VarTarg neck size help

[mefizto]

Greetings all,

I am getting ready to order a VarTarg reamer, and there appear to be a lot of contradictory opinions regarding the neck size and free bore. So, to get some more (confusing) information, the following is my reasoning and question.

I have measured several Lapua .221 FB cases and the outside neck diameter is rather consistent at 0.248 inch. Therefore, if the case is resized to 0.20 inch , the outside neck diameter will be 0.228 inch. Since some opine that 0.004 inch tolerance is acceptable, that would translate to a 0.232 inch neck chamber. Yet, some of the recommendations are for 0.234-0235 inch chamber.

The only explanation I can think of is to ensure tolerance for a different lot. However, this pre-supposes that the lot will have thicker brass.

To add to the confusion, JGS sent me a drawing that shows the neck size 0.224 inch.

Regarding the free-bore, the general consensus for 32-35 gr bullets is zero free-bore, there does not appear to be any consensus regarding 40 gr bullets.

Could you please clarify?

Kindest regards,

M

 

[Evan]

So what I have photographed here is a Lapua 221 and one of my sized Lapua 20 Vartargs:

On the out-of-the-box Lapua 221, I have an OD of 0.248, just like you measured, and an ID of 0.220. If I seat a 0.224 bullet in this case, it will have 0.004 neck tension and end up at a loaded OD of 0.252

My Lapua 20 Vartarg has an OD of 0.2305 and an ID of 0.202. If I seat a 0.204 bullet in this case, it will have 0.002 neck tension and end up at a loaded OD of 0.2325. In a 0.234 neck chamber, this is only 0.0015" of clearance: pretty tight! That's why I skim down the necks to get a little more clearance.

EDIT: a 0.224" chamber neck means a 0.222" loaded round max and 0.009" neck thickness per side. That's turning them thin. Like tight-neck PPC thin.

And here's a 40vmax seated to touch in my 0.040 freebore chamber: http://forum.accurateshooter.com/threads/my-20-vartarg-custom.3969176/page-3#post-37447997

 

[JSH]

Unless you have a surplus of Lapua brass I would check some of the 221 brass made from 223 for neck thickness. I see little 221 brass, let alone Lapua.

 

[linebaugh]

Unless you have a surplus of Lapua brass I would check some of the 221 brass made from 223 for neck thickness. I see little 221 brass, let alone Lapua.

You mean it's not available? Better look again as a quick serch netted me both remmy and lapua in stock.

 

[Rick in Oregon]

Nosler usually has a good stock of 221FB brass also. They now produce all their own brass right here at their factory. I much prefer Lapua for my 221-based rifles, but the Nosler stuff is far superior to R-P in terms of dimensional consistency.

 

[mefizto]

Hi Evan,

thank you for the reply. I understand that I have to add 0.004 inch to my dimensions. That is part of my confusion, because some prints I found specify the neck at 0.232 inch, and look at the one I received from JGS.

I could understand the 0.232, as it may account for different brand of cases, but (1) I found several references, which claim that there is no problem with Lapua brass (without a need to turn necks) and (2) what about the JGS drawing?

I think that I will try to post WTB add for a reamer with 0.234 neck, or perhaps a rent one, that way I will minimize the potential cost of an error.

Kindest regards,

M

 

[JohnHenry]

One will introduce an error when one measures the neck ID(curved surface) using the straight edge of a caliper. You will get a low reading. One needs a ball micrometer to measure neck wall thickness. One can obviously also determine the neck wall thickness by measuring the bullet diameter(at the pressure ring on a flat base bullet) and the outside neck diameter of the case with the bullet seated.
I would suggest a .234-.235 diameter neck chamber for a no turn 20VT chamber using Lapua 221FB brass. See attached link.

http://www.saubier.com/forum/showthread.php?t=28593

 

[mefizto]

Hi JohnHenry,

thank you for the reply. Your later suggestion is exactly what I did for the FB case. I then re-calculated for the VarTarg, hence my confusion how can some report no problem with 0.232 inch chamber.

Thank you for the link, I now have the false impression that I start to understand. ;-)

Kindest regards,

M

 

[Evan]

Hi Evan,

thank you for the reply. I understand that I have to add 0.004 inch to my dimensions. That is part of my confusion, because some prints I found specify the neck at 0.232 inch, and look at the one I received from JGS.

I could understand the 0.232, as it may account for different brand of cases, but (1) I found several references, which claim that there is no problem with Lapua brass (without a need to turn necks) and (2) what about the JGS drawing?

I think that I will try to post WTB add for a reamer with 0.234 neck, or perhaps a rent one, that way I will minimize the potential cost of an error.

Kindest regards,

M

Adding 0.004" isn't a necessity. That's just a general suggestion. For example, there was a lot of 6 PPC benchrest shooters who liked to run 0.002" clearance. The risk there is that if you get carbon build up or other contamination in the chamber neck, the resulting tight fit could prevent the brass from expanding to fully release the bullet, causing your pressures to skyrocket.

That reamer print JGS sent you with a 0.224 neck is pretty wild. That's for someone who wants to turn their necks thin. You wouldn't even get the bolt to start closing on an unturned round.

A 0.232 neck you keep hearing about is what Todd Kindler originally specified, if I recall correctly, and that was meant for turning the necks just a little to clean them up with Remington 221 brass. It's a fine way to go if you want to turn your necks, regardless of what brand brass you use. You'd then just need to turn your brass until a loaded round has an OD of less than 0.228 (if you want 0.004 of clearance). If you're looking for a safe, no-turn neck, then 0.232 is really too small. You need to have a chamber neck of 0.234 or more.

I know this is all a bit intimidating and the investment in a reamer makes it all a bit nerve racking but I was very happy with my result and glad I took that leap of faith. If you stick with normal, well known dimensions, then it will be easier to sell the reamer down the road if you don't like it or grow tired of it.

For a reamer rental, are you aware of these guys: https://4drentals.com/product/20-vartarg-lap/ I'm not sure what the specs on that reamer are, but they were very helpful and responsive when I was looking for a 22BR reamer. You could reach out to them and ask.

I used the cheap $50 Hornady 20 Vartarg die set to size my brass the first time and seat bullets to get some measurements (https://www.midsouthshooterssupply....ries-iv-speciality-2-die-set-with-zip-spindle). That may be a good investment right now so that you can size your brass and measure it to feel more comfortable about what your reamer needs to be.

 

[mefizto]

Hi Evan,

thank you, for the explanation, it all starts to make sense.

You are correct that ordering a reamer is nerve wrecking. I called JGS asking to speak with a technical personnel, but the secretary said that she would send me a print and if I do not like it to change the dimensions and they will re-draw it and make it. She found the one I posted; thus they appear not to have yours on file. Of course, any change will make it a new item with the maximum charge. That is not very accommodating, is it?

I am more and more inclined to try and buy, rent, borrow, or steal a used one. I have an excellent smith (a retired aerospace machinist), who produces amazingly shooting rifles, so he will be able to determine the condition of the reamer and, more importantly, not destroy it. I still have time as my barrel will not arrive for about 2-3 months.

Kindest regards,

M

 

[Tom Blue]

I have used, and own, a PT&G finish reamer. The neck on this one is .233, but I do not use Lapua brass for Vartarg or Fireball, I use Norma.
I find I end up with .230/231 necks and I do not turn necks.