243 vs 6mm Dasher trying to understand....

[pbreed]

For accurate target shooting....
Trying to understand the technical reasons 6mm Basher seems to be more accurate(popular) than 243 winchester?

Why?
They are so close to being the same cartridge?

Is it all default barrel twist?
Will a 243 with 1:7 or 1:8 be just as good as 6mm Dasher?

Are there additional reasons?

Does the 6 Dasher deal with long VLD bullets better?

Better rifling land engagement?

Alas a a newbe with a first post, if one wants to discuss multiple question better to do multiple posts, or one big multiquestion post?
(Different boards have different cultures about this. seems like this board is mostly single topic.)

 

[spife7980]

Dasher is a shorter, steeper shouldered, more efficient case design. It also has less recoil with 60% of the powder. It’s just easier to shoot well. Brass quality has some play in that as well.
243 can be plenty accurate though.

 

[DownhillFromHere]

The .243 was developed as a hunting cartridge with 80-100 grain bullets out of a 1:10 twist barrel at 3000-3200 fps. The 6BR was designed from the outset as a benchrest cartridge with slightly lower velocities.

As Spife said, the 6BR is more efficient, getting a 90-grain bullet to ~3000 fps with far less powder than the .243. As a PRS cartridge, the BR with long-for-caliber bullets in the 105-grain range at ~2750 fps out of a 1:7 - 1:8 twist barrel offers low recoil and great performance out to 1000 yards or even a bit further.

The 6BR is also going to give better barrel life, assuming one doesn't redline-load rounds for it. One of my shooting buddies says he has 3500+ rounds on his current BR barrel and it's still a match-accuracy hammer. For comparison, a 6 Creedmoor (similar to .243 wrt powder capacity) can be expected to toast a barrel in 2000 or less rounds.

Imo, the only way you're going to get optimal long-range (500 yards or more) accuracy out of a .243 is to custom build one with a 1:7 - 1:8 twist barrel with a chamber and throat cut to take advantage of 105-112 grain bullets. Maybe easier to buy (or rebarrel to) a 6 Creedmoor.

 

[pbreed]

For my simple mind, if you have a 243 retrofit with the same barrel twist I don't understand how the dasher can be better?
Pushing the same bullet down the same barrel at the same speed...

The 243 has a tiny bit more empty space so maybe you need slightly more powder to get the same exact bullet exit velocity and I could see that contributing to a very slightly larger recoil..

If you run the 243 hard then I could see faster speeds and more barrel wear..

 

[chevy_man]

For my simple mind, if you have a 243 retrofit with the same barrel twist I don't understand how the dasher can be better?
Pushing the same bullet down the same barrel at the same speed...

The 243 has a tiny bit more empty space so maybe you need slightly more powder to get the same exact bullet exit velocity and I could see that contributing to a very slightly larger recoil..

If you run the 243 hard then I could see faster speeds and more barrel wear..

243 is very hard on throats. Same speeds, Dasher will go 2x longer on barrels.

I think it's an effect of the case taper, it seems to push a lot of powder down the throat to finish burning. It also stretches cases worse than about anything else.

My last match barrel was a 243AI in a 1:7. Using h1000 under a 112 match burner it held in for 1200 rounds before I started getting flyers. I ran them all the way up to pressure signs at 3300fps, but settled in at 2950 because that's where it shot good. 26" barrel with a can. Can added about 30fps.
I shot it for practice and matches. It lasted me 2 summers, so not horrible. I did get it hotter than the hinges of hell with some 2 minute stage times and 15 round stages. If I treated it like a hunting rifle I'm sure it would have had hundreds more rounds easily.

Or, I can use less powder, and hit 2850-2900 with a dasher.

Currently I put a 25 Creed on to play with. It's going a lot better on barrel life. Still a laser beam.

However, I'll likely build another 243AI for hunting. Great deer and coyote round. And I still have about 600 mixed 243 cases and gauges so why not?

Next match barrel may be a Dasher. My BIL is putting together a Falkor action with a proof barrel right now. He might convince me.

 

[Bryan Litz Ballistics]

Good question, and you're thinking is good that if you select a .243 barrel with the right chamber and twist, it will shoot the same bullets as good as a 6 Dasher/BR.

At the higher levels of PRS competition, one of the most decisive variables is: did you see exactly where your shot hit/missed? If you can answer yes to this, your follow up shots are more likely to be hits than if recoil caused you to miss sight of the impact. So with that consideration, the difference between seeing and not seeing impact can be the difference in recoil between a 243 win and a Dasher.

So I'd say that's the advantage of the smaller case shooting 105 class bullets in the 2800 fps range. Good performance, and it's manageable.

All that said, I'm still a fan of the 243!

Why?

1) I'm not a PRS shooter. It is nice to see your impacts, but for what I'm doing, it's not 'decisive'.

2) 2800 is a nice speed for 105 class bullets, but 3100 fps is nicer

3) If you want, you can always load the 243 down to 2800 - Dasher performance. In fact, that's probably where the best precision will be, and it will be easier on the barrel. Use a small charge of a fast burning powder to minimize SD's with the down-loaded charge.

Good discussion.

-Bryan

 

[pbreed]

I already have 243 rifles. Wanted to try some longer range stuff and thought I'd shoot the heavy barrel model 70 for awhile and
then re-barrel it in 7 or 7.5 twist since I'm all setup for 243. Just trying to understand what I'm giving up. Why re-barrel an old gun?
Its my dad's competition gun from the 60's and has some nostalgia. I know that at one time my Dad took 4th place at camp perry at 1000yds as captain of the USCG rifle team. I don't know if it was with this gun as it was before I was born. He's been gone for about 12years and going shooting brings back some old and good memories.

 

[spife7980]

You don’t? Leave it alone.

If you want a dasher build a new one. A win70 isn’t an ideal host.

 

[DeathBeforeDismount]

You can't look at simple numbers. Tunability ( how easy it is and forgiving it is to find a load that shoots well) between them is huge. Much like the difference between a 6br and a 6 creed. With the BR use good brass Berger bullets and varget or N140 and pretty much any safe load is going to shoot very very well. Not the same can be said with 6 creed. Think about what makes these Uber efficient cartridge designs so inherently accurate. Be it powder collum, fill % and pressure curves. The dasher is basically a little longer necked BR. BR, BRA,BRX,Dasher and to a lessor extent the GT are all the same when it comes to effortless load development.

If the above didn't exist then people would have just downloaded 6 creed or 6x47 or even a fast twist 243 years ago and not dealt with mag or feeding issues.

 

[SanPatHogger]

If I were you, I would not rebarrel the gun your dad shot.

Do you plan on shooting PRS style matches and putting 3,000 rounds through it?
If so, then the reduced recoil and added barrel life point you toward one of the new fancy 6mm cartridges.

Do you already load for 243?
Do you have nostalgia for shooting the same round your dad did?
Are you a shooting enthusiast that want's to shoot really far but not enough volume to melt off barrels?
If so, then you might want to stick with the 243

I shoot a 243 because my uncle sent me one that he didn't shoot anymore. It now has a 26 inch 1:7 twist MTU Criterion with a match chamber that is throated for long heavy bullets. I think it shoots amazingly well. It shoots 115 Berger VLD Hunting bullets and Dtacs almost exactly the same.


Another way to choose....
Are you a they/them? Purple or green hair? Drink white claw? 6mm whatever flavor you like.
Are you a man? Hunt and eat what you kill with your bare hands? Work in concrete? 243
Good luck whichever you choose.

Here is a cherry picked 3 shot group from my 243.

 

[Sheldon N]

For accurate target shooting....
Trying to understand the technical reasons 6mm Basher seems to be more accurate(popular) than 243 winchester?

Why?
They are so close to being the same cartridge?

Is it all default barrel twist?
Will a 243 with 1:7 or 1:8 be just as good as 6mm Dasher?

Are there additional reasons?

Does the 6 Dasher deal with long VLD bullets better?

Better rifling land engagement?

6 Dasher has been around a long time in the world of 1000 yard benchrest competitions, it started winning records ~20 years ago. The Dasher was dominant for a long time, now you see more of a mix between 6 Dasher and 6 BRA (both very similar cartridges). Those benchrest guys really only care about how small of a group they can shoot at 1000 yards, regardless of what caliber it is. So I would say that the Dasher became popular because it is a more accurate cartridge.

Dasher picked up popularity with the PRS crowd maybe 8 years ago because it had a high level of accuracy and was also a low recoil cartridge which is perfect for the spotting your own misses in competition. It's been pretty prevalent in PRS since then, I'd guess at least twice as many matches have been won by Dasher in the last 5 years compared to anything else.

As to "why" the Dasher is more accurate than a 243, I'll reiterate some of the same things stated above. I think it's simply because the Dasher is a shorter, fatter, small case with a steeper shoulder angle.

When powder burns in a cartridge the combustion starts at the primer and works its way forward. The progression of that burning powder wants to push the powder at the front of the case forward. A really tall/skinny case will allow a lot of unburned powder to move forward during combustion and a shallow shoulder angle allows that powder to move into the throat of the barrel. A short fat, steep shouldered case tends to keep all the powder burning inside the brass cartridge. This results in more consitency from shot to shot, as well as a more efficient case - it takes less powder to make the same bullet speed.

Realistically though you can have a super accurate 243 and shoot fine with it. No need to change to a Dasher just because benchrest or PRS guys have found that it suits their needs.

 

[krw]

I read the posts and the word I looked for was inherently. There are some cartridges that are more inherently accurate than others. Look how the 6mm PPC has dominated 100yd Benchrest since the 70's. For pure accuracy the 6mm Dasher will outshine the 243

 

[pbreed]

Who makes a good < $2K 6Dasher bolt gun that feeds well?

 

[pbreed]

>Are you a man? Hunt and eat what you kill with your bare hands?
I'm 62... here's me with one of the 243's I now own, at age nine.
Got a little excited at this one from 150 yards and 2nd shot to finish I got ahead of myself and you can see the nice scope mark in my forehead.

 

[blksno]

I feel like, for your first post, it would have been a good idea to at least look at a picture of the two, side by side before making such an inflammatory statement.

They are so close to being the same cartridge?

They aren't even remotely close. In any aspect other than the bullet diameter they fire.

 

[DeathBeforeDismount]

Who makes a good < $2K 6Dasher bolt gun that feeds well?

I would find a used GAP ppr is 6 GT. They go around 2kish. You wont find many factory guns chambered in BR, Dasher or GT. If you go 6 creed your options open way up. Something like a Seekins Havick would be very nice.

There is factory ammo out there for 6GT, unlike 6 dasher unless you want to pay $2.5-3/round for custom ammo.

 

[pbreed]

I feel like, for your first post, it would have been a good idea to at least look at a picture of the two, side by side before making such an inflammatory statement.

So they are both short action, same diameter driving the same caliber bullet so yes I would categorize them as similar.
The case size is obviously different, I knew this before I asked the question.

Now I believe by reading between the lines I've actually gotten the answer I seek.
If I were to rephrase the answer as I understand it:

The default 243 twist is slower. (I acknowledged this in my opening question ) I won't address that here.

Answer as I see it:
The 243 is a larger case. I did not really understand why the larger case made it shoot differently for the same bullet and exit conditions.

To drive the same bullet at the same speed 243 has to pressurize a larger volume in total to generate the gas pressure
necessary. This requires more powder this contributes to increased recoil and more barrel wear for identical exit velocities.


Also a 243 case loaded to same exit velocities as 6-Dasher will have a lower fill percentage, this makes the distribution of powder in the case somewhat random and leads to some variation in the burning dynamics.

The variation is burning dynamics and the increase in recoil both lead to reduced accuracy.

So from physics first principal's I can see why the difference exists.

 

[Criver600]

6mm Dashers dominate 600 yard benchrest. I've got a 1" group at 600 yards hanging on the wall. Under 2" no big deal. You're not performing at that level with junk. You need be able to load ammunition capable of winning a match. Much better barrel life, lower recoil etc.
I've shot 243/243 Ackley's in NRA Long Range competition and they can be very accurate, but they eat barrels.