Six Dasher neck Clarence

[kawsam62s]

Good morning everyone happy Labor Day on the 6mm Dasher how much neck clearance is required? I have a 271 chamber and my loaded round is .269. Thanks, Scott.

 

[Clancy]

Good morning everyone happy Labor Day on the 6mm Dasher how much neck clearance is required? I have a 271 chamber and my loaded round is .269. Thanks, Scott.

.004

 

[quest450]

My reamer is .270" loaded round .267"

 

[shoot4fun]

Good morning everyone happy Labor Day on the 6mm Dasher how much neck clearance is required? I have a 271 chamber and my loaded round is .269. Thanks, Scott.

While I have, due to a miscommunication, tried as little as .001 clearance and saw no issues with pressure I will SUGGEST having .003 would be good.
I do have one .271 ND in a Dasher that I found .005 to shoot better than any other ND but that is kind of an oddity I think.

 

[Clancy]

While I have, on a whim, tried as little as .001 clearance and saw no issues with pressure I will SUGGEST having .003 would be good.
I do have one .271 ND in a Dasher that I found .005 to shoot better than any other ND but that is kind of an oddity I think.

Not odd at all. I’ve been doing .004-.006 on purpose. Really helps when the brass thickens on later firings also.

 

[shoot4fun]

Not odd at all. I’ve been doing .004-.006 on purpose. Really helps when the brass thickens on later firings also.

I don't believe the neck walls actually do thicken as firings increase. While it's true brass flows toward the neck in firing that is the cause of the dreaded donut. That flow tends to build up at the juncture of neck/shoulder and not thicken the neck wall.
The main issue of turning .006 I see is the possibility of leakage and sooty necks. Not saying it will happen in every case of turning that much but it does have a greater chance.
In a review of my original post I will say that .001 clearance is NOT recommended at all. Even the best brass will not measure the same thickness all the way around the neck and the tiniest burr on a case mouth can give one a round that won't chamber when you need it.

 

[Bill Norris]

I don't believe the neck walls actually do thicken as firings increase. While it's true brass flows toward the neck in firing that is the cause of the dreaded donut. That flow tends to build up at the juncture of neck/shoulder and not thicken the neck wall.
The main issue of turning .006 I see is the possibility of leakage and sooty necks. Not saying it will happen in every case of turning that much but it does have a greater chance.
In a review of my original post I will say that .001 clearance is NOT recommended at all. Even the best brass will not measure the same thickness all the way around the neck and the tiniest burr on a case mouth can give one a round that won't chamber when you need it.

I have definitely seen turned necks thicken over a few firings with PPC and 30BR.

 

[Clancy]

@shoot4fun what happens if you get a little soot on the neck? Anybody die?

 

[shoot4fun]

I have definitely seen turned necks thicken over a few firings with PPC and 30BR.

Maybe I should qualify what I said by saying "depending on shoulder angle". The 40˚ shoulder is where donuts most often form from my experience. That also has a tendency to keep the length from needing trimming (both just what I observe from over 20 years of various 40˚ shouldered brass).
I will ask just how much thickening you have seen. If you started with, say, a neck turned PERFECTLY to .012 on a 30BR, shot it 10 times, cleaned it perfectly clean of soot in the neck and measured with 100% accuracy BOTH times then just how much thickening are you talking about?

 

[Bill Norris]

Maybe I should qualify what I said by saying "depending on shoulder angle". The 40˚ shoulder is where donuts most often form from my experience. That also has a tendency to keep the length from needing trimming (both just what I observe from over 20 years of various 40˚ shouldered brass).
I will ask just how much thickening you have seen. If you started with, say, a neck turned PERFECTLY to .012 on a 30BR, shot it 10 times, cleaned it perfectly clean of soot in the neck and measured with 100% accuracy BOTH times then just how much thickening are you talking about?

I've seen as much as .001 over 4 to 5 firings

 

[Bob3700]

I have been shooting a 6mm BRX for about five bbls now. Have my own .272 neck reamer.

My experience is that after about three or four firings, Donuts have formed at the shoulder neck junction.
Brass is all inside neck reamed (not outside turned) and after the above firings, my reamer will remove some brass at the neck junction.
Normally, bullets are not seated to that depth so it is not an issue. But if you were running a mandrel into your necks for uniformity, you would be pushing that brass to the outside of the case.
Just a thought.

 

[shoot4fun]

@shoot4fun what happens if you get a little soot on the neck? Anybody die?

It was a .223 bolt gun with a fast twist barrel. A good friend chambered it with his "no-turn" reamer. I loaded Lapua brass and shot it 2X. At a match soon after I had a round that would not chamber. I set that round aside for close inspection when I got home. All the measurements were good; shoulder bump, .200 line, seating depth, etc. so I decided to pull the bullet. That's when I found a very small burr at the case mouth. I removed the burr and seated the bullet again. When the round then chambered easily a light bulb came on in my brain. Measuring a few fired cases against a loaded round, I found fired at .251 and loaded at .250. I called the friend and asked about his reamer. He casually said it was spec'd for WINCHESTER brass which was a thinner neck wall than Lapua.
Short answer to reply to your soot question is with that little clearance there was no soot on the neck.
No one died and, believe it or not, that brass showed no excessive pressure even when it was pushing 80VLDs at 2900+ FPS.
Would I advocate doing it?HELL NO but I still have the rifle and all my body parts intact.

 

[shoot4fun]

I have been shooting a 6mm BRX for about five bbls now. Have my own .272 neck reamer.

My experience is that after about three or four firings, Donuts have formed at the shoulder neck junction.
Brass is all inside neck reamed (not outside turned) and after the above firings, my reamer will remove some brass at the neck junction.
Normally, bullets are not seated to that depth so it is not an issue. But if you were running a mandrel into your necks for uniformity, you would be pushing that brass to the outside of the case.
Just a thought.

I have never liked the idea of inside neck reaming. If a donut becomes a problem I believe it is probably better to push it out with a mandrel and turn it off on the outside. It's tricky either way but at least I don't take more off the inside.

 

[JeffSummers]

No

 

[JeffSummers]

No

Did not mean to reply, It was an accident.