Long Range Hunting Online Magazine


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

Rifles, Bullets, Barrels & Ballistics Applied Ballistics


Reply

Balance in bore diameter???

 
LinkBack Thread Tools Display Modes
  #8  
Old 03-29-2006, 12:17 AM
Platinum Member
 
Join Date: Sep 2004
Location: on the rifle range in Utah
Posts: 2,720
Re: Balance in bore diameter???

I agree with Kirby's post.

I would also like to add that there are overbore 338's just the same as there are overbore 17's through the mighty 50. What you have to do is look at the bc's of the available bullets in your caliber, pick a target velocity window, see which case can give you that velocity with the smallest amount of powder, and then have fun with it. Every caliber now has bullets from the .2 bc's up to and past the .5's. The 338 caliber just has the sheer weight and momentum to maintain massive amounts of energy at long range and therefore makes it easier to kill and spot shots in the dirt.
__________________
Find it
Range it
Click it
Pull it
Dump it

If it's not far, it's boring.
Reply With Quote
  #9  
Old 03-30-2006, 08:52 AM
Platinum Member
 
Join Date: Dec 2005
Posts: 2,114
Re: Balance in bore diameter???

Fiftydriver's comments are pretty good and explain things well. Here's some observations I've made over the years.

For each caliber, there seems to be a few cartridges that seem to attain the best accuracy. These cartridges are the ones often used in competition and tend to produce the best scores. They all have one thing in common; their powder charge weight is at or very near 'bore capacity.'

OK, so what is bore capacity? Years ago a 'smith catering to the benchrest crowd explained it to me as follows. Bore capacity in grains of powder is equal to the cross sectional area of the bore in square millimeters; 1 grain of powder for each square millimeter. I did some checking and here's what I learned comparing the bore capacity for different calibers and examples of very accurate cartridges for them:

22 caliber, bore capacity = 26 grains; .22 PPC, .222 Rem.
24 caliber, bore capacity = 28 grains, 6mmPPC, 6mmBR
26 caliber, bore capacity = 33 grains, .260 Rem.
27 caliber, bore capacity = 38 grains, 7mm-08
30 caliber, bore capacity = 45 grains, .308 Win.

That 'smith also said that when cartridges at bore capacity are used, barrels typically last about 3000 to 4000 rounds of best accuracy. Double the powder charge over bore capacity for a given bore and barrel life drops to 1/4th as many; 750 to 1000 rounds.

Interesting stuff but it seems to be correct. There's a bunch of meanings/definitions for bore capacity, but this one makes the most sense to me.
Reply With Quote
  #10  
Old 03-30-2006, 09:17 AM
Official LRH Sponsor
 
Join Date: Jun 2004
Location: Fort Shaw, Montana
Posts: 6,831
Re: Balance in bore diameter???

Bart B,

What barrel length are you using for those Bore capacity figures?

So are you saying my 257 AM(95 gr powder charge) and my 7mm AM(107 gr powder charge) are a bit overbore?? [img]/ubbthreads/images/graemlins/blush.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

For pure accuracy and longest barrel life combinations I would tend to agree with your numbers for the most part.

Kirby Allen(50)
__________________
Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
Reply With Quote
  #11  
Old 03-30-2006, 11:35 AM
Platinum Member
 
Join Date: Dec 2005
Posts: 2,114
Re: Balance in bore diameter???

[ QUOTE ]
What barrel length are you using for those Bore capacity figures?

So are you saying my 257 AM(95 gr powder charge) and my 7mm AM(107 gr powder charge) are a bit overbore?? [img]/ubbthreads/images/graemlins/blush.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

For pure accuracy and longest barrel life combinations I would tend to agree with your numbers for the most part.

[/ QUOTE ]Barrel length didn't matter for this 'bore capacity' stuff. As barrels typically wear out from the throat forward from highest pressure and powder burning temperatures, that's where it came from and was/is based on barrel life. What 'efficiency' rating one gives a barrel for a given powder's charge weight vs bore diameter AND bore length may well be something else. But there are typically a narrow range of powder makes/types that tend to give best accuracy for a given bullet weight. And there's another range of powder makes/types that produce the highest muzzle velocity. Sometimes these two are the same.

No, I'm not saying your two cartridges are a bit over bore. If I did say they were, I would use a word meaning a lot more than 'bit.' That aside, sometimes one chooses to go a humungus amount of over bore capacity to get the muzzle velocity desired for a given caliber's bullet weight. It's sometimes been said that a given caliber is accurate for a given amount of powder. Shooting more powder per shot means you'll run out of powder (wear out your barrel) faster.

Regarding barrel life, it's much like religion, life partners, politics and sex. Whatever makes you feel the best is what you're gonna go with. We all have different personal standards and opinions.
Reply With Quote
  #12  
Old 03-30-2006, 02:20 PM
Official LRH Sponsor
 
Join Date: Jun 2004
Location: Fort Shaw, Montana
Posts: 6,831
Re: Balance in bore diameter???

Ah, I see.

As you say its a compromise but not to the degree most think. I have punched several groups out of my AMs that will measure less then 3/4 moa out to 1000 yards. Many in the .1"s and .2"s as well at 100 yards, not uncommon.

I suspect proper receiver machining and barrel fitting have much more to do with accuracy potential then anything else.

That said, a small caliber, small capacity is very easy to get to shoot tiny groups, very easy. Conversely, its much more of a challange to get a big chambering to shoot well but it is surely possible, repeatable and practical to do so with the proper rifle building techniques.

In my opinion, a true test of a custom rifle builder is not how accurate they can build say 223 Rem or 6mm BR. What would interest me more is if they could build a highly accurate big gun, say 7mm RUM and larger. This is where close enough just don;t cut it and it shows on paper.

Many feel this is a result of to much capacity, in my opinion thats hogwash, and more then likely its loose machining that is the reasoning or unsquared receivers and barrel work.

When all is said and done, theres only one way to get a .800 BC or higher bullet to over 3300 fps, its with a big engine. Sure barrel life will be shorter then a 22 ppc but you don't drive a 1200 HP dragster as your everyday car either, only for special, specific purposes. Likewise, you don't ask a 22 PPC to reach out 800 to 1200 yards and hammer a deer size target either, for that matter even punching paper.

I think alot of smiths make a much bigger deal out of barrel life then needs to be said. Most shooters, even serious shooters never shoot their rifles enough to burn out a barrel. And those that do, will not waste a high performance rifles barrel life just plinking, more suitable rifles are used for general purpose in most cases.

For big game rifles, a 900 to 1000 round accuracy barrel life will last even serious big game hunters nearly a lifetime of use. The better the shots, the longer the barrels will last in my experience [img]/ubbthreads/images/graemlins/grin.gif[/img]!!!

Kirby Allen(50)
__________________
Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
Reply With Quote
  #13  
Old 03-30-2006, 02:59 PM
SPONSOR
 
Join Date: Nov 2004
Location: El Reno, OK
Posts: 1,502
Re: Balance in bore diameter???

And then you have idiots like me and Bill Bailey who buy these massive big game rounds and just have to damn much fun with them!!!

Seriously, barrels are a replaceable item, most shooters will never fire these big calibers enough to burn out a barrel, and ya cant take your money with ya to heaven so you might as well enjoy it while your here. [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/wink.gif[/img]

"The better the shots, the longer the barrels will last in my experience !!! " Well I never thought being a bad shot could be so much fun [img]/ubbthreads/images/graemlins/grin.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img] I am sure we will take it easier with this Big 7mm you are building us but for know I am just having to much fun with the 270AM

These guys at this shoot in Texas will probably crap themselves when they see me and Bill set up to shoot next to them. We will be surronded by guys shooting 6br's and 6xc'x and then BAMMMM!!! the big daddy 270AM roars, ha ha ha, win or lose it outta be a lot of fun

take it easy
steve
__________________
Steve Elmenhorst
Third Generation Shooting Supply
www.3rdgss.com
"Products for shooters, by shooters"
1-800-522-3314
monday-friday 8:30-5:30 CST
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Balance in bore diameter???
Thread Thread Starter Forum Replies Last Post
What is the best (most consistent) balance midgetorama32 Reloading 2 08-07-2011 01:58 PM
Rifle Balance? edge Rifles, Bullets, Barrels & Ballistics 11 05-19-2011 07:31 AM
Micro Diameter vs Standard Diameter Browninglover1 Bowhunting 0 04-30-2011 12:41 PM
Lee Balance Beam Scale geneinnc Reloading Equipment and Components 3 03-11-2008 02:53 PM
Rifle Balance ? edge General Discussion 3 12-13-2006 09:53 AM


All times are GMT -5. The time now is 12:55 PM.


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