The next little thing

[Ardent]

Out to build a sub-4lb mountain rifle, and to aid in that using a tiny cartridge. Short list are .25-45 Sharps (right, with hammered in 80gr TTSX for display), 5.6x50 Magnum (left), .257x50 Magnum improved, or an improved version of standard 5.6x50 Magnum. Leaving out the 6mms only because I don't stock them on the bench, will be a .224 or .257. .224 will throw 70 grain GMXs (BC .350) from an 8 twist likely, and .257s will throw 80 grain TTSXs (BC .317). Ballistics would equal out as the .257 is more efficient at making fps from powder and the .224s carry slightly improved BCs over light .257. Bullet weights will be 70-90grs and need to be over 3,000fps.

It'll almost certainly be x50 based, needs to be a .375" case head due to action limitations though no doubt non-applicable suggestions will be kindly fielded. The x50 Magnum case allows the best the case head size can offer and on an all out ultralight build doesn't make sense to me to make a choice based on brass availability. Have 400 5.6x50 rounds to start that'll keep the gun warm. An improved variation seems sage for case life with those rare and often pricey cases. Goal is 3 1/2 pounds but we'll see what can be done.

 

[1899]

What action are you using? There was a fellow a while back that built a super-lightweight on a CZ action and an MPI microlight stock.

 

[1899]

Edit - I was wrong, it was on a Mk.X mini-mauser:

By the way, that picture looks like a 5.6x50R, is that what you plan on using, or the non-rimmed version?

 

[Ardent]

Hagn mini action in my build's case (1.25lbs), also hence the preference for the 5.6x50R Mag.

 

[conor_90]

Easy; the 25-45 and then sell me the reamer.

There's something about these that interests me:

 

[hoytcanon]

Angus, I'm not a fan od the .224" concept for your intended purpose... I love the concept, but I like .257" for this one.

P.S - is the 9.5X57 being scrapped for this or is this a new project?

I ask because that pair would make a real dandy set for your area.

Edit... I see that you are using a Hagn Mini... I'm glad because, I would like to see the 9.5X57 Ti finished.

 

[1899]

I know you passed over the 6mm, but I had great results with reduced loads in .243 Win with 85gr Partition. I suspect you would be able to match the velocity I was getting (not chronographed but probably ~2600 fps) and the bullet performed very well. I'd be worried about lower velocity and monolithics.

Near side:

Far side:

Prior to taking the "inside" pictures:

The load is 33.0gr of IMR4064, book velocity is 2809 out of a 24" barrel and I am shooting it out of an 18.5 barrel so my MV is probably somewhere around 2600fps.

 

[Ardent]

Naw the titanium 9.5x57 is done and pending import, and functionally no difference on game between a 70gr mono .224 at 3,200 and an 80gr .257 at 3100fps. All that matters with this one is shedding every ounce and maintaining trajectory, shots will be chosen like long range bowhunting.

Conor issue with standard .25-45 reamers is short throats intended for AR mag seating depths, in a single shot no reason for the handicap, can run a throater but if ordering a reamer might as well make it right the first time. And if one foot is down that path already of ordering a custom reamer... might as well be x50 Mag based for the mountains.

 

[Ardent]

I know you passed over the 6mm, but I had great results with reduced loads in .243 Win with 85gr Partition. I suspect you would be able to match the velocity I was getting (not chronographed but probably ~2600 fps) and the bullet performed very well. I'd be worried about lower velocity and monolithics.

Near side:

Far side:

Prior to taking the "inside" pictures:

The load is 33.0gr of IMR4064, book velocity is 2809 out of a 24" barrel and I am shooting it out of an 18.5 barrel so my MV is probably somewhere around 2600fps.

Very nice Kristian! The partitions are great killing bullets but the BCs suffer severely. No worries on the velocity as they'll likely leave the x50R's improved's muzzle at as much as 3,300fps.

 

[1899]

Very nice Kristian! The partitions are great killing bullets but the BCs suffer severely. No worries on the velocity as they'll likely leave the x50R's improved's muzzle at as much as 3,300fps.

Wow, I didn't think they'd get going that fast. That is getting pretty close to .243 velocity.

Are you planning on using a set trigger? Have you used a set trigger before? I bet it would help on such a lightweight rifle.

 

[hoytcanon]

Naw... and functionally no difference on game between a 70gr mono .224 at 3,200 and an 80gr .257 at 3100fps. All that matters with this one is shedding every ounce and maintaining trajectory, shots will be chosen like long range bowhunting.

True, but the 0.033" comes into play on target... If it twer me, I wouldn't put a .224 on 300 pound game... the TTH et al not withstanding... but that's just me.

 

[Ardent]

Wow, I didn't think they'd get going that fast. That is getting pretty close to .243 velocity.

Are you planning on using a set trigger? Have you used a set trigger before? I bet it would help on such a lightweight rifle.

Indeed Kristian the standard, respectfully loaded 5.6x50R pushes a cup and core 70gr to 3,100fps with factory ammo. Improved and warmed up 3,300 is the goal, it's a deceivingly capacious and efficient little case. No plans on the trigger but would be easy to have Martin add one, indeed have used them and appreciate their benefits but not entirely hooked on them yet.

 

[Ardent]

True, but the 0.033" comes into play on target... If it twer me, I wouldn't put a .224 on 300 pound game... the TTH et al not withstanding... but that's just me.

I'm of the opinion the game never notices the bullet's three sheets of paper in thickness bigger aside.

Honestly never thought I'd be adopting cartridge minimalism but really want the lightest possible rifle that can reach.

 

[1899]

Indeed Kristian the standard, respectfully loaded 5.6x50R pushes a cup and core 70gr to 3,100fps with factory ammo. Improved and warmed up 3,300 is the goal, it's a deceivingly capacious and efficient little case. No plans on the trigger but would be easy to have Martin add one, indeed have used them and appreciate their benefits but not entirely hooked on them yet.

Ah, I thought you were talking about +80gr bullets.

I love set triggers in the field - breathing heavy, awkward angle shot with no time to re-position, off-hand etc - this is where it shines. With such a light rifle and longish range, well the advantage of an 8oz trigger is obvious. Call me next time you are in town and we can go "plinking" with a set-trigger equipped rifle.

 

[hoytcanon]

I'm of the opinion the game never notices the bullet's three sheets of paper in thickness bigger aside.

Honestly never thought I'd be adopting cartridge minimalism but really want the lightest possible rifle that can reach.

How about the difference between 0.224" and 0.000"???

At some point it comes into play... otherwise we'd all be blowing kisses...

 

[Bartledan]

Tell you what:

Let me borrow one of your 84Ms, I'll reverse engineer it, and you can have a receiver made out of titanium.

Run boring old 243, then.

That sounds a bit like one of those university engineering challenges.

Score based on (velocity x grains)/(ounces)
Or (muzzle energy)/(ounces), with a max weight of 4 lbs scoped.

 

[Ardent]

How about the difference between 0.224" and 0.000"???

At some point it comes into play... otherwise we'd all be blowing kisses...

True, I put the cutoff at weight and speed though not diameter. I don't even see any real world difference from diameter between .338 and .458, my flat earth opinion it's only weight and speed that matter. I'd happily launch a 70gr 3000fps .177" into a goat's vitals if such a thing could be stabilized / not kill itself on bearing surface / yada yada.

Tell you what:

Let me borrow one of your 84Ms, I'll reverse engineer it, and you can have a receiver made out of titanium.

Run boring old 243, then.

That sounds a bit like one of those university engineering challenges.

Score based on (velocity x grains)/(ounces)
Or (muzzle energy)/(ounces), with a max weight of 4 lbs scoped.

Been there before with Stuart Satterlee when I started tweaking to get the action I wanted, hope your bill's less! In all seriousness, I'm in if you know the folks to machine it, but I'd bring a different action to you.

 

[AP]

Sounds like you are re-inventing the .22 savage Hi-Power (maybe trimmed a little).. Newton would be pleased

 

[Superbrad]

Why not build a .22 cheetah and launch 50 gr projectiles at 4300?......

 

[Bartledan]

True, I put the cutoff at weight and speed though not diameter. I don't even see any real world difference from diameter between .338 and .458, my flat earth opinion it's only weight and speed that matter. I'd happily launch a 70gr 3000fps .177" into a goat's vitals if such a thing could be stabilized / not kill itself on bearing surface / yada yada.

Been there before with Stuart Satterlee when I started tweaking to get the action I wanted, hope your bill's less! In all seriousness, I'm in if you know the folks to machine it, but I'd bring a different action to you.

I wouldn't charge you a dime... I'd just see we got two made when we got to that stage

My buddy can make anything, does it professionally!