[sredish]

Got my 6.8 built back in November but have never gotten around to shooting it.... work, travel, family, etc...

Well, tonight I did. I put 60 rounds through it for a prelim deal. About every 3 to 5 rounds, it would fail to feed; bolt would close with no round or it would half feed and jam, literally every 3 to 5 rounds, but mostly not feed at all. I would pull the bolt back and let go, feeding a round in and it would shoot another 4 or 5. I had about 6 rounds total that fed into the chamber and was struck by the pin but didnt' fire. there was an impression but not as dramatic as the fired rounds, but looked enough to fire to me. Hammer would fall and go click, I'd pull the bolt expecting there not to be a round in there (mis-feed) and it'd spit a round out; a round that failed to fire despite being struck by the pin. I think I had one round that actually jammed altogether and was dented by the bolt closing.

When it fired, it fired good and strong, and I loved it, especially when comparing back to back to my 5.56. I just want it to fire right. Here's some of the specs:

Spikes Upper and Lower
Spikes Pistol Buffer Tube assy. (I'm assuming std. 5.56 buffer spring)
Noveske 14.5" Barrel (came with carbine gas assy)
Young National Match chrome carrier
6.8 bolt that was supplied with the Noveske barrel

Ammo was 6.8 TAP, loaded into Barrett 6.8 mags probably 6 weeks ago.

Seems like it's not seating properly. Having only 60 rounds, I might need to just put some more mags through it and try to break it in, smooth it out some....

any thoughts / questions?

edit: I can remember (shooting with muffs on, of course) hearing it shoot and the bolt opening and closing. Seemed to be a slower process than on the 5.56.... so I'm wondering if the spring is too heavy, causing a slow ejection and occasional lack of feed and difficult seating or something. I'm trying to remember how the brass was ejecting and I'm thinking it was like 4 or 5 o clock; I'll check the upper to see if there's any brass contact.

 

[sredish]

Upon inspection, there are brass marks on the deflector.... can't remember if that means I need lighter or heavier....

Is this what is called 'short stroking'... if so, can someone recommend a specific spring/buffer to use?

 

[paulosantos]

Your buffer should be the regular carbine buffer. Look on the face of the buffer. There shouldn't be any letters on it. If it has an "H" or "H2", it means you have a heavy buffer. It shounds like it is short stroking. Before you go back out to the range, lube it up and hand cycle it a couple of hundred times more. When you go to the range, load up one round in the magazine. load it up and shoot it. The bolt should stay open. Do that a couple of times and see what happens. Then load up a couple at a time and shoot them off and see if the bolt stays open on the last round.

 

[sredish]

Your buffer should be the regular carbine buffer. Look on the face of the buffer. There shouldn't be any letters on it. If it has an "H" or "H2", it means you have a heavy buffer. It shounds like it is short stroking. Before you go back out to the range, lube it up and hand cycle it a couple of hundred times more. When you go to the range, load up one round in the magazine. load it up and shoot it. The bolt should stay open. Do that a couple of times and see what happens. Then load up a couple at a time and shoot them off and see if the bolt stays open on the last round.

cool, i'll try that. speaking of what your talking about, both times the mag emptied, it failed to stay open properly. the first time, the follower kept it from closing completely but the catch did not stop it; the second time, it closed most of the way.

i'll try that tomorrow a little. if it is short stroking, would I start off with a lighter spring? i'll get some lube on it and cycle it some more, I probably only have a couple hundred hand cycles...

 

[rcrandall]

Short stroking. Hornady is a little on the light side and the gun is probably still tight.

 

[sredish]

It has the std. carbine buffer and spring; so where do I find a spring that will work better for the gun and load or do I need to replace the buffer as well? I will be lubing it some and do a bunch more hand cycles with it... I'm sure it'll smooth out some more if past experience repeats itself but I'd still like to know a little more about the buffer spring options.

 

[paulosantos]

It has the std. carbine buffer and spring; so where do I find a spring that will work better for the gun and load or do I need to replace the buffer as well? I will be lubing it some and do a bunch more hand cycles with it... I'm sure it'll smooth out some more if past experience repeats itself but I'd still like to know a little more about the buffer spring options.

You already have the lightest buffer and springs on it. Try some SSA ammo and see if it still short strokes. As rcrandall indicated, Hornady ammo is kind of weak.

 

[sredish]

Cool. I went ahead and took the initiative to order two of the SSS springs, one for the 6.8 and one for my Colt. How does this spring compare with the carbine? I might leave this carbine one in there until it's broken in and performing properly, then swap and see how it does. SSA amoo on the way.

 

[paulosantos]

Cool. I went ahead and took the initiative to order two of the SSS springs, one for the 6.8 and one for my Colt. How does this spring compare with the carbine? I might leave this carbine one in there until it's broken in and performing properly, then swap and see how it does. SSA amoo on the way.

It works great. If you read the instructions, it specifically tells you that you are supposed to cut the springs. When you get them, they are long as hell. I never had a problem with my AR's short stroking with them, so I left mine alone, but if you do have some problems, cut a couple of coils at a time.

 

[Strawdawg]

Before doing anything, I would shoot some hotter ammo and see if that cures the problem. Lightly loaded ammo and a new gun may be all that is wrong.

 

[sredish]

thanks. yea, that's exactly what I'm going to do for now. I'm going to leave the spring in there for now, cycle it some more and try to shoot it tomorrow after cycling it. I won't swap the spring until it's broken in and shooting right with the current one. the ammo I ordered is the SSA 90gr Speer TNT round; that looks to be a great home defense round so I'll try that one out.

 

[BLACK LION]

I put my sss spring right on my rifle buffer... no trimming at all... works like a dream...



maybe you can opt for a carbine length buffer tube and heavy carbine buffer in conjunction with the sss spring.... maybe that pistol tube and buffer is too light...

 

[sredish]

Discovered something; what I believed was in the rifle was a std. buffer but upon inspection showed that it was an H buffer. Might not be a lot of difference but it's something. I opened up my 'box o goodies' and found my std. buffer (no writing) and swapped it out, then proceeded to lube up the BCG and friends and give it another 500 hand cycles.

So, I guess I might ask how much difference do you all think that std. buffer will make vs. the H buffer?

 

[HTR]

It all depends upon whether the gun is slightly over-gassed or under gassed. With the Hornadys blooping out at 5:30, it sounds like it is under-gassed.

If you shoot the SSA 115 tactical loads and they come out at 3 O'clock, then the rifle is set up to shoot hotter ammo, and cycle with normal timing. The H buffer will almost certainly short- stroke with the Hornady ammo and a very new gun.

The problem will be worse with the Hornady using the H buffer. You might actually see a little less SS with the standard buffer, but hotter ammo will also likely assure better timing in that gun. Precision rifle makers usually do not believe in over-gassing guns just to allow for weakling ammo (meaning Wolf in 5.56 and Remington and Hornady in 6.8) .

The SSS springs are actually designed to 1) allow a MUCH longer service life in the rifle and 2) allow the gun to take a slightly higher pressure round, whilst ensuring a little better pressure against the bolt, and in turn delaying unlocking very slightly. The heavier buffers also do this, and can change the timing.

I had to change to a H2 buffer and SSS springs in my Cardinal armory 16" superlight barrel, because it was over-gassed and would throw the combat loads at 1 O'clock. The change reverted the ejection pattern to about 3 O clock.

 

[sredish]

considering I built it from individual pieces, who would be the party that determined the over / under gassing? Would this be Noveske as it's their barrel, block and tube? Also, I'm reluctant to try the 'tactical' loads as it's not a SpecII chamber. I guess I could fix that but I'd feel odd sending a 10.5" upper in the mail, not sure if there's a problem with that.

I did get a bunch more hand cycles and might try the single round shots tonight with the different buffer if I get a chance. Going to Vegas in the morning and won't get back until late Saturday, so if I don't get it tonight, it'll be Sunday.

 

[paulosantos]

considering I built it from individual pieces, who would be the party that determined the over / under gassing? Would this be Noveske as it's their barrel, block and tube? Also, I'm reluctant to try the 'tactical' loads as it's not a SpecII chamber. I guess I could fix that but I'd feel odd sending a 10.5" upper in the mail, not sure if there's a problem with that.

I did get a bunch more hand cycles and might try the single round shots tonight with the different buffer if I get a chance. Going to Vegas in the morning and won't get back until late Saturday, so if I don't get it tonight, it'll be Sunday.

You don't have to use the Combat Loads. YOu can use their commercial loads.

 

[HTR]

considering I built it from individual pieces, who would be the party that determined the over / under gassing? Would this be Noveske as it's their barrel, block and tube? Also, I'm reluctant to try the 'tactical' loads as it's not a SpecII chamber. I guess I could fix that but I'd feel odd sending a 10.5" upper in the mail, not sure if there's a problem with that.

I did get a bunch more hand cycles and might try the single round shots tonight with the different buffer if I get a chance. Going to Vegas in the morning and won't get back until late Saturday, so if I don't get it tonight, it'll be Sunday.

If the barrel was assembled with gas tube and block, then Noveske drilled the gas port, and placed the gas block. As I mentioned above, it is possible the gas port is a little too small, or that the gas block slightly tilted and covered the port, but unlikely given the excellent QC that Noveske usually has. However, that said, choosing a certain size gas port is not a QC issue, it is a design spec thing, and you could ask then what size the gas port is, since some SBR's can be finicky with ammo, due to the choice of port size.

As I said, many builders do not want the gun to be way over-gassed because that places undue stress on your parts.

as for the combat loads, stainless barrels with SAAMI chambers have handled them well in the past, but these were Denny's / WOA's with 1 in 11" twist. If that is a SAAMI, 1 in 10" twist then it might show pressure with the combats. Changing it to SPC II or DMR is very simple and I would definitely do that if I were you. Even Noveske just modified their chamber and is coming out with the 1in 12" twist since they now recognize how much better the barrels perform with such specs. If you can go to the DMR chamber, you'll have an incredibly accurate barrel.

However, the 85 grain Barnes TSX's generate so little pressure that there is no longer any distinction between combat and commercial loads with this bullet. So, I have seen some guns SS with it, because the low weight / mass of the bullet and the pressure reduction of the rings, combined with a small sized gas port, won't reliably cycle the action, especially with a H buffer.

 

[sredish]

If the barrel was assembled with gas tube and block, then Noveske drilled the gas port, and placed the gas block. As I mentioned above, it is possible the gas port is a little too small, or that the gas block slightly tilted and covered the port, but unlikely given the excellent QC that Noveske usually has.

the barrel came with the gas block attached, but removal was necessary to install the barrel nut and gas tube. however, the way it fits and is pinned, there's no way to have it off/tilted at all, which is a good design by Noveske to eliminate installation errors.

as for the combat loads, stainless barrels with SAAMI chambers have handled them well in the past, but these were Denny's / WOA's with 1 in 11" twist. If that is a SAAMI, 1 in 10" twist then it might show pressure with the combats. Changing it to SPC II or DMR is very simple and I would definitely do that if I were you. Even Noveske just modified their chamber and is coming out with the 1in 12" twist since they now recognize how much better the barrels perform with such specs. If you can go to the DMR chamber, you'll have an incredibly accurate barrel.

I would love to change to a DMR chamber... is there a problem with shipping short barrels for smithing, with the whole SBR thing?

However, the 85 grain Barnes TSX's generate so little pressure that there is no longer any distinction between combat and commercial loads with this bullet. So, I have seen some guns SS with it, because the low weight / mass of the bullet and the pressure reduction of the rings, combined with a small sized gas port, won't reliably cycle the action, especially with a H buffer.

Wonder if I should talk to Noveske about the gas port sizing just for info on this situation. I'm still wanting to try and shoot some tonight but today has been one of the most hectic workdays I've experience in awhile; insane customers, nonpaying customers, idiots and whatever else you can imagine.

 

[HTR]

If the barrel was assembled with gas tube and block, then Noveske drilled the gas port, and placed the gas block. As I mentioned above, it is possible the gas port is a little too small, or that the gas block slightly tilted and covered the port, but unlikely given the excellent QC that Noveske usually has.

the barrel came with the gas block attached, but removal was necessary to install the barrel nut and gas tube. however, the way it fits and is pinned, there's no way to have it off/tilted at all, which is a good design by Noveske to eliminate installation errors.

As I expected....Noveske makes good stuff.

as for the combat loads, stainless barrels with SAAMI chambers have handled them well in the past, but these were Denny's / WOA's with 1 in 11" twist. If that is a SAAMI, 1 in 10" twist then it might show pressure with the combats. Changing it to SPC II or DMR is very simple and I would definitely do that if I were you. Even Noveske just modified their chamber and is coming out with the 1in 12" twist since they now recognize how much better the barrels perform with such specs. If you can go to the DMR chamber, you'll have an incredibly accurate barrel.

I would love to change to a DMR chamber... is there a problem with shipping short barrels for smithing, with the whole SBR thing?

No problem whatsoever. the barrel is not the serial numbered part, therefore it is not an NFA item in itself, because plenty of people own pistol lowers (pistols not NFA stamped), and if you send it to Harrison at ARPerformance, I believe that he has a pistol lower in his possession, so there shouldn't be any issue at all.

[quote:g3ttsj3a]However, the 85 grain Barnes TSX's generate so little pressure that there is no longer any distinction between combat and commercial loads with this bullet. So, I have seen some guns SS with it, because the low weight / mass of the bullet and the pressure reduction of the rings, combined with a small sized gas port, won't reliably cycle the action, especially with a H buffer.

Wonder if I should talk to Noveske about the gas port sizing just for info on this situation. I'm still wanting to try and shoot some tonight but today has been one of the most hectic workdays I've experience in awhile; insane customers, nonpaying customers, idiots and whatever else you can imagine.[/quote:g3ttsj3a]

I certainly would. their input is likely to be valuable. Be sure to share the info that you got here with them. They post on 68 Forums from time to time.

 

[sredish]

thanks for the replies htr. i will be talking to them about it. id like to shoot it and see how it does with the lighter buffer before i do though. unfortunately, i wont be shooting it tonight so itll have to be after i get back from vegas on sunday.

ill be sure to keep you in the loop. from just the little ive done with it, i love this short gun and cant wait to get it smoothed out. 90gr speer tnt ammo is on the way as well.

-scott (from my mobile phone)

€dit: also cant wait for my stamp to get here so i can get a stock on it.