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New Cooper 6.5x284

 
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  #8  
Old 12-24-2012, 10:59 AM
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Re: New Cooper 6.5x284

Quote:
Originally Posted by Mikecr View Post
He could get 2950fps at 18degs with 56.8gr 4831SC. This is ~2Kpsi above SAAMI max, and with a muzzle pressure of ~12.6Kpsi(very high). At 70deg the same load will likely put him at 3030fps, 8Kpsi over SAAMI max, same muzzle pressure.
53gr 4831sc will only get him 2830fps at 70deg.

He won't even get close to 4831 velocities using Retumbo.
The highest there is ~2800fps with a case full(including a full fireformed case).
His pressure would be 15Kpsi below SAAMI max, and likely producing very high ES.

The best he can do velocity-wise in 24", and possibly overall, is 60.5gr Ramshot Magnum at 70deg. This is barely SAAMI max, ~3016fps, not compressed, but muzzle pressure is still high at 13.4Kpsi.
With this load same conditions and a 28" barrel, he'd have 3130fps, same pressure but muzzle pressure would be down to where it is right now (~11Kpsi).
This is what a 6.5x284 cartridge is for.

No matter what, his muzzle pressures are high with a 24" barrel & this amplifies any flaw in release of boat tail bullets. It may not show up at 100yds, but it's a factor in distant shooting. The slightest crown flaw will show up big time, and ES is raised also.

It never made any sense to run big cartridges with short barrels..
With a 28" barrel, my 6.5WSSM can run circles around a 6.5x284 in 24". But a 6.5x284 in 30" would leave me in the dust(as you would expect from a way bigger case).

His gun, with that barrel length, would be perfect in 6.5x47L.
With all due respect Mike, I'm wondering if you have actually worked with a 6.5 x284 or whether you are looking a reference material. In either case the information you are stating is completely contrary to not ilymy own experiences are, but several other shooters of the cartridge as well. I have accurately tested at safe working pressures for years and verified all data with actual drops out to 1000 yards. I have also shot numerous game animals using the drop data out to 1000 yards.
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  #9  
Old 12-24-2012, 11:29 AM
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Re: New Cooper 6.5x284

Quote:
Originally Posted by Greyfox View Post
I have been a 6.5-284 shooter for several years, my current rifles, one a Cooper 520/26", the other a Savage LRH/24". It is very likely that you can boost your velocity using 140 VLD's to 2900-3000 FPS, getting the same accuracy you have shown or better using a 24" barrel, no high pressure, no blast effects. The chonographed velocity and drop data between my two rifles is 25 FPS, the 26" Cooper the higher. Both rifles shoot .25-.5MOA 5 shot groups. I have found that fire formed brass has more influence in improving ES than absolue accuracy with Lapua or Nosler brass. Seating depth of the VLD will have a greater influence. Both my rifles are .075" off the lands. Be are to work up carefully in .5 gr increments but you should get close to 53 gr. of H4831 SC, 2920-2950 FPS. I have found that Retumbo can produce better temperature stability, and higher velocities(2950-3000FPS) with equal accuracy. I use 59 gr in both my rifles but start at 57 gr and work up in .5 gr increments.
Congratulations, you have a very capable long range rig. Don't be too cautious about wringing out it's true potential. IMHO.
Hey Greyfox
Thanks for the info, I went up to 53gr of 4831sc but was only getting 2760fps out of my rifle. The groups really opened up. I was confused on why the speed wasn't going up in equal increments it .5grain increases. Because the groups where getting worse I stopped. It looks like I need to try some Retumbo, I use this powder for my 300rum. Thanks for your input and I will post results later this week. I am having trouble finding the 140gr Berger Hunting bullets any ideas. Merry Christmas!!!
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  #10  
Old 12-24-2012, 11:31 AM
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Re: New Cooper 6.5x284

I suggest there is a learning opportunity here.
If OP will be kind enough to post results of further work, we'll see who's right.
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  #11  
Old 12-24-2012, 04:01 PM
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Re: New Cooper 6.5x284

Quote:
Originally Posted by Mikecr View Post
I suggest there is a learning opportunity here.
If OP will be kind enough to post results of further work, we'll see who's right.
Sorry, the info I stated has been proven by numerous shooters. Simply run a search engine check on this site if you have any doubts. There can always be differences with specific rifles, but the info I posted will stand.
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  #12  
Old 12-24-2012, 04:22 PM
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Re: New Cooper 6.5x284

Quote:
Originally Posted by NVHunter1 View Post
Hey Greyfox
Thanks for the info, I went up to 53gr of 4831sc but was only getting 2760fps out of my rifle. The groups really opened up. I was confused on why the speed wasn't going up in equal increments it .5grain increases. Because the groups where getting worse I stopped. It looks like I need to try some Retumbo, I use this powder for my 300rum. Thanks for your input and I will post results later this week. I am having trouble finding the 140gr Berger Hunting bullets any ideas. Merry Christmas!!!
Try Sinclairs for the Bergers. I just bought some. I'm not sure what's going on with your velocity, might check the chronograph. Mine was off last week giving erroneous results. Seating depth will effect accuracy, pressure and velocity. I don't know if you worked on this but it can make a noticeable difference in your groups. Also, if you are too close or in the lands with max charges, you will get high pressure.
Thanks, you have a great Christmas as well! Good luck.
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  #13  
Old 12-24-2012, 07:04 PM
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Join Date: Mar 2011
Location: Nashville
Posts: 40
Re: New Cooper 6.5x284

Im loading 53 grns of 4831sc and getting an average of 2750 fps out of my Savage pred hunter and 1/4 inch 3 shot groups, I tried 54 grns but started seeing pressure, ( tight bolt). I wanted more speed so Im now loading 55 grns of H1000, and averaging 2830 fps, and still getting the same accuracy.
I would like to get to 2950, but just cant seem to get there, without pressure signs showing up. thats using 140 bergers. I think I will stay with the H1000 for now, I feel thats enough and the accuracy is great, this rifle got its first deer thanksgiving weekend. Great caliber.
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  #14  
Old 12-26-2012, 05:44 PM
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Join Date: Aug 2011
Posts: 22
Re: New Cooper 6.5x284

Update:
Loaded up some 142 SMK (Out of Berger 140 Hunting VLDs) with Retumbo.

Here are the results.
4000', 35 degrees, no wind, 55% Humidity. 100 yards.
142 SMK at 3.10", 215 primer, 3 shot group, Lapua brass

54.5 Gr Retumbo = 2873fps 3 shots touching, ****Best Group*****No pressure signs
55 Gr Retumbo Lost the data in crono????grrrr but group was .4 second best , no pressure signs
55.5 Gr Retumbo = 2905fps .6 group, no pressure signs
56 GR Retumbo - 2930 fps 1.5" group, Primer starting to creator, ejector mark on brass (too hot), no sticky bolt.

It looks like the Retumbo 54.5 gr (2873fps) load shoots as well 51.5 gr of 4831sc (2680fps, confirmed by drop test) load and give me almost 200fps more speed..... Ah the quest continues.

I am shooting better with this rifle no matter what load i put in it compared to my other rifles. But to be fair, this is the first upscale rifle I have ever owned and I am loving it.

Thanks for all the input I appreciate it , Remember to work your loads up slowly. My rifle took quite a bit less powder to start seeing signs of pressure compared to others that posted the same loads. Happy New Year!!!!!
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