.243 or 308 for AR10 build?

jstuck624

Sergeant of the Hide
Belligerents
Minuteman
May 10, 2014
256
51
Washington
Give your thoughts on which caliber i should choose.
looking for a target rifle for 800 yards and in.
leaning towards .243 for simple fact that it shoots flatter and has less recoil.
but I don't know the ins and outs of running that caliber on a gasser. If I'll run into cyclic issues etc.
also I want something that's easy to load for with lots of factory support. That's why I'm not goin 6 creed.
id like to load for it on a progressive.
thanks guys
 
Last edited:

TacticalDillhole

Shiner of shoes
Belligerents
Minuteman
Online Training Access
Jun 26, 2012
5,606
5,724
N. Carolina
Give your thoughts on which caliber i should choose.
looking or a target rifle for 800 yards and in.
leaning towards .243 for simple fact that it shoots flatter and has less recoil.
but I don't know the ins and outs of running that caliber on a gasser. If I'll run into cyclic issues etc.
also I want something that's easy to load for with lots of factory support. That's why I'm not goin 6 creed.
id like to load for it on a progressive.
thanks guys
My opinion, .308. I don’t think you will get the benefit of a .243 out of a gasser. I’ve actually never seen a 243 AR. Not to mention the barrel life difference. I think you would be much happier using the tried and true 308.
 
  • Like
Reactions: XLR308 and Kryan

7mmFanBoy

Private
Belligerents
Minuteman
Jul 31, 2017
115
21
WI
More energy 308 steel noise, impact dirt spot misses. Run no brake heavy ar10 308 keep the steel ringing every couple secs out 600 ez.
 

NukeMMC

Damn Bubblehead
Belligerents
Minuteman
Online Training Access
Mar 3, 2009
1,235
558
Harrisburg, PA
For 800 and closer, you will not realize the benefits of a smaller caliber to the extent that the reduced barrel life and effort to make the reliability of function for the smaller calibers is economical in terms of money or frustration. If you want the reduced recoil, shoot a brake or silencer and tune the buffer weight and gas. I have an AR10 in 308 and a GAP10 in 260. Both are threaded/profiled for my Ops Inc silencer and I also have Area 419 Hellfire brakes to attach on them. I am still getting used to the report and backblast from the brakes, so my accuracy is suffering, but the recoil is SIGNIFICANTLY reduced from bare muzzle and is slightly better than with the silencer.
 
  • Like
Reactions: XLR308

Strykervet

DEEZ NUTZ DEPUTY DOG!
Belligerents
Minuteman
Jun 5, 2011
5,348
3,957
44
Pierce County, WA
I personally would buy a new .308 unless you have tools and such along with knowledge of parts compatibility, etc. I think you come out on top with a quality rifle, like a KAC or Larue, etc. I have a 20" SR25 (like the new M110's) and it's great, I couldn't build a rifle like that, especially for the price I paid for it. Costly, but only thing I needed to change on it was the pistol grip --wanted a Magpul Miad.

I thought about a 6.5 upper, thought about building a rifle, then decided I'd rather have a good 6.5 bolt gun instead. I do have a Grendel, and it's amazing for anything out 800m+. It's great.

I'm totally happy with the SR25 and what I have into it, it's an amazing rifle and I couldn't have built one like it, like I said. Without handling one, it just looks like any other AR, but it's anything but. Almost completely proprietary from barrel and gas block to BCG to the lower and controls. An amazingly well designed and built rifle. The factory suppressor is pretty nice too, indexed and locks on solid with a twist of the wrist. Best mags available IMO. It's also totally reliable as well as accurate.

OBR may be a better rifle in some aspects, but it has a long wait. Or did when I was in the market.
 
  • Like
Reactions: XLR308

Potss

Full Member
Belligerents
Minuteman
Feb 16, 2017
727
200
OP for your needs it sounds like .243 is pretty perfect. Keep in mind the .308 will be cheaper to buy ammo for though. But if you don't mind paying a bit more per round, the .243 will be flatter and have less recoil.
 

steve123

Lt. Colonel
Belligerents
Minuteman
Mar 16, 2008
8,858
1,339
Flagstaff, AZ
The most reliable AR large frame I've ever had was a DPMS in 243. It didn't shoot the best but it was a cheap factory rifle. A 20" barrel really cuts it's balls off, in the high 2700's with 105 Amax.

Had a heavy barrel 308 DPMS too. I liked the 243 better.

Just for comparison. I had a AR in 243 WSSM, the recoil impulse was much less than the 243 large frame because of the much lighter BCG. Which got me thinking...

Now I shoot a 6MMFatRat in AR. That's the ticket, it's braked, 95's at 2870 fps and an incredibly soft shooting and accurate semi auto! I don't need anything else for a long range fun gun. OT I know but it's so awesome it's worth mentioning.

 

jstuck624

Sergeant of the Hide
Belligerents
Minuteman
May 10, 2014
256
51
Washington
Hmm...you guys all make good points and are starting to sway me towards the 308. I also like the fact that I can use cfe223 or 8208 xbr to load for it. Plus I can probably find a decent used rifle similar to what I want for much cheaper then buying a new one.
thanks guys
 

NewsShooter

Sergeant
Belligerents
Minuteman
Sep 14, 2011
786
210
60
I've got a couple 6.5 bolt guns so I put together a 6.5 aero precision kit. Took it out today to dial in the adjustable gas block. Only took a few minutes, recoil was less than I thought it be for a large frame AR. I also put a hellfire brake on it and I was able to spot all my impacts from the very first shot.
 

Forward543

Sergeant
Belligerents
Minuteman
Feb 14, 2017
592
162
.243 or 6.5. .308 is real nostalgic and would absolutly work, but i prefer a little more speed and a better bc.
 

FCS

Gunny Sergeant
Commercial Supporter
Belligerents
Minuteman
Jun 3, 2005
2,046
391
ABQ, NM
www.mccourtmunitionsllc.com
6.5 Creed or 308 would be best fit given parameters in original post.
243 can be made to work and work well but to make a243 gas gun shoot accurately and drop dead reliably, you'll have more issues than going with 6.5 Creed or 308.
 

bigjake83

Golden Shellback
Belligerents
Minuteman
May 19, 2013
3,297
905
Southern Idaho
OP don't forget that if you like the 6mm cartridges you don't need an AR-10, you can get a 6mm Fat Rat in the AR-15 platform that loses nothing to a 243. You get all the ease of shooting an AR-15 compared to an AR-10 and lose nothing as far as ballistics are concerned. I'm getting 2840fps out of 95gr TMKs and 2780 from my 107 SMKs.

That's pretty impressive since if you already own an AR-15 all you need to build is an upper not a full AR-10 build.
 

jstuck624

Sergeant of the Hide
Belligerents
Minuteman
May 10, 2014
256
51
Washington
OP don't forget that if you like the 6mm cartridges you don't need an AR-10, you can get a 6mm Fat Rat in the AR-15 platform that loses nothing to a 243. You get all the ease of shooting an AR-15 compared to an AR-10 and lose nothing as far as ballistics are concerned. I'm getting 2840fps out of 95gr TMKs and 2780 from my 107 SMKs.

That's pretty impressive since if you already own an AR-15 all you need to build is an upper not a full AR-10 build.
What's this fat rat cartridge? I need to Google it
 

jstuck624

Sergeant of the Hide
Belligerents
Minuteman
May 10, 2014
256
51
Washington
6mm AR with 40 degree shoulder, shoulder moved forward some. Need to form brass, there is no factory ammo available though I'm sure you could find one of the custom ammo companies who would load it for you.
6mm Fat Rat is very similar to 6mm AR Turbo.
http://6mmar.com/6mmAR_Turbo.html
I see. So is there a necked down 6.5 Grendel?
I'd like to not have to do a ton of work to the brass. This thread has got me thinking about just changing the barrel on my ar15 to 6.5 Grendel and loading it on my progressive with 8208
 

FCS

Gunny Sergeant
Commercial Supporter
Belligerents
Minuteman
Jun 3, 2005
2,046
391
ABQ, NM
www.mccourtmunitionsllc.com
6mm AR is the 6.5 Grendel necked down to 6mm, shoulder angle stays same. 6mm AR (30 degree shoulder, same HS as 6.5 G), 6mmAR Turbo (30 degree shoulder but shoulder moved forward) and 6mmAR Turbo Imp (40 degree shoulder and shoulder moved forward) so you have plenty of options. Dies available from 6mmar.com website.
6.5 Grendel set up "right" works really well with 8208 and 120 / 123 gr bullets.
 

steve123

Lt. Colonel
Belligerents
Minuteman
Mar 16, 2008
8,858
1,339
Flagstaff, AZ
OP, from past experience I can tell you a premium barrel like Krieger or Bartlein should be the top priority in a AR build. Worth the extra money.

6mmAR would be a great choice, one neck down and you're shooting. After trying 105's and the 95's I stayed with the 95 SMK.

Experimenting with different barrel lengths and contours I think a medium weight 22" is about perfect. You could expect 95's out of a 6mmAR in a 22" to be right around 2750 fps.

Again, most of the draw is a very accurate and low recoiling AR and it doesn't hurt that Lapua brass lasts a long time and it's very consistent in quality.

Even though it's a little of a hassle the Fat Rat is worth going through the forming for the extra 100 fps.

I'm keeping my eye on the 224 Valkyrie. If the brass can withstand normal pressures and exhibit long brass life, which remains to be seen, that could be a great cartridge for the AR. I wouldn't be surprised if 2750 fps with 90's(.53 BC) out of 22" barrel was normal.
 
Last edited:

FCS

Gunny Sergeant
Commercial Supporter
Belligerents
Minuteman
Jun 3, 2005
2,046
391
ABQ, NM
www.mccourtmunitionsllc.com
224 AR should equal the 224 Valkyrie but has advantage of Lapua brass. Valkyrie has advantage in factory ammo. Hmmmm.....if only there was a source for 224 AR ammo. Might have to make some phone calls on that.
 

millertime2

Private
Belligerents
Minuteman
Jan 16, 2010
188
26
43
Illinois, USA
I have a Remington R25 I bought for a song used. I shoot 80 grain noslers and have no problem hitting a 10" target at 650 yards. Yes barrel life I'm sure will be reduced compared to a 308 but I love this thing for coyotes. I was planning on rebarreling to 6.5 creed when it's time but am really thinking about going back to .243 but running a faster twist so I can get up to 105's.
 

MarkCO

Full Member
Belligerents
Minuteman
Dec 21, 2010
669
79
Colorado
www.CarbonArms.us
Having walked down this path a few times myself, I'd look at the 6mm options in the AR15 platform. I really like .243Win (5 bolt guns), and I want a .243 barrel for my .308 pattern AR, but I still don't have one since you can get 90% of the way there with an AR15 pattern for less $.
 

Greg Langelius *

Resident Elder Fart
Belligerents
Minuteman
Aug 10, 2001
8,534
4,420
74
Arizona, good place for me...
I have shot my (now rebranded from Stag Model 6) Stag 15 Varminter in F T/R MR comp at 600yd with very basic handloaded Hornady 75gr HPBT Match (Win 223 Brass, 24.4gr Varget, magazine length). Depending on altitude (at 1600ft ASL, it's still going 1445fps at 800yd...source: Hornady Ballistic calculator, 2875fps MV)), it can go further reliably.

When you figure I built it in a snap (literally under an hour) from a (24", 1:8" SS Bull Barrel) kit for under $750, and the handloads work nicely without requiring any Kama Sutra/Secret Squirrel handloading (RL550) moves, it's really not such a bad price for a pretty decent approach. Nothing to learn, easy to feed, and it's a really refined (and warranted) commercial design.

Even cheaper today only. Kit includes Stag 2 Stage Trigger | 2 lb first stage with a 3.5 lb let-off Needs one of these, too,(mine is engraved 'Any')..

Greg
 
Last edited:

Ernie20147

Private
Minuteman
Sep 27, 2019
4
0
I was wondering if anyone had any thoughts about if a .243 AR -10 would be effective in defeating the steel plate body armor of a drug cartel or in a "Red Dawn" type of scenario ( not that I saw that masterpiece) in defeating the steel plate body armor of an invading army - just hypothesizing...I have heard that the high velocities of some of lower grain .243 rounds could punch through. Of course, maybe I have been watching too much YouTube.
 

diggler1833

World's Okayest Rancher and Hog Hunter
Belligerents
Minuteman
Jul 22, 2007
1,294
1,530
41
Oklahoma
A necro-thread simply to test the effectiveness of your tin foil hat, huh? 😆

Speed defeats armor. However, if you're at the distance where it's too far to make an accurate headshot...your too far away for your fast .243 to punch armor as well.
 

Ernie20147

Private
Minuteman
Sep 27, 2019
4
0
A necro-thread simply to test the effectiveness of your tin foil hat, huh? 😆

Speed defeats armor. However, if you're at the distance where it's too far to make an accurate headshot...your too far away for your fast .243 to punch armor as well.
Just trying to figure these forum hodaleedadels out. Next question is where to find a reasonably priced ($250-$450), fairly lightweight barrel that would be compatible with freely available bolts/uppers. I would like to build something around the weight of the Wilson Combat 243 WC-10s for the price of the Rock River 243 LAR-10s. If I could use Aero Precision receivers that would be nice as well.
I am really thinking (it is hard with the aluminum shield over my brain and the high CO2 levels trapped inside my China virus mask) for 100 yards in scenarios. I only came to SH for two reasons, one they are the only open thread that were talking AR-10 243 yrs technically it is called LR-###; but when you are looking for 243 ARs that LR-### name really messes up the search engines. The second reason for coming to SH is that the members of the forum know their stuff in the technical sense. And I just thought of a third reason for using this forum, there is a lot less drama "...an armed society is a polite society..." .
Hammer those hogs.
 

hlee

Sergeant
Belligerents
Minuteman
Jul 14, 2012
4,088
3,971
42
TX
224 AR should equal the 224 Valkyrie but has advantage of Lapua brass. Valkyrie has advantage in factory ammo. Hmmmm.....if only there was a source for 224 AR ammo. Might have to make some phone calls on that.
My 224 predator (224 ar, lbc, whatever) is shooting 88 grain eld-ms at 2760, which is about 100 FPS faster than what Hodgdon says a valkyrie can. This is from a22” ar-15, and I don’t have a Valkyrie for direct comparison. I’d love factory ammo...
 
  • Like
Reactions: Constructor

FarmBoy87

Banhammer
Banned !
Minuteman
Sep 4, 2020
43
15
I have a 6mm Predator with a Titan bolt so I can run higher pressure and with my 22" barrel I sacrifice very little to a factory 243 and its light and high capacity.
 

Nimothy

I’m trying
Belligerents
Minuteman
Nov 14, 2018
777
268
Dallas Texas
The most reliable AR large frame I've ever had was a DPMS in 243. It didn't shoot the best but it was a cheap factory rifle. A 20" barrel really cuts it's balls off, in the high 2700's with 105 Amax.

Had a heavy barrel 308 DPMS too. I liked the 243 better.

Just for comparison. I had a AR in 243 WSSM, the recoil impulse was much less than the 243 large frame because of the much lighter BCG. Which got me thinking...

Now I shoot a 6MMFatRat in AR. That's the ticket, it's braked, 95's at 2870 fps and an incredibly soft shooting and accurate semi auto! I don't need anything else for a long range fun gun. OT I know but it's so awesome it's worth mentioning.
Ar15 is 243 wssm. That sounds pretty cool. What barrel length? What mags did you run?
 

oldfart80

On Duty
Belligerents
Minuteman
Dec 17, 2019
670
1,939
A buddy of mine had an Armalite in .308 & asked me to site it in and find some ammo it liked. Went down and bought a box of Fed Fusions in 150 I think. Clumped 5 shots into an inch & then went out and shot two doe with it over the weekend. Cool guns no doubt.
.308win has such a wide variety of ammo and can be found anywhere. If you want to shoot it a lot go this way. If you have to have more firepower, then the 30-06 would be my next choice.
 

Constructor

Private
Belligerents
Minuteman
I was wondering if anyone had any thoughts about if a .243 AR -10 would be effective in defeating the steel plate body armor of a drug cartel or in a "Red Dawn" type of scenario ( not that I saw that masterpiece) in defeating the steel plate body armor of an invading army - just hypothesizing...I have heard that the high velocities of some of lower grain .243 rounds could punch through. Of course, maybe I have been watching too much YouTube.
A 243 will not defeat L III, III+ or IV steel, it may defeat the LIII poly or ceramic if you put 2 very close together. I've tried Barnes 75gr solids(brass) on AR500...no go.
 

steve123

Lt. Colonel
Belligerents
Minuteman
Mar 16, 2008
8,858
1,339
Flagstaff, AZ
Ar15 is 243 wssm. That sounds pretty cool. What barrel length? What mags did you run?
I think it was a 24". It was an Olympic Arms upper and whatever mags they were selling with it. It was unreliable and not very accurate, I regretted buying it. Fast, sure it was, but that isn't everything.

The worst thing about 243WSSM brass was how poorly made it was, timeframe of a 12 years ago. The necks were as much as 2.5 thou from one side to the other. Flash holes were not centered. When rolled across a flat surface many cases would wobble. A third the cases wouldn't fit in the shell holder.
It started out as a 2.5" 100Y upper. After brass prep and load work I was lucky to get 1.25".

The 6mmART40 was the opposite. Lapua brass and extreme precision for an AR. I shot a 3/4" 10 shot group with one opening up an otherwise .35" group! Even won a match against bolt rifles. It also kicked our ass at 810Y on a 8" steel. My friend borrowing it on one occasion kept dinking the steel and the rest of us with bolt rifles were struggling.
 

KenRUM

Private
Hessian
Minuteman
Jan 20, 2019
34
2
Fruita, CO
I'm not sure if anyone else has suggested it yet, but how about a 6mm Creedmoor in an AR10? It has better factory loadings than the 243 as far as match ammo goes. Yeah it's probably overkill for 800 yards and in but so are any of the other options.
 

eastexsteve

Sergeant of the Hide
Belligerents
Minuteman
Nov 18, 2018
304
193
NE Texas
I was wondering if anyone had any thoughts about if a .243 AR -10 would be effective in defeating the steel plate body armor of a drug cartel or in a "Red Dawn" type of scenario ( not that I saw that masterpiece) in defeating the steel plate body armor of an invading army - just hypothesizing...I have heard that the high velocities of some of lower grain .243 rounds could punch through. Of course, maybe I have been watching too much YouTube.
Do you think you would survive a direct hit in the chest with a FMJ 308 at 100 yards even if you had on body armor? You're talking about a ton of energy striking you in the chest, even at that distance. Why reinvent the wheel?
 

Ernie20147

Private
Minuteman
Sep 27, 2019
4
0
A 243 will not defeat L III, III+ or IV steel, it may defeat the LIII poly or ceramic if you put 2 very close together. I've tried Barnes 75gr solids(brass) on AR500...no go.
thanks for your reply. I was curious as to the barrel length and range that you did your tests with? I had been thinking of much lighter grain (55-60) projectiles at 100 yards or less (yes, I realize that I am asking these questions on a forum called snipers hide and not rock throwers hide ;) ).
 

Ernie20147

Private
Minuteman
Sep 27, 2019
4
0
Do you think you would survive a direct hit in the chest with a FMJ 308 at 100 yards even if you had on body armor? You're talking about a ton of energy striking you in the chest, even at that distance. Why reinvent the wheel?
it would knock your average soldier down and out with a couple of broken ribs most likely. In the current American army, that would tie up maybe 20 people taking care of one wounded soldier. I'm talking about something like the Chinese Army in the Korean war, where they didn't even give the third wave of attacking Chinese soldiers rifles. Their officers just said to pick up rifles from the Chinese dead in the first two waves. It was an Army that didn't care about their soldiers. I think I am getting a little off track here, but putting a little fear of death over broken ribs into an invading army is a good thing.
 

Constructor

Private
Belligerents
Minuteman
thanks for your reply. I was curious as to the barrel length and range that you did your tests with? I had been thinking of much lighter grain (55-60) projectiles at 100 yards or less (yes, I realize that I am asking these questions on a forum called snipers hide and not rock throwers hide ;) ).
20yds, 24" barrel. Lead core bullets 223 or 243 will not defeat 1/2" mild steel but will pass through 1/4" mild steel. I tried 55gr FMJ at 3540fps, they would not pass through 1/2" mild steel. M855 made a hole about the size of pencil lead. A buddy was testing for a cheap armored vehicle idea to refit a humvee . The only bullet we found that would penetrate LIII+ is the 30-06 black tip
 

Disfunctional_Engineer

Sergeant of the Hide
Belligerents
Minuteman
Jul 27, 2020
310
350
I'm not sure if anyone else has suggested it yet, but how about a 6mm Creedmoor in an AR10? It has better factory loadings than the 243 as far as match ammo goes. Yeah it's probably overkill for 800 yards and in but so are any of the other options.
The 6 Creed vs 243 is an interesting proposition in my mind. I have a 243 AR-10 and would not want one if I didn't reload. The vast majority of factory ammo choices for it are hunting focused and quite frankly terrible for at distance stuff. It's not like you're going to get some GMM for it unless you want ones with Game Kings. The price compared to other similar function ammo isn't terrible once you get out of cheap surplus land which the .308 likewise wins hand down. Then again I've seen 243 on shelves I have seen zero 308 lately.

From what I've read about 6 Creed you should really have a +2" gas system with it. If I bought another 243 barrel and had the choice I'd probably do +2 gas with it as well so I could run slower powders and a 7.3 twist for something like 115 DTACs. That said the initial testing I've done with mine looks good in allowing for slower burning powders (just not super slow like H1000, Retumbo or Magpro.) Looking at Nosler's site they're saying a 40ish FPS difference at most in the win for 6 Creed. Not a huge swayer in my mind.

In an 18" gun with a rifle length gas system it's a kitten to shoot, lots of fun (my 8YO loves it,) accurate and reliable. I can say I've had one FTE in it ever and that was a book minimum reload which means it was probably under gassed at that point. The fact that I'm running PMAG 25s and have zero worries of anything Creedmoor specific being required would also be a huge boon in my book. I want to try a D50 for shits and giggles once but don't want to just burn up 50 rounds of ammo or barrel life to do such. ED:I also forgot to mention it was reliable with 58-105gr ammo, it just eats ammo up and doesn't care.

Re:Body armor no idea, it's interesting to see the tests though. I'm kind of surprised about the inability to punch through. That said if cracked ribs are a real issue there's always the old fashioned method which is a 12ga or perhaps if you're into new age some heavy 458 SOCOM or 450 Bushmaster rounds.
 
Last edited:

eastexsteve

Sergeant of the Hide
Belligerents
Minuteman
Nov 18, 2018
304
193
NE Texas
it [308] would knock your average soldier down and out with a couple of broken ribs most likely.
It takes a pretty stout steel or ceramic plate vest to keep a FMJ 308 from doing some deadly damage to you at 100 yards. We are not talking about 7.62X39 or 5.56 here. Most vests or flak vests won't protect you. See the below video where they are shooting .308 AP rounds through some amazing stuff - including AR500 armor plate.
 
Last edited:

Orphanedcowboy

Darryle
Hessian
Belligerents
Minuteman
Mar 24, 2010
92
45
55
Weatherford, Texas
I have built every version of the 308 parent case AR, except for the 6mm Creedmoor. That is about to change.

I would not build a 243 unless I could find a 8.5 or 9 twist barrel and then I would not even consider a 308. With that said, I would build a 6mm Creedmoor if you intend to shoot heavy for caliber bullets.

Which ever you choose, make sure it has a Slash's HeavyBuffers.com buffer kit in it and cyclic issues won't be an issue.
 

Disfunctional_Engineer

Sergeant of the Hide
Belligerents
Minuteman
Jul 27, 2020
310
350
I have built every version of the 308 parent case AR, except for the 6mm Creedmoor. That is about to change.

I would not build a 243 unless I could find a 8.5 or 9 twist barrel and then I would not even consider a 308. With that said, I would build a 6mm Creedmoor if you intend to shoot heavy for caliber bullets.

Which ever you choose, make sure it has a Slash's HeavyBuffers.com buffer kit in it and cyclic issues won't be an issue.
My mcgowen barreled 1:8 twist runs great with a standard M4 buffer/spring setup. It's soft, like Drake soft. Fixed gas as well.

https://www.midwayusa.com/product/1019472895

I saw these on sale and was lucky enough to pick one up for all of $135! I'm curious to see how it does but that'll hopefully be some time off at this rate. If worse comes to worse I'll convert it into bushings or some other parts on my lathe but for the price why not? Reviews say sub MOA so I figure if I get 1500-2K rounds out of it I can move up to a better barrel when I suck less. 🤣
 
  • Like
Reactions: Orphanedcowboy

Unknown

Gunny Sergeant
Belligerents
Minuteman
Sep 17, 2009
3,743
911
Pacific Northwest,USA
I used to have some .5" mild steel plates that I would shoot with a 5.56 at 200 meters (about 220 yards). The standard 55 grain ball would badly divot the steel at 200 meters. I set one up at 50 yards and the 55 grain ball punched right through it. That was when I decided that plain Jane 55 grain 5.56 ball ammo would do 98% of anything I asked it to. I would think that most car doors wouldn't provide too much cover from a 5.56 ball round, but two doors probably would.

I put the same plates behind railroad ties at 200 meters and 7.62X51 ball ammo (147 grain) would punch through the railroad tie and still knock the plates over, but 5.56 ammo would always stick in the railroad tie.

WWII 30-06 black tip would punch right through the half inch mild steel plate at 200 meters and leave a hole that looked like a 5.56 or .243 hole. The copper jacket would often be stuck in the hole that the penetrator went through.

I know this isn't scientific testing, but with my limited access to better testing facilities, I decided that I finally knew which weapon system to grab for various "jobs at hand".
 

DavidAR10

Sergeant
Belligerents
Minuteman
Aug 12, 2010
528
48
63
Dallas, Georgia
RFA on both.
That's wRong Fucking Answer for those that
live in Rio Linda.

6.5 Creedmoor FTMFW.

Well hell, I'm an old caveman and I know that!

BUTT!!! Out of your chosen TWO: 308 WIN

Go have fun.
 

Constructor

Private
Belligerents
Minuteman
I have built every version of the 308 parent case AR, except for the 6mm Creedmoor. That is about to change.

I would not build a 243 unless I could find a 8.5 or 9 twist barrel and then I would not even consider a 308. With that said, I would build a 6mm Creedmoor if you intend to shoot heavy for caliber bullets.

Which ever you choose, make sure it has a Slash's HeavyBuffers.com buffer kit in it and cyclic issues won't be an issue.
Why 8.5 or 9, we have been using 8 twist barrels for 12 years with 105s and 108s. I think the 115s and 17s need a faster twist and the 110 SMK definitely needs a 7 or 7.5 twist?
 

Orphanedcowboy

Darryle
Hessian
Belligerents
Minuteman
Mar 24, 2010
92
45
55
Weatherford, Texas
Why 8.5 or 9, we have been using 8 twist barrels for 12 years with 105s and 108s. I think the 115s and 17s need a faster twist and the 110 SMK definitely needs a 7 or 7.5 twist?
That is even better if you are going to shoot nothing but those heavies, that is why I referenced the 6mm Creed since both would have to be reloaded.

There are just not enough fast twist 243 Winchester barrel manufacturers out there, most are 10 twist, but most every 6mm Creed is a much faster twist
 

Disfunctional_Engineer

Sergeant of the Hide
Belligerents
Minuteman
Jul 27, 2020
310
350
That is even better if you are going to shoot nothing but those heavies, that is why I referenced the 6mm Creed since both would have to be reloaded.

There are just not enough fast twist 243 Winchester barrel manufacturers out there, most are 10 twist, but most every 6mm Creed is a much faster twist
243 is a hard thing to find in an LR308 build honestly. 6.5 Creedmoor took over the world pretty much and 243 stuff went away by and large. That said the Midway barrel above was 8 twist. I would be hesitant to have a 10 twist unless factory ammo was a requirement. My Mcgowen barrel was something like $250 on a Black Friday deal and $300 without flutes now. Well worth the cost to get what I actually wanted. Next one will be fluted, 20", 7 or 7.5 twist and +2 gas I think.

As a question to the others here who have had it, what's the heaviest weight you've gotten away with at 1:8? I am shooting 105s right now but haven't taken them to a decent length range, nor have I tested heavier. I was tempted to grab some of the 115 DTACs that seem to be sprouting up for sale in the PX to play around with but an not confident they'd stabilize especially in the short length 18" barrel. I think I'd wind up down about 225 FPS compared to a 24" barrel based on what I've seen online and I just don't think that's enough spin to give the super heavy bullets a fighting chance although I'm open to being told otherwise.
 
Last edited: