First results with new 12 FV .223

I tried my new Savage 12 FV .223 (1:9 twist) with 69 grain SMK and TMK bullets yesterday.
All 5 round groups @ 100 yards with temperatures in the high 30s, winds under 5 mph, altitude 250 ft. in Northern VA.

I mounted a cheap Leatherwood 8-32x56mm scope I bought on a big sale but never used just to break in the new rifle.
Based on these results, I think there is a scope upgrade in this rifle's future.
This rifle came with the LE/Varmint Accu-trigger set at 1 lb.11 oz. so I didn't adjust it any further.

The first load was used to adjust the scope - first at 25 yards and then at 100 yds and used 5 rounds.
It also seems like there is some truth to the comments on this forum about having to shoot a new Savage Barrel more than 10 rounds before it begins to group.
The groups were shot in the opposite order so the SMK groups got better as the rifle shot in.

The load description shows the powder, charge, seating depth, case trim length, primer, bullet exit time, and load temp/shooting temp.

# Groups	Load Description	Bullet	Bullet Weight	Vel.	Group (in.) 3-Shots	% Minutes of Angle	Avg Group (in.) 3 shots	% Minutes of Angle	Mean	Std Dev	1	2	3	4
3	IMR4166 24.4 2.265 case 1.750 CCI BR-4 wf 1.361 * 36/37 deg.	Sierra Match King # 1380	69	2953	0.313	30%	0.399	38.1%	0.422	0.078	0.313	0.422	0.463
4	IMR4166 24.2 2.317 case 1.750 CCI BR-4 wf 1.361 *39/37 deg.	Sierra Tipped Match King #7169	69	2948	0.289	28%	0.367	35.0%	0.367	0.067	0.289	0.339	0.394	0.444
						Overall	0.381		0.394	0.068

Love my .223 12FV....they are such great shooting guns. Great job!

That's dang good for an off the shelf, new rifle in a cheap plastic stock. Mine did the same before stock change and fine tuning a load. But if you're mostly shooting 100 to 200 yds, you might try the 53 gr V-Max and a faster powder like IMR 3031. The 53 VM has a fantastic BC for it's size and is quite accurate all the way to 500 yds. I've hit steel at 750 yds with it, but at that range it's pretty much out of breath.

I put a pillar bedded thumbhole stock under mine for my son to shoot and he can put 5 into groups measuring in the zero's and one's with that load while shooting off a bi-pod. I shoot my Criterion barreled 223 off a rest, free-recoil and I can't match what he shoots, but then his eyes are much younger.

Keep a lookout on the For Sale ads here and look for a target (red blade) AccuTrigger to install on your FV. Or buy an aftermarket trigger. That'll cut your group size substantially.

Congratulations on your purchase, and be careful of hitting the sides as you fall headfirst down the Savage rabbit hole while chasing the smallest groups.:cool:

PS. How did you manage to stuff 42.4 grains of powder in that little case, LOL

Texas10

I am currently loading for 52 gr SMK #1410, 52 Berger FB #22408, 53 gr SMK FB #1400, and 60 gr TMK #7160.
I'll probably load the 52 & 53 grain bullets with a faster powder like H335 or N133.
I'll probably use the IMR4166 for the 60 grain TMKs.

My 12 FV came with the LE/Varmint Accu-trigger set at 1 lb. 11oz.
I thought it was just about right and left it untouched.
I have a Target Accu-trigger on my 12 LRP and it came from the factory set at 10 oz. That was a bit too light in comparison with my other Accu-triggers that are all set at 2 lbs.
I reset it to 1 lb. 2 oz. so I wouldn't notice the difference.

The 42.4 entry was my dyslexia showing - the load was 24.4 grains. I just corrected it.

I recently bought the same gun, its a shooter. Keep us updated on load your progress.

That's encouraging news. I'm about half way through the break in on my new .223 12FV but was interrupted by Winter. Looking forward to getting back out on the range now that better weather is here.

As requested, here is an update of all the loads shot to date.
I repeated the first post data to make it easier to compare the results from the light to heavy bullets and the two different powders.
All the loads used Lapua brass and CCI BR-4 primers and all groups are 5 rounds, altitude was 250 ft. above sea level, winds were calm for the first 4 loads listed, less than 5 mph for the last two 69 grain loads.
The first four loads were shot on Wednesday, Mar. 20 in temperatures from 30 to 44 degrees and the last two were shot Monday, Mar. 18 in temperatures from 34 to 38 degrees.
The first three loads were shot at exit time of 1.134 msec., the 10th reflection of the shock wave because using the 12th reflection was too close to minimum load with the fast N133 powder.
The last two loads were shot at exit time of 1.361 msec., the 12th reflection, because the 10th reflection was over Pmax for the IMR4166 powder.
In my experience with my Les Baer .223 and apparently Texas10's as well, lighter bullets like a faster powder than the heavier bullets, and I have had very good results with the slower powders with heavier bullets.

# Grps	Load Description	Bullet	Bullet Weight	Vel.	Avg Group (in.)	1	2	3	4
2	N133 22.7 gr 2.255 3106 52 Berger FB case 1.750 wf 1.134 34/38 def F.	Berger FB #22408	52	3106	0.466	0.432	0.500
3	N133 22.7 gr 2.265 3106 52 SMK BHTP case 1.750 wf 1.134 36/40 def F.	Sierra Match King BHTP#1410	52	3105	0.343	0.285	0.361	0.382
3	N133 22.8 gr 2.265 3106 53 SMK FB case 1.751 wf 1.134 37/40 def F.	Sierra Match King FB #1400	53	3101	0.384	0.268	0.342	0.541
1	IMR4166 24.5 gr 2.322 60 TMK 3008 case 1.753 wf 1.134 40/44 deg F.	Sierra Tipped Match King #7160	60	3008	0.487	0.487
3	IMR4166 42.4 2.265 69 SMK 2953 case 1.750 wf 1.361 * 36/37 deg F.	Sierra Match King # 1380	69	2953	0.399	0.313	0.422	0.463
4	IMR4166 24.2 2.317 69 TMK 2948 case 1.750 wf 1.361 *39/37 deg F.	Sierra Tipped Match King #7169	69	2948	0.367	0.289	0.339	0.394	0.444

I had a new scope loosen up when I was shooting the 60 TMK load and lost some groups. It also may be why that load didn't shoot too well.
I had torqued the scope ring and rail mount screws to 30 in-lbs. but they still came loose, even on a low recoiling .223.
I think my old Fat Wrench may be due for a replacement. It's been being bounced around in my range bag for about 8 years.

Here is an update with some new bullets.
Temperatures were from 30 to 40 degrees with winds from 4 to 5 mph.
Altitude was 250 feet above sea level.
Primers were CCI BR-4, barrel exit times were all 1.134 msec.

Savage 12 FV .223 5 round Groups 8-32x56mm scope # Grps Load Description Bullet Weight Velocity Average Mean Std Dev 1 2 3 4 2 N133 23.2 gr 2.265 3110 case 1.754 33/34 def F. Nosler CC #53335 52 3110 0.367 0.367 0.112 0.287 0.446 4 N133 22.8 gr 2.265 3106 case 1.751 37/40 def F. Berger FB #22410 55 3079 0.343 0.305 0.094 0.281 0.288 0.322 0.481 2 IMR4166 24.0 2.272 2947 case 1.750 39/40 deg F. Hornady Match #2278 68 2947 0.653 0.653 0.001 0.652 0.653 2 IMR4166 24.4 2.270 2953 case 1.752 36/38 deg F. Nosler CC #17101 69 2953 0.403 0.403 0.085 0.343 0.463

Just another powder to try in your 12FV .223 with bullets from 45 to 62 grains: Winchester 748. With the right recipe/tune, it can be shockingly accurate. My 12FV 1 in 9 twist barrel loves 50-53 grain Hornady polymer tipped bullets, Federal GMM primer, between 26.5 and 27 grains of W748. Velocity close to 3300fps with 50 grainers and top powder charge out of my 26" barrel. Start 10% lower and work up to these powder charges. Congrats on your initial success and good luck on finding "the" perfect handload for your rifle.

The following are the results for the morning of April 17^th shot in Northern Virginia at 100 yards.

Temperatures from 57 to 68 degrees with winds from 3 to 6 mph. Altitude of the range is 250 feet above sea level.
All rounds were shot with a Savage 12 FV with the action screws torqued to 35 in.-lbs.
All the rounds were loaded using CCI BR-4 primers and all bullets were loaded to achieve a 1.134 msec. exit time that should be the sweet spot for a 26-inch 3% carbon steel barrel.
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.

This is the first time shooting the 52 grain Hornady ELD-M # 22491, 50 grain Berger FB #22406 and the Berger 70 grain VLD #22416 bullets.
The 69 TMK bullets were shot to see if there would be a difference in performance if I seated those bullets close to the Sierra recommended O.A.L. that I generally do not use. I normally seat the 69 TMKs out around 2.320 to keep the jump the same as I would see for SMK bullets seated at the Sierra SMK recommended O.A.L.

# Grps Load Description Bullet Weight Velocity Avg Median Std Dev 1 2 3 4 3 N133 22.7 gr 2.258 1.753 wf 1.134 * 62/2deg F. Berger FB # 22406 50 3121 0.390 0.392 0.064 0.325 0.392 0.452 4 N133 22.5 gr 2.252 1.754 wf 1.134 * 58/58 deg F. Hornady ELD-M # 22491 52 3094 0.333 0.332 0.072 0.265 0.277 0.387 0.403 1 IMR4166 23.9 gr 2.268 1.755 wf 1.134 *55/57 deg F. Sierra Tipped Match King #7169 69 2937 0.510 0.510 0.510 1 IMR4166 24.1 gr 2.267 1.751 wf 1.134 65/68deg F. Berger VLD #22418 70 2940 0.785 0.785 0.785 9 0.422 0.392 0.157

I shot one group of 69 TMK bullets seated back near the Sierra recommended O.A.L. of 2.260 to see how it performed compared to my normal seating at an O.A.L. around 2.320 or 0.060 further out into the barrel.
Actually, the jump at 2.320 for a 69 TMK is about the same as for a 69 SMK seated at 2.260 because the tip on the TMK extends the O.A.L. by 0.060.
The results with the 12 FV .223 are as follows for the 69 grain TMK:
O.A.L Grp Avg
2.268 0.510
2.317 0.367
------ 0.395 Average of all 69 gr TMK groups.

The results with the 12 FV for the various bullet weights to date are:
Wgt. Avg. ---Mean --St Dev # grps Rank
50 --0.390 --0.392 --0.064 ---- 8--- 4
52 --0.366 --0.382 --0.079 ----11--- 2
53 --0.384 --0.342 --0.141 ----3 ---- 3
55 --0.343 --0.305 --0.094 ----4 ---- 1
60 --0.487 --0.487 ------- ------1 --- 6
68 --0.653 --0.653 --0.001 -----2 --- 7
69 --0.398 --0.408 --0.074 ----10--- 5
70 --0.785 --0.785 ------- ------1 --- 8
All --0.408 --0.392--0.108 ---- 35

If you load that 50 grainer up to about 3350 fps, you may find some very nice results. And about 3250 for the 52 and 53 grain out of that 26 inch 9 twist. N-133 should do well, if not, try IMR 3031.

Texas10,

So far, I've loaded each of the powder-bullet combinations I've tried so far to match the 10th reflection time of the barrel (1.134 msec.) which should provide the best harmonics and the tightest crown.
So far, with all of my other rifles, that produces the smallest groups although the reflection time changes for every barrel length and type of steel.
With N133 powder, a 52 grain bullet that comes out at 3105 fps mv and with the 53 grain bullet it comes out at 3101 fps mv.
With a 3250 fps mv with the 52 grain bullet the reflection time would be 1.061 msec. so the 0.073 msec. shorter time would put the barrel reflection almost to the muzzle.
With the 53 grain bullet, 3250 fps would produce a 1.055 msec. reflection time and a 0.079 difference so the reflection would be even closer to the muzzle which would be at reflection time 1.021 msec.
That puts the reflection about 70% down the barrel to the muzzle which causes the groups to grow by about 0.06 inches.
If I choose a velocity that causes the reflection to approach the muzzle, my average group sizes grow by 0.070 to 0.090 inches.
That's based on hundreds of groups fired in 0.005 msec. increments so I generally start to first test my new rifles as close to the reflection time at the chamber as I can get.
It appears to work because the numbers seem to match up with pretty good group sizes.

So far, as you can see, I did have problems with the 68 grain Hornady Match #2278 bullets and with the Berger 70 grain #22418 bullets out of this rifle. They both shot terrible with this rifle.
The scary thing is that the 68 gr Hornady Match bullets shot two groups with a SD of only 0.001. That says the two groups were almost identical, so it tends to indicate that it was not the shooter.
I haven't yet figured out why they both shot so badly.

Since the 69 TMKs shot very well when they were seated out around 2.320, it wasn't bullet weight in the 1:9 twist. However the 69 TMKs shot lousy when they were seated at the Sierra recommended 2.260.

Maybe the Hornady 68s and the Berger 70s both need to be seated further out also, but they both shot so poorly, I'll probably wait to try them again.
I've got some 53 Hornady V-Max bullets to try next and I want to try H-4895 with the heavier bullets and H335 with the light bullets first.
I've had good results with both of those powders in my other .223s.

Texas10,

Your recommendation for increasing velocity got me thinking about where the 8th reflection time might be.
The 9th and the 11th reflections are at the muzzle. It takes 0.1134 msec. for the reflection to cover the 26 inches of barrel.
The next fastest reflection (8th) is 0.907 msec.
Turns out for a 53 grain bullet in a 26 inch barrel, H335 gets to the 8th reflection with 26.9 grains of powder with nominal seating depths and trim lengths.
It is 0.1+ grains within Pmax so it is very close - well within the expected variance for powder lots.
N133 powder is over Pmax before it can get close to 0.907 msec.

The following are the results for the morning of April 25^th shot in Northern Virginia at 100 yards. Temperatures from 59 to 62 degrees with winds from calm to 3 mph. Altitude of the range is 250 feet above sea level.
All rounds were shot with a Savage 12 FV using Lapua brass and CCI BR-4 primers and all bullets were loaded to achieve a 1.134 msec. exit time that should be the sweet spot for a 26-inch 3% carbon steel barrel.
I took the advice of Texas10 and finally got some 53 gr. Hornady V-Max bullets and shot them this morning. I shot a couple of groups of 53 gr Sierra SMKs as well that I had already tried as a control.
I also reshot a couple of groups with the Berger 70 grain VLD bullets with IMR4166 powder but I seated them out at 2.320 where my 69 TMKs shot so well. I also shot a group of TMKs seated out at 2.232 as a control and the 0.302 group fit right in the previous spread.
I shot the 53 grain bullets with N133 powder because I have over 9 lbs. of it and it takes forever to use up.
I shot the 69 and 70 grain bullets with IMR4166 Enduron powder to reshoot what I had already had results for.
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	N133 22.2 gr 2.250 1.757 wf 1.134 57/49 deg F.	Hornady V-Max #22265	53	3070	0.363	0.366	0.042	0.309	0.359	0.373	0.410
1	N133 22.9 gr 2.264 1.756 wf 1.134 59/59 deg. F.	Sierra SMK FB #1400	53	3100	0.404	0.404		0.404
1	IMR4166 24.4 2.322 1.754 wf 1.361 * 61/61 deg F.	Sierra TMK #7169	69	2947	0.302	0.302		0.302
2	IMR4166 24.2 gr 2.320 1.752 wf 1.134 62/62 deg F.	Berger VLD #22418	70	2948	0.670	0.670	0.040	0.641	0.6982
8					0.437	0.389	0.149

The results with the 12 FV for the various bullet weights through this morning are:
Wgt Avg --Mean St Dev # grps Rank
50 -0.390 0.392 0.064 -----8 ----4
52 -0.366 0.382 0.079 ----11 ----2
53 -0.376 0.366 0.082 -----3 -----3 - Previous average was 0.384
55 -0.343 0.305 0.094 -----4 -----1
60 -0.487 0.487 ------- ----1 -----6
68 -0.653 0.653 0.001 -----2 -----7
69 -0.389 0.394 0.076 ----10 -----5 – Previous average was 0.398
70 -0.708 0.698 0.073 -----3 -----8 - Previous average was 0.785
All -0.413 0.392 0.125 -----43

Looking at the top powder-bullet combinations provides a pretty good summary of what combination is providing accurate results.
Each entry is the composite total of all seating depths, and powder charges.
For example, the 69 grain TMK was seated at two different O.A.L.s - 2.260 and 2.320 and the combined results averaged 0.380.
The 2.260 O.A.L. shot 0.510 (which would have earned it 12th place) and the 2.320 shot 0.354 (good enough for 4th place).

5 Round Groups Savage 12 FV .223 Hand Loads Ranked By Average
# Grps Powder ----Bullet ----------------------Wgt -Avg -Best Load --Vel Rank
4 -------N133-- Hornady ELD-M # 22491 -----52- 0.333 -0.333 -----3094 1
3 -------N133 -Sierra Match King BHTP#1410 52 -0.343 -0.343 -----3105 2
4 -------N133 -Berger FB #22410------------- 55 -0.343 -0.343 -----3079 3
4 -------N133 -Hornady V-Max # 22265------ 53 -0.363 -0.363 -----3070 4
2 -------N133 -Nosler CC #53335 -------------52 -0.367 -0.367 -----3110 5
6 ---IMR4166 -Sierra TMK #7169 -------------69 -0.380 -0.302 -----2947 6
4 -------N133 -Sierra Match King FB #1400 - 53 -0.389 -0.384 -----3101 7
3 -------N133 -Berger Varmint FB # 22406 ---50 -0.390 -0.390 -----3121 8
3 ---IMR4166 -Sierra Match King # 1380 -----69 -0.399 -0.399 -----2953 9
2 ---IMR4166 Nosler CC #17101 --------------69 -0.403 -0.403 ----2953 10
2 -------N133 -Berger FB #22408 -------------52 -0.466 -0.466 ----3106 11
1 ---IMR4166 -Sierra TMK #7160 -------------60 -0.487 -0.487 ----3008 12
2 ---IMR4166 -Hornady Match #2278 --------68 -0.653 -0.653 ----2947 13
3 ---IMR4166 -Berger VLD #22418 -----------70 -0.708 -0.670 ----2948 14
43 ---------------------------------------------------0.413

Your average is pretty amazing, well done. I know it will mess with your exit time, but you should try pouring some coal to the 52's.

I intend to adjust the exit times eventually to verify the effect of moving off the reflection at the chamber, but so far I am trying to flesh out the data at the calculated reflection being at the muzzle.

I have adjusted velocity to get results with the reflection at different points down the barrels with my other 6.5mm Creedmoor rifles and with my two .308s and also with my Les Baer .223 semi-auto.

Generally, the accuracy begins to degrade as the reflection moves away from the optimum location (exit time so the reflection is at or very close to the chamber).

The better rifles lose about 0.1 in their average group size as the exit time approaches the reflection being close to the muzzle.

Love watching this development and percussion at work.

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 .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.

Always curious to try something I haven't tried yet, I loaded up 77 gr Sierra SMKs and TMKs with IMR4166 powder at the 12th reflection time (1.360 msec.) at 2540 fps in my 12 FV .223 and gave them a try.
The 10th reflection time (1.134 msec.) pushed the pressure over Pmax.

I was really surprised at the results.

# Grps -------- Load Description -------- --- Bullet --- Wgt. --- --Vel-- -- Avg. -- Median --St Dev-- ---1--- ---2--- ---3--- ---4---
-- 3 --- IMR4166 21.0 gr 2.384 1.758 --- SMK #9377 --77 ----- 2540 -- 0.515 -- 0.524 --- 0.045 -- 0.466 - 0.524 - 0.554
-------- wf 1.360 75/77 deg. F.
-- 4 ---IMR4166 20.9 gr 2.330 1.757 ---- TMK #7430 -- 77 ----- 2436 -- 0.280 -- 0.273 --- 0.053 -- 0.239 - 0.232 - 0.307 - 0.340
-------- wf 1.360 77/80 deg. F.
-- 7 --- Total ------------------------------------------------------------------ 0.380 -- 0.340 --- 0.134
-------- wf 1.360 77/80 deg F.

I have to say I was amazed by the performance of the TMKs compared to the SMKs.
So much for the concerns about stability problems with 77 grain bullets.
The SMKs averaged 0.270 better than the 70 grain Berger bullets that I had tried in earlier sessions but the TMKs shot

0.022 b

etter than any bullets I had tried with the 12 FV .223 so far.
I don't know if the results are atypical but I suspect that the higher ballistic coefficient of the TMKs might have had something to do with aiding in stabilization and achieving these results.

The 77 TMKs also out perform the 77 SMKs in my 1:8 twist.
Actually, TMKs that are similar weights to SMKs in my .308s consistently out perform the SMKs as well as long as the O.A.L. is longer to account for the 0.070 longer tips and get the ogive in the same place wrt the chamber.

I have always been surprised that no one supplies factory ammo with TMKs.
Perhaps it is because the TMKs would have to be seated longer by at least 0.050 and that might cause problems for magazine limits on some rifles.
Factory ammo just can't adapt for individual rifle chamber depths like a reloader can.
They would have to seat back to account for the smallest magazine and, from my experience, that would limit any benefits of the TMK wrt accuracy.
AR type mags limit seating depth on my 1:8 Les Baer Super Varmint and have forced me to use a single round follower with TMKs to seat the TMKs out where they perform best.
Thankfully, Savage mags have plenty of space for seating out the TMKs to take advantage of the TMK's inherent accuracy.

I like all the data you have collected on this.

I love my .223 and I do prefer the 77 SMK in the 1:9 barrel. They seem to be stable out to 600yd. I may try the TMK's and see if I get the same results as you.

A different question. I have been having life issues with brass. Specifically primer pockets getting loose after only 4 or 5 loadings. Has happened with different brass. Federal match, Fed budget, military brass and Winchester. I do not load at max, usually 23.5gn of Varget with the 77gn bullets. I used Rem BR primers so might that be the issue? I had a .223 many years ago but did not shoot it that much. This is the first time I have had this kind of problem in decades of shooting and reloading. In the past my case life was usually limited by split case necks at around 10 or more reloads per case.

I'm glad you liked the records of my loads with the .223. I thought serous shooters would get some value from posting them.

As for primer pocket wear, I had primer pocket wear problems similar to yours with my 6.5mm CM when it had a tight chamber (from the factory).
I got only 4 reloads with new Norma large primer brass regardless of what loads I used, even loads down at minimum pressure around 37,000 psi.
Savage bored the chamber out a few thousandths and now I get over 20 reloads with Lapua small primer brass.
Fortunately, the 12 LRP is now just as accurate with the bored chamber as it was with the tight chamber.
When I was researching the cause or worn primer pockets, the Hornady staff told me that precision barrels often have tight chambers to increase accuracy, but the tight chambers increase pressure conditions.
Personally, I think I just got a chamber that was cut with a reamer that was about worn out when they got to my barrel.
From my experience with the 12 LRP, high pressure conditions really do a job on primer pockets.

Other than that one rifle, I have had much better luck with numbers of reloads than you have across the board.
I have been using Lapua brass for at least 8 years and get over 20 reloads per lot with all my calibers - .223, .22-250, 6.5mm CM, and .308. My last lot of 6.5mm being used with my 6.5mm CM is on its 11 resize - 12 firings - and the primer pockets are still tight. That's over 1,000 rounds resized with the original brass. With that brass lot, I have never loaded any loads above 58,000 psi against a 63,000 psi Pmax.

I admit that because I am loading for exit time, I usually keep the loads well below Pmax, with the exception of my Les Baer Super Varmint .223 that has a 416R 18-inch barrel. The reflection times get loads very close to Pmax with some powders and over Pmax with others like Varget and H4895.

The 12 FV .223 I have been shooting for this thread has a 26-inch barrel and it stays well below Pmax unless I try to use the 10 reflection (1.134 msec.) with the heavy bullets and the .308 powders, especially the 77 grain bullets. That's why the load I used in post #19 with the 12 FV .223 is at 1.360 msec. reflection time - 1.360 msec. is the 12th reflection.

I don't seem to need to push the velocity and pressure to get accuracy.
If anything, I get better results with moderate velocities and pressures.
The sole exception is the Les Baer .223. I seems to retain its accuracy with the higher velocities and pressures, but at the expense of brass.
But ARs tend to mess up brass much more than bolt actions so I use mostly Federal brass with the Les Baer.

Come to think of it, Remington 7 1/2 Benchrest primers are a bit smaller in diameter than the CCI BR primers I have been using for the 12 FV and for my Les Baer.
The difference isn't great, but it doesn't take much to get a loose primer.
I always used Rem 7 1/2 primers with my original CZ 527 Varmint .223, but I didn't shoot heavy bullets with the CZ 527 Varmint until recently, so the powders were suited to lighter bullets.
However, the Rem primers didn't get loose in Lapua brass so I don't think it was just the primers.
I still think pressure has something to do with loosening primers.

I loaded a batch of Rem 7 1/2 primers with some 69 gr and 77 gr SMKs and TMKs and see if it makes any difference, either in accuracy or in primer pockets.
If the primers are loose, there should be some indications, like cavitating firing pin strikes as the primer moves back against the bolt.

I'll let you all know after I get to the range with the 12 FV .223 to try out the new loads.

Thanks for the prompt reply and the offer to test the primers. I know that Rem primers are known for being a bit on the 'soft' side so that may contribute. I was planning on changing to the CCI BR primers anyway. I use the large ones in my other rifles.

I thought about the case expansion a bit. Then it hit me that my previous .223 was a Contender, with a fully supported barrel, so it might never have seen loose pockets.

Just curious, what equipment are you using to measure things like exit time and determining shock wave reflection? As far as I understand it you'd need to know rate of change of acceleration down the barrel. Or is the shock a calculated number based on barrel length and muzzle velocity?

The speed of the reflection in the steel is the starting point.
Identifying the steel in your barrel is the first step.

Regular barrel steel reflects at 18, 916 fps.
3% carbon steel reflects at 19,107 fps. Savage barrels fit this category.
4140 and 4150 stainless steel reflects at 19,979 fps.
416R steel reflects at 20,014 fps.
The Materials Handbook lists 'Stainless Steel' with a generic speed of 20,000 (probably to cover everything from 4140 and 4150 and 416R stainless).

Then you have to know the length of your barrel from bolt face to the muzzle (consider the recess of the crown as not being part of the barrel steel.)
With the length of the barrel and the reflection time of the steel, you can calculate the time to go from the chamber to the muzzle.
Then you double it to get back from the muzzle to the chamber.
Do that about 10, 12 or 14 times and you get the exit time goals for your rifle.
You want the exit time to be on an even reflection because that is when the shock wave is back at the chamber when the bullet is leaving the muzzle.

The theory is that the less shock at the muzzle give you less vibration as the bullet leaves and also keeps the crown the tightest as the bullet is leaving.

QuickLOAD actually calculates the exit time and accounts for the acceleration of the bullet based upon the powder charge as well as considering the, barrel length, seating depth and trim length on the pressure when the bullet fires.

The choice of reflection time to match against exit time is up to you to figure out.

Even though QuickLOAD is a simulation, and many questions its validity based upon that, my seven rifles, accurate enough to use exit time for loading, produce results within 0.001% to 0.002% of the QuickLOAD calculated exit time. That variation can easily be caused by the mix of carbon in a particular barrel steel or poor barrel measurements on my part.

I built a spreadsheet to calculate reflection time based on the steel of my various barrels and their measured lengths.
You have to include the length of muzzle brakes, flash hiders and suppressors in the reflection time if they are attached to the barrel.
The problem with those appendages is identifying the metal they are made of and getting an accurate measurement of their mounted length and contribution to reflection time.

Thanks for that. I kinda figured since actual measurements require some interesting (and expensive) instruments. Have not worked with them on firearms but have used them on explosives tests.