Modification to 30BR Reamer

jackie schmidt

jackie schmidt

New member
I have Dave Kiff grinding me a new 30BR reamer with one modification over the Robinette zero freebore we have now.

Randy's reamer is designed to be used with cases that are made into the 30BR by necking up the standard 6BR. The result is a case that has a length of about 1.525, quite a bit shorter than the originol 1.560.

We found that by making the cases by blowing them out, the result is a case with a length of about 1.545.

So, I am having Dave Kiff grind me a reamer to be used with a case that is made by blowing them out, rather than necking them up. The reamer length will be 1.550.

I should have it in about ten days.........jackie
 
As I read this, the .020 longer will be in the neck -- the shoulder will be in the same place. So I doubt it is horsepower; rather better case fit, less trimming.

In short, precision.

And on that theme, "Robinette" is the ADA in older Law&Order TV programs. The Iowa bulletmaker doesn't have an "e" at the end of his last name (i.e., Robinett)
 
Excellent idea...extra area ahead of the brass promotes carbon build-up and less pressure seal of the brass neck to chamber neck...I think it would reduce standard deviation (fps) in the load...lots of positives when the brass fits the chamber closely..
Jackie be sure to give it a new name like "Poison"..:D


Eddie in Texas
 
eww1350 said:
Excellent idea...extra area ahead of the brass promotes carbon build-up and less pressure seal of the brass neck to chamber neck...I think it would reduce standard deviation (fps) in the load...lots of positives when the brass fits the chamber closely . . .
Click to expand...
Only two things wrong with this post. The original reamer cut a chamber where the brass was "too long," not too short. The second is most PPC reamers cut a chamber with a bunch of room in front of the case mouth. The small number of 1.505 reamers win their share, but they don't repeatedly trounce the 1.515 or 1.520 reamers.

I think Jackie is doing it so he can fireform his brass without crunching the case mouth. It is a pain -- been there, got the T-shirt.
 
Charles

You got it. The way we make cases, you have to trim a bucket full of brass off the overall length when using the Robinett Reamer.

The reason we make cases by blowing them out is they come out so darned nice and straight. What we have is a 6BR barrel, with the neck portion reamed out to .330. When you fire a laoded 6BR round in it, out comes a perfectly formed "factory" 30BR case.

Just another attempt at making life easier.......jackie
 
Al

I did a while back, I think it is around .304-.305 after you fire it in a .330 neck chamber. I will check one tomorrow and see..........jackie
 
Jackie...

If you've got some guage pins in standard .0002 increments, fiddle around and see if the inside of the neck has some taper along it's length. -Al
 
Jackie

Well...I am confused..:confused:...If you plan to stick a 30BR reamer into a 6mm barrel to use for fireform brass...wouldn't you need a reamer without a pilot.???
If you had stated that in your original post it would be clear what your objective was...
If you are going to fireform brass instead of exspanding up why not get a neck dimension that would give you the bullet diameter I.D. of the brass when fireformed to make final neck turning easier?
I use my 30BR barrel and stick a 6mm bullet into the virgin 6BR case over a full load of Varget and fire thru my .330 neck 30 caliber barrel, then run it over an .308 exspander mandrel before neck turning to final fit...
 
eww

I have had my case forming rig for sometime now. I took a standard 6BR barrel, chucked it up and simply ran a .330 diameter chucking reamer into the neck portion. When you fire a loaded 6BR round in it, the neck expands to the .330, or there abouts.

You still have to run it over the appropriate expander to fit you neck turning tool. Especially the portion by the neck shoulder junction. It naturally gets thicker there because of the way the metal moves. Since I single point turn my necks in a lather, all ofthis happens when I push the case up on to the turning mandrel.

If you take a 6BR Lapua case, expand it up, and seat a bullet, the neck will measure about .330 for most of it's length, but it will have have a distinct hump up at the shoulder junction. But, this is a minimum neck turn operation, not much comes off untill you hit that hump, which is about .007 on diameter.

Al, I guess that answers your question. The neck, which is about .360 long, is pretty straight for about 1/4 inch, then it starts to get thicker due to the moving of the shoulder.

I do not look for many shooters to adopt this, the only reason I am doing it is because it is so easy. Load 6BR brass with a cheap bullet, fire it in the .330 neck barrel, turn the necks in the lathe, trim so all are the same length, (about 1.540), and go to the line.

As a note, I do my 30PPC in much the same manner. I fire a loaded 220 Russian in a 6PPC barrel, turning it into a non neck turned 6PPC. I then load this with a cheap 6mm bullet, and fire it in a 6PPC Barrel that has the neck reamed out to .332. What comes out is a "factory" 30PPC. I then neck turn, and go to the line........jackie
 
Poker Player

The difference is we have this great Lapua 6BR brass to play with.

Heck, back in about 1997, I took a 3x44 reamer, ran it in short, and made a "30x1.5", I used chopped off Winchester 300 Savage cases as the parent. I did it to shoot a once a year score match we had out a American Shooting Center.

Like I said, the big difference is we have that great Lapua Case to start with.

What would have been really nice is if Lapua would have made 7BR brass, (a true factory offerring), as well as the 6BR. Making 30BR would then really be a breeze.

Or, since the 30BR is so popular, just start making Lapua 30BR brass. But, they probably do not do that for the same reason they will not make a true 6PPC case. They don't need to, as they sell every piece of 220 Russian, and 6BR, that they make........jackie
 
jackie schmidt said:
Al, I guess that answers your question. The neck, which is about .360 long, is pretty straight for about 1/4 inch, then it starts to get thicker due to the moving of the shoulder.
Click to expand...

When you fireform them this way, the 'hump' is on the inside. Even when you neck them up over a tapered expander that moves the 'hump' to the outside, the neck i.d. will be tapered along it's length.

After making hundreds of 30BR cases using all the various methods, I'm a firm believer in making ;) the neck i.d.'s perfect before turning the neck o.d.
 
perfect necks

Al, can you share how you go about making the necks perfect on the inside? I would like to see your procedure detailed if you don't mind.

Thanks,

Joe
 
Al

I blew out a case late this afternoon, necked it up the rest of the way on the turning mandrel, turned the neck, and checked the ID afterward. It is absolutly straight all the way through.........jackie
 
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