Retained air-2100-13-XX conversion

[vAgRaNt]

. . . ten pumps for an average of 747.9 fps. . . . . 4 pumps. . avg 564.8. . . . . . Crusty B's. Anyone remember . . . . . .

Very respectable #'s! Good output for reasonable input = Nice Job!

The more substantial 2100 forearm, almost balances out the Galaxyfinder mounted on top. . . .


Still surprised Usti' hasn't found his way back here yet . . . .

[Doc Sharptail]

Hiya, Vagrant.

Yeah, the old 6-24X 42mm Banner looks interstellar. I have 2, and I think the older one is close to 20. Both still going strong....

I think I'll be able to try the p-rod trigger group soon- put a disco spring into the gun last night, and found things much improved. The disco spring is a bit longer than the cut down 2100 spring. There's some slight pre-load on the same rodless RVA now. Will clock it again tonight, and take it from there... Gun's much easier to cock now, and the "grind" has gone from the sear. We shall see....

I badly want to bench this thing with some 8.2 gr. R-10's at 4 pumps.

-D.S.

[Doc Sharptail]

Hmmph.

With the disco hammer spring in it, it now takes 5 pumps for low 560's.

Can't quite figure this out, because at 4 and 5 pumps, the RVA has no effect on velocity at all- full in, or completely out. It was the same story with the cut down 2100 spring. Wonder what the heck's going on...

Back to the chrony- more in a while....

Couldn't stand the suspense any longer...



Rusty on the bench Get days like that though. Am pleased over-all.

Only thing I can come up with is temperature- it was 24 C in the shop last night. Tonight, 18 C. Either that, or my o-ring spacer on the valve rear let go. Haven't cranked the new hammer spring for max yet- that can wait. Just had to get that bench bee outta my bonnet

Had to remove the bbl bushing in the pivot cover- it was pushing the bore up so high the scope couldn't correct for it. IIRC, that scope will subtend 86" at 100...

-D.S.

[Doc Sharptail]

Only thing I can come up with is the disco spring has slowed the hammer down somehow. I remember reading here somewhere that .177 likes a short rapid pulse at hammer strike for a pumper.

I'm not changing that hammer spring out yet. I think I'm probably going to find differences in the way the gun handles retained air now.


-D.S.

[wesb2007]

Hi Doc, anything new on your 2100? Were you able to get it balanced for a couple good shots?

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[Doc Sharptail]

Will try and get over the chrony tonight. Dunno if I'll get as far as balancing retained air shots tonight. Do want to see where it top ends, and see where I am at ten pumps. Gonna switch to the 7.9 gr. milk carton points for test fodder, so there may be a shade more zip there... kinda wiped from work.

-D.S.

[wesb2007]

For sure, sounds good!

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[Doc Sharptail]

Got the velocity drop cause- that little XX hammer pin bent.

I should have seen this coming- it's not the first, second or even third time this has happened to me. Those drop in pins simply cannot withstand heavy pre-load of any kind....

I did run some numbers, before I realized what was happening. Top end occurs between 20 and 25 pumps, with a difference of only 20 fps. Still not bad, even with the bent pin- 875 at 20, and 895 at 25.

There's only one way to solve this~ Get my home made hammer in there with hardened motor key set screw hammer pin and P-rod grip frame and trigger. Hammers a bit heavier than the normal 13-XX too, so will get a look at it tomorrow night...

-D.S.

[wesb2007]

Great numbers!! Well, that'll be interesting how the new hammer changes things!

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[rsterne]

Pretty decent, Doc.... My Uber-Pumper did 912 fps (7.8 gr.) @ 20 pumps, 938 @ 25, and 950 @ 30, where it was just starting to retain air with the 2200 spring....

Bob

[Doc Sharptail]

Pretty decent, Doc.... My Uber-Pumper did 912 fps (7.8 gr.) @ 20 pumps, 938 @ 25, and 950 @ 30, where it was just starting to retain air with the 2200 spring....

Bob

I don't have quite your swept volume- difference in our builds. Surprising how close, though.

The more I think about it, the more I wonder if it's worth it to agonize over those extra 25-40 f.p.s.
Certainly not a life or death situation for me, but I'm fortunate~ almost enough to be called a fortunate son, but not quite

-D.S.

[rsterne]

In reality, ask yourself how often you will pump to 20 pumps....

I most often use mine at 3 pumps (~500+ fps), or at 10 pumps (~800 fps).... and rarely anything else....

Bob

[Doc Sharptail]

I hunt often with lightly modded 13-XX's in .22. I usually see mid 6's for 15 pumps, which isn't that much of a bother.
To be honest, the grouse I shoot at my self-imposed distance limits can't tell the difference between 650 and 950....

Got the drop-in XX pin out of the gun. There's a good 12 degree bend to it

Just for chuckles, tried the 2100 hammer in behind the disco spring. At ten pumps, with the RVA in all the way and adjuster nut off, 2 equal sounding shots, and a 3rd little braaap. Didn't bother to clock, but filed for future reference That 2100 hammer has a shorter stroke, and is a bit lighter than a 13-XX hammer....

Got the home made hammer into the gun. Way easier to cock and drop the sear now. No retained air until 20 pumps, with the RVA completely out of the gun. Time to chrony!

-D.S.

[Doc Sharptail]

I lost 20-30 fps at the top end with the heavier hammer~ not enough stroke in that set-up to take advantage of the extra weight.

Rest of it is a carbon copy of previous performance: within - or + 5-10 fps from 3 to 15 pumps.

I do need to mirror polish the tube hammer slot edges. That collar on the bent XX hammer pin created a few rough patches- nothing major, though.

I think I'll let her sit with that hammer for a while. I actually like the handling. Still on the XX grip frame. Just want to make sure everything's proper and consistent before I go to the P-rod grip.

That 2100 hammer looks promising for finding 2 balanced shots. By the sound of it, they'll likely be low 500's, which could be interesting for all the indoor plinking I do.

Probably take a couple days break from it. Got a pistola to shop for, and the time away from the project will sharpen my mind a bit.

-D.S.

[wesb2007]

Great work! Will be great to hear what numbers you get on two shots whenever you get back working on it again.
I was wondering if you did any work on the valve at all for more volume, or the transfer port? Wondering if I should do anything on my 760 gun valve and Tp or not.

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