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Hi all,
I have S-type match dies for my 6.5-284. I ran a bushing in the sizing die and all cases were neck turned for a tight chamber.
I had the chamber re-cut for a standard neck.
Question I have, do I need to run a bushing in my sizing die?
I have loaded some rounds without and hasn’t been a problem, however, it doesn’t stack up in my mind sizing without a bushing.
Thanks for any feedback
You cannot neck size without a bushing. Type-S need one or its just a huge hole. I suspect you have loaded your old tight neck brass and have minimal neck tension now.
If your chamber was tight, then opened up, the bushing you had will still give the same neck tension if you're using the same brass. The variable changed was the chamber not the components.
Do you know how to measure neck tension? Try that first and should point you in the right direction.
Yes I believe so, although your new loaded neck diameter will more than likely need a new bushing size?
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No, not this - not the bit about needing a different size of bushing. As James has said, if you are using the same neck-turned brass, then all that will be happening in the new chamber is that the necks will be expanding to a larger diameter on firing. If it is the same brass, and so the neck thickness remains unchanged, then the same bushing will give the same neck tension as before.Quote:
Originally Posted by Gerardo
What may be affected is the ability of that same bushing to size the (future) larger neck diameter of the the fired cases back down in one neck sizing step with the same degree of concentricity as was being achieved before, as from this point onwards the bushing will have more work to do on the cases fired in the new chamber. It may well be fine, but that is something you may want to check with a concentricity gauge on either the sized necks, or perhaps on the bullets in the finished loaded rounds, if such things are important to you.
As far as fitting or not fitting a bushing - yes - the bushing has to be fitted. Once you've fired the brass in the new chamber it will become quite apparent why it is required. Again as James has written above, on the existing cases you have from out of the previous chamber, a very tight neck can leave fired cases with a degree of residual neck tension from spring-back in the brass.
Awesome advice thanks,
I am not using the old neck turned brass.
Thinking back, I loaded 100 rounds all from new Lapua brass, shot extremely well, 0.6moa.
I best go pull my dies out and I think the neck diameter has been stamped on the barrel
I will report back
So…..
I have opened the die and you can see the sizing is from the bottom of the neck down. That said the neck has to pass through top of the shoulder in the die so likely some sizing occurs.
My bushing is .291 and the new chamber is .298
Would it be correct in saying that I should be running a .296 bushing?
Just measure the OD of a fired case neck and subtract 0.002" and that should be your bushing size, or very close to.
So what you're saying is you loaded up using new brass. This brass is yet to be sized?
If you still have any rounds loaded measure the outside diameter of the neck. Measure in two places 12 o'clock to 6 o'clock and 3 o'clock to nine o'clock. If your brass is good quality you should get close to the same readings. Average the measurements. I usually deduct 2 thou to determine the bushing size.
With springback that usually gives around 1.5 neck tension. As the brass hardens and if you don't anneal the springback and neck tension will change. You either anneal or select a different bushing.
A lot of gunsmiths only stamp the neck dimension on the barrel if it is a tight neck. Yours may be different and the smith may have stamped the std neck dimension.
Edit: I see you have posted 298.
I'd like this but my like button has gone awol.Quote:
Originally Posted by 38 South
No, in the instance there is no relationship between the brass and the chamber other than one sits in the other. You need to either know the wall thickness atvthe neck and the projectile OD, or the easier method is measure the neck of a loaded round as this will be the sum of the two. Measure 5-10 off them and take the average. This is your loaded neck OD. For the brass to grip the projectile you need neck tension. Essentially it is an interference fit between the case neck and the projectile. I would sugest anything from 2-4 thou for a hunting rifle, and maybe 1-2 for a target rifle. I don't know what a 6.5 is going to measure but an example may be if a loaded round measured 0.295" and you wanted 2 thou tension your bushing would be 0.293". Expect about 1/2 thou spring in the brass so really a 0.293" bush may give closer to 0.2935" or only 1-1/2 thou neck tension.Quote:
Originally Posted by Stag
Makes sense thanks. My calipers are shit so wouldn’t be confident in the measurement that fine. I will get something sorted so I can solve this problem with confidence.Quote:
Originally Posted by kiwijames
Thanks
There are some recorded measurements for the 6.5-284 Lapua brass neck thickness on the usual forums that a search should turn up if you go looking.
0.015" appears to be the figure to expect, your loaded rounds will then measure close to 0.294",
being 0.015" + 0.264" + 0.015", as measured in the way both Zimmer and KiwiJames describe in posts #9 and #11 respectively.
Your starting point for a bushing would then be 0.292", being 0.002" under the loaded round diameter of 0.294".
This is exactly the same selection criteria as Zimmer and KiwiJames have provided above with the difference being that in James's post he has taken the neck wall thickness to be 0.0155" giving a loaded round diameter of 0.295", so his bushing selection was 0.002" under that.
Hopefully that makes sense?
Your 0.298" chamber diameter across the neck indicates that (if the brass thickness is indeed 0.015" per side) that you have four-thousanths of an inch total clearance for the brass at the neck to expand into on firing to release the bullet, or 0.002" all the way around the diameter between neck and chamber wall. That is generally considered to be a "no turn" chambering; as implied - sufficient clearance to use the brass without needing to worry about turning.
The die does not size the neck if there is no bushing in place. While the hole at the top might look narrow there will be clearance to allow the necks to pass through untouched. Actually there is a small region of the case - right at the shoulder-neck junction that neither the die or the bushing contacts, even when the bushing is screwed right down, and it shouldn't be screwed hard down but backed off a fraction of a turn so that the bushing can "float" - rattle around sideways when you shake the die. I think this is all laid out in the set-up instructions for the dies if you have them?
@Stag your current 291 bushing will be fine with unturned Lapua brass, giving you probably 3-4” neck tension on the pill.
As an aside. It's quite interesting to note how stable even 2thou of neck tension is. My pills feel as if they are made of butter when seating and I'd always wondered if they are not going to slip out or go out of true. So far, so good in a purely hunting rifle setup.
Neck tension is yet another reloading rabbit hole to fall down I have chosen to steer well clear of. When shit works I try not to mess with it any further.
0.002" is generally sufficient, it's an interference fit, even a size for size fit requires force to assemble/disassemble, this is true of any size for size fit.
I bought a chino made ball-mic (locally) and with a tiny bit of adjustment with the tool that came with it, does a good job. Much better than stuffing about digital calipers for a radial thickness.Quote:
Originally Posted by Stag
Thanks for all the feedback, really interesting.
I will try my .291 bushing and if I experience any accuracy issues I will try reducing the tension with a larger bushing.
My experience is somewhat limited and relied on the support of a local gunsmith/BR shooter to help me.
I have just ordered a forster press and mitutoyo calipers so looking forward to making this a staple evening activity.