Fellas as always i have a little something thats been on my mind lately. I am thinking about buying my own 6ppc and 30BR reamers and having custom size dies made for each chambering instead of using redding and harrels dies for everything. Anyway on the 30BR reamer i am thinking about having my reamer made with a little free bore. My thinking on this is that a little free bore would be a good thing. All my 30Br chambers are zero free bore and they shoot just fine but would a little free bore say .025 help align a bullet that might be a little crooked? With zero free bore the bullet is sitting on angles and there really isnt anything to hold the bullet straight, is there? Maybe i am not thinking about all this in the proper way but if i am a little free bore would be a good thing right? What do you think, would a little free bore help align a bullet and how much would be to much for the bullets we shoot? thanks lee
30BR zero free bore Question????
- Thread starter skeetlee
- Start date
jackie schmidt
New member
Lee, the term "zero freebore" simply means that the reamer grinder attempts to put as little freebore in the grind as possible. I am not sure there is really such a thing in practicle sense, just in theory.
Here is why I say this. A good friend and I both have zero freebore 30 BR Reamers, ground from the same print, by the same grinder. But, to get the exact same marks on the bullet, he has to seat his .020 further in than I do. So, which one is right? Beats me, they both shoot quite well.
Keep in mind, the freebore is not what aligns anything, as it actually has clearance, (not much), over the bullet. The lead is what aligns things. Of course, if you are jumping the bullets, nothing does.
I ver have been able to achieve this "chamber will straighten a round" thing. I have taken crooked rounds, chambered them with a good jam, and it runs out just as much when I remove it. I can take dead straight rounds, do the same thing, and they come out just a straight.
I sometimes think that those that say that a chamber will starighten a round have never actually seen for themselves............jackie
Here is why I say this. A good friend and I both have zero freebore 30 BR Reamers, ground from the same print, by the same grinder. But, to get the exact same marks on the bullet, he has to seat his .020 further in than I do. So, which one is right? Beats me, they both shoot quite well.
Keep in mind, the freebore is not what aligns anything, as it actually has clearance, (not much), over the bullet. The lead is what aligns things. Of course, if you are jumping the bullets, nothing does.
I ver have been able to achieve this "chamber will straighten a round" thing. I have taken crooked rounds, chambered them with a good jam, and it runs out just as much when I remove it. I can take dead straight rounds, do the same thing, and they come out just a straight.
I sometimes think that those that say that a chamber will starighten a round have never actually seen for themselves............jackie
Fergus Bailey
New member
Actually, since freebore is effectively more clearance around the bullet, wouldn’t introducing freebore have less effect on aligning a bullet?
Fergus Bailey
New member
I agree that the Redding dies are fine, but the disadvantages of this approach I can think of would be that:
1) If I had specific dimensions I wanted for the chamber, I would have to forgo these if matching the chamber to a die. Whereas if I make the reamer to my specification, then find a die to fit, I have complete control over the entire final dimensions of the chamber (noting that the reamer grind and chamber reaming may still be variables outside my control).
2) Probably of greater concern to me is that (with Redding at least) the die dimensions will change over time, presumably as progressively more dies are cut and the reamer resharpened. Some years ago, a friend used my Redding small base die to size his 6PPC. It worked great, so he ordered one. However his new die was bigger by enough of a margin to make it useless for his purposes. Maybe that could be minimised by buying enough of the die at one time, but there are enough people out there offering to match a die to a chamber that it should never a problem to get a good fit when you need to.
D
Donald
Guest
Goodgrouper,
I don't always agrew with you, but you are spot on on your last comment. Congrats.
Donald
I don't always agrew with you, but you are spot on on your last comment. Congrats.
Donald
So whats the best way to achieve all of this? Do i send a fl sized case to the reamer maker, or is there another method? You mentioned something about a cast. I did some research on making a cast of a chamber a while back and the way i understand this is that a cast will shrink a bit, or can possibly shrink a bit? Thanks fellas. I hope that made sense i just woke up. LOL!! Lee
Boyd Allen
Active member
Goodgrouper is spot on. I have ordered reamers for a number of projects starting with a sized case from a specific die. There is one BIG advantage to this that has not been discussed. For calibers that Linwood Harrell does not make dies for, you can save a chunk of change doing it this way. What I have done, if it is available, is to start with a FL die, and some well used fired brass. I wan it as work hardened as possible so that the sized cases will be the largest that the die can produce. I lightly lube and size several cases, having first measured and recorded their dimensions at their shoulders (daimeters) and about .3 up from the head. This will vary with the die. I want the largest diameter above the extractor groove, that will be in the chamber. Then I size the cases, bumping the shoulder .001 with rimless cases, and remeasure looking for the largest case diameters. Form this, I dimension the body of the die. Depending on the use, I will specify the clearance that I am looking for. At the shoulder it has often been as little as .0005 for small cases in target/varmint applications. At the back of the case, I usually give more room, .001 to .0015.
In some cases, I have used one piece dies and figured out the chamber neck diameter so that I get the amount of neck tension and clearance that I want. Of course, given the neck IDs of normal FL dies, this resulted in a tight neck chamber. One one can also figure it out so that with the expander ball there is .002 neck tension, and without .003. When moving brass the expander does no harm to case straightness. When I have done this the brass and loaded ammo would make most Benchrest shooters envious. In a half dozen such projects the results have all been good.
In some cases, I have used one piece dies and figured out the chamber neck diameter so that I get the amount of neck tension and clearance that I want. Of course, given the neck IDs of normal FL dies, this resulted in a tight neck chamber. One one can also figure it out so that with the expander ball there is .002 neck tension, and without .003. When moving brass the expander does no harm to case straightness. When I have done this the brass and loaded ammo would make most Benchrest shooters envious. In a half dozen such projects the results have all been good.
Randy Jarvais
New member
For the really smart folks (not me), tweekers (Jackie, and Gene) and bullet makers (Robinette and others), they want chamber dimensions and throats that best match the bullet(s) they want to shoot/make. As they are starting with particular bullets, they then match the chamber according. Sometimes chambers evolve for a particular powder and/or density of powder. In either case the chamber is coming before the die. To get the chamber they need, they have to have the reamer, so the reamer also comes before the die. Others like me just copy others success and hopes it works for me, even though we may not know why. That is the usual sequence of thought processes in Benchrest so that is generally how it is approached, but as explained above, it isn't the only way to match a chamber and die. Randy J.