6br 0FB question

[NC/Br Shooter]

I had this question come up in a conversation over the weekend and everyone had an opinion but no definitive answer.
So the purpose of 0 freebore in the Br is pretty straight forward. But what should the lead angle be if you want to use 0 freebore for 6br?
Or should you use the standard 1.5 or 1.3 angle?
In 0 freebore, that's really the only other dimension that can change much of anything I'm thinking.
The whole purpose of the conversation was about having a reamer made.
I also know there had been some experimenting done with this, so if you know about any old threads on the topic, I'd be all about reading them.
I search it, but seems as though the threads are maybe titled something else.
Would lead angle make that big of a difference anyway?
Thanks

 

[gunsandgunsmithing]

I had this question come up in a conversation over the weekend and everyone had an opinion but no definitive answer.
So the purpose of 0 freebore in the Br is pretty straight forward. But what should the lead angle be if you want to use 0 freebore for 6br?
Or should you use the standard 1.5 or 1.3 angle?
In 0 freebore, that's really the only other dimension that can change much of anything I'm thinking.
The whole purpose of the conversation was about having a reamer made.
I also know there had been some experimenting done with this, so if you know about any old threads on the topic, I'd be all about reading them.
I search it, but seems as though the threads are maybe titled something else.
Would lead angle make that big of a difference anyway?
Thanks

I know testing has been done but there are soooo many variable that I think that testing is just scratching the surface, with only small if any gains realized on the target. Yes, it'll change seating depth but what does that amount to if the target looks the same.

I guess the real question I have is what are you looking for from changing lead angles? If it's better accuracy, I think it's very bullet specific and still not sure if gains are made or not. It's also powder specific, in optimizing how pressure builds but again, not sure if any gains are made.

If you wanna optimize powder fill rate, different story but that can be done with freebore, too.

I think ideally and ultimately, it's another example of we just have to test ourselves to know and even then, with specific projectiles and powders. You might find a combination that shows some improvement but not necessarily with different components.

Bottom line is, the common 1.5° angle is a known commodity that works well. When you change that, you may or may not change a lot of what we know to work.

Again, test, test and test some more. That's where the answer lies. Personally, I don't think there is any magic here, at least not with cf and reloadable cartridges, where we can already control maybe 90+ percent of what an angle change MIGHT give us.

One more thing and I'll stop but I don't think a zero freebore is ideal for any bullet in a 6BR but there are reasons some use it and yes, it'll work, especially with the really short bullets, like 58's etc. Part of the beauty of a 6BR is that long neck, which is very forgiving. I can see potential for a slight velocity increase, with the right components. Regarding the 1.3° lead, it may stave off the peak pressure a tad, allowing a few fps gain. Not sure.

 

[Clancy]

Buddy you are gonna drive yourself mad with this freebore business.

0- almost useless, half decent for 55 boattails

50- exceptional with 65-70 grain bullets

80- mid sized boattails

104- mid sized to 105 boattails and 70/80 flat base bullets

120 to 135- 108s, 109s, probably 115s but I’ve not seen anyone run those in a BR


1/30 lead on everything round here.

 

[gunsandgunsmithing]

Buddy you are gonna drive yourself mad with this freebore business.

0- almost useless, half decent for 55 boattails

50- exceptional with 65-70 grain bullets

80- mid sized boattails

104- mid sized to 105 boattails and 70/80 flat base bullets

120 to 135- 108s, 109s, probably 115s but I’ve not seen anyone run those in a BR


1/30 lead on everything round here.

Yeah, this!

 

[NC/Br Shooter]

What is the standard. Then,. What was the reason for going from 1.3'to 1.5?
Is one better than the other?
That's the question
0 is obviously for 70g under bullets.

 

[gunsandgunsmithing]

What is the standard. Then,. What was the reason for going from 1.3'to 1.5?
Is one better than the other?
That's the question
0 is obviously for 70g under bullets.

Standard is 1.5 and has been for a really long time, with very few exceptions.

As for one being better than the other...that's kinda my point. With few exceptions and for very specific components, I don't think there is a clear advantage, one vs the other. I also think that's why you see so little test results. Just not much to be gained there and what you may or may not gain with one very specific set of components...you may see the opposite with the next.

FWIW, 1.3 is "flatter" than 1.5 so it kinda negates the very short freebore. To delve deeper, we simply need more info, like what is your goal?

 

[NC/Br Shooter]

That's useful information. The other decision was in choosing a reamer 1.3 or 1.5 angle. I ran into a shooter who had a 0 freebore chamber and he definitely said his was 1.3. And I had a chance to buy a reamer but backed out, it was 1.5.
So that was another reason I was asking.
That's all

 

[gunsandgunsmithing]

That's useful information. The other decision was in choosing a reamer 1.3 or 1.5 angle. I ran into a shooter who had a 0 freebore chamber and he definitely said his was 1.3. And I had a chance to buy a reamer but backed out, it was 1.5.
So that was another reason I was asking.
That's all

I wouldn't let it stop me at all. In fact, I'd feel better about a 1.5 while I'm not sure I could tell the difference other than in seating depth.

Invariably with as many members as are on here, you're likely to have someone come and tell us how great their 1.3 is and it might be! That doesn't change that by far the most common is 1.5 and that it's a known commodity, either way. I would not be at all surprised that it works just fine.

FWIW, look closely at any reamer print's tolerances, too. You might be surprised by all makes in this regard. We're splitting a hair that they won't claim to be able to grind the reamer to within.

 

[urbanrifleman]

Stop looking at the front of the bullet and look at the back of the bullet.

The only thing that matters is the location of the pressure ring in the neck.

And frankly, most people that are talking about freebore, acting like 20 thou will make or break a chamber, are misinformed about what 20 thousandths is...

 

[urbanrifleman]

That's useful information. The other decision was in choosing a reamer 1.3 or 1.5 angle. I ran into a shooter who had a 0 freebore chamber and he definitely said his was 1.3. And I had a chance to buy a reamer but backed out, it was 1.5.
So that was another reason I was asking.
That's all

What is the freebore diameter? That effects the freebore more than that micro change in that angle.

 

[urbanrifleman]

What is the inside diameter of the barrel?

That effects the final location of the bullet also.

 

[NC/Br Shooter]

What is the inside diameter of the barrel?

That effects the final location of the bullet also.

Both the shooters chamber was 0, and the reamer in question I was looking at was 0.

 

[urbanrifleman]

Both the shooters chamber was 0, and the reamer in question I was looking at was 0.

My reamer is 30 FB.

The difference between those two is less than 1/32 of an inch.

Zero is too short for 80 grain bullets. Bart was shooting his 80 grain bullets with 104 fb.

Zero is too short for 68 bullets too IMHO. Unless you are purposefully trying to reduce the case capacity.

 

[gunsandgunsmithing]

My reamer is 30 FB.

The difference between those two is less than 1/32 of an inch.

Zero is too short for 80 grain bullets. Bart was shooting his 80 grain bullets with 104 fb.

Zero is too short for 68 bullets too IMHO. Unless you are purposefully trying to reduce the case capacity.

Just using Bergers as a reference here, the bearing surface length of their 80 fb and 105 vld Bt is near identical.
The long neck makes the little BR case very forgiving to freebore. With a 1.5 angle, I use the same .098 fb reamer for bullets from about 62-105 grains. Pretty sweet there. Yes, I agree that people get carried away with fb length. I've had people tell me they had to have a .104 and that my .098 with 105's. Really now? The internet is a wonderful thing isn't it? I could post pics but it's not worth it. The .098 has room to spare and works just as well as a .104.

I can't even remember how long I've had that .098 reamer but I think every single br bbl it's ever cut has won matches. And it still cuts great. Looks way better today than most of my new reamers, sadly.

 

[urbanrifleman]

Just using Bergers as a reference here, the bearing surface length od their 80 fb and 105 Bt is near identical.
The long neck makes the little BR case very forgiving to freebore. With a 1.5 angle, I use the same .098 fb reamer for bullets from about 62-105 grains. Pretty sweet there. Yes, I agree that people get carried away with fb length. I've had people tell me they had to have a .104 and that my .098 with 105's. Really now? The internet is a wonderful thing isn't it? I could post pics but it's not worth it. The .098 has room to spare and works just as well as a .104.

I can't even remember how long I've had that .098 reamer but I think every single br bbl it's ever cut has won matches. And it still cuts great. Looks way better today than most of my new reamers, sadly.

I'll take the one NOT ANYWHERE near the donut.

People seem to also miss that people never shot the ppc with 68s with a zero freebore.

Why would anyone think the bullet would care what case it was being shot from? The back of the bullet is still in the same place.

 

[BRGUY]

Leade angle - 1 1/2 degrees

Throat diameter - .2430 plus .0000 minus .0001

0 Free bore

I have more than 10 different 6mm rifles and pistols in various cartridges set up this way, and all are superbly accurate! Granted, an 80 gr. Flat Base bullet is the heaviest bullet weight that is shot in these guns.

I shoot these same throat dimensions in one of my 6mm B-R rifles and have won several matches with it, shooting at 100, 200 and 300 yards...

Just my 2 cents worth and nothing else. Everyone has the right to shoot what they like without being criticized for it.

Carry on.

 

[gunsandgunsmithing]

Leade angle - 1 1/2 degrees

Throat diameter - .2430 plus .0000 minus .0001

0 Free bore

I have more than 10 different 6mm rifles and pistols in various cartridges set up this way, and all are superbly accurate! Granted, an 80 gr. Flat Base bullet is the heaviest bullet weight that is shot in these guns.

I shoot these same throat dimensions in one of my 6mm B-R rifles and have won several matches with it, shooting at 100, 200 and 300 yards...

Just my 2 cents worth and nothing else. Everyone has the right to shoot what they like without being criticized for it.

Carry on.

Well, I certainly hope you aren't talking to me, as nothing I said was intended as criticism toward anyone.

 

[Clancy]

I set up my most recent BR with a .104 specifically to shoot 80s, contradictory to what I posted above?

Why? Because it’ll never get hot in its life, and max controllable speed was the goal. Ideally, it would have been an .080 or even a .050 in a barrel burner, but like some of y’all are saying, there’s some flexibility to this.

With N135 being chunky, I’d go a little longer if that was the plan, which it was.

 

[BRGUY]

Well, I certainly hope you aren't talking to me, as nothing I said was intended as criticism toward anyone.

Nope, just general conversation. Nothing intended towards anyone. My apologies if it came off as negative criticism or otherwise.

 

[Flyshooter]

My experience........ 6br “0” freebore is fantastic for varmints or pounding steel using any bullet from 55-70 bullets.

Having chambered at least 30 barrels with the “0” freebore reamer and using most of today’s popular barrel manufacturers it becomes apparent the “0” freebore is perfect for lite bullets all the while easily shooting tiny tiny groups at blisteringly high velocities......barrel life seems to be forever. One of the top PD set-ups there is......in my experience.

Seems I’ll continue to chamber 6BR “0” freebore barrels until my passport expires.