30 BR no turn neck?

[flatbase]

I'm in process of building a 30BR but am considering a no turn neck. I have 6mm BR Lapua brass to neck up. I know I might run into trouble if the neck thickness varies so I will check that before I proceed.

I estimate the brass will have a neck OD of 0.331" so chamber neck would be ~0.334?

I would like to hear if there is experience with this no turn neck approach.

thanks,
flatbase

 

[AlNyhus]

For those wishing to do a 'no turn' 30BR or a 30BR with a chamber neck diameter of larger than .330, here's how to 'end run' the problem of the bulge at the neck/shoulder junction that happens when you neck up from 6mm to .30:

Simply load the 6BR cases with a top end load of H322, seat whatever extra 6mm bullets you have laying around...and fire 'em in the 30BR chamber. The 6mm bullets rattle down the bore and go everywhere but straight when they exit...so make sure you do this in a safe place at the range..like into a dirt berm behind a handgun area, etc.

The necks blow out to the chamber's neck dimension and will be perfectly concentric with the case body. The bulge from this type of 'necking up' approach will be on the inside, but you can take care of this with a number of tools...the Wilson inside neck cutter, K&M's donut remover, or a simple straight fluted chucking reamer from MSC, etc.

The one thing to be careful about if you do it this way,not neck turning) is when you remove the inside neck donut...take care that the cutter does not touch the inside of the case neck anywhere but where the donut is. An oversize cutter that takes brass out of the entire neck length will cause all sorts of concentricity issues..as the outside of the neck will not be parallel with the inside of the neck. Obviously, the donut removal is done on fired cases that haven't been neck sized.

The best way to find out what size cutter you need is to check the neck i.d. with a pin guage after fireforming.

All in all, though..it's a lot of work when you consider that you can also simply neck up, outside neck turn and be done.

Not sure why you want a 'no turn' 30BR...can you explain your reasoning a bit more?

Thanks! -Al

 

[AlNyhus]

Should also add that anyone wanting to blow the necks out on a 30BR can do so w/o a bullet by using Unique and a bunch of Kleenex stuffed on top of it to hold it in the case. Have done this both with and w/o a wax 'plug' on the case neck..both ways work fine. -Al

 

[EdwinD]

Al,

I do NOT like turning brass!

Therefore that is why I want a "no neck turn " chamber.

 

[flatbase]

thanks for the replies

The main reason I'm contemplating a no-turn neck is that it seems to becoming popular and successful in other calibers such as 6BR and 6.5x47Lapua assuming high quality brass. But I haven't seen any comments about 30BR. Is it less forgiving since the 112 & 118 gr bullets are stubby compared to heavier 6mm bullets? Do you figure accuracy is less overall in general with no turn because one is giving up a little precision? The goal is less homework, less equipment to buy, and more range time.

As far as fireforming I think the range officer will be happier if I use Cream of Wheat. Too many houses close by.

Understand an outside donut would have to be trimmed. Inside donut doesn't seem as serious unless the bullet runs into it when seating. If the shoulder was pushed forward a tenth? would that take care of bullet seating problem?

Gunamonth, What kind of groups are you getting? And what cases are you using? Seems like a lot of variation. Can necking up introduce this much distortion?

thanks,
flatbase

 

[AlNyhus]

It's one thing to use a 'no turn' neck chamber in a 6BR....the inside of the neck is parallel with the outside of the neck....because the neck has always been the neck, not part of the shoulder. Given decent neck runout, accuracy will be great as we've seen with the 'no turn' 6BR's and some of the other experiments being done with the 220R case and it's variants.

But when you start expanding and stretching a .243 neck .065 thou.,.0325 per side) to .30, it's a whole different ballgame. Part of the material that was the shoulder now becomes the neck, hence the bulge at the neck/shoulder junction of a freshly necked up 30BR case that hasn't been neck turned.

So, you can turn off the bulge on the outside or fireform the cases and cut it off on the inside. But one way or another, it has to come off. I don't feel there's a really a performance disadvantage to leaving the donut in the base of the neck, provided the base of the bullet doesn't contact the donut. But here's the thing..it's a big donut and it doesn't exactly start and stop at a well defined specific place inside the neck. The internal donut imparts a considerable amount of stress on the case...hoop stress, in engineering terms. This stress, if left in there, will negatively effect how your sizing operation works...this stress makes the part of the shoulder that is now part of the neck want to get back to where it originally was. The 'springback' from this will be much more than the material around it...when you size the neck, this bottom part of the neck will come back more than the top part, for example. This thicker area of the neck bottom will also resist this area of the shoulder being 'bumped back' and want to return to it's previous dimension...thats why blending the cut from the base of the neck into the shoulder is so important in any outside neck turning operation..but doubly so in the case of the 30BR.

There's a lot more to this than meets the eye. That's why for most people, simple outside neck turning does away with 90% of the problems associated with this amount of necking up with this specific case,Lapua 6BR).

Regardless of how you choose to approach it..and no matter if you end up with a .330 chamber neck or a .334... the inside of the case necks must be on the same plane,parallel) as the outside of the necks or accuracy will suffer.

To take it a bit further, you can have great indicated runout of the necks o.d., but if the bullet runout is bad because the neck i.d. isn't 'on plane' with the neck o.d., you're not going to get all the 'goody' out of it.

I know that I've changed how I make up my 30BR cases over the past several seasons. It's been for the better, even though it involves more work than a simple 'neck it up and turn it off' approach.

Probably starting to get off topic a bit, so I'll stop here. Like everything, there's a lot of ways to acomplish the same result. :thumb:

Good shootin'.

 

[rayjay]

I think Ron Hoehn and others supply preturned brass. Simple and cheap when you count the cost of neck turning tools.

 

[flatbase]

Thanks for the explanation. I've learned a lot.

I've seen elsewhere where you have built up 30 cal cartridges with very short necks. While neck turning those did you have a donut to clean up? Do you get a thickening,donut) at the new shoulder neck junction because in effect you're bending the metal at that point?

Flatbase

 

[AlNyhus]

I've seen elsewhere where you have built up 30 cal cartridges with very short necks. While neck turning those did you have a donut to clean up? Do you get a thickening,donut) at the new shoulder neck junction because in effect you're bending the metal at that point?

flatbase: The short neck .30,the WolfPup) is basically a 30BR with the shoulder blown foward .240. It ends up with a neck that's .085 long. When turning the necks for this case, I turn them back .150. When the shoulder blows foward during fireforming, the lower .075 of neck becomes the upper portion of the shoulder. Since this part of the shoulder is the same thickness as the neck, donuts aren't a problem. Just finished my second full season of competition with this chamber in my HBR gun...still using the original 50 cases. Here's a pic of the case making process to better illustrate....it's not the greatest photo, but should get the idea across. Notice on the second case from the left..even with this bad photo you can clearly see the 'bulge' at the base of the neck on the necked up 6BR case. On the fireformed and loaded round,far right) you can just make out a faint line on the upper part of the shoulder that was the lower portion of the turned neck before the shoulder was blown foward.

Good shootin'. -Al

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