338 Lapua in Rem 700 Bolt Thrust Question...

J

Joe Woosman

Member
I've heard and seen the reports on the dangers of the Lapua in the 700. I'm not disputing them. Today I was measuring some cross sectioned cases I had laying around. The inside of the Lapua is only like .010-.015 larger than a Winchester WSM case. The wall thickness near the web, and the web itself is considerably thicker.

It is my understanding that bolt thrust will be the result of chamber pressure applied to the area of the internal diameter of the case at the base. There is only 5-10% difference in the two cases I measured. I don't believe the outside diameter of the cases means squat, (to bolt thrust). My question is: How marginal is a WSM case in a 700? Does the weaker WSM case just reveal high pressure before critical thrust is achieved? Just curious.
 
Something to think about isn't it. The question should be "When is 10% more too much?" Before RUM's and WSM's I built a lot of rifles on the 404 case. We road them pretty hard in those days and I did see some lug setback on 700's. Some standard .532" cartridges had some setback also. The WSM class of cartridges is as large as I'll build on a 700 class action with an 1 1/16" diameter barrel tenon.

Dave
 
The Long Magnums in a Model 700

Shooting a long magnum single shot in a Remington 700 is one thing, shooting them using a magazine feed is another.

If you are using a 700 long action with a .698"-.701" bolt body, and lugs 1.0625" there is a minimal amount of steel holding that magnum in the chamber.

All of the custom actions made for the large magnums have at least .750" bolts and the better ones have larger and/or longer bolt lugs and longer tenon threads.

Making the magazine work with bullets heavier and longer than 200-250 grains requires the back of the action to be machined away and the bolt stop be machined back also.This does nothing to strenghten and already minimal strength action.

Building a .338 Lapua on a Remington 700 may be penny wise and pound foolish.

Just my two cents worth.

Nat Lambeth
 
My problem is with tenon diameter, not bolt thrust. IMO the small tenon of the 700 doesn't resist the pressure well enough, it swells which leads to sticky extraction.
 
I have a factory Remington 700 in the shop that probably came out of the custom shop as the barrel is engraved with the caliber markings instead of roll stamped. The rifle has an Accuracy International standard length .338 Lapua magazine. The freebore of the chamber is long enough that you can't seat a bullet to fit in the magazine and touch the lands. I think Remington did this on purpose as a longer freebore drops pressures. To buy one of these to rebarrel, a shooter would be better off to get a Stiller Tac 338 action and whatever stock they wanted. The Remington wholesales at around $1750 which would go a long way toward paying for a stock and action. The barrel tenon on the Remington could always be opened up to a 1 1/8" thread, but that wouldn't do anything about the .700 diameter of the bolt. After reading Dan Lilja's article on the 700 for large diameter cartridges, I was surprised that Remington modified their action for the .338 Lapua. Pressure wise the long freebore may have been their answer to pressure problems with it.
 
Mike wouldn't the long freebore reduce shot start pressure while you'd still reach pmax a few inches down the bore?

Knowing that jam will increase pmax...
 
AJ300MAG said:
Mike wouldn't the long freebore reduce shot start pressure while you'd still reach pmax a few inches down the bore?

Knowing that jam will increase pmax...
Click to expand...

Don't know enough about that to know for sure. Was thinking more along the lines of the Weatherby cartridges where Roy Weatherby kept lengthening freebore and adding powder thinking he was getting more velocity by lengthening the freebore. Instead it took more powder to get the same pressure as the freebore was lengthened. He didn't have a chronograph at that time so thought more powder meant more velocity.
 
Joe Woosman said:
I've heard and seen the reports on the dangers of the Lapua in the 700. I'm not disputing them. Today I was measuring some cross sectioned cases I had laying around. The inside of the Lapua is only like .010-.015 larger than a Winchester WSM case. The wall thickness near the web, and the web itself is considerably thicker.

It is my understanding that bolt thrust will be the result of chamber pressure applied to the area of the internal diameter of the case at the base. There is only 5-10% difference in the two cases I measured. I don't believe the outside diameter of the cases means squat, (to bolt thrust). My question is: How marginal is a WSM case in a 700? Does the weaker WSM case just reveal high pressure before critical thrust is achieved? Just curious.
Click to expand...

The outside dimension means a lot. If a case head separation occurs the thrust is calculated by the size of the chamber. I think the .750" bolt diameter to solve the three rings of steel issue is not a total solution. If the bolt body diameter increases and the lug diameter does not then the lug contact surface area suffers greatly. There is considerably more meat around a large shank Savage WSM chamber VS a Rem 700 than people realize due to the 1.120" tenon and the 20 tpi threads being less deep. I have built 338 Lapua's in Savage actions but would not with a Rem 700 and will no longer do it with Savage actions either. I consider the WSM to be the largest case suitable and even that is not great. The 50bmg I'm doing now doesn't have too much lug surface area either.
 
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