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your probably right. I know I'll never compress loads that hard again. If the volume is about 2.5 grains of water difference between brass then would it stand to reason that max charges would be about 2.5 grains different in the different cases?
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Campfire 'Bwana
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Campfire 'Bwana
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I've never compared grains of water to grains of powder.
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Campfire Ranger
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Campfire Ranger
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Fine,
But you won't safely fit 308 loads in 300 Savage brass even if you can conjure the most "silly" freebore on the planet either, despite very little length and volume differences. The volume does matter.
Weatherby freebore is built into the throating itself, not by making the case volume less and seating the bullets deeper, it is effectively using more fuel to begin with.
It is true that seating deeper to a point can decrease pressure with that freebore, especially if you are very close to the lands or contacting close to the throat. Room to expand is not a bad thing.
A little test on reducing capacity, and why rifles are slightly different because of powder, but are the same because of volume.
(For example purposes only)Take a non-compressed load, then take the same load and fill with a filler (I like Dacron) from powder to base of bullet; slightly compressed to fill the space. Which gives higher pressure? You have added no weight and no resistance; you've just made your case volume less, or made your "bullet" seat deeper without the weight/resistance.
In reality, there is a happy medium between seating too deep or jamming the lands; both of which I believe can cause pressure issues if taken to extremes.
The poster may have gone to an extreme, and it sounds as if jamming the lands isn't it.
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Joined: Aug 2006
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Campfire Greenhorn
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Campfire Greenhorn
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One may download following graph regarding seating depth from ATK: http://le.atk.com/pdf/357_SIG_Setback_Length-vs-Pressure.pdf
"A stupid man's report of what a clever man says can never be accurate, because he unconsciously translates what he hears into something he can understand." Bertrand Russell
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Don't know how many have heard of or seen Stan Watsons book "A Handloaders Odessey". He does alot of pressure testing with a 30-06 and writes about different bullets, powders, temps, seating depths you name it with a huge array of 30-06 combo's. Here is a pic of a graph from the book...hope this isn't infringement....about seating depth with a 180 hornady. BTW....I found this book well worth the money for my reloading library. ![[Linked Image]](http://i672.photobucket.com/albums/vv88/kraky11/DSC00685.jpg)
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One last comment about the graph compared to early posters results with monolithic bullets near the lands...I think they are possbibly a science unto themselves.....I think they need a running start vrs being started by the lands....probably a much bigger increase in pressure compared to jacketed.
Last edited by kraky111; 10/13/09.
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Campfire 'Bwana
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Campfire 'Bwana
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your probably right. I know I'll never compress loads that hard again. If the volume is about 2.5 grains of water difference between brass then would it stand to reason that max charges would be about 2.5 grains different in the different cases? QL lists 54.6gr H20 capacity at 105% with 45gr Varget/165gr SST 57.7gr H20 Capacity at 98.7% with 45gr Varget/165gr SST
Give a man a fish and he eats for a day. Give a man a welfare check, a forty ounce malt liquor, a crack pipe, an Obama phone, free health insurance. and some Air Jordan's and he votes Democrat for a lifetime.
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Campfire Tracker
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OP
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your probably right. I know I'll never compress loads that hard again. If the volume is about 2.5 grains of water difference between brass then would it stand to reason that max charges would be about 2.5 grains different in the different cases? QL lists 54.6gr H20 capacity at 105% with 45gr Varget/165gr SST 57.7gr H20 Capacity at 98.7% with 45gr Varget/165gr SST Just need a little more explanation on what this is saying. Thanks.
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Joined: Dec 2002
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Campfire Ranger
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Campfire Ranger
Joined: Dec 2002
Posts: 25,933 Likes: 6 |
Fine,
But you won't safely fit 308 loads in 300 Savage brass even if you can conjure the most "silly" freebore on the planet either, despite very little length and volume differences. The volume does matter.
Weatherby freebore is built into the throating itself, not by making the case volume less and seating the bullets deeper, it is effectively using more fuel to begin with.
It is true that seating deeper to a point can decrease pressure with that freebore, especially if you are very close to the lands or contacting close to the throat. Room to expand is not a bad thing.
A little test on reducing capacity, and why rifles are slightly different because of powder, but are the same because of volume.
(For example purposes only)Take a non-compressed load, then take the same load and fill with a filler (I like Dacron) from powder to base of bullet; slightly compressed to fill the space. Which gives higher pressure? You have added no weight and no resistance; you've just made your case volume less, or made your "bullet" seat deeper without the weight/resistance.
In reality, there is a happy medium between seating too deep or jamming the lands; both of which I believe can cause pressure issues if taken to extremes.
The poster may have gone to an extreme, and it sounds as if jamming the lands isn't it. Hawk, you make some good points here. But consider, if you will, what would happen if you tried firing a 308 with a 150 gr bullet over 4350 in a smooth bore barrel. I believe, but can not prove, the pressure would never become high enough to properly burn the slow rifle powder. That is not true of faster pistol powders. In a pistol cartridge, the actual combustion chamber is inside the case, behind the bullet as it is seated. In a high power rifle with slower powders, I believe, the combustion chamber is actually the entire volume of the brass case as well as the first couple or three inches of barrel. I believe the bullet actually engages the rifling before chamber pressure and temperature reach anywhere near maximum. That is why a bullet which reaches resistance early in its motion will spike pressures. It reduces the size of the combustion chamber early in the ignition cycle and causes the powder burn rate to climb at a faster rate. Chamber pressure is a true indication of combustion temperature. And we were taught in Chemistry class that a ten degree Celsius temperature increase will double the speed of reaction. So any increase in chamber pressure early in the combustion cycle will greatly increase speed of combustion through the entire cycle.
People who choose to brew up their own storms bitch loudest about the rain.
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Update on my issue with the LC match brass and 45 grains Varget with 165 GMX's.
1. I pulled bullets and tried to load empty brass in action. 2/3rds of brass from base upward was slightly scuffed and bolt closed very stiffly. I measured with Hornady Headspace guage and found I didn't resize brass small enough to cycle easily.
2. If brass has no room to expand, will that affect pressures?
3. Could it just be that the brass was stiff to clamp down on before firing and that just made it tougher to open the bolt once it was fired. Not neccessarily the pressure being excessive but rather the brass just not being sized down enough that made it hard to lift the bolt? Is any of this line of thinking on track? What say the experts?
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Campfire Tracker
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My experience:
New brass seems to make less pressure and velocity than brass that is formed to fit the chamber even though it has less capacity. The reason being that energy seems to be spent expanding the case on "ignition". (Or so it has been explained to me). For me fireformed brass usually needs about .5 grains less powder to make the same vel as new brass.
RE: close sizing making it difficult to extract my answer is YES!
I recently aquired a forster bump die. It sizes the neck and bumps the shoulder. Brass will chamber like butter after one sizing but with warm loads I do get extraction problems. I don't notice trouble lifting the bolt so much as pulling it back. On this brass I can see what I think are "rough impressions" left by the chamber walls.
On most of my guns I see extractor circles on the brass before I get trouble with bolt lift. Did you see extractor marks on your brass as part of the diagnosis??
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I didn't see any extractor marks on the brass (not that I know of). Would it be a circle mark? It's a kimber montana. Primer pockets weren't loosened and no cratered primers. Just very difficult to lift and pull back bolt. It may have just been the brass wasn't resized enough to begin with.?
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Campfire Ranger
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Campfire Ranger
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Not being there and not seeing with my own eyes, I would guess you are right on the money with answer number three.
If you are really jamming the cartridge into the chamber, then yes it will be a bit difficult to extract that same brass.
Does your resized brass chamber easily before adding powder and seating the bullet?
If so you may well be expanding the sides of the case as you compress the powder charge. I have managed to do that on occasion in the 30-06 with super slow stick powders. The answer would be a move to a powder which uses a lighter charge weight.
If your newly sized cases (without powder and bullet) do not chamber easily. The answer is even easier. Try adjusting the die into the press a little deeper until your resized brass chambers easily.
If it is not possible to make your brass chamber easily with your present die, then a small base resizer may be in order.
People who choose to brew up their own storms bitch loudest about the rain.
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The more feedback I get the more I realize the probable reason for difficult bolt lift and extraction was that I didn't resize my once fired LC match brass fully enough. And I think 45 grains of Varget in those cases with 165gmx's is probably pushing a little too hot and certainly compressing powder a little too much (much moreso the 46 grains I loaded but didn't shoot). After pulling the bullets, the brass didn't chamber without a significant amount of pressure to close the bolt. Chalk it up to my inexperience with once-fired brass bought from someone else.
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Campfire Ranger
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Campfire Ranger
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Idaho has you pegged at number three; I totally agree with him!
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