Some of you have been following my published results with the 12 FV .223 on the “Ammunition & Reloading” forum in the “First results with new 12 FV .223” with the factory plastic stock and on the “110-Series Bolt Action Rifles” forum with the Oryx chassis in the “Documented results from replacing the 12 FV factory stock with an Oryx Chassis” thread.

While I was reporting the results on both threads, I got a note from another shooter who told me that he shot 77 gr SMKs in his 1:9 twist .223 and had good results.
He claimed that the bullet shape overcame the stabilization problem.

I have had great results with 77 grain SMKs and TMKs in my 1:8 twist Les Baer .223 but I have always read that a 1:9 twist wouldn't stabilize bullets over 73 gr bullets, so I never tried them in my two 1:9 twist rifles. In fact, both Sierra 77 grain bullets have a warning not to use the 77 grain bullets in barrels with twist slower than 1:8.

Always curious to try something I haven’t tried yet, I disregarded the long-held belief that a 1:9 twist can’t stabilize 77-grain bullets, and experimented with 77-grain Sierra SMK and TMK bullets in my Savage 12 FV 1:9 twist barrel. Surprisingly, the 77 grain bullets have been consistently more accurate than even the 69 grain bullets that the 12 FV really shot well.

Here is a summary of the results of 5 round groups sorted by bullet weight and by average.
By Weight By Average
Wgt. Avg. Median St Dev # Grps. Rank ----Wgt. Avg. Median St Dev # Grps. Rank
50 0.390 0.392 0.064 --- 3------ 6 ------- 77 0.285 0.271 - 0.066 - 94 ----- 1
52 0.366 0.382 0.079 --- 11 ---- 4 ------- 69 0.313 0.286 - 0.083 - 39 ----- 2
53 0.376 0.366 0.082 --- 8 ------ 5 ------ 55 0.343 0.305 - 0.094 -- 4 ------ 3
55 0.343 0.305 0.094 --- 4 ------ 3 ------ 52 0.366 0.382 - 0.079 - 11------ 4
60 0.487 0.487 ------- --- 1 ------ 7 ----- 53 0.376 0.366 - 0.082 -- 8 ------ 5
68 0.653 0.653 0.001 --- 2 ------ 9 ----- 50 0.390 0.392 - 0.064 -- 3 ------ 6
69 0.313 0.286 0.083 --- 39 ----- 2 ------ 60 0.487 0.487 - --------- 1 ------ 7
70 0.619 0.670 0.189 --- 4 ------ 8 -------70 0.619 0.670 - 0.189 -- 4 ------ 8
77 0.285 0.271 0.066 --- 94 ----- 1 ------ 68 0.653 0.653 - 0.001 -- 2 ------ 9
All 0.319 0.288 0.102 --166 ---------------All 0.319 0.288 - 0.102 -166

Note: I tend to shoot bullets that shoot the most accurately, but I have only been shooting the 77 grain bullets since June 19th, so I have really been impressed by the accuracy the 77 grain bullets produce and the group counts show it.
The difference in performance in the 69 and 77 grain bullets needs to be explored in a number of ways since both bullet weights were shot in two different stocks and with two different primers.

I had been shooting CCI BR-4 primers with Lapua brass (made to use small rifle primers) and after a member reported that he was having problems with loose primer pockets with Remington 7 ½ BR primers I offered to try those primers because I had over 5,000 lying around. I tried the Remington 7 ½ BR primers and found that they performed slightly better than the CCI BR-4s so I shot more loads using them to see if the results would hold up with a larger statistical sample. I also reported that they were slightly smaller in diameter and were easier to fit in to the primer pockets in Lapua brass that had been reloaded more than 11 times, but weren’t especially loose. The results showed that Remington primers were performing well.

Just a few weeks after trying the Remington primers, I purchased an Oryx stock for the 12 FV .223 to get a detachable magazine. That added another potential variation in the results so I analyzed the data to see if the results were consistent under both the primer change and the plastic factory stock to aluminum chassis change.

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 %Impr
Sierra Match King # 1380 - 69 gr -------0.329 0.303 0.087 --- 10 ------ 0.307 0.295 0.098 ---- 7 ---- 0.022 6.7%
Sierra Tipped Match King #7169 - 69 gr 0.304 0.288 0.061 --- 12 ------ 0.258 0.272 0.038 ---- 7 ---- 0.046 15.2%
Sierra Match King # 9377 - 77 gr ------ 0.344 0.327 0.118 --- 11 ------- 0.250 0.245 0.016 --- 11 ---- 0.094 27.3%
Sierra Tipped Match King #7177 -77 gr 0.272 0.266 0.039 --- 20 ------- 0.286 0.286 0.059 --- 51 ---- 0.014 -5.0%
----------------------Overall ---------- 0.296 0.282 0.078 --- 53 ------- 0.280 0.272 0.059 --- 76 ---- 0.016 5.4%

The Oryx chassis provided some improvement but it wasn’t as consistent as I would have expected. The biggest improvement came with the 77 SMK bullets and the 77 TMK bullets actually performed better in the factory stock. That was a surprise and there is no apparent reason for the difference that I can determine.

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 BR Primers
----------------------Bullets--------------- Avg. Median St Dev # Grps. Avg. Median St Dev # Grps. Delta %Impr
Sierra Match King # 1380 - 69 gr ------- 0.399 0.422 0.078 --- 3 --- 0.303 0.287 0.084 -- 14 ---- 0.096 24.2%
Sierra Tipped Match King #7169 - 69 gr- 0.354 0.339 0.065 --- 5 --- 0.264 0.272 0.030 -- 14 --- 0.090 25.5%
Sierra Match King # 9377 - 77 gr ------- 0.352 0.287 0.140 --- 8 ---- 0.265 0.250 0.038 -- 15 --- 0.087 24.7%
Sierra Tipped Match King #7177 -77 gr 0.269 0.282 0.051 -- 24 ---- 0.289 0.277 0.055 -- 47---- 0.020 -7.4%
-------------------------Overall -------- 0.306 0.291 0.090 -- 40 ---- 0.283 0.272 0.056 -- 90 --- 0.023 7.4%

The performance with the different primers shows just about the same kind of results, even down to the better performance for the CCI primers over the Remington primers for the 77 TMK bullets when all the other bullets performed better with the Remington primers. Again, there doesn’t seem to be an apparent reason for the difference that I can determine from looking at the data.

Confirmation using other 1:9 twist rifles
I then asked two range buddies who had 1:9 twist .223 bolt actions to test how their rifles shot with 77 grain bullets.
Two tried 77 gr Federal Gold Medal Match with SMK bullets in their rifles.
One shot a 12 FV .223 and the other shot a CZ 527 Varmint .223, both with 1:9 twists.

The Savage 12 FV shot factory Federal Premium Gold Medal Match SMK 77 gr ammo to a 16.1% larger average than his factory average for all bullet weights.
The same 12 FV shot factory Nosler Custom Competition 77 gr ammo to a 15.6% smaller average than his factory average for all bullet weights.
At a later session, the Savage 12 FV owner tried hand loads using 77 TMK bullets and shot the hand loads to a 11.2% smaller average than his hand load average for all bullet weights.
The 77 grain TMK hand load average was 40.3% smaller than the 77-grain factory SMK average and 28.0% smaller than the Nosler CC average.
The 77 grain TMK hand load average was also 9.6% smaller than the rifle’s 69-grain SMK hand load average.

The owner of the CZ 527 shot factory Federal Premium Gold Medal Match SMK 77 gr ammo to a 13.2% smaller than his factory ammo average for all bullet weights.

Conclusion:

The historical concerns that a 1:9 twist barrel will not stabilize a 77-grain bullet appears to be a myth, at least for Sierra SMK and TMK bullets and Nosler Custom Competition bullets, even though both the Sierra boxes and Nosler CC boxes clearly advised that their bullets were only recommended for 1:8 twist barrels or faster.