6mm BR vs 6.5x47?

[Erik Cortina]

Erik, Jason, what factors/considerations went into your decision on 0.175 and 0.220 freebore, respectively? I am trying to understand the factors that bear on setting (how to determine) the freebore for a reamer for a 6.5x47L.

I wanted a do it all freebore. My first 47 had a .200" freebore and it worked great for the 139 gr. Scenars, but I wanted to be able to shoot 123's and it was slightly long for them. The .175" freebore will handle all bullets.

 

[Cassidy]

Erik - what do you measure to come up with the freebore dimension? Do you measure the bearing surface length of the intended bullet, plus leave so much room to seat the bullet, plus so much length for the ogive to touch the lands plus maybe 0.020 into to the lands assuming this is near the jam? What factors like this do you measure?

 

[Erik Cortina]

Erik - what do you measure to come up with the freebore dimension? Do you measure the bearing surface length of the intended bullet, plus leave so much room to seat the bullet, plus so much length for the ogive to touch the lands plus maybe 0.020 into to the lands assuming this is near the jam? What factors like this do you measure?

I had a .200" freebore and simply shortened it.

 

[Eric Leonard]

ok,,Erik can you tell me my freebore,,I load the 123 Scenars at 2.720 for a .010 jump,,
the 140 Hybird is 2.840 .010 jump,,

it will also load the 108 Scenar to a .010 jump and the 100 NBT .010 jump with plenty of bullet in the case,,

whatever it is has to be the most versatile case/throat for a short action feed from AI mags ever devised,,it will shoot just about any bullet with any reasonable powder very well,,

got a 6 BRDX coming to see how they compare,,

 

[Cassidy]

Thanks, Erik!

 

[tclaunch]

ok,,Erik can you tell me my freebore,,I load the 123 Scenars at 2.720 for a .010 jump,,
the 140 Hybird is 2.840 .010 jump,,

it will also load the 108 Scenar to a .010 jump and the 100 NBT .010 jump with plenty of bullet in the case,,

whatever it is has to be the most versatile case/throat for a short action feed from AI mags ever devised,,it will shoot just about any bullet with any reasonable powder very well,,

got a 6 BRDX coming to see how they compare,,

The reamer print says .1634" FB for the JGS reamer I used. Its within .012" of Eriks favorite FB.

 

[/VH]

tclaunch,

Would that be JGS print #2124?

 

[Eric Leonard]

mine is an 8 twist 28.25 inch Bartlien tclaunch chambered for my practical rifle on a Stiller Tac 30 and to my surprise shoots the 100 NBT in .250 groups at 100 yards at 3250 fps with IMR 8208XBR,it will also bughole the 108 Scenar at 3200 with RL15,,it shoots the 123 Scenar at 3025 with RL15 and H4350 extremely well and the 140 Hybird pretty dang good with H4350 at 2800,,

at 1,000 rounds everything looks very good and very minimal wear

I cant see why you would not use the 8 twist,,

 

[mattri]

mr.big- sounds like the 140s aren't doing as well as the others for you- any guess as to why?

 

[Cassidy]

I'm trying to figure out the freebore on my reamer drawing; there is no dimension that specifically states "Freebore" on the drawing. There are, however, two dimensions in the neighborhood of the freebore: (1) the dimension starting from the end of the chamber neck (including the bevel between the end of the chamber neck and the start of the freebore [I use the term freebore here because I don't know what else to call it]), and (2) the dimension starting from the bevel-freebore junction to the end of the freebore (where the lands starts). Does the freebore dimension on the reamer drawing start at the neck-bevel junction (does it include the length of the bevel), or not? I am trying to figure out what specifically the freebore dimension is on my reamer drawing.

 

[Eric Leonard]

after looking back at my notes I think the 140 Hybirds I had were bad lot,,I could reach the 2920 node with RL15 but it would have wild fliers,,and I couldnt get enough of the lot of H4350 in the case to reach the 2920 node with the 28 inch barrel,,,

with the way the 123 Scenars shoot I may try the 136-139 Scenars with the RL15 load and see if the Scenars will eliminate the fliers at the 2920 node,,I have also been advised to try the 142 SMK,,

I was so happy with the 123`s at my normal 600 yards that I never really tried to solve the 140 load,,

what other powders would you try to get accuracy at 2920 with the 140 Hybird??

 

[tclaunch]

tclaunch,

Would that be JGS print #2124?
[/quote

Yes

 

[/VH]

Thanks tclaunch,

I have an 8.5 and an 8 twist cut with a reamer of the same print #. Just wanted to know for the purpose of comparison with what I may be able to glean from this thread.

 

[DennisH]

I was so happy with the 123`s at my normal 600 yards that I never really tried to solve the 140 load,,

Same here, Dennis

 

[afrench]

I'm trying to figure out the freebore on my reamer drawing; there is no dimension that specifically states "Freebore" on the drawing. There are, however, two dimensions in the neighborhood of the freebore: (1) the dimension starting from the end of the chamber neck (including the bevel between the end of the chamber neck and the start of the freebore [I use the term freebore here because I don't know what else to call it]), and (2) the dimension starting from the bevel-freebore junction to the end of the freebore (where the lands starts). Does the freebore dimension on the reamer drawing start at the neck-bevel junction (does it include the length of the bevel), or not? I am trying to figure out what specifically the freebore dimension is on my reamer drawing.

#2

 

[/VH]

Cassidy/ntexaslongshot,

Honestly, I don't recall whether the bevel between the neck and cylindrical "freebore" is technically considered as part of the freebore. I don't think it is, I was coached on this very well, several years ago by a very fine gentleman to speak with at JGS, I just can't remember. I believe his name is Cary. I expect he would welcome your call and be very kind and patient, as he was with me, when I called and would be happy to walk you through any reamer print dimensions that you have a question about.

I also can't for sure remember whether I have ever spoken directly with Dave Kiff but it is my understanding that he is great to deal with and I expect that he would also be happy to answer your questions.

Sorry I can't answer straight up but these two guys won't give you the wrong answer.

 

[Erik Cortina]

Freebore does not include the transition angle between neck and freebore.
Reamer prints usually show two dimensions like Cassidy found out, the shortest one is the freebore.

 

[stansrifles]

I would post your reamer print there is a lot of people on this forum that could read your print an explain the amount of lead an freebore.
Stan

 

[mattri]

Thanks again for such great replies.

I am looking for a round to use for field/practical shooting. It will be a singe shot, barrel around 26". I will of course shoot from a bench but not looking to be a br rifle, would like to look at F-Class down the road. The farthest I have to shoot at the moment is 600 yards, majority of shots will be at that distance. Not planning to hunt with it but may do some varminting.

From everything I can tell a 6br, Dasher or 6.5x47 would all work about as well.

Thoughts?

 

[DennisH]

All 3 will work.

Out of the three, all of which I own, the 6.5x47L shooting 123 grain Scenars out weigh the other 2 just slightly. The Dasher is very close, somewhere in the tenths. The 6br is the best all around cartridge.

I just like my 6.5x47L and always have great results.

Dennis