Poor accuracy with 155 SMKs and 155 Scenars

B

boomfab

Sergeant
Full Member
Minuteman
Oct 29, 2007
278
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43
Missouri, USA
#1
I've got an 18" FN SPR that shoots 168 SMKs with Varget lights out, sub-half MOA if the shooter does their part.

I tried some 155 SMKs and some 155 Lapua Scenars. Both are about 5 MOA. I'm pushing them with Ramshot TAC at about 2775 FPS. 2.80" OAL.

Is there some reason that 155s just won't work well with a 1/12 twist 18" barrel? Or should I change powders?
 
#2
Re: Poor accuracy with 155 SMKs and 155 Scenars

twist rate is fine

have you played around with different powders and charges?

They might even improve accuracy when they are 200 yards... but 5moa at 100 is crazy
 
#5
Re: Poor accuracy with 155 SMKs and 155 Scenars

I had a handful of the sierra 155s and they shot well out of my 1:10 18", I think it was 46 varget and win brass 2.805 overall. 5MOA means something is really wrong, it shouldn't be that large with any ammunition out there.

If you can't get them to shoot give them to me, I am getting ready to buy a bunch of bullets and will put them to good use.

Also 2775 holy hell I can't get near that velocity out of my 18" but then it's a gas gun with factory barrel and not-so-tight-chamber, I think my above load was 2600-2650.
 
#7
Re: Poor accuracy with 155 SMKs and 155 Scenars

I'll try another powder. TAC is also giving me sub-par accuracy out of the same gun with 175 SMKs as well. It works good for me in .223 loads.

I'll try some Reloader-15 that I have laying around.
 
#11
Re: Poor accuracy with 155 SMKs and 155 Scenars

I can't get the 155 Scenars to shoot for shit either. I've put it through the ringer with seating depth and different Varget charges. I gave up on the bullet for now, but will try a differnt powder out at some point. Out of curiosity, I bought some 168SMK Black Hills Match to see how they'd shoot, fricken 200yd group looked like a shot gun pattern.

The past week and half or so I've been playing around with 150 SMK's, and tonight with 47.2gr Varget at 2.775", I got them suckers shooting dang well, by my standards anyways. I've also loaded up a 150 SGK load, copied right out of the Sierra manual, and they shot better than I can get the Scenars to.
 
#12
Re: Poor accuracy with 155 SMKs and 155 Scenars

I used Lapua RL15 46.1gr 1/11.25 twist, buddy uses Varget 47.8 1/12 twist those two load where hard on brass and primer pockets. I am shooting IMR 8208 22" 1/10 twist barrel 2920 fps no preasure signs, does not work brass as hard. All these loads will hold a 1 1/2" x ring if you can run about 195-198 x's in teens for 20 rounds at 300 yds. Run great at 600 and a 1000 yds.
 
#13
Re: Poor accuracy with 155 SMKs and 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">sometimes.....you got to push 'em harder </div></div>

I've been told that as well.....When I feel like fighting them again, and get a little bolder with my reloading, I'll work up some hotter loads and see how that goes.

The highest I went was 47gr Varget, 5 thou off the lands, with a 20.25" barrel. Avg MV was 2735.
 
#14
Re: Poor accuracy with 155 SMKs and 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outsydlooknin75</div><div class="ubbcode-body">155smk's are flying out of my spsT just fine. 46.8grains of varget under it loaded out to 8.825 with a standard CCI primer</div></div>

**I think he means 2.825**
 
#15
Re: Poor accuracy with 155 SMKs and 155 Scenars

Try RL15 or Varget, and seat them just a tad longer, like 2.82". My rifle likes them seated .12" from the lands and .06" from the lands under 45 gr of RL15.
 
#16
Re: Poor accuracy with 155 SMKs and 155 Scenars

I've tried both 155 SMK Palmas and 155 scenars and they both shot terribly in my 20" SPS-T, yet 168s and 175 SMKs shoot extremely well. The best velocity I've gotten out of them using both Varget and RL-15 in Lapua brass has been about 2780 before I started getting prassure signs. Accuracy was 1.5 MOA at best.

My theory is that these lighter bullets like to go smoking fast before they start really making a differnce. And with a short barrel, I just can't get them into the high 28s and 2900s where they like to be.

I have a unopened box of 500 of the 155SMK Palma's (2155 version) if anyone wants to trade for some 175 SMKs or 178 AMAXs
 
#17
Re: Poor accuracy with 155 SMKs and 155 Scenars

This is what TAC gave me from a 20" LTR barrel:

Ramshot TAC 46.5
CCI 200
Win Brass
COAL 2.855"
2924 fps average


Scenars were hBn prepped.
 
#20
Re: Poor accuracy with 155 SMKs and 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: boomfab</div><div class="ubbcode-body">I'm pushing them with Ramshot TAC at about 2775 FPS. 2.80" OAL. </div></div>

Way too slow, need to get them up to 2900+fps, although there should be another accuracy node down near 2650.
 
#21
Re: Poor accuracy with 155 SMKs and 155 Scenars

As a few have said I concur they like speed. I wouldn't bother with them if you can't get them to 2900+. Like Swan said Varget, 47+ granis if you get the speed.
 
#22
Re: Poor accuracy with 155 SMKs and 155 Scenars

I've been thru the wringer for 2 months trying to get my M1A NM to tighten up groups. Starting to come together. It shoots Lithuanian NATO pretty well, that's a 147 gr @ 2840 fps. 43grs of TAC with 155 Scenar @ 2769 just shot 1 inch 7 0f 10 shots, still got a couple little flyers. 168 SMK 41.5grs H4895 @ 2663 did a bout as well with a little horizontal stringing, will back down the speed for tomorrow closer to M852 specs, it's looking real good. JAE GEN2 stock has worked wonders too, a sweet piece of technology off ebay. Torqued action to factory spec 15 inch pounds and cranked down the barrel tensioner tight (not recommended at first), that really helped group consistency. Got a high US 10X on it with no paralax and that adjustable cheek piece really helps the cheek weld/head position.
 
#23
Re: Poor accuracy with 155 SMKs and 155 Scenars

Oh yeah, reaming out the gas cylinder plug and piston with a .323 and .18 drill bit smoothed things out as well. Do that every session now. Got a sadlak sping guide which smoother out the action and made magazine insertion a dream. NM piston d/i (another acronym for the list "due in") for the 168's. Hope that smooths operation as much as Garand grease on the op rod channel.
 
#24
Re: Poor accuracy with 155 SMKs and 155 Scenars

Oh Yeah2. Forgot to mention dropping COAL to 2.79 tightened things up in the M1A and GAP bolt 308 after trying up to 2.81, not supposed to be that way. Try this for mental juggling: load development for 2 .308's at the same time, same range, same loading bench, different brass, bullets, powders primers, COALS, chamber spec's, anything I left out? Got dizzy sometimes, got notes coming out my yang....
cry.gif
 
#25
Re: Poor accuracy with 155 SMKs and 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: boomfab</div><div class="ubbcode-body">I'm pushing them with Ramshot TAC at about 2775 FPS. 2.80" OAL. </div></div>

Way too slow, need to get them up to 2900+fps, although there should be another accuracy node down near 2650. </div></div>

So what are my options to get more speed out of a 20.25" barrel? I posted earlier I was averaging 2735fps with 47 Varget, 5 thou off the lands. I was wrong, that was with 46gr Varget, which seemed to shoot quite a bit better than anything else in the 45-47gr range. I never did chrono the 47's, as they shot like shit. So, if I need to get more speed to get accuracy, what would you do next; different powder, deaper seating depth, work up with Varget until I see signs of pressure?

Thanks
 
#26
Re: Poor accuracy with 155 SMKs and 155 Scenars

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fisky</div><div class="ubbcode-body">
So what are my options to get more speed out of a 20.25" barrel? </div></div>

Other than grabbing it with both hands and pulling in an effort to make it longer, not much.

You might be able to squeeze 48ish grains behind them but if you have a good, accurate load that does what you want it to I wouldn't worry about the velocity.
 
#27
Re: Poor accuracy with 155 SMKs and 155 Scenars

I'm no expert by any stretch of the imagination and the real experts here will probably correct (educate) me on this but something I thought I'd mention that I just read in "Modern Reloading" was adding a crimp (via LFCD) proved to give more consistency and higher initial pressures because of the pull weight on the bullet from the neck. Seemed like a good argument for crimping but I've never tested it. See page 57 in chapter 2 for details.
Now back to the real experts....
 
#28
Re: Poor accuracy with 155 SMKs and 155 Scenars

I was having similar results, higher velocities gave me horizontal stringing with 155's, took a while to find the sweet spot but it was 2700 fps and 2.9 COAL in my gun. I believe I passed that sweet spot/accuracy node so I back tracked, took me 3 powders IMR4895, H4895, RE15) before I settled on TAC, I don't much care about what velocity works, everything above should be supersonic at 1k with 155's
 
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