Author Topic: BAM B-51 - Better Late Than Never (Read 33661 times))

rsterne · « **Reply #60 on:** December 21, 2014, 11:46:55 PM »

If the JSB Monsters are accurate I think I'll leave it the way it is.... If not, then faced with detuning it from 50 FPE down to 36 then you are probably right.... With enlarging the ports to 3/16" I suspect 70ish FPE wouldn't be too difficult in .25 cal.... but then I'm faced with the same problem, too much power for the JSB Kings, so then detune it back to 50 FPE again to use them.... Not a lot of point if it shoots the 25 gr. Monsters well, they are the same weight, and being less frontal area will have a better BC than the Kings.... I hope it likes them at longer ranges....

On the other hand, if JSB ever bring out their 34ish gr. Super Kings.... hmmmmmmmmmmmmm....

BTW, I modded my striker the way you did, only took off about another 0.040" and it made NO difference, but I couldn't leave some (potential) on the table.... *LOL*.... I think the stroke is about 0.66"....

Bob

SpiralGroove · « **Reply #61 on:** December 21, 2014, 11:49:30 PM »

Great find Ribbonstone!
Nice job........... Hope it works out well for you

Bob inspired me crack open my BAM B50 and check delrin hammer, remove valve sail, change valve spring and vent hammer as you did (different method). Got it all together, but my "old nemesis" (valve poppet) appears to be leaking at its seat. Will pull the whole sha...bang again tomorrow and hopefully get her going.

Kirk

SpiralGroove · « **Reply #62 on:** December 22, 2014, 01:22:47 PM »

Hey Bob,
Now that your tune is finished, what do you think about the quality of this rifle for $209 (B50) or $259 (B51)

??

Is this a deal or what ??....................Kirk

rsterne · « **Reply #63 on:** December 22, 2014, 01:41:06 PM »

DEFINITE DEAL !!! However, they are for those who like to play, as the way they are stock, they have too hard a hammer strike and need to be tamed down a bit.... much like the new Discos (whereas the old ones were about perfect).... Downloading "The Book" and reading through it BEFORE you purchase would be a good idea, just to let you know what you are in for....

Now that I have been inside and experimented on my B-51 first hand, there are some things I would do differently than "The Book".... For one thing, I dislike the hammer travel adjustment (on any rifle, IMO more is better), I would recommend that you set it to maximum (flush with the end of the hammer, even shorten the hammer if you can, but make certain you don't plug the vent holes).... Then fit a weaker spring (hoping you can find one that suits your tune) and tune using preload adjustments, either by fitting an RVA or making a selection of top hats and shims.... This allows you to use the least possible hammer spring tension, which given the design of the skinny bolt and the small amount of material around the cocking pin, may drastically increase the serviceability of that part.... Like Ribbonstone, that greatly concerns me, I really wish they had gone with a larger OD bolt....

Tuning the gun for a lower pressure fill by using the McMaster Carr spring recommended in "The Book" is probably a really good idea, it just wasn't the direction I wanted to go.... I would be curious what fill pressure you would end up with setting the striker flush with the end of the hammer, installing the McMaster Carr spring, and no other changes, both in .177 and .22 cal.... That might be all you need to do to end up with a pretty nice setup....

Bob

Pellgunfun · « **Reply #64 on:** December 22, 2014, 02:03:08 PM »

Awesome stuff!!!!

Bob, would you be interested in producing your own "the book"? I think you may find that it quickly becomes the "holy grail" for all BAM owners, especially those in .22cal.

You could call it "Book 2: taking it to the next level and beyond".

rsterne · « **Reply #65 on:** December 22, 2014, 04:33:45 PM »

Two problems with that.... upsetting those who did all the ground work and wrote "The Book", and finding the time to do it.... especially the latter.... If I wrote a book on airguns I wouldn't be able to do the development, that would have to stop.... On the other hand, maybe the book wouldn't be out of date when it was finished.... just a couple of years later after I started working on them again.... because ideas and methods are always changing.... A perfect example is my findings compared to "The Book"....

I've learned soooooooo much over the past 7 years since I got back into airguns I can't believe it.... Equally inspiring is that I'm still learning with every project.... with no end in sight, fortunately.... God I love this hobby....

Bob

Ribbonstone · « **Reply #66 on:** December 22, 2014, 07:29:54 PM »

It’s a little fast.

Shortest daylight hours of tye year, so only had time to run one shot string with one weight pellet.

Shortened the striker nose to increase stroke to something like .67-.70”.
Decreases striker string preload slightly (cocking effort is acceptable).
In doing so, found that previously the vent hole was mostly blocked. It’s now open.
Runs right at about 150-155BAR (call it 2300psi)

Efficiency seems good (will have to re-run those numbers as I might have fouled that up).

Probably will never know what made the difference, the longer stroke or the now completely clear vent hole.

BARELY got my 20 shot goal.

Really think it’s driving those 15.9’s a little fast, but should be good with 18.1’s or 21gr. pellets (and the heavy weights might add a shot or two to the count). If the past is any guide, those heavy weight pellets will also up the energy level a bit (probably to 33 foot pounds).

So I’ll be looking to trade 10% of the energy per shot for a bit more shot count; probably with a slightly smaller transfer port. With luck, might get 15-20% more shots for that 10% energy drop.

rsterne · « **Reply #67 on:** December 22, 2014, 10:29:42 PM »

Three choices to get the velocity down.... heavier pellets, less preload and a lower fill, or smaller transfer port.... The choice depends on what you want to fill to.... but the smaller port may give you the most shots at lower FPE.... Congrats on getting a better all around setup, though.... That string looks similar to my lowest tune in Post #46 (the black line) except mine was 23 shots at 34.8 FPE with 18.1 gr. starting at 2200, but certainly very similar.... Me, I'd try the 18.1 gr. JSB Heavies, I haven't got a gun that doesn't like them, and you'd be shooting them in the low 900s.... but if you want less energy and more shots, then yeah, a smaller transfer port....

Bob

Ribbonstone · « **Reply #68 on:** December 22, 2014, 10:58:49 PM »

Will test the 18.1gr. JSBs and the 21gr. pellets as I find time this week and see if the energy gain for heavy pellets is still in proportion to the old tune. If it is, then I’d expect the 21gr. pellets to end up at about 33 foot pounds, which is a bit over my goal.

So I’ll trade that 10% “extra” energy for more shots one way or another.

Might decrease the spring tension a little and see how that plays out, but suspect that I’ll eventually try a slightly smaller transfer port.

Shot this last week with the old tune. Can tell I just glued the target to a cardboard Coke box, tossed a rock in the box, and set it out at the longer distance I could manage,

So…1.4” at 45 yards is worth about 3.1MOA, so with 1/8MOA “clicks” on the scope, tried 25 clicks up. Not perfect, but for an old cheap scope, it works.

bubba zanetti · « **Reply #69 on:** December 23, 2014, 01:45:43 PM »

Good thread guys, my BAM work has come to a grinding halt and the reasons in this thread are why. There are twenty different ways to go and I don't have the time to work on it

. High chance it is getting shipped to someone to do the work.

BZ

rsterne · « **Reply #70 on:** December 23, 2014, 01:55:48 PM »

The big thing is to decide what you want and then focus on how to get there....

Bob

nervoustrigger · « **Reply #71 on:** December 23, 2014, 02:08:12 PM »

Wow, I'm very tempted to pull mine back apart and incorporate some of these changes. Seems like I was getting about 24 shots around 30fpe (JSB 18.1gr) with a velocity spread of 4% with the current tune but the energy levels you're getting, Bob, is just intoxicating

. It shoots the JSB heavies so well and I just haven't had much luck with the Monsters or Eun Jins with this barrel so I'm torn on whether it would be worth the trouble. I'm tempted nonetheless because when I tuned it last time, I didn't know much about PCP internal workings so I was afraid to make any permanent changes. I'm over that hump now

bubba zanetti · « **Reply #72 on:** December 23, 2014, 02:20:17 PM »

Quote from: rsterne on December 23, 2014, 01:55:48 PM

The big thing is to decide what you want and then focus on how to get there....

Bob

Bob:

That's easy. shoot a 10 grain pellet in the mid 800 to 900 fps range with little deviation for decent shot count using the BAM for FT shoots.

I am going to anneal the trigger and straighten it as you have noticed its big and clunky the way it sits now. But all the other stuff...that's the issue.

BZ

moorepower · « **Reply #73 on:** December 23, 2014, 03:22:10 PM »

Correct me if I am wrong, but it does not seem there is a negative to turning down the O.D. of the poppet. I really like the direction this went. I had accepted that these guns just won't run on 3kpsi. I am wondering what if the poppet was turned down and the spring/ brass washer was left stock. I am sure the power would be less, but could it help level the shot string/ extend shot count?

bubba zanetti · « **Reply #74 on:** December 23, 2014, 03:49:43 PM »

Moorepower:

Mine will run at 2800 psi (I never pumped to 3000) and launches JSB 10 grainers at 960 fps.

BZ

nervoustrigger · « **Reply #75 on:** December 23, 2014, 03:53:42 PM »

BZ, 21fpe in .177 cal...that's a fast icepick!

bubba zanetti · « **Reply #76 on:** December 23, 2014, 03:57:37 PM »

Quote from: nervoustrigger on December 23, 2014, 03:53:42 PM

BZ, 21fpe in .177 cal...that's a fast icepick!

Yes it is Jason LOL! That's also the problem for FT. I can get great accuracy with JSB's and H&N .4.51 Barracudas, but at those speeds I cannot use it for FT. And once I shoot down far enough on pressure my POI starts to shift too much. My BAM needs "smoothed out" just like everyone says.

Its also really LOUD at that pressure.

BZ

rsterne · « **Reply #77 on:** December 23, 2014, 05:25:31 PM »

If I had it to do again, I would taper the OD of the poppet at the seat to 5/16".... I would still reduce the thickness of the washer on the spring seat because I think driving the spring to coil bind is the reason for breaking the poppets.... However, if you drastically reduce the hammer strike to compensate for the smaller poppet and NEVER shoot the gun at too low a pressure (what is that, I don't know) you could probably leave the spring and spacer alone.... When you do the above you MUST fit a weaker hammer spring to compensate, and you would be well advised to lighten the hammer as well, certainly replace the top hat with plastic, then it's easy to reduce the preload by reducing the thickness of the "brim" of the hat (mine is now 0.10" instead of 0.50")....

Like most mods to a PCP, change one thing, that leads to two, which lead to four, and pretty soon you are nearly starting from scratch.... It's just what happens when you start modding, no solution to it but dive in with your eyes WIDE open.... BTW, properly tuned a PCP should be QUIETER at high pressure at the same FPE level....

Bob

rsterne · « **Reply #78 on:** December 23, 2014, 05:34:52 PM »

moorepower, your Inbox is full....

Bob

nervoustrigger · « **Reply #79 on:** December 23, 2014, 06:10:57 PM »

BZ, since you are doing FT, have you considered installing an in-tube regulator? In .177, you can get a ton of consistent shots with a moderate pressure setpoint. It would need some porting and a lightened striker as compared to stock.

My son's QB79 fitted with a 1000psi 13ci Ninja bottle gets over 100 15fpe shots on a fill. The volume is larger but I did not install an RVA to fine tune the striker preload so it's wasting air, so I would not be surprised if you could extract 60-70 shots from the B51 with some tuning.

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BAM B-51 - Better Late Than Never

Author Topic: BAM B-51 - Better Late Than Never (Read 33661 times))