6br tips

[Frank Green]

I've always wondered what the tooling/process is for cutting rifling.
I assume it's done using a broach/broaching?

Broach cutting is similar but different. On a broach you have multiple cutters on a single tool and typically you pull it thru once and your done cutting.

We single point cut rifle. So just one cutting tool in the rifling head. We cut one groove at a time to a depth of about .0001" or so. After the cut pass the tool is fed back down the groove it just cut and then it will index to the next groove and repeat. After all the grooves where cut (lets say it's a 5 groove barrel) the tool will get advanced to cut another .0001" out of each groove and repeats and again after doing all 5 grooves the tool gets advanced again.

So for example a 30cal barrel with .308" grooves (each groove is .004" deep) your talking about 40 passes per each groove x 5 grooves in the barrel your looking at 200 cutting strokes alone. Will take around 1.5 hours to rifle one barrel.

Those are close ball park numbers.

 

[Frank Green]

This will give you an idea....

 

[beetroot]

Thanks, I didn't think broaching would be the right term but it was the closest I could think of.

This will give you an idea....

I acually watched that video hoping it'd answer my question, but didn't quite get there.
Impressive workshop/setup you have there.

 

[Rogerthatout]

Just finished a 6 BR build. I did a 24" for some damn reason and 200 rounds later I'm finding it's pretty slow. 30 gr Varget under a 105 hybrid gets me to 2793 fps. Not exactly what I was hoping for, wish I had gone with a longer barrel.

Shooting Berger 105s. My Bartlein chambered by SAC chronographed 2780 w 30g Varget for first couple hundred rounds in 35deg weather. Same 30g load in that rifle today, and at 85 deg and with a hot barrel now chronographs about 2810 (about 350 rounds on barrel)

My daughters Kreiger chambered by L3 Rifles was always a little faster out of the gate, chronographed 2830 shortly after break-in but now both barrels are shooting about the same… chrono says the Kreiger ifs faster but on range we share dope to 1000 yards. After trueing both rifles side by side. At 1013 yards, despite what the chrono says…. both rifles are giving us 2815 fps and we share same ammo. She’s jumping 20k off lands and I’m jumping 40k off.

I have another 6BR in progress for my next daughter, it will probably also take 30 g varget, I believe the OCW is 30 varget on this caliber.

I found this thread because I’m little perplexed with bump and shoulder measurements;

At datum point .350, I’m get measurements of virgin Lapua brass at 1.162 and once fired
brass is between 1.1635-1.1665 however my spec sheets shows measurement should be between 1.167-1.177…. Wondering why virgin Lapua brass is measuring below spec ???
What am I doing wrong or is my diagram wrong?

 

[iceng]

Virgin brass is (usually) a hair under size, so you can load and shoot, and NOT have to size before you load.

Some smiths believe in the imaginary "super tight chamber", which puts you under spec and means you have problems sizing brass.

If yours chambers, load and forget about it. Id guess its in spec. Gordon is no slouch.

 

[spife7980]

Shooting Berger 105s. My Bartlein chambered by SAC chronographed 2780 w 30g Varget for first couple hundred rounds in 35deg weather. Same 30g load in that rifle today, and at 85 deg and with a hot barrel now chronographs about 2810 (about 350 rounds on barrel)

My daughters Kreiger chambered by L3 Rifles was always a little faster out of the gate, chronographed 2830 shortly after break-in but now both barrels are shooting about the same… chrono says the Kreiger ifs faster but on range we share dope to 1000 yards. After trueing both rifles side by side. At 1013 yards, despite what the chrono says…. both rifles are giving us 2815 fps and we share same ammo. She’s jumping 20k off lands and I’m jumping 40k off.

I have another 6BR in progress for my next daughter, it will probably also take 30 g varget, I believe the OCW is 30 varget on this caliber.

I found this thread because I’m little perplexed with bump and shoulder measurements;

At datum point .350, I’m get measurements of virgin Lapua brass at 1.162 and once fired
brass is between 1.1635-1.1665 however my spec sheets shows measurement should be between 1.167-1.177…. Wondering why virgin Lapua brass is measuring below spec ???
What am I doing wrong or is my diagram wrong?
View attachment 8214350

Your datum’s is slightly different than their datum. Don’t worry about it, you are using a comparator, not a gauge; your relative measurements of your chamber are all that matters.

 

[Rogerthatout]

Your datum’s is slightly different than their datum. Don’t worry about it, you are using a comparator, not a gauge; your relative measurements of your chamber are all that matters.

Got it