Cast boolits in a 5R bore?

[fatelvis]

I'm thinking of cleaning out the bore of my rarely used Rem 700 5R in 308, (extremely accurate with 175 SMK bullets), and trying for extreme accuracy with cast loads. Has anyone tried shooting cast boolits in their 5r? If so, do you think the different rifling helps or hurts accuracy with cast? Thanks in advance!

[Jack Stanley]

I had an old 700 "police" rifle that I think had that type of barrel and it was very accurate with cast .

Jack

[runfiverun]

treat it like a marlin micro-groove.
I have a 5-R in my Ackley and it shoots cast as well as my 4 groove not Ackley'd rifle.

[fatelvis]

treat it like a marlin micro-groove.
I have a 5-R in my Ackley and it shoots cast as well as my 4 groove not Ackley'd rifle.
So use a harder alloy and size to .001" over bore diameter?

[Outpost75]

So use a harder alloy and size to .001" over bore diameter?

NO! BORE diameter is the hole diameter before rifling, i.e. tops of lands

GROOVE diameter is the depth of rifling in the finished barrel.

But what matters to determine bullet size is fitting the bullet to the THROAT diameter ahead of the case before the rifling starts, easily determined from a pound cast, then measuring chamber neck diameter and brass neck wall thickness to ensure adequate release clearance in the chamber neck so that you don't blow up the rifle! If you forget EVERYTHING you ever read about slugging barrels and simply cast chambers from now on, and get bullets to FIT THE THROAT you will be far happier in the long run.

The limiting factor in safe bullet diameter is neck clearance. You MUST measure the neck diameter of the chamber on the cast. Most chambers have enough clearance ahead of a fired case mouth that a properly upset throat slug will get you a portion of the case mouth and its transition angle to the throat or ball seat, so that you can measure neck diameter at the mouth and throat diameter of the ball seat.

The loaded cartridge neck diameter must not be larger than 0.0015" SMALLER than the chamber cast at that point, to ensure safe expansion for bullet release. This is absolutely essential for custom target barrels which often have tight-necked chambers which require neck-turned cases. As a general rule the largest diameter of cast bullet which chambers and extracts freely, without resistance, will shoot best.

For instance in a .308 Winchester target rifle with .339" tight-necked chamber and using case necks turned to 0.012," maximum bullet diameter is determined by:

[neck (.339")-2(neck wall thickness 0.012)] - 0.0015 = 0.3135" for a "fitted neck" in which fired cases do not require sizing, but bullets will be held by case springback only. For necked sized fixed ammo, subtract another 0.0015" or .312" IF the chamber ball seat is that large. In a new barrel chambered for jacketed bullets, probably not. Min. SAAMI throat as on the pressure test barrel is 0.3105".

[fatelvis]

Thanks for the great advice. I don't know about the throat diameter, but I know its very long. I have never been able to seat the bullet to touch the lands yet, but being it's so accurate anyways, I'm not concerned with it. I hear this is common with factory Remington barrels.

[Jack Stanley]

I did a throat impression on mine and sized .0005" under that size , it worked out very well .

Jack

[runfiverun]

try 310.
a little more bhn doesn't hurt if your shooting a bore rider. [I actually use double the Sb and Sn with my silhouette type target boolits]
try for a load in the 1900 fps area. [17-18grs of 2400]

[fatelvis]

Thanks guys. God I love this site!