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300WM case life

 
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  #1  
Old 01-18-2004, 05:48 AM
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Location: Scotland.U.K
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300WM case life

Can any one give me an indication of case life with new Lapau brass.
Using 190smk 2950fps
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Old 01-18-2004, 07:08 AM
JR JR is offline
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Re: 300WM case life

Hello from just up north there Aficionado,

Case life on the Lapua? Hard brass that is, but what have you found to be the case? I could get around 6 decent reloads from W-W brass, and have been eyeing the Lapua....

JR
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Old 01-18-2004, 09:03 AM
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Re: 300WM case life

Aficionado & JR,I use the lapua 300winmag brass in my modified 300 win,it holds 2 grains of water less than std.It's good in the pressure area aswell as being quite useable for a fussy L/R benchrester like myself ..My speeds are 3230fps with a 187 gn projectile and is diffently high pressure,i have up to 10 reloads on some and are still good,but not without some work to refire..HHope this helps..JR..Jeff Rogers
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Old 01-18-2004, 09:08 AM
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Location: Austin, Texas
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Re: 300WM case life

I have had 8 or 9 "safe" reloads on the Lap brass. I have a rail gun I use to test my brass life, and I pushed a Norma Lap case with this bullet in my big 300 to 19 loadings before case / head sep, so about half that would be "safe". Web starts to thin around this area by about .005 - .007, so I would be careful. These were all loads within spec of the manual so that's no too bad. As stated above, the Norma brass is pretty hard, so anneal, anneal, anneal and you'll get better life. As for Win - Western brass, i've been getting about 7 or 8 loadings. Have pushed to 15 with the rail gun before rupture in the past, so I would consider about half that safe. Good luck bro.

TH

[ 01-18-2004: Message edited by: Austin ]
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Old 01-18-2004, 11:16 AM
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Re: 300WM case life

Hi Gents
Im just starting out with the 300wm going to try R19 for powder, 190smk, at 2950fps,hoping to get good velocities with not to much pressure.
Had very good case life with Lapau in 308 and thought it was a good place to start .
J.R..... Minsterley has 300 Lapau brass
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Old 01-18-2004, 02:43 PM
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Re: 300WM case life

One more thing you may try: I have noticed that this case seems to LOVE a near full capacity and I switched to H1000 and 872 with excellent results in 4 out of 5 300WM rifles. Also, I have been only neck-sizing this brass and that seems to give me 2 or 3 more safe loadings before I start to see problems with cross-sectioned cases.

TH
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Old 01-19-2004, 10:57 AM
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Re: 300WM case life

Probably preaching to the choir to most of you, but with 300 WM, there are a couple of things you need to know before reloading it.

1. The 300WM is probably the only caliber out there where SAAMI standards are not held to by different manufacturers in the U.S.
2. A study of all belted magnums held the shoulder/datum line length to a minimum from the belt with the exception of the 300WM in both chambers, in brass, and reloading dies.
3. Chamber reamers from different sources can differ on the shoulder/datum line lengths and factory rifles can vary up to .035" to the datum line which makes reloading the 300WM a different story.
4. Brass is different as well, with .015" between different manufacturers. This has been offered as the reason 300WM chambers are so sloppy.
5. Reloading dies from different sources can be as varied as the brass on lengths.
6. Shooting rifles built in this manner often produces inconsistent case stretch, (datum line headspace length) shooting the same lot of ammunition in the same shooting session.
7. This produces inconsistent reloads, extreme deviations, and poor accuracy when not returning the datum lines to the same length when reloading by neck sizing only.
8. Full length resizing to return all the brass to the same datum line length overworks the brass and speeds up case head separations.

One US Customs' gunsmith spent a large number of dollars on reamer designs and came up with the 300WM reamer dimension the US Army AMU still uses today. I have his original reamer in my possession.

Several years ago, a guy approached Dave Brennan, Precision Shooting about the problems with 300WM's and the above issues. Brennan had several LR gunsmiths respond in a letter type forum. Many were unaware of the problem.

Before the 300WM, the US Military shot the 30-338 Winchester Magnum cartridge wildcat, headspacing the cartridge both on the belt and datum line. Excellent accuracy was obtained with this method.

The Accuracy gunsmiths who responded to Brennan's query determined several things based on the information provided.
1. The shooter picks a lot of brass. The gunsmith averages 10 pieces of the brass for datum line length. The smith lathes off the belt on a couple of pieces of the brass that are the absolute longest in the lot. Uses them for headspace gages.
2. The gunsmith will cut the chamber in to headspace on the now beltless brass. Generally the reamer will not go in far enough to start the belt cut.
3. The belt cut is then done on a lathe to a chosen headspace based on the lot of brass' general average headspace on that lot of brass.
4. Given this method, using new factory loads, the pressure could be expected to be slightly higher but not to a dangerous level.
5. Using this method, reduced the stretch of the 300WM brass, increasing reload numbers, and consistency in accuracy.
6. Using the shorter once fired brass, reduced the maximum load usable in the 300WM but maintained the velocities with load developement. The number of loadings in this type set-up can run from 15-20 reloads.

The downside is generally having to have a reloading die made for the rifle that meets the dimensions of the shorter fired cartridge.

Starting with a factory rifle, obtaining a chamber casting, and using a case gage to determine the maximum chamber dimensions, will give you an idea about the approximate number of reloads you may expect from your rifle with your brass.
With a case gage, the casting, and your chosen lot of brass, you can determine the stretch of a fired case and also decide if your reloading dies will over work the case when resizing.
Lots of trouble, but worth the effort for max accuracy with a 300WM.
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