ridgeway
Silver $$ Contributor
I agree 100%. The terminology used here is debatable.Don’t be lost! Changing “your” case length has nothing to do with it.
Bart
I agree 100%. The terminology used here is debatable.Don’t be lost! Changing “your” case length has nothing to do with it.
Bart
View attachment 1169148
Maybe a picture is worth 1000 words. In this drawing, the FB is .115. The chamber length is 1.925. If .025 is added to the chamber, will that not increase the EFFECTIVE FB to .140? Just saying.
James...where are you getting .025"? I think the area you are speaking about is a chamfer, not part of freebore.View attachment 1169148
Maybe a picture is worth 1000 words. In this drawing, the FB is .115. The chamber length is 1.925. If .025 is added to the chamber, will that not increase the EFFECTIVE FB to .140? Just saying.
Please explain in further detail. To me freebore is freebore. It's cut...no changing it. If you trim your case and call it the "real freebore" and saying it effects the freebore cut, that's beyond me. I'm just not understanding the point here.
Let's say I have a 1.560 chamber length with a freebore of .150. I trim my case to 1.550. Now from how I understand this, it altered my effective freebore by .010?
Yes, it sure is a number and reading what you wrote I don't think you really follow the relationship between the chamber length and freebore and how it affects the freebore. Trimming brass does not in no way shape or form change freebore. Two reamers with identical freebore and different chamber lengths will affect the loaded case OAL where it touches, but freebore is identical.chuck chuck chuck,
let new ASK YOU A SIMPLE question:
do you shoot a print, a reamer or a chambered rifle with brass and a bullet ?
"free bore" on a print is a number, period
"real chamber freebore" is a combination of:
the "design/print" free bore
actual case length
the amount of length growth for the case neck in the reamer.
SO YES there can be a large difference in "print" free bore, and ACTUAL mechanical free bore in the real chamber.
typical neck growth in a reamer is .020...that affects real free bore.
where you trim your brass also affects the real free bore.
as I mentioned earlier, I spec my reamers to only 0.007, and I trim back from that maybe 5-6.
where the bullet engages the THROAT does not change.
IF IS A HYPOTHETICAL …..James...where are you getting .025"? I think the area you are speaking about is a chamfer, not part of freebore.
Hypothetically, if one has a chamber that is 1.570inches in total length and has a cartridge that is 1.550 and his reamer freebore is a nominal .025"; does that mean that he really has .045 " of actual FB ?
Yes, it sure is a number and reading what you wrote I don't think you really follow the relationship between the chamber length and freebore and how it affects the freebore. Trimming brass does not in no way shape or form change freebore. Two reamers with identical freebore and different chamber lengths will affect the loaded case OAL where it touches, but freebore is identical.
Now back up to answer the first question, I adjust my freebore to a seated dummy round with the bullet I plan to shoot. I throat in a separate operation and make it what I want. I care less about the number.
Like I said before...freebore is misunderstood by many. This thread was way much more complicated than what it is, lol.
Exactly. And that increased amount to the lands is what I am calling "effective" freebore since the bullet has that much more to go before being in the lands. I think everyone here understands what I am saying but let the semantics of the word FREEBORE give them an excuse to argue. If the bullet must be seated out farther before engaging the lands then the effect is an additional freebore. The pissing contest on my part is over.No. But if you get a new reamer with a chamber length of 1.590, your bullet/neck relationship will effectively be out another .020". But none the less the reamer will still have a freebore of .025".
Tom
snip
In the drawing you've included it's a far more generous .0075"
25 cal bullets are .257 in diameter. The freebore diameter shown in the 25 Creedmoor drawing above is in fact only .0005 over bullet diameter.