AR10 failure to feed.

[whatsupdoc]

First is it an AR10 or is it a DPMS configuration rifle?
Take the rife and put the boltcarrier into battery, next install an empty magazine.

Pull the charging handle all the way to the rear, release the charging handle.
Does the bolt catch engage and hold the boltcarrier???

If it does hold it open where does the catch engage?

If the rifle is not stripping a round out of the magazine when you charge the rifle its
either a magazine issue or the boltcarrier is not reaching its full travel.

 

[whatsupdoc]

One more thing with the bolt carrier pulled all the way to the rear and the bolt catch
raised by the magazine (or manually) you should have at least .125 clearance between the two.

 

[mac86951]

This was the one test I wish I would've done while at the range yesterday. would be very telling.

Rifle Should do so without pushing the bolt catch, maybe that's step 2?

Step 3 then is feed one from the mag and see if bolt locks back.

 

[asquared19]

Thank you again for all who had input. The unit is built with an Aero Enhanced complete upper. 22" barrel in 6.5CM. https://aeroprecisionusa.com/m5e1-65-cm-22in-mid-ss-complete-upper.html

Stock is a Magpul PRS Gen 3. https://www.primaryarms.com/magpul-prs-gen-3-precision-rifle-stock-black

Buffer Tube kit is a Tactical Works PRS completion kit. https://www.tacticalworks.com/Magpul-PRS-Completion-Kit-AR10-.308-PRS308.html

CH is the Radian Raptor Ambi - https://www.midwayusa.com/product/1019310486?pid=289399

Today we lubed this thing adequately. Neighbor took the BCG apart and helped me do a proper lube clean. Again, keep in mind issues presented day 1 on first firings, and I only have 30 rounds down range with it total.

We then took the buffer and buffer spring out and gave them a lube. What I noticed is that it took a lot of force to pull back on the CH. If I was deliberate about ensuring the CH went full stroke, I was able to strip a round every time, with the magpul pmags.

If I casually pull the last round of the chamber with an empty mag, the BCG cycles forward again. If I really yank on it, it locks in the open position. I could also pull back casually and manually lock it open, and the BCG would be forward. If I again, deliberately, pull back on the CH and lock it, then it locks back with the BCG in the full rear position. Please see attached photos. One photo is showing the Raptor pulled back all the way. as can be seen, clearance to the cheek weld on the PRS stock is a fraction of an inch. The second photo is the chamber with the BCG locked. Note that this is locked with the BCG a full 3/4" or so into the chamber. this is the issue I reference above where I can lock it without the BCG being in the full rear position. If I really pull back, I can get it to lock in the full rearward position.

I took a video too, showing how if it was fully locked in the rear position, it would properly strip a round.

All of this being said, I'm suspecting it's something in the Tactical Works buffer tube/spring setup. too stiff a spring?

Any thoughts?

 

[mac86951]

Thank you again for all who had input. The unit is built with an Aero Enhanced complete upper. 22" barrel in 6.5CM. https://aeroprecisionusa.com/m5e1-65-cm-22in-mid-ss-complete-upper.html

Stock is a Magpul PRS Gen 3. https://www.primaryarms.com/magpul-prs-gen-3-precision-rifle-stock-black

Buffer Tube kit is a Tactical Works PRS completion kit. https://www.tacticalworks.com/Magpul-PRS-Completion-Kit-AR10-.308-PRS308.html

CH is the Radian Raptor Ambi - https://www.midwayusa.com/product/1019310486?pid=289399

Today we lubed this thing adequately. Neighbor took the BCG apart and helped me do a proper lube clean. Again, keep in mind issues presented day 1 on first firings, and I only have 30 rounds down range with it total.

We then took the buffer and buffer spring out and gave them a lube. What I noticed is that it took a lot of force to pull back on the CH. If I was deliberate about ensuring the CH went full stroke, I was able to strip a round every time, with the magpul pmags.

If I casually pull the last round of the chamber with an empty mag, the BCG cycles forward again. If I really yank on it, it locks in the open position. I could also pull back casually and manually lock it open, and the BCG would be forward. If I again, deliberately, pull back on the CH and lock it, then it locks back with the BCG in the full rear position. Please see attached photos. One photo is showing the Raptor pulled back all the way. as can be seen, clearance to the cheek weld on the PRS stock is a fraction of an inch. The second photo is the chamber with the BCG locked. Note that this is locked with the BCG a full 3/4" or so into the chamber. this is the issue I reference above where I can lock it without the BCG being in the full rear position. If I really pull back, I can get it to lock in the full rearward position.

I took a video too, showing how if it was fully locked in the rear position, it would properly strip a round.

All of this being said, I'm suspecting it's something in the Tactical Works buffer tube/spring setup. too stiff a spring?

Any thoughts?

That's the bolt catch hooking the forward part of BCG, instead of bolt face.

Sounds to me that somewhere in your build, apples and oranges were mixed. Welcome to AR-10, which in of itself is completely erroneous to say and is half the problem.

AR-10 parts are generally NOT compatible with DPMS LR-308 / KA SR-25 pattern stuff. Aero Prec. Is DPMS pattern.

Ok, that stated, i have three suggestions.
Two possibilities are bolt carrier interface questions. All based on how the bolt carrier interfaces with parts in the lower. Those parts can be:. Trigger hammer, bolt catch, buffer tube, buffer spring retaining pin, and actual lower receiver buffer threads / casting portion of receiver.

Bolt carrier commonly drags on the bolt catch tab. What's the lower you're using, and what parts kit? I'm guessing you've got the bolt carrier dragging on the top of the bolt catch (I've seen that one s few times). Both parts are hardened, so it'll be light wear marks. Question, when bolt is closed, if you press bottom of bolt catch is there any play in the bolt catch, or is it tight?

Bolt carrier can also be dragging on the buffer spring retention pin. Look for a single line worn under the bolt carrier. Might also look like trigger hammer as it wears in.

Bolt carrier can be misaligned with buffer tube.

My advice, remove buffer and buffer spring and check bolt / charging handle clearances. It should slide freely thru the whole cycle.

If above is True then, buffer and buffer spring are your troubles.

I'm always wary when I hear about an AR-10 that doesn't work and a list of mix matched parts from 3rd party suppliers. I'm guessing the buffer /spring is your issue by how you describe the force needed to fully open the bolt. We've been there, we've built them, but large formats are not the small formats and one must be picky. Let's get your rifle working, then we can help you get it back to where you want it. Keep us posted. If you can't cycle it by hand then that's where we start!

Might be worth a few dummy rounds (sized case, no powder, no primer, only bullet).

-Mac

 

[asquared19]

Here is the LPK. https://www.aeroprecisionusa.com/m5-308-lower-parts-kit
PM sent too. I have some dummy rounds to play with, and can try your suggested ideas tonight or tomorrow at worst.

 

[miningshawn]

It is the magazine. Switch to a steel magazine and enjoy life.

I stand corrected, mostly.
I agree with everything mac posted. The easy things to check are the bolt catch dragging on the bcg as it cycles and the gas block alignment. Buffer springs and buffer weight in AR10's can be tricky.
If it were me...
One of the things I see is that it is 6.5 and not .308 so there is less recoil energy to cycle the bolt. I would try to get a better alignment first, and order an adjustable gas block second.
I would also pick up a buffer with a lighter weight, there are a few adjustable ones out there that won't break the bank.
But..... I would still use steel or aluminum magazines

Edit: also, it's a new build. Try hosing out the gas tube with brake cleaner, this will also clean the gas block. There may be crud or chips left from manufacturing. Don't forget to run some oiled patches down the barrel immediately after to prevent flash rusting.

 

[YEW PLUCKER]

I'm no expert, but it sounds to me like your rifle might be under gassed. Why don't you try an adjustable gas block?

 

[asquared19]

Thanks again everyone for the input. As mentioned in the OP, after the original shot and F2 feed, I figured under gassing, but then ran into the same issue manually cycling. I did a lot of cycling last night with some dummy rounds and found that if I was very intentional about cycling it all the way back, it stripped a round every time and then locked in the open position with an empty mag. Again, it just seemed like it took much more exertion then should be required, and this aligns with the fact that it happens under fire. Doing some more testing with the dummy rounds, and by pulling the buffer and spring, and will see what results I come to. I do want to say that I've been communicating with Mac, and he's been incredibly patient, helpful, and thorough in this process. I'm confident we will get to the bottom of it.

 

[DiffEQ]

If the picture of it "locked back" is what you are calling that, eek.
Please do the following:

• Measure your buffer tube. Post that info.
• Measure and weigh the buffer, post that info.
• Measure the spring length. Post that info.
• Measure the BCG OAL with the bolt in the extended position, Post that info.

I have ordered "AR10" buffers, buffer tubes and springs and received AR15 ones instead. To the uninitiated, they look the same.
AR10 springs are generally shorter than AR15 ones, but there's lots of conflicting info around on that.
Here's a good resource at 308ar.com .

Make your life easier.
If you make it to Portland much and you're still struggling, we can meet and I'd be glad to go over your build with you. If anything is needed, we can head over to Oregon Rifle Works in Tigard. They will have the parts (and knowledge) to set your build right, and they will also check your headspace for free.

 

[asquared19]

If the picture of it "locked back" is what you are calling that, eek.
Please do the following:

• Measure your buffer tube. Post that info.
• Measure and weigh the buffer, post that info.
• Measure the spring length. Post that info.
• Measure the BCG OAL with the bolt in the extended position, Post that info.

I have ordered "AR10" buffers, buffer tubes and springs and received AR15 ones instead. To the uninitiated, they look the same.
AR10 springs are generally shorter than AR15 ones, but there's lots of conflicting info around on that.
Here's a good resource at 308ar.com .

Make your life easier.
If you make it to Portland much and you're still struggling, we can meet and I'd be glad to go over your build with you. If anything is needed, we can head over to Oregon Rifle Works in Tigard. They will have the parts (and knowledge) to set your build right, and they will also check your headspace for free.

thanks for the input and offer. Very much appreciated. The picture with the BCG partially in the chamber isn't it fully locked back. As Mac corretly stated, it was catching the front of the BCG not the bolt face. If I really worked it back, I could get it to lock in the full rearward position, as well as get it to strip rounds and automatically lock open with an empty mag. Mac has been guiding me via PM as well, and it seems there's a little resistance in the buffer tube. He had me pull the buffer and spring and draw back the BCG and let go, with the muzzle pointed down. The BCG wouldn't just freely drop back. I had to tap the stock a little for it to start coming down, then eventually it would finally drop.