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I've a new to me, Marlin 1894, for which I won't be reloading (as I really don't have the room at home, tiny modern house). It has a new (probably less than 250 rounds) microgroove barrel.

I've been testing a couple of types of factory ammunition, all .38 special

Magtech FMJ Flat 158gn
Magtech LRN 158gn
PPU Lead SWC 158gn


Last night I noticed a number of what looked like tumbling rounds at 10-15m (was practical night) using the PPU SWC. Is that normal?

I final test @10m had 3/11 PPU rounds showing rectangular holes/tears, while all the Magtech LRN holes were nice and circular.

Is this just a thing that happens? I've never really had any ammunition or rifles (.22lr/303) which have exhibited key-holing before.

First check the barrel for leading.

Either way the bullets are too small diameter or too hard not setting up in the micro groove rifling. Such rifling needs a throat diameter soft bullet.

strangesam wrote:I've a new to me, Marlin 1894, for which I won't be reloading (as I really don't have the room at home, tiny modern house). It has a new (probably less than 250 rounds) microgroove barrel.

I've been testing a couple of types of factory ammunition, all .38 special

Magtech FMJ Flat 158gn
Magtech LRN 158gn
PPU Lead SWC 158gn


Last night I noticed a number of what looked like tumbling rounds at 10-15m (was practical night) using the PPU SWC. Is that normal?

I final test @10m had 3/11 PPU rounds showing rectangular holes/tears, while all the Magtech LRN holes were nice and circular.

Is this just a thing that happens?

Most of the .357/.38 underlever's in our club (mix of Marlin, Rossi & Henry) don't seem to like any SWC or flat bullet ammo, only LRN's.

What Dromia says.
Bullet nose shape is irrelevant on sub-sonic rounds, unless there are feeding issues.
Bullet fit in the throat is everything.
Fred

As said, soft and large is the way with Marlin micro-groove barrels as a rule of thumb. As you're not going to reload, jacketed factory for you.

Thanks, sounds like its not unusual, just ammo sensitive.

I know the FMJ Flat 158Magtech works, so I shall buy some more of that.

I find 10m is too close to stabilise , try 20m groupings

If you reload. you might be able to afford a larger house.
Fred

FredB wrote:If you reload. you might be able to afford a larger house.
Fred

Worst case I probably spend £2k per year on ammo. Even if I saved 50%, thats longer than my remaining lifetime to afford a bigger house. (something 4 bed in a half decent area near me starts at £500,000 and goes up rapidly).

My best hope is inheritance, the lottery, or the wife moving up the career ladder again.

My Rossi 92 would do the same at 25m with ppu swc.
I reload now with the ppu brass and 158gn rnfp GM lead.
Problem gone. it just didn't like semi wad cutters.