Expander Mandrels & Primers

[357Max]

Now maybe this is common knowledge, but I'm mostly self taught & I've never seen it discussed.

Recently I was loading 400 rounds of 6.5 Creedmoor.
In my reloading process typically the last steps are to lube the neck with graphite, mandrel, powder, & seat the bullet. On this batch of 1 x Lapua I noticed the mandrel was pretty tight. These were annealed the same as all previous so I thought it odd, then a light bulb went off. Looking at the inside of the mandreled neck I could see that the mandrel had a very concentric fit. So well in fact I suspected it was air compression that made it feel tighter. These were primed with a CPS and all primers were .0055 below flush to start. Sure as shit I started measuring after mandrel and the primers were now .004 - .0045. Luckily I wasn't stroking the press fast and just stayed consistent so all primers were in the range stated above after.

Note to self: Mandrel before priming. Anyone else see this?
A drilled or EDM'd hole through the mandrels plus a hole in the die cap would ensure this couldn't happen.

 

[whatsupdoc]

Woa, now hold on there are you saying that you are moving/pushing the primer out by the air pressure
increase when you expand the neck using a mandrel?

No way unless you have bad primer pockets.

 

[357Max]

Woa, now hold on there are you saying that you are moving/pushing the primer out by the air pressure
increase when you expand the neck using a mandrel?

No way unless you have bad primer pockets.

Yes that's what I'm saying.
I measured before mandrel .0055 & immediately after .004 - .0045. Granted I did not use a depth mic, this was with Mitutoyo Absolute calipers. Repeated this at least 6 times in a row. When I was done I spot checked primer depth on at least 15 at random and all were .0035 - .0045. I think it was just 1 that was .0035.

Bottom line is yes air pressure can & will move the primer.

Edit: These were once fired Lapua 6.5C sml rifle primer. The original firing was from factory Berger ammo. Primer pockets were not bad.

 

[whatsupdoc]

I did the math you are getting approximately 14.960528 PSI, I doubt that is moving anything. (.264 bore .5 stroke)

Also if that is the case seating the bullet should move it some more.

 

[357Max]

I did the math you are getting approximately 14.960528 PSI, I doubt that is moving anything. (.264 bore .5 stroke)

Also if that is the case seating the bullet should move it some more.

Your real close on stroke. .542" beyond taper which also displaces space. Or .825" total.
As for bullets on these, They were 135 A-tips @ 2.880 & 130 Berger's @ 2.815 so only .220 bearing surface in neck.

I measured it repeatedly. I believe the primer.
You don't have to believe me, but it happened. It did not cause ES/SD to go to hell, but regaurdless I'm changing my process as a result.

I have no idea how much psi it would take to move a primer.

 

[whatsupdoc]

To really confirm whether the primers are actually moving would require better measuring equipment.

 

[357Max]

To really confirm whether the primers are actually moving would require better measuring equipment.

Agree partially. A lot of people don't do so well with measuring equipment. Yes a depth mic would get me accurate measurements to the tenth (.0001) & I have them. The calipers are accurate to .0005 when properly used. I got .001-.0015 difference every time & never the opposite direction.

I've got many years experience as a machinist & when I can measure .0055 repeatedly on a case & then 1 minute later after mandrel measure .004 -.0045 repeatedly on the same case, and the pattern repeats 6 cases in a row, I don't care about the tenths. I measured a bunch of them cause it didn't make sense. They moved. Now maybe this was some freak combination of 1x Lapua + GM205M that'll never happen again??

It happened to this 1x Lapua (still tight on go guage after firing) & I mandrel everything I reload. 224 Valk & 6 ARC the primer pockets do start to loose tension pretty quick. So for me, I think it's best practice to mandrel before priming going forward.

 

[spife7980]

Why don’t you mandrel the lubed brass when you are doing case prep before you put a primer in?

 

[whatsupdoc]

Why don’t you mandrel the lubed brass when you are doing case prep before you put a primer in?

That is how I thought everyone did it.

 

[spife7980]

Can’t speak for everyone but I only prime brass after it’s all sized and cleaned and trimmed etc

 

[Precision Underground]

Pop one of the primers out and see if the resistance is still there. That’s a lot easier than trying to measure .0001. My guess is it will still be there. Annealed brass can make for big time friction on a mandrel if conditions are right.

 

[Jefe's Dope]

I thought it was common practice to prime the case as the last step prior to loading with powder and seating the bullet.

 

[3rdfocal]

Now maybe this is common knowledge, but I'm mostly self taught & I've never seen it discussed.

Recently I was loading 400 rounds of 6.5 Creedmoor.
In my reloading process typically the last steps are to lube the neck with graphite, mandrel, powder, & seat the bullet. On this batch of 1 x Lapua I noticed the mandrel was pretty tight. These were annealed the same as all previous so I thought it odd, then a light bulb went off. Looking at the inside of the mandreled neck I could see that the mandrel had a very concentric fit. So well in fact I suspected it was air compression that made it feel tighter. These were primed with a CPS and all primers were .0055 below flush to start. Sure as shit I started measuring after mandrel and the primers were now .004 - .0045. Luckily I wasn't stroking the press fast and just stayed consistent so all primers were in the range stated above after.

Note to self: Mandrel before priming. Anyone else see this?
A drilled or EDM'd hole through the mandrels plus a hole in the die cap would ensure this couldn't happen.

I have made this mistake. Realized I didn't mandrel the cases before priming, thought I could do a quick pass with a mandrel while the cases were primed. 100% pushed primers looser. This was on almost new brass, very tight pockets. No idea what pressure was generated inside the case, but it was enough to move primers.

 

[Superjet]

This is interesting, I always prime prior to using my mandrel on my dillon. I’ll have to check my primer depth as well.

 

[Haney]

I have guns I shoot both jacketed and cast bullets in . I prep and prime all for jacketed . If I decide to load for cast I expand and flare primed brass . I use mica as a lube , I have never witnessed trapped air/pressure before . This is a new one for me .

 

[XikoPlavi]

Get an accuracy one primer pocket depth gauge. Some of your primer pockets may not be reamed out enough. In any case: I prime after the mandrel. For me the AO gauge helped a lot with consistent pocket depth measures

 

[357Max]

Why don’t you mandrel the lubed brass when you are doing case prep before you put a primer in?

I will be Mandreling before priming from now on. For me it was just a work flow that made sense. I re-tumble with ss pins after sizing so I dont mandrel when sizing. I want to retain the graphite from the mandrel for bullet seating.

After FL sizing, re-tumble, bake dry, trim/chamfer, prime, mandrel, powder seat. This flowed well because the CPS is on an inline fabrication mount. Once primed I'd put the press back on for mandrel & seating vs press mandrel - CPS - press seating.

Was hoping to find something today, but no. I de-capped 510 6.5C sml primer Lapua cases yesterday.
These included 295 Lapua that were factory primed with what appeared to be GM205M & now 1x fired. I did not see the primer issue with these even though I'd neck sized and mandreled them.
165 that were 1x fired originally factory ammo. These were the ones I saw this on (GM205M). When de-capping the primers did noticeably come out easier.
50 that were 2x fired and these came out with about the same force as the factory primed cases.

Checked 20 - 30 of each batch with primer go/no go gauges & they all feel the same.

Then I measured primers. The GM205M are the ones that moved & they did measure a little smaller. I kind of doubt even a half thou is enough to make a big difference, but I have no way to know the temper/spring back capability of the cups. I think this is the wild card. I have noticed before that cci #41 are stiffer seating compared to BR-4's & I attribute that to the stronger cup since they measure about the same.

GM205M = .1751 - .1753
cci #41 = .1754 - .17595
cci #450 = .1753 - .1758
BR-4 = .17525 - .17595

 

[Molon]

I’ve never primed cases before all sizing and prep work was completed. To test your hypothesis, I sacrificed five virgins to the Reloading Gods; five virgin Lapua cases in 223 Remington.

The inside diameters of the necks of the virgin Lapua cases gauged at 0.222”. The primer pockets of the cases were uniformed with a Sinclair primer pocket uniformer. The cases were primed with Federal Gold Medal Match primers using a 21st Century Bench Rest Priming Tool. The seating depths of the primers were then measured using an Accuracy One Precision Primer Gauge. The targeted primer seating depth was 0.002”. The average measured seating depth for the five cases was 0.0019”.

Next, I molyed the inside of the case necks and expanded the necks using a 0.2230” Sinclair carbide expander in a Forster CO-AX press. The primer seating depth was measured again using the Accuracy One gauge. The average primer seating depth was 0.0019”.

…

 

[Bacarrat]

I thought it was common practice to prime the case as the last step prior to loading with powder and seating the bullet.

That's what a normal person would do.

 

[918v]

Why is it that primers don’t pop out when you seat a bullet?

 

[357Max]

Why is it that primers don’t pop out when you seat a bullet?

None of them popped out. They moved a little with that batch of 1x cases using that lot of GM205M's.
The GM205AR's probably have a thicker cup & I have a thousand of them on the way now.

In post #5 shown bullet seating was less than half the stroke of the mandrel.

I'm not claiming this is a common thing. Just found it in this instance & have never seen anyone specifically recommend running the mandrel before priming.

This makes no sense to me either. Another thought I had was since these were seated with about .004 crush fit, maybe the compressed anvil is contributing to help push them out a little with such low air pressure??? That would also help explain why none moved very far.

Could be the primer pockets have some taper on these? Can't measure for that with current tools. Or it could be the cups on these primers are a little softer? Can't check that either. They did measure the smallest of the primer options I have on hand.

I've done 223, 224 Valk, 6 ARC, 6GT, 6.8SPC, & 308 win via priming prior to mandrel. Never an issue.
The only reason I started checking these is because for whatever reason the mandrel felt like it had a tight air seal on these. It's a feel on the press. Didn't feel like friction it felt like an air seal.

 

[357Max]

I’ve never primed cases before all sizing and prep work was completed. To test your hypothesis, I sacrificed five virgins to the Reloading Gods; five virgin Lapua cases in 223 Remington.

The inside diameters of the necks of the virgin Lapua cases gauged at 0.222”. The primer pockets of the cases were uniformed with a Sinclair primer pocket uniformer. The cases were primed with Federal Gold Medal Match primers using a 21st Century Bench Rest Priming Tool. The seating depths of the primers were then measured using an Accuracy One Precision Primer Gauge. The targeted primer seating depth was 0.002”. The average measured seating depth for the five cases was 0.0019”.

Next, I molyed the inside of the case necks and expanded the necks using a 0.2230” Sinclair carbide expander in a Forster CO-AX press. The primer seating depth was measured again using the Accuracy One gauge. The average primer seating depth was 0.0019”.

…

Molon - Thank you for taking the time to check this. Based on responses here I'm thinking this may be a pretty rare occurrence. Did you use GM205M or GM205AR?

The pockets are tight based on go/nogo guage, but I can't measure for taper. These particular GM205M's did measure smaller than the other sml primer options I have on hand, but not by a lot.

Mine were seated with about .004 crush fit & maybe the compressed anvil is contributing to help push them out a little with such low air pressure??? That would also help explain why none moved very far.

 

[Bradv86]

15 psi (if above is correct) applied to the surface area of a SRP at .174 diameter generates 0.36lb of force pushing on the primer... I have my doubts.

 

[Haney]

If indeed the primer is being pushed by the mandrel and not the bullet I would point out the mandrel displaces a lot more air than just seating a bullet in the neck .

 

[Haney]

Can’t speak for everyone but I only prime brass after it’s all sized and cleaned and trimmed etc

At least you finally admitted you don't know everything , maybe there is hope .

 

[spife7980]

At least you finally admitted you don't know everything , maybe there is hope .

I cant speak for everyone on mandrels but I can speak for everyone in that we think you are a massive cunt.

 

[918v]

If indeed the primer is being pushed by the mandrel and not the bullet I would point out the mandrel displaces a lot more air than just seating a bullet in the neck .

Lol you’re buying into this bullshit.