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Discussion Starter #1
So I'm totally confused on which piston to use with my SLP. One is up to 1 1/2 oz. and the other is 1 1/2 oz. and over. I've really only run Buck loads through it and I don't see where buck loads are measured in oz.

Obviously I bring this up because I am having cycling issues. I have done a lot of research on this and the answer seams to be "I bought it to run heavy loads" so they don't care. I guess I kind of do care. I really hate to bash the gun because I really love everything about it other than the cycling problem.

Here is what I have tried.

Running the piston oiled and dry.
Thoroughly cleaning the gas holes from barrel to piston
Really I've only been using the heavy piston. I tried the light one but didn't seam to make much difference.

I'm hoping that someone out there has been experimenting with this and have found some answers as it is getting expensive for me to keep going the way I am since ammo is not cheap these days.
 

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I guess everyone is as confused as I am. I have a call into FN right now. Bob and I are playing phone tag. I'll let you know what I hear back.
 

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Discussion Starter #3
I talked to Bob at FN. he explained that the Heavy piston should only be used for magnum and 3" shells. I guess I'm gonna do some more testing with the light piston and see what happens.
 

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I have been wondering the same thing. In researching the SLP's it does seem to like the heavier loads. I have also read somewhere on line that it likes the higher velocity shells, 1300fps+. Thanks for posing your question to FN as I had the same question since the manual that I downloaded off the net isn't the most helpful in regards to what piston to use. I like the way the SLP handles, but there does seem to be a lot of cycling issues talked about on the net. The ability for a gun to operate 100% is most important to me, and thus I am on the fence with the SLP.
 

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casurfballa said:
I talked to Bob at FN. he explained that the Heavy piston should only be used for magnum and 3" shells. I guess I'm gonna do some more testing with the light piston and see what happens.
Thanks for posting that info - others may be able to use that information!
 

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This could be disappointing.

I just ordered the SLP and it will be here next week. One would think we could get some definitive info from FN on which light loads work best. I would hope they would be doing some ongoing testing to help out their customers.

Otherwise I'll be selling this baby real quick and going with the more popular models.
 

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lmmmmm said:
This could be disappointing.

I just ordered the SLP and it will be here next week. One would think we could get some definitive info from FN on which light loads work best. I would hope they would be doing some ongoing testing to help out their customers.

Otherwise I'll be selling this baby real quick and going with the more popular models.
The only "light loads" I have ever had a problem with are those which are reduced recoil and those are pretty rare. Any other 2 3/4 shell has cycled perfectly, from bird to buck shot. To date, with approx. 600 rounds through my SLP, I have had two malfunctions, both with reduced recoil loads. Everything else has been perfect. I keep Hornady TAP 00buck in it at home and that has always (200 rounds) cycled perfectly.

I love this shotgun and definately trust it.
 

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Discussion Starter #8
jwinch2 said:
lmmmmm said:
This could be disappointing.

I just ordered the SLP and it will be here next week. One would think we could get some definitive info from FN on which light loads work best. I would hope they would be doing some ongoing testing to help out their customers.

Otherwise I'll be selling this baby real quick and going with the more popular models.
The only "light loads" I have ever had a problem with are those which are reduced recoil and those are pretty rare. Any other 2 3/4 shell has cycled perfectly, from bird to buck shot. To date, with approx. 600 rounds through my SLP, I have had two malfunctions, both with reduced recoil loads. Everything else has been perfect. I keep Hornady TAP 00buck in it at home and that has always (200 rounds) cycled perfectly.

I love this shotgun and definately trust it.
Are you using the Light or Heavy piston?
 

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casurfballa said:
jwinch2 said:
lmmmmm said:
This could be disappointing.

I just ordered the SLP and it will be here next week. One would think we could get some definitive info from FN on which light loads work best. I would hope they would be doing some ongoing testing to help out their customers.

Otherwise I'll be selling this baby real quick and going with the more popular models.
The only "light loads" I have ever had a problem with are those which are reduced recoil and those are pretty rare. Any other 2 3/4 shell has cycled perfectly, from bird to buck shot. To date, with approx. 600 rounds through my SLP, I have had two malfunctions, both with reduced recoil loads. Everything else has been perfect. I keep Hornady TAP 00buck in it at home and that has always (200 rounds) cycled perfectly.

I love this shotgun and definately trust it.
Are you using the Light or Heavy piston?
I have always used the light piston. I have not, to date, shot loads that were heavy enough to require the larger piston. 2 3/4 00buck works perfectly everytime with the light piston for me.
 

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I picked up my Mark I on Friday. Can't wait to shoot it.

I noticed looking through the barrel while cleaning there seemed to be a couple of notches about half way down the barrel. Anyone else notice that on theirs.
 

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Discussion Starter #11
lmmmmm said:
I picked up my Mark I on Friday. Can't wait to shoot it.

I noticed looking through the barrel while cleaning there seemed to be a couple of notches about half way down the barrel. Anyone else notice that on theirs.
Got a little click happy there!!!! :D

To answer your question... Those are the gas ports that feed to the piston.

I didn't really notice in the manual where it shows cleaning instructions. What I have been doing is after disassembling the gun and removing the piston I take a Q-tip and dip it in some hopps and run it through the little 2 little holes. If I remember right I had to pull some of the cotton off the tip because I couldn't get a full one through. I've been looking for a tiny little brush that I can run through it. I even tried a .17 cal brush but it was still to big.
 

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casurfballa said:
[To answer your question... Those are the gas ports that feed to the piston. quote]

I have no experience with a smooth bore so it's okay that the inside of the barrel isn't "perfect" but has those marks?
 

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Discussion Starter #13
lmmmmm said:
casurfballa said:
[To answer your question... Those are the gas ports that feed to the piston. quote]

I have no experience with a smooth bore so it's okay that the inside of the barrel isn't "perfect" but has those marks?
maybe you need to take a picture of thes marks. I guess they could be something else.
 

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upon further inspection the "marks" are at the point that the gas block is attached to the barrel...

do you lube the inside of the gas block or magazine tube to make it easier to pull the barrel off???
 

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Discussion Starter #15
lmmmmm said:
upon further inspection the "marks" are at the point that the gas block is attached to the barrel...

do you lube the inside of the gas block or magazine tube to make it easier to pull the barrel off???
Nothing personal LMMMMM but your kinda hijacking the thread a little here. Please post the question as a new topic. Just helps us keep things organized a little better. I'll watch for it.
 

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My SLP has been great with light loads. Just use the light piston and keep the rings oiled with mobil1. Double check to make sure you have the light piston installed.
 

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casurfballa said:
I didn't really notice in the manual where it shows cleaning instructions. What I have been doing is after disassembling the gun and removing the piston I take a Q-tip and dip it in some hopps and run it through the little 2 little holes. If I remember right I had to pull some of the cotton off the tip because I couldn't get a full one through. I've been looking for a tiny little brush that I can run through it. I even tried a .17 cal brush but it was still to big.

There are much much better cleaning products that you can use to keep your gas piston in tip top condition. I've been shooting gas operated shotguns for many years, mainly Berettas, for both all of my hunting and target shooting. While there are great advantages to gas operated shotguns ( mainly the lower felt recoil ), cleaning the gas system is the main extra chore that you have, And it is not easy to do ( a real pain actually ), unless you have effective cleaning products designed specifically for that purpose.

I will not repeat myself here, but checkout my post in the thread titled: "Cleaning Gas Valve" Here is a link to it:

http://fnforum.net/viewtopic.php?t=3415

Try those products and the cleaning tips that I mentioned, and you will have your gas piston looking like new.

I've been able to shoot my FN on Sporting Clays courses using light Remington Gun Club and Game Loads with 100% reliability. Of course, I get some bizarre looks from many of the shooters with their fancy Beretta and Browning overunders, but hey, it is good practice for me in using my FN.

.
 

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piston

The manual and FN's FAQ page are QUITE clear about which piston to use with what sort of load:

The light piston is set for minimum loads of 2 ¾”, 3 dram, 1 1/8th oz and a maximum of 2 ¾”, 3 dram 1 ½ oz.

The heavy piston is set for loads in either 2 ¾” or 3” Magnum with a shot charge larger than 1 ½ oz.

What's NOT clear is the labeling on various brands of ammo which don't always bother to describe drams or shot charge weight.

If my ammo is 3" or says "magnum" I know I'm using the heavy piston. Not sure if I should guess based on velocity claims on the ammo box which piston to use.
 

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I've had my SLP for a few months now and always run mine with the lighter load piston. I rarely shoot 3" mags, so I just put in the lighter piston (I can't remember which was installed when I bought mine). Also I found that just going out and shooting a few boxes of shells (cheap birdshot works fine for me) to start getting it broken in was a good start as well. if a gun has tight tolerances, when it's new it might be a bit "stiff" and need some rounds to break them in. I know when I get one of the little 380 pocket guns I always put 200+ rounds down it before I consider it "broken in". plus it gives you a chance to see if there are any feeding/extraction issues to consider. but usually that show up right off the bat and I haven't had any problems since.

so basically unless you are running 3" magnums or really heavy loads (magnum performance out of 2 3/4") run the light piston and make sure you have run a bunch of rounds thru the shotgun to get it broken in and see if there's any particular rounds it doesn't like...
 

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Cycling

My SLP came with the heavy piston installed. I took it out and tried to run some #6 loads through it and it wouldn't cycle. I took it down right in the field and swapped out the heavy for the light piston. It cycled fine after that and I had a great time shooting it. It's a real jackhammer. I will keep running the light piston all the way up to 00. I will run the magnum loads through my old Defender 1300 pump whenever I feel like bruising my shoulder.
 
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