Bore Ridig Diameter.

[braddock]

Image above is of two cast boolits, one cast for 30/30 and sized 0.309" and the other cast 0.312" and then sized 0.309".
This isn't my issue.
The bore riding diameter on the Flatnose 30/30 boolit is 0.300 + a small amount. The other boolit is 0.302" on the bore rider section.Both are intended for use in 300/308 diameter bores.
Is 0.302" too big of a diameter to safely use in a 308 Win? A dummy round is cut by rifling over the bore riding section when run through the action of my 308, the boolits are hardcast with a brinel number in the high 20s.

[475AR]

It will depend on your specific barrel and rifling. If you go to McGowan barrels and look at their barrel tech info, they list for their 30 cal barrels have a .300" bore (top of the lands) and a .308" groove. So both listed bore rider dimensions you listed would not fit into the bore. To correctly fit you would need to be somewhere in the .299"-.2995" for the bore ridding section of the bullet. Also the mold maker's tolerance will impact this dimension.
Since your bore ride is a tad to large you could get an NOE nose size die and get the correct diameter after getting a chamber cast and measuring the actual bore of your barrels. (Or you could order a couple of the NOE nose bushings in say .298"-.299". Also you should take note that cast bullet shrinkage will also impact your final bore ride diameter for a given alloy.
If you are not looking to do all the extra work to get the exact bore ride diameter I would suggest getting one of the NOE nose bushing dies in .2985" and call it a day. Even with a little slop in the bore ride dimensions the bullets will still be accurate.

[Bigslug]

The bigger question is if they chamber and extract easily. If they do, then your bore ride section is far enough back from the throat that it's not jamming into the lands until after you pull the trigger. If your ammo makes opening or closing the action harder than it is with an empty chamber, then "safety" is compromised mainly by the fact you don't have a reliably functioning firearm.

Going a little softer on your alloy mix may drop your nose diameter down that extra 0.001"-0.002". I am assuming you're using some kind of water-quenched wheelweight or linotype base if your BHN's are over 25. If this is the case, you have hardness to spare and can experiment with dropping in a bit of pure lead without compromising performance. Alternatively, most of our modern molds are spec'd for either wheelweight or Lyman #2. You might try those and see where you land.

Correctly filling the available cartridge neck and chamber throat space is one of the challenges of designing molds for bottlenecked cartridges. We tend to start with the gas check at the base of the neck, locate our lube grooves, and fill forward from there. Unless you're locked in by a need for a crimp groove, there's something to be said for a design that allows you to creep the base of the bullet forward about 0.1" in the neck before you expose lube, impact the lands on chambering, or run out of space in your magazine. This allows you to set the front of your bore ride section and front driving band a bit back from where you think they need to be, and seat longer to achieve your ideal chambered-round resting point.

The .308 you're shooting has a comparatively short neck which makes the above a little harder to achieve. You might consider looking at the following from NOE: TL309-177-RF, TL310-178-RF, and TL311-178-RF. These are the same Ranch Dog design with minor diameter tweaks. Ranch Dog shaped it specifically for the SAAMI .308 neck and throat, which is a comparatively rare thing in Cast Bullet World. I believe it's the .310 shank/.300 nose version I'm running as a practice bullet in my Ruger Gunsite Scout, and loading it was a no-brainer: 1. Seat to conceal all the grooves; 2. Fire for effect. With its flat nose, it is obviously not intended as a long range target bullet, but it is accurate to common hunting distances, can be driven hard, and hits with authority, turning water jugs into baby fog banks.

[Maven]

I agree with Bigslug completely: Well-written and spot on!

[Delkal]

Just stick the bullets into the muzzle and see how they fit. Bore riders should go in with a light thumb pressure. If it takes too much effort the nose is too big and if the bullet drops right in it is too small.

[Bigslug]

braddock, some more brain-twitches. . .

Your round nose bullet looks to be a 210 grain Lyman 311284, which I understand was originally conceived as a bullet for the U.S. .30-40 Krag - a round defined by a long case neck and a throat designed for a 220 grain round nosed FMJ. It's a LONG bullet for either a .308 neck or a .308 throat. As 475AR suggested, there are work-arounds, but it probably isn't optimal.

The .30-30 has a similarly long neck traditionally without the long bullet nose. Looking at the bullet you pictured, you can probably set your lube sizer depth to not fill the forward crimp groove, keep both lube grooves in the .308W's .300" long neck, and be functional.

[Delkal]

Very few bullets are true bore rider designs. Most bullets have a taper that get larger than the bore before you hit the top lube band. For these bullets the rifling engages somewhere along the ogive and is the max OAL to be seated. With a true bore rider the bullet fully engages the rifling at the top band.

You can usually tell bore rider designs by measuring the diameter along the ogive. If there is 1/4+ inch section where the diameter is the same it could be a bore rider as long as that section is slightly snug in your barrel. If you measure and the diameter starts out oversized and progressively gets smaller towards the tip (even moving 1/16 inch) it is a standard design.

[405grain]

Make a dummy round (no primer or powder) and see if it chambers. If you check to see if the bullets are going to work before hand it will save you from loading up a whole batch and then discovering that they won't fit.

[charlie b]

Like stated above, just have to check the fit in the chamber/throat/start of rifling. This is not the same as at the muzzle.

Another data point is my Savage .308 likes the bore riders to be .302 for a slight interference fit. You can feel the bullet engage the rifling and it takes a tap on the bolt handle if you want to extract the loaded cartridge. I size the noses to that dia. The seating depth is set so the first drive band engages the throat as well. FWIW, a .302 nose will not come close to fitting in the muzzle of the rifle.

Do a pound cast of your chamber mouth/throat area and measure the pertinent sections. Then figure which bullet to use.

Keep in mind that a combination of nose and body size dies from NOE will solve a lot of problems.

[braddock]

Many thanks for the responses, I'll revert when I've had an opportunity to load some and test them this coming weekend.

[Finster101]

Would love to get a couple of nose sizing dies. The only problem I have ever had with NOE is finding items in stock.

[Delkal]

Another data point is my Savage .308 likes the bore riders to be .302 for a slight interference fit. You can feel the bullet engage the rifling and it takes a tap on the bolt handle if you want to extract the loaded cartridge. I size the noses to that dia. The seating depth is set so the first drive band engages the throat as well. FWIW, a .302 nose will not come close to fitting in the muzzle of the rifle.

I don't totally understand this. Unless your barrel is getting shot out the lands diameter should be the same from where the rifling becomes full sized (after the throat) and be the same at the muzzle. I also have some loads where I jam the bullet into the lands but these are actually jammed into the taper after the throat.

What bullets are you using and are they supposed to be a bore rider design? AFAIK a bore rider is supposed to barely touch the top of the rifling so if the whole bullet nose/ ogive doesn't fit in the muzzle I would not call it a bore rider. The barrel should only be engaging the rear bands of the bullet.

[Dusty Bannister]

This from the archives might help you understand the bullet design.

https://castboolits.gunloads.com/sho...+bullet+design

[charlie b]

I don't totally understand this. Unless your barrel is getting shot out the lands diameter should be the same from where the rifling becomes full sized (after the throat) and be the same at the muzzle. I also have some loads where I jam the bullet into the lands but these are actually jammed into the taper after the throat.

What bullets are you using and are they supposed to be a bore rider design? AFAIK a bore rider is supposed to barely touch the top of the rifling so if the whole bullet nose/ ogive doesn't fit in the muzzle I would not call it a bore rider. The barrel should only be engaging the rear bands of the bullet.

The tighter fit in the bore helps accuracy for me. And, yes, the .30cal 210gn I use is an Eagan design (Acc 31-210E) with most of the bullet of bore dia. It is a bore rider because it does not fill the grooves.

If it doesn't touch the lands evenly all the way around then it is not a bore rider, it is just an undersize nose. To make sure it is evenly centered I like the bullets to be a friction fit. Then I am sure it is not too small, which is really bad for accuracy.

And, yes, I am happy when the muzzle is very slightly smaller than the chamber end. The throat area does erode over time as well.

[Delkal]

This from the archives might help you understand the bullet design.

https://castboolits.gunloads.com/sho...+bullet+design

Maybe it is just a matter of semantics but to me there is a big difference between a bore rider bullet and how a standard bullet travels down a bore. I only know of a handful of true bore rider designs and most bullets are tapered to where they are oversized before you get to the lube bands,

I have recently been playing with the Lyman 311291 which is a true bore rider design. Luckily I have a mold where the nose is 0.300 and is the correct diameter for a .308 bore. I can push the nose of the bullet in the muzzle with a slight pressure and it goes in till the firm stop at the start of the bands. This is the correct bore rider dimensions. I have heard a lot of people complain when it is smaller and it gives reduced accuracy. I assume you can also push a larger 301 nose in the muzzle but I think it would be rare for a properly made bore rider to have a .302+ nose.

Everything else in your referenced post concerning sizing to fit the throat / freebore is correct. I understand the differing diameters of the throat / freebore and sizing to fit but that is only applicable to the bands of a bore rider bullet. With a bore rider the sizing is only done on the bullet's bands. The nose should fit the top of the lands perfectly and should remain untouched.

[35 Rem]

Image above is of two cast boolits, one cast for 30/30 and sized 0.309" and the other cast 0.312" and then sized 0.309".
This isn't my issue.
The bore riding diameter on the Flatnose 30/30 boolit is 0.300 + a small amount. The other boolit is 0.302" on the bore rider section.Both are intended for use in 300/308 diameter bores.
Is 0.302" too big of a diameter to safely use in a 308 Win? A dummy round is cut by rifling over the bore riding section when run through the action of my 308, the boolits are hardcast with a brinel number in the high 20s.

If a dummy round can be chambered and extracted, then all this theorizing seems useless to me. Your rifle can handle a .302 diameter bore rider. Unless it fits so tight that you think the bullet might be pulled out of a loaded round every now and then?? I shoot a bore rider from Accurate in my Winchester 94 chambered for 32 Special and it leaves light rifling marks on the nose but easily extracts a loaded round. Seems like a perfect application of the bore rider design to me.

[john.k]

To reduce a 302 bullet to 300 is only 001 per side ....this nothing with any lead alloy ,and sets the bullet up to enter the rifling exactly straight on,instead of skidding along one side of a throat and entering slightly crooked...........Ive found cast bullets exceptionally difficult to pull from a sized case neck ,more so than jacketed.

[charlie b]

Maybe it is just a matter of semantics but to me there is a big difference between a bore rider bullet and how a standard bullet travels down a bore. I only know of a handful of true bore rider designs and most bullets are tapered to where they are oversized before you get to the lube bands,

I have recently been playing with the Lyman 311291 which is a true bore rider design. Luckily I have a mold where the nose is 0.300 and is the correct diameter for a .308 bore. I can push the nose of the bullet in the muzzle with a slight pressure and it goes in till the firm stop at the start of the bands. This is the correct bore rider dimensions. I have heard a lot of people complain when it is smaller and it gives reduced accuracy. I assume you can also push a larger 301 nose in the muzzle but I think it would be rare for a properly made bore rider to have a .302+ nose.

Everything else in your referenced post concerning sizing to fit the throat / freebore is correct. I understand the differing diameters of the throat / freebore and sizing to fit but that is only applicable to the bands of a bore rider bullet. With a bore rider the sizing is only done on the bullet's bands. The nose should fit the top of the lands perfectly and should remain untouched.

I think you mean a 311299. The 311291 is more of a conventional design. There are a lot of bore rider designs out there if you look closely. FWIW, the 311299 is a friction fit in my bore. It won't go in the muzzle without tapping on it. Once chambered it will stick in the bore. But, it shoots really well. I would nose size those as well if I shot them more to be a better fit. The RCBS 165SIL is another that fits mine well. They also make a couple others in .30cal.

And, yes, if the bullet comes out of the mold the proper dia you don't size the nose. Unfortunately some of them do not, so using a nose sizer can be necessary. When I ordered my Accurate mold I specified the nose dia such that I would need a nose sizer to make it a perfect fit.

I agree that the perfect situation is when the bullet just touches the lands, first driving band just touches the rifling and the bullet is a perfect fit to the grooves. But, it takes something to be off just a tad and not touch, ruining the accuracy of the bullet. So, I oversize the nose just a bit and I jam the driving band into the rifling and the driving bands are sized .001 to .002 over the groove dia. Must be doing something right or I could not shoot these.

This was the Accurate 31-210E at 500yd.


or this one.
https://www.youtube.com/watch?v=F0uNMmw85cw