6BR (BRA) with 0.104” Freebore - Does this look right?

[samb300]

I’m trying to figure out if I’m crazy or not. I’m loading fireforming loads for my new 6BRA using virgin 6BR brass and 105 Hybrids. The barrel was chambered with a new JGS 6BRA reamer, 0.271” neck, 0.104” freebore. Barrel is a 0.237” Bartlein 4 groove.

Using a Hornady BTO tool, I’m measuring 1.819” to the lands, which ends up at 2.418” OAL (105 Hybrids measure 1.240” long).

Loading ammo and seating to the lands for fireforming, the bullets just look like they’re way out there already. I’m measuring approximately 0.165” of bearing surface in the neck, which seems like underutilized space considering the neck is 0.300” long. I tend to like to chase the lands as the barrel wears, and with this setup it doesn’t seem like I’ll have much opportunity for that.

The barrel is already made, so it is what it is. But I’m wondering if this is in line with what others are getting with 0.104” freebore in 6BR/BRA. If that’s the recommended freebore for the 105 Hybrids I don’t understand why it wouldn’t be more like 0.040-0.060” freebore?

Thanks,

Sam

 

[JEFFPPC]

Your set up is exactly how I have every barrel throated for the bullet I use.I almost never chase lands, just utilize the tuner.6brx, 6ppc, 6.5 x 47........

 

[swd]

It definitely looks more than .104”, probably closer to .140”. But just like Jeff that’s exactly how I throat almost everything. The BRA throats don’t move much anyways.

 

[Falfan2017]

Looks about right. Even if you chase the lands by .01 or .015 over the life of the barrel it’s still in the middle of the brass neck.

 

[samb300]

I should mention this will be for a PRS application, so no barrel tuners and generally high rates of fire for brief periods.

@Falfan2017 not sure if you meant 0.010-0.015”, but if the throat grows 0.100” there will be hardly any bullet in the case. It’s only 0.165” in there right now, basically dead center in the neck.

 

[gunsandgunsmithing]

See what a flat base looks like.

 

[expiper]

I’m trying to figure out if I’m crazy or not. I’m loading fireforming loads for my new 6BRA using virgin 6BR brass and 105 Hybrids. The barrel was chambered with a new JGS 6BRA reamer, 0.271” neck, 0.104” freebore. Barrel is a 0.237” Bartlein 4 groove.

Using a Hornady BTO tool, I’m measuring 1.819” to the lands, which ends up at 2.418” OAL (105 Hybrids measure 1.240” long).

Loading ammo and seating to the lands for fireforming, the bullets just look like they’re way out there already. I’m measuring approximately 0.165” of bearing surface in the neck, which seems like underutilized space considering the neck is 0.300” long. I tend to like to chase the lands as the barrel wears, and with this setup it doesn’t seem like I’ll have much opportunity for that.

The barrel is already made, so it is what it is. But I’m wondering if this is in line with what others are getting with 0.104” freebore in 6BR/BRA. If that’s the recommended freebore for the 105 Hybrids I don’t understand why it wouldn’t be more like 0.040-0.060” freebore?

Thanks,

Sam

Most of the time my 6mm Dasher bbls. wear ~ .003" per 100 rds,,,so 2000 rds = .060" of wear,,,you will still have .100 of shank (bullet grip) that will still work well,,,,what I have found to be minimum 'grip' is ~.060"...shoot it and enjoy every round,,,Roger

 

[Falfan2017]

I should mention this will be for a PRS application, so no barrel tuners and generally high rates of fire for brief periods.

@Falfan2017 not sure if you meant 0.010-0.015”, but if the throat grows 0.100” there will be hardly any bullet in the case. It’s only 0.165” in there right now, basically dead center in the neck.

Edited for accuracy yeah .015

 

[urbanrifleman]

You really might love the dtac

 

[CaptainMal]

fullsizeoutput_1486 by Larry Malinoski, on Flickr

Granted I am a little crooked in this fast photo but ...

This is .012" off the lands on a chamber cut with a .104" reamer. Move the bullet out that .012" and maybe another .004" for recession after 800 rds. and you have about what you have in your picture.

 

[Rich S]

Most of the time my 6mm Dasher bbls. wear ~ .003" per 100 rds,,,so 2000 rds = .060" of wear,,,you will still have .100 of shank (bullet grip) that will still work well,,,,what I have found to be minimum 'grip' is ~.060"...shoot it and enjoy every round,,,Roger

So far Im getting less throat movement with a BRA compared to Dasher. Ive heard others are seeing that also. I agree Id shoot it and see what happens. Keeps bullets out of neck junction and a little more case volume. I shoot 107 SMKs 0.020 off and 0.104 fb. Below is a pic. I wouldnt mind a little more fb.

 

[Boatschool02]

My last lot of 105 hybrids (newer production) were well over 1.270 long. Both they and the 105 Scenars would have done well with more than 0.100 freebore, seating very similar to the pic posted by Rich S.

 

[tclaunch]

My last tune with Hybrids had a jump of .035". Some forget to plan for that. Enjoy!

 

[powderbrake]

I run 105 hybrids in a 6BR with a .104 freebore. I push them .005 to .010 into the lands and they work fine. I also run the 88gr berger in the same gun (.104 freebore.)
I would assume you would push them hard into the lands for fireforming.

 

[CaptainMal]

I run 105 hybrids in a 6BR with a .104 freebore. I push them .005 to .010 into the lands and they work fine. I also run the 88gr berger in the same gun (.104 freebore.)
I would assume you would push them hard into the lands for fireforming.

For BRA you do not need to make land contact to fireform. They headspace on the shoulder right at the end of the neck. Now making a Dasher is a totally different issue. This thread was started with a picture of a standard BR case but the title had BRA in it. My picture is with the BRA case. Mostly I jump around .015" +- with the hybrids.

 

[JMayo]

Here's what I have at + - .001
108 bt