Is there a book or reference that teaches how to specify reamer dimensions for BR barrel chambers for competition?

[Cassidy]

I've looked and cannot find books or references that teach how to determine, understand and specify dimensions on reamer prints for ordering reamers to chamber BR competition barrels; I shoot 100/200 yd 30BR. I'm trying to learn about this and have been unable to find a credible detailed reference to learn from. I know BR gunsmiths have determined their own print specs/dimensions for reamers that some are unwilling to share, but maybe there is a textbook or publication I can learn from. Any thoughts?

 

[Clancy]

Tag

 

[DaveTooley]

Not that I'm aware of. Here's the nuts and bolts part from 40+ years of experience. DON'T go too tight on anything. I stick with SAAMI bodies ( reloading dies have to work), neck diameter loaded round +.004" minimum, freebore diameter min +.0007" or more depending on application, over bullet diameter. Freebore length is where things get a bit tricky. There are several numbers that up to the total, leade angle is pretty standard 1'-30" for accuracy work.

 

[jackieschmidt]

I think you are logged onto it.
There are quite a few experienced, and credible, 30 BR shooter right here on this Web Site that will freely offer you advice on your subject.

 

[DaveTooley]

Call Jasmine at JGS and ask for the Robinette V2 reamer print.

 

[LVLAaron]

Call Jasmine at JGS and ask for the Robinette V2 reamer print.

They likely have the reamer in stock. They did when I ordered one.

 

[JGS_Jaz]

Call Jasmine at JGS and ask for the Robinette V2 reamer print.

I've got a document I can send out that explains each of the boxes on the prints too, if that's helpful.

Give me a call or email me at jasminejgsprecision@gmail.com

 

[Clancy]

Not that I'm aware of. Here's the nuts and bolts part from 40+ years of experience. DON'T go too tight on anything. I stick with SAAMI bodies ( reloading dies have to work), neck diameter loaded round +.004" minimum, freebore diameter min +.0007" or more depending on application, over bullet diameter. Freebore length is where things get a bit tricky. There are several numbers that up to the total, leade angle is pretty standard 1'-30" for accuracy work.

It feels good to hear someone of your stature say this. I said last year that if there’s one thing I’ve learned in the last 20 years…. It’s that cute little tolerances come back to bite us. I like a lot of neck clearance and a full .001 over bullet diameter in the freebore.

 

[DaveTooley]

It feels good to hear someone of your stature say this. I said last year that if there’s one thing I’ve learned in the last 20 years…. It’s that cute little tolerances come back to bite us. I like a lot of neck clearance and a full .001 over bullet diameter in the freebore.

I've got more than a few reamers where I got cute with tolerances. Like, hey if we tighten up the back end of the chamber the primer pockets will last longer. That shouldn't have even passed the first "Oh I have an idea" test.

 

[ELR LVR]

If you're asking how to custom Spec out your own reamer dimensions
or even just changing a few to suit yourself
the easiest way I know is to print out your reamer drawing
then use some white out and write in your dimension for whatever you wish to change
Note to the Reamer maker how many changes you made and what those changes are so they are aware of where&what you changed from normal.
-----------------------------------------------
I will tell Manson for example:
I want a 284 Reamer with these 3 changes
1. I want the neck dia to be XXX
2. I want the freebore to be XXX
3. I want the Shoulder dia to be XXX
Thank you
Please reference my sent Reamer Drawing Blueprint

Those are usually the 3 main dimensions I want to change so very often they can take an In stock reamer and simply regrind it to whatever you call out differently.
Unless you are coming up with a whole new design
Then maybe ask for a reamer drawing print like this with no dimensions called out for a blank slate

 

[jackieschmidt]

Just a note.
Concerning your shooting the 30BR.
The simple truth is, that wheel was invented quite a while back, and while there are minor differences in a few reamer designs, it is yet to be proven that any particular one shoots any better than a regular “zero Freebore .330 neck chamber coupled with a top quality 1-17 or 1-18 twist barrel.
One of the “odd” configurations is my reamer that simply has a longer neck than the standard variety 30BR case made from a Lapua 6BR case. This is a product of the way I make my cases, that being, I “blow them out” rather than necking them up. This retains much of the original 1.560 length of the Lapua 6BR case.
Hence, my trim to length is 1.545, and my reamer is ground to accommodate this.
Does it shoot any better, or any worse??……..No.

 

[Alex Wheeler]

Gunsmiths do this as part of their job all the time. Ask your smith to spec it out based on his experience. Just like any other trade. Hes the professional and has the experience. Its hard to mess up a zero freebore 30br reamer though.

 

[Cassidy]

Thank you all for your very helpful feedback. What I am trying to learn is the process of how to determine dimensions to cite on the reamer print (to order a 30BR barrel chamber reamer) that provides the smallest group size on the target for my 30BR rifle. From the above info it appears I need to focus on neck diameter and length for the reamer. Do you all test different reamer neck diameters and neck lengths for their resulting group size like you would for bullet seating depth, powder charge, case neck tension, barrel, case neck thickness, etc, as examples, though this would be expensive recognizing the cost for barrels, reamers and gunsmith work.

 

[Greg@wfcustom]

To Jackie and Alex’s point hit the easy button and order a “Robinette” reamer from JGS and call it a day. I use a .332 nk for my own personal preference re:neck turning, but you really have to work at it to screw up a 30 BR.
JMHO
YMMV
G

 

[Greg@wfcustom]

I've got more than a few reamers where I got cute with tolerances. Like, hey if we tighten up the back end of the chamber the primer pockets will last longer. That shouldn't have even passed the first "Oh I have an idea" test.

Been there done that, still got the damn things!
LOL
G

 

[Greg@wfcustom]

Call Jasmine at JGS and ask for the Robinette V2 reamer print.

^^^^
THIS

 

[Hal]

You might talk to Randy Robinette. See what he has to say.

Hal

 

[AlNyhus]

Thank you all for your very helpful feedback. What I am trying to learn is the process of how to determine dimensions to cite on the reamer print (to order a 30BR barrel chamber reamer) that provides the smallest group size on the target for my 30BR rifle. From the above info it appears I need to focus on neck diameter and length for the reamer.

Respectfully, this work has already been done and the map to success is well drawn. The JGS 30BR Robinett V2 is the Gold Standard of 30BR reamers and is the culmination of a couple of decades worth of tweaks and adjustments designed to work with the subtle changes in brass over the years.

Things like the leade angle and free bore length have been optimized to place the base of the .925" and 1.00" jacket length bullets precisely at a place in the neck to allow for the volume of the different powders used to 'fit' in the case at known velocity spots for accuracy.

Small tweaks can be made to suit personal preferences, of course. But within reason, none of these are going to make any positive differences 'on target'. And any change from the print will mean it's no longer a 'real' 30BR Robinett V2 reamer. It's now a one off. Which is neither good or bad...it just is what it is.

There's a time for experimentation and learning. For a 30BR, it's not with the reamer. I'd suggest you capitalize and benefit from the work that's already been done and learn about what makes a good reamer in reverse...by studying this one.

Time spent learning how to make good brass will provide 'way more benefits to your 30BR project. This, the use of wind flags (mandatory) and correct tuning are the big things that make little holes. Stay on the reservation by using a high quality barrel in the appropriate twist rate, assembled by an accuracy minded 'smith on a very good action, use true BR quality hand swaged bullets....etc.

No corners can be cut.

My 2 cents worth.... -Al

 

[Hal]

Al

Amen.

Hal

 

[Greg@wfcustom]

Al,
That puts the proverbial bow around it!
And you work to cheap, it’s worth a hell of a lot more than 2 cents!
JMHO
G