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308w sst advice

11 Apr 2015
@ 03:00 am (GMT)

john feyereisn

I have a savage mod 11 varmint barrel in 308 that shows a very strong liking to varget and 150 nosler ballistic tips. what i found suprising was not the accuracy, but what i did find it interesting how accurate it was with a very wide range of seating depths and charge weights. The ssts i have shot in both 165 and 150gr weights are good, but not quite as good as the balistic tips so far and i would like to tinker with it to improve the ssts. I have a genral range of charge weights that seems to show slight prefrence with the ssts, but would like to revisit exact charge weights and seating deapths.
I also just bought a cronograph, so what to do with this info is new to me. Should i start my attempt at improving it with seating deapths or start by fine tuning powder charge or swaping different primers? Will seating deapths affect velocity standard deviations?

Replies

11 Apr 2015
@ 03:31 am (GMT)

john feyereisn

Re: 308w sst advice
I forgot to mention that one reason i would like to revisit seating deapth is that looking back i may have started a little on the close side at about .015 off the lands. I am planning to back them off a bit more. Has anyone noticed a prefrence as far as seating deapth with this particular bullet?
11 Apr 2015
@ 03:37 am (GMT)

Mike Neeson

Re: 308w sst advice
Hi John, try reading this thread. It might help.
http://www.ballisticstudies.com/Resources/Discussion+Forums/x_forum/18/thread/4756.html

In regard to seating depth, the 308w normally has a long throat so one is normally limited to the magazine length - although I'm not sure on the magazine length in the savage. My magazine is 72mm, so I load to COAL of 71mm for optimum feeding. Please read COAL article by Nathan...
http://www.ballisticstudies.com/Knowledgebase/Determining+COAL.html

Hope this helps.
11 Apr 2015
@ 05:46 am (GMT)

john feyereisn

Re: 308w sst advice
I would have to look at my notes to find the coal measurements but with these bullets in this rifle, i will hit the lands before i will run out of magazine length.
One other interesting comment that someone on savageshooters.com mentioned that had the same model as i do was that he had found that the throat was not as shallow as he thought, it was just tight clearance and when pushing a bullet out of the case towards the rifling, that it felt like the bullet was touching the rifling when it was not, it was just in a bore that was on the tight side. I have no idea how he determined that or if he was a reliable source of information, but I suppose he cant be wrong, ot was on the phone nternet afterall!
11 Apr 2015
@ 05:53 am (GMT)

Mike Neeson

Re: 308w sst advice
The key part to the COAL length article is to provide full neck support to the projectile to achieve good concentricity. The 308 was designed to have a good jump to the rifling to act as an expansion chamber for better velocity/pressure curve.
11 Apr 2015
@ 04:01 pm (GMT)

Bryan Webster

Re: 308w sst advice
It is also possible the sst bullets are not what the barrel likes.
I found (my surprise) the 168 and 178 grain Hornady A-Max bullets were a
significant improvement in precision in my .308. I did not bother too much about trying to seat close to the lands, allowing magazine length to guide my efforts, but found 3/8 inch 5 shot groups to be just fine with COAL of 2.80 in my Remington 700P LTR with heavy 20 inch barrel.
 

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