Short Actions 7x33 twist rate

[CharlesHunterSA]

What twist is used in the 7x33?

 

[bloorooster]

What twist is used in the 7x33?

Approximately 1-16”
1-401 mm metric

 

[CharlesHunterSA]

Thanks. That will be almost impossible to find now with the current barrel makers. Slowest I can now find is 1:12

 

[mattimoose]

1 in 12 should be good. Generally, the biggest problem with rifling is not enough twist for longer projectiles, a little bit faster twist for such a short projectile shouldn't hurt that much. You never hear of a bullet being "Overstabilized" by spinning too fast. Most barrel makers are making 7mm barrels with a .284" groove diameter and that seems to be more of a problem for 7x33.

 

[mattimoose]

In Canada, here, I often thought of using a .280 Ross Barrel for the 7x33. it is a little larger but the twist is more like 1 in 9 or 10. The diameter is correct. There has to be some take-off barrels out there and the shank past the chamber is still big enough for an L46 thread. every time I have found a suitable donor, on stripped Ross 1910 actions, people have an inflated Idea of what they are worth. I owned one for a while and discovered that 7mm Remington magnum brass elongates quite nicely in the .280 dies and becomes a ready source to make these thing shootable but the .287 bullets are always the hangup. When I win the lottery, I will have a .280 Ross with a 7x33 SAKO auxillary cartridge and I will post some targets to test our assumptions.

 

[stonecreek]

The nominal bore diameter for the Sako 7x33 was .286-.287". The .284 bullets I've fired in mine yielded adequate accuracy, but at 100 grains and pointed they are hard to fit in the magazine. If building a 7x33 from scratch I would recommend the 1-12" .284 barrel. Factory .287" bullets, if located, will swage down nicely as they enter the bore and no harm will result from shooting the very slightly oversized bullets.

 

[mattimoose]

Yeah, it's just like the .22 Hi-power. You can shoot .224, 70 grain bullets out-of it which will give you passable accuracy. It's just nicer to fill the grooves. I have a Valmet 412 in 5.6x52 under 12 ga. but found a box of Hornady .227s, so haven't had to .224 yet. I am still waiting on my 7x33 dies from Ellwood Epps. RCBS was way behind but Redding was able to give an earlier date. The Lee 7mm -130 grain mold I shortened has an as-cast of .287 and works well with the Lee liquid allox. It fits in the magazine and throws at about 79 to 80 grains. I am anxious to get the dies as well, to swage down some .350 legend brass as well, though I have enough Bertram and SAKO brass to cover. Part of me also wants to use the 50 Berdan-primed SAKO cases I have. I have about 200 of the tiny Berdan Primers too that came with the reloading tools and the couple of boxes of "Kokkovaipat" that got me started on this goose chase.

Beyond that, I still have a bitter taste in my mouth for that 7x33, L46 at Ellwood Epps that just went by. My friend told me about-it and at 1200 dollars I would have been-in but someone beat me to the punch line. I have been waiting for it to show-up here.

 

[mattimoose]

These77 grain norma bullets at .308 should swage beautifully to .286 and be very close in weight to the factory 78 grIn fmj

 

[paulsonconstruction]

I have been told, but have not confirmed, that swaging a jacketed bullet down that far can cause the jacket to separate from the lead core as the jacket will "spring back" ever so slightly while the lead will not. Have you done this before & have you ever run into this issue? Would be nice if this could work!