243/6mm rifle build...thoughts?

[JAYgs8163]

For a standard 700 short action, the mag length is 2.850 if I remember correctly. The OP obviously wants to shoot bullets heavier than 95 grains.
If you look at Bergers offerings in hunting bullets, the 108 EH and the 115 VLD's stand out since he will be using a 28", 7 twist barrel. So to keep from encroaching on powder space, I would likely set it up for the boat tail/body junction of the bullet to be at the base of the neck of the case or slightly above to avoid a doughnut.
243 Win case= 2.045-1.804(shoulder/neck junction)=.241 neck length.
Berger 108EH oal= 1.260-.185(boat tail length)=1.075
(minus case neck length).241=.834
So, 2.045(case length)+.834 (bullet protruding past case mouth)=2.879 aol.

For the 115 VLD
bullet oal=1.348
Boat tail - .196
neck length- .241
= .911(length of bullet sticking out of case)
+ 2.045(case length)
=2.956 cartridge oal
If you don't mind giving up powder capacity, it would work on a short action. But, if you're going to do that, you may as well start with a shorter case with less capacity to begin with. Just my opinion.

Just depends on what mag well he's running. If he's got a M5/DBM bottom metal he can get Accurate Mag without the binder plate which allows for 2.99 OAL. I run my 308 this way have load I run at 2.95 OAL. Feeds fine.

If he's running a BDL he can put a Wyatt's extended box and also run 2.99 OAL.

 

[Mike Matteson]

For a standard 700 short action, the mag length is 2.850 if I remember correctly. The OP obviously wants to shoot bullets heavier than 95 grains.
If you look at Bergers offerings in hunting bullets, the 108 EH and the 115 VLD's stand out since he will be using a 28", 7 twist barrel. So to keep from encroaching on powder space, I would likely set it up for the boat tail/body junction of the bullet to be at the base of the neck of the case or slightly above to avoid a doughnut.
243 Win case= 2.045-1.804(shoulder/neck junction)=.241 neck length.
Berger 108EH oal= 1.260-.185(boat tail length)=1.075
(minus case neck length).241=.834
So, 2.045(case length)+.834 (bullet protruding past case mouth)=2.879 aol.

For the 115 VLD
bullet oal=1.348
Boat tail - .196
neck length- .241
= .911(length of bullet sticking out of case)
+ 2.045(case length)
=2.956 cartridge oal
If you don't mind giving up powder capacity, it would work on a short action. But, if you're going to do that, you may as well start with a shorter case with less capacity to begin with. Just my opinion.

I understand that, but a LA allows you to do different things with it. He might want to shoot something different and require a LA. Once you set up your action, trigger, and stock. You are down to barrel you want. You just wasted your time in explaining or showing all these dimensions. I do believer that most of us understand what a SA is, and limited with them. Now if you decided to change to a 6mm/06 (.243) bullet. Gee now you have to get a different action, stock and set it up. What if you want to go to a 6mm/280 or 280AI. Gee that SA is again to short. Can't do it. So why limit yourself to a short action? Being he has a SA he can decided how he wants to go. I didn't say he had to go to a LA, just open up another way to go.

 

[JAYgs8163]

Or he can hit the easy button and do a 6 Creedmoor and be done.

 

[JAYgs8163]

If he does a long action then he's buying everything. Stock, action, barrel, bottom metal, etc….. as opposed to a barrel and maybe a bottom metal. Significant budget change.

 

[DustThroughaFan]

Or he can hit the easy button and do a 6 Creedmoor and be done.

There were quite a few options for ammo at academy today. Some of it was $60 a box though.

 

[Wyo37]

Or he can hit the easy button and do a 6 Creedmoor and be done.

It's pretty simple

 

[ATH]

I run 243AI optimized to the lands mag fed from a short action....it's a huge improvement from standard 243 both in terms of velocity and case life. Depending on the powder with a 24" barrel I get 3200-3280fps accuracy loads with Re22 and Re26 respectively. Big difference is standard 243 constant trimming 243AI never trim. I never shot enough 243 to reach end of case life but it's pretty obvious the 243AI has massively extended case life if you don't blow the primer pockets.

 

[44-40]

I built a long action 308 Win. Just to see what is possible with a 308, for 200 to 250 grain bullets, out of a 308 case, on an aluminum chasis and 30-06 mags to feed up to 3.4" cartridges...on a 30" 8 twist throated barrel, in my garage.
Before introducing the hybrid bimetal cases I was shooting 200 grain SMK at 2856 Ave. 225 eldm at 2675 fps, and 230 Atip at 2620 fps. The Hybrid case makes it possible to add more velocity 2952 fps out of a 308 case with 200 gr SMK, and a reformed 6.8x51 case. So far I like the lapua brass cases well enough and have not yet found the Magic powder for the 308, although incerases in velocities were obviously present.
So a long action can basically increase case capacity for the long aerodynamic bullets when they way out of the case.
But fired some more Bimetal hybrid cases in 6.5 Creedmoor with 150 gr at 2980 fps, 153 Atips at 2953 fps, and 147 gr eldm at 2976 fps as a standard acceptable load, this in a 24" factory 6 5 barrel. Not for the average guy who doesn't build his own rifles...but huge gains are possible in certain instances. For most a factory cartridge is the least expensive way to go. The 6mm Creedmoor is fine so is the 6.5 Creedmoor, with factory match ammo available for those who do not reload..they are low recoil for target work and affordable to shoot so you can become an expert...the magnums cost more in ammo & burn up barrels, more practice equals better shooting.

 

[Culpeper]

I ended up building a .244 Rem aka 6mm Rem long action. Longer neck and can take long skinny high BC bullets unlike the 243 Win.

 

[BenelliHunter]

I have somewhere between 7 and 10 6CM's because my kids are small and they love them. We found a factory round that shoots sub 1/3" in 4 of our rifles and bought 10K rounds. They should be set for the foreseeable future. When deciding on the round we were dealing with covid and there was more available for the 6CM than for the 243 at the time.

 

[sendero72]

Hello everyone! I'm thinking ahead a bit, but I'm considering a 6mm build in the next couple of years. I will preface this discussion with the fact that I will be building the rifle on a Remington 700 action in 243 Win. I have shot thousands of rounds out of this rifle, and it is my favorite gun. Period. I've killed prairie dogs, varmints, coyotes, deer, and antelope with it. Shot paper, steel, shotgun shell hulls, and coins with it. The thing has always been a tack driver, and I it!

Anyway, my only complaint about the gun, being a factory rifle in 1-9.5 twist, is that I could not stabilize anything heavier than 95 gr pills out of it. Groing in the long range game, I've found myself leaving the gun in the cabinet in favor of my 7mm Rem mag and 308 Win.

I'm torn about what cartridge to focus on for a new build. All would have a 28 inch barrel with a 1-7" twist.

243
Pros - I already have a love for the chambering, I have the dies, brass, etc.
Cons - you cannot let the heavier bullets out as much (COL) as I might want to.

6CM
Pros - There are components, specifically brass, available. There is more room to seat bullets out in the short action mags.
Cons - I'd have to buy new brass and dies. I will also be honest that I don't want to become part of the CM fan Boyz I like my older cartridges.

6 GT
Pros - From everything I've read, you get more for less. The same velocity, less powder, less recoil. The chambering looks exceptionally efficient! I can let my seating depth out even more than the CM.
Cons - finding brass looks to be a pain in the ***, and again I'd have to get new dies. It doesn't hurt my pride as much as becoming a fan boy, but switching still hurts my pride a bit.

Those are my thoughts. I'd love to hear what y'all think. Thanks in advance!

I purchased a Savage model 11 for $300 just for rebuilding. I had the bolt-faced trued and re-barreled with a 29" Krieger 7.7 twist. It's throated for the heavier bullets 108-115 gr. Using Hogdon V-100, the rifle shoots .03 at 100 yds and 2-inch groups at 600 yds. The 108 eldms are deadly on whitetails. Good luck.

 

[Tiny Tim]

For a standard 700 short action, the mag length is 2.850 if I remember correctly. The OP obviously wants to shoot bullets heavier than 95 grains.
If you look at Bergers offerings in hunting bullets, the 108 EH and the 115 VLD's stand out since he will be using a 28", 7 twist barrel. So to keep from encroaching on powder space, I would likely set it up for the boat tail/body junction of the bullet to be at the base of the neck of the case or slightly above to avoid a doughnut.
243 Win case= 2.045-1.804(shoulder/neck junction)=.241 neck length.
Berger 108EH oal= 1.260-.185(boat tail length)=1.075
(minus case neck length).241=.834
So, 2.045(case length)+.834 (bullet protruding past case mouth)=2.879 aol.

For the 115 VLD
bullet oal=1.348
Boat tail - .196
neck length- .241
= .911(length of bullet sticking out of case)
+ 2.045(case length)
=2.956 cartridge oal
If you don't mind giving up powder capacity, it would work on a short action. But, if you're going to do that, you may as well start with a shorter case with less capacity to begin with. Just my opinion.

A Wyatt's or Bainey box will give the additional space required if a bullet. Cheap fix and no other mods really necessary.

 

[esorensen]

I'm in the OP's boat as well. A well used AR10T .243 with a 24" 10 twist. Silly accurate, but pretty much stuck with the 87 vmax due to the slow twist. Killed a boat load of stuff with it over the years, and it's getting tired. I already have a 6 CM bolt gun and it's great too! However the .243 barrel is most likely being replaced with the 6SLR 26-27" 8 twist or so carbon affair. IMO that's what the .243 should have been in the first place. I may be wrong, but smacking the SLR case from a straight .243 is maybe a pinch easier than doing the full AI. Then again you might be able to get away with firing a straight .243 in an AI chamber and then you have your brass. My concern is the full AI not feeding so great in the AR platform, but that's most likely not the case with a bolt gun. The SLR does not have as much capacity as the AI, but better neck length than either the CM or AI. Honestly they're all apples to apples. Do you really think there's a coyote, antelope, deer, whatever out there that will question a solid hit from the ~100 fps difference from any of them? I think we in this wonderful hobby of ours we tend to split hairs. Do whatever scratches the itch.

 

[lancetkenyon]

For a standard 700 short action, the mag length is 2.850 if I remember correctly. The OP obviously wants to shoot bullets heavier than 95 grains.
If you look at Bergers offerings in hunting bullets, the 108 EH and the 115 VLD's stand out since he will be using a 28", 7 twist barrel. So to keep from encroaching on powder space, I would likely set it up for the boat tail/body junction of the bullet to be at the base of the neck of the case or slightly above to avoid a doughnut.
243 Win case= 2.045-1.804(shoulder/neck junction)=.241 neck length.
Berger 108EH oal= 1.260-.185(boat tail length)=1.075
(minus case neck length).241=.834
So, 2.045(case length)+.834 (bullet protruding past case mouth)=2.879 aol.

For the 115 VLD
bullet oal=1.348
Boat tail - .196
neck length- .241
= .911(length of bullet sticking out of case)
+ 2.045(case length)
=2.956 cartridge oal
If you don't mind giving up powder capacity, it would work on a short action. But, if you're going to do that, you may as well start with a shorter case with less capacity to begin with. Just my opinion.

Very well thought out. Great number references. And would be a great loaded round with a custom AI reamer or throater. Standard .243AI FB is .082".

I don't think a 6CM is going to run with a .243AI for speed, even if you seat the bullets past the body to should junction. Hard to make up for 3-4 extra grains of powder capacity, or nearly 7-10%.

I know a 6.5CM doesn't run with a .260AI at the same COAL.

I'm in the OP's boat as well. A well used AR10T .243 with a 24" 10 twist. Silly accurate, but pretty much stuck with the 87 vmax due to the slow twist. Killed a boat load of stuff with it over the years, and it's getting tired. I already have a 6 CM bolt gun and it's great too! However the .243 barrel is most likely being replaced with the 6SLR 26-27" 8 twist or so carbon affair. IMO that's what the .243 should have been in the first place. I may be wrong, but smacking the SLR case from a straight .243 is maybe a pinch easier than doing the full AI. Then again you might be able to get away with firing a straight .243 in an AI chamber and then you have your brass. My concern is the full AI not feeding so great in the AR platform, but that's most likely not the case with a bolt gun. The SLR does not have as much capacity as the AI, but better neck length than either the CM or AI. Honestly they're all apples to apples. Do you really think there's a coyote, antelope, deer, whatever out there that will question a solid hit from the ~100 fps difference from any of them? I think we in this wonderful hobby of ours we tend to split hairs. Do whatever scratches the itch.

Forming a .243 Win brass to 6SLR is as simple as a single pass in the FL die. Gets you 98%.

I have had a 6.5SLR for years. Shot the first barrel out at 2800 rounds. Second barrel has about 700 on it, and is my daughter's go-to rifle.

Just know this in advance. When doing an SLR, if you go with Rem or Win brass, you are good to go. They both use the same thickness brass in the neck and shoulders. If you go most other brands (Lapua, Alpha, Peterson, Fed, etc.), you will need to turn necks. They use thicker brass in the shoulders than the neck has. And since you are reforming the shoulder to 30° and pushing that into the neck, you will get a mean donut. Unlike the AI, which sharpens the shoulder by pushing the body up into the shoulder area, but leaves the neck as is.

For reference. (Neck any of these down to 6mm, and it would be 6CM, .243 Win, 6SLR, .243AI)

L-R: 6.5CM, .260 Rem, 6.5SLR, .260AI