Neck Clearance in F class?

[Rtheurer]

I am of the understanding that More Neck Clearance for the top F class shooters has gone up and over .002 as of the last few years and Tight Neck Cases at .002 and below have pretty much for the most part gone by the way side.

Personally I look for .003 and more. Just wondering what the Belly Benchrest guys are doing and what the trend is.

 

[XTR]

In my F-TR rifles I shoot unturned WW brass in a .342 neck, Loaded cases are at about .332 so somewhere about .010 for me.

When/If I run unturned Lapua the loaded necks are closer to .336 if I recall correctly, so .006 then.

I anneal almost every time, and I've never split a neck before I lost the pockets.

 

[Dusty Stevens]

Too much clearance wont hurt accuracy but too little will. Consistent necks are the key and they gotta at least be skim turned to be consistent. You just gotta decide if that little bit of extra work is necessary for your accuracy requirements

 

[savagedasher]

In my F-TR rifles I shoot unturned WW brass in a .342 neck, Loaded cases are at about .332 so somewhere about .010 for me.

When/If I run unturned Lapua the loaded necks are closer to .336 if I recall correctly, so .006 then.

I anneal almost every time, and I've never split a neck before I lost the pockets.

Excess neck clearance works the brass more so you should split the necks. If the bras has more clearance your running less case pressure so the primer pockets will last longer. Larry

 

[Dos XX]

I run.006 clearance with turned Lapua for .308 Win. I used to run tighter but am much happier with .006.

If you control necks with bushings, .006 is not so much that you have to size in 2 steps.

 

[KWeigel]

4 thousands. Dasher and 6.5x47

 

[XTR]

In F-TR there was talk last yr that the Canadians would be running chamber checks that included confirming that the neck was not below minimum SAAMI (i.e. thight neck). I seem to recall that they backed off on that one, but it could come back. If I recall the minimum SAAMI for a 308 is actually .3425, so you run less at your own peril if you plan to shoot the Canadian Nationals or the Worlds.

Since i started shooting F-TR competitively about 5 yrs ago I have never split a neck, I've worn out several 308 barrels and have a 5 gallon bucket about 1/3 full of cases from both WW and Lapua that have lost their primer pockets

 

[Dos XX]

I currently run a .341 neck. I would have no problem running a .3425 neck.

Split necks is not something I worry about. I anneal every firing. As Wade noted, primer pockets are going to be gone before neck splitting will occur.

 

[Dusty Stevens]

Turn em thin to win

 

[Scott Harris]

Turn em thin to win

Correct me if I'm wrong Dusty, but Jack meant you need to have plenty of clearance between the chamber neck and cartridge neck. right?

I prefer .006 clearance for all of my cartridges.
.340 chamber and .334 loaded round for the 308 WIN
.317 chamber and .310 loaded round for the 284 Shehane
.294 chamber and .289 loaded round for the 6.5x47 Lapua

 

[Dusty Stevens]

Correct scott. Could be any size what he means is have plenty of clearance

 

[Rtheurer]

So the Next question is of these responses who is shooting in the .3 and .4's at 100 during testing?
Thanks again Fellas.

 

[Ringostar]

I use .005 on my 284 F open barrels.

 

[Dusty Stevens]

I can shoot less than .2's. Im a br shooter- if i couldnt i need to quit

 

[Keith Glasscock]

So the Next question is of these responses who is shooting in the .3 and .4's at 100 during testing?
Thanks again Fellas.

How do I want to say this? If it isn't in the .3's or smaller at 100, something needs tuning for F-class. I'm not sure I would even consider taking a barrel that doesn't shoot better than .3" @ 100 to a major match. Of course, I'm not in the situation of not having a backup barrel right now.

 

[Dos XX]

Smaller than that.

 

[XTR]

It's not a load if it doesn't shoot an inch vertical at 300 yards.

 

[Laurie]

In F-TR there was talk last yr that the Canadians would be running chamber checks that included confirming that the neck was not below minimum SAAMI (i.e. thight neck). I seem to recall that they backed off on that one, but it could come back. If I recall the minimum SAAMI for a 308 is actually .3425, so you run less at your own peril if you plan to shoot the Canadian Nationals or the Worlds.

Smaller than that I believe. If I've read the SAAMI chamber drawing correctly, it's a nominal 0.3462" with 0.002" tolerance allowed making it 0.344". That's what I believe our gunsmiths in the UK work to with FTR rifles. The GB F-Class Association has raised the 'threat' on occasions that the top shooters in our GBFCA league rounds will have their chambers tested with a minimum SAAMI spec 'gauge' and those where it doesn't fit will be DQ'd.

On the wider issue, I'd never run an FTR rifle with 0.002" total clearance (ie a single thou' at any point). This isn't benchrest where rifles are cleaned between relays involving a few shots, and we shoot in the open on dusty or otherwise fouled firing points (sheep dung amongst other things), moreover in a country where it rains (a LOT!). Excessive pressures and blown primers with water getting in the chamber is a big enough problem with sensible clearances and anybody running 2 thou' is really asking for big problems.

 

[kyreloader]

I shoot a .311 loaded round in a .315 chamber in my .284 Win.

Yes, mine will shoot 0.3 MOA at 100 yards.

 

[Rtheurer]

Dusty, Keith, Russell,Scott Laurie
Thank you. Was having a discussion with a Gentleman the other day who seems to be stuck in 1990 land and refuses to believe that more than .002 will get you a quality shooting rifle that shoots less than .4's or .3's. I doubt I will change his mind but this trend of larger neck Clearance has proven itself over and over. Seems even the Benchrest crowd has been proving it some as well.

Again Thank you.