Education and Confirmation Time Re: Reamer Specs Related to 'Freebore'

[Dusty Stevens]

It seems like a relevant need in this community is a software program that allows you to input the chamber reamer specs from shoulder forward, input the bullet brand, caliber, weight via bullet part number, and have the software show the overlay of the reamer cut and bullet overlay -- allowing the the user to select bullet placement in the neck area and lands area -- then one could proactively better assess their bullet selection and options to save time, grief, money, and gunsmithing resources.

all you gotta do is ask. 99% of the gun builders out there will have your answer. And .100fb on a .22 cal anything under a 75-80gr will be longer than what i feel like youre wanting. Like was said above youll need a zero to .045 max for a 40-52gr bullet. Call jgs and tell em what you want to shoot and they will tell you what you need, rather than giving them a number and hoping you was right.

 

[338 dude]

View attachment 1189518
Here's what I've got on hand: Top - 40gn Sierra Blitzking, 50 VMAX, 55 VMAX, 69 Sierra Matchking, 80 ELD, 90 Berger VLD, 88 ELD, and 95 Sierra Matchking. Loaded rounds top and bottom are 88ELDs at a 0.010" jump to the lands. As you can see, with this freebore you wouldn't be able to load the 40-69 without a pretty decent jump, and even then you'd only have the smallest amount of neck to hold the bullet.

That is an awesome display and is easily understandable

 

[DaveTooley]

Thanks, Boyd. I understand that option.

It seems like a relevant need in this community is a software program that allows you to input the chamber reamer specs from shoulder forward, input the bullet brand, caliber, weight via bullet part number, and have the software show the overlay of the reamer cut and bullet overlay -- allowing the the user to select bullet placement in the neck area and lands area -- then one could proactively better assess their bullet selection and options to save time, grief, money, and gunsmithing resources.

There is still more trial and error than is necessary with today's technology. I appreciate the answers and feedback. Keep it coming with relevant input.

It's not trial an error for some. Take your chosen bullet, set your calipers -.001" under bullet diameter. Scribe a line using the calipers on the ogive of the bullet. That line will be very close to the contact area with the lands. Take your freebore diameter and lead angle and do the trig to calculate the distance from the end of the freebore to groove diameter.
then it's simple math. For a freebore that's .0005" over nominal bullet diameter you're talking about approximately .014" with 1'30" lead angle. Take the amount of bullet you want outside the case, subtract .014" in this case. That gives you the freebore length. I always fudge about .025" shorter. The reason may surprise you. Dies wear, dies wear out, nothing stays the same. No two lots of bullets with the same product number are exactly the same. So your suggestion of a data base by product number isn't practical.

 

[6and7mm]

The sooner you order the reamer you want, the sooner you’ll get it.

Amen to that.

 

[6and7mm]

It's not trial an error for some. Take your chosen bullet, set your calipers -.001" under bullet diameter. Scribe a line using the calipers on the ogive of the bullet. That line will be very close to the contact area with the lands. Take your freebore diameter and lead angle and do the trig to calculate the distance from the end of the freebore to groove diameter.
then it's simple math. For a freebore that's .0005" over nominal bullet diameter you're talking about approximately .014" with 1'30" lead angle. Take the amount of bullet you want outside the case, subtract .014" in this case. That gives you the freebore length. I always fudge about .025" shorter. The reason may surprise you. Dies wear, dies wear out, nothing stays the same. No two lots of bullets with the same product number are exactly the same. So your suggestion of a data base by product number isn't practical.

Dave, I super respect your advice and direction. However, when you share that the concept isn't 'practical', I would comment back that it may not be technically practical, but that it would provide a decent indicator as a place to start, because, as you say, there are the various variables. And we will all face the final need to create a spec for the appropriate reamer.

I will likely do the following:
Order the reamer with zero freebore and a .254 neck diameter, with an OAL of 1.560".
I would also order a separate throating reamer.

Question: What diameter should I spec out for the throating reamer?

Thanks Dave and others for the relevant feedback.

 

[DaveTooley]

Dave, I super respect your advice and direction. However, when you share that the concept isn't 'practical', I would comment back that it may not be technically practical, but that it would provide a decent indicator as a place to start, because, as you say, there are the various variables. And we will all face the final need to create a spec for the appropriate reamer.

I will likely do the following:
Order the reamer with zero freebore and a .254 neck diameter, with an OAL of 1.560".
I would also order a separate throating reamer.

Question: What diameter should I spec out for the throating reamer?

Thanks Dave and others for the relevant feedback.

Sounds like you have it figured out.

 

[6and7mm]

Sounds like you have it figured out.

Dave, what would be your answer to my last question?
Question: What diameter should I spec out for the throating reamer?

 

[6and7mm]

Okay, a quick conclusion and follow-up.

For a 22 BR chamber that will need to work with Lapua and Norma 6BR brass, and for the .224 lighter bullet class of 40-60 grain, the JGS reamer print number is: #0846.
This reamer incorporates the following:
A) Neck dia. .254"
B) .200 line measurement of .4714"
C) OAL of 1.570"
D) Throat/lead of 0.020"
E) live pilot
Cost: $180 as of this posting
Wait Time: Approx. EIGHT weeks as of July 2020