308 Winchester Load Development: 175-grain Sierra Matchking and Varget

M700 308 Winchester 22 barrel surefire nightforce spuhr r right 3

308 Winchester Load Development

I headed to the range to do some load development for my custom Remington 700 chambered in 308 Winchester with a 22″ long barrel (my previous load was a NRA High Power pet load).

The rifle was built with the following parts from Brownells:

If you’d like to read about how the rifle was built, please see:

No sense reinventing the wheel with a cartridge this common. I selected long proven match quality components: 175-grain Sierra Matchking (SMK) bullets, Lapua brass, Hodgdon Varget powder and Wolf large rifle primers.

The Lapua brass I am using has been fired 3 times in this rifle. Cases were neck sized, trimmed to length and cleaned in an ultrasonic cleaner. I loaded 10-rounds of each of the 5 different charges in .3-grain increments. I stopped .8-grains below the maximum charge listed by Hodgdon for this powder and bullet combination. Charges were dispensed using an RCBS Chargemaster.

I fired two, 5-shot groups with each load. Shooting was done prone, from a Harris bipod, with a rear bag. Target distance was 100 yards. Range conditions were 40F, a full-value wind was gusting at 15 miles-per-hour, lighting was poor with the sun low at about 1 o’clock to the shooter (it was approximately 1 hour before sunset in the late fall). All 50 rounds were fired in approximately 30 minutes, the barrel was not allowed to cool between strings.

A quick caveat: since I shoot mostly prone, I do my load development prone. I do realize that I will likely achieve better results from a bench, but find this a more authentic test (and is good practice). I have similar feelings about not letting the barrel cool. While it opens the groups up, it does give a more accurate indication of the rifles performance under long strings of fire.

Ballistic information was recorded with a Magnetospeed V3 barrel mounted ballistic chronograph. All velocity information presented below, represents data for both 5-shot strings (10 rounds total).

WARNING: The loads shown are for informational purposes only. They are only safe in the rifle shown and may not be safe in yours. Consult appropriate load manuals prior to developing your own handloads. Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

308 WINCHESTER- 3XF Lapua Brass 2.832” OALWARNING: For reference purposes only, read disclaimer above, only safe in test gun 5-shot group sizes are measured center-to-center in inches
Load	Bullet	Powder	Primer	Velocity (FPS)	SD	Distance	Group 1	Group 2	AVG
1	175 SMK	43.0 Varget	Wolf LR	2588	8.7	100 yds	.917	.857	.887
2	175 SMK	43.3 Varget	Wolf LR	2607	12.8	100 yds	.805	.676	.756
3	175 SMK	43.6 Varget	Wolf LR	2614	9.3	100 yds	.775	.452	.764
4	175 SMK	43.9 Varget	Wolf LR	2630	8.0	100 yds	.867	1.095	.981
5	175 SMK	44.2 Varget	Wolf LR	2659	12.0	100 yds	1.045	.609	.827
AVG									.843

All ten 5-shot groups averaged .843″ (.805 MOA) and all of the loads had a standard deviation (SD) of less than 13. Loads 1 and 3 each had a called flier. Load 1, group 2, had four rounds .279″ with a called flyer opening it up to .857″. Load 3, group 1, had four rounds .323″ with a called flyer opening it up to .775″. Load 1, group 1, had round #2 go way left for some reason as well. I didn’t call it, but the cold bore shot, as well as the last 3 rounds of the group printed nicely.

Keep in mind, this was a hot barrel, the light was bad, and I was in a rush trying to beat the sunset. I think the results would have been a little better if I had more time and allowed the barrel to cool down between strings.

Looking at the targets, velocities, SDs and groups sizes of the five loads, I plan on doing further load development on #1 (see photo above: second and third target in top row) and #3 (see photo above: second and fourth target in second row) since I view them as the most promising. I’ll be loading up 25 rounds of each and shooting, 5, 5-shot groups without the chronograph attached to the rifle. Once I see which load the rifle likes better, I’ll be tweaking the OAL of the cartridge to see if I can squeeze out any more accuracy.

I’ve shot a few 10-shot groups in the .600″s with this rifle and my other load. I’d like to see 1/2 MOA or better over 50 rounds (10, 5-shot groups). I’m believe I am heading in the right direction.

Update: