JP Buffer / spring question

[HiCapMag]

Just got a JP upper with the LMOS stainless bolt carrier. Also have a low mass buffer on the way. I forgot to ask if the standard rifle length stock spring is to be used in the system. I assume it is ok, but.....well, you know what assume is.

Thanks.

[TRUBL]

I believe that the low mass buffer is a rifle buffer.....and is to be used with a rifle spring and a rifle buffer tube

Tim

[mjbine]

I believe that the low mass buffer is a rifle buffer.....and is to be used with a rifle spring and a rifle buffer tube

Tim

I agree.

[SingleStacker45]

would using the wolf reduced power buffer spring be good? I'm thinking of how the light spring in my pistol helped with recoil. I've got the young mfg skeleton carrier on the way and I'd like to combine that with the lmos buffer or a lightened buffer. Problem is I've got the geissele trigger group which has a pretty stout spring. I do have a RRA I could switch to though.

Mule

Edited February 20, 2009 by SingleStacker45

[busyhawk]

Mule,

If you don't have an adjustable gas system "then" perhaps a lighter OP spring might work. An adjustable gas system will work better since you want a strong spring to strip the next round from the full magazine and chamber the round. All you have to do is adjust the gas so you don't feel the buffer/bolt/carrier slam to the rear of the tube. You can't do this with a pistol and yes a pistol round from a pistol magazine takes less spring to make all work. A rifle needs a little more umph to insure it works.

Hope I explained this correctly so one might understand...

Sincerely,

RLTW,

Scott

[XD Niner]

I have the same LMOS bolt carrier and it works just fine with a conventional rifle spring and buffer. I'l be interested to see if you observe an improvement with the LMOS buffer.

Edited February 21, 2009 by XD Niner

[SingleStacker45]

Mule,

If you don't have an adjustable gas system "then" perhaps a lighter OP spring might work. An adjustable gas system will work better since you want a strong spring to strip the next round from the full magazine and chamber the round. All you have to do is adjust the gas so you don't feel the buffer/bolt/carrier slam to the rear of the tube. You can't do this with a pistol and yes a pistol round from a pistol magazine takes less spring to make all work. A rifle needs a little more umph to insure it works.

Hope I explained this correctly so one might understand...

Sincerely,

RLTW,

Scott

Thanks. I am using an adjustable gas system so tuning is not a problem in that area. My thought process was that having a lighter mass would cause the standard spring to accelerate the carrier forward faster possibly increasing the chance of slamfire as I have read in another post and just at a rate that is unnecesarily fast for proper operation. I realize that there is more tension on the cartridge in the magazine due to the higher round count and the increased surface contact between the magazine and the round. I also realize the buffer spring has to push hard enough to activate the extractor in this case since unlike a pistol there is no controled feed. I think I'll get the wolff spring and try it with the lightened carrier when it arrives. I also wonder about using the lighter buffer with this setup. I suspect that the ratio of buffer weight and carrier weight needs to be balanced to reduce the chance of "bolt bounce" that I read of as too light of a buffer would cause the carrier and buffer to separate during the cycle. That could make things weird. After weighing and looking at JP's site it looks like the carrier should be roughly twice the weight of the buffer. Your thoughts? I'm also concerned about the role the hammer and hammer spring play since I am using a full power Service rifle trigger from Geissele automatics.

Mule

Edited February 21, 2009 by SingleStacker45

[steel1212]

The LMOS buffer is 3oz. I use a VLTOR EMOD stock and a standard 3oz car buffer and car spring. Think about it like this, with a heavier stock rifle buffer its going to take more gas pressure to push back a heavier weight and then that weight is going to have more enertia hitting the back of the buffer and fine tunning it to not would be harder in my opinion. If you have a lighter buffer it takes less gas to push it back and there for your going to feel it less. JMHO

[busyhawk]

Mule,

Good question...I have a JP 15 with the LMOS carrier and carbine/colapsible stock/buffer combo and the buffer has "NO" weights in it at all. I just took all the weights out of the buffer and closed off the gas system almost all the way off. I just shot the rifle and slowly opened the gas system until the rifle would work. Then I opened the gas screw another 1/2 turn and called it quits. I tested with the lightest loads of course so then knowing the rifle would work with more pressure. Has been working great and I love the impulse. I do have an extra TI firing pin just incase but have yet to have to use it.

Never experienced any bounce but with the standard spring I am guessing it is doing the trick...

Test some stuff out and post what you find out....

RLTW,

Scott

[kurtm]

Bolt bounce happens on closing. It is caused by the bolt carrier coming to a sudden stop and rebounding out of battery slightly...CLICK. It is not the weight of the buffer rather the weights in the buffer that cascade forward AFTER the bolt is closed that keep it closed, sort of like a dead blow hammer. The J.P. lightened buffer has very light "weights" inside that still cascade forward and that is why it works. Most folks that run an empty buffer every once in a while will get the click, If you run just one buffer weight with a spacer, it will work, but the weight has to have just a little room to move and a rubber spacer on each side or...CLICK.

I doubt a lighter spring will be a good thing as to stripping rounds out of a magazine, especially anything that hold more than 30 rounds....BUT every rifle is different. I know one top shooter that runs a light buffer with a extra power spring jst so it will strip rounds out of a 45 round DPMS mag.

I am NOT saying don't experiment, but I would have a regular spring on hand. KurtM

[SingleStacker45]

Bolt bounce happens on closing. It is caused by the bolt carrier coming to a sudden stop and rebounding out of battery slightly...CLICK. It is not the weight of the buffer rather the weights in the buffer that cascade forward AFTER the bolt is closed that keep it closed, sort of like a dead blow hammer. The J.P. lightened buffer has very light "weights" inside that still cascade forward and that is why it works. Most folks that run an empty buffer every once in a while will get the click, If you run just one buffer weight with a spacer, it will work, but the weight has to have just a little room to move and a rubber spacer on each side or...CLICK.

I doubt a lighter spring will be a good thing as to stripping rounds out of a magazine, especially anything that hold more than 30 rounds....BUT every rifle is different. I know one top shooter that runs a light buffer with a extra power spring jst so it will strip rounds out of a 45 round DPMS mag.

I am NOT saying don't experiment, but I would have a regular spring on hand. KurtM

I'm running the standard spring now so I can switch it back. I won't know till I get the new carrier(couple weeks out) if it will strip the rounds. The spring though is a wolff and it is described as "High-quality, reduced power, action spring helps cure feeding problems caused by excessive bolt “bounce” in rifles configured for 3-shot burst or full-auto modes of fire. Helps shooters fine-tune action cycling for light, target/varmint loads in semi-auto rifles. "

Sounds like it will be plenty strong. I'm more worried about the full power hammer spring giving me grief. Thanks for the clarification on bolt bounce.

Mule

Edited February 22, 2009 by SingleStacker45

[SingleStacker45]

Ok got the setup running. At first the gas rings were tight and the carrier was a bit rough in my 'el cheapo' upper but after some working it is smoothing out. With the lighter spring it would not go into battery at first so I shot it a hundred rounds or so with the full power spring to smooth it out then went to the reduced power spring. I was able to turn down the gas system a full turn on the screw over the stock spring, carrier and buffer. I'm not sure I could tell much of a difference in the cycling althoug it reminded me of my glock 34 shooting 147 grains. I was shooting .2 splits on my shots and it was keeping up just fine though but it was slugish. I think if you are going lightweight though I would go with JP's kit and use the wolff reduced spring to slow things down a bit. I'll try that on my next build and report back.

Mule

[busyhawk]

Mule,

Thank you for the update...I will keep this in the back of my brain housing group.

RLTW,

Scott

[grywlfbg]

The LMOS buffer is 3oz. I use a VLTOR EMOD stock and a standard 3oz car buffer and car spring. Think about it like this, with a heavier stock rifle buffer its going to take more gas pressure to push back a heavier weight and then that weight is going to have more enertia hitting the back of the buffer and fine tunning it to not would be harder in my opinion. If you have a lighter buffer it takes less gas to push it back and there for your going to feel it less. JMHO

This doesn't jive with my experience switching from the JP SS carrier to the Al one (with LMOS buffer and standard rifle spring). I found I needed MORE gas with the AL carrier. My assumption is that the AL carrier doesn't have as much inertia to carry it to the rear of the tube in order to then strip the next round, lock back, etc. Perhaps you could then combine that with a lighter spring?

[mpeltier]

Kurt is right on.

I experimented with the Wolf reduced power spring with a JP LMOS (stainless not aluminum) carrier and JP LMOS buffer (the red one) In three differant guns that otherwise ran 100%. After adjusting the gas blocks and using P-mags (nothing I have found strips rounds easier) the spring does not always have enough strength to fully chamber a round. Sometimes I would get thru a magazine without a hitch, sometimes not. Standard springs are all I will use after that experiment. I also could not really tell any differance in the recoil or feel of the impulse.

I also experimented with a standard rifle buffer and removed three weights and replaced the equivalent length of the 3 weights with a piece of aluminum rod. It ended up weighing just a fraction of an ounce more than the JP red buffer, yet I can tell no differance between the two when shooting. It runs perfectly also.

Edited April 3, 2009 by mpeltier

[SingleStacker45]

Bolt bounce happens on closing. It is caused by the bolt carrier coming to a sudden stop and rebounding out of battery slightly...CLICK. It is not the weight of the buffer rather the weights in the buffer that cascade forward AFTER the bolt is closed that keep it closed, sort of like a dead blow hammer. The J.P. lightened buffer has very light "weights" inside that still cascade forward and that is why it works. Most folks that run an empty buffer every once in a while will get the click, If you run just one buffer weight with a spacer, it will work, but the weight has to have just a little room to move and a rubber spacer on each side or...CLICK.

I doubt a lighter spring will be a good thing as to stripping rounds out of a magazine, especially anything that hold more than 30 rounds....BUT every rifle is different. I know one top shooter that runs a light buffer with a extra power spring jst so it will strip rounds out of a 45 round DPMS mag.

I am NOT saying don't experiment, but I would have a regular spring on hand. KurtM

Update: my setup ran fine for the first 500 rounds or so but the started having failure to strip rounds out of the mag.Three different occasions in saturday's match the bolt would stop with a round half way out of the mag. I made the mistake of racking it the first time which caused a double feed since the extractor had not grabed the case that early in the cycle. the next two times as I droped the mag and the round went into battery so it seems not to be a feed issue. I'm thinking the lighter spring lost its tension over this time and began having trouble overcoming the magazine tension. curiosly though the failures occured about half way through the magazine on three different occasions. I would have thought it would have had more trouble on a full mag. I switched the spring for the ISMI CS spring and reset the gas so we'll see how it runs this weekend.

Mule

[mlmiller1]

Update: my setup ran fine for the first 500 rounds or so but the started having failure to strip rounds out of the mag.Three different occasions in saturday's match the bolt would stop with a round half way out of the mag. I made the mistake of racking it the first time which caused a double feed since the extractor had not grabed the case that early in the cycle. the next two times as I droped the mag and the round went into battery so it seems not to be a feed issue. I'm thinking the lighter spring lost its tension over this time and began having trouble overcoming the magazine tension. curiosly though the failures occured about half way through the magazine on three different occasions. I would have thought it would have had more trouble on a full mag. I switched the spring for the ISMI CS spring and reset the gas so we'll see how it runs this weekend.

Mule

Not because I know ANYTHING(I don't!) but because I am curious, did you try giving it more gas when it started malfunctioning? Perhaps you were not getting full stroke of the buffer? Not going all the way back properly compressing the spring could give you not enough forward inertia--in my mind, anyway!

Just curious & learning, or trying to anyway.

MLM

[SingleStacker45]

Update: my setup ran fine for the first 500 rounds or so but the started having failure to strip rounds out of the mag.Three different occasions in saturday's match the bolt would stop with a round half way out of the mag. I made the mistake of racking it the first time which caused a double feed since the extractor had not grabed the case that early in the cycle. the next two times as I droped the mag and the round went into battery so it seems not to be a feed issue. I'm thinking the lighter spring lost its tension over this time and began having trouble overcoming the magazine tension. curiosly though the failures occured about half way through the magazine on three different occasions. I would have thought it would have had more trouble on a full mag. I switched the spring for the ISMI CS spring and reset the gas so we'll see how it runs this weekend.

Mule

Not because I know ANYTHING(I don't!) but because I am curious, did you try giving it more gas when it started malfunctioning? Perhaps you were not getting full stroke of the buffer? Not going all the way back properly compressing the spring could give you not enough forward inertia--in my mind, anyway!

Just curious & learning, or trying to anyway.

MLM

I did not only because the bolt was still locking back fine on the last shot. It just seemed slugish from the getgo with that reduced power spring. I put in the flatwire spring and it seems very snappy now. I opened the gas about a half a turn to get the bolt to lock back then gave it another quarter to give it some margin. Gonna shoot drakes landing nc today so we'll see how it runs.

Mule

[SingleStacker45]

Rifle running fine with the flatwire but quite a bit more fouling in the carrier. I also don't like how the extra spring handles as far as charging etc. I'm gonna trie a brownells standard power CS spring and see if that is a happy medium. I would still like to try the JP LMOS system with the reduced power spring. That may be the way to go.

Mule