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7mm Remington Ultra Mag

 
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  #15  
Old 10-10-2011, 07:37 AM
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Re: 7mm Remington Ultra Mag

Quote:
Originally Posted by Fiftydriver View Post
Sendero_Man,

Your load used 71.0 gr of Retumbo in a 7mm RUM?????

I would thing that load would be SEVERELY under loaded for this case capacity. Maybe I read it wrong and you were talking about a 7mm Remington Magnum and not the ultra Mag. YOu should be up in the mid to upper 90s with retumbo and this bullet weight. There must be some confusion here.
it is 168 VLD in a 7 RM

Rem. Mag.

I was just stating what I did in a similar factory rifle to get great results.
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  #16  
Old 10-10-2011, 08:41 AM
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Re: 7mm Remington Ultra Mag

Lhampton83,

As mentioned, if you have access to a local smith that can scope the throat for you that would be best. that said, I have seen many throats that if you "LOOKED" at them, you would say they were all used up but when you shoot them, they really suprise you as to how well they still shoot.

Its good to get a barrel scoped but simply shooting the rifle will also tell you what you need to know if you do not have access to smith with a bore scope.
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  #17  
Old 10-10-2011, 08:49 AM
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Re: 7mm Remington Ultra Mag

Meatyrem,

Barrel quality can have some effect on accuracy life but most of todays factory stainless steel barrels are pretty damn good as far as barrel life goes.

A loose throat will effect accuracy life more then anything simply because they allow more gas blowby around the bullet before it seals the bore. This causes an flame cutting effect on the throat. THis is generally why a match grade barrel will have a longer barrel life, because they are usually chambered with a much tighter, match grade throat which dramatically reduces this gas blowby.

For example, some factory throats will have a throat 1 to 1.5 thou over sized compared to bullet diameter. This may not seem like much but when talking throat clearances, ITS ALOT. Most of my throats on my custom designed reamers will have a neck diameter of 0.0002 to 0.0005" over bullet diameter so they are DRAMATICALLY tighter then any factory throat.

There are some match barrels that will tend to offer longer accurcy life with these high intenstity magnums but how you care for the barrel by keeping it from getting to hot while shooting and keeping it clean will effect barrel life much longer then anything else.

To that end, if you heat up a 7mm RUM or even a 7mm WSM for that matter and keep shooting it, they will have a shorter barrel life then even a very extreme 7mm AM that is used properly.
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Kirby Allen(50)

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  #18  
Old 10-10-2011, 08:53 AM
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Re: 7mm Remington Ultra Mag

Liltank,

Yes I have tested H-50BMG in the 7mm RUM and my 7mm AM. I personally do not like it in either. It is a decent burn rate but the powder is very large in size and as such, its hard to get up to a working pressure I prefer. It also increases the possibility for powder bridging.

I have used US869 which is slightly slower burning yet and it works pretty well but as its a ball powder, it burns with more carbon fouling and is less stable over temp changes.

With the very large 200 gr class custom bullets, this burn rate is about ideal in the 7mm AM but its a bit slow for the 7mm RUM because the cases will not support the chamber pressures needed to get a relatively clean burn on either of these powders. This is why I prefer the ball powders in this burn rate over H-50BMG as you can get much more powder in the case and get up to proper working pressures but again, you have to know these powders limitations with temp changes and keeping on top of the carbon fouling issues.

Retumbo, with its smaller size has proven to be a very good all around performer and about the best there is in the 7mm RUM.
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Kirby Allen(50)

Allen Precision Shooting
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Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

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  #19  
Old 10-10-2011, 08:54 AM
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Re: 7mm Remington Ultra Mag

Sendero_man,

Thanks for clearing that up for me. Just did not want someone to try 71.0 gr in their RUM!!!

That 7mm Rem Mag of yours is a hell of a shooter!!!
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Kirby Allen(50)

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  #20  
Old 10-10-2011, 10:33 AM
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Re: 7mm Remington Ultra Mag

Good luck reloading for your 7mm RUM. I'm not having much luck with a new Sendero I bought a couple of weeks ago. I think my main problem is the freebore in the Remington factory barrel. Remington specs on the chamber for the 7mm Rem. Ultra Mags calls for .400" of freebore to protect the gun from over pressure. This prevents even a remote possibility of seeting any bullet to the lands. I'm trying to load the Berger 180gr. VLD and with the bullet seated as far out as possible it's still .25" from the rifling. I've loaded Retumbo (92 grains) , H1000 (88 grains), H870 (94 grains) and H4831SC (81 grains) trying to find a load that will shoot. I've seated them with a COAL from 3.600" to 3.920 (that one got me a collapsed case and you have to remove the bolt to remove a loaded shell from the No joy yet. About the best I've been able to consistently get out of this bullet and caliber is about 1 1/2" groups at 100 yards. This weekend I loaded some test loads of the Berger 168gr VLD and the first groups I shot with the four different powders didn't show much either. Three shot groups were running about an inch. I'll keep trying the 168s for a while because I really like the high BCs of the Bergers. I also have some of the Sierra 175gr SMKs and SGKs that should be here today. I'm just afraid that about the time I find a load that will shoot my barrel will be burned out and my shoulder will be hamburger. If you find a load that will shoot, please share it.
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  #21  
Old 10-10-2011, 11:44 AM
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Re: 7mm Remington Ultra Mag

I just came by a 7mm RUM yesterday. I think I will try the 160gr Acuu bond first. The guy I gaot it from was shooting 140gr bullets and was fairly happy with the groups he was getting but he thought that a heavier bullet would perform better. I have my deer hunt comping up in a couple of weeks but after that I will get working on it. I'll keep you posted as to what I come up with.
Thanks to Kiby for all the helpful tips
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