Interpreting Pressure Signs from Velocity (260 Remington load dev)

[bigedp51]

When you look at a reloading manual it will list a universal receiver and a pressure test barrel at minimum SAAMI chamber and bore diameter. If a specific firearm is used a strain gauge is glued to the barrel to measure chamber pressure. (Pressure Trace system)

I would also assume that Hodgdon's measured base expansion with calipers able to read to .0001 of an inch from their link above. In the older reloading manuals you were told .001 of an inch was a sign of excess pressure and now it is measured in .0001.

I do not understand why some people want to argue this topic when they do not have pressure measuring equipment or the proper tools to measure base expansion.

This was the point of brass flow into the ejector because you can see the brass flow. Meaning they didn't have calipers calibrated to .0001 of an inch.

Or below you can use a ruler and measure base expansion in 1/16th of an inch.

 

[Pdvdh]

Who's arguing. I'm promoting common sense.

BEFORE being misled into running out and spending your cash on a 0.0001" measuring tool, consider the consequences of shooting reloaded ammunition that expands your case heads 0.0005" or less on the initial firing.
It is not death, or even lesser destruction.
Understand that your loads could generate pressure causing 0.0005" case web expansion for your entire long lived life of reloading and shooting, and you'll be 110% safe and sound. You'll even experience good brass life.

Pressure doesn't even BEGIN to get interesting until the case web expands 0.001" or more on the initial firing.

You shouldn't expect to see any gas escape a case head without having more than 0.001" case web expansion.

Still need a 0.0001" caliper. Not for physical health or safety. Maybe psychological health... If so, maybe get the 0.0001" tool.

Be forwarned. All you'll measure is case web expansion that's meaningless gibberish.

 

[bigedp51]

Be forwarded. All you'll measure is case web expansion that's meaningless gibberish.

Measuring base expansion like seeing brass flow into the ejector tells you the strength and elastic limits of the brass. My less than $30.00 vernier caliper are only accurate to .005 and I do not plan to buy a more expensive caliper. BUT this does not change the base expansion limits posted at the Hodgdon's link.

I have had factory loaded Federal cases with over-sized primer pockets after the first firing. And this is due to soft brass and a thinner than normal flash hole web.

No one is forcing you to buy a new vernier caliper, but by your reaction here I have a visual impression of someone who's hairy knuckles drags on the ground when he walks.

Modern man learned to use modern tools. And some stone age people refuse to learn anything.

Have a nice day

 

[Pdvdh]

No one is forcing you to buy a new vernier caliper, but by your reaction here I have a visual impression of someone who's hairy knuckles drags on the ground when he walks.

Modern man learned to use modern tools. And some stone age people refuse to learn anything.

Have a nice day

Now it would be fair to characterize this as arguing. That's the consequence of communication with someone lacking common sense. They exhibit even less sensible behavior over time, become defensive, and ultimately degrade into launching personal attacks.

You should consider a couple 0.0001" measuring tools, for their associated physiological and psychological health benefits. Those 0.0001" tools have also been known to repair injured egos. But only a teensy weensy bit - around the magnitude of 0.0001 percent.

 

[bigedp51]

Don't take it personal, I just wanted the forum to know who was still using flint or possibly bronze tools.

Bottom line, the Internet has too many stone age midgets sitting at their computers pretending to be giants.
And people wonder why the newer reloading manuals are more conservative. And measuring base expansion is now given in .0001 of an inch. Or do some of you think that Hodgdon's test methods carry the decimal point too far to the right.

Digital Caliper Round-Up Which Digital Caliper Should I Buy?

 

[Pdvdh]

Agreed. Don't take it personal. I just wanted the members to know who was responding from a lack of common sense, an enlarged ego, and psychological distress.

Based on your track record, how could we expect anything you recommend, let alone a measuring tool, is worth anything more than $0.0001?

 

[bigedp51]

Agreed. Don't take it personal. I just wanted the members to know who was responding from a lack of common sense, an enlarged ego, and psychological distress.

Based on your track record, how could we expect anything you recommend, let alone a measuring tool, is worth anything more than $0.0001?

If you keep your hands in your pocket, your hairy knuckles wont drag on the ground.

 

[Pdvdh]

Your last two Posts combined, aren't worth $0.0001. All combined the totality of the information you've posted is less than $0.001. A negative value to those spending their money on the 0.0001" measuring tool you advocate as necessary to measure case web expansion indicative of dangerous pressure.

Your sense of humor is also lacking. You learn how to reload from these cartoons? Knowledge from the school of loony tunes and cartoons?

 

[desertcj]

Wow. While this is almost entertaining to watch, I'll just throw this out there. I was a machinist professionally for 6 years. I used Mitutoyo .001" calipers every single day and I still have and use the same ones. My experience is that yes you can TELL if your part is on this side or that side of the nearest thousandth, but you aren't actually getting an accurate measurement. A micrometer that can measure .0001" or ten thousandths is the correct tool that will give you an actual measurement of the tolerances we are talking about here. Yeah, everyone on the internet is a pro and they've done this and that. If you don't want to use a mic to measure case head expansion, it certainly isn't going to bother me.

 

[Pdvdh]

If you feel you need a 0.0001" measurement tool to collect case web measurements, when it's commonly agreed that up to 0.0005" case web swell is acceptable, the initial indication that pressures are getting interesting, then that's what you should buy.

No matter how many years you've been a machinist and no matter how well you understand precise and accurate measurements, have you considered whether that 0.0001" accuracy is necessary for the sole subject of this debate - case head expansion indicative of dangerously excessive cartridge pressure?

A few comments, if you please. After measuring 100s of cartridge case webs, with either a 0.001" caliper or a 0.0001" measurement tool, you'll come to understand that the case webs vary by more than 0.0001" around the case web straight out of the box from the factory production line. Even when you mark the measurement location to establish a datum point to repeat the measurement, you'll still experience slightly differing measurements. Which means you'll be measuring background noise that's both meaningless, and non-repeatable down to 0.0001".

You do understand that 0.0005" case head swell is generally considered acceptable on the first firing of a high powered centerfire cartridge case? No problems. Continue with the same powder charges until retiring the cartridge case. You understand that 0.0006" and even 0.001" case web expansion indicates nothing more than the cartridge primer pocket may expand with 2-3 additional shots at that powder charge and pressure to the point the case may no longer prevent gas leakage around the loosened primer pocket? This is not a matter of life and death, or even injury to the shooter or the rifle. It only predicts an earlier death of the useful cartridge case life cause by swelling of the primer pocket.

If you understand all this, and still feel the need to record case web diameter down to the +/- 0.00005", which is what you'll be able to see with a 0.0001" measurement tool, then that would just be a preference. Not mandatory for this purpose of ID'ing unsafe pressure levels. My bet is most won't recognize any material, meaningful benefit measuring down to +/-0.00005", when case web expansion at more than 10x that measurement is good to go.

Maybe collect 100 or more case web measurements pre and post-firing on virgin brass with a 0.001" caliper before promoting the need for the 0.0001" measurement tool. Because your comments indicate that while experienced in collecting accurate measurements in a machine shop, you've not been engaged in meaningful case web expansion measurements. Or you'd already understand the 0.0001" tool is completely unnecessary for identifying dangerous case pressure-caused case web swell. Smaller measurements for this purpose is simply an exercise of taking and recording numbers out of preference (like a hobby), rather than providing any practical use and benefit.

 

[desertcj]

Phorwath, I Personally don't care if you use a sledgehammer or even bite your fired cases to measure them. From what I can tell, your comments indicate that you not only enjoy listening to yourself talk...you also enjoy arguing for the sake of arguing. Most people use digital calipers, which pretty much suck in my opinion and probably aren't repeatable enough for this and also just because a tool CAN be used for a certain application (Which I acknowledged that it COULD) doesn't mean that it SHOULD. Very important differences when you are going to recommend to somebody else what the correct tool is for the task. Calipers can work, but they are not the best tool. What are the consequences of an inaccurate measurement? Well for one, you could end up arguing on the internet...lol. Two, loose primer pockets...Oh My! Three, why are we trying to walk so close to the lava with over pressure loads to start with?

 

[1Moose]

Thanks everyone for the thoughts / help. I'm trying to learn, and one of the things that is great about this forum is how generous everyone has been with their time. I really appreciate it, from all of you.

I had formulated some thoughts in my mind earlier in the day, and I'll hazard to post them--recognizing fully that I know less about this than everyone else commenting on this thread.

I had run into that info on Hodgdon site in my search for info on how much web expansion was too much. Thanks for referring me back to that. What I'm thinking now on both measurement and hardness:

Measurement:
If 260 Remington is somewhere in the .0005 - .0006 range for acceptable 1st-firing web expansion, then the chance of missing signs I was in that range with my current calipers would likely be small if I averaged out several cases (some "rounding" down to NN.nnn0 or NN.nnn5 and some rounding up). With a single case, logic would suggest it'd be pretty easy to get compounding errors pre- and post-firing that would underestimate case head expansion (and equally likely to overestimate case head expansion). Averaging several should help eliminate that.

Hardness:
The wrench in all of this seems to be that if some cases are made of brass with nearly double the hardness of others--and may even place more of it in the web area--then using the same criteria of maximum expected expansion for different manufacturers may have highly different factors of safety built in (i.e., cause very different interpretations on where one is starting to get into that range of pressures). One would guess (correctly?) they set those expansion guidelines with the "weakest" brass?

With all of the above, I can see why some reloaders, 1) load up until they see other pressure signs and then back off, or 2) use factory rounds with the same brass (in my case likely expensive factory rounds with Lapua brass) as a baseline.

Honestly, I'd like my brass to last a while, but I really just don't want to lose an eye or something. I'm okay if I only get 8 instead of 15 loadings out of it. One factor in my mind is that because I have a 1:8.5 twist, I want to ensure I have enough velocity to maintain stability in the 140-143 grain bullets out to maybe 700 yards. Fortunately, I live at 5000' so that helps there. I am a bit frustrated with myself that I didn't get an 8-twist when I had this rifle made. I need to let that go as that's not worth the stress I feel when I overthink that!

 

[Pdvdh]

Well now that you've settled the matter that you personally don't care...,
by all appearances, you sure seem to care.

You ought to measure some case webs before deciding what's significant enough to merit caring about. Before proclaiming on behalf of all non-machinist members which tool is the proper tool for a task and purpose you've clearly never engaged in.

Your entire input here could have become pertinent and meaningful if you had simply explained why us non-machinists need a 0.0001" measurement tool capable of +/-0.00005" measurements, when the only necessary measurement to prevent hazard exceeds those measurement capabilities by a factor of more than 10.

I get it, you only care about the things you care about. Like lava flow... Thanks for that tip. That's a big help.

 

[desertcj]

Well now that you've settled the matter that you personally don't care...,
by all appearances, you sure seem to care.

You ought to measure some case webs before deciding what's significant enough to merit caring about. Before proclaiming on behalf of all non-machinist members which tool is the proper tool for a task and purpose you've clearly never engaged in.

Your entire input here could have become pertinent and meaningful if you had simply explained why us non-machinists need a 0.0001" measurement tool capable of +/-0.00005" measurements, when the only necessary measurement to prevent hazard exceeds those measurement capabilities by a factor of more than 10.

I get it, you only care about the things you care about. Like lava flow... Thanks for that tip. That's a big help.

You not only assume far too much, you also talk about your assumptions far too much as well. Perhaps to reinforce to yourself that your assumptions are correct?

Good night sir...