Gunsmithing Freebore question

[Lrush]

How do you determine how much freebore,if any,will work well in a particular caliber?

 

[jake6547]

It depends on what your starting with, A scratch build? It seems like most of the time freebore is restricted by the mag length. If you have plenty of mag length then you should take the cartridge and projectile you want to use. Press the bullet in till the projectile is
about to the bottom of the case neck. Then measure the freebore. The term freebore is measured from the face of the case to the (not sure proper terminology) full diameter of the bullet just starts to taper down That dimension should be you free bore>make since?

 

[Lrush]

I think you are talking about the ogive,I know what freebore is, what I am asking is if you were going to build a custom rifle and ordered a reamer would you order a saami spec or a custom reamer and how to determine what freebore works well in certain calibers. I hear of some rifles having 0 freebore and some having say .100

 

[Goatman007]

I try not to. LOL

 

[BusterB]

Quick and dirty answer, if you pick a specific bullet weight class you use free bore to tweak the chamber to the amount of jump that works best for that combination. You can also use free bore to make oal longer or shorter depending on needing to fit into a specific length action or if you want to push the bullet out to make more room for powder.

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[BusterB]

Ps. If I was building a custom rifle I would have the reamer custom made for the bullet and brass combination I planned on using

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[krw]

I have had 2-260's built with a custom PTG reamer made to my specs. I specified a .298" neck to allow Lapua brass with .003" clearance. I also loaded up 3 dummy rds with 123gr SMK's loaded to 2.800" oal and specified I wanted .010" jump. This equates to a .047" freebore. I never intend to shoot heavier than 123's was my reasoning behind this. If doing this over I would have asked for another .010-.015" freebore. I think this is the reason both these rifles are a little on the finicky side. But the heavier rifle is a sub 1/2moa rifle and the Ltwt hunting rifle will shoot in the .6's so they both shoot!

 

[gewehr]

Depends upon the bullet you want to shoot, if I was having a reamer cut for a berger hybrid for example,
Mag length - brass length - bullet tip to ogive - neck shoulder junction to brass length and add .015 after I come up with the number based on those inputs and your good to go


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[jake6547]

I would order a custom for sure, only way to ensure everything is going to work together with the projectile combo you want to run.

 

[Straight Shooter]

As a smith I try to encourage Saami spec. You never know when someone is going to shoot factory ammo. Shooting factory ammo without the specified free bore can disassemble a rifle is spectacular fashion. Shorter than Saami then don't expect to be able to utilize some of the max loads in the book. The reloading manuals are printed based on Saami spec chambers. Lots of guys blowing primers trying to get their 260 to get run the 140 grain bullet up to book speeds, if that chamber is a custom, they may have to live with the fact they may never get there. There is nothing wrong with a nice snug throat without rifling for a little bit. If your chamber is truly in line with the actual path of the bore the rifle gets a lot less sensitive to seating depth. Also consider that trick no turn neck may become unsafe with a different batch of brass.

 

[Lrush]

One reason I was asking, I just built a 260 with .070 freebore to shoot Berger 140 gr.,I have a rock creek barrel 1:8 twist and I'm having trouble developing a load with good groups