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Thread: Can I preload a drop in gas ram?

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    Can I preload a drop in gas ram?

    Hi all,

    I couldn't help myself and decided to buy a drop in gas ram for project 'cock, I took a bit of a risk as it's meant for a Bam B19 but basically the B19 is a copy of the Gamo, which my Brocock Indy is also, anyway it fits and fires nicely but is only doing about 10ftp which I'm not overly bothered about as it's only a back garden gun but would the power increase if I put some preload or extra weight into the piston or does preload only work with springs?

    Your thought please learned folk.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    So glad you posted this, Pete, and I had seen that you'd bought the ram.

    I've never owned or worked on a gas ram, so wouldn't really know the answer, but would have guessed that a little preload could be added in the form of a washer?

    The next of my rifles due for a fettle is my Gamo Vipermax. Actually shoots very nicely. Dead easy and smooth cocking. Accurate. Very little sight picture disturbance. But it twangs like a good 'un!

    Now, everything I've seen on-line indicates that the spring guide is a very sloppy fit. So, on most guns a nice, tight fitting guide and top hat would do the trick. Now, I haven't had a peep inside yet, but looking around, that standard guide looks pretty poor. Looks like it can be driven out of the end block and a new guide obtainable from Welsh Willy. Or maybe Nick might want to make one up. But they look "stepped". I wonder, is that to give clearance for the piston and trigger unit?

    If the actual guide section is well finished I had considered trying to source a spring that fits the guide properly, get Nick to do a top hat and then fit a piston sleeve as I'm sure the reduced spring diameter will leave the spring rattling around the piston.

    Any thoughts?

    And then, I see Knibbs do rams for them. Now, due to the nature of the gun I want to keep the budget low. The cost of a ram might not work out at much more than the cost of a spring, guide, top hat etc. And, as I don't own a rammer, it'd be a cheap, easy way of getting one.

    Now, whilst looking at some videos on-line a few days ago, it seems that some people fit them in with the "fat" end in the trigger housing and having to enlarge the inside diameter of the housing?? But some fit them fat end in the piston, which is how I'd have guessed they should fit.

    But then I like springs and the ease of tweaking etc.

    What do you and other peeps think?
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    If i remember right ,pre loading will not do much .


    From another forum

    The NP has it's full pressure from the moment you start cocking it, versus a spring which is more "progressive" build up to full pressure. The same thing happens, in reverse, when fired. While the spring may only have a percentage of it's max. force left during the end of it's stroke, the NP will still be exerting full value throughout it's stroke. Adding spacers won't gain, with the NP powerplant, and as posted above, slamming the piston into the breech will destroy your piston seal, and I'll bet it'll be a violent shooting cycle. Good Question!


    NP = Nitro piston

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    In view of the above then, Pete, maybe just test with some different pellets and, if you like the way it shoots anyway, leave as is?
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    Quote Originally Posted by bighit View Post
    If i remember right ,pre loading will not do much .


    From another forum

    The NP has it's full pressure from the moment you start cocking it, versus a spring which is more "progressive" build up to full pressure. The same thing happens, in reverse, when fired. While the spring may only have a percentage of it's max. force left during the end of it's stroke, the NP will still be exerting full value throughout it's stroke. Adding spacers won't gain, with the NP powerplant, and as posted above, slamming the piston into the breech will destroy your piston seal, and I'll bet it'll be a violent shooting cycle. Good Question!


    NP = Nitro piston
    Agree that a gas ram will have in effect a degree of pre-load already since even when fully extended there is pressure in there, but as the ram is compressed it must follow that the internal pressure, and hence the "spring" force" will rise further. So Pre-load will increase the stored energy, but it is far from clear if that will be beneficial or detrimental.
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    Tone, I don't normally recommend drop in rams as the two I've had in the past (Theoben AWT units) have both leaked (I'm sure I still have one of them kicking about in the loft), as I've always mentioned (and one reason why I like springs) is you can't adjust the power of a drop in ram (thus why I'm asking now), I was always put off rammers many years ago by Tony Wall at SFS as he told me some right horror stories about them (leaking, different temperatures causing power fluctuation) , I've always liked a rammer and the little faux pas I made early on in the year with my Theoben and trying to convert it to spring (should have just left it alone but my daft brain comes up with some crazy ideas sometimes), but I've read a lot of different reports recently about how different rifle makers are using drop in rams to good effect, the main body of AWT rams I had would slip into the piston body itself and the rod would contact the rear of the cylinder, most of the newer rammer models being produced including the Diana N-tech models are turning the ram around and having the rod in the piston and the main body touching the rear of the cylinder (like the ram I've just fitted), I believe fitting the ram this way reduces the recoil and quickens the piston up as it doesn't have the weight of the rams main body in the piston (but if I turned it around, I wonder if it would increase the power due to having a heavier piston?), I remember seeing on the Theoben site once saying you shouldn't fit washers to preload the ram and you can't cut the rod to reduce power either.

    As for the Gamo spring tuning kit, I have just taken out my welsh willy kit, which actually transforms the rifle from the standard spring set up, the new rear guide is one piece and is stepped as it needs to make room for the trigger housing slotting into the cylinder, there is no twang from the WW kit (mainly because Will makes the guides to fit the springs) and it fires almost the same as it does with the ram fitted.

    Hope that helps mate, if you want any more info then just ask.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    Pete; thank you for this excellent information.

    Makes me even more inclined to stick with the spring driven plant, methinks.

    I've been itching to have a little look inside for a while. Not sure if I can squeeze in some fettling time before Christmas.
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    Quote Originally Posted by TonyL View Post
    In view of the above then, Pete, maybe just test with some different pellets and, if you like the way it shoots anyway, leave as is?
    I will most probably leave it as is, as like I said I'm not overly worried about the power to much but it would have been nice to have it around the 11ftp mark, I expect if the rifle was .22 then it would be around the 11 mark, I may try turning the ram around to see what happens but it has a proper machined end piece that the main ram body slots into and that has the rear pin and screw going into it at the end of the cylinder, it's a shame you can't get the Quickshot rams, pistons and triggers over here as I recon they would transform Gamo rifles.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    Maybe a bit of a pain to try in the other way round then, Pete?

    What pellets have you power tested with?

    And are you happy with the overall feel, cycle and accuracy?
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    Quote Originally Posted by TonyL View Post
    Maybe a bit of a pain to try in the other way round then, Pete?

    What pellets have you power tested with?

    And are you happy with the overall feel, cycle and accuracy?
    I expect I'd have to pack the ram body out and it will rattle around inside the piston, Quickshot who make the ram also make a special piston which is thinner (the rams body fits inside perfectly with no slack) than the Gamo piston and has bearings and is lighter as well.

    I've only tested it with the usual 'go to' AA fields as that's what it's normally the most accurate with, I've not tested the accuracy yet but it shoots pretty nice (just as good as the WW kit when fitted).

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    Tony clear your inbox please.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    Space in inbox now, Pete.

    If your Brocock holds a special place in your heart, Pete, maybe worth pursuing other options.

    My Gamo, however, will only be getting tweaked on a budget in keeping with its overall demeanor. It does actually impress in quite a few areas and doesn't seem pellet fussy and it's clobbered the 75 yards Quigley Bucket at The Bash a fair few times. Firing cycle, as previously mentioned, is very mild.

    Quickie question, if you know.....if fitting a piston sleeve, can it come to the back of the piston or would this interfere with the sear notch? I'm sure this has been asked on the forum in the past, but can't remember the outcome.

    If the finish on the standard guide is good, as per above, I'll most likely just go down the suitable spring and top hat route.
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    I fitted a ram (Theoben awt) to my Vulcan.. I used electrical tape to fit it to the ID of the piston. I don't think you can preload, not by a lot anyway, it's not a spring. While a spring will go coilbound, the ram just stops if the maximum pressure is reached.. remember, gasses are treated like liquids.
    The instructions for fitting the old awt rams called for it to be fitted just touching, so it didn't rattle back and forth, and so that maximum working compression is reached without 'going solid

    Don't ask me how it shoots, I need to resize the Aussie seal I fitted at same time.. it's only doing 8fpe.
    Donald

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    Quote Originally Posted by TonyL View Post
    Space in inbox now, Pete.

    If your Brocock holds a special place in your heart, Pete, maybe worth pursuing other options.

    My Gamo, however, will only be getting tweaked on a budget in keeping with its overall demeanor. It does actually impress in quite a few areas and doesn't seem pellet fussy and it's clobbered the 75 yards Quigley Bucket at The Bash a fair few times. Firing cycle, as previously mentioned, is very mild.

    Quickie question, if you know.....if fitting a piston sleeve, can it come to the back of the piston or would this interfere with the sear notch? I'm sure this has been asked on the forum in the past, but can't remember the outcome.

    If the finish on the standard guide is good, as per above, I'll most likely just go down the suitable spring and top hat route.
    I don't think a sleeve will interfere with the sear notch but if it does then all you'd have to do is just cut out a little square of the sleeve so the sear doesn't touch it.

    Pete
    Far too many rifles to list now, all mainly British but the odd pesky foreigner has snuck in

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    Quote Originally Posted by look no hands View Post
    I don't think a sleeve will interfere with the sear notch but if it does then all you'd have to do is just cut out a little square of the sleeve so the sear doesn't touch it.

    Pete
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