Freebore
- Thread starter Doc68
- Start date
You don't. Not easily, any ways.
Either trust the reamer print, or section the barrel. Or find someone with a similar barrel that is chambered with a known reamer i.e. one that you (or they) *know* had a specific freebore dimension. Get their seating depth to the lands with one specific bullet, preferably touching/jammed, and if at all possible, the OAL, not base to ogive. BTO is too subjective depending on the type of comparator used, lot to lot ogive variances, etc. OAL is also variable, but mainly just due to tip finish on HPBT, and is the lesser of the two evils in this case. Seat a similar bullet to the lands in your chamber, and compare the readings.
It won't be exact, but you should be able to tell if your barrel is in the same ball park or not.
Either trust the reamer print, or section the barrel. Or find someone with a similar barrel that is chambered with a known reamer i.e. one that you (or they) *know* had a specific freebore dimension. Get their seating depth to the lands with one specific bullet, preferably touching/jammed, and if at all possible, the OAL, not base to ogive. BTO is too subjective depending on the type of comparator used, lot to lot ogive variances, etc. OAL is also variable, but mainly just due to tip finish on HPBT, and is the lesser of the two evils in this case. Seat a similar bullet to the lands in your chamber, and compare the readings.
It won't be exact, but you should be able to tell if your barrel is in the same ball park or not.
That is another option... depending on how much you trust Cerrosafe. Probably plenty close for these purposes, though.
I trust it a lot more, after finding the actual manufacturer's information on the dimensional changes, rather than the shite that Brownell's marketing dept. mangled and put on their product page
I trust it a lot more, after finding the actual manufacturer's information on the dimensional changes, rather than the shite that Brownell's marketing dept. mangled and put on their product page
Yeah, I got that. And that's what I described how to ballpark. The video you linked to is finding the seating depth... which is not the same thing. As I'm sure you know
If you got it from NSS, they're usually pretty good about emailing you the reamer print on request.
Yeah, I got that. And that's what I described how to ballpark. The video you linked to is finding the seating depth... which is not the same thing. As I'm sure you know
Whats the reason for needing to know freebore besides finding seating depth?
Some of the load data floating around may or may not be safe in a chamber with radically different freebore.
Just knowing that someone else was jumping 20 thou to the lands isn't always enough. If they have a chamber with 100 thou longer freebore than you do, you'll run into major pressure very early on. Having an idea of what your actual chamber dimensions are is one part of diagnosing those kind of problems.
And every once in a while you see someone end up with the wrong chamber - like a 6BR throated for 55-70 gn varmint bullets instead of 105-110gn match bullets. Gunsmith grabbed the wrong reamer, etc.
Just knowing that someone else was jumping 20 thou to the lands isn't always enough. If they have a chamber with 100 thou longer freebore than you do, you'll run into major pressure very early on. Having an idea of what your actual chamber dimensions are is one part of diagnosing those kind of problems.
And every once in a while you see someone end up with the wrong chamber - like a 6BR throated for 55-70 gn varmint bullets instead of 105-110gn match bullets. Gunsmith grabbed the wrong reamer, etc.
And if you hit pressure way early, compared to what is the norm for a given chamber/freebore relationship? Just shrug and say 'oh darn'? Or maybe do some sleuthing to find out if your gun really has the chamber it was advertised as having - and that you paid for?
Judging by the original post I would say he has no clue so it's kind of irrelevant. A person needs to work up a load based on their personal rifle instead of just grabbing info off the internet and hoping it works. There is a reason that you are supposed to start low and work your way up. If you are really concerned then buy quickload and you can see what bullet seating depth does with your pressure and powder charge.
Has the op even bothered to measure oal for his particular gun? Plenty of info out there especially in our reloading data section with specifics listed as far as bullet, powder and overall length of a person wants to go that route.
If
Has the op even bothered to measure oal for his particular gun? Plenty of info out there especially in our reloading data section with specifics listed as far as bullet, powder and overall length of a person wants to go that route.
If
Yes. I have measured base to ogive with a hornandy modified case and comparator. For my load of hornandy 105gr BTHP its 2.280 from base to ogive to where they touch the lands. I was running 41.7gr of h4350 in my stock barrel that came with the Ruger precision Rifle and had zero issues. I worked up a new load in my criterion barrel and had a few rounds left over from the stock barrel, 7 to be exact and popped primers in 3 of the 7 rds.
As far as the brass, its all hornandy 2x fired. Shoulder bumped back .002.
Bradu, its rude to assume things.....
This is why i was asking. Im not a maniac when it comes to reloading. I like my face and fingers how they are and where they currently are.
As far as the brass, its all hornandy 2x fired. Shoulder bumped back .002.
Bradu, its rude to assume things.....
This is why i was asking. Im not a maniac when it comes to reloading. I like my face and fingers how they are and where they currently are.
The old chamber was 2.265 from base to ogive touching the lands and i had them the bullets jumping 15 thousandths into the lands, so the bullets were seated to 2.250. So thats now 30 thousandths off the lands on the new barrel. This is why im confused as to why i popped those 3 primers.
Weather conditions was about 10 degrees warmer yesterday with the new barrel than when i shot the old barrel. Humidity here in CO is almost non-existent.
Just weird. Thats all.
Weather conditions was about 10 degrees warmer yesterday with the new barrel than when i shot the old barrel. Humidity here in CO is almost non-existent.
Just weird. Thats all.
