Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Group size vs ES/SD?

  1. #1
    Site Supporter ccmdfd's Avatar
    Join Date
    Feb 2011
    Location
    Southeastern NC

    Group size vs ES/SD?

    Got a 280AI earlier in the year. Wanted something with a little more reach than my 7mm-08 for deer, and possibly larger critters, but without getting into magnum territory. Chose the Barnes 139 LRX as my bullet of choice.

    Choose H4831SC as initial powder because; 1 had some around from reloading a relative's 6.5PRC, 2. it's temp stable, and 3. Online reviews are very positive for it in the 280AI. Following Barnes' rec's, i seated 0.050 off of the lands and worked my way up from 57gns to 63.3 max. The 63.3 is listed as a compressed load but i found i was getting compression at 60-61 gns. In fact, at 63.3 I couldn't seat the bullet to the recommended depth. So i backed off on the powder charge.

    I shoot 3 shot groups, then let the gun cool for 10 min, then repeat until i get to 18 shots, then analyze the set.

    I found this to be an accurate loading with groups of 0.6 to 0.8 in at 100 yards. However, my chrono is telling me i've got velocities around 2940 but with an ES of up to 70 and an SD of 20. Played around with the depth and charge weight a little and will say the group sizes have stayed very consistent, no changes at all, but best i've seen on the chrono is ES of 40 and SD of 14.

    Question 1: Am I right in thinking that even with a tight 100 yrd group, those large ES/SD's will lead to problems if I stretch the range out?

    So happened on some Hybrid 100V, which is listed as using less case capacity. Sure enough, even at max charge and 0.05 off of the lands, no compression at all. Took it to the range and got MV of 2950, but now with ES of 20 and SD of 6. Yay! Unfortunately, my groups opened up to 1.1-1.2 inches at 100.

    Question 2: What's best next step? Keep with Hybrid (and lose temp stability) and work on seating depth and see if I can tighten those groups up? Or go back to 4831SC and see if i can keep the tight groups but do something else to tighten up the velocities? Other ideas?

    Thanks
    cc

  2. #2
    Member
    Join Date
    Oct 2011
    Location
    Asuncion, Paraguay
    At what range are you planning to hunt?

    The group size depends mostly on the harmonics of your barrel/rifle with a given load, and unless the SD is really large this is secondary.

    A larger SD/ES does open up the groups at long range, but I would say you won't notice inside 600 yds or so. You can play with a ballistic program and see the difference in drop and wind drift at X distance with different velocities.

  3. #3
    Site Supporter ccmdfd's Avatar
    Join Date
    Feb 2011
    Location
    Southeastern NC
    Quote Originally Posted by TiroFijo View Post
    At what range are you planning to hunt?

    The group size depends mostly on the harmonics of your barrel/rifle with a given load, and unless the SD is really large this is secondary.

    A larger SD/ES does open up the groups at long range, but I would say you won't notice inside 600 yds or so. You can play with a ballistic program and see the difference in drop and wind drift at X distance with different velocities.
    If I can get this thing to go out to 600 I'd be perfectly happy.

    I will look at those ballistic apps and see what they say.

    Thanks

  4. #4
    Quote Originally Posted by ccmdfd View Post
    Got a 280AI earlier in the year. Wanted something with a little more reach than my 7mm-08 for deer, and possibly larger critters, but without getting into magnum territory. Chose the Barnes 139 LRX as my bullet of choice.
    ***
    Question 1: Am I right in thinking that even with a tight 100 yrd group, those large ES/SD's will lead to problems if I stretch the range out?

    So happened on some Hybrid 100V, which is listed as using less case capacity. Sure enough, even at max charge and 0.05 off of the lands, no compression at all. Took it to the range and got MV of 2950, but now with ES of 20 and SD of 6. Yay! Unfortunately, my groups opened up to 1.1-1.2 inches at 100.

    Question 2: What's best next step? Keep with Hybrid (and lose temp stability) and work on seating depth and see if I can tighten those groups up? Or go back to 4831SC and see if i can keep the tight groups but do something else to tighten up the velocities? Other ideas?

    Thanks
    cc
    Consistency is the key to low ES/SD and you have to isolate the variables in your hand loading process. A couple of quick thoughts, that come to mind. First, I would start with the chronograph. Are you using a quality chronograph that is consistent, like a magnetospeed? Were you done fire forming the ackley brass? going to see some extra ES/SD when you are still fire forming shoulders. Much harder to get consistency when you are shooting a compressed load.

    I have not had good luck with Hybrid 100v... ever. Looking at barnes reloading manual for that weight bullet they report IMR4350 as the most accurate. I would try H4350 for the temp stability. Shoot a ladder over the chronograph and find the node then play with seating depth.

    If it is a hunting rifle I would not go too crazy chasing ES/SD. I don't know the barrel life on 280AI but I would not go crazy with it.

  5. #5
    Site Supporter ccmdfd's Avatar
    Join Date
    Feb 2011
    Location
    Southeastern NC
    Quote Originally Posted by Jimichanga View Post
    Consistency is the key to low ES/SD and you have to isolate the variables in your hand loading process. A couple of quick thoughts, that come to mind. First, I would start with the chronograph. Are you using a quality chronograph that is consistent, like a magnetospeed? Were you done fire forming the ackley brass? going to see some extra ES/SD when you are still fire forming shoulders. Much harder to get consistency when you are shooting a compressed load.

    I have not had good luck with Hybrid 100v... ever. Looking at barnes reloading manual for that weight bullet they report IMR4350 as the most accurate. I would try H4350 for the temp stability. Shoot a ladder over the chronograph and find the node then play with seating depth.

    If it is a hunting rifle I would not go too crazy chasing ES/SD. I don't know the barrel life on 280AI but I would not go crazy with it.
    I actually have some H4350 lying around.

    Funny that both H4350 and IMR4350 are on the 280 Rem list, but only IMR is on the AI list.

    Same starting weight for H4350 as listed for IMR?

    Thanks

  6. #6
    STAFF Hambo's Avatar
    Join Date
    Aug 2014
    Location
    Behind the Photonic Curtain
    Quote Originally Posted by ccmdfd View Post
    If I can get this thing to go out to 600 I'd be perfectly happy.
    The stock answer is to start shooting groups at longer ranges and see what happens for real.
    "Gunfighting is a thinking man's game. So we might want to bring thinking back into it."-MDFA

    “It worked pretty good if you could shoot.” -Pat Rogers

  7. #7
    Quote Originally Posted by Hambo View Post
    The stock answer is to start shooting groups at longer ranges and see what happens for real.
    Yes. Sometimes things don't matter until they do. The best path for you IMHO would be actual testing at the ranges you intend to shoot. We've already seen that low ES & SD are not affecting your accuracy at 100 yards, so I'd take it out and stretch its legs a bit at a time to see how long grouping remains acceptable.
    Malo periculosam, libertatem quam quietam servitutem
    I prefer the tumult of liberty to the quiet of servitude
    -Thomas Jefferson
    I prefer dangerous freedom over peaceful slavery.

  8. #8
    Member
    Join Date
    Jan 2015
    Location
    OKC
    For serious groups, three shot groups are not the way. Five at least. Years ago Snipers Hide had a rule you could not post three shot groups.

  9. #9
    STAFF Hambo's Avatar
    Join Date
    Aug 2014
    Location
    Behind the Photonic Curtain
    Quote Originally Posted by Eric_L View Post
    For serious groups, three shot groups are not the way. Five at least. Years ago Snipers Hide had a rule you could not post three shot groups.
    If he's got a light contour barrel, three is probably all he's going to get. I had a .280 Remington Mountain rifle that would start stringing shots after three rounds.
    "Gunfighting is a thinking man's game. So we might want to bring thinking back into it."-MDFA

    “It worked pretty good if you could shoot.” -Pat Rogers

  10. #10
    Site Supporter ccmdfd's Avatar
    Join Date
    Feb 2011
    Location
    Southeastern NC
    Quote Originally Posted by Eric_L View Post
    For serious groups, three shot groups are not the way. Five at least. Years ago Snipers Hide had a rule you could not post three shot groups.
    Quote Originally Posted by Hambo View Post
    If he's got a light contour barrel, three is probably all he's going to get. I had a .280 Remington Mountain rifle that would start stringing shots after three rounds.
    Yeah, I haven't tried ringing a five shot group out of this gun yet to see what it would do. It has a carbon fiber wrapped barrel, they seem to be all over the place with what they do in my experience.

    But I have had several rifles for hunting that have very thin barrels and shot number four and five would be nowhere near shot number one two and three. Those lightweight barrels just won't hold a group that big. But that's also why I shoot a multitude, several three shot groups. I often will do 18 and sometimes even go above 20 before making an assessment of what the gun is doing.

    Plus this rifle only holds three so I'm never going into the woods with more than that.

    Heavy, bull-barreled Target rifles, completely different animal.

User Tag List

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •