Is there a standard acceptable freebore? I'm working on loads for my Custom 405 again and am looking for an acceptable freebore for calculating C.O.L for different bullet types.

Freebore can run anywhere from .000 to god knows what, depending on the reamer used to chamber the rifle. If your gun is a custom you should be able to contact the gunsmith that chambered it and ask him what the freebore of his reamer is. There is no standard freebore for any ctg. that I know of, and any reasonable freebore is acceptable, depending on the bullet being used. Use of something like the Stony Point guage, or even closing the bolt on a dummy round will give you a very good idea of the O.A.L. to the lands for a particular bullet. The O.A.L. should be measured with a guage that will give a measurement to the ogive as bullets vary in length from the base to the actual tip.

I think closing the bolt on a dummy cartridge is the way to go, better than all the numbers you could crunch. In one of my rifles the freebore is very short. I'm experimenting with my 404 Jeffery since loading up a bunch of very blunt faced, long ogive bullets on the crimping groove (Rhino bullets) and having a bullet stuck in the barrel the first time I slammed closed the bolt. The bullet on the dummy round should be able to move a little so don't seat it into a tightly sized neck or a crimped case.

Ok maybe I'm not thinking right here. I thought freebore would be determined by seating depth and shape of bullet. Assuming no crimping requirements, a Spitzer could have a C.O.L. longer than a FN. A Spitzer could actually have the nose of the bullet into the rifling area but not actually engaging them where a FN would engage the rifling almost immediately. Thus a cartridge loaded with a Spitzer would have a longer C.O.L.? Right??? hehe.

I guess I'm asking how far a bullet should travel before it engages rifling on a normal basis. I realize there are schools of thought on this and that with the proper charge you can even seat a bullet so it engages the rifling when chambered but I'm not looking for that type of info. Just some guide to get started.

You are confusing two things:

1) freebore: this is an attribute of chamber, and describes the distance from the end of the case part of the chamber to the start of the rifling.

2) distance to lands: the distance the bullet can move from its position seated in case till it engages the lands. This you can influence, by varying the seating depth of your bullet, but the freebore of the chamber (as well as your magazine lenght) will also play a part in determining this.

It seems to be "distance to lands" you are asking about. There is no hard and fast rule for what distance to lands will provide good results. You'll find some of the most accurate (BR) loads in the World to be loaded with the bullet into the lands. There is evidence this is beneficial for accuracy in general. HOWEVER, seating into the lands can cause pressure spikes (so you have to be careful when developing the loads), and what is worse, this seating arrangement is impractical if you ever need to remove a loaded round from your chamber (without firing it). Bullet ogives vary, and even if you think your seating depth will only allow the bullets to JUST touch the lands, the next bullet may be seated .005" into the lands. You risk that by extracting such a cartridge, that the bullet will stay stuck in your barrel, and you will have powder all over your action... Not a great situation, least of all if you are out hunting....

If you want to seat OFF the lands, it is mostly a trial and error thing to depend what works with a particular bullet in a particular rifle. Monometal bullets (e.g. Barnes TSX) often like to be seated further off the lands than bullets with a lead core - Barnes recommends to start the TSX .050" off the lands. That is fairly far (though not impossible) for a more conventional bullet.

So with what distance to lands does it make sense to start with when reloading?? I believe you should make sure you are OFF the lands with all bullets. It is not beneficial in terms of pressure to sometimes be on and sometimes off the lands. Bullets vary over the ogive. Even small caliber (commercial) match bullets routinely vary .002-.003" over the ogive. So to be sure, you should probably be off the lands at least .005" with such bullets. Big game hunting bullets will vary even more than that, so to be sure you are always off the lands, it probably makes sense to start with a distance to lands of about .010 - .020". After that it becomes a trial and error thing, whether more or less distance to lands is beneficial in your rifle with your load.

- mike

YEA, thats what I meant. A "listen to what I mean not what I say" moment. hehe

Very nice answer and thank you very much.

If it is a hunting rifle start off with seating depth that is the same as the diameter of the bullet. Eg. 0.308"(7.62mm) seating depth for all .30 calibers. It will fit the magazine and you do not need a crimp because the case will grip the bullet over a bigger surface. All rifles differ, so play around with it.

My .308 hunting rifle shoot sub MOA with a 5mm jump and speed is good with lighter loads.

KS, .200 is one hell of a jump to the lands.

b beyer, you are absolutely right.
It is a Musgrave'83 and is very accurate like that. To get the bullet touching the lands there is only 2mm for the case to grip.
Is there any bad things that can happen if the bullet jumps 5mm to the lands?

At what point do we drop the term throating and go to free bore? Perhaps a dumb question, maybe not. You hear "---deep throated 6.5x55 or 7mmx57". roger

quote:

Originally posted by KS:
b beyer, you are absolutely right.
It is a Musgrave'83 and is very accurate like that. To get the bullet touching the lands there is only 2mm for the case to grip.
Is there any bad things that can happen if the bullet jumps 5mm to the lands?

Possibly, you will have gas going down the barrel before the bullet most likely which is bound to momentarilly slow up ignition. Who knows? maybe that's a good thing? roger

IIRC, Ken Waters stated in Pet Loads Volume 2 that Norma specified a freebore of something like 11 MM when they loaned out their 308 Norma Mag reamers. That to me is an incredible amount of "jump" for a bullet to make, but somehow or another Norma makes it work...

Back to the origional thread and the .405 win. Are you going to shoot jacketed bullets or cast? If cast bullets are the fare, they will shoot better seated in an oacl that places the bullet very close if not touching the lands. Forget about that 11mm crap when dealing with the .405 win. The oacl will be designated by the magazine length more than the length of the throat. If shooting jacketed bullets crimp in the cannelure and find what the rifle likes, as in the old days by varying powders and bullets .......... have fun, the .405 is a good one

Don't forget that Roy Weatherby built his empire of hot rifles using a looooong throat or a long free bore. I have read somewhere that you weren't supposed to fire Weatherby Magnum ammo in a "standard" throated rifle. (whatever standard is)

Its a 405 but somewhat modified. Its been reamed out to take 3 1/4" brass. I pretty much got this figured out now. I held one of the bullets against the rifling and using a rod, measured distance to end of barrel. Then I took same type of measurement using a cartridge with same bullet with a known acceptable C.O.L..

Comparing the two gave me the C.O.L. of a cartridge using that particular bullet that just engaged the lands. I then subtracted .15 and set that as a start for all other cartidges using that particular bullet. So my distance to lands is .15

I'll repeat with other bullets and fine tune from there.

I just finished a cartridge using a 400gn Hawk with a C.O.L. of 4.170 with an estimated velocity of about 2400 fps. I shot 5 of them yesterday and they look like a winner with 81gns of H4350