Reamer freebore and reloading

[UndFrm]

Apparently, I missed reading about the reamer and the affect on deciding the suitable bullet.
I did read about the brand of the brass that will be specific to the reamer (unless neck turned) but I didn't read about the freebore of the reamer that'll also decide what will be the most suitable bullet (brand, weight etc).

Considering the reamer is a 6mm Dasher with a .120 freebore, how does it affect and how do I decide what the ideal bullet would be? The barrel is a 7.5 twist. I was under the impression that whatever the freebore is for the reamer, it can be neglected as the seating depth of the bullet can be adjusted (to an extent) and then be tested with jam or certain jump. Is that not correct?

Given the freebore and the twist, what should be my bullet of choice for starting the testing? I do have some load data but then again, I don't remember seeing anything that mentioned the freebore, just the twist for picking the bullet. Talking to guys at the range, they recommended 105gr Berger or 115gr but only 1 of them asked me about the freebore which got me thinking.

Thank you

 

[Threadcutter308]

Apparently, I missed reading about the reamer and the affect on deciding the suitable bullet.
I did read about the brand of the brass that will be specific to the reamer (unless neck turned) but I didn't read about the freebore of the reamer that'll also decide what will be the most suitable bullet (brand, weight etc).

Considering the reamer is a 6mm Dasher with a .120 freebore, how does it affect and how do I decide what the ideal bullet would be? The barrel is a 7.5 twist. I was under the impression that whatever the freebore is for the reamer, it can be neglected as the seating depth of the bullet can be adjusted (to an extent) and then be tested with jam or certain jump. Is that not correct?

Given the freebore and the twist, what should be my bullet of choice for starting the testing? I do have some load data but then again, I don't remember seeing anything that mentioned the freebore, just the twist for picking the bullet. Talking to guys at the range, they recommended 105gr Berger or 115gr but only 1 of them asked me about the freebore which got me thinking.

Thank you

You should also look into bullet availability as part of your decision. I shoot Berger 105's, but I bought a bunch when they were available (in the Trump years). If you can find them, they're a great bullet. But, if you can't find any to buy, it doesn't matter how good they are.

 

[918v]

Apparently, I missed reading about the reamer and the affect on deciding the suitable bullet.
I did read about the brand of the brass that will be specific to the reamer (unless neck turned) but I didn't read about the freebore of the reamer that'll also decide what will be the most suitable bullet (brand, weight etc).

Considering the reamer is a 6mm Dasher with a .120 freebore, how does it affect and how do I decide what the ideal bullet would be? The barrel is a 7.5 twist. I was under the impression that whatever the freebore is for the reamer, it can be neglected as the seating depth of the bullet can be adjusted (to an extent) and then be tested with jam or certain jump. Is that not correct?

Given the freebore and the twist, what should be my bullet of choice for starting the testing? I do have some load data but then again, I don't remember seeing anything that mentioned the freebore, just the twist for picking the bullet. Talking to guys at the range, they recommended 105gr Berger or 115gr but only 1 of them asked me about the freebore which got me thinking.

Thank you

Your concern is valid and you should talk to the rifle builder about this because you’re dealing with a specialty cartridge.

 

[Doom]

I'm no Dasher expert but based on some info from some "experts" that freebore works well with bullets of 105 gr and higher. It's a little long for lighter bullets.

 

[UndFrm]

Thank you for the responses.
I'm still unable to understand the affect of Free bore (for example: .120 vs .240). Isn't it the same as adjusting the jump for a bullet?

 

[918v]

Freebore allows you to seat the bullet out further. It allows you more flexibility in adjusting bullet jump. It’s a dimension that is part of several variables involved in chamber design.

Generally heavy for caliber bullets need more freebore else they will need to be seated deep in the case and take up room that can be filled with powder.

Also consider that bullet jump reduces pressure because the bullet can get moving before it gets engraved by the rifling.

 

[spife7980]

Any freebore from .104-.150 should be fine with the 105-115 bullets, especially with the 7.5 twist. Pretty standard dasher chamber for long range shooting it looks like. You would do fine with it.

 

[bax]

Regardless of bullet, my max COL is what will fit into my magazine and reliably function. If you single-load, you are not constrained by that limitation.

A very short bullet might be just barely seated in the neck, but that won't work. When you chamber the round, the bullet is knocked all skeejay and doesn't line up with the center of the bore. You want the maximum amount of bullet shank in the case neck with only the boattail protruding into the case body. That maximizes case powder capacity and while providing the most metal-to-metal contact between the case neck and the bullet - hopefully that improves bullet alignment with the bore. That is the ideal, you can try variations some will work better. Seat further out, more powder capacity, less grip by the neck, may not fit in the magazine. Seat further in, less powder capacity and more jump.

Different guns (that is stock, action, barrel combinations) like different jump. For some given freebore let's start with minimum jump, with a short bullet with low ballistic coefficient that is just touching the rifling. How deep is the bullet seated? Will it fit in the magazine? Suppose a max COL cartridge - bullet seated as far out as you dare and still fits the magazine - and zero jump. That may shoot or it may not. If you increase the freebore without changing the cartridge COL, the gun may shoot better, or not. Now return to that specified freebore and seat the bullet deeper into the case. The gun may shoot better. Or not. Let's change from a short fat bullet to a long skinny bullet. For a given seating depth (bottom of the bullet shank is at the bottom of the case neck), COL will be longer and now jump will be longer. In order to get the same jump, the COL will be longer, bullet will be seated higher in the case neck, and it may (or may not) fit in the magazine.

So - you have several variables that interact. Bullet shape and weight. Seating depth. Freebore. Maximum COL to fit in the magazine. Of those four, freebore is the hardest to change because you need a reamer AND it can only get longer - once you cut it deeper, you can't put the steel back.

Some calibers will shoot certain cartridges well. For example, most 308 rifles fed with ammo loaded to Federal Gold Medal Match ballistics shoot well. Other weapons and calibers fed different combinations of bullet, powder, primer, case, seating depth, and reamer dimensions are more fussy. I like long heavy bullets so I ask for slightly longer freebore. I don't know if I am right or wrong but I tune the ammo to shoot with the chamber it has.