Hidden Pressure Reading: A Method

[Dean2]

This is what you are TOLD…have you ever actually tested this?
I have!
There is TRUTH in fast or slow barrels and pressure readings of SAID beliefs DO NOT ring true…

Cheers.

If you are using actual pressure test gear please publish those results for your fast and slow barrels. Outside of that, you are guessing what pressures you are developing. Of all the metrics available to the layman loader, case head and web expansion are the most accurate.

The quote below is from Hodgdon's site and they should know a bit about the subject. When you see case head expansion in the .0006 range as indicating maximum pressure, and you have primer pockets growing by .0015, or over double that, it is pretty clear that load is well past limits.

One of the first rules of handloading is to always follow the approved reload data. The cautious reloader gradually works up to approved maximum loads to ensure his particular gun does not show pressure signs. Generally this is visual observation of the fired shell case head and primer. There is another slick way to check for pressure signs if you are interested.
Using a blade micrometer that measures in ten thousandths (.0001″), new, unfired cases can be gauged before and after firing to determine reasonably accurate maximum loads. Micrometers measuring in thousandths (.001″) are insufficiently accurate to perform these measurements, and should not be used. Previously fired cases cannot be used accurately due to various levels of brass hardening. Measurement is taken just ahead of the extractor groove on the case head and must be taken at the same place on the case before and after firing. By placing a small mark on the case head – entering the cartridge in the chamber with mark at 12 o'clock – a consistently accurate measurement can be taken with each firing.
Lower pressure rounds, like the .30-30 Winchester, usually yield maximum pressures at .0003″-.0004″ expansion. Modern cartridges, like the .223 Remington, will show maximum pressure at .0004″-.0005″, while .308 Winchester, .270 Winchester, etc., typically yield .0005″-.0006″ expansion at max pressure. Magnums, like the .300 Winchester Magnum, show maximums at .0006"-.0007" expansion, and should be measured on the belt.
In conjunction with these measurements, case head signs of pressure should be monitored as well. These signs include very flat primers, slightly cratered primers, ejector marks on the case head, and stiff extraction. All these case head signs indicate high pressure, and loads should be reduced until these signs disappear.
As always, start with the beginning load listed, and cautiously work up to the maximum shown for that set of components, using the methods listed herein.

 

[Opa-lopa]

What kinds of speeds are you running?

Pressure equals speed and speed equals pressure

Until it doesn't. Seen bullet structures slump, causing increased bearing length, higher resistance pressure & chamber pressure w/o increasing MV. It's like hitting a wall.

 

[ButterBean]

Nosler brass has been soft for me. Slowly weeding out that brass in favor of Peterson or ADG.
I use a go, no go pin as well. It's very fast to check.

I have found this to be true as well

 

[VinceMule]

WOW! That barrel is going to last a very, very long time!

 

[Orange Dust]

If you are using actual pressure test gear please publish those results for your fast and slow barrels. Outside of that, you are guessing what pressures you are developing. Of all the metrics available to the layman loader, case head and web expansion are the most accurate.

The quote below is from Hodgdon's site and they should know a bit about the subject. When you see case head expansion in the .0006 range as indicating maximum pressure, and you have primer pockets growing by .0015, or over double that, it is pretty clear that load is well past limits.

Yes, back in the old days when we were working with wildcats a lot, we were taught to measure the head just below the web. Load until .001 expansion, and then back off a grain. That would put you around .0006 as you stated above, but difficult to accurately measure. We were also taught to put a mark on the case (sharpie) and that is your reference point. measure from there before and after, and position the cartridge mark up in the chamber. You have to be very consistent doing this. We did it with once fired, formed brass. I don't load on the edge anymore, and have only one wildcat left. By the time you have visable ejector marks or hard bolt lift, you are way past a .001 swell. There is soft brass out there, but you are overpressure for that lot of brass. Some brass can take more pressure than others. I have always felt If you use this method you have a safe load for the components you are using. don't know the pressure, but never really cared if it was safe. Some of my best loads have been at or near this limit.

 

[WYO300RUM]

Yes, back in the old days when we were working with wildcats a lot, we were taught to measure the head just below the web. Load until .001 expansion, and then back off a grain. That would put you around .0006 as you stated above, but difficult to accurately measure. We were also taught to put a mark on the case (sharpie) and that is your reference point. measure from there before and after, and position the cartridge mark up in the chamber. You have to be very consistent doing this. We did it with once fired, formed brass. I don't load on the edge anymore, and have only one wildcat left. By the time you have visable ejector marks or hard bolt lift, you e'

sway past a .001 swell. There is soft brass out there, but you are overpressure for that lot of brass. Some brass can take more pressure than others. I have ajlways felt If you use this method you have a safe load for the components you ajre using. don't know the pressure, but never really cared if it was safe. Some of my best loads have been at or near this limit.

Great advice.
I haven't seen you around in a long time ! J

 

[Orange Dust]

Great advice.
I haven't seen you around in a long time ! J

Had some health issues, but I am a big boy

 

[VinceMule]

Comments we make have to be tailored for the new guys that are trying to get a handle on reloading and some of the really dumb azzes who just have to go over the max because in their minds, this is what is forbidden, which makes them like it.

When working up loads, if you stand up the cases in the Case Guard where the case head is exposed, you can read a lot of pressure off of the depth of the lettering on the back of the cases. As you load goes up, the depth of the lettering will have less depth. You should be looking at the case head with a magnifying glass or a Jewelers loop. You will actually be able to see how the bolt head is not square on a Non trued and some custom actions. Then you will see very faintly the edges of the ejector hole, which may need deburring. Next you will see the very faintest amount of bolt swipe, maybe not enough to actually scratch the face on the brass, just mashing it. I reject all firing pin flow as pressure, but it is an issue to watch, especially on small bolt face cases where the thickness of the primers is less than large rifle primers.

By the time you are getting case head swiping, and removing metal, pressures are a point where accuracy is blown.

A very slight increase in bolt lift is where many cases shoot their best, and this could cost you a quick follow-up shot in the field, know your limits. Full-length sizing/Shoulder bumping after a slight increase in bolt lift will be required, and I could that varying amounts of pressure needed to close the bolt on loaded rounds caused flyers.

Web dimensions in the chamber vs sizing dies vs web dimensions of various brands of brass is a real can of worms. I am hesitant to jump on board with the "latest and greatest" new cartridges as it often is a nightmare working out brass/die/chamber dimensions.

 

[WYO300RUM]

Had some health issues, but I am a big boy

Good to hear you are doing better. Welcome back.

 

[Orange Dust]

Comments we make have to be tailored for the new guys that are trying to get a handle on reloading and some of the really dumb azzes who just have to go over the max because in their minds, this is what is forbidden, which makes them like it.

When working up loads, if you stand up the cases in the Case Guard where the case head is exposed, you can read a lot of pressure off of the depth of the lettering on the back of the cases. As you load goes up, the depth of the lettering will have less depth. You should be looking at the case head with a magnifying glass or a Jewelers loop. You will actually be able to see how the bolt head is not square on a Non trued and some custom actions. Then you will see very faintly the edges of the ejector hole, which may need deburring. Next you will see the very faintest amount of bolt swipe, maybe not enough to actually scratch the face on the brass, just mashing it. I reject all firing pin flow as pressure, but it is an issue to watch, especially on small bolt face cases where the thickness of the primers is less than large rifle primers.

By the time you are getting case head swiping, and removing metal, pressures are a point where accuracy is blown.

A very slight increase in bolt lift is where many cases shoot their best, and this could cost you a quick follow-up shot in the field, know your limits. Full-length sizing/Shoulder bumping after a slight increase in bolt lift will be required, and I could that varying amounts of pressure needed to close the bolt on loaded rounds caused flyers.

Web dimensions in the chamber vs sizing dies vs web dimensions of various brands of brass is a real can of worms. I am hesitant to jump on board with the "latest and greatest" new cartridges as it often is a nightmare working out brass/die/chamber dimensions.

All true. But, it takes more experience to read pressure this way than it does to learn to use a micrometer properly. Handloading is a very difficult thing to learn without a Mentor. My kids are grown now (28 and 32). They are shocked at the current prices of ammo. Both of them have asked me to teach them to load shells this summer. I have bought them new equipment, and enough components for each of them to load 1000 rounds. after they load that all up and shoot it they are on their own. They are asking so many questions, I am thinking of starting a thread on the process of teaching them. Seems like making anything in this country is a lost art, handloading included. Handloading is very different than reloading and can become highly technical. Guess that is why it is such a rewarding hobby.

 

[Dirtrax]

Part of the issue is that our terms are vague and misleading.

 

[Orange Dust]

BTW folks, in case I wasn't clear. You cannot measure cases with calipers to find pressure. They have too much error. You must use a micrometer. You must also learn how to use it properly and read it if it is not digital. If you live in or near a large town there will be a store that sells machinist supplies. Buy it there, and the salesman at the store will be glad to show you how to use it properly. Don't buy it on the web. It does take some practice to get the same number every time. You cannot use the method I described above until you can consistently measure a case. A MIc is invaluable to a handloader anyway, and every handloader should own one and know how to use it.

 

[VarmintBob]

Until it doesn't. Seen bullet structures slump, causing increased bearing length, higher resistance pressure & chamber pressure w/o increasing MV. It's like hitting a wall.

Once % powder burn gets below 98%, you can add powder which WILL increase peak pressure since that happens when the bullet is about 4" down the barrel but velocity does not increase since the additional added powder is burned outside the barrel. If the barrel were a bit longer then velocity would have increased.

 

[FullCurl8]

You guys are free to do whatever you want, but I really can't believe how many times this has to be repeated. If you are getting hard bolt lift you are WAY WAY past pressure limits. You are north of 90,000 PSI and past even proof test loads. If you are losing primer pockets after 1 or 2 firings, even on soft bras, you are Way past pressure limits. All of the traditional pressure signs, flat primers, ejector marks etc are well over the proper pressure.

Hodgdon publishes the pressure for all their loads, and these are all 100% tested. Different guns, powder, brass will give slightly different results but if you think you can significantly exceed their velocity or loads you are just fooling yourself. If you think loads have been lawyered, call Hodgdon. They will confirm that better testing equipment and current powder profiles is what has lead to current loads.

Like I said at the start, guys are going to do whatever they want, but I am glad I don't have to share a range with guys shooting 100,000 PSI loads.

Have any range catastrophic failure evidence? Did Hodgdon share with you how component differences can and do represent themselves as pressure signs when they may be component failure signs?
The practice of finding pressure signs then moving back probably isn't a great idea, but I cannot say I have witnessed or heard of a failure that could 100% be attributed scientifically to too much (incremental increases) in powder, VS accidental double charges, bad metallurgy in firearm.