115 Dtacs

[urbanrifleman]

If you chamber your barrel with the appropiate freebore thats no issue with dtacs. In fact Davids reamer that Manson makes is set up to make sure that the bullet does not seat past the terminus of the neck.

Yes. I know. I've chambered a few. I have the 160, 100, and 50fb reamers. I only offer the 160 and 50 now. The 160 shoots just about everything.

I was just saying a person could go even longer. David designed it to be the correct length in a Remington box mag for use as a repeater with the DTAC seated at 20 jump. Which is awesome. But for single feeding there is even more case capacity available.

 

[ACard]

The idea is that the heavier bullets are in the barrel longer, so that flame has longer to act on the bore. I don't know how much that really plays out, but it sounds credible to me. Anecdoatlly, heavier bullets seem to take a toll.

In any case, I was referring to the fact that a 6xc or a .243 shooting DTACs isn't going to last as long as a 6BR shooting 103-108s. And that's definitely a noticeable difference. You pay quite a bit for that little advantage.

In fact the heavier bullets are not about longer bore time. They are about lengthening the bullet changing the CG and increasing BC for long range performance. The main difference in erosion is going to be the difference in powder charge size.

 

[urbanrifleman]

The 6xc has some advantages over the 6br. One of them is the ability to shoot those longer bullets.

Once again I would say that the 6br reamers are way too short on freebore. If a person were to go to 160 or even 260 in a 6br or 6bra the DTAC would shoot great in a 6br.

People really have not spent enough time looking at the back of the bullet in the neck.

 

[Retired shooter]

I found I like the mid size 6mm cases like the BRX and Dasher and the DTAC is just too heavy for them. The 109 Berger is a great bullet for the mid size 6mm’s.

The 109 Berger might be a good alternative, "IF" you big guys would share some with the little guys. Finding them is the pitts.


Thank you to all who have provided some great info.

 

[dcali]

In fact the heavier bullets are not about longer bore time. They are about lengthening the bullet changing the CG and increasing BC for long range performance. The main difference in erosion is going to be the difference in powder charge size.

I'm aware of why people like heavy bullets.

Light bullets use more powder, though. But even given equal powder charges, the heavy bullet will spend more time in the bore, which will expose the bore to high flame temperatures for slightly longer each time the trigger is pulled. Barrel erosion is in large part due to melting a very thin layer of the bore. So it makes sense.

I can't say for sure, and I doubt anyone can show it definitively, but but anecdotally, I think you'll find people have the experience that shooting heavy bullets eats barrels a little faster even when shooting similar powder charges. Shooting 155s vs 200s in a .308 for example.

 

[Bob3700]

I'm aware of why people like heavy bullets.

Light bullets use more powder, though. But even given equal powder charges, the heavy bullet will spend more time in the bore, which will expose the bore to high flame temperatures for slightly longer each time the trigger is pulled. Barrel erosion is in large part due to melting a very thin layer of the bore. So it makes sense.

I can't say for sure, and I doubt anyone can show it definitively, but but anecdotally, I think you'll find people have the experience that shooting heavy bullets eats barrels a little faster even when shooting similar powder charges. Shooting 155s vs 200s in a .308 for example.

Years ago, Kevin Thomas (Sierra Bullets) did a lot of testing on barrel life with different wt. bullets. As bullet weight went up, barrel life went down. He kept excellent records on rounds fired in each of his test barrels in the test tunnel. Barrels that fired the 107 gr. bullets experienced faster wear than barrels that tested the lighter 6mm bullets.

He also tested moly coated bullets and could not find a benefit to increased bbl life. That is not to say there are no benefits to coating bullets, just that the coating did not extend bbl life. A lot of these results were part of articles published in Precision Shooting.

 

[6xcshooter]

I'm aware of why people like heavy bullets.

Light bullets use more powder, though. But even given equal powder charges, the heavy bullet will spend more time in the bore, which will expose the bore to high flame temperatures for slightly longer each time the trigger is pulled. Barrel erosion is in large part due to melting a very thin layer of the bore. So it makes sense.

I can't say for sure, and I doubt anyone can show it definitively, but but anecdotally, I think you'll find people have the experience that shooting heavy bullets eats barrels a little faster even when shooting similar powder charges. Shooting 155s vs 200s in a .308 for example.

Here we were talking 107 gr compared to 115 gr. 8 gr difference. Did some calculations, 24 inch barrel , 115 gr bullet going 2900 fps equals .00068 seconds in the barrel. 107 gr going 2950 fps equals.00067 seconds in the barrel. This simplified not taking into account for ecceleration , but it would be almost exactly the same for both bullets. So given the fact of 1 hundred thousands of a second in mho it makes no to minuscule difference in barrel life. Even if you shot 1500 rounds of the 115’s it would only equal .015 seconds more total time inside the barrel compared to the 107’s. So in mho it doesn’t matter a gnats ass which bullet you shoot for barrel life.

 

[ACard]

I'm aware of why people like heavy bullets.

Light bullets use more powder, though. But even given equal powder charges, the heavy bullet will spend more time in the bore, which will expose the bore to high flame temperatures for slightly longer each time the trigger is pulled. Barrel erosion is in large part due to melting a very thin layer of the bore. So it makes sense.

I can't say for sure, and I doubt anyone can show it definitively, but but anecdotally, I think you'll find people have the experience that shooting heavy bullets eats barrels a little faster even when shooting similar powder charges. Shooting 155s vs 200s in a .308 for example.

I have never been able to draw a correlation to bullet weights per se and barrel/ throat life over the last 50 years. I have been actively involved in competitive shooting sports for that amount of time and usually in long range disciplines. Now, to be totally fair, I have not put much thought into bullet weight as a contributor but have always, because of the disciplines I shoot in, tended to shoot heavies.

In my statement about charge weight being more significant, I was addressing the comparison you make between 6BR and 6XC. I made that observation because it would not be a statistically important comparison as the difference between the two cartridges case capacity is vastly different.

As for heavies vs lighter bullets causing faster erosion, I would guess that the difference would be so minor that most shooters would not even notice the difference in barrel life. Not to mention that unless it were the exact same barrel set back to the next test, the amout of variables between two different blanks and the metallurgical make up would again make any findings subject to question.

 

[6xcshooter]

I have never been able to draw a correlation to bullet weights per se and barrel/ throat life over the last 50 years. I have been actively involved in competitive shooting sports for that amount of time and usually in long range disciplines. Now, to be totally fair, I have not put much thought into bullet weight as a contributor but have always, because of the disciplines I shoot in, tended to shoot heavies.

In my statement about charge weight being more significant, I was addressing the comparison you make between 6BR and 6XC. I made that observation because it would not be a statistically important comparison as the difference between the two cartridges case capacity is vastly different.

As for heavies vs lighter bullets causing faster erosion, I would guess that the difference would be so minor that most shooters would not even notice the difference in barrel life. Not to mention that unless it were the exact same barrel set back to the next test, the amout of variables between two different blanks and the metallurgical make up would again make any findings subject to question.

I agree

 

[urbanrifleman]

I think powders eat barrels not bullets. Hot powders eat barrel life. Regardless of the bullet.

 

[dcali]

I have never been able to draw a correlation to bullet weights per se and barrel/ throat life over the last 50 years. I have been actively involved in competitive shooting sports for that amount of time and usually in long range disciplines. Now, to be totally fair, I have not put much thought into bullet weight as a contributor but have always, because of the disciplines I shoot in, tended to shoot heavies.

In my statement about charge weight being more significant, I was addressing the comparison you make between 6BR and 6XC. I made that observation because it would not be a statistically important comparison as the difference between the two cartridges case capacity is vastly different.

As for heavies vs lighter bullets causing faster erosion, I would guess that the difference would be so minor that most shooters would not even notice the difference in barrel life. Not to mention that unless it were the exact same barrel set back to the next test, the amout of variables between two different blanks and the metallurgical make up would again make any findings subject to question.

That's my point. At the end of the day a slightly lighter bullet in a BR is going to be more practical than a 115 in a 6xc and not give up much performance. That's one reason I don't think they're as popular.

 

[dcali]

Here we were talking 107 gr compared to 115 gr. 8 gr difference. Did some calculations, 24 inch barrel , 115 gr bullet going 2900 fps equals .00068 seconds in the barrel. 107 gr going 2950 fps equals.00067 seconds in the barrel. This simplified not taking into account for ecceleration , but it would be almost exactly the same for both bullets. So given the fact of 1 hundred thousands of a second in mho it makes no to minuscule difference in barrel life. Even if you shot 1500 rounds of the 115’s it would only equal .015 seconds more total time inside the barrel compared to the 107’s. So in mho it doesn’t matter a gnats ass which bullet you shoot for barrel life.

You can't ignore acceleration - it matters a lot. Barrel time is closer to .002 seconds than .0007 seconds. If it increases even 5% with a heavy bullet, you've just lost 5% of your barrel life (give or take).

 

[6xcshooter]

That's my point. At the end of the day a slightly lighter bullet in a BR is going to be more practical than a 115 in a 6xc and not give up much performance. That's one reason I don't think they're as popular.

If you don’t care about wind deflection

 

[dcali]

If you don’t care about wind deflection

Everything is a balancing act. You could really make them scream out of a .243 but you're gonna have a bad time overall. I'm just saying why I think they're not as popular as 107 class bullets. 100-110 seems to be the sweet spot for 6mm bullets. Run the numbers, the wind difference isn't *that* big at ranges where shooting any sort of 6mm makes sense.

Smaller, more efficient cases with slightly lighter bullets that buck the wind almost as well as a DTAC out of a 6XC are attractive to a lot of shooters. Really long bullets also have the downside that they have to be launched perfectly or you'll have trouble with accuracy. Like I said. everything is a balancing act. Pick your poison.

 

[6xcshooter]

I’ll take the 6xc over a br at any range and any yardage. But that’s just me. And I have many 6 mm cartridges. 6br,6dasher,6x47lapua,6creedmoor, 243win,my favorite of all the 6xc

 

[6xcshooter]

Here’s a few of my various 6mm’s

 

[6xcshooter]

You can't ignore acceleration - it matters a lot. Barrel time is closer to .002 seconds than .0007 seconds. If it increases even 5% with a heavy bullet, you've just lost 5% of your barrel life (give or take).

I not smart enough to calculate the time of acceleration. Be very close to same considering on 50 fps and 8 gr difference in bullets. Let me know what your calculations say the time of acceleration is.

2 feet divided by 2900 fps =0.00068965517241379
2feet divided by 2950fps = 0.000677966101694915
Seconds inside the barrel.
Pretty sure you won’t be able to see any significant barrel wear. But shoot what ever you think is best for you.

 

[davidjoe]

You can't ignore acceleration - it matters a lot. Barrel time is closer to .002 seconds than .0007 seconds. If it increases even 5% with a heavy bullet, you've just lost 5% of your barrel life (give or take).

I’d also suggest that a heavy bullet with a long bearing surface could spend significantly more time in its first inch of travel, maybe twice as long.

We hear often that a .22LR does not need a barrel longer than ~17 inches for maximum velocity. For a lot of match rifles a good portion of the LR bullets’ barrel time isn’t increasing velocity by significant amounts. The occurrences at the beginning of barrel time may tell us more than its total length does.

I would imagine that longer barrel time’s containment where the heat and pressure is the highest, does take a greater toll than shorter barrel time in that short throat area disproportionally affecting accuracy.

Where the difference is really clear in wear is .223 FTR rifles. I have felt that .223’s shooting the heaviest bullets have some of the shortest lives in accurate round count, whereas with light bullets for say 100-200 yard matches, they can have the longest lives.

 

[6xcshooter]

Well only way to settle this is for someone to get 2 exactly the same barrels. Shoot them exactly the same day. Shoot the loads with same powder primers and brass. Cool off barrel exactly the same length of time. Shoot exactly the same amount of rounds through them. Then get someone to measure the lands for wear and see what the results are.

 

[dcali]

Well only way to settle this is for someone to get 2 exactly the same barrels. Exactly the same load. Shoot them exactly the same day. Cool off barrel exactly the same length of time. Shoot exactly the same amount of rounds through them. Then get someone to measure the lands for wear and see what the results are.

Nah, all you have to do is keep records like Sierra did. The military has done all kinds of work on barrel erosion. It's not that much of a mystery - the way it happens is pretty well understood.