I'm loading for a 308 win bolt action hunting rifle with a 16" barrel. Obviously I want to maximize my fps since I'm dealing with such a short barrel. I ran a ladder today with Lapua LRP Brass, Varget 42.7-44 grains in .3 grain incrimints (5 shots per charge), and 180 Berger EH. Gordon's tool shows me at 64,000 psi, 2500fps, at 44 grains. I see zero signs of pressure at 44 grains but I was getting very similar velocities to what GRT said I would get. Do I trust what the Brass and gun are telling me or trust GRT?
When is hot too hot?
- Thread starter leclairk
- Start date
44 grs of Varget is a pretty hot load, and it's over 100% useable case capacity. The issue I'd have with such a hot load is that it tends to produce pressure above the SAAMI max of 62,000 psi, which is not necessarily a problem when no pressure signs are showing, BUT. . . that pressure can increase quickly to dangerous levels from there when higher summer ambient temperature come along. IMHO, 44 grs of Varget is too hot for a .308 hunting rifle.
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Why ask us? If GRT predicted it, and your numbers coincide, then it's likely to be accurate.
You're ~5% over recommended SAAMI maximum pressure for the cartridge.
If you want to gamble with your eyes, face and hands, go ahead. I'd recommend that you make sure your insurance is current.
If you're not showing pressure signs, you may be lucky, or it's just that your chamber and leade do not cause pressure spikes.
In my experience, too frickin' hot is when your primer blows out, you flow brass into the bolt head, and you have to hammer the bolt out of your action.
You're ~5% over recommended SAAMI maximum pressure for the cartridge.
If you want to gamble with your eyes, face and hands, go ahead. I'd recommend that you make sure your insurance is current.
If you're not showing pressure signs, you may be lucky, or it's just that your chamber and leade do not cause pressure spikes.
In my experience, too frickin' hot is when your primer blows out, you flow brass into the bolt head, and you have to hammer the bolt out of your action.
Jager
Gold $$ Contributor
Modeling tools like GRT or QuickLoad are very accurate at predicting pressure if - big if - they're used properly. The two big keys being that an accurate chronograph is being used and that the load variables (powder type, powder lot, case capacity, etc.) have been calibrated such that the actual velocities are married up with the software.
It's important to remember that classic pressure signs - all of which involve metallic failure of one sort or another within the cartridge case - don't instantly arise the moment you cross the SAAMI/CIP pressure spec maximum. It'll be quite some thousands of psi before that happens. Doesn't mean you're not over pressure. Just means you're not seeing it.
Lots of guys, myself included, are quite happy to knowingly build a load that is at maximum or even somewhat above. But hot rodding a heavily built competition gun with very tight tolerances is different from doing so in a field gun which is both more susceptible to over pressure woes and where the consequences of weapon failure are much higher.
Handy is nice. But stuffing more powder in to make up for a very short barrel probably ain't the best idea.
It's important to remember that classic pressure signs - all of which involve metallic failure of one sort or another within the cartridge case - don't instantly arise the moment you cross the SAAMI/CIP pressure spec maximum. It'll be quite some thousands of psi before that happens. Doesn't mean you're not over pressure. Just means you're not seeing it.
Lots of guys, myself included, are quite happy to knowingly build a load that is at maximum or even somewhat above. But hot rodding a heavily built competition gun with very tight tolerances is different from doing so in a field gun which is both more susceptible to over pressure woes and where the consequences of weapon failure are much higher.
Handy is nice. But stuffing more powder in to make up for a very short barrel probably ain't the best idea.
Jager said,
"But hot rodding a heavily built competition gun with very tight tolerances is different from doing so in a field gun which is both more susceptible to over pressure woes and where the consequences of weapon failure are much higher."
This cannot be overstated while reading this site.
May I ask what GRT stands for?
An abbreviations page would help dummies like me.
"But hot rodding a heavily built competition gun with very tight tolerances is different from doing so in a field gun which is both more susceptible to over pressure woes and where the consequences of weapon failure are much higher."
This cannot be overstated while reading this site.
May I ask what GRT stands for?
An abbreviations page would help dummies like me.
Gordon's Reloading Tool.
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Your risking your eye sight and perhaps more. Why did you want a 16" barrel in the first place. If you dropped 100 or 200 fps it wouldn't reduce the ability to kill a deer. If you get a carbon build up the pressure will build up slowly and get worse.
I never understood why anyone would want a 308 with a 16" barrel then compound the issue by selecting 180 grain bullets unless they like getting punched around by Mike Tyson. Also, the 16" barrel limits the velocity and ability to burn the powder completely. In addition, save your money for a hearing aid, you'll need one if you keep shooting that rifle.
You stated the purpose is a "hunting rifle". If it is deer hunting, a 125-grain bullet would be a better choice with a faster powder such as IMR 4895. Nosler 125 BT's or Hornady SSTs would be a good choice.
I also don't understand why anyone would push the pressure envelope especially for a hunting rifle. A 308 loaded to moderate pressure levels is enough for most game that this caliber is designed for in North America. Most certainly it is enough for white tail deer.
You stated the purpose is a "hunting rifle". If it is deer hunting, a 125-grain bullet would be a better choice with a faster powder such as IMR 4895. Nosler 125 BT's or Hornady SSTs would be a good choice.
I also don't understand why anyone would push the pressure envelope especially for a hunting rifle. A 308 loaded to moderate pressure levels is enough for most game that this caliber is designed for in North America. Most certainly it is enough for white tail deer.
Why?
Why push the load to the brink of disaster?
If you are shooting game just a few fps won't make a difference in recovering the game or not. If you are shooting targets all that matters is the bullet goes where you aim.
Military sniper's lives depend on the rounds going down range to do there job, they aren't hotrod rounds! They are carefully made ammunition, made using the best practices available.
Why aren't you doing that instead of pushing the ammunition and rifle to the limit?
Crop sprayer pilots push the envelope of the airplane and the edge of their skill so much that many of them crash. Is that what you want to do is crash? Back off to a sane load and practice until you get the rounds on target to your satisfaction!
Paul
Murray Brook
Silver $$ Contributor
How many firings with that load do you have on your brass. Case life and primer pocket tightness are a good indication of over pressure loads. JMO
It helps to understand that the SAAMI pressure rating is for ammunition manufactures to use to ensure that the ammunition will be safe in all guns. Things don't magically fail at 62,001 psi. Unfortunately we have no way to measure pressure other than to note when some component is reaching a point that its physical appearance indicates it is at or beyond its pressure limit. By design the case or the primer are going to fail before the action and it is likely that those failures releasing hot gasses are going to cost someone their eyesight or result in hand injury.
GRT is only a guide, use it as it's the only available tool you have to estimate pressure.
GRT is only a guide, use it as it's the only available tool you have to estimate pressure.
Thanks for the info guys. This is exactly why I asked. It’s a long story on why I have a rifle with a 16” barrel but I love the thing. I know it’s less than ideal but it’s light, deadly accurate, and a joy to shoot. I will drop the charge and also look at lighter bullets. This is a good reminder not to push the envelope on this stuff. Thanks again.
No point in going wild with a 308 at all. How many deer were harvested with black powder 30-30 and even the 25-20? Gobs of them is the answer.
I can’t speak for all, I’ve never had a max load in any caliber do well accuracy wise. Around 70-90% book loads have showed best accuracy in factory rifles and pistols. Full custom stuff has been mostly the same, some doing better lower in the charge weight range, but never a max load. I’m sure others exist who have had best accuracy over max book loads.
But, that’s the cool thing of reloading, you find what works best for you, not what a factory makes only.
I can’t speak for all, I’ve never had a max load in any caliber do well accuracy wise. Around 70-90% book loads have showed best accuracy in factory rifles and pistols. Full custom stuff has been mostly the same, some doing better lower in the charge weight range, but never a max load. I’m sure others exist who have had best accuracy over max book loads.
But, that’s the cool thing of reloading, you find what works best for you, not what a factory makes only.
DirtySteve
Gold $$ Contributor
I learned my lesson on short barreled rifles. I thought a 20" 300 WSM would be awesome. It shot awesome but was a 308 that consumed a lot of powder.
NZ_Fclass
Silver $$ Contributor
My only experience of a short hunting rifle was a 303 Jungle Carbine (No 5 rilfe) with an 18in barrel. Shot fine with 174g Hornadys at around 2300fps and nothing walked away from being shot. Great in the NZ bush where shots were always under 200 yds, normally 50 yds. For open country - 7x61 S&H with 160g.
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