Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Rifles, Bullets, Barrels and Ballistics


Reply

Throat erosion and double-based powders.

 
LinkBack Thread Tools Display Modes
  #8  
Old 03-26-2012, 11:52 AM
Platinum Member
 
Join Date: Feb 2010
Location: Gillette, WY
Posts: 2,404
Re: Throat erosion and double-based powders.

BART,

Maybe I misunderstood what you mean but, from the hodgdon site:

7mm RM:
120 GR. HDY SP Hodgdon H4831 .284" 3.230" 65.0 3095 45,800 CUP 68.5 3236

7mm RUM:

120 GR. NOS BT Hodgdon H4831 .284" 3.600" 85.0 3344 54,600 PSI 90.0 3536


Same Bullet weight, same powder. 22 grains & 300 fps difference, did I miss something?
Reply With Quote
  #9  
Old 03-26-2012, 03:09 PM
Platinum Member
 
Join Date: Dec 2008
Location: Great Falls, MT
Posts: 3,950
Re: Throat erosion and double-based powders.

For 7 RUM ...

(Taken from Lyman 49th ed)

130gr JSP
3.6 OAL
BC=.394
26" barrel
1:9.5 twist
Fed 215
110gr AA8700
3560 FPS
62,900 PSI

Using Handy Excel Formula Predicts Useful Barrel Life « Daily Bulletin ...

__________________

I voted for my "FREEDOM", "GUNS", and "MONEY" - keep the change - UNK.



"I am always proud of my country!"

"Leadership Rule #2: Don't be an @zzhole." - Maj Gen Burton Field.

Last edited by FEENIX; 03-26-2012 at 04:17 PM.
Reply With Quote
  #10  
Old 03-27-2012, 01:56 PM
Silver Member
 
Join Date: Feb 2012
Location: Remington County, PA
Posts: 383
Re: Throat erosion and double-based powders.

First of, the RUM can handle 25% (or 25 grains) more powder than the rem mag, thereby adding around 10% more velocity to any given bullet, resulting in 25% more "hitting power".

I suppose that most of those who do go ultra do so because they are looking for big bore size, and/or big bullet weight. But apparently I am one of those individuals who was blessed (or more likely, cursed) with the "need for speed" mentality (note my user name). I maxed out (actually, max + 1.5) on the mag at 75gr of RL-19, without my bolt going tight. Velocity at 15ft was 3680fps, + or - 5fps on 80% of the rounds fired. That probably equates to 3700 at the muzzle. Despite not having a tight bolt, I WAS very nervous firing those rounds.

The one over-charge that I did have (not sure how it happened), gave me a reading of 3875 at 15', with a very tight bolt! The amount of RL-19 that my figures indicate would have been needed to achieve that velocity, is 83gr! It must have been a really compressed load. THAT put put a scare into me, so it was at that point that I decided to chamber-up to something that can handle that much (and considerably more) of a charge, without the bolt going tight. From THAT perspective, doesn't 4000 seem reasonable for the RUM, especially since the required charge would probably still be a good 10-15gr below the max capacity (100gr) of the RUM.

And barrel burnout in only 100 rounds? Why do you think THAT low? The 220 runs similar/greater velocities. Albeit, it IS known to be a barrel burner, but with modern steel formulations, I'm thinking it should do 500-1000 rounds before accuracy goes out the window. I'm looking at the 7RUM that I'm building as the 220's "big brother".

EDIT: Just like the 220 can basically "vaporize" prairie dogs, I want to vaporize ground hogs!

Last edited by Max Heat; 03-27-2012 at 02:12 PM. Reason: added info
Reply With Quote
  #11  
Old 03-27-2012, 03:54 PM
Silver Member
 
Join Date: Feb 2012
Location: Remington County, PA
Posts: 383
Re: Throat erosion and double-based powders.

None of the posted load data applies to the powder that I've been using in the mag (Reloader 19).

Does anyone have any 7RUM data (max loads&velocities) for the 120NBT/RL19 combo?

Or is #19 simply too fast burning for the RUM, even though the light bullets will spend LESS time inside the barrel than in the rem mag?


Is there any 120NBT/RL22 data for 7RUM out there maybe??

What about 100 grainers at 4 grand (or even higher?), if the 120's generate too much pressure for the 7RUM, at the target velocity, with ANY powder?

You just gotta love how accurate those 7mm 120gr Nosler ballistic tips are though.
Reply With Quote
  #12  
Old 03-27-2012, 06:42 PM
Platinum Member
 
Join Date: Jan 2003
Location: The rifle range, or archery range or behind the computer in Alaska
Posts: 3,419
Re: Throat erosion and double-based powders.

Quote:
Originally Posted by Max Heat View Post
And barrel burnout in only 100 rounds? Why do you think THAT low? The 220 runs similar/greater velocities. Albeit, it IS known to be a barrel burner, but with modern steel formulations, I'm thinking it should do 500-1000 rounds before accuracy goes out the window. I'm looking at the 7RUM that I'm building as the 220's "big brother".

Having destroyed a throat and creating heat checking out the ***** in a 300 RUM in less than 70 rounds by running 180 grain pills at 3400 FPS is why I think the barrel life for the 7mmRUM will be so low running such 'hot rod' loads. I could be way off but having conversed with other 7mmRUM users and hearing their stories of rediculously short bore life while running top loads leads me to this opinion.

Hope that helps.
__________________
Quote:
Originally Posted by Broz View Post
Please just answer one very simple question. Why would anyone shooting long range load a low BC , low SD 168 gr offering in a 300 win???????

My answer to this is. The only reason is to make the 7 RM look good. There is no other reason.

Jeff.
Reply With Quote
  #13  
Old 03-27-2012, 09:09 PM
Platinum Member
 
Join Date: Dec 2005
Posts: 2,114
Re: Throat erosion and double-based powders.

Quote:
Originally Posted by Outlaw6.0 View Post
BART, Maybe I misunderstood what you mean but, from the hodgdon site:

7mm RM: 120 GR. HDY SP Hodgdon H4831 .284" 3.230" 65.0 3095 45,800 CUP 68.5 3236

7mm RUM: 120 GR. NOS BT Hodgdon H4831 .284" 3.600" 85.0 3344 54,600 PSI 90.0 3536

Same Bullet weight, same powder. 22 grains & 300 fps difference, did I miss something?
I was not wrong. Nor did I make an error. No mistake was made, either. Didn't even goof; not one tiny smidgen. But I sure was weak in being right................................ Shame, shame on me for mixing up the data on Hodgdon's web site. I'm probably the only person on this planet who's done that.

Kudos to your for noticing. Excuse me while I find a rock to slither under..........
Reply With Quote
  #14  
Old 03-28-2012, 06:36 AM
Platinum Member
 
Join Date: Dec 2005
Posts: 2,114
Re: Throat erosion and double-based powders.

My calculations for barrel life with a 7mm barrel burning 85 grains of powder is rather short. With bore capacity at 38.5 grains, 85 grains is about 220% overbore. Barrel life will be about 600 to 700 rounds.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Throat erosion and double-based powders.
Thread Thread Starter Forum Replies Last Post
HMR 17 throat erosion? BlackSS Rimfire and Airguns 1 07-08-2011 09:58 PM
.338 Edge throat erosion Topshot Rifles, Bullets, Barrels and Ballistics 5 09-16-2010 07:11 PM
6.5X284 Throat Erosion Willys46 Rifles, Bullets, Barrels and Ballistics 1 03-22-2010 01:32 PM
Shocked at how much throat erosion Alan Griffith Rifles, Bullets, Barrels and Ballistics 18 01-16-2008 02:14 AM
throat erosion? Dr. John Long Range Hunting & Shooting 12 02-01-2004 09:29 AM

Current Poll
Do You Think Slingshots Should Be Legalized For Hunting Brown Bear?
Yes - 47.55%
846 Votes
No - 52.45%
933 Votes
Total Votes: 1,779
You may not vote on this poll.

All times are GMT -5. The time now is 02:31 AM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC