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"Use A Big Enough Gun!"

R-WEST

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"the spotlight of truth will cause the cockroaches of deceit to run for cover every time"
Rush Limbaugh

First, the tube of a Marlin has a bulge near the load gate area. Thus bulge is to provide more room for the cartridge to turn-into the magazine.
Now, with the bulge providing more space, the round that sits in that area has more room to slip side-ways under recoil( or any other movement with the rifle ie shaking, bumping it into something, whatever).
Sitting side-ways, the edge of the round's meplat is now closer to the primer of the round ahead of it. Under heavy recol, the meplat edge may hit the primer. A one-in-a million chance, like being struck by lightning, regardless to what "they" say.
As to the two basic designs of meplats (flat points) normally used, small and large.
Within the bulge, due to the extra movement, a small meplat sits on the other side of the primer, essentially away from it(Buffalo Bore Ammo uses the smaller meplats for this reason).
With a large meplat, it's too large to dent the primer to any degree to set it off. This larger meplat is larger around it's edge as compared to the size of the primer hole(Garrett's Ammo uses this larger meplat for this reason).
Both the large and small primers have their good points, and their supporters for usage.

Here is an update, since it appears, with this thread, some may not be aware of...

Bufalo Bore uses a small primer(with a small meplat, that sits away from it within the tube).
The primer pocket is deeper then normal, so the primer doesn't get smacked.
They uses a slam-fire resistant primer originally designed for automatic rifles.
Garrett's said they'd be eventually using the same brass/primers( and may already be doing so), which is made by Starline, as designed by Tim Sundles, who owns Buffalo Bore Ammo.
Now, you understand why a burst tube might happen and the new brass that eliminates this possibility.
Solution... use Starline 45-70 brass.
Also... gunsmith Dave Clay is trying to perfect a "tube eliminator" of sorts.
This idea, as invented by "E-John-O"(a Marlin Talk poster), uses a flat spring, which bridges the bulge within, in an effort to hold the rounds straight-line within the tube, and eliminate the sloppy movement. The "bulge" still works as designed, but the rounds are now held straight inline.
I hope this settles the mind some. ~~~Suluuq

Garrett, as of Christmas, is using nickel-plated brass with a SMALL primer. Brass is stamped "Garrett", I believe.

Pertinax
(who uses Win brass with a LARGE primer...)

The accident developed this way:

He had customized a Model 71 Winchester lever action by installing a heavy wildcat based on the .348 parent case. The magazine tube was replaced by a custom magazine tube made from electrical conduit tubing.

When the accident occurred, the magazine was fully loaded with heavy-charged rounds featuring Barnes (I think) round-nosed, soft-point bullets. Those cores were pure lead, as I recall.

This rifle was a hard-kicker. On his first shot, the recoil fired the second round in the magazine ahead of the action. That was sufficient to fire the rounds ahead of it. The conduit tubing, being much heavier than "factory" tubing, allowed quite a lot of pressure to build up before the tube blew. When it blew, it blew where his hand was holding the forearm. His hand was turned into rags. Many delicate and expensive surgeries followed.

Believe what you like and do as you like, but the warnings about using anything but broad, flatnosed bullets in tubular magazines are there for sound reasons.

Paladin

quote:

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Originally posted by Tanoose:
where have you seen the warnings against round nose bullets , the only warnings in the marlin manuals warn against some pointed and full medal jacket round nose bulletsAnd if you ask marlin or remington and winchester about there round nose bullets they say there perfectly safe.

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Should you decide to contact thoses you quoted, they'll likely say RN are fine with "TrapDoor loads, at 28,000 psi or less.
Beyound this, especially with loads 40,000+ psi, RN are considered taboo.
Of course, opinions, experience, whatever, may say other-wise.
Everyone's got their views, and will support them to the death. (just don't let RN help you with it. ) ~~~Suluuq