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Working on 308 Win load - Help!

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8shots View Drop Down
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    Posted: August/25/2008 at 04:31
I am shooting with a Rem 308 VSF. The twist is 1 in 12. The throat seems to be very generous or out of spec, as at only 2mm of the bullet in the case neck (at 73mm OCL), I am not touching the lands.
So, I will first post a serious of targets at 47gr powder and varying seating depths. The best (69mm) is still not good enough. All shots with 155 gr Sierra Matchking at approx 2800 ft per sec. I think personally that the 155 gr is to heavy for the 1 in 12 twist, or that 2800 ft per second is to slow. However increasing the powder made the grouping worse.
 
I paste targets in increasing bullet OCL.


Edited by 8shots - August/25/2008 at 09:28
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pyro6999 Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 05:54
i would try different seating depths and different powder before i did anything else the 1:12 twist will handle bullets all the way to 180gr down to 140gr so your fine there, try some other powder the bullets are going to be accurate they are  sierras so i wouldnt blame them just yet.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyborg Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 07:30
I have a tendency to think that the freebore may be a tad out of spec. Check it and see how much there is. The 83 OCL is a bit strange to me for a .308 you'd think that the lands would be there somewhere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:20
OK, somebody help me out here? make sure my math is right!!!  83mm/25.4= 3.2677 inch WOW   OAL for .308 155gr A-max is 2.735 inches.  2.735X25.4=69.469mm  So the longest I'd go is 74mm or 75mm max. 
8, do you have any 168gr bullets to try out maybe yours doesn't like 155gr bullets, (almost unheard of) or can you get some Varget powder. I know you probably like using home grown businesses but I have never used S431 powder.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:30
Originally posted by Steelbenz Steelbenz wrote:

OK, somebody help me out here? make sure my math is right!!!  83mm/25.4= 3.2677 inch WOW   OAL for .308 155gr A-max is 2.735 inches.  2.735X25.4=69.469mm 


That is what I was just thinking after I done the conversion.  Max mag length is about 2.865.  I thought mine was deep and it was 2.935.  That is insane if you measured that right. 

If it really is that far out, it might be worth taking it to your smith and having the barrel cut and rechambered.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8shots Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:31
Sorry Steelbenz, I have seen my typo error and fixed it. Should be 73 mm.
69mm= 2.716"
70mm=2.755"
73mm=2.874"
75mm=2.953"
 
S341 is our Somchem local powder and all that is available. It is a medium burning ball powder.


Edited by 8shots - August/25/2008 at 09:31
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:37
Ah, that is actually not bad at all for a factory remmy gun.  A lot of them are over 2.9. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:46
OK, stay with the 69mm OAL and play with your charge, are you seeing any sign of high pressure?  I'd back it down to 45.5,46, 46.5 and see if you get some tighter groups.  Do you have access to a chronograph? To get a real picture about whats going on.  If you can get as much info as possible then make a good call on the load. How many round have gone through this weapon, maybe you need to shoot it in?  Just a suggestion!!! Hope I have given you something to think about anyway, hope it helps more than muddles the water more!!!!  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:49
Tornado siren going off, gotta go.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8shots Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 09:54
Thanks Steelbenz. My approach is this. One more check on 69,5mm and one on 68,5mm.
I have tried the lower powder weights without success.
It seems to be around the 47gr and 69mm OCL. The amount of freebore worried me, but it seems from the feedback that is how it is. I am used to being just a thou or so off the lands, but not with this one.
I also have a Timney trigger which I will fit. It may just give me a little better release.
I also thought I would get the load right and then chronograph, as I have to borrow one. According to the reload data sheet I must be around 2850 . So I do not want to move downwards in load. At 48gr of powder the group spread out again, the bolt also felt tight, so I think I 48gr is at the top end.


Edited by 8shots - August/25/2008 at 09:56
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 10:05
You don't just want to go for the fastest you can get, that always sounds great to have more speed but is not always the most accurate way to go.  You need to find the accuracy node for your barrel.  Maybe with those bullets it is only 2750 or 2700.  You never really know until you load a whole bunch of different loads and shoot them all while chronographing them.  You have to find that speed where the harmonics of your barrel is the best.  Meaning that particular speed will whip your barrel less and result in better accuracy. 

I found with my VS and 175 grain SMK that right at 2600 my accuracy was very good.  Less than 1/2 MOA.  But if I pushed them a little harder and hit 2650 then I was around 1 MOA.  WIth the 168s it was around 2660 and at 2700 if dropped off again.  So every barrel/load is different and in order to find that accuracy node you really need to play with a lot of different loads and use the chronograph to discover it properly.  Or at leasat more easily and accuratly. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 10:05
Cool, somebody with the county got a quick trigger finger!!!   LOL
We have a few light storms blowing thru right now, no big deal.  OK that sound good to try also.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 10:07
Yes a chrono is a great tool. without it your really just guessing!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 11:42
Can you get ahold of any 168gr. Federal Gold Medal ammo? That should shoot well enough for you.  
 
If I could get you a pound of Varget and some 168gr. SMKS, you would be a very happy Optics Master!! Wink
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 11:43
Originally posted by Steelbenz Steelbenz wrote:

Cool, somebody with the county got a quick trigger finger!!!   LOL
We have a few light storms blowing thru right now, no big deal.  OK that sound good to try also.

 
Miss Fay headed our way now, Mike.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: August/25/2008 at 12:03
B'ham area is getting its share for today and yes we can use it too.  Also a good reason not to cut the grass today.  Other than I'm just being lazy this Monday.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8shots Quote  Post ReplyReply Direct Link To This Post Posted: August/26/2008 at 07:31
Keep your head down. Hope you all Ok with the storms in your area.
 
Our weather is not to bad this side, so I managed to put some more rounds down range.
Seems 47gr powder S341 and 69mmOCL is giving a reasonable result. I tried slightly longer and shorter OCL and slightly up and down on powder range. All are there or there about. I will now try different components. Some Lapua brass and flat based bullets.
I also fitted the Timney trigger. It is not a hair trigger, but a think trigger. You just think of the shot and it goes off! I love it!!!
 
 
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Longhunter Quote  Post ReplyReply Direct Link To This Post Posted: August/26/2008 at 09:32
Ditto SteelBenz's suggestion.  I would try some 165 to 168 grain bullets.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8shots Quote  Post ReplyReply Direct Link To This Post Posted: August/26/2008 at 10:07
Ok thanks for your help. I am going to try other bullet weights etc and will let you know how it worked for me.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: August/26/2008 at 11:52
Looking good!!
That trigger swap looks like it helped you out. I too like Timney triggers and the OLDER Remington triggers tuned.   
 
Tip asked on your other thread, but I assume you have the X-Mark Pro trigger? Why does damn near everybody say they suck?  
Nobody around here likes them, that I know to be true.  
 
Whats your round count now, 8?
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