Nomosendero
Well-Known Member
Shawn, what would the estimated muz. velocity be for the new 250Accubond in a 26" factory RUM & a 30" Edge? I think this might be a great bullet for me, my max. range would be somewhat shy of yours.
.338 rum vs .338 edge
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Long Time Long Ranger
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AJ, I did quite a few of these years ago when the first ultras came out. All were in 26, 28 and 30 inch barrels. This cartridge gains very little in fps per inch of barrel. Naturally a longer barrel gives you the odds of more velocity but the individual barrels had about as much impact as barrel length since there just wasn't much gain as you added length. In other words I had some 26" tubes just as fast as some 30". I would say on average this cartridge would gain maybe 50 fps per 2" of barrel length tops. So a 30" tube should get a guy about a 100 fps extra, but then the next guy gets a hot 26" barrel and outshoots the 30". In other words a 100 fps variance in identical length barrels is not uncommon depending on rifling, throat, chamber cuts, tight necks, etc.
That 300 wby I mentioned is the most amazing thing I have ever seen. Maybe Shawn figured that one out in his proprietary patent. Straight up I can not see a 338-300 ultra shooting with a 338-378 which will average the 2950 fps mentioned. If he can do it I am getting one and replacing the big gun. The ones I did averaged more in the 2700-2800 fps range without getting way to hot. I haven't worked with the straight 338 ultra. I have worked quite a bit with the Lapua which averages slightly higher fps than the 338-300 ultra. Particularly the improved Lapua's.
I know Dan Lilja did a test with a 338-378 wby 12-15 years back starting with a mid 40's" barrel and sawing it off in I believe 2" increments after each ten shot spread. All of the loads were as identical as he could get them and the gain was not very much on average. At one time the rifle shot just as fast with a 4" shorter barrel. I wish I could remember that test better but it was years ago. I just remember the bottom line of not much gain. Seems to me he got about 35fps per 2" of length on average, but at some lengths there was virtually no gain and that was right in that 26-32 range I think.
To the contrary of that I have seen some way overbore wildcats of mine get up to 125 fps per 2" of barrel. 6.5-8mm rem mag for instance. In past years I had a lot of fun really getting into this stuff trying to find that majic golden calf. I realize now the golden calf is in the barrel. You can look at the cartridge and design of it and figure very accurately what velocity range it will hit in with max pressure. Until you get one like the golden calf barrel 300 wby I got. I wish that barrel was 30" I would rechamber a 30-338 lapua improved or similar in it and have the most awesome 30 caliber around.
That 300 wby I mentioned is the most amazing thing I have ever seen. Maybe Shawn figured that one out in his proprietary patent. Straight up I can not see a 338-300 ultra shooting with a 338-378 which will average the 2950 fps mentioned. If he can do it I am getting one and replacing the big gun. The ones I did averaged more in the 2700-2800 fps range without getting way to hot. I haven't worked with the straight 338 ultra. I have worked quite a bit with the Lapua which averages slightly higher fps than the 338-300 ultra. Particularly the improved Lapua's.
I know Dan Lilja did a test with a 338-378 wby 12-15 years back starting with a mid 40's" barrel and sawing it off in I believe 2" increments after each ten shot spread. All of the loads were as identical as he could get them and the gain was not very much on average. At one time the rifle shot just as fast with a 4" shorter barrel. I wish I could remember that test better but it was years ago. I just remember the bottom line of not much gain. Seems to me he got about 35fps per 2" of length on average, but at some lengths there was virtually no gain and that was right in that 26-32 range I think.
To the contrary of that I have seen some way overbore wildcats of mine get up to 125 fps per 2" of barrel. 6.5-8mm rem mag for instance. In past years I had a lot of fun really getting into this stuff trying to find that majic golden calf. I realize now the golden calf is in the barrel. You can look at the cartridge and design of it and figure very accurately what velocity range it will hit in with max pressure. Until you get one like the golden calf barrel 300 wby I got. I wish that barrel was 30" I would rechamber a 30-338 lapua improved or similar in it and have the most awesome 30 caliber around.
To increase velocity at the same pressure as the velocity increases at 1/4 the increase in powder capacity. In other words a 10 percent incresae in powder capacity will increase velocity two and one half percent percent..
AJ Peacock
Well-Known Member
Interesting, seems to work for a 308 and 30-06. Based solely on that, there should only be 40-50fps difference between the RUM and the Edge. That relationship is new to me, thanks. Where did you find it?
Merry Christmas
AJ
Lost creek
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I talked to a tech guy at nosler bullets the other day about the b.c. of the 250gr accubond,he told me it is .575. IF I am correct about the velocity loss of 175-200fps.going from the 225gr.accubond at.550 b.c.to the 250gr. accubond at .575b.c.,accordingto my ballistic program the 250 is a step backwards in drop,wind drift and energy.
Desert Fox
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Me too, I believed it's in the barrel. My 308 with 25" Pac-Nor 3 grove - 12 twist will push the 155 Scenar at over 2900 with only 44.8 grain of Varget, when everybody else is using 46 grain or more to get to 2800.
Nomosendero
Well-Known Member
wow, thanks for the info guy's, I'm currently looking at buying the remington 700 338rum or having a 338 edge built. Right now I'm just learning with my 308 savage and 22-250m77 but I'd like to get a bigger rifle soon. this site is great and I'm learning a ton.
Shawn Carlock
Sponsor
JWP,
Your formula is close to what I have seen as long as the increased capacity is used with the same powder. Sometimes a small increase will allow use of a different powder.
Update on my project - we just shot some loads in the high 2900's (two rounds went 3007 & 3003 fps). These round shad slight ejector marks, a bit more pressure than I want to run, but the bolt lift was not sticky or different to feel in any way. We shot a group in the 2970's and no ejector marks what so ever. This mod is also going to allow us to use a couple different powders no able to use before. I am testing these for ES and temp sensitivity. If they pass those tests I expect to pick up another 20-30 fps in that switch. 2950-2980 FPS should be the norm if all works well. Still alot of testing to do before I will consider it a successful project. Keeping my fingers crossed.
Your formula is close to what I have seen as long as the increased capacity is used with the same powder. Sometimes a small increase will allow use of a different powder.
Update on my project - we just shot some loads in the high 2900's (two rounds went 3007 & 3003 fps). These round shad slight ejector marks, a bit more pressure than I want to run, but the bolt lift was not sticky or different to feel in any way. We shot a group in the 2970's and no ejector marks what so ever. This mod is also going to allow us to use a couple different powders no able to use before. I am testing these for ES and temp sensitivity. If they pass those tests I expect to pick up another 20-30 fps in that switch. 2950-2980 FPS should be the norm if all works well. Still alot of testing to do before I will consider it a successful project. Keeping my fingers crossed.
Agreed, I just spoke with Nosler today regarding the same issue, but forgot to get the bullet length. I wanted to confirm the BC as .575.
I spoke with Shawn Carlock on the phone a few weeks ago, he was very helpful in answering my questions, if i weren't doing this myself he'd build my .338 Edge.
Anyhow case capacity was brought up referencing quickload, and I figured I'd share my recent unfired measurement using remington brass. Filling the case LEVEL with a new CCI 250LRM primer pressed all the way in netted me 115.2 grains water capacity. Using the overflow method I got 116.0.
The argument between the .338 rum and .338 edge seems to be settled, someone else out there is making the equivalent of a .338 Edge with .338 RUM width dimensions (fire form required). That to me seems like a better argument in regards to a negligible gain. Thanks for the insight!
