I have a Mauser 03 in 300 Weatherby. I measured the lands at 3.990". Weatherby lists the freebore for the 300 on their website at .361".

I'm trying to figure out what length I should load to. Should I subtract .361" from 3.990" for a COL of 3.629"? The max length my magazine will hold is 3.685".

Or should start at 3.629" and back down?

Or, should I start around the 3.56" spec max COL?

From my experience the 300 Weatherby liked a fair amount of bullet jump. I loaded a 210gr nosler at 3.58. I didn't have any issues the mag box
Dave

all of the rifles that i have worked up loads for that had alot of free bore like the weatherbys and some others shot much better with flat base bullets. i would choose a seating depth that gives sufficient neck tension and go from there.if the cartridges fit the magazine i believe you will still be off the lands plenty far enough.

i would use a fed 215 primer and try different weights of appropriate powders for the most accurate load in that rifle.

I have never been able to make contact with the lands given a COL that fits the magazine box, and given adequate case neck purchase.

My best accuracy with the .300 Roys has obtained from seating to the max length allowed by the mag box, and by avoiding boat tail projos. Someone here clued me into the BT issue awhile back and it is a valid observation.

interesting observation on the boat tails.

I'm using some Scirocco 180 gr bullets to break in the barrel. For bullets, I'm going to test 200 gr Aframe, Woodleigh, and Partition. And 180 gr TSX.

I think Sciroccos and Accubonds are bit light construction for a 300 WB.

I would start as long as the magazine allows and still lets the rifle feed flawlessly. Making the LOA a few hundredths shorter will make no detectable difference in velocity/pressure and is unlikely to make a difference in accuracy, although you're certainly free to try. The less room you leave in the magazine for the bullets to bounce fore and aft then the less potential damage you will have to bullet tips from recoil.

Phil, Sam and Stonecreek have it right above.

In my 300 Weatherby Mag, granted I was shooting Weatherby factory loads at the time. it seemed that the flat base bullets were more accurate. I have observed in that in other 300s since too.

I am not much on crimping in many calibers, but the 300 Weatherby is one I would at least try a mild or medium crimp on. Especially if I wasn't satisfied with the results I was getting.

quote:

Originally posted by TexKD:

I am not much on crimping in many calibers, but the 300 Weatherby is one I would at least try a mild or medium crimp on. Especially if I wasn't satisfied with the results I was getting.

What is it about a .300 Weatherby that you believe would make a crimp helpful? What about a .300 Win, a 7mm STW, or a .264 Win?

You might be able to seat a .300 Win, .264 Win or 7mm STW to or near the lands and get consistent shot start pressure that way.

A .300 Weatherby with its long free-bore is more reliant on neck tension and perhaps a crimp for the initial pressure build up during ignition. At least that's the theory
put out by some.

My 300 wby a Japanese Mk v likes bullets loaded close to magazine length. However I find that as I increase OAL I get to a point where the second and third bullet in the magazine will push the tip of the first bullet high and jam it in the action. Make sure you feed your hand loads through your action each time you load new rounds.

I have had good results at magazine length as well. I have also had trouble with some boat tails, but have been able to get useable accuracy with some tinkering. I have had very good luck with Barnes TSX/TTSX boat tails at Mag length especially the 165/168 grains. I cannot get Berger VLDs to fly right from mine with ALOT of effort, including seating well past mag length. The only flat base I shoot from the Roy is the 150 Partition. it is sub MOA, but can't come close to the TSXs.

The TSXs frequently work in the Weatherby cartridges, often in barrels that don't really like anything else. The combination of a bullet that likes a jump and a chamber that guarantees that its going to get one works well together, at least as far as squeezing little groups goes.

what lengths are you seating your TSX's at? Mag length?

Barnes recommends 3.57", but I'm game for anything that will:

1) Fit in the mag
2) allow me to crimp into one of the pressure relief bands

I think the 200 gr Aframes, but you have to seat short to crimp into the cannelure.

Typically I seated them (168s)to the second groove which put the base of the boat-tail near the beginning of the neck and left the door open to crimping, although I don't remember crimping any. If memory serves that was about 3.700 in a box with a length of 3.800+. I still have the rifle but it is a .300 Win now.

If you want a crimp in your magazine you'll have to seat to the first groove. That will use up most of your magazine with a bit of rattle room for function.

Having many Weatherby chamberings with the standard freebore, 3/8"-1/2", I would not bother with crimping, just load to .010" under max mag length and shoot for groups, then load up whatever charge weight is the most accurate.

Dogleg,
Would really like to know where this theory about crimping and freebore effects start pressure.
I can tell you with 100% certainty that the factories crimp to boost/delay bullet movement so that they get higher start pressure and therefore higher velocities with less powder, it also reduces ES and is why factory ammo is accurate in many rifles. It has nothing to do with freebore, the leade and throat are .003" (tapered throat) to .0005" over bullet diameter and is enough of an area to seal the chamber fir good start pressures. I know this to be true because I own a pressure trace and have tested many rifles with freebore, including modern chamberings that come with far more freebore from the manufacturers than the SAAMI specs for that cartridge. Crimping helps when using a low load density charge also, it improves the curve under PMAX due to start pressure increases.

Cheers.

Didn't we just say more less the same thing?a crimp raises shot start pressure. Do you not think that jamming the bullet against the lands does the same thing? That isn't an option on a Weatherby cartridge.

Yes, jamming a bullet raises start pressure, but it doesn't mean that raising the start pressure by CRIMPING is the SAME or has the SAME EFFECTS.
Crimping may in fact reduce accuracy, whether there's freebore or not, not all brass is even thickness around the neck, some thicker spots may cause the bullet to tip as it's released by the neck.
Jamming bullets may work in tight necked BR rifles, but I have never seen an improvement to accuracy from a tuned load in a hunting rifle.
I leave the BR techniques to the BR crowd, even my F-Class rifles don't get the bullets jammed, they like jump.
The reason for the freebore in the first place is to lower pressure giving the bullet a softer transition into the rifling and due to the extra powder you can use, velocity doesn't lose out.

Crimping is not necessary unless you want to scrimp on powder and need to boost start pressure, most ballisticians understand this, hence why the factories do it to save money on powder.

Cheers.

You don't have to sell me on not crimping, I don't crimp anything but revolvers and straight rifle cases.

You've never seen an accuracy improvement from seating to the lands?