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Overbore???

 
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  #8  
Old 07-03-2003, 08:51 PM
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Join Date: Jul 2003
Location: PRcal
Posts: 22
Re: Overbore???

Chris,

Thanks for the info. I'm now considering 338 lapua. I always thought that they were a much higher pressure cartridge & worried about blowing up the Rem 700 action.

The more you guys teach me, the more expensive my next rifle is becoming. I can now appreciate the "ignorance is bliss" saying.

Thanks again.

Chris.
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  #9  
Old 07-03-2003, 09:42 PM
 
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Re: Overbore???

We have shot the Sierra 77's past 800 yards near sea level. 7 twist.
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  #10  
Old 07-03-2003, 11:13 PM
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Join Date: Apr 2003
Location: Newburgh NY
Posts: 235
Re: Overbore???

I hear 3030fps is the magic number for 1000yd 223. When I work it out on my ballistics program 2900fps will have the bullet at 1152fps at 1000yds. I would say the extra 130fps is an insurance policy. If I were you I would prefer to shoot Berger or JLK or Hornady rather than Sierra. I have had excellent performance from the Hornady bullets from 75gr and down. My Colt will not stabilize an 80gr bullet due to it being a 1:9 twist. If your rifle has a 1:7 or 1:8 twist then the heavier bullets are for you. The powder to use for this achievement is is vv540. I use blc2 with the 68 and75gr hornady bullets but cannot get near the magic velocity for 1000yds. There are a few drawbacks to vv540. One is that guys rip case rims off and another is broken extractors from this powders slower burn curve cycling the action too hard!!! I have only shot critters out to between 5-600yds with my223. It is great for head shots on deer at those distances. What kind of 223 do you have? Mine is the 24" stainless barrel Colt elite HBAR 6724. Tis a fine shooting iron!!!
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  #11  
Old 07-03-2003, 11:23 PM
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Join Date: Jul 2003
Location: PRcal
Posts: 22
Re: Overbore???

Hbar,

I've got a Rem LTR w/a 20" bbl. I think it's a 1/9. Doubt I'll be able to make that velocity w/a 77gr bullet. Does really good w/the 69 MK & just ok w/52's. Haven't tried the heavier stuff yet, but will soon.

Thanks.

Chris.
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  #12  
Old 07-03-2003, 11:55 PM
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Join Date: Jul 2003
Location: PRcal
Posts: 22
Re: Overbore???

Thanks Chris.

I'm really starting to get interested on 1000 yard + shooting & .308 win in a 26" barrel isn't working as well as I had hoped. I know the 338 lapua has a bigger case head than the RUM, but if the boltface is opened up will the cartridge fit in a Rem700 long action?

Is 338 caliber allowed in 1000 yard benchrest? I went through some PS magazines & mostly see 30 cal & smaller cartridges being used. Are 30 cals intrinsically more accurate than 338 or is the 338 cal for long range target shooting a new development.

Thanks.

Chris.
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  #13  
Old 07-04-2003, 04:45 AM
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Join Date: Jun 2001
Location: Palmer, Alaska
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Re: Overbore???

Chris,

There's alot of theory behind longer necks and sharper shoulders cutting the errosion, formulas to figure them, so on and so on, who really knows why. Talking to Steve Shelp a while back on one thread or another here, I agree with him to the point it probably offers better physical protection more than anything. The burning powder is blasting out of the case and is funneling into the shoulder and out the neck, and the way I understand it, the burning powder that is blasting down the side of the case and on it's way out, it hits the shoulder, follows the shoulder angle, then is redirected to the opposite side as it enters the neck and leade area at near the same angle. If the case has a longer neck, it's said the burning powder that causes the errosion, will actually be bouncing off the inside of the cases "neck" and not off of the leade then throat area before it straightens out to head down the bore. If the neck is too short, and/or the shoulder angle to shallow, the powder directly impacts in front of the case mouth instead.... think cutting torch hitting steel and redirecting the flame. If the case neck takes the brunt of it before it's redirected instead of the throat, it can't hurt, and conversely, it could if it didn't. Time will tell. Others swear by it and have many reasons why their formula to figure the angle and neck length is better. Without high speed internal cameras in the chamber, this is one that will probably be theory for a long time to come. Can't argue with success though, just why and how it works is debatable. The theories make alot of sense, but how one's to prove his theory over anothers will be interesting to see.

I think my smith here in Anchorage said he had over 4000 rounds through his 30 Alaskan, which is a 40 degree shouldered 338 Lapua case necked down and blown out to near .570" at the shoulder with about a .400" neck length. Dave Kiff at Pacific Tool has the reamer plan for it too and I think it's real close to mine. Homer said he was still getting sub 1/3 MOA accuracy from it with something like only .020" - .030" errosion so far is all. To put that in perspective, my Dads short necked 6.5 WSM has about 500 rounds through it so far, he's got about .030" errosion "now". We'll see where accuracy gets it's best and then finally falls off down the road. I'm not too worried about it living a long, long time though... still, just an edjucated guess. [img]images/icons/wink.gif[/img]

The dies are custom, and running me about $215 from Jim Carstensen.

The way I see it:
$150-$300 - Good used 70 or 700 action. ($800+ for a custom)
$150-$500 - A solid stock and bedding job.
$450-$600 - Custom barrel and chambering.
$200-$275 - True action, Tubb recoil lug, (Sako extractor on 700), mag box.

$100-$350 - Custom dies
$40-$135 - Rent a reamer or buy a reamer of your own design.

You supply scope, rings and base.

It can get expensive, or stay relatively inexpensive, just depends on what you need and want. [img]images/icons/smile.gif[/img]

I think "Improved" in cartridge terms, is "modified" in real terms, most believe they're improved or they'd keep it the same. Weather it's actually "improved" is sometimes debatable. Eye of the beholder sometimes. [img]images/icons/wink.gif[/img]

Lapua had designed and rated the 338 Lapua at about 70,000 psi in the testing phase I "think", they later reduced it to about 63-65 kpsi, and all data suggests this is true. But, the case is super thick and strong and obviosly over built compared to others of equal case capacity. There could be many reasons they dropped the max pressure rating, accuracy problems at higher psi, case longevity or a few others. If I had to guess, I'd say it was accuracy, consistancy and also they'd be, pressure wise, "over the top" compared to any other factory chambering out there.... may have made too many potential customers in the "buying market" a bit too squeemish, if you know what I mean. The case is hell for stout and will live longer under heavier pressures than others, and it should too, it's casehead alone is a full .050" thicker than any other design I've ever seen, including that of the .408 CheyTac, which is more of an upscaled 416 Rigby case design than that of the intended 338 Lapua.

Good luck. [img]images/icons/smile.gif[/img]

[ 07-04-2003: Message edited by: Brent ]
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