6.5mm 123gr Sierra MK Loads

[LEO]

I have been searching through all of the usual competition shooting forums for any information on the success,or lack thereof) of this new bullet in the 6.5x284 Win. I have been very surprised to find nary a single comment, for good or ill. It seems this bullet has not caught on with anyone... serious competitor or casual target shooter. I've tried 46.5 to 49.0 grains of H4350, Lapua brass, with a 210M primer. Results were mediocre, compared to what I have come to expect with the 142gr MK and 51.5gr H4831SC,all else the same). The best group I could get with the 123gr bullets was .78 at 100yds. This is almost twice as big as my best 142gr groups. Has anyone else tried this bullet?

BTW: I'm also looking for a 107gr Sierra MK load for my 6.5X284. Thought it might be interesting to try it out on my local groundhogs... Any recommendations?

 

[Asa_Yam]

The 6.5-.284 has too much case capacity for lightweight 6.5mm bullets. While you can get extra speed by going lighter, the gains probably aren't as great as you might think. Push the bullet too fast, and you start seeing grey puffs downrange,bullet came apart in flight).

Even with bullets in the 140 grain weight range, the 6.5-.284 often has more case capacity than an accurate load requires. Most accurate 140ish grain loads are in the 2950-3100 FPS range. Fill the case, and you might see over 3200-3300. With 1-8.5" or 1-9" twist barrels, you're on the verge of having these bullets disintegrate in flight at such velocities.

 

[RIFLE1]

Concerning the 123 Sierra's,.... I have a tactical rifle with a 28" long 6.5mm Pacnor 8" twist, and on it's worst day it will shoot in the .4" range. Generally speaking, it will shoot high .2" to mid .3".,conditions allowing) Very consistently I might add. This is in a 6.5x47 Lapua, 35gr of Varget and a CCI450 of course. The 6.5/284 can be tuned to shoot the lighter projectiles, but it isn't easy to keep it tuned.

Chris

 

[Forum Boss]

When I had a .260 Rem, the 123 Scenar and the 100gr FB Sierra Varminter were the two best-shooting projectiles. In the wind, of course, the 123 won out big time--and it was more slippery than the 120 Sierra MK as well.

For me, in the 260, the 123 and 43.0+ gr of H4350 was a winning combo--very low ES/SD and nice, consistently round tight groups with few "flyers".

But in the bigger 6.5x284, I think it makes sense to go for better BC. You have the capacity to drive the 139 Scenar and 140 VLDs where they like to run,2950-3050 fps), so why not do that?

 

[LEO]

Point taken...

 

[Shelley]

I spent yesterday at the range working up a load for the 123 gr Sierra MK. I ended up pushing it about 3050fps in a 27" barrel and saw one five shot group that measured .174". I have a hundred loaded for a match that I'll shoot today. That'll tell me if the bullet, gun and load really work as well as I hope they will.

I'm shooting the 123 in a 6BR case blown out .175" and necked up to .264" I call it a 6.5BRXX.

Shelley

 

[Forum Boss]

Shelley--

Wow, that's some serious speed you're getting out of that little case. Proof #1 of the case's efficiency and #2 the strength of the brass. I was using Norma .243 brass necked to 6.5mm and 2980 or so was showing big ejector marks on the cases. That was in a 24" bbl. 3000 fps and the case head expanded enough that I had trouble getting the brass in a shellholder and the primer pockets were loose.

 

[RIFLE1]

We've seen 2975+ out of a 6.5 Dasher with a 28" tube with Varget and the 123 Sierra,.....not a light load by any means,.... but it does leave you with a reloadable case.,Lapua brass)

Chris

 

[Shelley]

Varget alone pressured up too much so I went to a mixture of 8 ounces of Varget to 6 ounces of H4350 and started getting good accuracy and good case life. I know...... I've heard all of those arguments about mixing powders but I've been blending for years and sometimes it just works great when I can't find a commercially available powder that has the characteristics that I require.

Man, do I feel stupid. The match that I was going to shoot was last weekend. I thought the match was on the last Saturday of every month but it's held on the fourth Saturday of every month. June had five Saturdays. There I was, all dressed up for the dance.... drove a hundred miles and no one showed up. Oh well, I'll just take the 6.5BRXX out to Gene Beggs' Tunnel and spend a couple of days working with it. That'll also work to tell me how much potential it has.

I want to get it tuned in as good as possible before July 14th because I'm going to shoot it at the Utopia Invitational match which is a 400 yard match on a ranch in windy West Texas. There's a $1,000.00 prize for first place. You shoot five matches at clay targets mounted on a target board. Five of the targets are 2" in diameter, two are 4" and one is 5",or there abouts). You are allowed to take 10 rounds to the bench for each match. The smaller the target, the higher the score for hitting it. Sounds easy, huh???? Only .5 minute of angle needed, but then there's the tricky wind at the range that's built in a canyon and mirage. It's limited to 24 shooters and you must get invited. I feel good about getting invited cause it's a way cool match.

Shelley

 

[LongRanger]

Am working up loads for 6.5x47 with 123 SMK for 1000y, and tried but stopped tests on 6.5 130gr Berger.

Yesterday on first visit to 1000y with new,250 rounds) Krieger 28" 8.5 twist, 38.3 grains Varget and Sierra 123 for 3010 fps settled down to 5 x's on new F-Class target,5" "x" ring) in last 5 shots of 20 shot string. Shots 1-15 were aggravating high 9, low 9, high 9 etc. Since I was testing, I did not hold-off for conditions,variable 5mph). Horizontal was great, rarely exceeding width of 10 ring. Altho speed was there, shots seemed to lack authority. At 200 yards, this load shot 1/2" with ES 7. Am leaving barrel dirty to revisit this load during next "calm" weather.

In my rifle, anything over 39.3 Varget with 123 SMK causes occasional expansion of extractor groove.

For comparison, at same fps, my 6BRX with 107 SMK's and 33.1 grains Varget shoots 3 minutes higher.

Varget for 123 SMK may be just a little too hot. Bought a bottle of 4350 and a bottle of 4381SC today to try out. Already tried RL-15,sooty crap I will never foul a barrel with again). Also tried VV 550 @ 40.1 grains for 3100 fps....this load was a little too hot but shot clean and I need to revisit since the groups were small and ES was only 6 fps.