Pressure / barrel speeds?

Shit! Thanks for that

Backed off half a grain and called it good? :D

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If given loaded rounds if you

1. Put one in the gun and bolt closed smoothly
2. Had a modded case and checked length then measured the reloads OAL
3. Had some of his used brass to visually check plus see how that went into the gun
4. Pulled one projectile and weighed the contents. Compared to the books.

After all of the above you d surely have to be ok ? And comfortable to pull the trigger on a couple of them ?
The .243 I m trying to sell for example can have to the right person 51 x brass 2 x fired plus there is 42 90 Gr Targex loads that are awesome..
To throw them away would be dumb. To reload them would be dumb. They are all set to measured length etc For me to keep them would be dumb !

If YOU were to buy this gun would you not use them ? :thumbsup:

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Originally Posted by Happy

If given loaded rounds if you

1. Put one in the gun and bolt closed smoothly
2. Had a modded case and checked length then measured the reloads OAL
3. Had some of his used brass to visually check plus see how that went into the gun
4. Pulled one projectile and weighed the contents. Compared to the books.

After all of the above you d surely have to be ok ? And comfortable to pull the trigger on a couple of them ?
The .243 I m trying to sell for example can have to the right person 51 x brass 2 x fired plus there is 42 90 Gr Targex loads that are awesome..
To throw them away would be dumb. To reload them would be dumb. They are all set to measured length etc For me to keep them would be dumb !

If YOU were to buy this gun would you not use them ? :thumbsup:

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I wouldn't now:)
In the past yes....my life is worth more than that two me:)
3 grains of powder two much in a small case like a 22-250 = no fun.
Not helped buy the particular power BM2.
I did all of the above before using the reloads......but it only takes one:)

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Originally Posted by BRADS

I wouldn't now:)
In the past yes....my life is worth more than that two me:)
3 grains of powder two much in a small case like a 22-250 = no fun.
Not helped buy the particular power BM2.
I did all of the above before using the reloads......but it only takes one:)

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Sorry Brads I m confused now ,,, If Im right you saying just the one was over the safety mark. Yes agree you could get caught out.


so did you pull and weigh one of the loads and it was ok within limits.. or ??? :thumbsup:

Inattentive reloading could be dangerous for sure. Our machine has so far never had a fail or over beep. We check it and recheck it during the process but others may not for sure.

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Originally Posted by Happy

Sorry Brads I m confused now ,,, If Im right you saying just the one was over the safety mark. Yes agree you could get caught out.


so did you pull and weigh one of the loads and it was ok within limits.. or ??? :thumbsup:

Inattentive reloading could be dangerous for sure. Our machine has so far never had a fail or over beep. We check it and recheck it during the process but others may not for sure.

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I checked 3 or 4 that where all as the should be, the one in the photo obvisiouly wasn't:(
The guy seemed very trustworthy and was a family man but people do funny shit like drinking while reloading, different powders out at once etc.

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Originally Posted by veitnamcam

Backed off half a grain and called it good? :D

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That's what I did to start with, shot a deer and then the bolt still would open that easy. Just as will the stag went down straight away!

Backed off another half grain after that.

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Originally Posted by BRADS

Someone will no the proper answer:) but this is my basic understanding.
Some of the longer double banded (Barnes pills?)create way more pressure than the same weight in other pills,
Has caught a few out:)

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Other way mate likes of Barnes and gs custom projectiles with more grooves have less engraving pressure so can load higher go faster for same pressures.

Gmx have a couple in them and nosler etips have none hard projectile engraves hard and puts pressure back up.

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Originally Posted by tui_man2

Other way mate likes of Barnes and gs custom projectiles with more grooves have less engraving pressure so can load higher go faster for same pressures.

Gmx have a couple in them and nosler etips have none hard projectile engraves hard and puts pressure back up.

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Thanks Abe that does make sense.

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Originally Posted by Gibo

Ok guys im trying to get my head around a few things.

Firstly pressure. Why is it lighter pills in the same cal can use more of the same powder than heavier pills. Is it to do with resistance?
How can this effect the case differently (pressure wise) ?

Secondly barrel speed?? If someone has told me my barrel is slow (tikka) how could a magnum of same cal same (tikka) go any faster?

Just getting my head around the basics of reloading so keen to learn. Hope these even make sense: D

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Heavier pills = bigger pills = more surface area touching the rifleing = more friction = more pressure

Here's some ejector marks I got in my 6.5-55ai. I have lapua brass now though so will see if I can go back to that charge of powder and not get the marks

Attachment 28112

Edit: What you can't see also is loose primer pockets, Fresh primers can be put in by hand and knocked out just as easy. I did measure it but forgot how much bigger they were but it was by a bit

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Originally Posted by Smiddy

another sign is the roundness of your primer after being fired, compare it to a unfired round - it should look the same and not flat

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Disagree Smiddy, It should have a dent from the firing pin:thumbsup:

Are those marks indented toby?

Yup, not just a shine but a small gouge

Trying to reach ..260 Ackley speeds eh?:p

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Originally Posted by R93

Trying to reach ..260 Ackley speeds eh?:p

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Was on a mission to get to 3000 with 140's haha dreaming of course but got close to 2,900. I think. I can check what my top speed was if you want?

I thought the 6.5 x 55 ai was faster than the .260 ai
I get 2950 easy.
What length barrel Toby?

What kind of charge was that with Toby?

I'll start another thread

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Originally Posted by Nick-D

Heavier pills = bigger pills = more surface area touching the rifleing = more friction = more pressure

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Mmm not sure about that, different shaped pills have different surface area. The weight is the key.

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Originally Posted by Nick-D

Heavier pills = bigger pills = more surface area touching the rifleing = more friction = more pressure

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Has more to do with F=ma

They are some good ejector marks!

Pressure is when you kick open the bolt, the primer falls out of the oval pocket and part of your bolt is gone.

https://farm4.staticflickr.com/3845/...fd52e72c_z.jpg
image by AckleyImproved, on Flickr

https://farm4.staticflickr.com/3843/...6c02769b_z.jpg
image by AckleyImproved, on Flickr

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Originally Posted by Tahr-Bound

Pressure is when you kick open the bolt, the primer falls out of the oval pocket and part of your bolt is gone.

https://farm4.staticflickr.com/3845/...fd52e72c_z.jpg
image by AckleyImproved, on Flickr

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Fark!!!!!

I fixed Willis bolt after some hot loads, out tahr shooting he smashed it up with a rock off come handle, she was all locked up hard, couldn't get bolt up had to undo the barrel to back pressure off to open bolt :o

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280Ack Imp using a load I had worked up to pressure and backed off to a safe level and fired many times. It was pissing down at the time and my only guess is water got into the chamber and caused a huge pressure spike. Scared me a lot.

Thats not from my reloading knowledge (dont have any of that). This is just an observation based on my understanding of physics. (Civil engineer once upon a time).
@Gibo

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Originally Posted by Nick-D

Thats not from my reloading knowledge (dont have any of that). This is just an observation based on my understanding of physics. (Civil engineer once upon a time).
@Gibo

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All good

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Originally Posted by Banana

Has more to do with F=ma

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Actually, f=ma has little do do with it, other than determining 'a' as the force does not change(charge weight stays the same). The spike in pressure is cause by the increased time the projectile stays in the barrel. This increases the peak pressure as more powder is converted to gas (ie more pressure) before the projectile moves enough for the peak pressure to drop away. Much the same as a pressurised water system.

The Big determining factors on this increase in barrel time are going to be mass or force (pill size & charge), static friction (friction build up before the prjectile moves) and of course barrel friction (givin that the projectile is slighly over bore). This is why they say do not use reloading data from 1 120 grain projectile to the next, as the frictional forces have a significant effect on initial pressure, veloctiy, and peak pressure achieved in the chamber and barrel. (as does projectile weight and charge size)

Again, no expert on ballistics, just observations based on what I remember from my engineering days

Maybe I should have written it as a=F/m. Same force but more mass = less acceleration. Same powder burn rate (roughly) and less projectile acceleration, so pressure peaks in less projectile travel.

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Originally Posted by BRADS

Ok when your brass does this:)
This wasn't my loading....it came with a gun I brought.....
Guy said they where all sweet, he seemed two no his stuff,
the first few where all fine
I really spat the dummy bolt lift was REALLY hard. I was glad it was in a Sako, a lesser action the results may have been a very different......
Lesson.....never use loads your given:)
Let's use this as a worse case example:)
http://img.tapatalk.com/d/14/08/13/6adapuru.jpg

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That definitely is a good one in the pressure department, I bought a Remington 788 in 243 a few years ago it came with some reloads from a well known ammo re-loader the shop told me who made the ammo all good with me but he never said fire at your own risk. First and second shot was sweet third shot big orange flash in my face with a big bang, bullet tumbles down range and smacks side on into target. Look at rifle smoke coming out of places it should not be coming out of along with the odor of burnt oil, go to open bolt hello it is jammed solid took it to feller who made ammo, the feller hammers bolt open, extracts case with case firmly implanted into bolt, hammers case out of bolt face primer drops on ground with a huge tit where it extruded into firing pin hole, primer pocket almost doubled in size and all case head stamping was just a bright shiny surface and all stampings gone, needless to say rifle was going to take a fair bit to fix.

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Originally Posted by Banana

Maybe I should have written it as a=F/m. Same force but more mass = less acceleration. Same powder burn rate (roughly) and less projectile acceleration, so pressure peaks in less projectile travel.

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Indeed, The burn rate will change with the pressure spike. Cant remember which way though haha. Same principles as an engine.

lets take two bullets of the same type but different weights out of the same rifle.
say 120gr 6.5BT and 140gr 6.5BT
Correct me if I'm wrong but, say 48gr of a 2209 moves the 120gr at 2900.
But as this is well over max it would be dangerous for the 140gr
Is this because the lighter bullet has gone further down the barrel with the same powder charge so the pressure will be less than a heavier bullet that has travelled less distance therefore leaving less empty volume behind the bullet for pressure increase.
Or is that a load of bollocks and it all happens in the chamber in fraction of seconds before the bullet even gets a few mm down the barrel.
Or Something else.

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Originally Posted by jakewire

lets take two bullets of the same type but different weights out of the same rifle.
say 120gr 6.5BT and 140gr 6.5BT
Correct me if I'm wrong but, say 48gr of a 2209 moves the 120gr at 2900.
But as this is well over max it would be dangerous for the 140gr
Is this because the lighter bullet has gone further down the barrel with the same powder charge so the pressure will be less than a heavier bullet that has travelled less distance therefore leaving less empty volume behind the bullet for pressure increase.
Or is that a load of bollocks and it all happens in the chamber in fraction of seconds before the bullet even gets a few mm down the barrel.
Or Something else.

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Fantastic question:D i will put mine on option 1

Its a compounding effect.
the more pressure that builds the faster it burns and the more pressure builds.
Light some powder poured on some concrete... pretty unimpressive.
Things that increase pressure but not limited to are.
increased weight
increased neck tension
hard jackets
less jump
increased bearing surface
etc etc etc.

this is why we work up and drop back a bit and work up again if changing anything dramaticly

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Yeah your right about pressure VC, you can throw Plastic shotgun shells in an open fire and they will fizz every time.
There is absolutely no pressure there.

Ahh I had wondered about pressure for jump, but makes sense when going from throat to lands that there would be a pressure increase when the bullet hits the rifleing

How would you work it when playing with jump to dial in a load?

Load it close to the lands to start and start low or shift back to a lower pressure node and filddle there, then ramp back up to bigger charges once you have found a COAL/jump that your rifle likes?

I usually start at max mag length or just touching the lands whichever is shorter.
ladder for pressure then load a few at steps close to max, if no joy accuracy wise start moving back.(can't go forward cos already on lands or won't fit mag)
load up some more shorter at say .5gr steps and try again.
often need more powder to get same speed after moving back.

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Cool man cheers

Ok so im going to do up some loads and find my pressure limit. Im already at .4 grains over max with no signs and no need to length size yet. May i ask how the gurus find pressure? Do I load 1x load and go up by .5 or liad 3x loads and go up slower say .3 and chrony at same time?
Keen to know what you guys do