Quick question. I recently bought my first AI rifle. A new AT in 308 (thanks for the great deal EuroOptic). I noticed that there is more internal length in these mag than in the AICS mags. Haven’t reloaded in a few years. Is conventional wisdom still stretching the round out as long as possible within the constraints of the mag? I’ve had some great 308s in the past, and have some decent data from those as far as where I’m going to start with load development, but if anyone was willing to share what they’re using for overall length, or charges of varget for Sierra 175’s, I’m a factory AI-AT 308 with the 24” barrel, I’d love to consider that as well. Thanks!
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AI .308
- Thread starter Dyer_MCSO
- Start date
Loading long to mag length gives you more room for additional powder for additional velocity. So, if that what's appealing to you . . . go for it. I load my .308 long all the time and what fits in my mag may not fit in yours; like I was barely able to get my 177 SMK's into my mag with a COAL at 2.937.
I haven't use Varget in a long time since now my go to powder is AR-Comp for my .308. But when I used Varget, the load that was most consistent for me to push the 175 SMK's was 40.5 grs with a COAL of 2.894 in Federal brass with Fed-210 primers. Out of my 24" barrel I was getting MV's at ~2550 fps.
PS: if you get a chance, you really should try the new 169 SMK's as I find they perform quite a bit better than the 175's.
Additional info of interest:
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I’ll look into those, thanks! The Berger 185 juggernauts and the Sierra 175s were all the rage last time I had a 308. Do the 169s stay supersonic to 1k? As I remember, the 168s did not.
Yep, the 185 jugs were/are great still and the 175 are good but there's these new 169 SMK and 177 SMK's with pointed tips having much better BC. And yes, the 169's stay supersonic past 1K . . . if you got enough barrel and powder to get them there, if you know what I mean.
I’m my AT im running the 168 sierra tmk with an oal of 2.915, cbto is 2.235. I’m my chamber this puts me .030 off the lands. Shoots very well. It also shoots the 175 mk equally well at the standard 2.81.
I use 41.6 grains of ar comp in Norma brass with a br-2 primer for the 168 and 40.3 for the 175. Velocities are 2670 and 2550 respectively. All out of a factory 20 inch barrel.
I use 41.6 grains of ar comp in Norma brass with a br-2 primer for the 168 and 40.3 for the 175. Velocities are 2670 and 2550 respectively. All out of a factory 20 inch barrel.
This is pushed all the way to the lands with a 175gr SMK. The base of the boattail is just about half way up the neck. I like pushing my bullets out as much as the next guy, but that is just too much. I just don't feel the bullet has enough hold on the neck to load it this long. I measured before with the 168gr ELD and it was worse than this. I have another 308 barrel for my AW and it's about the same when I measured it out too.
Hmmmm??? Well, if one is loading to touch or jam the lands, seating with this amount of bearing surface being held is not a problem, and. . .it helps to have enough neck tension to hold the bullet in place.
I've VERY often loaded my cartridges with this amount of bearing surface being held (and I think sometimes a little less) being .010 - .020 off the lands with 175 SMK and others and not had any problems. Your discomfort for doing so, doesn't mean that it's something that can't or shouldn't be done.
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It has been great for me! I started using it when Varget was nowhere to be found and I’m not going back.
