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Howa .338 edge?

 
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  #22  
Old 03-06-2011, 04:37 PM
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Re: Howa .338 edge?

Its not case length or capacity that determines how it stresses a receiver. Its case head diameter and chamber pressure.

I am in agreement with this, good thread.
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  #23  
Old 03-06-2011, 04:49 PM
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Re: Howa .338 edge?

nwolf I would look at kriby's 338 ultra max I just got one from him and did some load's to day and was very impressed 300gr smk running out at 3032 in remington brass and 3091 in fed brass and it is based of the 375 rum case
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  #24  
Old 03-06-2011, 05:18 PM
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Re: Howa .338 edge?

Quote:
Quote:
Originally Posted by Fiftydriver View Post
MontanaRifleman,

Those cases may have been true for older Howa rifles. I can not dispute that. BUT, howa now chambers their rifles in the 375 Ruger which is a RUM case shortened to 2.500 in length and has a very similiar shoulder design as the RUM. Basically its identical to the 375 RUM except that the case is 0.350" shorter. As such, it will generate EXACTLY the same amount of bolt thrust onto the receiver as a full length 375 RUM will. The stress imposed onto the receiver is based on the size of the case head, nothing more or less. The larger the case head, the more bolt thrust because the same amount of PSI is being applied but over a larger area so the total thrust is greater.

I am sure that Howa has fully tested their receiver with the 375 Ruger and proven it plenty capable of this level of bolt thrust. If it will handle this, it will handle the RUMs.

To that same point, the 338 Lapua has a significantly larger case head diameter and area. As such, 65,000 psi in the Lapua will produce dramatically more bolt thrust then a RUM loaded to the same 65,000 psi.

This is why you really have to beef up a receiver and barrel to use a 408 CT class wildcat. Larger case head diameter imposes MUCH higher bolt thrust levels to the receiver even at same chamber pressures.

There is a reason that the 50 BMG is loaded to 55,000 psi. Even though the receivers are huge, if you up pressures to the 65,000 psi level that is common with todays magnums, you will generate a bolt thrust that would stress even the large BMG class receivers.

Its not case length or capacity that determines how it stresses a receiver. Its case head diameter and chamber pressure.

Another example is the 223 Rem. I have studied tests with this little round where loads were driven up to nearly 85,000 psi and the only thing that happened was pierced primer pockets with no receiver damage at all. In the same test, they took a larger diameter case, I believe it was a 300 Win Mag and loaded it to this same pressure range and the bolt lugs were set back to the point the receiver was spoiled. If that level of pressure was put in a Lapua case head diameter, the receiver likely would fail or at least be locked solid.

As far as the Howa to Remington comparision. I like the Howas but they are no where near as easy to work with. Barrels can be a serious pain to break loose. I have had several that I could have stood on my 6 foot breaker bar and still not turned them loose. I certainly would never do that as you can tweak a receiver easily if you force it so in those cases I simply cut the barrels off and bored out the barrel segment left in the receiver. The funny thing, once the shoulder of the barrel had been machined off, the barrel shank often can be turned out by hand???? Go figure. Not sure what those guys do to make some of the barrels so tight but some are amazingly hard to break loose.

The receivers are not that hard to accurize but the bolts are a bit more difficult, just need to make up some custom tooling and fixtures to do it.

now if your just doing a simple barrel replacement and perhaps lapping the lugs and no full accurizing, no problem.

The Rem 700 trigger options are much better all around. magazine box options are also better for the Rem 700. Its also easier to bed a Rem 700 as well. In the end, for a precision rifle build, the Rem 700 is hands down superior but the Howa is a much better receiver and rifle then most give them credit for.
Kirby and Darrin, thanks for education on the bolt thrust, which is new info for me. I am still having trouble understanding how a 375 Ruger will have exactly the same bolt thrust as a 375 RUM just because they have the same bolt face. But for now, I'll take your word on it.

On the 700 vs the Howa, my approach to doing a budget build is getting a good action/stock combination like a Sub MOA Vangurd, Sendero, or Mark V Accumark, etc., and just doing the basic accuraization of trueing the action, lapping the bolts, skim bedding and good to go. If I start replacing bolt's and triggers, etc, I might as well just get the custom. so from this angle, i think the Howa is a better choice with it's one piece bolt, integral recoil lug, ported blot sleeve, m16 style extractor, etc (some will probably debate those features.. oh well) the trigger on my Howa is much easier to tune also. And both my 770's and Howa are tuned very nicely for my purposes and my Senderos are good .5 MOA rifles to 500 yds and last I shot the Howa 7RM it was .3 @ 100. So as where some of the other upgrades might be nice, I am more than happy with the basics, especially in the Howa.

Interesting insight on a smith's perspective of the Howa.

Thanks, Mark
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  #25  
Old 03-06-2011, 06:32 PM
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Re: Howa .338 edge?

So then it would be true that the .338 Norma Mag has the Same bolt thrust as the .338 Lapua, therefore it not the best decision to build one on a remington 700 action (or Howa of that matter)? so then the main purpose of the .338 Norma becomes moot, that is being able to use a r700 action. I suppose it still offers a shorter barrel compared to the lapua, RUM and edge.

good thread.
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  #26  
Old 03-07-2011, 10:59 AM
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Join Date: Dec 2010
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Re: Howa .338 edge?

As for the .338 sin. You say there are other cartridges that are the same. Do they also fit the howa action without any modification? This is an honest question as I've never heard of them. If they do then I see why you question its existence. If not, then what's your question?
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  #27  
Old 03-07-2011, 06:51 PM
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Re: Howa .338 edge?

The 338 Norma Magnum, if loaded with the same bullet to the same pressures as the 338 Lapua magnum will produce nearly exactly the same bolt thrust on the receiver.

I used to build alot of Rem 700s modified to be chambered for the Lapua class chamberings, namely my 7mm Allen Magnum, 300 Allen Xpress, 338 Allen Xpress and 375 Allen Xpress.

I did some testing with a stainless steel Rem 700 with the 300 AX and after 700 rounds down the barrel, most of them being the 240 gr SMK loaded to 3200 fps in a 30" Lilja 1-8 twist barrel. I pulled the barrel and measured the receiver for bolt lug set back into the receiver supports. After 700 rounds, the stainless steel receiver had roughly 7 thou of bolt lug set back. Bolt lift was starting to get tight at around 500 rounds down the barrel and really noticable after that. Nothing that kept the bolt from opening but it did not matter what load I used, bolt lift was stiff, extraction was effortless, pressures moderate.

This prompted me to check for bolt lug set back.

After seeing this, I fitted the same barrel to a Chrome Moly rem 700. Hammered down another 700 rounds and then pulled the barrel to check the bolt lug setback. Less then 2 thou. Bolt lift had remained excellent throughout testing.

The harder chrome moly steel resisted bolt lug set back much better then the stainless steel receiver when using the same load and chambering. More then three times less set back. At this point I decided to use ONLY chrome moly Rem 700s for my Lapua class builds.

A year or so passed and a customer sent me back his 7mm AM that had been built on a chrome moly receiver. It seems he had been loading this rifle up to the limits of the Lapua case with the 160 gr Accubond and was getting north of 3550 fps in a 30" barrel length. After 300 rounds, bolt lift had become very heavy with all shots. Hearing this I told him to stop shooting the rifle and send it back to me for inspection ASAP.

He did, I pulled the barrel and the bolt lugs has set back into the receiver supports by 10 thou!!!!!

Now these loads that had been used were far over what I had recommended. At that time, I had only loaded the 7mm AM up to around 3450 fps max in the Rem 700 based rifles. He took the load development higher and since there were no pressure signs with his loads and the Lapua brass, he figured they were perfectly safe.

This made it clear that the Rem 700 was not a good choice for this class of chambering. If the Lapua class chamberings are loaded to the 65,000 psi range, a properly built Rem 700 Chrome Moly receiver will handle them easily.

The problem lies in the fact that the Lapua case can support dramatically higher chamber pressures then this and when that case strength is combined with a bit of an unexperienced handloader, the receiver is stressed more then it was ever designed to be.

It was also because of the very strong Lapua case that I have done all my load development for my wildcats based on the Lapua case with the Norma Brand of brass which is significantly softer then the Lapua and will loosen primer pockets at nearly identical pressures and the Reminton RUM brass cases, which is in the 65K to 68K psi range. Once those loads were determined in the norma brass, I could then move over to the Lapua brass and get extremely long case life.

Seeing the potential of the Lapua case to handle pressures that were far above the design goals of the Rem 700, I made the decision to stop offering my Lapua class wildcats on that receiver platform and that was the start of the APS Raptor receiver.

In comparision, I have inspected several 338 Edge rifles with well over 1000 rounds down the barrels in both chrome moly and stainless steel and neither had bolt lug set back much more then 2 thou if that.

Hope this puts some perspective on what can happen when the Rem 700 is overloaded with a Lapua class chambering.
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  #28  
Old 03-07-2011, 10:16 PM
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Re: Howa .338 edge?

That makes alot of sense, thanks Fiftydriver.
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