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Twist Rate for 300gr SMK's in 338/300 RUM?

 
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  #8  
Old 12-29-2005, 12:45 AM
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Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

LongrangeSupply,

Just curious if you have any documented cases of a Rem 700 based 338 Lapua coming apart with the use of proper 338 Lapua load levels?

Most of the modern receivers I am aware of are proof tested at twice their working chamber pressures so we are dealing with pressures up to or over 100,000 psi.

Now I can tell you that you will pierce a primer or loosen a primer pocket well before you get anywhere near this level of pressure. In fact more cases will start to loosen their primer pockets in the 65,000 lb range to some degree depending on their chamber design and fit.

I will also say that if you are loosening the primer pockets on a 338 Lapua case no matter if its as the standard 338 Lapua or any wildcat based on that case, you are pushing the pressure far to high and need to dramatically reevaluate your loading practices.

One aspect of the Savage barrel is that it has a relatively small diameter Barrel shank diameter over the shoulder area of the chamber, Over 1/4" smaller in diameter then the Rem.

Also keep in mind that there was a Savage rifle chambered for the 7.82 Patriot. This Lazzeroni short magnum has a lapua case head diameter.

I do not advocate using the Savage with the Lapua class case but I do the Rem 700 when used properly in properly fitted rifles.

There have been thousands of Rem 700s built and chambered for the Lazzeroni short actions and long actions which all use nearly the same case as the Lapua only in a slightly improved design.

There have also been alot of Rem XP-100 handguns chambered for the Lazzeroni short action magnums and used to full potential with no problems at all.

Ever measure the barrel shank diameter and receiver diameter of a Sako TRG-S? I suspect the barrel shank is less then a Rem 700 and the receiver no larger.

Same with the Wby MkV receiver. Same barrel shank diameter and receiver diameter.

Again, a factory Rem 700 receiver, certainly not, but a properly squared receiver with 100% lug contact and a precise fitted barrel and min spec chamber design with responsible load levels, you bet.

Kirby Allen(50)
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Old 12-29-2005, 06:05 AM
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Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

LRS,

I to have built several 338 LM's on Rem 700 receivers with no problems at all. I believe that all other things being the same that the critical area is bolt lug shear strength and not barrel shank diameter that is encapsilated by action diameter. Actions are proof tested far beyond the levels of responsible handloading. I have no issues for action strength. My concern for strength stems around a mistake or repeated firing at near proof level loads. We all know guys that shoot loads that ruin the brass in 1 firing, in the interest of max velocity, despite repeated warnings against it. These guys will usually set the lug back before anything and create an excess headspace problem. Then they have a case rupture or 2 and come to talk about the poor work you did on their rifle. Since you are obviously fall on the safety side of the line I wouldn't have any concerns about building the LM on a 700. The LM in the 700 has some issues that need to be addressed by your smith when they build the rifle but action strength is not one of them.
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  #10  
Old 12-30-2005, 07:12 PM
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Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

I am not saying that I think that a normal pressure load is going to fail in a Rem 700 or a Savage small thread action chambered in 338 LM but the facts are clear as I understand them, that it is without question less than a 100% setup safety wise.

The Savage testing giving below 100% safety margin with the WSM's had absolutely nothing to do with lug strength, but rather chamber wall thickness. It is in marginal territory with the WSM and even more so with the Lapua. Remington barrel shanks are thinner than Savages behind the shoulder and thus would be more prone to failure than the Savage barrel in that area. I have also talked to some smiths who are seeing chamber wall stress cracking in Rem 700's chambered in WSMs and will not install WSM barrels on them. Since the Lapua Mag has even thinner walls, I just don't want to go there myself.

Based on that knowlege, I won't be chambering any 700's or small thread Savages in 338 Lapua.
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