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Brass Life

 
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  #8  
Old 07-25-2006, 06:21 PM
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Re: Brass Life

If I were to bump I would use my full length die by starting out one full turn up off of the shell holder. I would blacken the neck and shoulder with soot from a match. Then adjust the die down until it was getting the whole neck and just started to touch the shoulder. Now I would be ready to bump. Take a brass that closes hard in my gun and run it through the die and then try it again in the rifle. I would take the die down just a smidge at a time until the shell would chamber easy. No more than that. Now the die is set to bump the shoulders on the batch of sticky brass. I still haven't had to do even this in near 20 years.
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  #9  
Old 07-31-2006, 01:10 AM
 
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Re: Brass Life

[ QUOTE ]
Brass life (reloads per case) depends on three things: how much the case is sized down form its fired dimensions, how hot the load is and the quality of the cartridge brass.

[/ QUOTE ]

Everyone seems to have missed a major determinate - cartridge. A 300 RUM at max SAMMI pressure doesn't have nearly the life of Bart's hottest 308 WCF loads. 300 RUMs typically get 3-4 reloading.

[ QUOTE ]

I and many others get between 50 and 100 reloads per good commercial rimless bottleneck cases when fired in SAAMI minimum chambers and full-length sized such that body diameter's not reduced more than .003-in. and the shoulder's set back no more than .003-in. using maximum loads producing best accuracy.


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Is this Partial Full Length Resizing (PFLR) that I have documented on my web site? I PFLR myself.

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Primer pockets don't open up much all with our maximum loads until after about 50 reloads.


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You omitted the 308 WCF qualifier. Unquestionably false for the 300 RUM, Kirby's uber mags and other hot rods.

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If they do, a tool is used to crimp the pocket's top edge so they'll hold a primer.


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This sounds interesting, do you have a link or other reference to such a tool? I'm guessing for many folks it's cheaper and better spent time to toss the brass and use fresh.

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We don't need to anneal case necks. I've never annealed a case neck.

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Because you have a custom tight chamber, custom dies and bump shoulder/diameter 3 thousands max. Not everyone can do that. I also question your generalization of the 308 WCF to the hotter rods typically used on this forum.

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If one gets short case life, too much of at least one of two things is the cause; case sizing (oversize chamber?) powder charge for the bullet used and case hardness (especially military cases; they aren't made to be reloaded, even match ones).

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Do you want the 300 RUM crowd to load at 308 velocities. Clearly false for non-308's.
Interesting conjecture on military brass. I've got lots of reloads of 308 military match on my 243 (after outside neck turning). Commercial brass isn't made to be reloaded. It's manufactured for new [factory loaded] cartridge. Do you have any evidence to support this position (I'm not saying your wrong, I'm just a bit skeptical). My .243 anecdote is not evidence you are wrong. It's more likely that military brass gets less reloads because it's thicker. There is no active step to make commercial brass inherently reload able (that I'm aware of).

I found your old posts at yarchive.net/gun/ some of the best reading on the net. (I have a link to it on my 50 BMG home page I even have a Bart Bobbitt folder with your posts (in a nicer, more readable format) with a link to where the information came from.
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  #10  
Old 07-31-2006, 07:48 PM
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Re: Brass Life

So you think a 300 RUM at max SAMMI pressure doesn't have nearly the life of my hottest 308 WCF (itís 308 Winchester, not 308 Winchester Center Fire) loads. Well, thereís not more than about 3000 ppsi difference between specs as far as I know. If you've got some real data, let me know what it is. The .308's peak about 58,000 and the 300 RUMís about 61,000. But I know the perpencity of magnum owners (Ďspecially on this forum) to throw more coal in their fire boxes to create more steam pressure in their boiler so itís no wonder to me they typically get 3-4 reloads per case. Such reloaders are sometimes referred to as METMís (pronounced 'met-ums). Any sport involving speed and power has lots of them. Iíve known a few users of .308's that used all sorts of tricks to get 300 fps more speed for a given bullet; a couple of them ruined their rifles (and sometimes their body parts) doing so. But that didnít happen until a few milliseconds after they pulled the trigger on a way-too-hot load.

No, I donít do any form of partial full-length resizing (PFLR). ĎTis interesting to me the process for this term has changed in the last few years. For decades, it meant to use a full-length sizing die on a bottleneck case such that the fired case neck was not sized all the way to the shoulder. This reduced fired case body diameters a few thousandths but set the shoulder forward a bit and sometimes made the case hard to chamber. It was used by folks who got too short a case life Ďcause they set the shoulder back too far using regular full length sizing which meant to reduce all case diameters from pressure ring to case mouth and set the shoulder back. Nowadays, PFLR means different things to different folks and the original use has gone with the wind for most folks. I still use the original description for PFLR.

Well, of course primer pockets open up faster with more peak pressure. I donít think itís prudent to load cases that hot. But others do and thatís fine with me. I donít like being by folks shooting such hot loads; Iíve been there and have almost memorized their screams when a case or barrel lets go; yes I was by a barrel when it blew apart looking like a half-peeled banana at the back end. The tool a friend uses to close primer pockets to again hold a primer is one he made. As I remember itís a round ball about 3/10ths inch in diameter laid in a shell holder pressing up on a case against a rod coming down from a die in his press. The ballís shape is such that it swages the top of the primer cup a bit smaller and that holds the primer in. I donít know of any commercial ones. I think itís best to keep peak pressures down to SAAMI-safe levels. One gets longer case (and primer pocket) life and best accuracy is much easier to attain. Besides, doing this gives one a reasonable safety margin in case something sneaks in to the system thatíll cause really high pressure. Without a safety margin, somethingís gonna break.

We don't need to anneal case necks. I've never annealed a case neck. And we donítí use custom tight chambers and dies which is a very, very common and incorrect assumption. SAAMI chambers for a .308 Win. have neck diameters of about .344- to .345-inch. Our loaded roundís neck diameters range from .331-inch with WCC58 super-thin walled .308 Win. match cases to .339-inch with some commercial cases. Lots of clearance, yes, but very, very accurate rifles and ammo thatíll equal what any tight body/neck benchrest chamber/case combination out there produces and sometimes beats them. I and others use standard full-length sizing dies (RCBS for me) with their necks lapped out to .002- to .003-inch smaller than loaded round neck diameter; Iíve got seven at different diameters for different makes of cases with different neck wall thicknesses. And we set the shoulder back a couple thousandths as well as reducing body diameters from pressure ring to shoulder a few thousandths. For what itís worth, everybody can do this; itís easy.

Do I want the 300 RUM crowd to load at 308 velocities? No way. They would not like using a reduced load. Although many users of any given cartridge canít stand whatever velocities it gives a spectrum of bullets; they want more. So they cram more powder/power in the case, push pressures to near unsafe limits, then smile Ďcause theyíve got a reasonably well performing volcano with a barrel on it.

Regarding my interesting conjecture on military brass versus commercial brass as far as reloading is concerned. A friend of mine used to be a field rep for Remington arms and we shot a lot together. He sometimes talked about Remingtonís folks operating the Lake City Army Ammunition Plant in Missouri and their case making operations compared to the commercial stuff Remington made. Military brass has to be harder and thicker to withstand the rigors of storage, shipping, handling, use (including very high pressures at times) and reliability. Commercial brass is more ductile and forms much easier which makes it easier to reload and metal fatigue from multiple sizing operations doesnít happen as often. Commercial brass is also more uniform than military brass and therefore is more accurate. I heard the same stuff from an engineer at Lake City's plant when I had to talk to them about some poor quality 7.62mm NATO M118 match ammo a military unit I was in was shipped (horrible accuracy!!!!) No self-respecting highpower competitor (benchrester, either) I know of ever uses military brass if he expects to shoot winning and/or record setting scores. Call the cartridge brass making companies and ask them what the difference is and why they take no active steps to make commercial brass inherently reloadable if thatís your belief.
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  #11  
Old 07-31-2006, 11:27 PM
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Re: Brass Life

Bart B,

I have no dog in this fight but your 61,000 psi number is interesting to me as you say this is the limit of the 300 RUM. I was always under the impression that it was rated at 64,000 psi like most other modern high intestity magnums.

A quick look though the Hodgdon loading data for the 300 RUM reveals many loads that go right up to this pressure level. Now I am sure Hodgdon is not loading to +SAAMI specs and I know for a fact they would not print actual pressure data that was over SAAMI spec so I suspect your numbers are not correct just judging from what is actually printed by Hodgdon.

Not sure what you mean by the definition of partial FL sizing has changed either, AS far as I know it means the same it has always ment. No experienced loader I know has any other definition then the one you discribe, fill us in on the current definition of PFLS that is different then what it has always been.

So what type of rifles are these that are letting loose all the time at your range? Who made them? What were they chambered in. I can tell you for a fact that one of my Rem 700 rifles that was totally accurized and blue printed could not be blown up using appropriate powders and with no bore obstructions. You may well lock a bolt up but you will never blow a rifle apart.

If this is happening and you witnessed it, It was not from the use of appropriate powder be used with just to much powder. IT was to fast a burn rate powder being used incorrectly. This is the fault of the reloader not the rifle and not the chambering being used.

No modern, properly build rifle coudl be blown up using apporpriate powders for the chambering.

For example, if you had a Rem 700 chambered for the 300 RUM and you were using a 180 gr Accubond and Retumbo powder. You simply could not get enough retumbo in the case to case catastrophic rifle failure. Unless there was a bore obstruction.

Do not take that as saying you could not blow a primer pocket or lock up a bolt but those are totally different then a rifle coming completely apart like you say you have witnessed. Very few shooters have witnessed this and the ones that have occur from either a gross misuse of powder or a bore obstruction.

Most rifles that come apart are generally rifles that are not intended to be used with modern high pressure loads but since the owners of the rifles are to cheap to spring for the proper receiver you see receives such as the small ring mausers being chambered for modern high pressure rounds. Again, not the fault of the cartridge, not the fault of the rifle, its the fault of the cheap owner and gunsmith that did the work if there was actually a smith involved and not a basement barrel job which is common as well.

Also, your telling me you have up to 14 thou neck expansion on each firing, you only neck size and you never anneal and you can get 50 to 100 firings per case. Ya know that this tells me, if your telling the trueth, your loading to about 45,000 psi in pressure because at 50,000 to 55,000 psi, cartridge brass permanently deforms. That means your case necks will expand to fill the neck of the chamber and stay there.

This also means that they need to be sized back down 14 thou so that they will hold a bullet securely enough to be useful. Just this expansion and resizing alone will work harden case necks. The thinner the necks the quicker this will happen and the sooner you will get neck splits without annealing.

Add to this the heat of actually firing a round and this will accelerate the process even more.

Sorry my friend, Unless your loading puff loads in your 308, I simply do not believe your 50 to 100 firings per case without annealing or FL sizing. At some point you will have to bump the shoulder or chambering will get extremely tight once the case begins to temper from heat and looses its elastic properties. This will occur within 10 firings no matter what load you use.

Again, I really do not care what position you take on this subject but you have made a few comments that simply do not hold water with real world experience on my end.

No flame intended here so please do not take offense but I thought something had to be said about some of your comments and I was actually suprised you have not been called on them already.

Kirby Allen(50)
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  #12  
Old 07-31-2006, 11:41 PM
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Re: Brass Life

Bart, a bigger round is going to work the brass more at the same pressure. It just will.

Take a look at bolt thrust which goes up with the square of the interior case diameter. Even with appropriately thickened brass to arrive at the same stress ratio for pressure in the brass itself you're left with a larger total force in the end. This force is going to deflect the same action at the boltface more than a smaller round at the same pressure. There's no way to avoid it. This encourages more brass growth.

Same deal in the radial direction. If you look at the equations used with strain gauges and understand what they're actually telling you, they're telling you an identical barrel in 300 RUM will be "stretched" at the shot more than a .308 even at identical chamber pressures.

To expect brass life in one to apply to the other at the same pressures (300 RUM is 65000 psi average BTW) is to have unreasonable expectations.
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  #13  
Old 08-01-2006, 01:07 AM
 
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Re: Brass Life

Thanks for correcting me on the 308 WFC.

[ QUOTE ]
So you think a 300 RUM at max SAMMI pressure doesn't have nearly the life of my hottest 308 load ...If you've got some real data, let me know what it is.

[/ QUOTE ]
This is well know to the 300 RUM community (most who also own at least one 308). It could be a well know myth, but the fact that many folks use max loads from published manuals for each cartridge - and get 3-4 reloads from the 300 RUM and over 20 with the 308 (doing some annealing) is evidence it's not a myth.

[ QUOTE ]
But I know the [sic]perpencity of magnum owners (Ďspecially on this forum) to throw more coal in their fire boxes to create more steam pressure in their boiler so itís no wonder to me they typically get 3-4 reloads per case. Such reloaders are sometimes referred to as METMís (pronounced 'met-ums). Any sport involving speed and power has lots of them. Iíve known a few users of .308's that used all sorts of tricks to get 300 fps more speed for a given bullet; .

[/ QUOTE ]

I'm under the impression most on this forum do load development to find the sweet spot (min Std-Dev on velocity). The 300 RUM is more popular than the 308 for long range shooting because it can safely propel a 240gr pill 1.5 miles. The 300 RUM has a Ginormous Advantage over the 308 in the long range arena. Folks who want even more speed go for a Kirby Uber mag, 338 edge or some other hot rod.

Google reports METMís as Mediterranean Editors and Translators but I'm guessing your meant it as an ad hominem attack. Can you provide a ref for METM's?
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Well, of course primer pockets open up faster with more peak pressure. I donít think itís prudent to load cases that hot.

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Much of that depends on the hardness of the brass. You can read about it at the excellent 6mmBR site [ QUOTE ]
Even if you can potentially get more loadings out of a Lapua case, Winchester brass offers more bang for the buck. You'll find a lot of once-fired Federal Gold Medal Match brass available. While it tends to shoot accurately, we've found GMM brass is relatively soft compared to Lapua or Winchester, so the primer pockets tend to loosen up after just three or four reloadings.

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HOLLY primer pocket batman, even the 308 using Federal GMM brass gets only 3 or 4 loads. Reading further they write
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In addition to commercial brass, many .308 shooters reload boxer-primed military cases such as Lake City, IMI, and Hirtenberger. The Lake City Match brass is pretty good. ...IMI brass has a reputation for being strong, but we advise you only to purchase it new. ... <font color="red"> The most important thing to remember about military brass is that the internal capacity will probably be less than commercial .308 Win brass, because military brass often has thicker webs or casewalls </font>

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When I asked you for a reference, I was asking for something verifiable, not 3rd party hearsay over a few beers with a salesman. I agree military brass is harder than most commercial brass, that's why I ANNEAL my military brass every other reload. Because military brass is thicker and harder, you can actually reload it more times than commercial brass. (The opposite of your unsupported conjecture). Part of the allure of the 308 WCF (Win Cartridges are FUN) - economy, doesn't require BR prep or BR components. I know muzzle breaks are anathema to the BR boys, but after Kirby re-crowns my cheap factory sticks and adds a muzzle break (and trigger job), they shoot sub 3/4 MOA (some even better). My borescope shows the tack driving 308 Kirby just sent me has a barrel that looks like the surface of the moon. I'm amazed it shoots so well. (At the recommendation of 7mmBR I'll be trying the Tubbs final finish ).

I agree with you military brass is not the correct choice for BR. But this forum is not about BS or BR. Take most BR guys hunting and the first time they eject a cartridge (because they don't know how to hunt, they didn't get off a shot), the bullet sticks in the barrel and powder pours into their magazine - they begin to realize there is a world of difference between BR and long range hunting. I took my 308 out last weekend and was busting rocks at 100 to 400 yards off a bipod in the dirt, weeds, off tree stumps. BR gear does me no good here.

&gt;&gt;The tool a friend uses to close primer pockets to again hold a primer is one he made.
OK, not something the rest of us can easily take advantage of.

[ QUOTE ]
I think itís best to keep peak pressures down to SAAMI-safe levels. One gets longer case (and primer pocket) life and best accuracy is much easier to attain Besides, doing this gives one a reasonable safety margin in case something sneaks in to the system thatíll cause really high pressure. Without a safety margin, somethingís gonna break...


[/ QUOTE ]

I don't think anyone here is recommending exceeding uncle Sammy's safety limits. If you want liberal democrat safety move over to the ping pong forum. All my firearms are inspected by competent smiths. I only use powders that fill the case to at least 90% so double loads are impossible.

[ QUOTE ]
I and others use standard full-length sizing dies (RCBS for me) with their necks lapped out to .002- to .003-inch smaller than loaded round neck diameter; Iíve got seven at different diameters for different makes of cases with different neck wall thicknesses. And we set the shoulder back a couple thousandths as well as reducing body diameters from pressure ring to shoulder a few thousandths. For what itís worth, everybody can do this; itís easy.


[/ QUOTE ]

This sounds interesting. Where can I get my dies worked like that? How much does it cost. How does the price compare to having custom dies made from a couple of fired cases?

[ QUOTE ]
So they cram more powder/power in the case, push pressures to near unsafe limits, then smile Ďcause theyíve got a reasonably well performing volcano with a barrel on it..


[/ QUOTE ]

How do you define near unsafe ?. I have no idea what that means. Have you shot with a representative population of this community to make that judgement? From what I've read, the folks on this forum are looking for high velocity cartridges, high BC pills and the most accurate/consistent load/combination they can get. I don't know anyone who's out to get the highest possible V at the expense of accuracy. Can you site posts supporting your claim?
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