AR wives tales

[budlight]

A slightly different question. My AR10 Armalite Target action takes a lot of effort to charge the first round. It is lubed well and throws the spent rounds at 2-3 o'clock. I have to place the rifle butt on my knee or against my belly and it takes a lot of force to pull the bolt back. It cannot be charged by holding the rifle in one hand and pulling the charge handle back with the other hand. That action will cause my rifle to swing wildly. I see a lot of videos of guys seemingly easily pulling an AR15 bolt back, not mine. Is this amount of force normal for a 308 AR10? If not, what is required to fix this to make charging less effort.

I just pulled my 308 out. With a fully charged 20 round mag and it's just a two finger easy charging. It seems to me that when I built this thing out of parts that I went to a lighter rifle length spring. It's the buffer weight spring that is resistance to charging. 2-3 means that you are over gassed. I pulled the rear breakdown pin and I can push the buffer weight down with one finger.

 

[JustMe2]

AR10's seem to require a bit more "break-in" time than 15's, but I would suspect you have excessive pressure on your carrier from a full magazine. If you strip a couple rounds out of the mag, does it still do that? One thing most people don't understand is that the bolt is not cycled by the gas impulse through the gas tube/piston. That impulse only unlocks the bolt, which is now being driven back by the pressure of the gasses still within the barrel. That pressure obviously dissipates very quickly as the action opens and the bullet exits, but is a very strong initial impulse.

Yes, it is still very heavy even with the magazine removed. It's a real bear to pull back and I go to the gym lifting weights regularly. Was wondering if the spring is too heavy or that's how all AR10s operate. The AR15s I've used takes 1/4 the effort or less. This thing takes probably 20 pounds or more to pull back.

 

[MSURunner]

Yes, it is still very heavy even with the magazine removed. It's a real bear to pull back and I go to the gym lifting weights regularly. Was wondering if the spring is too heavy or that's how all AR10s operate. The AR15s I've used takes 1/4 the effort or less. This thing takes probably 20 pounds or more to pull back.

Any chance you've got a rifle length spring in a carbine buffer?

 

[JustMe2]

I just pulled my 308 out. With a fully charged 20 round mag and it's just a two finger easy charging. It seems to me that when I built this thing out of parts that I went to a lighter rifle length spring. It's the buffer weight spring that is resistance to charging. 2-3 means that you are over gassed. I pulled the rear breakdown pin and I can push the buffer weight down with one finger.

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I can push the buffer spring in with one finger, but it really flattens the end of my finger and is not easy/comfortable. What weight spring would you recommend? I changed the factory M-16 butt to a Magpul PRS Gen I and I added an extended charge handle. I can only pull one side of the charge handle since my scope is too low for two fingers to fit on both sides. I have an adjustible gas block. What clock position should it be throwing the brass? I always thought 3 o'clock was correct. Will changing the blowback make pulling the charge handle easier? Doesn't seem like that would affect it.

 

[JustMe2]

Any chance you've got a rifle length spring in a carbine buffer?

How can I tell? I changed the factory M-16 style butt to a Magpul PRS Gen I and used the same factory buffer spring.

 

[MSURunner]

Take the spring out and measure it for length. If it is >=11.75 it's a Rifle length spring. It sounds like you have a rifle buffer tube (screws in with a flat on the back to torque and completely round), so the next thing I would say is make sure there aren't any spacers on the inside of the tube. Is it difficult to pull back through the entire stroke or only initially? If it is easier to pull back after you've started it, then you may have some issues with your bolt unlocking (either too tight of tolerances, machining burrs, cam pin issue, or just plain dirty). As for changing the spring to a softer spring, yes, it will change ejection angle because the brass will be pulled back quicker. Ideal for most guns is probably in the 330-430 window, but if you're going to err one way or the other, I would choose over gassed to under gassed (which means I'd take a 230-330 if that was necessary). There are a lot of variables (barrel length, gas system length, gas block setup, BCG weight, buffer weight, buffer spring) to this that probably could be a thread in and of itself. Without knowing those, we're just guessing at your problem.

 

[JustMe2]

Take the spring out and measure it for length. If it is >=11.75 it's a Rifle length spring. It sounds like you have a rifle buffer tube (screws in with a flat on the back to torque and completely round), so the next thing I would say is make sure there aren't any spacers on the inside of the tube. Is it difficult to pull back through the entire stroke or only initially? If it is easier to pull back after you've started it, then you may have some issues with your bolt unlocking (either too tight of tolerances, machining burrs, cam pin issue, or just plain dirty). As for changing the spring to a softer spring, yes, it will change ejection angle because the brass will be pulled back quicker. Ideal for most guns is probably in the 330-430 window, but if you're going to err one way or the other, I would choose over gassed to under gassed (which means I'd take a 230-330 if that was necessary). There are a lot of variables (barrel length, gas system length, gas block setup, BCG weight, buffer weight, buffer spring) to this that probably could be a thread in and of itself. Without knowing those, we're just guessing at your problem.

Thank you very much. That was helpful. I'll have to check those things since it's been a long time since I've removed the spring. It seems like it takes the same effort for the entire pull, but once it starts moving I have momentum helping me. Everything is very clean and well lubricated with both "slide grease" and gun oil.

 

[Jasbo]

Thank you very much. That was helpful. I'll have to check those things since it's been a long time since I've removed the spring. It seems like it takes the same effort for the entire pull, but once it starts moving I have momentum helping me. Everything is very clean and well lubricated with both "slide grease" and gun oil.

You may consider an experiment of removing the scope so that you can use two fingers to pull the charging handle? This may answer; is pulling on only one side adding substantial friction?

 

[JustMe2]

You may consider an experiment of removing the scope so that you can use two fingers to pull the charging handle? This may answer; is pulling on only one side adding substantial friction?

Thanks. I tried that and it's a slight easier, but still very heavy compared to an AR15.

 

[HRM Johnny]

Lots of misinformation out there about felt recoil and the ejection system. So I went looking and came across this well written post. I have learned over time from my own experimentation and seeing what the pro's are doing. I've been blessed with enough resources to buy barrels and parts and modify them and if it doesn't work out, I throw them away. Life is about learning and not just trusted some gun shop owner that knows it all when you tell him that his 20 inch 7 twist throws every 55 or 62 grain bullet sideways through the paper at even 50 yards. Or an expensive FN ar10 that can only shoot "Service Rifle ammo" I also don't like using Adjustable gas blocks! when you can build a perfectly functional micro blocked rifle. I have two piston 15's with adjustable gas blocks. because of my rifle length and .072 gas ported SS barrel it's basically wide open to cycle right. Out shooting away 100's of miles from home and the adjustment came apart and quit firing. Luckily I always bring two or more rifles. Lesson learned from many years ago deer hunting when my buddy climbed into the pickup bed and upon coming out kick my rifle off the tail gate and internally broke my scope when it landed on a rocky two track road. The cross hairs were like 10 feet left and 8 feet high, so my hunt was done with a 800 mile round trip.

I machine dimples in my gas gun barrels, so the set screws don't allow the micro blocks forward over time and use high temp Permatex red inside the block to seal all gas from escaping between the block and the barrel.

On to the good read!

The Physics of AR-15 Recoil Reduction - AR15.COM

Firearm Discussion and Resources from AR-15, AK-47, Handguns and more! Buy, Sell, and Trade your Firearms and Gear.

www.ar15.com

Excellent information. But, let us not disparage wives tales. A lot of married men on this formum are quite fond of wives tails. … …

 

[budlight]

What clock position should it be throwing the brass? I always thought 3 o'clock was correct.

I've actually cut off some the length of the buffer tube springs then stretched them out to the original length. Instead of waiting for some shipment to arrive in a week or two. You might need a couple of trims to get it right.

AR-15 Ejection Patterns - Wideners Shooting, Hunting & Gun Blog

Learn about AR-15 ejection patterns in this helpful article, we'll show you how to figure out where your casings should be going.

www.wideners.com

 

[budlight]

Yes, it is still very heavy even with the magazine removed. It's a real bear to pull back and I go to the gym lifting weights regularly. Was wondering if the spring is too heavy or that's how all AR10s operate. The AR15s I've used takes 1/4 the effort or less. This thing takes probably 20 pounds or more to pull back.

Well did you get the spring cut shorter or buy a new one?

 

[JustMe2]

Well did you get the spring cut shorter or buy a new one?

Not yet. Thanks for asking. I was planning to wait until after New Years to call Magpul about a shorter spring. It's hunting season here in Florida with the rut just around the corner. The rifle season doesn't start here until 16 Dec. Went deer hunting today, but didn't see anything.

 

[ntsqd]

I haven't used many of them, but I've become a fan of Sprinco springs. Was able to take a .40 S&W PCC from poorly/barely functioning with the recommended spring for that application to functioning well with almost anything in commercial ammo.