Consistancy in zero

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by jmbn, May 1, 2003.

  1. jmbn

    jmbn Active Member

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    I've got a 25-06 that I've been using for close to 30 years that shoots 3/4" groups all day long, but any difference in temperature will put the group into a different zero. I've got a 270 and a 7mm Rem mag that are very consistant in this regard, as was an earlier 7 mag, and is my buddie's 270.

    Have any of you come up with a logical reason for this? I have a Ruger #3 that has never shot well (unlike two #1's that I have)and I've decided that rebarreling it would be a worthwhile project as soon as I can make up my mind as to what caliber. Most of my deer hunting is out of a backpack so I don't want anything really heavy; a good honest 500 yard rifle will do fine. I'm leaning towards a 270 Weatherby, simply because I don't have one, and it will do what I want in terms of velocity, but I'm concerned about consistancy as mentioned above. Dan Lilja recommends the 270 Weatherby but he believes that one cartridge is not more consistant than any other, and that my experiences with the 270 and 7 Rem mag are simply co-incidence

    Any comments on this? I've been reloading and putting together custom rifles since the 222-250 was a wildcat and I'm reasonably knowlegable for a stupid amatuer.

    jmbn
     
  2. Boyd Heaton

    Boyd Heaton Well-Known Member

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    If I were you I would give a strong look at the 270 or 7WSM......We have taken deer out to 750 yards with a STOCK Win M70 Coyote out of the box 270WSM shooting 135gr MatchKings at 3200fps..
     

  3. Brent

    Brent Well-Known Member

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    Everything I been seeing with the 6.5wsm lately, man I'd jump on one of them in a heartbeat if even considering what you are. It is absolutely amazing at the 30" barrel length, the Ruger still would be real short with a 30 or 32" bbl too and 3250-3300 fps with a 140 is real doable at under 65k psi, I can tell you that much. Something you might look into. [​IMG]

    S1 has a good bit of experience with this wildcat too.

    The POI shift in cold weather is something I haven't noticed, but it could be the powder is temp sensitive? You didn't say which one you'd been using. The Hodgdon Extreme line of powders are probably the best, although the Reloader 22 and 25 I've been using alot of have been outstanding too.
     
  4. jmbn

    jmbn Active Member

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    I've been using H4831 in all three rifles mentioned. I wasn't aware of the "extreme" powders until recently, and I assume that they are recent changes in Hodgen's powders, so I'm definately using information taken over many years. Why the WSM's? I notice they all have short necks. One of the things I like about the 270 Weatherby is the long neck, and it follows that the short neck of the 7 Rem mag is something I DON'T like.

    Obviously, I'm relating the changing zeros in different temps with pressure differential.

    I go elk hunting in CO in the late season, which is in early November. I always stop at a place just off the paved road and check zeros. My 7 mag is always right on, and my improved 35 Whelen is always three or four inches off. When I get back home, it's right on again.

    I'll try the Extreme powders; you guys might be on to something there. I hope. Thanks for your help.

    jmbn
     
  5. MAX

    MAX Well-Known Member

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    There are some details missing about your quandry with the 25-06 but I assume you're talking about cold barrel group shift. I'd be looking at the bedding and or fore end warp pressing upon the pressure pad differently as the temps change. I'd guess that barrel stress could cause it but think that would show up more during a string instead of between different groups.
     
  6. Brent

    Brent Well-Known Member

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    The short mags do have short necks, especially the 7mm. The Ultra mags are the same damn way too.

    One has to consider the throat errosion this causes, and may want to increase the neck length considerably to quelch it.

    This means form dies and custom reamer, so price gets up there quick like.

    Around .400" neck length in a fairly sharp shoulder 35-40 degree, will end the massive throat errosion problem... I'm told by a few now.
     
  7. Mysticplayer

    Mysticplayer Writers Guild

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    JMBN, is the stock on your 270 Wood? My guess is that the stock is warping and moving your POI. Free float the barrel and this problem will go away. Good bedding helps too.

    As to the Extreme powder, I am a big supporter for hunting. Living in Canada, I see big swings in temp during a day. Conventional powders will vary up to 3fps per deg of F change. That means a load can easily vary by 100fps in my climate. This affects POI, accuracy, drop. By using Extreme powders, I have found my POI to not shift from summer to winter. Vel. are consistent too. Great stuff.

    My favorites are the H4350, H4831SC and Varget. Using CCI BR2 primers, I get 1/3 MOA or better from "hunting" rifles.

    As to sugg. for a new cartridge, I too would lean towards the 270WSM in this calibre. Great performance and longer effective barrel length. Throat wear should be lower then the WBY too.

    If choosing any cartridge, then I would look at the 6.5 cal and 7mm, simply because there are so many great bullets to choose from.

    I have had excellent success with the Hornady SST for accuracy and BC. Tougher then the Nosler BT too.

    Good luck with your new projects.

    Jerry
     
  8. jmbn

    jmbn Active Member

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    Jerry Teo- It's my 25-06 that is the one in question, and yes, it's a wood stock; I made it years ago, but I have rebedded it a couple of times over the years. Wwhen I moved from Newport Beach, CA (hi humidity), to Sacramento (dry) I rebedded all my stocks, and they all needed it. The 25-06 is a Mauser action and I bed them only on the back side of the recoil lug, the flat just behind the lug, around the tang, and about the first inch of the barrel. I always bed my rifles in a completely relaxed position, by holding them in position with masking tape while the epoxy goes off.

    The 270 that you asked about is a 700 Mountain Rifle in original wood stock, but I pillar bedded it before I shot it. The barrel is completely free floating. The 7 Rem mag is in a glass/ carbon stock that I made myself, and is bedded like the Mauser.

    I don't think the problem is bedding. Could be that it's cartridge specific, but it might be connected to other things, like barrel vibration, but this should be controlled by barrel length and weight, as well as by bedding. Someone else on this forum, talking about something else, talked about bracketing loads and watching velocity spread in the interest of consistancy in accuracy. I think I'll play with that.

    Thanks for the input.

    jmbn