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300 WSM bullet choice - T3 Lite

 
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  #8  
Old 05-15-2013, 08:36 AM
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Re: 300 WSM bullet choice - T3 Lite

DDB, Most welcome and welcome to LRH!

I think you might be overthinking it a little but who knows. Speed of sound is actually closer to 1,100 fps. The pressure and velocity of a particular load of powder and bullet will detrmine the barrel's harmonics and other things that affect the equation are type of brass, primer, bullet seating depth, length of throat, temp to name a few. All these will affect pressure and velocity which can and will affect accuracy and/or POI. This is why I am a little skeptical that a program could account for all these parameters. But if you're having sucess with it, that certainly is interesting.

I have found that heavier, stiffer barrels tend to be less affected by harmonincs or at least that's the impression I have based on my experiences with a couple of Senderos I owned. They shot most everything very well and were not fussy about loads. POI would shift slightly between loads which is a harmonics thing.

The way bedding affects harmonics is to keep it consistent from shot to shot. If your action has stresses on it or shifts around in the stock when fired that will induce inconsistencies. Bedding may be old school but you'll find that almost all precision shooters bed their actions to their stocks. It works.

On bullets, Game Kings should work well (never used them). They are like a lot of cup and core bullets and can be frangible which isn't all bad as they tend to do more damage and probably disable and kill a little quicker. That said, for short range shooting I like something like the E-Tip which is tough and holds together and will do a better job smashing through heavy bone, penetrating deeply and exiting. Partitions used to be my bullet of choice before LR hunting and i killed a lot of critters with them but I hated the way their tips deformed in the mag box. They still seemed to shoot well at short range anyway.

Here's some pics of E-Tips I recovered from my 300 RUM behind 400 and 500 yd targets. You'll note they have a flat vs rounded frontal and wide. They were shot into partially frozen gritty ground which is why one is missing part of a petal.
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  #9  
Old 05-15-2013, 11:11 AM
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Join Date: Feb 2013
Posts: 5
Re: 300 WSM bullet choice - T3 Lite

Mark, thanks for the excellent reply! I know it took a while to create, and I appreciate it.

I was not familiar with the E-tip, and I will definitely be looking into it.

I have shot both the standard 180 grain Partition Soft Point and the 180 grain Partition Protected Point. The 180 gr. Protected Point was designed to address the problem of tip deformation in magnum magazines which you spoke of. But it has a lot lower BC, only .361 compared to the regular partition's .474. It has a slightly more forward bulge to its ogive, different profile, and a flatter tip.

Left to right, the Partition Protected Point next to a regular Partition, and a regular Partition that has been through the recoil of my rifle in its (plastic!) magazine, and has its tip all smeared around.


The felt bedding I was referring to was actually bedding in forends which firmly touched the barrel, not action bedding. I've seen some old english rifles with it, and my old Ruger M77 has some felt between the forend and the barrel too. I think its purpose was to dampen those waves, which are probably the same thing as what you are calling the harmonics.

THe Quickload program actually allows you to change its default value for pretty much everything - such things as case capacity, cartridge COAL, bullet length, etc. So, if you change brass and the lapua has 2 grains more case capacity, you can change that value. There is even a sort of "fudge factor" you can play with to adjust the program's predictions to the actual range performance you are getting. You can even modify the powder data files with all sorts of exotic stuff dealing with burn rate and several other factors. It was written by a German powder engineer and was originally for modeling new light antiaircraft cannon shells! It has preset data (which can be modified) for every bullet i have ever looked for, literally hundreds of bullets from every makerr you ahve ever heard of and a few you havent; about 200 cartridge files preset for COAL, case capacity, max. pressure, etc; and data for every powder made in the world. It is really remarkable what you can do with it.
For example, when I was wildcatting the .30-25 WSSM, I actually modified the 25 WSSM data file to handle a .308 bullet, with same COAL and correct shoulder angle and neck length for my chamber. I got .30-06 +P velocities with short to medium length bullets up to 180 grain, out of an AR15 lower. It was a heck of a learning experience! There was literally zero data for this wildcat so I had to start from scratch, measuring case capacity after modifying cases, that sort of thing. But the program took me right to the sweet spots. (until the weather got to 105 degrees at the range. That really messed with powder burn rates!)

Science commercial: Believe it or not, the speed of sound varies with the medium it is passing through. In air at sea level with humidity at 70% it is 1100 or so fps. At altitude it is lower. In water it is vastly different, as it is in rock, steel, glass etc.

Whatever, it doesn't matter whether it is a speed of sound in steel shockwave or harmonics or little elves with hammers that make there be accuracy nodes in a given powder/bullet/barrel/temperature setup; what matters is the OBT calculator can direct you to the barrel time best suited for your barrel length, and then QL can give you a range of powders to get there, within safe limits.

Of course so can shooting a ladder, or better yet the Optimal Charge Weight method, which takes into account barrel heating as you go through the test better. A lot easier than all the tech stuff I play with as well! But it keeps me off the streets....

Again my thanks for the tip about E-Tips, and for your advice.

-David
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  #10  
Old 05-15-2013, 01:01 PM
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Join Date: May 2008
Location: South of Canada and North of Wyoming
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Re: 300 WSM bullet choice - T3 Lite

David,

You're right about the speed of sound in different mediums. Didn't think of it as I usually think of it in terms of Mach and atmosphere.

Also glossed ovwer the :barrels" part of the bedding you mentioned, and I have heard of different techniques of bedding barrels or putting pressure points on them to modify the harmonics or vibrations for better accuracy and consistency. I tend to shy away from that as I think that environmental conditions could affect the fore end of the stock and cause inconsistencies in the pressure it puts on the barrel. I have heard it has been used successfully sometimes and I have heard that putting a shim or wrapping the barrel with tape for contact will sometimes correct a poor shooting barrel.

The Quickload program does sound interesting.. still a little skeptical but I might try it someday. For you, I would dismiss the 180's at higher velocities because the program suggests they won't work. I think they are worth giving a try but that's your call and there isn't a lot of difference between 165 and 180.

You mentioned KE as part of your critieria for choosing. I think it can be a little missleading because velocity (squared) is is a much more significant part of the equation than mass. I put a little more weight on momentum than KE.

For short range hunting (less than 500 yds), E-Tips are my first choice because of their tough construction. They are made of guilded metal which is tougher than the copper Barnes mono's. When they expand they produce a wide flat frontal than any other bullets I know, which produces more shock, trauma and a wider wound channel. And comparing to the Partitions, they have a tough trauma resistant tip and higher BC.

For LR work, my 2 first choices are Cutting Edge and Berger bullets for BC and down range expansion. I'll shoot whichever one of those i think will give me best overall down range results with emphasis on accuracy.

Keep us posted on your progress.

Cheers
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You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams
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  #11  
Old 05-15-2013, 10:38 PM
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Join Date: Feb 2013
Posts: 5
Re: 300 WSM bullet choice - T3 Lite

Thanks for the answers, Mark. Will do!


-David
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