Trouble with JP LMOS

[lucas]

The gun has worked perfect since march of 03,now i'm having problems.Part of it was my gas block set screw had backed out to far,but now i can no longer shoot around 100rds before cleaning and lubing.At about 75rds it short stroked once then fed but would not lock back after last round,then i wiped and oiled the carrier and was fine again. Its become so much more temperamental all of the sudden. Is there a rule of thumb for how to tell when you need a new carrier,and what is the most important part that needs lubed at some point during the match,the bolt through the holes only as i've read one person does during a match or pulling the hole thing out as i did and wiping and lubing?I never use to have to do anything during the short matches around here before.

[Zak Smith]

Wouldn't short-stroking be a symption of not enough gas?

[lucas]

And according to JP to much gas aswell.I ajusted down my set screw about where it was before it had worked its way past the top of the gas block, and shot 5 rounds at a time from 3 mags many times to make sure it would lock back,then around the 75rd mark after shooting some more, problems stated again as i stated above.Part of what JP said about the gas was if there is to much the carrier will slam the buffer harder forcing the carrier and bolt forward at a accelerated speed being to fast,and remember after wiping and lubing problems stopped again,wouldnt that rule out not enough gas anyway?I'm just wondering if its time for a new carrier.I'm going to call JP again,but i thougt someone else might have some feed back.

[George]

Been said around here before and I will say it again because it is usually right.

Check your gas ring, if it is the one piece spiral type and you are using an "Alloy" LMOS carrier, either change back to the old 3 piece ring set, or be prepared to put a few drops of oil in the holes of the bolt carrier and hand cycle it in every 75-100 rounds or the bolt will start unlocking "stickily" and this will cause no end of ills.

The one piece McFarland style spiral ring just seems to get sticky in Alloy carriers after the system gets worn in. I am going on 9k with my original LMOS carrier and it is starting to lose plating, it has a big deep hammer groove on the bottom, but it is still running strong and reliably. I switched to the 3 piece rings at my second bolt rebuild (new rings, extractor spring & rubber damper every 3500ish rounds). For the first 7k on the rifle, I lubed the carrier as described and just figured it was a race gun thing and I should live with it. It ran 100%, all of the time with this periodic lube the carrier routine.

Then I read a post by Kurtm about the spiral ring thing. It changed my life ;-) I switched back to a 3 piece set and I am now going over 700 rounds without doing anything but some oil in bolt holes every 250-300 rounds (if I remember to do it at all).

It did make a difference for me.

As far as the gas block screw goes, I have one of the self-adjusting type too ;-) After my second call back to John when it was new, I took John's second piece of advise and put a drop of blue loctite on it after verifying it's adjustment for "my" reloads. On the first call about it I was told to shoot it a bit and it should get set in place by the combustion residue. I did, it didn't, so hence the 2nd call and no problems for 8500 rounds with the loctite.

--

Regards,

[kurtm]

New gas rings, and check your carrier key to make sure it is tight. I've had gas rings do this befor but not the key but check anyway. KURTM

[lucas]

So the JP gas rings are Mcfarland?I didnt notice or know what i was looking at.I'm ordering the 5 pac of 3 bolt gas rings from Brownells tomorrow.Who's bolt should i buy if i want a spare?I'm also going to check with MSTN,they have a lightened up SS carrier to compare weights with the JP SS carrier which is 9oz according to Brownells.