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I looked in my books and on Hodgden's site and a 55 grain Nosler boat tail loaded max with 48.5 gr of IMR 4007ssc shows 3834fps with a CUP of 48.300. That's flat out hauling a$$!!! Will the bullet work on coyotes at that speed? Keep in mind I have no intention of jumping right up to the max load, I just saw that and was floored
 

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It's been a few years since I've done much 6mm loading, but my findings with the 55gr Ballistic Tip is that they're a very thin jacketed bullet and you might wind up "blue-streaking" them if you load up that high.
I didn't have a chrony when I was messing with them but according to the loading data, I was pushing around 3550-3600fps when they started disintegrating in flight. This was with both the 6mmRem and the .243.

The 6mm 55gr Ballistic Tip is more of a prairie dog or woodchuck bullet in the bigger 6mms or more suited for varmints or coyotes out of the little 6mms like the 6x47 or 6mmPPC.
Are your bullets the regular Ballistic Tips (purple tips) or the Varmageddon (black tips)?
The Varmageddon are even thinner jacketed than the regular BTs. I've never used em so I don't know what velocity limits they might have.

The best yote load I had for those two cartridges was the 75gr Sierra HP. Pushed by IMR4320 to 3350-3400fps, this was a very accurate bullet in several rifles I had in both .243 and 6mm. My lefty 788 6mmRem would do one-hole groups with the 75gr Sierra & 4320 at 100yds and it stayed sub-1" at 200yds. It would hammer dogs out to 400yds easily if I did my part.
My other favorite .243 yote load was the plain old Winchester bulk 100gr SP running @ 2900fps. It would drill right through coyotes with minimal expansion so it would poke two holes in the hide. BUT, there was enough energy transfer that it would anchor a dog with no problems.
It didn't tear up the hides very bad either. I've always preferred that to a super explosive bullet that is supposed to grenade inside the dog since I have had those thin-jacketed bullets blow up on the hair and just leave a surface wound. Yotes have good thick pelts in the winter time so this was pretty common for me with both the .22-250 and the big 6mms.
 

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Neck that .243 down to .224 and you have a wildcat called a "Cheeta" and with 55 gr bullets 4,000fps is possible. Just saying FYI....

Regards, Kirk
 

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Discussion Starter · #4 ·
the rifle in question is a Remington 700 ADL made in 1966 (I called them). It is a good 95% condition so I really, really, really don't want to burn the barrel out of it.
 

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It's not really the hot velocity that will burn your barrel out. That boils down more to powder choice and high pressure loads than just screaming velocity, but mainly not letting the barrel cool between shots while running those hot loads. You can burn a barrel throat with slower heavy bullets too if you run high pressures too.

The .243 has a max spec of 60,000psi or 53,000cup. You're getting kinda hot at 48,000cup but not near the max yet.
The .243 is one of those "overbore" cartridges that has a fairly large case capacity compared to the bore diameter. These are the cartridges more prone to faster barrel wear. But the .243 has been around for quite a few years now and it's not really notorious as a burner. It's not the most efficient cartridge but there are many other overbore cartridges that are worse offenders.

If those 55grs work good out of your rifle, give them a try. If you're hide hunting though, I would suggest a slightly heavier bullet as I mentioned above. They'll help buck the wind a bit better too.
 

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Discussion Starter · #6 ·
I have not bought any 55's yet. I am starting with 85gr. Sierra Game Kings hollow point boat tail. I'll do a ladder test of both IMR 4350 (42-46gr.) and Varget (37.5-41.5gr) in 0.2gr increments. That should make for a fun day at the range. I may even borrow a led sled to eliminate a large error inducer on testing. My chrono will come along for data logging
 

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Getting that velocity with that charge probably isn't going to happen. Work up a load over hodgdons MAX then it can probably be achieved or surpassed. Hodgdons loads are usually light compared to most other manuals but they produce great accuracy. Their "compressed" loads that I use in my 300 win mag aren't compressed at all from my experience. If you want to see some serious ass hauling check out the 22-243 Middlestead. 5,000+ fps......now that's haulin ass.
 

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I shot the barrel out of a 220 swift years ago in the 1960's. Factory ammo pushed a 40 grain bullet to 4,100 fps. I loaded to about 4200 fps and shot a LOT of prairie dogs. The rifle was a Winchester model 70 and I was dead accurate to 300 yards when it was new. After a couple of years I started missing more times than I hit and thought the scope (9X Redfield) was messed up. Took the rig to a gunsmith and the first thing he did was put a .224 bullet in the muzzle and it dropped all the way to the chamber. He told me I didn't have a 220 swift any more, but he could make it a .243. I didn't have the money to pay for the conversion and sold the rifle and scope.
 

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If the base of the bullet leaves the case mouth, before the bullet seals the bore, barrel life will be shorter.
Agreed. Also, longer bullets are more stable. Are the Varmint Grenades available for .243? Just an idea, i know they are a long bullet in .224, and hold up to the higher velocities. Alot of people are velocity junkies tho, always gotta have the fastest. But the fastest velicities are seldom the most accurate. And youre not gonna miss a coyote due to 3600 vs. 4000fps. I dont care about the numbers, i run them where the rifle want them.
 

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"blue streaking"? New to me, as is the idea that the 55 gr Nosler won't hold up to high velocities.
I shoot 6mm Rem, a 55 gr Nosler B.T. at 4065 fps,(chronyed dozens of times) 5 shot group of .44 at 100 yards benched.
This is my go to load for prairie dogs from my Remington 700 H.B. Varminter.
I have never had one of these bullets come apart except at impact, and I've shot over 3000.
BTW, the barrel is still good too.
 

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Discussion Starter · #12 ·
If the base of the bullet leaves the case mouth, before the bullet seals the bore, barrel life will be shorter.
ahhhh, another tidbit for a newbie such as myself. thank you

I am not quite certain what I want to do with the thing yet. I called Remington this morning and the serial # shows it as a 9.125:1 twist. Once again I show my inexperience by asking if this twist works better with a heavier bullet as compared to a 10:1 or higher.
 

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Agreed. Also, longer bullets are more stable. Are the Varmint Grenades available for .243? Just an idea, i know they are a long bullet in .224, and hold up to the higher velocities. Alot of people are velocity junkies tho, always gotta have the fastest. But the fastest velicities are seldom the most accurate. And youre not gonna miss a coyote due to 3600 vs. 4000fps. I dont care about the numbers, i run them where the rifle want them.
ONLY, if the rifling pitch and velocity impart the right amount of twist.. Longer bullets require more twist than shorter ones. And you can only get more twist with a faster pitch or hotrod velocity, and in some cases a good mixture of both
 

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Re: .243 loads

My 1-10 twist 27" barrel groups best with Berger 90gr hpbt (IMR 4831) or 68 gr Flat base(4350). The longer 88gr VLD not as good but ok. The Sierra 85 gr hpbt #1530 is a good all around bullet in the 27" & 18.5" barrels using IMR 4350 or H4350
 

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the 85 gr sierra is one of my fav 6mm pills.

my all time combo is 107 smks in an 8 twist barrel powered by 4000MR
 

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"blue streaking"? New to me, as is the idea that the 55 gr Nosler won't hold up to high velocities.
I shoot 6mm Rem, a 55 gr Nosler B.T. at 4065 fps,(chronyed dozens of times) 5 shot group of .44 at 100 yards benched.
This is my go to load for prairie dogs from my Remington 700 H.B. Varminter.
I have never had one of these bullets come apart except at impact, and I've shot over 3000.
BTW, the barrel is still good too.
I don't doubt that the 55gr BT will work out of some large 6mms.
I finished using my stock of 55gr BTs in my 722 .244Rem (1:12" twist) They worked very good on prairie dogs in that rifle...but you don't find many slow-twist 6mms anymore unless it's a custom rebarrel or an old-timer.
Do you happen to know the twist rate of your rifle? Was it a 9" or 10" twist, I know the 700s came with both depending on the year of manufacture.
All of mine except that .244 were all 1:9" Remingtons (788, 660, & 700).
The 55gr might work fine in a 10" twist when pushed hard, but my experience with the 55gr BT in 9" wasn't good above 3600fps. They weren't full-blown blue streaks, but I had keyholing and keyholed up shotgun looking patterns on target.
 

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Bindernut...

You mention that the .243 isn't the most "efficient" cartridge; I've heard the term before, but I don't understand what that means. It's been my favorite for about 40 years, and I'd hate to think I've been inefficient in my choice.;)

What does that term mean, in reference to ammunition? To my engineer brain, efficiency would be the inverted ratio of the available energy in a certain charge of powder, to the energy delivered to the target. After all, shooting is simply the process of converting chemical energy (stored in a chemical compound) into kinetic energy (contained in a moving object), then transferred to a target through impulse (kinetic energy absorbed by a solid object). Any engineer despises wasting any energy in the conversion process.:mad:

What would be an example of an efficient caliber, and what makes it so? Is there a way I can measure it myself? With the .243, I find that a 100 gr. SP powered by 32.5 gr RL-15 powder gives a performance that's exceptional, even though it's not the hottest load I could use. But I'm willing to rethink it if I can get better efficiency.:D
 

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rawright,
Efficiency in a cartridge relates to the amount of powder burned to get a certain velocity. As for what is ideal I'm not exactly sure if there is a proper or set definition...I've never seen one myself.
For a certain bore diameter (6mm for an example since 68c15 is talking .243 loads), as the case volume grows you need more powder to fill it and push that same bullet down the barrel. At some point some cartridge cases will get to a point where you'll see you're using more powder to get the same velocity as a smaller case using a smaller charge.

An example would be to compare the 6x47 (6mm-.222Mag), to the .243Win, to a 6mm-.284 all using a 75gr bullet. All use the bore diameter but you'll get 2800fps, 3400fps, and 3600fps. For that small velocity increase over the .243, the 6mm-.284 uses more powder than the .243. If you added the .240Weatherby into the comparision, you will top out at around 3600fps also but are using even more powder.
An extreme example would be something like a .300 H&H size case necked down to the same 6mm. Sure, you will still get more velocity but at the expense of burning even more powder than the .240Weatherby.

The .243 really isn't all that inefficient...but it's right around the break point of velocity vs powder charge (internal case volume).
Also, as you get into larger cases with small bore diameters you'll run into problems with a sandblasting effect from the large powder charge being pushed down the barrel at higher velocities. Over time, this might cause problems with increased barrel throat wear if you shoot hot-n-heavy. that's where you'll see the .243 compared as less efficient than it's parent cartridge the .308. Same internal case volume but necked down to a smaller bore. You will also see this described as "overbore".


If someone would take all the time to plot out the case volume and powder charge versus the velocity gained you can seen when the efficiency drops off. I think software like QuickLoad will also plot out stuff like this but I don't have a copy so I'm not positive.
 

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Thanks, Bindernut! I think we're saying the same thing, more or less, and it would be interesting to plot the curves for various cartridges. I think what I'd see, if I plotted the fps on the vertical and grains of powder on the horizontal, would be a fairly straight line rising from left to right, but rolling off to flat at some point. The more "efficient" the cartridge, the more steeply the line would rise. Smaller cases would roll off faster, too, because the case size would limit the amount of powder possible.

That would actually be a fairly interesting set of graphs, especially for someone trying to select a new cartridge to shoot. To make any sense, each graph would have to use one powder and one bullet weight/style, but display several different cartridges. That would be difficult, since the tables I've seen so far offer only two points for each powder and bullet weight - a starting charge and a maximum charge. It would take a lot of research to fill in enough points to make a meaningful curve.

Oh well, I'll add that to my list of projects to pursue in retirement. In the meantime, I'm enjoying the heck out of my .243 BLR, and looking forward to the .30-06 BAR I have on order, due to arrive in about 4 weeks. :D

Thanks again!
 
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