6mmbr vs. .243 AI - my first post

[Scott7m]

Been reading here for a year or so. Have always been a varmint hunter, but just now getting the desire for a nice custom.

I'll also say the more you read on hear is the more confused one can get lol.......

SO here is my question to you, I plan on building a custom rifle. I'm going to use it for general varmint hunting, coyote, crows, that kinda stuff.

I am looking to use 87 grain vmax bullets in case i'd like to pop a deer as well.. However I am torn between the .243AI and the 6mmbr. I saw where matt pushed a 107 up to 3350 with an AI, and I do like to run my loads on the hot side in my 22-250. That intrigued me on the 243ai, I thought if they can push a 107 that fast a 87 should go over 3500?

But what is the best, or what would you guys reccomend, is it possible to get speeds in the neighborhood of 3500 with the AI or br? If so what are the advantages and disadvantages to each!?

thanks for the help

 

[chadjamesr]

I might not have answers for all of your questions, but I can comment on a .243AI that I have. My rifle is a laser! I'm still fire forming but consistently get sub 1/4" groups at 100 yards with 70gr Speer TNT and 40gr of Varget. I just returned from Kansas yesterday on a dog hunt and shots under 200 yards were guaranteed. I haven't ran the chronograph on my rounds yet as I'm still trying to fire form all 500 of my cases before I work on my loads.

I'm in the same boat as you though as I'm thinking of buying a 6mmbr as well. The advantages to the .243AI from what I understand is the higher velocity, better feeding, and cheaper cases if you buy winchester. The advantages to the 6mmbr is 3 times the barrel life and less cost in powder.

Personally I will always use my .243AI for my varmint hunts as it works flawlessly and the little extra speed is nice. I'm still building a 6mmbr, but that will be my range gun and possibly my girlfriend's rifle when she goes out shooting varmints with me.

If you have any questions, let me know.

 

[Eddie Harren]

The 243 AI is a proven "Hot Rod" that delivers speed and accuracy. Remember that the standard 243 Win., when pushed to the max., has a reputation for being a barrel burner. Wringing more velocity by "improving" this case will only compound this situation. The "cost" of obtaining the velocity is shorter barrel life. There are no "free lunches".

 

[janderson0]

Fireform 500 243 AI before working on loads? Sounds like you might not ever see what that barrel could do.

Jim

 

[Ackman]

Both are real good cartridges, but they're very different. Like the difference between a small block and a big block engine. The .243AI shoots flat with 70's doing 3800-3850 depending on the bullet, and does it with great accuracy. The 6BR uses about 15gr less powder and mine shoots 55/58's at 3850-3900+, also with great accuracy. It's all in how you want to use the gun. I've never shot 87's in the .243AI but 3500 sounds do-able.

Thing about a .243AI, the .243 already has about the same shoulder dia. as an AI. Fireforming blows the shoulder forward considerably but changes body taper only a little. The Improved version is a definite performance step up and worth doing, but not such a large step as with some other AI cartridges. Fireforming accuracy is just as good as with formed cases, and fireforming velocity will be about the same as with a formed case. So don't worry about extra barrel wear "fireforming"......as with any other AI case you just load and shoot. One of my .243AI's has upwards of 2,000rds through it. This one has a 13" twist. Although the gun is still accurate, right now it's getting a new barrel for when that day comes. I shoot mostly 70TNT's.

The 6BR is awesome. It shoots light 6mm bullets faster than a 22-250 will shoot the same weight bullet and does it with less powder. Some people like to lob heavy bullets, I prefer lighter ones going fast. A 6mm/55 Bal Tip has the same BC as the .22 cal 55gr. version and at 3900+ those things shoot flat. My gun has a Sako action and the 6BR doesn't feed as a repeater. There are supposedly ways to make one feed in a Rem. 700, but I've no experience with that.

Which one you choose all depends on how much horsepower you want.

 

[chino1969]

I shoot 87 grn. V-Maxes at approx. 3550 ft/s. out of a 1:10" .243 A.I. driven by a stiff load of H4831 sc. I have two other brand new 1:10" barrels and just started breaking in a 1:12" barrel to shoot lighter bullets from 80 grn. down to 55 grn. The .243 A.I. is a fine hard hitting varmint cartridge and I have dropped many groundhogs with it from 200 to 500 yards. Ackleys are tough on barrel wear and that is one of the prices you pay for this speed.

I have a 6mm BR with a 1:14" barrel that shoots 65 grn. Horn. V-Maxes into a single hole at 200 yds. The 6mm BR is a very accurate cartridge that is easy on barrel wear but it doesn't have the kill power of a .243 A.I. at distance, particularly on hard skinned PA groundhogs. They are both great cartridges, but very different.

Here's a consideration where you can have the best of both worlds: start with one of the new Savage single shot actions for your project with a .308 boltface. Shilen & Pac Nor offer excelllent Savage pre-fit barrels. You can have a .243 A.I., a .22-250 A.I., a 6mm BR, a .308, etc. with different rates of twist, etc. with only one rifle. You'll save alot of money going this route and will be able to kill crows, groundhogs, prarie dogs, coyotes, etc.
Chino69

 

[Scott7m]

thanks for all the reply's..... In building my frist custom rifle it seems choices are endless.

Let me get this straight.. 1 guy says his 6mmbr shoots as fast or faster than his 243ai, and another guy says the br just doesn't have the power that an ai has...... kinda confusing.. however...

this is what i've taken from what i've read so far, it's kind of like the 243ai is fast but hard on the barrel and so on.. the 6mmbr can acheive the same results but with less powder and a better barrel life?

I'm just wondering if you set up targets out through a field at 100 2,3,4, and 500 if one is going to shoot flatter or more consistent than the other. Heard great things about each..

So far I still haven't decided on much, i guess i'm in the research phase of the project. However there is a nice stock i like on the site that is a 2 wood laminate thumbhole varmint design that i really like..

 

[Scott7m]

the reason i want a flatter shooting gun is partially because of the scenario i'm often in when varmint hunting. here it's not go out in a field and set up and wait for something to pop up, here we drive around for a few hours on dirt farm roads hunting for coyote and crows. Shots must be made as quick as you can get the sand bags on top of the car, there is no time to really adjust and check exact yardage although we try to use rangefinders when conditions allow. So the flattter shooting is the less i'll have to allow when faced with a long shot, and there sure isn't enough time to go clicking on the scope..

But I've never had a scope where the adjustments were so at hand and such, maybe i'd think different after getting one.

I've been looking at the 6 - 20X Zeiss as my scope of choice on this rifle.

 

[Scott7m]

thanks for the excellent idea there chino69, is the savage single shot actions pretty good? i hope so, that would be nice.
only bad thing i can see is that the longest barrel they show is a 26" for the drop ins.

Hopefuly they still shoot well..

 

[Jake31]

Scott7m, I am currently building a new custom rifle in 6MM BR. In the beginning of my project I was going to go with a 6x284. I have owned previous 6x284's and had much success with that cartridge. It pushed the 87grn V-Max at 3750fps and the 107grn Sierra Match King at 3500fps.

However, here is what happened to make me go to the 6BR. During a squirrel hunting trip I witnessed something that was awesome. One of the guys on the trip had a custom 6BR. This guy was hitting everything we missed. I was shooting my custom 6x284 with the 87grn V-max traveling at 3750fps. He was shooting his custom 6BR with a 70grn Ballistic tip traveling at 3500fps. The bottom line, mine was faster, but his was fast enough and more accurate. He made consistent hits at 400, 500, and 600 yards. Of course he had to dial up more MOA than I did, but who cares when you can make shots consistently like that. He let me shoot his 6BR, I was so impressed with the accuracy, I told my self I was going to have to build one. I madE my fair share of hits with my 6x284, but this guy was deadly accurate with this thing and when he let me shoot it, I was too.

Even at the longer ranges from 700 to 1000 yards, his 6BR was awesome. He had a different load for shots past 600 yards, I believe he was using a 105grn Berger.

Here is my two cents. If your going to be doing the majority of your shooting past 700 yards, than I would go with the 243AI only because of the added velocity. However, if must of your shooting is going to be done from 100 to 600 yards, go with the 6BR.

 

[chino1969]

thanks for the excellent idea there chino69, is the savage single shot actions pretty good? i hope so, that would be nice.
only bad thing i can see is that the longest barrel they show is a 26" for the drop ins.

Hopefuly they still shoot well..

Scott,
Yes the Savage single shot action is a good action, especially for a varmint rig. Pac Nor will give you a longer barrel if you need one but my question is why? My .243 A.I. barrels are approx. 26", my 6mm BR is approx 24". Incidentally, I have several blueprinted Remington varmint rigs that I had put together before I went the Savage route. In my opinion, especially for a varmint rig, Savage is one of the most accurate and economical ways to go. When I was thinking about putting another rifle together several years ago I was going to buy a Nesika action,$1100.00) and then a McMillan stock,$500.00) have a benchrest gunsmith chamber and provide a Hart or Kreiger barrel,$500.00) along with a Jewell trigger,$200.00). There would have probably been another $100.00 to bed the action. Now this was just to whack varmints. I had been reading, with alot of interest, articles about Savage rifles. I was at the range one day shooting beside a fellow who had just had a Savage rifle put together by Fred Moreo of Sharp Shooter Supply. I was impressed with the accuracy, quality, and price of his rifle. I called Sharp Shooter Supply the next day and asked Fred Moreo what he would charge to put together a .243 A.I. with a Savage single shot action. Fred put together a Savage single shot action, installed one of his competition triggers, trued and timed the action, precision ground recoil lug, Douglas 1:10" barrel, bedded the whole package in a fiberglass varmint stock, and the price was about 1/3 of what my original plan would have cost. I've since acquired several match grade Pac Nor barrels and another Douglas. Seriously look into the Savage. Sharp Shooter Supply has caught on and Fred Moreo is very busy but try calling the shop. Lisa, his wife, is very nice and they are great people to deal with. Pac Nor is another great company to deal with.
Chino69

 

[Scott7m]

that sounds great chino, i'll probably end up going the savage route, no point in building a benchrest gun to shoot varmints..

now a scope question? when you guys talk about dialing in moa? I'm curious to how that works, i only have one true target scope and never touched the turrets on it becaue it's my dad's. but when you see a ground hog pop up at lets say 480 yards, and you know your gun will be shooting 16 inches low at that distance? what do you guys do, turn the turrets 4X that many clicks? and then hold center and fire?

also if you do that, and then put your scope back to where it is supposed to be, you better hope your scope is working perfect. i'm kinda confused about how all of that works but it sounds good. i've read that zeiss scopes have the most precise internal adjustments.

 

[Scott7m]

are there any advantages or disadvantages to the improved versions of the 6mm br?

 

[chino1969]

Well, Scott, if you are going to get into long range varmint whacking there are several things you'll have to do to shoot groundhogs at distance. Once you have a good load developed that is accurate you'll need to determine the velocity with a chronograph. I usually zero my varmint rigs at 200 meters. The range I belong to has backstops at 100,200,300,400 & 500 meters. The nice part is that setting up at one bench allows you to shoot all these yardages by only changing your angle and elevation, as the different ranges are tiered behind the front one and offset to the left or right of each other. I will run my velocity through a ballistics program to develop a click chart at the different yardages. You can also come up with your drop by looking at the back of any good reloading manual once you have your velocity. At any rate, you'll need to shoot the distances you intend to shoot and determine how many clicks you need to come up to hit a groundhog at say 400 yds. I don't want to confuse you by going deeper but that is the general idea. A rangefinder is a must for determining the distance to your target.
Chino69

 

[Scott7m]

yeah thanks for the help... it's starting to make sense.
honestly shots here over 400 yards are pretty rare.. the terrain usually just does not allow for it. seen my dad kill a crow at 660 with a 22-250 one time but that happens i guess...

I guess i'm really just looking for something that really surprises me with its accuracy capabilities, but yet the main purpose is going to be whacking varmints and especially coyotes..


unfortunately, there are no ground hogs in our area anymore.. groundhogs used to be very thick here, as we could go hunt any evening and see a lot, now we may see 1 - 2 per year.. i don't know what happened to them.. coyotes maybe?

 

[Scott7m]

as i continue to read and research the choices are endless....... but i think i'm leaning towards a real screamer vs. the most accurate. i'll read where some will talk about how accurate the br is holding groups, then i'll see someone getting great accuracy out of a real screamer too....

i'm going to ttake chino's advice and get one i can switch barrels with.... right now i'm just looking for something that shoots like a laser but yet is really accurate.

most of the info i find for the 6.5-284 is using heavier bullets, anyone ever try like 87's in it?

 

[AndyW]

Scott,

I own a 6mm Remington,very close to the .243AI velocities) and a 6mmbr. These guns are twins with the exception of the caliber difference. Both are semi-custom varmint guns built on the remington VSF platform with custom tubes, trued action, jewell trigger and Leupy 8.5-25x50 scopes. I mostly use them for paper punching and coyote hunting.

I shoot the 87 Vmax out of the 6mm rem @ 3450fps and the 75 Vmax out of the 6mmbr @ 3350fps. The 6mm Rem is accurate, and the 6mmbr is ultra accurate, and because of this it has become my go-to vermin gun. The speed thing wears off in a hurry when you have a tack driver in the safe that is just plain more fun to shoot. BTW- the 6mmbr with the 75 Vmax is no slouch in the speed department @ 3350 fps with the 75 grain Vmax!

On most of the long shots I take I am packing a rangefinder anyway, maybe 2 MOA at 550 yards is the only difference in the above example.

Go with the 6mmbr.

 

[Scott7m]

yeahhhhh thanks for the help again.......... everyone is chanting 6mmbr, and i feel that you guys know what your talking about! So it looks like that will be what I go with in chambering this rifle..
Cant' wait to get started

 

[Preacher]

6mmBR is the one to do, I have Varmint rifles chambered in 6mm AI's, 22/250AI's, 220 Swift AI's, and a bunch of others but when I get serious about poking a groundhog in the nose at 300+ yards I ALWAYS reach for one of my 6br's.....
I just wish I had known about them years ago........... Actually I did, but being old and set in my ways I didn't figure that puny little bitty case could do it all up as good as it will.........
You may end up with lots of others, but you'll never forget what that little 6br case will do for you........

 

[chino1969]

yeahhhhh thanks for the help again.......... everyone is chanting 6mmbr, and i feel that you guys know what your talking about! So it looks like that will be what I go with in chambering this rifle..
Cant' wait to get started

Well, you won't be disappointed but you may become spoiled. Most people who have their first 6mm BR are simply amazed at the accuracy. It is a fun cartridge to shoot. This is why I suggested the Savage action. You can have a 6mm BR barrel, a 22 BR, a .243 A.I., a .22-250 A.I., a .257 Roberts A.I., a .308, etc.
Chino69