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Aussie_Shooter
05-06-2013, 09:33 AM
I have a 32" barrel and am almost in the process of reloading some ammo.

Does it matter how "hot" the load gets?

I don't want to prematurely wear out the barrel or have to much pressure build up.


I can easily work up the loads so that it matches the maximum MV with less powder due to the extra barrel length but if I can squeeze more out of the load is there a maximum safe MV for the 175 gr's or any projectile for that matter?

MarkR
05-06-2013, 01:16 PM
I don't believe you could push it too fast with a .308....a 300 Patriot maybe...:)

Hunter
05-06-2013, 01:28 PM
Does it matter how "hot" the load gets...is there a maximum safe MV?

You're kidding, right? :confused:

PS It's not a matter of how much MV you get, it's a matter of how "hot" is the load.

Aussie_Shooter
05-07-2013, 02:35 AM
No I'm not kidding.

I don't want to push the prodgy to fast ( if at all possible ) so that the pressure is excessive or the barrel gets prematuerly warn.

I am concerned if I use the hornady oal gauge to measure a seating depth of the prodgy a few thou from touching with the max load there might be over pressure.
Should I work my way up from a minimum load to account for the possibility of this happening?

adamsgt
05-07-2013, 11:16 AM
No I'm not kidding.

I don't want to push the prodgy to fast ( if at all possible ) so that the pressure is excessive or the barrel gets prematuerly warn.

I am concerned if I use the hornady oal gauge to measure a seating depth of the prodgy a few thou from touching with the max load there might be over pressure.
Should I work my way up from a minimum load to account for the possibility of this happening?

First, seating off the lands is not going to be the source of high pressure. Working up from a minimum load is always a good idea so you can check for excessive pressure signs.

Second, prematurely warm in comparison to what? I'm sure you'd blow up a barrel before you melt it.

Last, does "prodgy" represent a diminutive form of projectile?

Wilbur
05-07-2013, 01:43 PM
Relating muzzle velocity to chamber pressure in the context described doesn't seem appropriate. Certainly, there is a correlation, but the variables involved cast a dangerous atmosphere. Please note that the term "potential" was not used.

Turn off the chronograph and determine your max load using the pressure signs the case exhibits. That is your max load with that specific lot of powder, bullet, seating depth and primer. Doesn't matter in the least what the MV is - that's the max load.

Aussie_Shooter
05-12-2013, 09:49 AM
First, seating off the lands is not going to be the source of high pressure. Working up from a minimum load is always a good idea so you can check for excessive pressure signs.

Second, prematurely warm in comparison to what? I'm sure you'd blow up a barrel before you melt it.

Last, does "prodgy" represent a diminutive form of projectile?

So if I understand you correctly the maximum load is dependant on the effect on the case rather than specific numbers?

Prematuerly warn compared to average barrel life

Yes prodgy is known in some parts of the Australian shooting slang for projectile

Aussie_Shooter
05-12-2013, 09:58 AM
Relating muzzle velocity to chamber pressure in the context described doesn't seem appropriate. Certainly, there is a correlation, but the variables involved cast a dangerous atmosphere. Please note that the term "potential" was not used.

Turn off the chronograph and determine your max load using the pressure signs the case exhibits. That is your max load with that specific lot of powder, bullet, seating depth and primer. Doesn't matter in the least what the MV is - that's the max load.

Thanks Wilbur

How many rounds should I test of each specific powder load before that sample is deemed acceptable?

Also what would be a reasonable powder weight jump (e.g. 0.2 gr, 0.5 gr etc)?

Aussie_Shooter
05-15-2013, 08:30 AM
Anyone?

alinwa
05-16-2013, 02:07 AM
OK :)

Take 5 brand new cases and load them to you current 'max' load, load and fire them 5 times.
Write down velocity of each round fired.

-are the primers still tight?

If they are, go up 1/2 grain and do over.....velocity should be a little higher, WRITE IT DOWN!

-are the primers still tight?

Keep going up until you get loose primers
This VELOCITY is over-max for YOUR in this gun/barrel/setup.
Once you've loosened the primers, throw those cases away, (((or,
if you're a COMPLETE tightass like me, seat the primer with a
cigarette paper and slop fingernail polish around the joint, load
with a moderate varmint load and bring it hunting, eject it into the bush!)))

Back down one full grain, check velocity and check the primers....




YOUR MAX VELOCITY, regardless of any book, any guesstimate from some feller on the innertube, any formula or software program, any app or download, is 1 grain below where your primers get loose. Now, the reason you need to write down the velocity is because velocity is the result of pressure. (You will get guys who argue this point, ignore them unless you're willing to burn up several barrels TESTING this concept) and pressure varies with temperature, soooooo....... IF you're going to play around with MAX loads you MUST understand that PRESSURE CHANGES WITH TEMPERATURE!!!!!

Write that down

Those loads you worked up in July may just LOCK YOUR GUN UP in December!!!

MAXIMUM LOADS ARE TEMPERATURE SPECIFIC


You MUST find your maximum velocity and then you MUST stay well below it whether it's 0 degrees or 30 degrees outside

If you can't/aren't willing to/won't test this stuff for yourself, stay away from maximum loads. For a maximum year-round load work up to loose primers and back off 2 full grains, this SHOULD keep you out of trouble thru the year.





Here's what I ask my Hunter Ed kids....

"What's the difference between this 243 cartridge and a hand grenade?"

Answer

"You'll probably never detonate a hand grenade 8" in front of your right eye!"



And BTW, to answer your question within a question, I jump 1/2 grain increments when using a powder thrower (measure) for a bunch of reasons, the main one being that you are fooling yourself if you think your measure can advance in .2gr increments, it can't. If you want to get serious about this then get a 500.00 scale and weigh your charges, graph EVERYTHING for velocity and weigh down to the kernel of powder and you might re-adjust your max a little tighter..... meantime just fuh'geddaboudit, stay away from max. FIND IT, scientifically FIND MAX, and then back off.... Go up and when primer pockets loosen, BACK OFF!

The case is your gauge, when it fails, YOU'RE DONE :) back the load down

and if you want to predict WHEN the case will fail, use a chronograph.

And BTW this is scientific. It's the RIGHT way to do it. You can read books, you can talk with "techs," you can talk with people who work at large reloading/testing facilities, you can learn about CUP's and LUP's and PSI's and test cylinder plunger setups......you can learn about strain gages, you can BUY strain gages, you can buy a strain gage/oscilloscope setup if you so choose.....you can buy a blade mic and "measure for casehead expansion" but in the end you will learn that THE MOST ACCURATE method of measuring is gauging. Which is exactly what you're doing with those primer pockets....


YOUR gun, YOUR sizing method, YOUR chamber/headspace/tenon/lube/case phizzick and YOUR primers/powder/bullets will tell you the story.


Loose Primers=Too Hot

The End

al

Wilbur
05-16-2013, 03:03 AM
Your rifle may have extraction issues well below loose primers. You'll know when something is haywire. Work up slow to save yourself significant problems such as stuck cases and broken bolt handles. I had a 6mm/06 that operated just fine (could still open the bolt) but a half grain more blew out the primer and locked the bolt. It was telling me to stop all the while....

If you don't have problems up to alinwa's loose primers then yes, stop there and realize that anything you change is cause to reduce the load and take a slow look up.

Hunter
05-16-2013, 09:55 AM
Those loads you worked up in July may just LOCK YOUR GUN UP in December!!!

Good post, al. I assume the July/December example does not apply in "our" neck of the woods?

alinwa
05-17-2013, 12:16 AM
Good post, al. I assume the July/December example does not apply in "our" neck of the woods?

LOL!

dude's an Ozzie eh...... up here where we stand up and hang down it's of course reversed......

(how's that for obfuscatory politicospeak?)

In other words, AGREED :)

al