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7mm vs. 7mm ultra mag?

 
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  #8  
Old 02-20-2009, 10:55 AM
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Re: 7mm vs. 7mm ultra mag?

J E, you are more knowledgeble on the subject than I am, and for the most part I completely agree with you. But I have read numereous posts that the 300 WSM shows quite long barrel life, 4000+ rounds, and that the 7mm WSM which is very close to the same case has short barrel life 1000-2000 rounds. I find that very interesting. I wonder if that translates over to the RUM cartridges in 7mm and 300? From what I've read it doesn't seem to, at least not to a significant affect. My guess is that a 300 Rum shooting a 210 bullet will probaly slightly out last a 7mm RUM shooting a 180 bullet under similar conditions? Just a guess. It's been my impression that smaller bores in equal size cases burn out faster because they are concentrating that fire power in a smaler area. That may be an overly simplistic view of it. There is probably mor to it. And your assertion that shooting heavier bullets at lower velocities and better powder burn makes sense,

Interestingly, GS claims their bullet design increases velocity withou increasing pressure and their design also facilitates the burn of powder over a longer and larger area of the bore resulting in less throat burning and overall cooler shooting temps.

GS CUSTOM BULLETS - Barrel Wear
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  #9  
Old 02-20-2009, 12:43 PM
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Re: 7mm vs. 7mm ultra mag?

Well being as you already have both a 7 Rem Mag and a 7 RUM and a few extra pennies laying around the situation seems to me to be like this.

Buy a reloading set and learn to reload.

Take a few more pennies and buy expensive optics such as rifle scopes, rangefinders, binoculars and spotting scope. Each one of those items will run very near $1K, so that is going to be quite a pile of pennies.

Use the 7 Rem mag for a practice rifle until you burn the barrel out and then use the action for a custom rifle.

Once you have developed some skill reloading then develop a good long range load for the 7 RUM and then set it aside for hunting only, do not use it for practice.

If either of the rifles proves to be inaccurate then you are in a different ball game.
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  #10  
Old 02-20-2009, 03:43 PM
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Re: 7mm vs. 7mm ultra mag?

Quote:
Originally Posted by MontanaRifleman View Post
J E, you are more knowledgeble on the subject than I am, and for the most part I completely agree with you. But I have read numereous posts that the 300 WSM shows quite long barrel life, 4000+ rounds, and that the 7mm WSM which is very close to the same case has short barrel life 1000-2000 rounds. I find that very interesting. I wonder if that translates over to the RUM cartridges in 7mm and 300? From what I've read it doesn't seem to, at least not to a significant affect. My guess is that a 300 Rum shooting a 210 bullet will probaly slightly out last a 7mm RUM shooting a 180 bullet under similar conditions? Just a guess. It's been my impression that smaller bores in equal size cases burn out faster because they are concentrating that fire power in a smaler area. That may be an overly simplistic view of it. There is probably mor to it. And your assertion that shooting heavier bullets at lower velocities and better powder burn makes sense,

Interestingly, GS claims their bullet design increases velocity withou increasing pressure and their design also facilitates the burn of powder over a longer and larger area of the bore resulting in less throat burning and overall cooler shooting temps.

GS CUSTOM BULLETS - Barrel Wear
Thanks for the complements but there is a lot more that I can learn before I go to the Happy
hunting ground. and I can only speak from over 50 years of experance and you are right
about smaller bullets and bigger cases.

Hear is an example= Take a 375 H&H with a 275gr bullet(The standard bullet used) and place
70grs of powder behind it and you will get 2600 ft/sec velocity and who knows how many
rounds you can run through it 15000+.

Now take the same 375 H&H case and neck it down to 7 mm and blow the shoulder out and
forward into a wildcat like the 7mm STW ( most belted wildcats started life as a 375 and were
changed to personalize them ) and you have a barrel burner because you have made it into
an over boar cartrige and barrel life will not be as long.

Barrel life is determined by many factors so to say a barrel only has 1000 rounds in it
would be unfair and just a guess under the worst case scenario.

I would think that the 7 WSM would have less barrel life than a 300 WSM but not twice or three
times less because of the smaller and faster bullets.

If a barrel is kept clean and carbon is removed as often as possible barrel life will be improved
and accuracy maintained longer.

The 308 is a prime example of the reverse because most match shooters use the 168gr + bullets
and velocity is 26 to 2800 ft/sec using around 42grs of powder and barrels last 20,000 +rounds
before any loss of accuracy.

The first thing I do when a friend brings me his favorite rifle complaining about how the barrel
is shot out and will not group any more is give it a GOOD back to bare metal CLEANING and
most of the time they shoot just like they used to.

And be carefull not to believe everthing you read about claimes of unbelievable high BCs,
velocites,Barrel life ETC because if it seems to good to be true it probably is not true.

By the way ANY Banded Bullet of the same weight and dia. will be slightly faster than a full
bore dia. bullet because of less bearing surface just like flat based bullets have longer
bodys than boat tailed bullets of the same weight and dia. increasing bearing surface
and slowing velocity slightly (a vary small % ) so this is not something new and wonderful
and may have a downside in some applications.

J E CUSTOM
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Last edited by J E Custom; 02-21-2009 at 10:29 AM.
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  #11  
Old 02-20-2009, 04:01 PM
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Re: 7mm vs. 7mm ultra mag?

Re barrel burners .- <I think one can get a very general but fair idea for comparisons if dividing powder grains/caliber.

i.e. 90 grains/ 7 mm cartridge: 12,86
65 grains/ 7mm cartridge: 9,28

It does not give absolute figures but I thin k can be an easy rule of thumb for a fast comparison. Of course it does not bear in mind bearing surface, speed, etc.. but does the job.

Re. the 7rm- it is well behind the 7rum but even being an oldie I would not treat it as useless. There´s many swearing for the 7wsm now and the 7rm is equally if nor more capable.
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  #12  
Old 02-20-2009, 04:43 PM
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Posts: 458
Re: 7mm vs. 7mm ultra mag?

I chose the 7 STW because it is (1) 7mm for the high bc and sectional density of the heavier .284 bullets (like 180gr Bergers). (2) Reputation for excellent accuracy. (3) A step up in power from the venerable 7 Rem. Mag., or the new 7 WSM.

Yes, it's overbore (inefficient), but not as bad as the RUM; and is reported to be less finicky to load for.

If I hankered for an even more powerful 7mm, I'd skip the RUM and go straight to the 7 Allen Magnum, which enjoys an outstanding reputation, and is formed from the very strong 338 Lapua brass (much stronger than Remington brass).
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  #13  
Old 02-20-2009, 09:11 PM
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Posts: 3
Re: 7mm vs. 7mm ultra mag?

Thanks to all who replied to my post. I recieved very knowledgalbe information from everyone that posted. I'll do my very best to apply this knowledge out in the field. Thanks to all and happy hunting.
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  #14  
Old 02-20-2009, 11:38 PM
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Re: 7mm vs. 7mm ultra mag?

Quote:
And be carefull not to believe everthing you read about claimes of unbelievable high BCs, velocites,Barrel life ETC because if it seems to good to be true it probably is not true.
JE, I hear ya on this, but there are guys shooting these bullets with significantly higher than *normal* velocities. The BC's are in question, but as I said in another thread, the proof will or wont be in the pudding. so I figure I'll load up a few and send them down range

Quote:
By the way ANY Banded Bullet of the same weight and dia. will be slightly faster than a full bore dia. bullet because of less bearing surface just like flat based bullets have longer bodys than boat tailed bullets of the same weight and dia. increasing bearing surface and slowing velocity slightly (a vary small % ) so this is not something new and wonderful and may have a downside in some applications.
Once again, I agree with you in theory, but working up loads for the smooth E-Tip and banded TTSX I found no significant difference in velocity. Now that may and probably is just my rifle or some other variable. but the GS's do seem to have something going for them in the velocity department. I would say the jury is still out until I see it for myself, but I like being an optimist when it comes to ballistics
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