AR 15 - Switched to PRS bolt barely goes forward

[Tango24]

I just recently switched from a collapsible stock to a PRS. I changed the receiver extension to full length and added the Brownells stock completion kit (rifle spring and buffer).

I haven't even fired it yet and already noticed an issue. The bolt carrier is moving forward too slow and doesn't always go all the way into battery. When I move it by hand I don't feel what I would call excessive resistance or any rough spots.

Any thoughts on troubleshooting this? Thanks!

 

[Ballista One]

Lube it copiously first and then again. Cash money says this solves the problem...

Are you letting the bolt group "fly" using the bolt release or charging it by hand?

 

[bp7178]

Measure the spring and make sure its actually a rifle spring.

 

[Tango24]

I have charged it both ways, using the bolt release and by hand.

How would I measure the spring? Once I've done that, what value tells me it's a rifle vs carbine spring?

 

[lennyo3034]

Compare it's length to the carbine spring you took out. Or just report the measurement here and we'll help figure it out. The other possibility is the Bolt carrier binding on something, perhaps the buffer retainer? Unlikely but I've seen it happen.

 

[Laseredge]

39 coils for an AR15 Carbine 11.25" relaxed
44 coils for an AR15 Rifle 12.75" relaxed

http://heavybuffers.com/reference.html

 

[Tango24]

Sorry, by measurement I thought the issue was strength of the spring. I had no idea how I would measure that.

The spring is 42 coils and 12 1/8" long. The carbine spring it replaced is considerably shorter but I didn't measure it.

 

[maggitas]

Tango,

did you purchase the A1 or A2 completion Kit? Is the spring excessively noisy when the charging handle is pulled?

 

[Tango24]

I bought the A2 version. My understanding is the only difference between them is the A2 includes a spacer. The receiver extension is the same. From that I would guess the spring is too, but I don't know that for certain.

There is no unusual noise from the spring when I pull the charging handle.

 

[maggitas]

Tango,

The reason I ask is that I had a AR and had an issue with the spring binding in the tube. If it all looks good you may consider asking Brownells if they can upgrade your recoil spring to a Wolff xtra power spring.

 

[BC83]

I would do this...

Take your lower and plunge your buffer down and up and make sure that the buffer is traveling smooth..

Then take your upper and leave you CH and BCG in the forward locked position and then grab the back of your BCG and move it in and out of battery, making sure the BCG is not binding in your receiver, also make sure that your gas tube is not bent binding up the Gas Key

The only other thing i can think of is to check your Buffer Retainer, make sure its not to high (out of spec) grinding the bottom of your BCG

 

[Woj8541]

Just to get this straight. So, when you lock the bolt to the rear and send it home by releasing the bolt catch the BCG doesn't go into battery? How far does it appear to be out of battery at the completion of it's travel?
Is it consistent and repeatable or does it just do it sometimes?
Can you get the BCG/Bolt to go into battery with your hand without the lower attached?

My guess is that your spring is drastically too soft but I find that hard to believe if it came from Brownells.

If all else fails, the best AR spring I've used is the Tubb Flat Wire. Best $32 upgrade for an AR, 5.56 or 7.62.


Sent from my iPhone using Tapatalk

 

[bobke]

When installing new buffer tube, did you depress buffer retainer fully to let tube seat fully home? If you look at the tip of the plunger, has any metal been sheared off of the tip of buffer retainer plug from cycling action? If so, pull tube and reinstall, being certain to depress retainer plunger to let shoulder of tube seat fully to lower and over shoulder of retainer plug.

 

[Travis S]

Silly question, but did you install the correct buffer as well? If yes, check for hang ups along travel. Lube it up good, let it fly several times.

 

[Woj8541]

AR 15 - Switched to PRS bolt barely goes forward

A word of caution when lubing buffer springs. If you absolutely feel as though you've gotta lube it make sure you do it very sparingly with a low viscosity substance. In lower temperature operations higher viscosity greases will cause malfunctions as a result of slower BCG velocities. (I know a shop here that was building guns and putting tons of bearing grease on the springs to "quiet them down". That didn't play out so well when the weather got colder and they couldn't figure out why customers were coming into the shop saying their guns were malfunctioning.)

 

[maggitas]

Well you replaced three parts. Buffer tube, buffer spring, and Buffer. The problem lies with one of them you would think. If you have access to other parts substitute each part until you find the culprit.

 

[Woj8541]

AR 15 - Switched to PRS bolt barely goes forward

Indeed.

 

[Tango24]

Since I moved from a carbine to a rifle stock I can't replace only one component at a time.

I still don't have the solution but I have isolated the problem. The buffer and spring are moving freely in the receiver extension. The bolt carrier also moves freely in the extension. However, the carrier slides into the upper freely only about a third of the way and then it binds up. I cannot tell whether the carrier key is lined up appropriately with the gas tube. Any thoughts on this?

 

[bp7178]

Is the gas tube upside down?

Is the FSB or gas block loose?

Is the barrel nut loose?

Does the gas tube look centered in the upper?

Can you take any pics? Its hard to diagnose things just off of your typed messages.

 

[Andy T]

This usually indicates that the gas tube became bent. You can try to carefully "unbend". The carrier, without bolt in it, is supposed to smoothly fall down all the way forward with the gas tube inside the gas key.

 

[bp7178]

Is the gas tube obstructed at all; is there anything stuck inside of it?

 

[BigBlue&Goldie]

Do you have a forward assist upper? If so, check out the forward assist pawl to see if it's damaged. I saw a well known shooter's rifle lock up like a vault after a forward assist broke.