308 load out of short barrel ar

[GhengisAhn175]

Guys been searching the 308 loads but the best I can find that matches my rifle profile is a 20".

I'm running a 16.5" barrel 1:11 twist and was looking for powder. Was suggested 4064 but couldn't find someone else on the hide using it for a short barrel ar .

Anyone have suggestions?

Shooting 175/190 smk


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[dmike]

Tag. Same boat except 1:9.5.

Just started load dev, promising results with 3031 but pretty slow. Also trying norma, accurate, vv, hogdon.

175/4064 @ 42.0 was right at moa at 380 yards with mixed brass and tula lrm primers (mv was 2420ish, on par with FGMM. I'll run it again with better brass and fed210.

190s in progress.

 

[Cornholeo]

18" GAP-10 likes the 4064 over Varget using 175SMKs in Lapua brass. 2.8 COAL using CCI BR2s

 

[GhengisAhn175]

308 load out of short barrel ar

Thanks corn got any idea on FpS or height deviation at 200-300 yards?

And grains? Assuming high 42's

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[Cornholeo]

The little bit of Chrono time I had with a buddy it was ~2631 I believe as that is what I have in Strelok app. I am using 42.0gr of IMR 4064.

This seems to go with Dan Newberry's data on the load combination that I stumbled across on the internet, the low node. I do want to get out and try his OCW method to find the high node as well. A friend helped me with this when I first started with the rifle and reloading. It has been accurate and the 4064 is a hell of a lot easier to find...for now.

Hope this helps.

 

[Rancid Coolaid]

Working now on 4064 loads with 150 soft points now out of my 16" 716 Sig.
Will let you know shortly.

 

[GhengisAhn175]

Thanks for the input fellas. I got
8# of 4064 and will try it out. I was just wanting to make sure I'm buying the right powder for the barrel length and burn time.

I suppose I'll start at 42 grains and work up a load.


Anyone know how different I would be in a 20" barrel?


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[dmike]

Thanks for the input fellas. I got
8# of 4064 and will try it out. I was just wanting to make sure I'm buying the right powder for the barrel length and burn time.

I suppose I'll start at 42 grains and work up a load.


Anyone know how different I would be in a 20" barrel?


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GhengisAhn, since you said you were also running 190s: for velocity reference 41.6gr 4064 got the 190SMK to 2400fps in my 16". I believe the IMR data says I've got 2 grains more to play with before max so I'm working up to find an accuracy node.

With the 175s, it took 42.8 to break 2500fps, that wasn't grouping but maybe there's something in the mid-43s. The way I read the IMR data it looks like max is at 45 but I know most people run well below that.

 

[GhengisAhn175]

Thank dmike! Don't have access to a chrono ATM so looking for close to ideal #s and working up micro loads up.


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[dmike]

Thank dmike! Don't have access to a chrono ATM so looking for close to ideal #s and working up micro loads up.


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The FGMM 175s are doing well in the 16", easy 3/4 MOA. Prochrono says MV is about 2525 after a good cleaning.

I can't get 190SMKs and 4064 to group yet. I had a Federal 210 primer blow at 41.4gr (2380FPS) and 42.3gr (2415FPS), COAL 2.80. The brass was SWA and the primers went in a little too easily. It looks like IMR shows max at 43.7 with 2.74 COAL so I figured I'd be good.

I had very promising results yesterday with 41.2gr of 3031 behind a 175SMK, it shot about 1/3 MOA at 380 yards (210 primer, new SWA brass, 2.80 COAL). M/V was around 2470. 41.0 was not good at all though. In terms of OBT I'm wondering if the shorter barrel makes the nodes closer together?

 

[dmike]

Let's say "hypothetically" I have this friend who is *allegedly* wanting to try 220 SMKs in his 9.5 twist 16" piston AR-10. N150 powder, maybe starting at 36gr and working up slowly to find 2100fps but not exceeding 39gr. Assuming they fit in a mag, why not? No QL so not sure what kind of pressures we're talking about but based on some hasty calcs:

220 SMK
G1 BC .6 (advertised)
MV 2100
Muzzle energy: 2154 ft-lb
1185fps/685 ft-lb @ 900 yds
1100fps/595 ft-lb @ 1000 (subsonic)
1025fps/510 ft-lb @ 1100


175 SMK
G1 BC .49 (advertised)
MV 2500
Muzzle energy: 2430 ft-lb
1260fps/620 ft-lb @ 900 yds
1150fps/520 ft-lb @ 1000 (trans-sonic)
1050fps/430 ft-lb @ 1100

What am I missing here?
for all you VV haters N150 is supposed to be on par with RL17 for burn rate so unless you want to send me some of your RL17 or powerpro 3000 it's going to have to be n150. Seems like a good compromise given the short barrel

 

[dmike]

Nobody? 220gr out of a pof p308, why not?

 

[ArmyJerry]

You guys should mention your brass with the load data as there can be 1.5+ grain plus variation of powder to brass differential to get the same or similar velocities.

 

[GhengisAhn175]

308 load out of short barrel ar

Just an update to my load development.

1. Mixed brass.. (I know not precision right?)

43.4 grains gave me very good groups. 43.6 was also close but not as good as .4 (1/2-3/4 "). That's good enough for government work for me

175gr smk
2.870" COAL
43.4 gr imr 4064
210m primers
Mixed brass

 

[Thebelly]

16" Larue PredatAR here.

41.8 gr IMR 4064
175 SMK
Rem 9 1/2 Primer
Fed Brass


With suppressor:
41.6gr IMR 4064
175 SMK
Rem 9 1/2 primer
Fed Brass

 

[GhengisAhn175]

Guys with my 43.4 load I'm barely breaking 2k fps. What gives? Confused ...

 

[ZombieMonkey]

Guys with my 43.4 load I'm barely breaking 2k fps. What gives? Confused ...

I'd chrono another known good load like FGMM and verify that your chrono wasn't off. 2k FPS doesn't sound right with that charge weight, would make me think that maybe that powder is a bit too slow for that barrel length and you're not getting a good full burn. Something seems off with that velocity though.

 

[GhengisAhn175]

Roger this will try.

I did with the same conditions sand standards, get 2799 average for my 260 remington with 42.0 h4350.

And I did expect around 2700 (100more fps was surprising )

I picked imr 4064 For the short barrel! [emoji35]

I don't think going up in charge should be the answer so I guess I'll try the fgmm

 

[GhengisAhn175]

Would I get less/more fps if I seated too far/too close?

 

[GhengisAhn175]

Bump for an answer