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6mm Rem. Ackley Improved vs. .243 Win.
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Trickymissfit
Well-Known Member
probably closer to 300% greater barrel life. Both rounds work best with 85+ grain bullets. Should be able to get close to 3550fps with an 85 grain bullet and a 26" barrel. I had little trouble seeing 3500fps with an 87 grain bullet.
gary
Call me a skeptic trickymissfit,
Regardless of what the barrel life might be..... the 6mm-284 can make bullets scream. I am getting 3465 fps the 95 gr Berger classic with 54 gr of RL-17 from a 24" barrel. (it is a 243 takeoff rem barrel rechambered)
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Using a 30" barrel the 105 berger hybrids can go 3400-3500 fps depending on powder.
Randy Derks world record 6 targets 7" @ 1000 YDS
54 grains of Reloader 22 - Federal 210m primer - Sierra 107 grain Match King bullet - 3425 fps
I got 3475 with RL-33 and 105 Berger hybrid.
Regardless of what the barrel life might be..... the 6mm-284 can make bullets scream. I am getting 3465 fps the 95 gr Berger classic with 54 gr of RL-17 from a 24" barrel. (it is a 243 takeoff rem barrel rechambered)
------------
Using a 30" barrel the 105 berger hybrids can go 3400-3500 fps depending on powder.
Randy Derks world record 6 targets 7" @ 1000 YDS
54 grains of Reloader 22 - Federal 210m primer - Sierra 107 grain Match King bullet - 3425 fps
I got 3475 with RL-33 and 105 Berger hybrid.
Originally posted by trickymisfit: " probably closer to 300% greater barrel life."
Thats a bold statement and I sure hope you are right. I'm building a 6 rem AI and bbl life is one reason I chose it.
I'm plan on try rl23 with 95 or 105vld. It's an 8 twist so hopefully I can even stabilize 105 Hybrids.
You guys care to share any pet loads ???
Thats a bold statement and I sure hope you are right. I'm building a 6 rem AI and bbl life is one reason I chose it.
I'm plan on try rl23 with 95 or 105vld. It's an 8 twist so hopefully I can even stabilize 105 Hybrids.
You guys care to share any pet loads ???
Trickymissfit
Well-Known Member
fps
the 6/284 is not, and never has been known for any kind of a serious barrel life. It's not uncommon to see them go south at the 1000 shot mark (I've seen them go south at 600 shots). Why? Poor case design and excessive over bore. On the otherhand 2500 shots seems to be about the minimum with the 6mmAI, and many folks are seeing well over 3000 shots. Why? Much less over bore with a good case design (not perfect but very good). The biggest difference is in the neck length alone.
A few years back some friends of mine were shoot the 6/284, and were going thru a barrel a year if not a little sooner. One guy reamed his barrel .100" short, and lost 75fps. That ought to tell you something right away. The barrel lasted about 50% longer I might add. The other guy reamed his barrel .150" short, and lost almost 100fps. He also got over two years heavy shooting out of that barrel. They mostly shot bullets in the 90 grain VLD range that were loaded very hot. Over bore smacks you in the face here.
Parker Ackley stated more than once, that the 6mm Remington case was about the max case capacity without going into over bore. The 6mmAI is slightly into over bore. Where as the 6/284 is deep into over bore. Yet the velocity difference between the two is almost nill (Precision Shooting found no real difference).
Looking at various 6mm's, one will soon find out that the 6BR is only slightly slower than the .243 Winchester. A much more accurate round as well. The 6BG would be like a 6BR on steroids, and is very similar in velocity to the .243 Winchester, but will have a greater barrel life due to the case design alone. It's pretty much a stretched 6BR that head spaces off a .300 Savage case gauge. I shoot the 6/250AI, and it will push a 105 grain Amax to just under 3100fps (very hot), but 3000fps seems to be the accuracy load. Yet the case is nothing but a 22-250 necked up. Very efficient, but hard on barrels due to the short neck length. Had the round been reamed off a 6mmAI reamer, I suspect a 50% greater barrel life. The .243 comes with it's own set of issues even though it has a nice case body volume. The .243AI reamed with a 6mmAI reamer would be a fantastic round. Still the .243 case could not be used. Yet Ackley never did that round to make it go faster, but trying to make the case and throat last a little longer. He felt the .308 case family to be pretty much an improved design from the factory. From there you move up to the 6mm Remington. A very, very good round with a long barrel life as it is. But the 6mmAI is the next step. You won't gain as much as many would like to think because the case capacity is already about it (perhaps 150fps). We should be seeing a trend here. The more powder, the less you gain.
gary
the 6/284 is not, and never has been known for any kind of a serious barrel life. It's not uncommon to see them go south at the 1000 shot mark (I've seen them go south at 600 shots). Why? Poor case design and excessive over bore. On the otherhand 2500 shots seems to be about the minimum with the 6mmAI, and many folks are seeing well over 3000 shots. Why? Much less over bore with a good case design (not perfect but very good). The biggest difference is in the neck length alone.
A few years back some friends of mine were shoot the 6/284, and were going thru a barrel a year if not a little sooner. One guy reamed his barrel .100" short, and lost 75fps. That ought to tell you something right away. The barrel lasted about 50% longer I might add. The other guy reamed his barrel .150" short, and lost almost 100fps. He also got over two years heavy shooting out of that barrel. They mostly shot bullets in the 90 grain VLD range that were loaded very hot. Over bore smacks you in the face here.
Parker Ackley stated more than once, that the 6mm Remington case was about the max case capacity without going into over bore. The 6mmAI is slightly into over bore. Where as the 6/284 is deep into over bore. Yet the velocity difference between the two is almost nill (Precision Shooting found no real difference).
Looking at various 6mm's, one will soon find out that the 6BR is only slightly slower than the .243 Winchester. A much more accurate round as well. The 6BG would be like a 6BR on steroids, and is very similar in velocity to the .243 Winchester, but will have a greater barrel life due to the case design alone. It's pretty much a stretched 6BR that head spaces off a .300 Savage case gauge. I shoot the 6/250AI, and it will push a 105 grain Amax to just under 3100fps (very hot), but 3000fps seems to be the accuracy load. Yet the case is nothing but a 22-250 necked up. Very efficient, but hard on barrels due to the short neck length. Had the round been reamed off a 6mmAI reamer, I suspect a 50% greater barrel life. The .243 comes with it's own set of issues even though it has a nice case body volume. The .243AI reamed with a 6mmAI reamer would be a fantastic round. Still the .243 case could not be used. Yet Ackley never did that round to make it go faster, but trying to make the case and throat last a little longer. He felt the .308 case family to be pretty much an improved design from the factory. From there you move up to the 6mm Remington. A very, very good round with a long barrel life as it is. But the 6mmAI is the next step. You won't gain as much as many would like to think because the case capacity is already about it (perhaps 150fps). We should be seeing a trend here. The more powder, the less you gain.
gary
Trickymissfit,
Good summary of the various 6mms. Had no idea the Rem AI would last that long.
I just chambered a barrel yesterday for 6 BR and am looking forward to shooting it. I own the reamer and was considering doing what I did with a 30 BR reamer a while ago. By going approximately another 1/2" deeper I made a 30BR/308 with a 30 degree shoulder and less body taper. It did require some serious neck turning on the 308 Lapua brass, down to .010" thickness. Thought it would be interesting to do the same with the 6 BR reamer. Then I found this article on the 6mm BR-K (aka 6 BR long) on accurate shooter. They did it first.
Hot .243-Based Wildcats — The .243 BR-K
Gunsmith Mike Sosenko and long-time AccurateShooter Forum member John Adams have been using a modified .243 Winchester case with great success in Varmint Silhouette matches at the Pala Range in Southern California. Officially called the ".243 BR-K" (and informally dubbed the "6BR Long"), the wildcat is basically a .243 Winchester with less body taper and a 30-degree shoulder. The design essentially grafts a 6mmBR Norma "top end" to the .243 Winchester case. After fire-forming, Mike and John can reload this case using normal, unmodified 6BR neck-sizing and seater dies.
Compared to a .243 Winchester, the .243 BR-K's body length is about .006″ longer, and the shoulder is about .0055″ wider. The main difference is the shoulder angle (30° vs. 20°), and the location of the neck-shoulder junction ("NSJ"). Based on reamer prints, the base to NSJ dimension is 1.718″ on the 6BR Long, compared to 1.804″ for the .243 Winchester. Neck length is a bit shorter because "the neck shrinks a little when the shoulder blows out" according to Sosenko. We've provided a mock-up diagram of the .243 BR-K, but you should check with Dave Kiff of Pacific Tool & Gauge for exact dimensions. Dave created the reamers for both the 6mm and 22-caliber versions of this wildcat. Ask for the "22 BR-K" or ".243 BR-K" reamer designs.
Wicked Velocity with Stable Brass
The main advantage of the .243 BR-K is serious velocity in a case that is very stable. Mike's favorite load is the 95gr Berger VLD pushed by Reloader 22. With a stout load of RL22 and Federal 210m Primers, Sosenko is getting 3450 fps with the 95-grainer, with no bullet blow-ups. This is with a 1:8.5″ twist Broughton 5R barrel finished at 28.5″. The cases are holding up very well. Mike has a half-dozen loads on his brass and he hasn't had to full-length size yet. Mike runs a .262″ tight neck, but there is also a no-turn version of the case (see illustration). Accuracy is excellent. Mike says the round delivers repeatable 1/4 MOA groups at 100 yards in testing. He has also experimented with N160, but, thus far, Reloader 22 has delivered smaller groups with better ES and SD.
VIEW 243 BR-K REAMER PRINT (No-Turn Neck)
John Adams shoots a no-turn (.274″) neck .243 BR-K with 105gr Berger VLDs. He's getting about 3230 fps using Reloader 22. John says he can push the 105s faster, but 3220-3240 fps "seems to be the sweet spot." John notes that "after about five reloadings on a case, it gets a little tight". John then full-length sizes with a custom Hornady FL bushing die. "The Hornady custom shop dies work great" according to John. Adams also shoots a version of this wildcat necked down to 22-caliber. It has demonstrated outstanding velocity and good accuracy in initial testing with a 9-twist barrel. Using the 80gr Amax bullets, John is getting 3570+ fps speeds. John feels that his 22 BR-K needs some more development work. "The .243 BR-K is proven. We know what works. With the 22 I want to try different seating depths, experiment with a few different bullets, and fine-tune the velocity."
Good summary of the various 6mms. Had no idea the Rem AI would last that long.
I just chambered a barrel yesterday for 6 BR and am looking forward to shooting it. I own the reamer and was considering doing what I did with a 30 BR reamer a while ago. By going approximately another 1/2" deeper I made a 30BR/308 with a 30 degree shoulder and less body taper. It did require some serious neck turning on the 308 Lapua brass, down to .010" thickness. Thought it would be interesting to do the same with the 6 BR reamer. Then I found this article on the 6mm BR-K (aka 6 BR long) on accurate shooter. They did it first.
Hot .243-Based Wildcats — The .243 BR-K
Gunsmith Mike Sosenko and long-time AccurateShooter Forum member John Adams have been using a modified .243 Winchester case with great success in Varmint Silhouette matches at the Pala Range in Southern California. Officially called the ".243 BR-K" (and informally dubbed the "6BR Long"), the wildcat is basically a .243 Winchester with less body taper and a 30-degree shoulder. The design essentially grafts a 6mmBR Norma "top end" to the .243 Winchester case. After fire-forming, Mike and John can reload this case using normal, unmodified 6BR neck-sizing and seater dies.
Compared to a .243 Winchester, the .243 BR-K's body length is about .006″ longer, and the shoulder is about .0055″ wider. The main difference is the shoulder angle (30° vs. 20°), and the location of the neck-shoulder junction ("NSJ"). Based on reamer prints, the base to NSJ dimension is 1.718″ on the 6BR Long, compared to 1.804″ for the .243 Winchester. Neck length is a bit shorter because "the neck shrinks a little when the shoulder blows out" according to Sosenko. We've provided a mock-up diagram of the .243 BR-K, but you should check with Dave Kiff of Pacific Tool & Gauge for exact dimensions. Dave created the reamers for both the 6mm and 22-caliber versions of this wildcat. Ask for the "22 BR-K" or ".243 BR-K" reamer designs.
Wicked Velocity with Stable Brass
The main advantage of the .243 BR-K is serious velocity in a case that is very stable. Mike's favorite load is the 95gr Berger VLD pushed by Reloader 22. With a stout load of RL22 and Federal 210m Primers, Sosenko is getting 3450 fps with the 95-grainer, with no bullet blow-ups. This is with a 1:8.5″ twist Broughton 5R barrel finished at 28.5″. The cases are holding up very well. Mike has a half-dozen loads on his brass and he hasn't had to full-length size yet. Mike runs a .262″ tight neck, but there is also a no-turn version of the case (see illustration). Accuracy is excellent. Mike says the round delivers repeatable 1/4 MOA groups at 100 yards in testing. He has also experimented with N160, but, thus far, Reloader 22 has delivered smaller groups with better ES and SD.
VIEW 243 BR-K REAMER PRINT (No-Turn Neck)
John Adams shoots a no-turn (.274″) neck .243 BR-K with 105gr Berger VLDs. He's getting about 3230 fps using Reloader 22. John says he can push the 105s faster, but 3220-3240 fps "seems to be the sweet spot." John notes that "after about five reloadings on a case, it gets a little tight". John then full-length sizes with a custom Hornady FL bushing die. "The Hornady custom shop dies work great" according to John. Adams also shoots a version of this wildcat necked down to 22-caliber. It has demonstrated outstanding velocity and good accuracy in initial testing with a 9-twist barrel. Using the 80gr Amax bullets, John is getting 3570+ fps speeds. John feels that his 22 BR-K needs some more development work. "The .243 BR-K is proven. We know what works. With the 22 I want to try different seating depths, experiment with a few different bullets, and fine-tune the velocity."
Trickymissfit
Well-Known Member
what you are discussing is very similar to the 6BG. Might also want to look at the 6SLR. Uses a factory .243 case. Dies are out there. The BG has the 30 degree shoulder, minimum taper (same taper as the .243) with a .35" neck length. Has the same gauge line as the .300 Savage case. It will push a 107 grain bullet to 2900fps. In other words about 90% as efficient as the 6BR per grain of powder.
When I do a barrel set back on the 6/250AI, I'll go with a 6mmAI reamer and use .243 brass for a loner neck length (I may have to shorten the shoulder length a tiny bit as I want a 2.00" case length)
gary
gtaylor1023
Well-Known Member
I absolutley LOVE the 6AI - i shoot two, one in 10 tw and one in 14 - both varmint guns for sure
If any of you are having issues aquiring brass let me know.
I have 200 rounds of virgin 6mm or would be more than willing to make you some 6mm AI brass out of 7x57 mauser. Its norma brass and lasts much longer than the remington.
Took me a while to master the converstion but I currently have all the tools to do it well and efficiently. Currently my chamber is .274 which requires a little neck clean up. Any 7x57 brass will need to be neck turned where as the .276 neck will not if using remington brass
If any of you are having issues aquiring brass let me know.
I have 200 rounds of virgin 6mm or would be more than willing to make you some 6mm AI brass out of 7x57 mauser. Its norma brass and lasts much longer than the remington.
Took me a while to master the converstion but I currently have all the tools to do it well and efficiently. Currently my chamber is .274 which requires a little neck clean up. Any 7x57 brass will need to be neck turned where as the .276 neck will not if using remington brass
Booney
Well-Known Member
Hey Tricky when you say you will use a 6mmAI reamer and use 243 brass that will basically a 6SLR right?
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Trickymissfit
Well-Known Member
I thought the SLR used a 30 degree shoulder. If I'm wrong, then so be it! But I think the SLR has a slightly longer shoulder length than the 250 case. Anyway, I'm looking at a 1.46" shoulder length to make everything fit with the Ackley neck and shoulder. In other words a 6BG reamed .100" long, but with a 40 degree shoulder. I think it will push a Sierra 107 grain bullet to 3100 fps with a barrel life that will out live me. I'd rather have a 30 degree or a 35 degree shoulder.
gary
