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Belted case versus beltless case cartridges

 
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Old 05-02-2001, 10:37 PM
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Join Date: May 2001
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Belted case versus beltless case cartridges

Gentlemen,
Over the last several years I've noticed that articles have been published in virtually every major periodical dedicated to rifle involved sports addressing the debate over whether belted case cartridges are more or less inherently accurate than beltless case cartridges. Overwhelmingly, these arguments have been in favor of the beltless case cartridges, too. The rationale being that beltless cases provide for significantly better cartridge alignment inside the chamber than belted cases.
Recently, however, (and you guys keep the laughter down over seeing how wet behind the ears I am) I noticed something that strikes me as constituting a major flaw in this argument. A rifle cartridge doesn't even seat 100% of the way into the rifle's chamber! The head/rim sits flush against the bolt face, but from just ahead of the rim and or belt for at least 2 or 3 millimeters, there is no contact between the case body and the chamber wall! Of course, the basis of the argument for beltless case cartridges being more accurate would be obvious if this were otherwise and 100% of the cartridge's length came into contact with the c

[This message was edited by David P. Herne on April 25, 2001 at 04:32 PM.]

posted April 25, 2001 04:23 PM

Warren Jensen
Member

From: Arco, ID US
Registered: April 12, 2001
Posts: 12
Belted vs beltless
--------------------------------------------------------------------------------
David,
What is difficult to differentiate in performance is whether a performance improvement is the result of better design or better execution. I don't think there is conclusive proof that a beltless case is inherently more accurate than a belted case. After being fired-once and neck sized they will both be headspacing off of the shoulder. Granted there are more matches won and records set with beltless cases, and the most highly engineered, most efficient small arms round (excluding .224) developed is the T-65, 7.62 x 51, 308 Winchester, I think that most of the performance is gained through better components and closer attention to detail. If you slapped a belt on the 308 Win., would that make it less accurate? Probably not.

So, is the 7mm Dakota inherently more accurate than the 7mm Rem. Mag.? The components(cases) in general are inherently of a higher quality, but you can get cases of equal quality. A test of one rifle chambered in one and one in another would not be sufficient to categorically support that argument. You would have to test numerous rifles of equal quality.

So to answer your question, I don't know. I have seen a lot of opinions and data, but I do not think the argument has been proved.

By the way, you can get the performance you are looking for in a 280 Rem.

Warren@lostriverballistic.com http://www.lostriverballistic.com

posted April 26, 2001 08:41 AM

David P. Herne
Member

From: Houston, Texas (USA)
Registered: April 11, 2001
Posts: 12
Belted case vs. beltless case cartridges
--------------------------------------------------------------------------------
Warren,
Darn it! My post got cut off well shy of its conclusion! How'd that happen?
Anyway, the other thing I wanted to add as far as the relative virtues of the 7mm Dakota over other 7mm magnum cartridges (and this is something seen in alot of the newer beltless case magnum cartridges) is that the former is shorter but fatter than the latter. I began to speculate as to the difference thereby rendered pursuant to an exchange Dean and I had over the .338 Lapua. In one of Dean's replies to a inquiry I'd made about the then brand new Remington .338 Ultra, he commented that the cartridge falls way short of the potential of the .338 Lapua because of the case's length to diameter ratio. I failed to follow through with more questions because I get embarrassed to ask guys like you and Dean for advice about anything. But I came to the conclusion that, implicit in Dean's remarks, was the fact that a cartridge needs to start getting fatter (bigger in case body diameter) at some point, as just increasing case capacity by lengthening it will prevent it from using the propellant therein to its fullest potential (e.g the propellant would burn with the same uniformity as in a case with a lesser overall length to body diameter). Am I right?

Regards,
David

N/A

posted April 27, 2001 10:05 AM

Warren Jensen
Member

From: Arco, ID US
Registered: April 12, 2001
Posts: 12
Efficiency of case design
--------------------------------------------------------------------------------
David,
Maybe. As with most rules there are exceptions. If fatter relative to length were always true then the 22-250 would be inherently more accurate than the 223 Rem. or the 222 Rem., for that matter. It's not. The theory is that you will get a more uniform ignition and burn with the fatter case, thus belieing the old dictum that the primer ignites all the powder at the same time and uniformly. It doesn't. There is a minute time delay from back to front, giving the fatter/shorter case a theoretical advantage in combustion uniformity. It does not always work out this way in practice, but in the areas of accuracy competition there does seem to be a pattern.

To conclusively prove that one is more accurate you would have to conduct a test with powders of the same relative efficiency in the two cases and with the same density and space interstices, and then remove all of the other variables. It would be a daunting task. How do you eliminate small variables such as the stamping of the head of the case is more uniformly distributed around the base on the 223 Rem. than it is on the 22-250 and this may cause a more uniform hardening of the head allowing it to center up in the bolt face ever-so-more slightly concentrically.

You may be right, and I have heard it argued a lot, but it has not been proved scientifically. However, at some point statistics of many years of competition become a proof unto themselves.

Warren@lostriverballistic.com http://www.lostriverballistic.com

posted April 27, 2001 02:52 PM

Gary Rihn
Member

From: TN
Registered: April 14, 2001
Posts: 22
David-
"I failed to follow through with more questions because I get embarrassed to ask guys like you and Dean for advice about anything".

What??

Ask anything you like. I certainly don't know it all, but got to this point by asking a lot of questions. Heck, if we all knew everything already, there wouldn't be any point in having this forum.

Besides, you might ask something I've been wondering about, and save me the trouble of having to ask.

posted April 28, 2001 07:44 AM

David P. Herne
Member

From: Houston, Texas (USA)
Registered: April 11, 2001
Posts: 12
Efficiency of case design
--------------------------------------------------------------------------------
Gary,
Thanks for the vote of confidence, pal. But guys like ya'll (especially the W. Jensen's and D. Michaelis's of the world) have to watch out for people like me. I can become worse than a house guest that has worn out his welcome.
Warren,
I'm much obliged to ya for your feedback. And since you've brought it up, I might just have to take it upon myself to conduct the research of which you speak. I've got a friend whose planning on building the same rifle I talked about above (same Dakota T-76 action, same Krieger barrel, same McMillan A-2 stock), except chambered for the 7mm Remington Magnum. We could do some preliminary testing and submit it to you or some other ballistics authority for review, further testing, and then possibly, publication!!!

Just a thought . . . . . especially since there seems to be a dearth of research pursuant to this take on ballistics performance.

Regards,
Dave

N/A

posted April 28, 2001 03:15 PM
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