hey guys a little guidance would be great. I'm trying to determine how to accurately determine appropriate freebore for any specific load I want to run so I order the Reamers correctly the first time. Would I be correct in thinking that I could load a dummy round, measure to the ogive with a comparator add the desired jump and go from there?
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Gunsmithing Determining freebore
- Thread starter hunter223
- Start date
https://youtu.be/TWmIwPwLyyg
I found the method above to work the best for me and be most consistent.
I found the method above to work the best for me and be most consistent.
If the comparator has an inside diameter the same size as the diameter of the rifling at the exact point that you want the bullet to engage them, them yes. It must have a sharp edge also. Any radius will change the measurement. The easiest way to get it done righ is to load up an couple dummy rounds and send it to your reamer company of choice. Tell them where you want the rifling in relation to the bullet, jump or jam distance, and they will get you what you need.
Yessir I understand that was just trying to avoid the time for that set up was all. I've only used Manson and really like em but are any of the other reamer manufacturers fairly quick on turn around?
What bullet are you wanting to shoot? I found dimensions on the Berger 195 I'm shooting in my 28 nosler I'm building. I used that along with case dimensions to figure out how much freebore I wanted. It is just a bunch of simple math, enough to make it seem kinda complicated to me.
Jgs is 6-8 weeks I believe. That's who I mostly use. That is another option. Tell us what you are going to shoot and what your parameters are and odds are someone might have done the same thing already and and answer your question without even measuring
I order custom reamers from Manson. I've seated a bullet to the depth I want in a case with no primer and sent it to them. I've also talked with Dave and told him what I was doing (on a wildcat) and he was able to calculate the freebore (from the ogive) with a computer since he's got the specs of nearly every bullet currently made. Both methods of getting the reamer ordered has been spot on for me in terms of freebore.
Call Dave Kiff at PT&G and he will compute it for you. There are radius at ogive meeting 1.5 degree nose. Simple math will not be accurate.
The closest thing I could find was to seat a bullet touching a friends gun in same chambering and subtract the known freebore. With same bullet, measure the difference in OAL to add back in to chamber length. With something as popular as a 300WM, it should be relatively easy to find someone that has one.
Manson has been really great at sending prints since I started using them(after switching from PT&g). If you call and ask, they'll have a print of whatever you want in your email almost before you get off the phone. Ask them for a blank too, so you can fill it in and sent it back to them. I usually start with a print or prints for a given cartridge, to compare with the dummy I make. Where the actual bullet touches the leade is difficult to calculate, but fortunately, it usually isnt a big variance.
As was mentioned above, there's a huge knowledge base already there, chances are they can recommend something from memory. Use a good comparator too.
As was mentioned above, there's a huge knowledge base already there, chances are they can recommend something from memory. Use a good comparator too.
The PTG 300WM Tac Match reamer has 0.097 free bore. The 230 Hybrids touch at 3.620" in the half dozen chambers I've reamed with it.
