Reamer questions - Neck diameter of 17 FB with Lapua brass and freebore

[kmcdonou]

My 'smith is going to make me a 17 Fireball and I wanted to buy the reamer. I called PTG and specified I was planning to use 221 Fireball brass from Lapua, didn't want to turn necks, and was planning to shoot 20-25gr bullets. I didn't state the bullets in particular, but am thinking the 20gr V-max, 21gr Kindler Gold, and 25gr KG.

I got back the following print:



My main concern is with the .011 freebore. I've frequently read where people use a 0 freebore. Is .011 too much?

Also, I don't have the dies and brass yet to confirm the neck size. I assume PTG are on the ball and have a good idea, but those of you that form 17 Mach IV or 17 FB from Lapua 221 FB can you tell me the finished neck diameter?

Thanks much.

 

[Phil]

Mine is zero freebore, but .011 isn`t very much.....a human hair averages .003.

Grab a dial caliper and set it to .011, the visual should ease your mind, I`d run it in a heart heat.

Good luck with your project,

Phil.

 

[AckleymanII]

I see .015 + .026 + .011 = .052 on that print. .052 is your real number, not .011

you can change the print to start the leade angle right at the case mouth and that would help and also designate zero freebore. I did this on my 17 Mach 4 reamer, and it shot like a house a fire on every barrel used.

 

[kmcdonou]

Ok, I didn't realize how to read the print. So freebore is the lead plus the throat plus the distance where the chamber narrows down?

If I revise my print the way you suggested will it handle 20-25gr bullets of all types well?

 

[kmcdonou]

Actually, isn't freebore traditionally considered the leade, which in my case is .011? Technically, I believe your position of including the "mean little shoulder" length (Salazar's term in this article http://riflemansjournal.blogspot.com/2010/09/basics-leade-angle.html) is also part of the freebore measurement, but I don't see too many people including that. I haven't really come across people including the throat in the freebore measurement.

I am not sure what you mean by "you can change the print to start the leade angle right at the case mouth and that would help and also designate zero freebore." Can you explain that more?

 

[Phil]

Keith,

The freebore is .011, plus the lead .015 that equals the .026 listed on the print. you added the .015 and the .011 in to the equation when it was already included in the .026.....

.026 is the total freebore including the .015 lead.......

If you spec`ed this reamer at ZERO freebore you would still have .015 in the lead, unless you had that removed too......

Phil.

 

[kmcdonou]

Just for curiosity sake, I looked at a minimum SAAMI spec for the 17 FB (see below). According to those specifications the available freebore is 0.173 (1.5930 - 1.420). That is about 6x more freebore than the 0.0263 on the print that Dave at PTG sent me. How come so much more freebore for a minimum SAAMI? Is that to accommodate 30gr bullets? Are 30gr bullets that long?



Also, the neck in the SAAMI print appears to be .206. I asked someone on a different forum who has the same reamer print as me and his loaded Lapua rounds are .201. Does only having .002 clearance in neck diameter ok? I thought I read where .003 is better. Curious as to the opinions of those that have more experience.

Don't get me wrong, I am not fretting about this. I am just new to it and want to understand so I know I am making the right decisions for my use.