Temperature increases pressure signs?

[tapper]

Hi guys,

Looking for some confirmation on this as it's not something I want to test myself.

If you're near or at max load but not seeing any pressure signs using hand loads, is it right that shooting on a hot day, hotter rifle the pressure will be increase?

So you should allow a little less for this?

A difficult one to test for a newbie without getting risky to find out

[ex_reven]

What are we talking about here, pistol or rifle reloads?

Pressure signs will vary depending on a lot of factors, they may present themselves early or they may show up too late to be of any use.
Generally on a hot day your loads will run at a higher velocity than on a cold day - this varies between powders.

If you load for pistol you might find that your low velocity target loads that cycle your action fine one day, will cause stovepipes and failure to eject on cold days.

Is there any particular reason you are pursuing a max load for your particular firearm?

[Jack V]

Yes absolutely correct. Even with ADI powders some pressure increase will still happen as the powder heats up . Loads developed in winter at max can start causing trouble in Summer . Leaving a max pressure round in the chamber of a hot barrel while you wait for a shot can pop primers and give hard bolt lift or worse . Leaving said rounds in the sun or a hot vehicle can also have the same effect .
There is a few very good reasons why powder companies have recommended safe loads on the lighter side and then a stated max .

[ex_reven]

On that note, if you are seeking accuracy - it does not necessarily lie in the hottest/fastest load.

Your rifle will have accuracy 'nodes' that occur at certain velocities. You can have several different velocities around which you will experience a marked increase in accuracy/consistency. If you run a ladder test, you can identify where these 'nodes' lie and can then do further load development around these nodes until you work up a load that suits the purpose of the firearm.

[Noisydad]

An old military snipers trick to get a little more velocity for long rang shots is to sit cartridges in the sun to heat up.

[tapper]

Is there any particular reason you are pursuing a max load for your particular firearm?

Hi ex-reven.

I'm not pursuing max anything at the moment. I'm new to reloading for rifles and have done very little.

I'm going slow and sensible but there is so much to read, so many potential problems people talk about.

I'm just getting information together ahead of time

Thanks for the answers.

[wayward]

Leaving a max pressure round in the chamber of a hot barrel while you wait for a shot can pop primers and give hard bolt lift or worse

"pop primers"

You mean firing the round?

Or it bursts on itself without firing you mean?

[tapper]

On that note, if you are seeking accuracy - it does not necessarily lie in the hottest/fastest load.

Your rifle will have accuracy 'nodes' that occur at certain velocities. You can have several different velocities around which you will experience a marked increase in accuracy/consistency. If you run a ladder test, you can identify where these 'nodes' lie and can then do further load development around these nodes until you work up a load that suits the purpose of the firearm.

Yep, I've understood that from reading about reloading, fast doesn't mean accurate.

That's fine with me. Still to do a ladder test but I will, then Ill find my accuracy nodes

[tapper]

Yes absolutely correct. Even with ADI powders some pressure increase will still happen as the powder heats up . Loads developed in winter at max can start causing trouble in Summer . Leaving a max pressure round in the chamber of a hot barrel while you wait for a shot can pop primers and give hard bolt lift or worse . Leaving said rounds in the sun or a hot vehicle can also have the same effect .
There is a few very good reasons why powder companies have recommended safe loads on the lighter side and then a stated max .

I'm using ADI reloading data. That seems to be pretty renowned for generous safety margins at the top end of the loads.

[Carter]

An old military snipers trick to get a little more velocity for long rang shots is to sit cartridges in the sun to heat up.

Man, you'd need some good intuition on your shots to be adding extra range on the fly for shots that long.

[upup]

Yes absolutely correct. Even with ADI powders some pressure increase will still happen as the powder heats up

ADI do the one for Aussie Outback ammo which isn't so effected by temperature don't they?

Can't remember which one, do you recall by any chance? Just curious.

[Jack V]

"pop primers"

You mean firing the round?

Or it bursts on itself without firing you mean?

No , usually just a split primer or gas blow by at the edge . Ignition under those circumstances is called a " cook off " .

[Jack V]

ADI do the one for Aussie Outback ammo which isn't so effected by temperature don't they?

Can't remember which one, do you recall by any chance? Just curious.

ADI powders are less effected by heat than many other powder brands but not immune to heat caused pressure increase . It still happens to a lesser degree . When a load is right at primer busting max even a slight pressure increase can be enough to cause major problems .

[headspace]

Most ADI powder are pretty stable from an ambient temperature point of view, the stuff they load for the military has to endure all sorts of variables, plus it has to be loaded hot enough to not cause feed problems in automatic weapons. I think most of their stuff is very stable, I use 2206H, 2208, 2213SC and 2207 and have yet to have a noticeable problem, although some of my loads are close to or slightly above their recommended max. Once again it depends on the individual rifle and cartridge case.

[sbd3927]

ADI do the one for Aussie Outback ammo which isn't so effected by temperature don't they?

Can't remember which one, do you recall by any chance? Just curious.

Yes, but the powder used in the Outback ammo isn't available for purchase . A friend asked a contact at ADI about it. "Variants of 2208 and Benchmark series"

Best brass source I could find for my 308 was 120rounds of ADI Outback. I've pulled some apart to use once the brass is formed (saving for trips up north). Powder cylinder size is half that of 2208, quite different smell, slightly compressed load.
Standardising the powder load seems to have pulled it under 1/2moa (46.3gn +- .5gn on 40 factory loads, half within .1gn)

Benchmark 8208 is the one mentioned in their catalog as being more temperature tolerant, but max load for a .308 is 42.8, a long way from whats in the factory rounds.

[upup]

Yes, but the powder used in the Outback ammo isn't available for purchase . A friend asked a contact at ADI about it. "Variants of 2208 and Benchmark series"

Ah ok, didn't realise that.

For some reason I thought it was sold as a regular powder under a AR xxxx label.

[Jack V]

Some factory ammo is loaded with blended powder to give very specific performance . Most of the time we can duplicate the same performance with standard powders but sometimes not . They also swap about al lot and we can never be sure what the powder really is. I think it is way better for reloaders to ignore what the factory may or may not be doing and just stick to producing a good safe load with the components you can buy easily .

[headspace]

My 308 with Winchester brass is using 45.5gn of 2208 behind a 165gn Hornady Interlock. It shoots extremely well and has been chronographed at an average 2,740fps over 5 rounds. No complaints from either me or the rifle.
JD

[Jack V]

There is not much that you can't knock over with a 165 at 2740 fps. especially when the accuracy is good.

[sbd3927]

My 308 with Winchester brass is using 45.5gn of 2208 behind a 165gn Hornady Interlock. It shoots extremely well and has been chronographed at an average 2,740fps over 5 rounds. No complaints from either me or the rifle.
JD

Good to know, I haven't tested past 44.6 yet. 44.3 was 2.5" above crosshairs,, 44.6 has come back down to 1" From your data might be worth poking a bit higher, no pressure signs, just soft federal primers flattening same as factory round.

The outbacks hitting in between, around 1.5" above crosshairs and is only spreading around 1/4", so seems like a sweetspot. I think i'll be trying to match the velocity, which is stated at 2750. Chrono would make it easier... Outback uses 165gn gameking, I'm loading 165gn Hornady btsp interlocks (very similar shape, and cheapest I could find for plinking $46/100)

[Korkt]

Good to know, I haven't tested past 44.6 yet. 44.3 was 2.5" above crosshairs,, 44.6 has come back down to 1" From your data might be worth poking a bit higher, no pressure signs, just soft federal primers flattening same as factory round.

It's worth trying, but don't get stress over increasing velocity... It doesn't equate to accuracy.

Your most accurate load could be anywhere in the load range, so do a full workup to find the right one.