Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Rifles, Bullets, Barrels and Ballistics


Reply

Extreeme spread and tight groups

 
LinkBack Thread Tools Display Modes
  #1  
Old 12-18-2003, 04:23 PM
Junior Member
 
Join Date: Feb 2003
Location: Arizona
Posts: 29
Extreeme spread and tight groups

Hey guys,

The other day I was out testing my favoraite load and come up with 120 FPS extreeme spread. The funny thing is this load will shoot groups in the mid .300's (5 shot) daily. Most of the velocities are very concistent, but 3 out of 10 got me thinking. What will this do at 600 or 800 or even 1k?? Is there something in barrel harmonics that will dictate good groups to 1k despite this 120 FPS differance? There is just a little air space in the loaded case. Is it possible for that little bit to do this? I am not sure what else could make 120 FPS of differance. Cases are matching and weight within 2 grains, bullets and powder are all off the same lot, primers too. All charges are the same and OACL is right on, necks are turned and tension is the same round to round. Should I be looking for a more dense load? Or am I beating a dead horse?

Load is: 308, RL15, Fed GMM primers,178 AMAX, 2.830" 24" BBL

Thanx guys

[ 12-18-2003: Message edited by: 308175 ]
Reply With Quote
  #2  
Old 12-18-2003, 04:29 PM
ktg ktg is offline
Bronze Member
 
Join Date: Aug 2002
Location: Ut
Posts: 69
Re: Extreeme spread and tight groups

I recently had a similar problem. I traced it to neck tension. Just because the cases were neck turned & sized properly didn't mean that the neck tension was the same. When I acutally measured the neck diameter after sizing, it varied greatly. An anhealling job fixed it. Now my extreme spread has dropped to single digits with no other changes.
Reply With Quote
  #3  
Old 12-18-2003, 07:10 PM
Junior Member
 
Join Date: Feb 2003
Location: Arizona
Posts: 29
Re: Extreeme spread and tight groups

ktg,

If I understand what you are saying, you thought your neck tension was right but (when you checked the preped cases) you found they varied?

Before any round is ever loaded the cases are each inspected, including the case necks, inside and out. If any ever do vary, they are dealt with indavidually.

I will pay more attention to the necks on my next reloading session.

Also, I am not sure what "anhealling" is. Help on understanding this would be greatly appreaciated.

Thanx again
Reply With Quote
  #4  
Old 12-18-2003, 08:57 PM
LDO LDO is offline
Silver Member
 
Join Date: Sep 2003
Location: eagle,co
Posts: 251
Re: Extreeme spread and tight groups

annealing is simply heating the case necks up to make brass more pliable[less brittle,softer,more workable].after repeated firings brass gets hard and loses some its ability to spring back.by annealing the cases u level the playing field by making the cases very close to being the same again.its very easily done.are u shooting these at short range?ES doesnt make a real difference at short ranges at long range it can be huge,depending on how far u are shooting,my-2-dave
Reply With Quote
  #5  
Old 12-18-2003, 09:06 PM
Junior Member
 
Join Date: Feb 2003
Location: Arizona
Posts: 29
Re: Extreeme spread and tight groups

Thanx for the info,

I generally shoot at 600 and some at 1k. I havent fired this load at 1k yet.

Thanx again
Reply With Quote
  #6  
Old 12-18-2003, 10:58 PM
ktg ktg is offline
Bronze Member
 
Join Date: Aug 2002
Location: Ut
Posts: 69
Re: Extreeme spread and tight groups

308175, new prepped cases should size the same. If you have a case that has been fired many times, it may have different 'hardness' from work hardening than other pieces of you have. This can cause the actual neck diameter of the sized brass to be different from each other, causing neck tension to vary. The only way to know is to measure the neck diameter after sizing. I had brass that the sized neck diameters varied by nearly .002". After annealing, they varied by about .0003". You should be able to find info on the process by doing a search.
Reply With Quote
  #7  
Old 12-19-2003, 02:36 AM
Platinum Member
 
Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: Extreeme spread and tight groups

308175,

If your rifle will consistantly hold .3's at 100yds, at 600 yards it would be shooting no better than about 11.8" groups from the 120 fps spread alone, no wind.

If it's consistantly shooting better than this at 600, I'd check your chronograph out carefully to see what's wrong with "it", because it won't be holding .3's at 600 yards with some leaving 120 fps apart.

I didn't go back and look, but I think this is a good place to start with annealing info.
http://www.aeroballisticsonline.com/.../bulletsc.html
http://www.cctrap.com/~varmint/arelo.htm#Anneal
__________________
Brent Moffitt
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Extreeme spread and tight groups
Thread Thread Starter Forum Replies Last Post
Trouble shooting tight groups Gota6.5 Long Range Hunting & Shooting 1 02-11-2011 11:03 PM
Extreme Spread Austy Reloading 7 10-25-2010 10:31 PM
Appropriate velocity spread Natty Bumpo Reloading 2 07-06-2008 03:41 PM
Brass fired a few times, how tight is too tight ? Marine sniper Reloading 14 06-16-2008 12:59 PM
Extreme spread Reloading 9 02-07-2005 08:14 AM

Current Poll
How Many Different Cartridges Do You Reload For?
ZERO, all factory ammo - 7.99%
350 Votes
1 - 2.79%
122 Votes
2 or 3 - 14.52%
636 Votes
4 or 5 - 20.37%
892 Votes
6 or 7 - 14.86%
651 Votes
8 or 9 - 8.68%
380 Votes
10 or more - 30.80%
1,349 Vote
Total Votes: 4,380
You may not vote on this poll.

All times are GMT -5. The time now is 01:53 AM.


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