.243 Gas system.

J

jk2paintworx

New member
I am starting on a lightweight .243 that I will be using for coyote hunting. I have built several AR15 platforms but this is my first large frame. I am using 18” X Caliber .243 1:10 twist barrel with Rifle length gas port and a adjustable gas block.

But I’m not sure what BCG/Spring system to use. I have my eye on the JP LMOS because It’s only 9oz but not sure the light carrier is enough weight to run the rifle reliably and not sure I can have the best of both world (light and reliable). Also not sure what buffer/spring system to use.

Does anyone have experience with getting the 6mm AR10s to run well? They sound like they are a little more finicky than the AR15s And the parts are spendy when shaving weight so I wanna get it right the first time. I will be shooting suppressed 100% of the time and using lighter weight bullets 55-90gr
 
Both of our bca ambedextrios 20" 243's run fine with standard rifle gas and the pa10 lowers from Palmetto. I just pulled a buffer and spring out of the stock and the spring is quite a bit shorter than a standard AR-15 rifle buffer spring and the buffer is a little bitty short thing. I guess the AR-10 bolt carriers are just that much longer. I would start with the standard parts for the LR 308 and see where you're ejected brass ends up and how it cycles.
Found this on another forum.....The buffer is 2 17/32" long and weighs 3.7 oz. The buffer spring is 11 7/16" long.
 
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Don't over think it. I pulled my ACE stock off one of my AR15 lowers and slapped it on my 20"243 and went hunting.thrown adjustable gas block on and shoot.
 
I think JK realizes he can make it work fine with standard parts, he's trying to save weight and wondered what experience anyone might have with light weight options for bcg and what buffer and spring would make it work right.

Having said that, I'll admit I have no clue how well the lmos works.
 
I haven't gone down the rabbit hole of saving a few ounces with moving components with a large frame, I chose carbon fiber components (barrel, stock and handguard) I did try shaving weight on an AR15 With BCG and buffer system to shave weight for my 5yr old to deer hunt with. Once i got it to finally cycle, it kicks like a mule and is still finicky. It's very tempermental with bullet weights
 
That's basically what I meant if you're going with the lightweight BCG Etc I would throw the standard buffer and spring in it because the standard stuff is normally the cheapest and just see where your brass ends up.
Just guessing here but I'm guessing going lighter on the reciprocating parts may take less gas to do it but then depending on how hard the round chambers because of the extractor getting over the rim and overcoming drag in the magazine you're still going to require a stiff spring which in turn is going to require more gas I just don't see it as a realistic place to shave weight.
Reciprocating parts and the last 2 in of muzzle are places that I don't see as best places to save weight. However that's just my opinion.
 
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Honestly I would consider a dpms g2 16" 243 if I was looking for the lightest way to go. It would probably work well and be the easy way to go. Not as much fun as wrestling parts on a build but hey, sometimes easy is nice lol.
 
Originally Posted By: 204 ARHonestly I would consider a dpms g2 16" 243 if I was looking for the lightest way to go. It would probably work well and be the easy way to go. Not as much fun as wrestling parts on a build but hey, sometimes easy is nice lol.

I agree, I held my buddies the other day and I was blown away by it. He has a fluted 260 Remington barrel on it and ordered a couple 243 barrels. That rifle is the end all be all for predator hunting in my opinion.
 
Bear creek makes a 4 and three-quarter pound upper. I’m gonna order in the next couple of days. My aero lower weighs just under 2 pounds. So six and three-quarter pounds total minus optic and ammo. I don’t think there’s going to be too many AR 243’s lighter unless you’re going to spend a couple grand.
 
Originally Posted By: yotehunter243Originally Posted By: 204 ARHonestly I would consider a dpms g2 16" 243 if I was looking for the lightest way to go. It would probably work well and be the easy way to go. Not as much fun as wrestling parts on a build but hey, sometimes easy is nice lol.

I agree, I held my buddies the other day and I was blown away by it. He has a fluted 260 Remington barrel on it and ordered a couple 243 barrels. That rifle is the end all be all for predator hunting in my opinion.

I have the 20" version and it's very accurate. I ordered a couple spare barrels also, and was thinking of ordering a 260 barrel also. How does his 260 shoot, and how tough was it getting the carbon fiber tube off?

I built a pretty nice 243 7 or 8 years ago with DPMS receivers and a bhw barrel. It shot real well also, and was pretty decent handling with a carbon fiber float tube. But not near as nice, or visually appealing to my eye as the G2.
 
Originally Posted By: 204 AROriginally Posted By: yotehunter243Originally Posted By: 204 ARHonestly I would consider a dpms g2 16" 243 if I was looking for the lightest way to go. It would probably work well and be the easy way to go. Not as much fun as wrestling parts on a build but hey, sometimes easy is nice lol.

I agree, I held my buddies the other day and I was blown away by it. He has a fluted 260 Remington barrel on it and ordered a couple 243 barrels. That rifle is the end all be all for predator hunting in my opinion.

I have the 20" version and it's very accurate. I ordered a couple spare barrels also, and was thinking of ordering a 260 barrel also. How does his 260 shoot, and how tough was it getting the carbon fiber tube off?

I built a pretty nice 243 7 or 8 years ago with DPMS receivers and a bhw barrel. It shot real well also, and was pretty decent handling with a carbon fiber float tube. But not near as nice, or visually appealing to my eye as the G2.

He ordered it with a 308 barrel and pretty sure killed a bear or two in Alaska. I was surfing AR performance one day and he had G2 barrels in stock so I told my buddy and he ordered the 260. Been 4 years ago and hasn't shot it. I told him about your post and the 243 barrels cheap so he ordered some. He said the handguard was dumb but wasn't bad. I have a 22" carbon fiber 243 barrel due here any day and a 8.5oz handguard and barrel nut. I'm going to see how light I can get one
 
I’m going to order a BCA 20” 243 4 & 3/4lb upper later this week if,and, when I get a lee Enfield sporter sold to pay for it. I will weigh it with my claimed 31oz Aero lower Along with the butt stock added to check actual weight. I paid $200 on Black Friday for my complete A5 AR10 lower minus a stock. The current upper is $318. So for a $518 complete you can buy two sub 7lb AR 10’s for the price of a DPMS. My heavy 22” stainless 243 upper they sell for $380 shoots .3” groups with two different 55 grain loads so I know with the right hand load the 20” upper will shoot just as well if not better. My heavy BCA shot six sub MOA loads I tested the first time out so for a cheap upper I was impressed. I like the DPMS but I didn’t want to spend the extra cash on it.

I found my old post here with some groups from my First range session with my BC upper.

http://www.predatormastersforums.com/for...566#Post3209566
 
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Originally Posted By: DultimatpredatorI’m going to order a BCA 20” 243 4 & 3/4lb upper later this week if,and, when I get a lee Enfield sporter sold to pay for it. I will weigh it with my claimed 31oz Aero lower Along with the butt stock added to check actual weight. I paid $200 on Black Friday for my complete A5 AR10 lower minus a stock. The current upper is $318. So for a $518 complete you can buy two sub 7lb AR 10’s for the price of a DPMS. My heavy 22” stainless 243 upper they sell for $380 shoots .3” groups with two different 55 grain loads so I know with the right hand load the 20” upper will shoot just as well if not better. My heavy BCA shot six sub MOA loads I tested the first time out so for a cheap upper I was impressed. I like the DPMS but I didn’t want to spend the extra cash on it.

I found my old post here with some groups from my First range session with my BC upper.

http://www.predatormastersforums.com/for...566#Post3209566

Not trying to dispute your numbers, but looking at the $318 upper at bca it shows 4.75 lb, but also shows a gas block size of .875. That's semi-bull and pretty heavy, add a 15" rail and full weight bcg and I'm thinking they are a couple pounds off. Might be worth a call to verify. It is a very good price though, that's for sure.
 
Bca's website is not accurate. 20" 243 barrels are. 750 GB. I have the ambedextrios model. I think it was 13 # and change with my trail xp50 on it with no mag.
 
I called the day before yesterday to verify the weight. I’ll do it again today before I order. The gal I talked to told me the rear 20” charger was 4 &3/4 lbs and the ambi was 5.2 lbs. I have no interest in the ambi as it adds a half pound and I use it in the sandy washes. I can see sand in the ambi charger the first time I hunted with it. I’d rather stick with a dust shield model. I sold an old lee Enfield “freebie” that my buddy didn’t want and couldn’t sell to pay for it so I’ll be into it for nothing. Worse case Scenario if it’s a lot heavier than what it says it is I’ll just send it back since there’s a 30 day return policy. I think I’m gonna call and have somebody actually weigh it to verify. I know my 22 inch version is as heavy as a log. I never weighed it by itself but I’m sure it’s all of the 8.4 pounds they said it is. It’s a very fun in accurate upper but I’d like to have a light weigh upper for a walking varminter as well I can switch back-and-forth. I figured for $318 for a complete upper its worth a gamble.
 
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When I was saying their website wasn't accurate I meant on the gas block diameter meaning it is lighter than what the .875 would be. The barrel is basically what a standard contour AR15 barrel is as far as weight. Obviously the bigger receiver and BCG adds a little weight but I don't think the guns are that heavy. I use mine for night hunting and have a Radius rangefinder on it so it gets to be kind of heavy but when you've got thermal and range finders and Arca Swiss mount etc it all adds up.
Even at that weight it doesn't bother me because it's sitting on the pod most of the time or it's slung over my head across my shoulder. The bare gun is obviously a tad heavier than a standard AR-15 in the same barrel length but in my opinion not enough to counter the ability to sling projectiles at 243 speeds.
If it wasn't for all my 6x6.8's I would probably have another one for daytime hunting.
I will say after having the side charging and ambidextrous uppers that I will never go back to a rear charging. I convinced all my buddies to go side charging and they're all in the same boat now as well.

I had one of their 22 inch heavy barrels and those are just too heavy to lug around although it was accurate. It was a Stoner but I think the Stoners are BCA parts.
 
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I have a call into Bear Creek. They are going to weigh both 20 inch uppers and give me actual weights before I place my order today. The lighter one wins. I was told the other 20” rear charging model for five bucks cheaper is the older hand guard style(not the split rail) and weighs a half a pound heavier because the hand guard style??? They don’t have that one in stock anymore but they have up on their website for some reason. I don’t see how the hand guard would way a half a pound more. I remove the one off my 22 inch barrel and I don’t think it was a half a pound by itself and it’s longer. Guess I’ll have the answer shortly.
 
Some good info here guys, I just got a 22" side charger but waiting for the lower to get back in stock to take to the range. I thought the 20" & 22" were both heavy fluted barrels otherwise I would have went 20" if it was a lighter profile. Sure is heavy but looks nice.

Dultimat, the upper you were shooting 55 grain pills accurately with, was that an 8 twist? I am only interested in shooting light bullets and figure the 8 might be too much. I might just slap a BSF cf tube on it!
 
Nope, mine is a 1 in 9. It’s an AR stoner branded bear creek upper. The same stainless 22” upper they sold last year. Looks like they have changed twist rates 1/8 in their current 22” offering for some reason. It’s also not available with a stainless barrel anymore. Looks like all their 243 offerings are now one and eight Twist. That’s the reason I ordered the Stoner at the time because Of the slower twist. Bearcreek didn’t have them in stock because they were re-branding them for midway USA at the time. Then months later after I bought mine Bearcreek started selling them on their website for 120 bucks cheaper. Yeah the one that you have is a heavy log I have the same one it weighs about 8 1/2 pounds according to their website. My guess is it weighs more. 20 inch version weighs half of that according to their posted website specs. I still didn’t place my order today because Bearcreek never called me back. I did get some answers from one of the employees that posted a 243 video on YouTube. When I ask questions on there they respond pretty quick. I was told the side charging receiver weighs more so I’ll probably be ordering the rear charging model either tonight or tomorrow morning. I’ll be pretty excited if it really weighs 4 3/4 pounds versus the 8 1/2 pound upper I have now... Basically half the weight.


I figure for another 300 bucks it’s worth the gamble for a 20 inch light weight 243 upper. If it doesn’t shoot white projectiles I’ll just sell or trade it off. I’m sure it will shoot great using light or heavy projectiles with the right hand loads.
 
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