Alex Wheeler
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I think some make a .750 bolt to thicken up the bolt nose ring but do not necessarily add lug size, in some cases they reduce lug size in the action and bolt due to having a larger bolt body.
Threads are overrated
- Thread starter carlsbad
- Start date
DaveTooley
Gold $$ Contributor
After getting some new information The Kelbly Atlas while having a larger diameter bolt, really isn't an improvement over a 700. The increased diameter was probably to accommodate an extractor for the larger case.
Ruger went the other way with the 338 RPR. The bolt face OD is still ~1", but the bolt is relieved behind the lugs to 0.600".
To your point, that and the third lug double the lug face contact area over a M700 or M110 and it uses a 1.125"x 18 thread. The tenon isn't as strong as a large shank Savage, but the lug area is way up. I'm using the RPR as an example of a modern design purpose built for the 338 Lapua by an organization with far more sophisticated engineering capabilities than the aftermarket receiver companies. We don't know if its to address a problem with 338 Lapua M700s or so they can use peanut butter for their receivers though.
If it's the lug area, and 1.060" tenons are OK, a .750 bolt body reduces lug area? Which action is that?
I'm still not clear on exactly what the problems you've seen are? That .750" bolt diameter criteria has never made sense to me, especially if we're discussing Remington pattern clones. Or anything with a 1.060" tenon for that matter. I'm getting from this thread that your 1.060" comments in the past weren't implying that the barrel tenon bursting or pulling out were your concerns, it's that it sets the maximum OD of the bolt face and is a limit to the lug area.
Is the issue lower lug setback, some kind of failure of the bolt contact faces, or something else?
Do you think it's inevitable each time one of these guns is chambered in 338 Lapua, or is it only going to be a few Darwin Award candidates you're turning loose with a maxed out design, 338 Lapua brass, and internet velocity expectations? Is it that one guy, or if you do 1,000 barrels you'll have a 100 problems, or eventually all of them come back to you?
carlsbad
Lions don't lose sleep over the opinions of sheep.
Thank you all for your concerns for my safety. I'm pretty sure I'm the only Licensed Mechanical Engineer in this thread.
We've gone off track here a bit and I'm ok with that but lug area is probably not as important as the effective shear area of the attachment of the lug to the action. Making the bolt 3/4" may or may not affect this shear area. Single shot actions have a much larger shear area for the lower lug than repeaters.
That said, my change to 1.125" threads had nothing to do with the lugs. I did not mean to imply that I think 1.062 x 16 threaded actions are not ok for 338 lm. I have one in my gun safe now made by remington and they have a staff of very conservative lawyers.
--Jerry
We've gone off track here a bit and I'm ok with that but lug area is probably not as important as the effective shear area of the attachment of the lug to the action. Making the bolt 3/4" may or may not affect this shear area. Single shot actions have a much larger shear area for the lower lug than repeaters.
That said, my change to 1.125" threads had nothing to do with the lugs. I did not mean to imply that I think 1.062 x 16 threaded actions are not ok for 338 lm. I have one in my gun safe now made by remington and they have a staff of very conservative lawyers.
--Jerry
Jerry sorry to impose on your thread. But Alex doesn’t making the bolt oversized and leaving the lugs the same size make the action weaker? That’s less surface area on the bolt lugs which would be more dangerous?
Having said that I have built a 300norma on a defiance .750” bolt OD action. It was fine but I also built it for a friend who does understand reloading. Could be a nightmare if they messed up on a powder.
Alex Wheeler
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All else equal, smaller lugs will have less shear strength and higher pressure (psi) on the lug seats even if the total load is the same. When we increase bolt face diameter we also increase total load. Increasing total load while decreasing lug surface area does not make any sense to me. I am not worried about safety but I am worried about lug seat stability. When you set lugs back in an action usually its not equal, there goes your perfect lug contact.
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carlsbad
Lions don't lose sleep over the opinions of sheep.
Dusty Stevens
Shiner
There sure isnt much for the 3 rings of steel if that concerns you.
Alex Wheeler
Site $$ Sponsor
The HR has pretty large lugs. Same surface area as the Bat M and Surgeon XL. Its a tough action, I have hammered the HR worse than any other action I have owned, scary pressures...
I’m not trying to stir the pot just want to hear people’s opinions about. Like I said I made one on a defiance and was a little nervous about it. But I guess it goes back to savage small thread and large thread with the WSM issue.
Is it unsafe or just causes more bolt trust on lugs that are smaller?
Is it unsafe or just causes more bolt trust on lugs that are smaller?
Pictures are worth a thousand words!
No, I'm another. Also work in the power industry. I've been a PE since '85 and consultant since '94. I work for other engineers. I'm not concerned at all for your safety and it has nothing to do with my stereotypical engineers lack of empathy.
The reason I've commented here is I've done similar projects to what you opened this thread with. This is for my personal use as a test mule for 338 Lapua based wildcats. It's going to get it's third barrel soon. I measured it the last time it was apart and the lower lug was where I left it.
As an old engineer, I know that some of the most important information I can have during the design phase is service histories. I only have 2 of these. What I'm looking for is a professional gunsmith who did a few of them and had them all come back for the same reason, or did a few hundred of them and enough came back they stopped doing them. These being 338 Lapua barrels, not receiver mods.
Something I had to learn a few times as a young engineer was just because someone had the why something was breaking wrong, didn't mean it wasn't breaking. I'm trying to head that off as well.
The reason I do this modification has more to do with the limitations of my threading skills than making the tenon larger. I take the threads to the large shank Savage 1.125x20, using a large shank receiver as a pattern.
There sure isnt much for the 3 rings of steel if that concerns you.[/QUOTE said:
Finally a thread worthy of discussion!! I don't see the logic of this conversion, but am enjoying the arguments from both sides.
Paul
Paul
Fair enuf.
No riflesmith I know of, will build a .338 LM on a standard M700 action. It ain't about tenon diameter, it's about bolt thrust. Lugs...
The .300 Norma Mag operates at higher pressure than the Lapua (4400 vs 4200 bar) with the same case head diameter and therefore has more bolt thrust than the Lapua.
76,500 N vs 71,900 N, prox..
It's your forehead, behind the bolt.
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