Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Hunting > Long Range Hunting & Shooting

Long Range Hunting & Shooting Nightforce Optics


Reply

God groups but bad ES

 
LinkBack Thread Tools Display Modes
  #1  
Old 03-15-2011, 02:32 AM
Bronze Member
 
Join Date: Jul 2009
Posts: 50
God groups but bad ES

I have a custom built 300 RUM that I had built two years ago that It shoots sub 1/4" MOA from 100 to 700 yards (3 shot groups); however, when I use my chrono, it shows an ES of about 25 fps. Even if I throw out the most extreme velocities, it would still show an ES of 20 fps. What can be causing this?

When I shoot at 750 yards, the groups tend to be slightly more horizontal than vertical.

Here are the specs of my rifle.

Stiller Predator Action
Schneider P5 barrel, 1:11 twist -
5.5 taper, 28"+ Muzzle Break
McMillan A 3-5 Stock
5.5x22x56 Night Force
Badger Rings

Nosler Brass
86 grains of H1,000
Federal 215 M Primers
Berger 210 Hunting VLDs
loaded .020 off the lands
OAL is 3.798 (4.127 with comparator)
2,988 to 3,013 FPS

I measure every load exactly on an older RCBS Balance Beam scale
RCBS rock chucker press
RCBS full length dies and seater

Just as an FYI, I have no problem achieving a low ES when I reload for my friends 300 RUM (6- ES), or my Kimber 300WSM (9- ES); however these guns only average .75" group at 100 yards.

The other thing that is throwing me off is when I last shot at 750 yards; I shot 3 groups that were (1.5") (3.2") (2.5"). When I do the math on my Ipod (ballistic FTE), and figure a 25 fps ES, my bullets should be printing in a 6" vertical group.

I know I should be happy with what I'm getting, but I can't help but think what my 1,000 yard groups would be like if I had an ES of 5?

Where should I begin my search for th cure?

Justin
Reply With Quote
  #2  
Old 03-15-2011, 07:30 AM
Bronze Member
 
Join Date: Mar 2011
Location: N. E. Montana
Posts: 44
Re: God groups but bad ES

2.5" groups at 750?.....mission acclomplished. Throw away the chronograph.
Reply With Quote
  #3  
Old 03-15-2011, 07:45 AM
Bronze Member
 
Join Date: Nov 2009
Posts: 77
Re: God groups but bad ES

^^I agree. But you could try a few loads with some different powder/ seating depth. Shoot groups at 750 without the chrono, and pay attention to vertical spread. What type of vertical spread do the other rifles you load for get?

This is what i do, and my current rifle prints groups with almost no vertical dispersion (1/2") @600yds....
Reply With Quote
  #4  
Old 03-15-2011, 07:51 AM
Platinum Member
 
Join Date: Feb 2007
Location: Townsend, Montana.
Posts: 7,914
Re: God groups but bad ES

Move your chronograph farther away from the muzzle and retest. 18' plus.

Jeff
__________________
Reply With Quote
  #5  
Old 03-15-2011, 09:21 AM
Platinum Member
 
Join Date: Nov 2005
Location: Texas
Posts: 1,844
Re: God groups but bad ES

25 fps is actually marginally acceptable for a sporter. My cut off for competition loads is 15fps. The only thing I question is your shot string. When verifying the final load I always shoot a couple of 10 shot strings to verify my ES.
__________________
The Truth Is Not Always Good For Business!!
Reply With Quote
  #6  
Old 03-15-2011, 09:40 AM
Bronze Member
 
Join Date: Jun 2007
Location: Burlington WY
Posts: 84
Re: God groups but bad ES

I would have to say groups don't lie. Those are good groups for that large of an ES, I would personally question the chrono. Was it a partly cloudy day? I found that most chronographs are very sensitive to light conditions and where the sun is in the sky.
Reply With Quote
  #7  
Old 03-15-2011, 09:45 AM
Gold Member
 
Join Date: Jul 2007
Location: Billings, Mt
Posts: 804
Re: God groups but bad ES

Quote:
Originally Posted by Broz View Post
Move your chronograph farther away from the muzzle and retest. 18' plus.
Jeff
Broz gives good advise.

I think what Broz is saying is that you have to be assured you are not getting any effect from muzzle blast on your chrony.

Heck - set your chrony up at 100 yds if your rifle is shooting like that and then you'll really know what is happening. Use your 100 yd. velocities and play with a ballistic calculator to get your muzzle velocity.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: God groups but bad ES
Thread Thread Starter Forum Replies Last Post
best groups john south Long Range Hunting & Shooting 4 05-04-2009 08:16 PM
Groups??? Bulldog Long Range Hunting & Shooting 8 04-05-2009 07:41 AM
Groups with my .270 remingtonman_25_06 Reloading 5 03-10-2006 01:03 AM
BEST GROUPS Shawn Carlock Rifles, Bullets, Barrels & Ballistics 30 03-23-2005 11:31 PM
BEST GROUPS Shawn Carlock Long Range Hunting & Shooting 0 12-11-2004 07:33 AM


All times are GMT -5. The time now is 06:13 AM.


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