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New and need help - 260 rem cycling problem


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Hi all new here and just built a Lr 308 based gun and it won’t cycle properly


DPms oracle donor gun gen1never fired 

cal- 260 Remington

giessiel 2 stage trigger

larue (Walther?) 22” barrel with plus 2 gas system 

larue low profile gas block and extended tube

jp hp bolt

sjc brake

Stock - carbine and a2 fixed both with appropriate standard buffer, spring and tube

1 standard DPMS mag

ammo larue special 130g match grade


Won’t lock back on the single round mag test won’t load the next round when attempted locks back manually appears under gassed -slo mo video shows bolt comming back just far enough to eject spent case and recook hammer (approx 2/3 way back) only about 20 rounds fired so far


cleaned and lubed well, tried both stocks no change, checked gas port and block alignment good, found and removed burr at port no change, gas port measure .069 by measuring pin - called larue and got proprietary info can’t tell you the port size or ammo details they recommended red spring and h2 buffer which didn’t make any sense to me since it won’t cycle the standard stuff

have not tried any other ammo don’t have any loaded up yet can’t get factory 260 rem locally

knew about the 260 gas gun finikyness going in didn’t expect under gassed symptoms

got any suggestions or experience with this? Any info appreciated



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2 hours ago, Radioactive said:

Stock - carbine and a2 fixed both with appropriate standard buffer, spring and tube

Details like measurements on depth of the buffer tube and buffer weight would be helpful, "appropriate" means different things to different makers.

20 rounds isn't much, sometimes it takes a good number to mate up the surfaces.

That gas port sounds small but don't have any reference on a +2 system so can't be positive.


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Carbine or should I say collapsible is 7 inch tube 11 3/8” spring 3.9 oz buffer 2.5” long

fixed A2 has 9 5/8” tube 12 5/8” spring and 5.4 oz buffer that is 5 1/4” long

those should be Lr 308 compatible 

20 rounds is not much but I thought it should at least cycle enough to lock back

i don’t have a clue what size gas port is proper for this combo

i do know larue did some development with 260 in an ar platform which is one reason I went with their barrel (vs proof research) I’ve also had good customer service from them in the past

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Your gas port diameter for that caliber and that length of dwell time need to be 0.080".  Your gas port is too small.  

Your gun will eat any ammo that you throw at it after you drill that gas port diameter up to 0.080.  :thumbup:


I'm running rifle gas on a 20" Wilson Combat .260 barrel, so we have the exact same dwell time (length). Let's sort he gas system out first, and get it running.  We mess with recoil system parts later, after the gun runs.

Edited by 98Z5V
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Didn’t know but suspected as much. Had a suspicion my barrel may have snuck through without the final port size and that’s why I discovered a burr in the port. Was leary about jumping head first into enlarging the port. Thought about sending barrel back but it took so long to get it the first time. What the hell I’ll fix it and learn some stuff in the process. It’s only money if I have to buy new parts cause I screwed it up.

is there a simple formula or a pressure chart to look at to figure dwell time /port size etc? I have only been able to find some tables of others measured ports and some of those measurements seem suspect.

by the way - thanks

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13 minutes ago, Radioactive said:

is there a simple formula or a pressure chart to look at to figure dwell time /port size etc? I have only been able to find some tables of others measured ports and some of those measurements seem suspect.

I've never been able to find a chart, reference, or anything on it.  Time on the gun is the only thing I know about it, differences here and there, what works, what doesn't.  This is, however, the exact reason we started keeping track of gas port diameters here on the board, everytime we get a new barrel and get it working... 

Stick a 1/4" wooden down down your barrel before you start drilling.  Go with slow drill speed, and light pressure on the drill.  Use a numbered drill bit - ACE Hardware carries the Irwin bits, in numbered sizes.  Don't use fractional bits - not enough difference between them to get close to 0.080".  You need a #46 drill bit (0.081").

For reference:


Edited by 98Z5V
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6 minutes ago, Radioactive said:

Good call on the dowel I have the correct bits. Should I sneak up on the size to see if she’ll run or just go straight to it? I guess worst case adjustable gas block may be required if I get too much gas which is better than it’s running now with not enough. What are you using on your 20” gun?

Standard gas block on mine.  I don't own a single adjustable gas block, in this house. You're only talking about a 0.010" jump in size, so just go straight to it.  It'll be fine if you go slow with light pressure - let the bit eat. 

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Well .081” gas port did the trick

locks back on last round - feeds next round

eject looks to be about 4 o’clock 

now to put it all back together with fixed stock and hand guard in place remount the scope and burn through some ammo to see if any little indications show up

I did notice slight extracter marks on rim, helical marks on body of the case, primers look good and just a slight ejector smudge on the bottom

i have never seen a case body show marks like they do. I assume from chamber needing polished.

I’ll attempt to attach a couple pics if not too big





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Found some stuff on fluted barrels

HK figured it out for delayed blowback systems like the 91

It is supposed to help with extraction by allowing some gas to go around the case. This basically suspended the case on a gas cushion not allowing full case expansion thus preventing sticking during extraction. Apparently it works well for thicker military spec brass but has drawbacks and may actually work the other way when thinner commercial brass is used. There has been some internet chatter about ripping cases apart and leaving the top section in the chamber thus allowing next round to acquire a second neck or shoulder. I assume that would stop the bolt from going into battery.

Reloading camps are split with some saying case issues and others reporting no problems .

Larue went the fluted chamber route in their rifles I assume to aid in extraction and I couldn’t find any real negative consequence reports. Since I purchased my barrel from them that explains the fluting.

I’ll run it like it is and maybe go with some Lapua brass or not (already have about 200 or so mixed pieces). I will keep an eye on my reloads and see what happens.

anyone have experiences with fluted barrels that can give some insights?

is there some info I missed?

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  • 4 weeks later...

 Well.... still having issues

finally had some time to put some rounds through the gun after opening up the gas port - cycled for about 5 shots then would eject but not pick up next round this lasted about 4 or 5 shots it got worse and finally wouldn’t eject

still short cycling

did a quick spring change to a shorter lighter adjustable stock carbine sized spring and it ejects and picks up next round but not enough spring press to fully lock into battery

will break it down for another clean and lube currently almost dripping wet - not even 2 full boxes of ammo run through 

checked the gas block still tight hasn’t moved seems clear when blowing through it

seems like a friction related thing but wanted some other opinions

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