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Brass troubles

 
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  #22  
Old 11-28-2008, 05:12 PM
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Re: Brass troubles

Mag, i didn't say a long throat will cause denting. i said if the bullet releases from the case before it engages the rifling can cause denting. did you read the other post i referenced where this was talked about? too low of pressure can also cause this. the reason he has this happen with one bullet and not the other is the length of the baring surface.
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  #23  
Old 11-28-2008, 06:59 PM
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Re: Brass troubles

Quote:
Originally Posted by woods View Post
Okay, here's a small sample of what's what in the real world. Going to my spreadsheet and taking one rifle, a Beretta Mato 300 win mag, and pulling out load and range data for loads that were only loaded-at-the-same-time and shot-at-the-same-time

5/30/05
Accubond 200 / 71.5 gr IMR4831 / 2956 fps
TSX 200 / 71.5 gr IMR 4831 / 2896 fps

2/12/06
Accubond 200 / 79 gr H1000/ 2983 fps
TSX 200 / 79 gr H1000 / 2967 fps

10/1/06
Accubond 200 / 72 gr RL22 / 2926 fps
TSX 200 / 72 gr RL22 / 2884 fps

That is shooting 4 shot groups. I could pull many more of these comparisons out of my spreadsheet. They generally happen during the load development stage on a new rifle.

It has always been my experience and others from what I have read that it takes more powder behind a TSX to achieve the same velocities. To me that means the TSX's develop less pressure for the same amount of powder.
My question is: How do you know that the barnes is producing less pressure at the same powder charge?
My experience has shown that to achieve the same velocity as conventional bullets with the Barnes you need to overload by 5%-10%, above SAAMI max pressure, using my pressure sensor I have found that Nosler Accubonds and Ballistic Tips give higher velocities at lower pressure than nearly all other bullets, including the Barnes.

Your examples don't prove whether the Barnes is showing less pressure or more pressure compared to the Accubond, only velocity differences, it is quite common for any type of bullet to show velocity differences compared to another with the same powder charge, that is why we 'work' up our loads, but pressure differences are an entirely different matter, we cannot compare pressure with velocity, some bullets are faster or slower at the same pressure, which should not be confused with the same powder charge.

Powder burning rates can change depending on the bullet used, even in the same case, which in turn raises/lowers pressure and therefore changes the burning rate even more, which is the cause of the original thread. The powder used with one bullet showed 'normal' operation, and when used with another showed too little pressure for normal operation.

You can never take anything for granted when it comes to handloading, the variables are exponentionally mind numbing.
Cheers.
MagnumManiac.
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  #24  
Old 11-28-2008, 07:15 PM
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Re: Brass troubles

Quote:
Originally Posted by davewilson View Post
Mag, i didn't say a long throat will cause denting. i said if the bullet releases from the case before it engages the rifling can cause denting. did you read the other post i referenced where this was talked about? too low of pressure can also cause this. the reason he has this happen with one bullet and not the other is the length of the baring surface.
dave,
I have several Weatherby cartridges, including a 375WbyMag, this particular chambering will not allow any bullet, except a Barnes, to touch the rifling when a bullet is placed in the chamber and an empty case is chambered behind it (Woodleigh 300gr PP.). Therefore every time this rifle is fired the bullet is released from the neck before the rifling is engaged, and I have never had a dented case, even with bullets that would have to travel for a good 1/4" from the case mouth before engraving the rifling don't show any denting of the case.
Also, I have never had a dented case while fire forming from 375H+H to 375Wby, even with the large gap that is present for gas to rush down into, it has never happened. If the pressure is substantial enough, the neck should be fully expanded to seal the chamber just as or before the bullet is fully released, if it didn't we would all end up with gas in our face on every shot we take.
I do not believe this to be correct that it causes case dents when a bullet is released from the case before it engraves the rifling, only unusually low pressures can cause this.
Cheers.
MagnumManiac.
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  #25  
Old 11-28-2008, 09:56 PM
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Re: Brass troubles

once the bullet releases from the case, and not engaged in the rifling, the pressure is the same everywhere in the chamber. to think the pressure is still just inside the case is wrong. the other post had a scenario where there was plenty of pressure and the dents still happened. how do you explain that. i used to think the way you do, that dents could only come from low pressures. but i learned something with that other post.
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  #26  
Old 11-30-2008, 04:46 AM
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Re: Brass troubles

Quote:
Originally Posted by davewilson View Post
once the bullet releases from the case, and not engaged in the rifling, the pressure is the same everywhere in the chamber. to think the pressure is still just inside the case is wrong. the other post had a scenario where there was plenty of pressure and the dents still happened. how do you explain that. i used to think the way you do, that dents could only come from low pressures. but i learned something with that other post.
The only example I can give regarding the other post you mention is:
A while back I started playing with a 25WSM wildcat for a mate of mine, we had quite good succes with most powders ; H4831sc, RE19, RE22 and H4350 and 180gr Accubonds. I obtained starting loads for the above powders out of a US mag, but when we didn't have any info for a particular brand of bullet I had to extrapolate starting loads.
Right from the get-go we had dents and sooting all the way down the brass, my pressure sensor readings were errattic and varied by as mush as 25000psi,some higher than SAAMI max and some lower than SAAMI max, with the same powder charge, I have never seen that or heard of it before, so I spoke to another handloader that has the same cartridge and he told me that there was a very fine line where this particular case design functions correctly regarding pressure, if it is onlt slightly less than max pressure, it tends to go off on pressure excursions almost causing the dreaded S.E.E, the worst powder offender was RE22, a difference of only 2 gr caused the above example. This is obviously caused by pressure and not any other mechanical or rifle fault, there is no long throat or headspace problems with the rifle.
I cannot expalin it, and others I have spoken to can't explain it either, but one thing I do know is that Winchester had the same problem, that is why it was never introduced, even though it was on the drawing board for the new WSM cartridge. They had to go with the WSSM concept for it to work.
Cheers.
MagnumManiac.
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  #27  
Old 12-01-2008, 09:36 PM
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Re: Brass troubles

A while back I started playing with a 25WSM wildcat for a mate of mine, we had quite good succes with most powders ; H4831sc, RE19, RE22 and H4350 and 180gr Accubonds.

the high pressures might be because you loaded those 180 accubonds in that 25 cal! OK, a little joke there.

i tend to agree with you on the absense of this sort of thing in Weatherby's. i'm sure there are quite a few of them with bullet release before rifling engagement. why do some and why don't some....that is the question!
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  #28  
Old 12-02-2008, 03:57 PM
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Re: Brass troubles

Magnum.....can you tell us about those tests that show the bt's and abs make more velocity at less pressure.......what kind of pressures and velocity comps do you have to other bullets in the same gun?

Last edited by kraky2; 12-02-2008 at 05:22 PM.
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