.257 Roberts Help

Tikka;

I'm not familiar with that gun, so a couple of questions.  What type of  bolt lock-up does it have?  Is it a shotgun type single lug, or a rotary with how many lugs?

RCBS makes small base dies for your type of application.  The weak point of the Rem corn-shuckers & semi-autos was extraction, the small base dies helped alleviate that problem a great deal.

In answer to your question though, Speer #13 data is all to the .257 + P level.  The cartridge notes say to reduce all loads by two grains if loading for a slide action rifle, which I presume means one like yours.  This reduction would then make the max charges for 120 gr Speer bullets as follows:

IMR4831, 43 grains.  760, 41 grains.  H414, 41 grains. IMR4350, 41 grains.  And RL19, 41 grains.  These proceed from highest velocity to lowest.

Just parsing the math, the velocity produced by 43 grains of IMR4831 works out to be about 2672 fps, and it drops from there.

However, considering your situation, I'd take a good long look at using the 100 grain bullets.  This gets the velocity up into the mid-2900's with either 760 or RL19, working the data the same way.  That still yields over 1000 ft lbs of energy at 300 yards, using the Speer 100 gr spitzer.  You may very well find that playing around with O.A.L. will bring the 100's into acceptably tight groups.

900F

Tikka;

Whether or not it would chrono the same isn't really the question.  It's almost certain though that both aren't loaded with the same powder.  In other words, it isn't the velocity that's the question, it's the vibes.

Everytime it goes bang, the barrel goes twang; it vibrates.  The trick is to get the bullet going out the muzzle when the barrel is at one of the two end points of it's cycle.  You know, fast in the middle of the swing & slows to a stop & then speeds up going the other direction.

'Cause if the bullet leaves the barrel in the fast middle portion of the swing, then the muzzle tends to kick the bullet sideways & induce yaw, which makes for inaccuracy.  This is where the old crap about a bullet 'going to sleep' came from.  Too hot addresses the physical strength of the rifle & components, not necessarily accuracy.

900F

  I load for a bolt 257 R and it like H-414, But I am going to try IMR4064 When my hunting season is over. I loaded for a 760 in 308 a few years back,And I had a hard time getting it to feed with reloaded brass, But I just made sure that my hunting loads were with factory fresh brass and i worked fine, Thats a rather rare little pump you have there. The newest American rifelman has a great article on the 760.

    ..tj3006

My 257 whitetail load is 42 grains of IMR 4350 with the Hornady 117 round/flat nose.  I shoot a 1976 m77 Ruger tang saftey model.  It shoots good, is moderate but not high pressure.  I reload for a number of older 760 pumps, most '06.  They are all very strong rifles and most shoot 1 inch with good loads, even factory.

That WT loaad in my 257 has grounded about 7 deer, all with one shot.  The performance is way better than one would normally expect from a quart inch 120 grain slug.  I think the amount of exposed lead on the flat nose helps lots.

BEAR