DAY 6: BAM .177

[Ribbonstone]

Day 6:

Went ahead and straigtened the trigger a bit to get rid of the worst of the “cat tail” shape.  Took a chance and just bent the trigger with padded pliers.  Realize it certainly could break, but also realized that if I did, I could silver solder it back into working shape.

Simple rifle (I admire that quality):



Trigger didn’t break; got a more pleasing shape:




From the shot counts on Day 5, decided to slow the rifle down a bit. Decided to try for a little less power, looking more for something about 20 foot pounds with the more common 10.3-10.6gr. .177 pellets.

Day 5:

http://www.gatewaytoairguns.org/GTA/index.php?topic=83981.0

So I tried a little less striker weight. Kept the striker spring force the same as I didn’t want to increase the force needed to cock the rifle.

Form a couple left-over from the 51 and by taking the (21gram) one from inside the BAM 51, ended up with 4 to try out:

Standard spring guide/top hat: 37grams.



Slightly reduced to 29 grams:



To 24 grams:



To 21grams:



Really did not want to increase the spring force needed to cock the rifle, which means I’d NOT try the really light weight (Delrin) spring guides with a standard valve. I HAVE TRIED THWEM in the past, but to get the velocity up, need to increase the striker spring tension, which translates into stiffer cocking.  Wasn’t willing to increase cocking effort, so wasn’t willing to try the super light weight strikers.  If I get to modding the valve, will try the lighter weights.


Shot count with the heaviest modded spring guide/top hat (29grams):



As expected, the upper sweet spot fill pressure was a little lower.  The energy was a little lower.  The shot count was a little less but the efficiency is pretty good.

There might be a longish time before another BAM 50 post.  It’s pretty much were I wanted it to be (for tight now, will just fill to 160BAR, shoot 30 shots, and refill to 160BAR...likely to stay inside of 3% velocity variation that way).

[caniborrowsomeammo]

I picked one up, shoots too good to tear it apart yet. My fill range starts at 2525# shooting the heavy Crosmans. 
Did you heat the trigger up to reshape it? My trigger feels nasty as only the tip of my finger is touching.

[nervoustrigger]

Robert said or implied that he just bent it cold (could repair with silver solder). 

When I straightened mine, I heated it with one of the little butane torches that uses a cigarette lighter as the fuel cell, and that worked out great.  I probably could have repaired it if it had broken but it would have been painful so I figured annealing it a bit first was worth it.

[SpiralGroove]

Hey Ribbonstone,
I bent the trigger using two pieces of pine in a metal vise (w/no heat).  Because the pine is very forgiving, the trigger never gets bent too much at a time or in one place along the curve.

Unless you change out the ridiculously heavy, valve spring, you're pretty much stuck with using the OEM spring (cut).  Once the valve spring is changed to a Hillman #83 (medium) or a Hillman #86 (light) everything else related to hammer strike can be reduced.  You can go with OEM Hammer/spring guide with Hillman #152/#83 or MC; delrin hammer/spring guide with Hillman #152/#86 or MC.  Then to get everything just right, you tinker..................maybe a lot

If you don't want to change out or cut the OEM valve spring, you cannot reduced cocking force too much (F = M x A).

[nervoustrigger]

Kirk, I was looking for the Hillman #86 conical spring and it seems about as rare as hen's teeth!  Google pretty much brings up Hillman's site, your thread, and an Ace Hardware in WI that will ship one across the country to me for a $20 bill

Where are you getting them?  We don't have a local Ace unfortunately.  The big Lowe's nearby carries a tiny selection of Hillman springs but no conicals of any kind.  I guess I should have asked while I was in there if they would special order it but I expect it would be crazy expensive if they would do it at all.

I think I'll have a look at McMaster tonight and see if they have something comparable.

[SpiralGroove]

Hey Jason,
You have been a very valuable resource on the GTA
I would be more than happy to buy a few springs and ship to you -> just let me know.
Looking at my last receipt, they are only $1.92 each for the #83, #86 & #152; and because they weigh almost nothing, shipping shouldn't be outrageous.
Kirk

[nervoustrigger]

Kirk, thank you very much for your generous offer.  I may take you up on it after my buddy checks his local store.

[bubba zanetti]

The stock trigger shape is just awful. Straightening it out is a good, simple mod.

BZ

[Ribbonstone]

On the first one (.22 BAM 51) did take the time to remove the trigger, anneal it, and shape it by pressing it in a vice between two formed/shaped hard wood blocks.  Basically just pressed it between two wooden dies to form the shape.

On the new one  (.177 BAM 50) just used padded pliers and carefully cold formed it to shape. 



It BAM 51’s did come out a little nicer shape, but it’s pretty close.



Always a chance that the brass will just snap, it’s not like it’s made to any real specifications and brass always has the potential for hidden imperfections.

[nervoustrigger]

Hi Kirk,

We struck out today so I dropped you a PM. 

[caniborrowsomeammo]

Ribbonstone, I think I will heat mine up, just to be on the safe side.  After seeing your 51, kinda makes me wish I would have got one too.
Spiralgroove, would you mind if I took you up on that offer? Been reading "The Book" will get into the gun when the poppet takes a dump.

[Ribbonstone]

Brass anneals differently than steel.  To soften brass, heat it and quench it.  That’s a process that will HARDEN steel, but with brass it softens it.

How hot? 

Have played with annealing brass cases, jewelry,  inlays, etc. but am still not real fond of giving advice about it.  The part does NOT look to be cast, it LOOKS like it was made from sheet brass,  That’s a good thing, as cast brass will break more times than it will bend no matter what you do.

Are ways to measure the temperature, and probably  is a perfect temperature (if we knew just what the alloy was…which we don’t). Propane torch for this job, just heat the blade part of the trigger until it just starts to change color, drop the trigger in water,  and you should be OK.

Will be a bit discolored, but will polish back to bright.

[bubba zanetti]

Brass anneals differently than steel.  To soften brass, heat it and quench it.  That’s a process that will HARDEN steel, but with brass it softens it.

How hot? 

Have played with annealing brass cases, jewelry,  inlays, etc. but am still not real fond of giving advice about it.  The part does NOT look to be cast, it LOOKS like it was made from sheet brass,  That’s a good thing, as cast brass will break more times than it will bend no matter what you do.

Are ways to measure the temperature, and probably  is a perfect temperature (if we knew just what the alloy was…which we don’t). Propane torch for this job, just heat the blade part of the trigger until it just starts to change color, drop the trigger in water,  and you should be OK.

Will be a bit discolored, but will polish back to bright.

Ribbon:

Pretty much the method I used. I straightened it and cut it shorter trying to mimic a M-Rod trigger. I am pretty happy with the results and it was surprisingly simple to do.

BZ

[rsterne]

Yep, you quench brass to anneal it, the opposite of steel.... That's what I did before I straightened mine....

Bob

[Motorhead]

I simply reshape them by heating with a propane torch until 'Straw' color then lightly hammer against a round pipe of desired radius.  Let it cool down naturally so temper remains the same.