anomaly and the true performance is more like 0.297 to 0.299.