Blown out primers and pressure signs

[DaveTooley]

There's only a couple of tenths difference in the numbers.

 

[dellet]

I'm not saying it would cause problems. I am saying it might make it so the go/no go gauges aren't interchangeable.

Take a look at the below CIP specs for the cartridge and note that there is no base to datum number defined. You have to use shoulder to body and shoulder to neck measurements.

The SAMMI drawing posted earlier also have metric measurements.

The differences are in the .01’s of millimeters, .010 millimeter = .0004”. Not many people have the tools need to find that difference, temperature variation in the tools and measured item will throw the measurement off that much.

 

[precision1]

Has anyone actually had these pressure signs/problems from seating into donuts?

Or does it just cause erratic es/sd? From slightly raised pressure?

Blown primers and smeared brass rims?IDK just don't seem right

Generally in my experience donuts cause poor es/sd no pressure signs...but I'm far from expert for seating into donuts and somehow what little I've noticed doesn't cause me problems

 

[precision1]

Assuming your using bushing die since your talking about donuts.

If your going to try everything how about buying a super cheap lee collet die.it irons out donuts and is cheap

 

[mikehill85]

FYI,

I shot 35 more rounds today. I chose brass that didn't have any donuts and I didn't run into any pressure issues despite going to max load. It is looking more and more like the donuts were the problem.

 

[mikehill85]

Has anyone actually had these pressure signs/problems from seating into donuts?

Or does it just cause erratic es/sd? From slightly raised pressure?

Blown primers and smeared brass rims?IDK just don't seem right

Generally in my experience donuts cause poor es/sd no pressure signs...but I'm far from expert for seating into donuts and somehow what little I've noticed doesn't cause me problems

I checked my fired brass from yesterday. There are now 3 new pieces of brass which I can't push the bullets into even though I haven't resized them. The bullets are getting stopped at the neck shoulder junction.

I am actually a LEE full length sizing die. It uses an expander ball. I've read some say that this type of die doesn't create donuts but if a thick area of brass at the neck shoulder junction isn't a donut, then I don't know what is.

I'm not sure how the donuts are forming. Maybe I am not lubing inside the case neck enough and the expander ball is pulling material up into the neck? Can they form during the firing process?

I have been looking at options to get rid of them but most seem to involve dropping a few hundred dollars on a system to trim brass/ream the inside of the necks.

 

[DaveTooley]

I use chucking reamers about .001" to .002" over bullet diameter. Run them in a drill and slide the case onto the reamer prior to sizing. Makes quick work out it. Rock River Tool has them in .0005" increments.

2400-D - Rock River Tool, Inc.

www.rockrivertool.com

 

[243winxb]

have been looking at options to get rid of them (donuts)

1. Outside neck turning. OR
2. Bushing die & dont size the neck all the way to the shoulder.

Turning is best. The bushing cant fix thick neck walls or tight neck chambers.

When a bullet will not drop into a fired piece of brass, it can be from low pressure and/or slow burn rate powders. Brass may need annealed.

 

[dellet]

Donuts form a couple ways. Under firing pressure the case stretches lengthwise and since the walls of the case are tapered, thicker brass moves forward, what was the shoulder becomes the neck.

In your case, with a short chamber, you have to push the shoulder back farther than normal, forcing a portion of the shoulder into the neck which has thicker brass.

Normally you would expect enough thinner brass in the shoulder that this would not be a problem until after multiple firings, but here you are.

The only correction is to remove metal. You can remove it from the case to fit the chamber, or you can remove it from the chamber to fit the case. Third option is fire the bras until the donut develops and then throw it away, I guess there is a fourth option of shooting shorter and shorter bullets to stay ahead of the donut.

Back to the SAAMI drawing, note the chamber dimensions of the neck. There is a slight taper with the junction of shoulder to neck having the larger diameter.

A different manufacturer, headstamp with different brass thickness may solve your symptom, but this all goes back to a chamber too short for a go gauge.

 

[mikehill85]

FYI,
I ordered a Go-Gauge from Forster. It is a full 3 thou shorter than the Go-Gauge I originally used. The bolt closes on it no problem. So it turns out I don't have a problem with headspace being outside of SAAMI specs.

Also, whatever you do, don't order Z.P.V. Proizvodnja headspace gauges. They are garbage, apparently. That said, at least they agreed to give me a full refund and pay to have it shipped back to them.

 

[dellet]

FYI,
I ordered a Go-Gauge from Forster. It is a full 3 thou shorter than the Go-Gauge I originally used. The bolt closes on it no problem. So it turns out I don't have a problem with headspace being outside of SAAMI specs.

Also, whatever you do, don't order Z.P.V. Proizvodnja headspace gauges. They are garbage, apparently.

This more likely a problem with your comparator insert not matching the angle of the shoulder on the gauges and why I said before there are always discrepancies.

Minimum chamber base to shoulder datum is 1,541”. Your old gauge with the insert you have measured 1.540”. It was already .001” short and did not close. Now you have a new gauge that is .004” shorter than SAAMI minimum at presumably, 1.537”, And the bolt closes.

Do you see the problem there?

Your fired cases measured 1.5385” with the same tool. .0025” shorter than minimum chamber.

The next clue is developing donuts early, pushing the shoulder into the neck.

The Hornady comparator is notoriously inaccurate for reliable measurements, but you have some pretty good other indicators.

It’s back to, try different brass, start removing metal somewhere, use shorter bullets.

 

[jelenko]

new gauge that is .004” shorter than SAAMI minimum at presumably

Wait. The new gauge is from Forster - I would assume they ground it right - yes?

 

[dellet]

Wait. The new gauge is from Forster - I would assume they ground it right - yes?

You would think. That’s why I said the insert would be most suspect.

But look at the numbers, all measured with the same caliper and insert.

Original gauge 1.540”
New gauge is old gauge -.003” 1.537”
Fired brass 1.5385”

Won’t close on the original.
Closes on fired brass
Closes on new gauge.

The measurements are within margin of error using a caliper with only .0015 +/- with the new and old gauge compared to the fired brass. Almost pointless. Other than it’s pretty safe to assume the chamber is on the tight side, with minimum being 1.541”,

Here’s the kicker tho. Every hornady insert I have used, measures short because of the chamfer on the hole. This makes the angle of the measured item critical. So the fired brass most likely matches the chamber the closest.

Bottom line, who cares. But look at the other indicators. The shorter the base to shoulder length, the closer to the lands the bullet will be, given a consistent base to bullet ogive. We know there were problems there. Donuts are being formed with a single firing. Another indication of thick brass and a hot load, where does thick neck brass come from? The shoulder.

Was it possible the cartridge sticking in the chamber was hanging up on the donut instead of the bullet? Maybe.
But if seating the bullet deeper allowed it to fall out, that should have created a bigger problem at the donut by expanding that area even more. It doesn’t make sense.

Seating the bullet deeper seemed to help the pressure problem some, if it was still a problem. Changing bullets Helped more or solved the problem. But we don’t know exactly what those bullets were and the loading details. My guess is they were different enough to be below the lands, above the donut. Just a guess.

Getting actual numbers has been difficult, and when actual numbers/measurements are used, problems seem to be found. Frustrating for everyone.

And remember, we have a near max load, in brass that is sized to near or below minimum spec.

There’s a lot going on and honestly, a .003” discrepancy using a hornady insert on go gauges from two different manufacturers. Isn’t where I would focus my time. Certainly not when the fires brass comes up shorter than minimum chamber on a load that pops primers.

 

[mikehill85]

You would think. That’s why I said the insert would be most suspect.

But look at the numbers, all measured with the same caliper and insert.

Original gauge 1.540”
New gauge is old gauge -.003” 1.537”
Fired brass 1.5385”

Won’t close on the original.
Closes on fired brass
Closes on new gauge.

The measurements are within margin of error using a caliper with only .0015 +/- with the new and old gauge compared to the fired brass. Almost pointless. Other than it’s pretty safe to assume the chamber is on the tight side, with minimum being 1.541”,

Here’s the kicker tho. Every hornady insert I have used, measures short because of the chamfer on the hole. This makes the angle of the measured item critical. So the fired brass most likely matches the chamber the closest.

Bottom line, who cares. But look at the other indicators. The shorter the base to shoulder length, the closer to the lands the bullet will be, given a consistent base to bullet ogive. We know there were problems there. Donuts are being formed with a single firing. Another indication of thick brass and a hot load, where does thick neck brass come from? The shoulder.

Was it possible the cartridge sticking in the chamber was hanging up on the donut instead of the bullet? Maybe.
But if seating the bullet deeper allowed it to fall out, that should have created a bigger problem at the donut by expanding that area even more. It doesn’t make sense.

Seating the bullet deeper seemed to help the pressure problem some, if it was still a problem. Changing bullets Helped more or solved the problem. But we don’t know exactly what those bullets were and the loading details. My guess is they were different enough to be below the lands, above the donut. Just a guess.

Getting actual numbers has been difficult, and when actual numbers/measurements are used, problems seem to be found. Frustrating for everyone.

And remember, we have a near max load, in brass that is sized to near or below minimum spec.

There’s a lot going on and honestly, a .003” discrepancy using a hornady insert on go gauges from two different manufacturers. Isn’t where I would focus my time. Certainly not when the fires brass comes up shorter than minimum chamber on a load that pops primers.

First of all, thanks for all the time and thought you've put into trying to help me out. It is truly appreciated.

You said the comparator can't be relied upon for absolute dimensions, only relative dimensions. I'm not sure how we can conclude the brass is coming out shorter than the minimum chamber length when we are using a comparator that can't give us absolute dimensions and the fired brass has a headspace dimension that is larger than a go gauge from a reputable manufacturer.

The fired brass measures 1.5385". The old gauge measured 1.340". The new gauge measures 1.537". To me, it makes sense that the fired brass would be larger than the new gauge and that the old gauge (which didn't chamber) would be larger than either one. The fired brass measures between the new go gauge (which chambered) and the old gauge (which wouldn't chamber).

That being said, I agree the chamber has to be on the tight side (i.e. very close to SAAMI minimum headspace).

I'd add that my calipers are the Mitutoyo CD-6" ASX model, so they aren't junk.

Sorry for the lack of specifics on those loads. The last 4 loads (with no pressure issues) were set up as follows:

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 140 grain Berger Hybrid Target
Powder: N555
Charge: 41.4-43.4 grains (5 shots per charge in 1 grain increments...i.e. 5 rounds at 41.4 grains, 5 rounds at 42.4 grains, and 5 rounds at 43.4 grains) (Max charge is 43.4 grains)
CBTO: 2.196" (chosen to seat above the donuts but below mag length)
Velocity: Unavailable

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 140 grain Nosler RDF
Powder: N555
Charge: 40.0-42.0 grains (5 shots per charge in 1 grain increments) (Max charge is 42.0 grains)
CBTO: 2.2445" (chosen to seat above the donuts but below mag length)
Velocity: Unavailable

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 143 grain ELD-X
Powder: N555
Charge: 39.7-41.7 grains (5 shots per charge in 1 grain increments) (Max charge is 41.7 grains)
CBTO: 2.2758" (chosen to sit 20 thousandths off the lands)
Velocity: Unavailable

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 147 grain ELD-M
Powder: N555
Charge: 42 grains (3 5-shot groups) (Max charge is 42.6 grains...I only went to 42 because I shot a 0.23 MOA 5-shot group with this load last time out)
CBTO: 2.272" (chosen to sit 20 thousandths off the lands)
Velocity: Unavailable

 

[dellet]

First of all, thanks for all the time and thought you've put into trying to help me out. It is truly appreciated.

You said the comparator can't be relied upon for absolute dimensions, only relative dimensions. I'm not sure how we can conclude the brass is coming out shorter than the minimum chamber length when we are using a comparator that can't give us absolute dimensions and the fired brass has a headspace dimension that is larger than a go gauge from a reputable manufacturer.

The fired brass measures 1.5385". The old gauge measured 1.340". The new gauge measures 1.537". To me, it makes sense that the fired brass would be larger than the new gauge and that the old gauge (which didn't chamber) would be larger than either one. The fired brass measures between the new go gauge (which chambered) and the old gauge (which wouldn't chamber).

That being said, I agree the chamber has to be on the tight side (i.e. very close to SAAMI minimum headspace).

I'd add that my calipers are the Mitutoyo CD-6" ASX model, so they aren't junk.

Sorry for the lack of specifics on those loads. The last 4 loads (with no pressure issues) were set up as follows:

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 140 grain Berger Hybrid Target
Powder: N555
Charge: 41.4-43.4 grains (5 shots per charge in 1 grain increments...i.e. 5 rounds at 41.4 grains, 5 rounds at 42.4 grains, and 5 rounds at 43.4 grains) (Max charge is 43.4 grains)
CBTO: 2.196" (chosen to seat above the donuts but below mag length)
Velocity: Unavailable

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 140 grain Nosler RDF
Powder: N555
Charge: 40.0-42.0 grains (5 shots per charge in 1 grain increments) (Max charge is 42.0 grains)
CBTO: 2.2445" (chosen to seat above the donuts but below mag length)
Velocity: Unavailable

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 143 grain ELD-X
Powder: N555
Charge: 39.7-41.7 grains (5 shots per charge in 1 grain increments) (Max charge is 41.7 grains)
CBTO: 2.2758" (chosen to sit 20 thousandths off the lands)
Velocity: Unavailable

Primer: Remington 9-1/2
Brass: Lapua LRP
Bullet: 147 grain ELD-M
Powder: N555
Charge: 42 grains (3 5-shot groups) (Max charge is 42.6 grains...I only went to 42 because I shot a 0.23 MOA 5-shot group with this load last time out)
CBTO: 2.272" (chosen to sit 20 thousandths off the lands)
Velocity: Unavailable

Let’s assume the Forster gauge is correct. It measures .004” shorter than the SAAMI drawing. 1.537 vs 1.541. That would not be surprising based on the insert design.
But keep in mind your CTBO measurement, was almost right on and matched the first gauge closer to specs. Thats two data points.

Your old gauge measures 1.540 and does not close. So it’s probably safe to assume the chamber would be 1.5395 max. Possibly less if the Forster gauge is correct.

Your fired brass brass measures 1.5385”. If the bolt closes freely on fired brass, those numbers make sense.we are talking about +/- .0013”. Thats hard to reliably measure even with the best calipers without practice.

What really helps is complete data, and knowing you checked to make sure the bearing surface of the bullet was above the donut.

I will go back to the biggest question, why are the donuts forming on one firing?

Just to stir the pot in a different direction, are you 100% sure your calipers aren’t counterfeit?
Mitutoyo products are probably in the top 10 for being counterfeit.

 

[mikehill85]

I will go back to the biggest question, why are the donuts forming on one firing?

Yeah, I did have 3 form this last session. It really is the key question. I anneal every time. Is it possible I've gotten my brass too soft and it is flowing more than it should? I mean, the headspace is definitely on the tight side. Maybe that in combination of going near max results in the donuts.

I'm about as sure they aren't counterfeit as I can be. When I got it I did research on how to tell if it is fake or not and it doesn't have any of the characteristics associated with knock-offs and matched what you'd expect from the real deal. The code and serial number check out on the Mitutoyo website. Also, everything I measure with a known dimension checks out (e.g. 6.5 Creedmoor bullets have a diameter of 0.2640").

 

[dellet]

Yeah, I did have 3 form this last session. It really is the key question. I anneal every time. Is it possible I've gotten my brass too soft and it is flowing more than it should? I mean, the headspace is definitely on the tight side. Maybe that in combination of going near max results in the donuts.

I'm about as sure they aren't counterfeit as I can be. When I got it I did research on how to tell if it is fake or not and it doesn't have any of the characteristics associated with knock-offs and matched what you'd expect from the real deal. The code and serial number check out on the Mitutoyo website. Also, everything I measure with a known dimension checks out (e.g. 6.5 Creedmoor bullets have a diameter of 0.2640").

If you can get the same measurement every time, it doesn’t matter if it’s wrong(to an point) until you want someone else to reproduce something made from your specs. If you really want to check your calipers and measuring technique, they make what are called standards. Basically a precision ground piece of steel that is within .0001 of the stated size.

Personally I’d probably grab some different headstamps of brass and cross section a couple. Look for differences in thickness in the base of the neck and shoulder.

Before that seat a bullet in a couple pieces where the bearing surface is below the neck. Then carefully measure the neck in multiple places to check the taper. That will probably identify the problem brass before you fire it.

Trust me when I say the first time you turn the neck on a couple different pieces of brass of varying quality, you will wonder what you’re doing wrong. When it’s actually just the brass that sucks.

 

[243winxb]

Trim length can be as short as 1.900" I would not let brass grow longer then 1.910" As a test.

Some how the bullet is getting crimped in the barrel. Short chamber or long brass.

No crimp is needed, if using one.

Dont seat bullets long, keep them out of the rifling.


Donuts-

1. Outside neck turning. OR
2. Bushing die & dont size the neck all the way to the shoulder.

 

[ELR Harry]

Trim length can be as short as 1.900" I would not let brass grow longer then 1.910" As a test.

Some how the bullet is getting crimped in the barrel. Short chamber or long brass.

No crimp is needed, if using one.

Dont seat bullets long, keep them out of the rifling.


Donuts-

OP,
A friend was having issues recently blowing primers along with other "extreme" pressure signs. The root cause of his problem turned out to be that he did not clean the lube off his brass after FL sizing. Following his exact same loading process but wiping the lube off loaded rounds with Isopropyl solved his problem. Hope this helps...


Safety first!
Harry

 

[mikehill85]

OP,
A friend was having issues recently blowing primers along with other "extreme" pressure signs. The root cause of his problem turned out to be that he did not clean the lube off his brass after FL sizing. Following his exact same loading process but wiping the lube off loaded rounds with Isopropyl solved his problem. Hope this helps...


Safety first!
Harry

I use Hornady One Shot spray and I run the brass through a vibratory tumbler with walnut media for at least 3 hours after resizing. So, in my case, it probably isn't that. Thanks for the suggestion though. It is a good one.