135 SMKs and semi-autos revisited, w/questions ...

[Snakum]

I'm still trying to my semi auto to shoot ten round strings into 1.5 MOA consistently, out to 500 yards max. I've gotten very close with 150gr SMKs over 41.5gr 4895. Not quite there yet.

Anyone using 135gr SMKs in a semi or a bolt gun? What is the max range you shoot them? How are they working for you?

What powder you using, what wt? Velocity you're getting and barrel length your using to get it?

I've always used 4895, would an even faster burning powder be better for an 18 incher? Which one and why?


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Background:
Rifle is Saiga 308 with barrel trim to 18" and target crown, and PWS FSC30 brake. Twist rate is (iirc) 11.5. I tried 155 and 168gr Amaxes and tried 150, 155, 168, and 175gr SMKs, always over 4895. After learning how to actually shoot a semi for med range work (very different from bolt gun), almost every load I could get 2 MOA for ten shot strings out to 300 or 400, with the only difference being how many of the ten rounds in each string fell into 1 MOA or 1.5 MOA. I noticed as I went lower in weight on the SMKs (150gr) my ten round strings using a lighter load of 41.5 IMR 4895 would run them close to 2500fps and yield five or six of the ten rounds at 1 MOA or better, two or three more making it 1.5 MOA, with the usual crazy fliers (not called) taking it to 2 MOA - always shooting prone with the rifle just thrown over a ruck with a rear bag. So I want to try 135gr SMKs next, hoping the lighter bullet with moderate 4895 wts will reduce receiver flex even more, which I think may account for the crazy non-called fliers.

 

[Heman]

Re: 135 SMKs and semi-autos revisited, w/questions ...

The 135gr SMK was designed by Sierra for the M1A match at Camp Perry which is shot at 300yards. Shawn McKenna shoots them at around 2950fps in his M1A but he has a 1:15 twist barrel in his M1A. Most people don't have that slow a twist so the velocities have to be kept down. I've read were Sierra suggests around 2700fps. I've been playing around with them in my National Match M1 1:12 twist and they like 47gr of IMR4895, shot them the other day at 300 on a 300 rapid target and elevation was half to 3/4 of the 10 ring. 47.5gr group opened way up, 46 and 46.5gr rifle doesn't like them. Also on seating depth they seem to shoot best seated at 3.160" overall which puts the base right at the shoulder neck junction. As far as elevation I need to come up an extra 1.5 to 2MOA for 300 than what I do with a 175 load. If your using them in a M1/M1A platform I'm going to say 300yds, as you have the whole gas system issue and wind drift won't be your friend. If it's a windy day I probably will sling up tighter and shoot the 175's for 300rapids and the 135's just at 200. Maybe they can be pushed harder probably can but I haven't as I'm just looking for a light load for rapids.

 

[Snakum]

Re: 135 SMKs and semi-autos revisited, w/questions ...

Thanks for the info. 2700 would be plenty hot for what I use this rifle for. I just need it flying true for 500 yards. I use the FCP for anything past that. Ordered some of the 135s and will give em a shot.

 

[Heman]

Re: 135 SMKs and semi-autos revisited, w/questions ...

If your going to go to 500 with them I'd try and find another higher velocity accuracy node. Was corresponding with Paul Box today at Sierra he said they're very picky on seating depth since they got a very small bearing surface in a chamber with a long free bore. In a shorter chamber they're better suited.

 

[Snakum]

Re: 135 SMKs and semi-autos revisited, w/questions ...

The Ruski seems to like lighter bullets and slower velocities, and I assume this is due to the inherent instability of the stamped receiver and barrel. Both flex more than an AR platform. Then there is the rail attachment of the scope, which introduces another variable.

I've worked up the 135s at 40.0, 40.5, 41.0 and 41.5 grains of 4895 and will send them tomorrow afternoon if the weather holds. I work up six rounds at each weight, shoot them round robin style after warming the barrel up with three or four FMJs, throw the worst flyer out of each group, and then start fine tuning the charge and playing with the seating depth. Ten round groups are shot next.

We'll see how it shoots tomorrow with the 135s, and hopefully I'll wind up with ten-round strings hovering around 1.5".

 

[Heman]

Re: 135 SMKs and semi-autos revisited, w/questions ...

Yeah if you are going slower than 2700fps then I'd be leary of 500 yards with them as far as the wind blowing them around. Where I'm shooting them I know I'm cranking an extra 1.5 to 2 MOA for 300 than I do for my 175's in my M1 so that is telling me at 600 I'd be cranking on A LOT more than I would and they're going to get blown around. Keep me posted though as there isn't a lot of load info out on them.

 

[Snakum]

Re: 135 SMKs and semi-autos revisited, w/questions ...

Just shot the four strings, and it was the best groups yet in the thing, still a lot of testing to do. They shot good at 40.0 grains, opened up badly at 40.5, shot very good at 41.0 (five into 1.125"), then started to spread again at 41.5.

I'm working up 20 at 41.0 and a few at much higher charge wts tonight and will try to get out to 300 with them Monday or Tuesday. Best groups so far though, with the 135s.

 

[Heman]

Re: 135 SMKs and semi-autos revisited, w/questions ...

Sounds to me your hitting different nodes of the bullet. I'd go for the fastest node with safe pressure. To save bullets maybe do a ladder test since your at 300 to see. Since I finally have 300+yds to shoot I did some last weekend with known loads and unknown loads. First time having done one I was impressed at how it works.

 

[Snakum]

Re: 135 SMKs and semi-autos revisited, w/questions ...

Shot five round strings out to 300 yards today, but it was a little windy. The 41.0 load still zeroed at less than 1.25" again and went about 3.75" at 200 and 5.5" at 300. They're quite slow at about 2360fps but are grouping better than anything else and according to JBM they're staying super sonic past 500 yards.

Shot a couple of strings at 42.0gr and 43.0 gr and they just start opening up pretty badly. As is common, I would have three or four rounds grouping very nicely (better then the lower powered loads) and then get one or two wild flyers when every single shot felt good and tight - no called flyers. It's just the way the AK platform is, I guess. Too many moving/flexing parts to expect it to stay tight.

 

[Snakum]

Re: 135 SMKs and semi-autos revisited, w/questions ...

Shot another 50 rounds of the 135 SMKs. I shot them at 100, 200, 250, 300, and 350 and like before they're staying just under or right at 2 MOA for ten. I still get the occasional stellar five-shot group that closer to 1 MOA. But I also still get the occasional wild flyer or two on some strings that otherwise feels perfectly fine but push me past 2 MOA. It's got to be the receiver flexing and/or the scope attachment (side rail). Most likely a combination. So I can either stiffen the receiver by spot welding narrow rails to the inside corners or just call it a solid 2 MOA rifle and be done with it. If I can ring 10" plates with it at 500 yards 75% of the time I'll probably call it done.

That was a lot of work to knock 1/4 MOA off it. I shoulda just sold my bike and bought a PWS 216 or a Larue 308.

But it has been fun learning to shoot a semi and playing with the loads. No wasted time really.