Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Reloading

Reloading Techniques For Reloading


Reply

Disappointing 308 MV.......and......which powder in Lapua factory 308?

 
LinkBack Thread Tools Display Modes
  #8  
Old 03-23-2005, 03:12 PM
Silver Member
 
Join Date: Mar 2004
Location: scotland
Posts: 174
Re: Disappointing 308 MV.......and......which powder in Lapua factory 308?

hi matt

if your atmospheric conditions are measured accurately, and you can get me your height above sea-level, i'll plug it all into exbal for you and send you a drop table..... if you could get to a range and measure the actual drops further out, i could plug them in and it would adjust it accordinlgy for you.....

cheers

derek

ps, where did you get your aci and how much was it?

ta
Reply With Quote
  #9  
Old 03-23-2005, 04:15 PM
Gold Member
 
Join Date: Sep 2003
Location: Blighty
Posts: 638
Re: Disappointing 308 MV.......and......which powder in Lapua factory 308?

Derek,

Thanks, I've spent all afternoon mulling this over in the back of my mind, waiting for the flash of inspiration.

Just spent 1hr fudging every variable (given a fixed 2722fps mv rather than the fudged 2580 I've been using) tried messing with pressure, alt, scope height, retard value, BC etc [img]/ubbthreads/images/graemlins/crazy.gif[/img] in order to try to match field observations. No success, only 2580 mv puts me in the parish [img]/ubbthreads/images/graemlins/mad.gif[/img]

Until, literally 10min ago, it occurred to me that the S&B might not be giving me spot on 10mm clicks. What if they were, say, 9mm clicks?

I just input a formula that divides my 1cm click values by 0.9, and lo and behold, at an mv of 2722 I am firmly in the parish! 0.88 seems closer yet.

This will need a bit more investigation, but I think this may be EUREKA

PS I'll drop you an email regarding the ACI
Reply With Quote
  #10  
Old 03-25-2005, 04:30 PM
Gold Member
 
Join Date: Sep 2003
Location: Blighty
Posts: 638
Re: Disappointing 308 MV.......and......which powder in Lapua factory 308?

Derek,

Popped out yesterday just for a check-sanity plink. Didn't have the space to put up a long range target, but stuck one up at 134m and another at 248m. Dreadful condition, wind all over the place; couldn't get under 0.5moa but, my comeups were on the nose. So.....here's the weird bit:

Previously, to match my field trajectory observations, I plugged 2580fps with a scope click value of 1cm into my ballistics prog,

Now that I know the rounds are actually doing 2722 there is no 'normal' data fudge (ie BC changes etc.) that will allow predicted data to match my field observations. But..

If I plug in the actual MV of 2722fps but with 0.87cm clicks, the predicted data does match my field observations!:

The comeup values remain within half a click out to 700m!

.....Now I have to think of a way of measuring my scope click values to confirm this solution [img]/ubbthreads/images/graemlins/frown.gif[/img]
Reply With Quote
  #11  
Old 03-27-2005, 11:58 AM
Silver Member
 
Join Date: Nov 2003
Location: La Grange, TX
Posts: 222
Re: Disappointing 308 MV.......and......which powder in Lapua factory

Watching and reading this thread.

I was as involved as you are on a bit of a different subject. Let me try to help save your sanity.

I am being totally serious. It was suggested before also. Just go out and record conditions and record the actual impacts at distance.

Who cares why what how etc...... There are going to be so many variables involved it'll drive you nuts. And there is no reason to wonder.

The one thing I would have to know is the clicks on the scope though. Just do a few tests to figure it out. NOT how it matches your data so much as how much physical movement it gives.

Other than this, life is too short, Jeff
__________________
Get as close as you can, but utilize your skills as needed.
Reply With Quote
  #12  
Old 03-29-2005, 08:14 AM
Gold Member
 
Join Date: Sep 2003
Location: Blighty
Posts: 638
Re: Disappointing 308 MV.......and......which powder in Lapua factory

Jeff,

Wise words!

Trouble is, because I'm afflicted with 'ballistics-nerditry', I have to know! [img]/ubbthreads/images/graemlins/smile.gif[/img]

Checked the tracking on the scope. It's giving spot on 1cm clicks. Maybe the 'fudge' I was looking for to match real world to program modelling was simply to input a false scope click value -time will tell!
Reply With Quote
  #13  
Old 03-29-2005, 03:53 PM
Silver Member
 
Join Date: Mar 2004
Location: scotland
Posts: 174
Re: Disappointing 308 MV.......and......which powder in Lapua factory

maybe the ballistics program is using the wrong drag function for the style of bullet. a g1 is the norm but does not represent boat tails all that well. hopefully someone who know more than me will chip in here?

how accurate is your chrono too? have you tried testing it with subsonic match ammo to see if it is in the ball park?

come back to me about your trajectories, were they in metres or yards? is the drops in inches or cm, and are your adjustments on the scope in moa, cm, inches or clicks?

cheers

delboy
Reply With Quote
  #14  
Old 03-30-2005, 12:15 AM
Gold Member
 
Join Date: Sep 2003
Location: Blighty
Posts: 638
Re: Disappointing 308 MV.......and......which powder in Lapua factory

Hi Derek,

I'll blip you an email.

I 'calibrated' the chrono with the known value Lapua factory ammo shown above; it clocked spot on the factory claimed mv.

I've played with all the drag functions and retard coefficients. No combinations model the trajectory accurately.

The only fudges that get me in the parish are: Fudge MV to 2580; or fudge scope clicks to 0.87cm
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Disappointing 308 MV.......and......which powder in Lapua factory 308?
Thread Thread Starter Forum Replies Last Post
338 Lapua Factory Ammo Hntbambi Long Range Hunting & Shooting 5 08-18-2010 09:09 PM
FS- Brass, Bullets & Factory Ammo + Redding 3BR Powder Measure laver Reloading Equipment and Components 0 07-22-2009 05:10 PM
Which powder in Hornady Factory Ammo northernchris Reloading 7 12-05-2007 11:21 PM
Powder in Lapua 308 Factory Target Ammo. Brown Dog Reloading 1 12-23-2006 09:29 AM
Remington factory powder/bullets????? *WyoWhisper* Rifles, Bullets, Barrels & Ballistics 0 11-20-2001 03:22 PM


All times are GMT -5. The time now is 08:33 PM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC