Peterson > Lapua... Bigger donuts

[Phys86]

I just started testing some Lapua 284 brass in my 30-284ai and have found that the neck diameter is much larger near the shoulder junction after sizing. I initially used Peterson 284 and didn't see hardly any variation in sized and loaded neck diameter through the whole neck length, even with 10-11x fired brass. I'm wondering what the cause of this is.

I necked up then fireformed my Lapua with a medium load behind 175smk. Then used 14 pieces to find pressure with this lot of powder. Upon resizing some of those 14 pieces, I found that one case neck near the shoulder measures 0.345 where it should measure 0.3365! It chambers but with resistance. Sharpied the neck and it looks like it hits at the shoulder junction, not the neck ....

The sizing is a FL die, expander removed, shoulder bumped 0.002. then used a mandrel to expand the neck.

If I use the expander ball in the FL die, it's not as large a difference in neck diameter, but it's still there.

I never had this issue with Peterson. I don't want to have to neck turn (chamber neck is a parallel 0.3425) or have the chamber neck opened near the shoulder.

Thoughts?

 

[Phys86]

I found some interesting things last night in sizing cases and taking measurements and trying them in the chamber after sizing. It's hard to explain without pictures, but I'll try.

My first post explaining the sizing method is a bit contradictory with the information below. The initial sizing/measuring in the first post was with just a couple cases. After investigating more last night, I think the information below is what is actually going on.

Using my Hornady case comparator, I shoot for a sized measurement of 1.809. this gives 0.003 shoulder setback for my chamber.

When sizing with the expander ball in the die, the neck diameter near the shoulder junction is increased quite a bit and I'd get stiff chambering even when the comparator showed 1.809. I pulled the expander ball and sized a case which came out to 1.807 or so with a uniform neck diameter across the whole neck. That case chambered freely. So I thought maybe the expander ball was screwing things up when pulling it back through the smaller neck.

I adjusted the die without the expander ball installed to give 1.808 or 1.809 and sized a few cases.

I then took my Lyman M neck expander die and expanded the necks on those after using the FL die without expander ball. The comparator measurement grew to 1.809-1.810 and also increased the neck diameter near the neck junction a bit!! These cases chambered pretty freely for the most part.

So what I found was that for some reason, even when using the Lyman M expander separately, is that the shoulder is being moved upward (or lengthening?) to some degree when expanding the neck, which happens to a greater degree when using the expander ball. It seems that the shoulder might be moving more closer to the neck in comparison to where my comparator tool hits the shoulder.

I have no idea why this happens, but I don't like it. It never happened that I'm aware of with Peterson brass. It could be the fireforming process pushing more of the shoulder material into the neck and junction area than what happened with the Peterson. I'm not sure if it's a function of the brass or if it's due to my fireforming. I did have some wonky cases that didn't chamber with resistance like they should when fireforming, so it is either that or the brass itself.

This is a strange issue

 

[Phys86]

I'm curious what you more experienced guys thoughts are here and what a good solution is.

Is this THE donut issue and why am I seeing it right after fire forming?

Why do I see it with Lapua when I have Peterson on it's 11th firing and there is zero indication of a donut being present?

If it is the donut issue, what is the cheapest solution (I'm on a seriously tight budget)? Outside neck turning into shoulder after expanding mandrel? Convert my FL size die into a bushing die and don't use a mandrel so that the donut stays inside? I've got my cases chambering without resistance, but my neck diameter measurements near the shoulder junction indicate there is very little clearance that I'm not very comfortable with since it's a hunting rifle. Chamber neck should be 0.3425 and my case is measuring around there or a touch larger. However, it shouldn't cause pressure issues because I'm seating the bullet well ahead of the donut portion.

 

[gunsandgunsmithing]

Likely has something to do with brass thickness in the shoulder. When you neck up, you're using part of the shoulder to form the neck. Peterson may be using thinner brass in the shoulder area. Ultimately, donuts are overhyped. Just make sure the bullet bearing surface doesn't get seated into that area and rock on.

 

[Coyotefurharvester]

You said this is a hunting rifle and brass at 0.345 has some bolt resistance. I don't want bolt resistance on hunting rounds. And the 0.003 neck clearance you are used to seeing is Ok, I would want the Lapua brass fitting the same. It should only take on time turn to get rid of the donut.

 

[David Christian]

Here is an inexpensive cure to your donuts. Lapua brass when necked up is known to produce donuts. After firing run an internal reamer to cut them out. I too use an expander mandrel post sizing. Even if your bullets are not seated deep, the extra material at the neck/shoulder junction messes with your seating die as well as chambering. Cut them out.

 

[Sandstorm]

David ...How are you turning the reamer. In a lathe.?

 

[David Christian]

David ...How are you turning the reamer. In a lathe.?

Hand drill starting with an undersized reamer then working up in diameter to where I am only cutting the donut and not the insides of the neck.

 

[Phys86]

Likely has something to do with brass thickness in the shoulder. When you neck up, you're using part of the shoulder to form the neck. Peterson may be using thinner brass in the shoulder area. Ultimately, donuts are overhyped. Just make sure the bullet bearing surface doesn't get seated into that area and rock on.

Thanks. I'm guessing that's the case and have been considering cutting a couple virgin cases open to look.

Even on the virgin brass prior to fireforming, the neck is thickened considerably near the shoulder just from necking up. Below, it measures 0.340 at that point and should be 0.338

 

[Phys86]

You said this is a hunting rifle and brass at 0.345 has some bolt resistance. I don't want bolt resistance on hunting rounds. And the 0.003 neck clearance you are used to seeing is Ok, I would want the Lapua brass fitting the same. It should only take on time turn to get rid of the donut.

Agreed. I usually have 0.004+ clearance. 0.338 loaded neck diameter and 0.342+ chamber. I've got the sizing operation figured to where I can chamber them without resistance, but I'm fairly certain that it needs to be dealt with by turning.

I don't have any turning tools and had hoped to avoid it. I'm now kind of looking at the pma model B or the cheapest k&m setup possible.


FF case, measures 0.340 here and 0.338 closer to mouth


0.342+ here

 

[Phys86]

Here is an inexpensive cure to your donuts. Lapua brass when necked up is known to produce donuts. After firing run an internal reamer to cut them out. I too use an expander mandrel post sizing. Even if your bullets are not seated deep, the extra material at the neck/shoulder junction messes with your seating die as well as chambering. Cut them out.

Thanks! In my searches, I found another thread mentioning those. So you just use several and increase incrementally until you've only cut out the donut?

How long does it take to come back?

 

[searcher]

I just started testing some Lapua 284 brass in my 30-284ai and have found that the neck diameter is much larger near the shoulder junction after sizing. I initially used Peterson 284 and didn't see hardly any variation in sized and loaded neck diameter through the whole neck length, even with 10-11x fired brass. I'm wondering what the cause of this is.

I necked up then fireformed my Lapua with a medium load behind 175smk. Then used 14 pieces to find pressure with this lot of powder. Upon resizing some of those 14 pieces, I found that one case neck near the shoulder measures 0.345 where it should measure 0.3365! It chambers but with resistance. Sharpied the neck and it looks like it hits at the shoulder junction, not the neck ....

The sizing is a FL die, expander removed, shoulder bumped 0.002. then used a mandrel to expand the neck.

If I use the expander ball in the FL die, it's not as large a difference in neck diameter, but it's still there.

I never had this issue with Peterson. I don't want to have to neck turn (chamber neck is a parallel 0.3425) or have the chamber neck opened near the shoulder.

Thoughts?

If your brass trimmer (like a Wilson) will allow the use of a reamer, you can take out the doughnut from the inside. Short of turning necks - that is the only way I know of getting rid of those doughnuts.

 

[gunsandgunsmithing]

Worst case, turn the necks. Best case, the bullet doesn't seat into it and it won't hurt a thing. I don't understand why everybody gets so worked up over donuts. IME, if the bullet is seated above it, fuggitaboutit

 

[Eagle Six]

I may be talking out of turn as I have no experience with the 30-284AI. If it were me I would probably use the mandrel I have and then outside neck turn to skim the neck up to the shoulder junction. I don't turn neck anymore but I do have an old Forster neck turner in the tool cabinet and a used one, or something similar might fit a tight budget. I would think that OD turning would be easier to see and measure the results and be more uniform than a hand drill cutting the inside. Just my thoughts.

 

[Phys86]

Worst case, turn the necks. Best case, the bullet doesn't seat into it and it won't hurt a thing. I don't understand why everybody gets so worked up over donuts. IME, if the bullet is seated above it, fuggitaboutit

I'm only concerned because i only have a regular FL die and when expanding the neck it pushes it all to the outside, causing very minimal clearance near the shoulder junction in the chamber and it's also making my shoulder bump numbers screwy.

If I had a bushing die without using an expander and the donut was left inside, then I wouldn't worry about it at all! I seat my bullet well ahead of that point

 

[David Christian]

Worst case, turn the necks. Best case, the bullet doesn't seat into it and it won't hurt a thing. I don't understand why everybody gets so worked up over donuts. IME, if the bullet is seated above it, fuggitaboutit

This is the second part of what I said above:

“I too use an expander mandrel post sizing. Even if your bullets are not seated deep, the extra material at the neck/shoulder junction messes with your seating die as well as chambering.”

A case with a large enough donut that is run through an expander mandrel post sizing essentially reduces/eliminates your neck clearance.

 

[Tesoro]

Bite the bullet and get yourself a K&M carbide with the power grip and ergo handle. Contrary to prevailing consensus, neck turning is good therapy, has added benefit of evening up neck tension on all your cases as well as fixing your current issue! Add a weak hand drill, which you can control speed easily with, and an optivisor. The above applies only if you are not shooting thousands of rounds and your life is dictated by an activity planner.

 

[gunsandgunsmithing]

This is the second part of what I said above:

“I too use an expander mandrel post sizing. Even if your bullets are not seated deep, the extra material at the neck/shoulder junction messes with your seating die as well as chambering.”

A case with a large enough donut that is run through an expander mandrel post sizing essentially reduces/eliminates your neck clearance.

I see. I'm not a mandrel guy but I can see how it would be an issue in your situation. You may be able to set the mandrel die to stop before it pushes the donut back out but, not having done it, I'm not sure how critical or how it would work in that regard. Sounds like Peterson is your answer unless you wanna change or add something to your process. To me, I build rifles around brass and it has never been around Peterson, although, I'd love for it to become a better brass option, being American made. If it works that's great but until things get worse than they already are, I'll stick with Lapua and do what I need to to make it work. Not telling you what to do but the value I put on Lapua brass is up there, where I'll decide on cartridges and processes based around it. The 30 might be different but other 284 based wildcats have traditionally suffered from brass issues related to pressure when pushed hard. I'd lean heavily toward whatever the best and toughest parent brass is for the chambering, right or wrong. If you're not gonna step on the gas hard, you may well get by with something else but to date, I've not found anything that holds pressure and is otherwise very good..as Lapua. The "easy button" is drop the mandrel step but if you feel it matters on target, I would keep doing it, too.

If as I suspected previously and it's from thicker shoulder brass, I don't see another solution. It just is what it is, sounds like. Neck turning isn't terrible and could do away with your mandrel op and fix the issue at the same time. Like you though, I prefer not to need to neck turn.

Curious what you decide. Keep us posted on what you find or do. Sorry, most of this was directed to the op but I hear you too. Decisions, decisions. Lol!

 

[gunsandgunsmithing]

I'm only concerned because i only have a regular FL die and when expanding the neck it pushes it all to the outside, causing very minimal clearance near the shoulder junction in the chamber and it's also making my shoulder bump numbers screwy.

If I had a bushing die without using an expander and the donut was left inside, then I wouldn't worry about it at all! I seat my bullet well ahead of that point

I would not worry about clearance strictly due to the donut as long as the bullet is seated above it AND it doesn't cause other problems as you mentioned. I don't have any good answers but see my post above to David. I'd go a fair distance to stay with Lapua if it were mine, but it's not, so...

 

[Phys86]

I appreciate all the input.

I do like the Peterson brass I'd been using. The only problem was that I ended up with the clicker issue even though i designed the chamber reamer and resize reamer to avoid it. It is likely due to pushing limits to hard and my die not being the best. The intent with Lapua was to see if this resolved the issue or not. If I continue to see a clicker issue with Lapua, I'll just go back to Peterson due to availability, being US made, and that I likely can't shoot the difference! I have been looking at Cortina's 284 expander die. I may be able to use it similarly to a small base die and prevent clickers with Peterson. However... Maybe I'd end up with a Peterson donut to deal with eventually.

There's lots of options and ways to skin this wildcat.

Before spending any money, I'm going to see if I can get my mandrel set up to allow me to leave the donuts inside and I'll just seat above them. If that does work, I'll continue with that until I see a problem or aquire the funds to get a better fix in place.

I'll report back