[zenmtnman]

Hey all,
Just got back from a marathon day at the range with a friend, and brought along my new 6.8 build to try out. Since my SSA ammo order somehow routed through Chicago, rather than to here in Colorado, I loaded up 100 rounds of 110g Hornday V-max polymer tips with 24 grains of Benchmark powder in my factory fresh SSA brass the night before.
I was all excited to try out the new upper I bought (RRA mid 6.8), put the first C-products 25 round mag in and locked and loaded the first round. Bang...sweet. Bang...sweet. Click - ???
Round didn't feed. Pull back the charging handle. Chamber round. Bang...sweet. Click. D*mn.
Needless to say, my beautiful new RRA mid became a bolt action rifle today. I couldn't get it to reliably feed more than two rounds in a row, and I had to have the range officer come over 4 times to tap back the charging handle with a rubber mallet to clear an unfired round that was stuck in the chamber with the bolt not all the way closed.
Alright...here's what we all sussed out as potential reasons why this is happening.
1. I've got a heavy tungsten buffer in there, which I thought the heavier powder charge of the 6.8 would be able to push back. Maybe that's not the case. Maybe swap for a carbine buffer?
2. Something with the mag perhaps? I had three mags there, but all had the issue. The bolt would sometimes cycle and lock, but not pick up a round.
3. My handloads - maybe I didn't chamfer the case mouth enough and the little lip at the crimp was hanging up somewhere in the chamber. And for Failure to Feed, maybe that ridge/lip was catching on the mag lip and that slowed the bolt enough to not feed all the way.
4. Its just band new and needs more lube - all the tolerances are tight, and it needs some time to break in and run smooth.
The good news is I was able to get the front sight post adjusted so I was hitting center height at 50, even if I was a bit left with my first outing with iron sights. I was also able to ground 5 shots in 4 inches at 100 (again first time with an AR and irons). I love how soft this platform is, of course, I was also shooting my friends 300 win mag, and my 30-06 loaded hot with 180 grain bullets.
So pros on this board - what do you think it is? My intial reaction is to swap buffers and maybe open the lips on the mag a bit to see if that fixes the issue. I'm also going to see if the factory ammo has the feeding issue/jamming issue, as that would point to the hand loads.
Gimme your theories, your thoughts, and your ideas. I'm all ears.
If I've left out any pertinent info, please ask, as its late and i should have been in bed an hour ago. =)
Thanks in advance.

 

[paulosantos]

24 Gr.. of benchmark and the 110 Gr. bullets is WAY too weak. That is probably the cause of your short stroking issues. The recommended max is 29 gr. I would load up some with 28, 28.5 and 29 Gr. of benchmark and try again. Also, start with the lightest buffer you have.

 

[pira114]

3. My handloads - maybe I didn't chamfer the case mouth enough and the little lip at the crimp was hanging up somewhere in the chamber. And for Failure to Feed, maybe that ridge/lip was catching on the mag lip and that slowed the bolt enough to not feed all the way.

This couldn't possibly be the case if your main problem is rounds not stripping from the mag.

Have to agree with Paulo about the buffer. Don't know anything about the loads, but I would defer to him anyway.

 

[marinesg1012]

Start with the carbine buffer..

use factory ammo to test... I dont know much about and loads but if Paul says its way to light then you should bump it up...

did you hand cycle your action 500-1K times to get her broken in?

 

[joshuades]

Hey all,
Just got back from a marathon day at the range with a friend, and brought along my new 6.8 build to try out. Since my SSA ammo order somehow routed through Chicago, rather than to here in Colorado, I loaded up 100 rounds of 110g Hornday V-max polymer tips with 24 grains of Benchmark powder in my factory fresh SSA brass the night before.
I was all excited to try out the new upper I bought (RRA mid 6.8), put the first C-products 25 round mag in and locked and loaded the first round. Bang...sweet. Bang...sweet. Click - ???
Round didn't feed. Pull back the charging handle. Chamber round. Bang...sweet. Click. D*mn.
Needless to say, my beautiful new RRA mid became a bolt action rifle today. I couldn't get it to reliably feed more than two rounds in a row, and I had to have the range officer come over 4 times to tap back the charging handle with a rubber mallet to clear an unfired round that was stuck in the chamber with the bolt not all the way closed.
Alright...here's what we all sussed out as potential reasons why this is happening.
1. I've got a heavy tungsten buffer in there, which I thought the heavier powder charge of the 6.8 would be able to push back. Maybe that's not the case. Maybe swap for a carbine buffer?
2. Something with the mag perhaps? I had three mags there, but all had the issue. The bolt would sometimes cycle and lock, but not pick up a round.
3. My handloads - maybe I didn't chamfer the case mouth enough and the little lip at the crimp was hanging up somewhere in the chamber. And for Failure to Feed, maybe that ridge/lip was catching on the mag lip and that slowed the bolt enough to not feed all the way.
4. Its just band new and needs more lube - all the tolerances are tight, and it needs some time to break in and run smooth.
The good news is I was able to get the front sight post adjusted so I was hitting center height at 50, even if I was a bit left with my first outing with iron sights. I was also able to ground 5 shots in 4 inches at 100 (again first time with an AR and irons). I love how soft this platform is, of course, I was also shooting my friends 300 win mag, and my 30-06 loaded hot with 180 grain bullets.
So pros on this board - what do you think it is? My intial reaction is to swap buffers and maybe open the lips on the mag a bit to see if that fixes the issue. I'm also going to see if the factory ammo has the feeding issue/jamming issue, as that would point to the hand loads.
Gimme your theories, your thoughts, and your ideas. I'm all ears.
If I've left out any pertinent info, please ask, as its late and i should have been in bed an hour ago. =)
Thanks in advance.

What buffer do you have precisely? I had bought an MGI buffer with the same idea in mind and eventually had to take out the weights and replace the springs inside with lighter ones. At first it was just too heavy to cycle and after I lightened the buffer I found the springs were oo heavy to be compressed and wouldn't lock back. My first move in your case would be to swap the buffer for a standard buffer.

 

[zenmtnman]

Thanks for all the replies so far.
The loads are a bit light as they were the first 6.8 I've loaded. I went 10% below the low range, but wasn't expecting that to cause cycling problems. Guess that's the newbie AR owner in me...never have that problem with my bolt guns! (lol).
The buffer is the extra heavy tungsten carbine buffer...picked it up from Fulton for this build. Guess I need to give it a work out with hotter loads.
The short stroking of the action would definitely cause all the problems I had.
The factory ammo should be showing up this week, as well as the A1 buttstock assembly I've ordered for another build. That set up will have the stock ar rifle buffer with it, so I'll throw the 6.8 upper on that lower as well to see if that fixes the problem. I'll also load a few 28 gr loads and take them out back to see if they'll cycle.
Keep the suggestions coming, and thanks a lot.
Love this forum!

 

[QuicksilverJPR]

Thanks for all the replies so far.
The loads are a bit light as they were the first 6.8 I've loaded. I went 10% below the low range, but wasn't expecting that to cause cycling problems. Guess that's the newbie AR owner in me...never have that problem with my bolt guns! (lol).
The buffer is the extra heavy tungsten carbine buffer...picked it up from Fulton for this build. Guess I need to give it a work out with hotter loads.
The short stroking of the action would definitely cause all the problems I had.
The factory ammo should be showing up this week, as well as the A1 buttstock assembly I've ordered for another build. That set up will have the stock ar rifle buffer with it, so I'll throw the 6.8 upper on that lower as well to see if that fixes the problem. I'll also load a few 28 gr loads and take them out back to see if they'll cycle.
Keep the suggestions coming, and thanks a lot.
Love this forum!

Too heavy a buffer, IMHO. I wouldn't use more than the standard H buffer with the 6.8...

 

[zenmtnman]

Update #2.
The A1 stock came in today, so once I put that together I tried the 24 grain cartridges with that lower to see if it would strip/feed reliably. It would cycle and pick up the next round, but wouldn't have enough force to put that next round into the chamber and lock.
Alright, next step...had some time on my hands (as I work from home) and put together 4 rounds of 110 grain v-max with 28 grains of powder, as suggested.
Tried it with the A1 lower, cycled great! (Yes!)
Tried it with the tungsten buffer lower...Bang, Bang! YES!!!!
So it looks as though my problem is solved for the time being. I've got a standard CAR buffer on the way for the CTR lower, and until then I'll use the A1 lower for my 6.8 shooting. I'm also going to take apart the 24 grain rounds (about 30 left) and re-mix them to a hotter load, since I'm guessing the CAR buffer will cycle about the same as the rifle length buffer with the 24 grain loads.
Thanks again everyone for your help!

 

[Test_User]

You are going down the right path now.