Thread: What are you using for pressure estimation in your handloads.

Greetings all,
I have been thinking a lot recently about how a novice handloader deals with estimating pressure in their handloads. Recently I did a short talk about handloading at our local NZDA branch. A quick survey of those present showed that most were either novice or aspiring handloaders so the more detailed notes on more advanced techniques were scrapped and a more basic talk and demo presented. Unsurprisingly this showed a lack of knowledge on the dangers of excessive loads. So I started thinking that I have hopefully learnt a thing or two over nearly 50 years of handloading so perhaps this could be shared through a series of short articles. To ensure the ideas offered are broadly based a consultation with the brains trust (this means you gentle reader) seemed desirable, So how do you keep from blowing your rifle and yourself up?
Regards and thanks Grandpamac.

I do what the manuals TOLD ME TO DO when starting out.....watch primers and primer pockets,use feeler guage for brass deteriation. if a load feels hot,it probably is hot. ejector swipe, heck Ive seen some REALLY hot loads that shouldnt have been..factory loads that blew primers out,blackend around primers,so flat the primer was nearly out to writing on case head. first reload and case had split, my early Norma manuals have pictures of what a primer SHOULD look like...so does the Nick Harvey book come to think of it... YES I know different primers are different hardness but if you use the same primers the pressure signs should all other things being equal behave the same way...softer primers arguably will show load is getting hot sooner than a hard primer...and there is a wealth of information out there telling you which are hard or soft.
bottom line for me...stick to published load and dont try to hot rod it ...most important is dont use chronicgraph so velocity chasing doesnt occur,others will argue using one tells you if load is getting hot...yes and no.... each rifle is different.. some like it hot some are over pressure at middle of road data levels.
some barrels/chambers/actions are just slow by comparison to same rifle off same production line.... without using said chronic graph you would never know this and could be quite happy with an accurate load that kills well.

I find velocity a pretty good indicator, but usually I will look at a culmination of things and then the velocity kinda just confirms it.
primer flattening, ejector stamp and or swipe, heavy bolt, loose primer pockets etc however not all cartridges give these symptoms (apparently AI cartridges are renowned for this)
I generally try to stay away from pressure so most of the time i am not loading max loads, it's still nice to know. I'm more interested in consistent velocity and accuracy

Velocity and Gordon’s Reloading Tool (GRT).

I use GRT to predict a load at maximum pressure, and note the velocity. Then run a ladder test up to that velocity. Finally I will calibrate GRT with my measured velocity to correct the pressure value.

If I see any pressure signs something else is wrong. I also cross reference with published data for a sanity check.

I have found primer flattened to be solely determined by hardness of primer and is not a useful pressure sign. Primers in my 6.5prc will almost no flattening at pressures you should be avoiding.
Ejector swipe and bolt lift seem to be good clues to back off for the straight walled cases.

For 6.5PRC using AR2213sc, I believe the book data maximums are very low and I trialled shooting one shot each of increasing 0.5grain increments (something I don't recommend but I was curious to see where pressure was as I worked up to max and felt like I was shooting mild loads still). I won't tell you what load I found noticeable signs of pressure at but I can tell you it's quite a long way from book max in my rifle. However, what I found did correlate with almost all the anecdotal data I could find online for loads people had used with this powder before book loads were available.
Interestingly, 22" barrel and I started seeing pressure when the velocities started matching the book max load, and excess pressure when just over.

I quite like load development for black powder loading, fill the case up, jam the powder in with a compression die and stick a projectile on top .

Originally Posted by Micky Duck

I do what the manuals TOLD ME TO DO when starting out.....watch primers and primer pockets,use feeler guage for brass deteriation. if a load feels hot,it probably is hot. ejector swipe, heck Ive seen some REALLY hot loads that shouldnt have been..factory loads that blew primers out,blackend around primers,so flat the primer was nearly out to writing on case head. first reload and case had split, my early Norma manuals have pictures of what a primer SHOULD look like...so does the Nick Harvey book come to think of it... YES I know different primers are different hardness but if you use the same primers the pressure signs should all other things being equal behave the same way...softer primers arguably will show load is getting hot sooner than a hard primer...and there is a wealth of information out there telling you which are hard or soft.
bottom line for me...stick to published load and dont try to hot rod it ...most important is dont use chronicgraph so velocity chasing doesnt occur,others will argue using one tells you if load is getting hot...yes and no.... each rifle is different.. some like it hot some are over pressure at middle of road data levels.
some barrels/chambers/actions are just slow by comparison to same rifle off same production line.... without using said chronic graph you would never know this and could be quite happy with an accurate load that kills well.

did you perhaps also get told not to use powder you cannot 10000% verfiy is what you are told it is ? .......too soon ?

Reloading manuals are very conservative - they have to be so as to allow for the idiot that starts at max and works up from there.
Personally I start in the mid range with a suitable powder, projectile combination and slowly, as in .3 or .5 of a grain, work up from there, looking for accuracy and a good group. Once Ive established that, I get the chrony out and measure velocity. Then I enter the data into my ballistics calculator and away I go. Nothing magical, just simple and straightforward, and the results speak for themselves.
There are a number of pressure signs that each individual rifle and cartridge combination will demonstrate, but generally to much pressure will be significant increased recoil, significant increased noise, many aspects of the case expanding to fit the chamber resulting in bolt markings on the case head, split necks, case head separation, blown or flattened primers, and more. This usually has the secondary effect of a bolt which is stiff to lift

Greetings all,
It was all warm and horrible outside this morning so I thought I should find out what three of my oldest manuals had to say on pressure estimation. They were Reloading Simplified by Cyril Waterworth 1961, Speer No 9 about 1975 and Reloading Manual for Rifle and Handgun by Nick Harvey 1980. All included primer leak, hard extraction and case head expansion as signs (Speer also included primer appearance). All three did not consider primer appearance to be a reliable indicator of pressure. Interesting.
Regards Grandpamac.

Originally Posted by Magnetite

Velocity and Gordon’s Reloading Tool (GRT).

I use GRT to predict a load at maximum pressure, and note the velocity. Then run a ladder test up to that velocity. Finally I will calibrate GRT with my measured velocity to correct the pressure value.

If I see any pressure signs something else is wrong. I also cross reference with published data for a sanity check.

This

Originally Posted by dannyb

did you perhaps also get told not to use powder you cannot 10000% verfiy is what you are told it is ? .......too soon ?

it will always be too soon.....

Originally Posted by Micky Duck

it will always be too soon.....

you learned a lesson I will never forget....at least you escaped mostly unscathed mate.

Currently, my face (nearest thing to the pressure containing bit that is attached to me). As I'm quite attached to my face, what I am doing is using a very good systematic approach to loading which hopefully prevents distraction and fluffups and then making sure I use the correct info with the correct bits and inspect and work up each load with brain and care engaged. Using accurate measuring devices and inspection tools combined with knowing what to check for is probably (from my experience anyway) a bit more reliable that estimation of pressures as a slightly different throat combined with a different bullet type and case volume can produce a quite different than expected pressure result. I've had one rifle that was anti-pressure and just generally did not read the loading manuals. Was producing case stamping and signs of pressure only a few grains past start loads, which was - unexpected on an '06 sized case...

Originally Posted by grandpamac

Greetings all,
It was all warm and horrible outside this morning so I thought I should find out what three of my oldest manuals had to say on pressure estimation. They were Reloading Simplified by Cyril Waterworth 1961, Speer No 9 about 1975 and Reloading Manual for Rifle and Handgun by Nick Harvey 1980. All included primer leak, hard extraction and case head expansion as signs (Speer also included primer appearance). All three did not consider primer appearance to be a reliable indicator of pressure. Interesting.
Regards Grandpamac.

Primers are an interesting one. Soft primer cups can show marking, backing out and flattening that actually shows a too-light load rather than too-hot. Also, if the firing pin hole in the bolt face is excessively chamfered (Remington hey?) a soft primer can extrude back filling the hole or worse case - rupturing around the pin tip. This makes you suspect high pressure when you are simply at the bottom end and the case isn't setting back against the bolt face properly. Can also lead to short case syndrome which overworks the brass and creates other issues...

Originally Posted by No.3

pressures as a slightly different throat combined with a different bullet type and case volume can produce a quite different than expected pressure result. I've had one rifle that was anti-pressure and just generally did not read the loading manuals. Was producing case stamping and signs of pressure only a few grains past start loads, which was - unexpected on an '06 sized case...

RUMPY has a .270 that is like that...low to middle of book is enough,anything past middle of road and its getting too warm of load... whereas mine will tolerate more. the rifle my buddy DannyB referred to happily handled 3 grns above book maximum UNTIL I fed it wrong powder..it had a very long throat and loose chamber so was in effect a larger than normal case capacity.... every rifle is different,if we all did what every single loading manual,pamphlet etc said and started low and worked our way up slowly....we would all be fine,where we get into trouble is the old enemy ASSUMPTION .... the mother of all fcukups.

Yep, the old 'one load in all rifles' trick, when you workup a load in one rifle and then expect it to go in everything. A mates .308 is a good example of that, the chamber swallows everything quite happily. But, try chambering a case from that rifle into another .308 and it doesn't even get it's nose in the door before there's a refusal. That thing damn near needed .30-06 load data...