Measuring bullets with chamber cut from Wheeler JGS 6BRA reamer

[urbanrifleman]

I ordered the 104 reamer from JGS and I cut two new barrels. If I measure a 108 Berger to the ogive I am getting 1.832. 80 berger was about 1.820.

That seems long to me, in fact it is longer than my PTG 127 FB reamer. I am not saying it looks wrong, maybe the angle is different.

 

[Dos XX]

Freebore diameter difference?

Your PTG isn't 127 as labeled?

 

[Alex Wheeler]

This will get you close, JGS is very good. I have over 100 reamers from them and not one screw up yet.
http://forum.accurateshooter.com/threads/measuring-a-reamer-freebore.3924672/

 

[urbanrifleman]

This will get you close, JGS is very good. I have over 100 reamers from them and not one screw up yet.
http://forum.accurateshooter.com/threads/measuring-a-reamer-freebore.3924672/

Oh, I didn't think it was a screw up. Just thought maybe the lead angle was more subtle. I was just asking if these numbers sounded right. I don't trust PTG... haha

 

[geraldgee]

@Alex Wheeler
Thank you for your considerable support for those of us who are trying to find our way through to the Promised Land....lol.

Can one determine the distance from case base to lands from the dimension listed on a reamer print?

Thank you in advance for your help.

Gerald

 

[urbanrifleman]

This will get you close, JGS is very good. I have over 100 reamers from them and not one screw up yet.
http://forum.accurateshooter.com/threads/measuring-a-reamer-freebore.3924672/

Man that is just great. So very cool of you to help us so much.

 

[Alex Wheeler]

@Alex Wheeler
Thank you for your considerable support for those of us who are trying to find our way through to the Promised Land....lol.

Can one determine the distance from case base to lands from the dimension listed on a reamer print?

Thank you in advance for your help.

Gerald

Not accurately. You really have to know where the lead angle will touch the ogive, thats different on different bullets. And your comparator wont touch there either. Chamber length, freebore diameter, and angles all change things a lot.

 

[geraldgee]

@Alex Wheeler

Thank you for the fast reply. I’ve tried more than a few times with reamers I’ve bought and had no luck whatsoever. I thought I was measuring wrong....thank you for your help.

Gerald

 

[jamesdmock]

I ordered the 104 reamer from JGS and I cut two new barrels. If I measure a 108 Berger to the ogive I am getting 1.832. 80 berger was about 1.820.

That seems long to me, in fact it is longer than my PTG 127 FB reamer. I am not saying it looks wrong, maybe the angle is different.

When figuring freebore, it seems to me that one must also consider the overall length of the chamber. i.e. if one reamer has an overall length of 1.550 inches, and another 1.570 inches, and both have .104 listed freebore; isn't it possible that the 1.570 has (in reality) .015 more freebore. This comment is from a NON_GUNSMITH, so take it for whatever it is worth. Good shooting...James

 

[urbanrifleman]

Well I tell you what looking at my split case 104 in this reamer is pretty darn long. No donut worries here. I need to check a DTAC. The 108 is 50 thou above the neck junction.

This is not a criticism, just learning more every day.

 

[gunsandgunsmithing]

When figuring freebore, it seems to me that one must also consider the overall length of the chamber. i.e. if one reamer has an overall length of 1.55 inches, and another 1.70 inches, and both have .104 listed freebore; isn't it possible that the 1.70 has (in reality) .015 more freebore. This comment is from a NON_GUNSMITH, so take it for whatever it is worth. Good shooting...James

Technically, freebore begins at the end of the chamber case neck and ends at the end of the parallel section, where the leade begins. "Effective" freebore will include the length from the end of your trimmed brass and also include the bevel(typically 45°) at the end of the chamber neck.

 

[Sheldon N]

For what it’s worth my 6BRA barrels with 104 freebore have both been around 1.780 to 1.1790 to the lands with varying bullets when new, with my Hornady comparator. Very similar to my 104 freebore Dashers.

 

[urbanrifleman]

For what it’s worth my 6BRA barrels with 104 freebore have both been around 1.780 to 1.1790 to the lands with varying bullets when new, with my Hornady comparator. Very similar to my 104 freebore Dashers.

That is what mine should be from my notes. This is longer than my 127 freebore it should be shorter. I will have to measure it when I get home, but I think something is up.

 

[urbanrifleman]

I ran home at lunch to measure that reamer because I wasn't going to be able to spend the rest of my day without knowing what it said. So I measured it using the Alex wheeler technique and it is exactly 104. So I guess I'm doing something about measuring my overall length is my guess. I use a split neck case to measure the touch and I always have good luck but since these chambers are 4 thou short they might be putting a crush on that pinch and forcing them to have a bunch of neck tension and jam them real far into the lands. That's a distinct possibility.

 

[Alex Wheeler]

Make sure that the bore of the comparator is clean use a copper solvent it doesn't take much to mess up a reading

 

[urbanrifleman]

Make sure that the bore of the comparator is clean use a copper solvent it doesn't take much to mess up a reading

Since the case is too long I won't be able to use the bolt to close.

 

[urbanrifleman]

I have come to conclusion that I have no way to measure this accurately until I firestorm some brass.

 

[Alex Wheeler]

Just bump the shoulder on a 6br case until its loose in the chamber then find your touch with the stripped bolt.

 

[Northridge]

A given Free bore to a given bullet or another is not going to be a linier measurement many in the same weight class will be very close but some options like a 105 Hammer (Barts bullets) will require fare less free bore to achieve the same touch point. Roy Hunter 103 requires a far shorter free bore for the same touch point 107 sierra is another example. in regard to JGS reamers I have many of there reamers as well in duplicates even that are "spec the same" but are ground differently, JGS is human as well. I find more variance in regard to touch point in the human doing it vs the given grind. don't be afraid to shoot a deeper throat you might be surprised unless its just simply to deep. my personal favorite is not our standard throat depth but quite a bit deeper and I have shot a lot of small groups on it. good luck

Shawn Williams

 

[KenOath]

A given Free bore to a given bullet or another is not going to be a linier measurement many in the same weight class will be very close but some options like a 105 Hammer (Barts bullets) will require fare less free bore to achieve the same touch point. Roy Hunter 103 requires a far shorter free bore for the same touch point 107 sierra is another example. in regard to JGS reamers I have many of there reamers as well in duplicates even that are "spec the same" but are ground differently, JGS is human as well. I find more variance in regard to touch point in the human doing it vs the given grind. don't be afraid to shoot a deeper throat you might be surprised unless its just simply to deep. my personal favorite is not our standard throat depth but quite a bit deeper and I have shot a lot of small groups on it. good luck

Shawn Williams

By deeper do you mean longer freebore?