My late model 880 as stated earlier is highly modified; straw barrel encased inside of an arrow bolt, front sight altered to accept the added diameter of the arrow bolt, bolt & straw barrel cushioned above lever arm pivot point, plastic receiver clam shells bolted in place, added weight to both stock & forearm grip clam shells, & highly modified the trigger & sear. With all this said I recommend you only modify the trigger & sear & add weight to the forearm grip & stock. These are the only mods I will explain at this time & here’s why; the stock trigger assembly is atrocious & there is no weight to speak of to help balance the gun. There is no way you can group shots consistently with these two factors alone. Once you’ve addressed these two issues, & I say this with the utmost respect; learn how to shoot your guns.That last comment is a tough pill to swallow as it was for me. I knew all there was to shooting guns & no one was going to tell me otherwise. It wasn’t until I spent time over at the “Shooting Match Gates” that I realized I didn’t have a clue the skills necessary to achieve the results l was hoping for. I was dumb founded as to how those members could knock down bulls the size of their pellets day after day like they were the size of dimes. It took a lot of time at the range to finally piece it together. My recommendation at this point is to read the information on this link (https://www.gatewaytoairguns.org/GTA/index.php?topic=140500.0) & spend a lot of time on the range putting each step into practice until it becomes routine. To barrow a phrase from a wise man; "until you master these steps you'll be spittin in the wind". My apologies if I've offended anyone but I have never been one to tip toe through the tulips. In the mean time I’ll gather up those two mods which are scattered everywhere in this gate & post them here.
Work has been driving me nuts, so I have not had a chance to do anything 880 related.
Thanks for that. It's good stuff. The day I stop reading, stop seeking advice from those who know more than I, start thinking I know all I need to know, is the day I becoming a closed minded dingle-berry.
Work has been driving me nuts, so I have not had a chance to do anything 880 related. I very well may try to pull the rivet that I have in place of the factory probe and install a longer one to see if my velocity issue was probe length related by not pushing the pellet totally past the TP, thus causing pellet interference with the air.
Quote from: wll2506 on January 08, 2019, 10:20:46 PMWork has been driving me nuts, so I have not had a chance to do anything 880 related. I very well may try to pull the rivet that I have in place of the factory probe and install a longer one to see if my velocity issue was probe length related by not pushing the pellet totally past the TP, thus causing pellet interference with the air.For testing this just use a bent piece of wire to push the pellet in a little further. That way if the probe length isn't the problem you can leave it be.
Cobalt, I will do this tomorrow and report back !wll
Quote from: wll2506 on January 09, 2019, 09:55:52 PMCobalt, I will do this tomorrow and report back !wllOkay, I'm interested in knowing. If that's not the problem hopefully it'll be something relatively easy to cure.
Quote from: cobalt327 on January 09, 2019, 11:17:55 PMQuote from: wll2506 on January 09, 2019, 09:55:52 PMCobalt, I will do this tomorrow and report back !wllOkay, I'm interested in knowing. If that's not the problem hopefully it'll be something relatively easy to cure.Lengthened the probe by another .085 and it made a difference of 20 fps with the 540fps gun ... so now I'm getting 560fps ... great ?I'm going to put a shim under the hammer valve area to get more lift on the valve.. I ordered some .030 and .040 shim material, should get that tomorrow >wll
Quote from: wll2506 on January 10, 2019, 01:08:10 PMQuote from: cobalt327 on January 09, 2019, 11:17:55 PMQuote from: wll2506 on January 09, 2019, 09:55:52 PMCobalt, I will do this tomorrow and report back !wllOkay, I'm interested in knowing. If that's not the problem hopefully it'll be something relatively easy to cure.Lengthened the probe by another .085 and it made a difference of 20 fps with the 540fps gun ... so now I'm getting 560fps ... great ?I'm going to put a shim under the hammer valve area to get more lift on the valve.. I ordered some .030 and .040 shim material, should get that tomorrow >wllIs this the same gun that you were getting 580-590 fps from w/10.5 gr ammo? If it is, there might be something else going on because changing the probe shouldn't cost you any power as long as the TP isn't blocked. I seem to remember you mentioning bolt O-rings but cannot recall what was said, but have you tried the tissue/talc test to see if it's blowing back at the bolt?Anyway, just a thought and good luck.
Quote from: cobalt327 on January 10, 2019, 07:20:49 PMIs this the same gun that you were getting 580-590 fps from w/10.5 gr ammo? If it is, there might be something else going on because changing the probe shouldn't cost you any power as long as the TP isn't blocked. I seem to remember you mentioning bolt O-rings but cannot recall what was said, but have you tried the tissue/talc test to see if it's blowing back at the bolt?Anyway, just a thought and good luck.Yes it is, Since I changed the probe things went south with this gun. I will do a powder check tomorrow, although I did a toilet paper check and did not see air blow by ... except ... I felt it on the underside of the gun ?I did not buy any small bolt "O" rings today as I was waiting for my graphics guy to tell me if he needed any "O" rings for our Roland printer. I will buy the rings tomorrow "Heck or High Water !!!"He made some PETG slit washers for the hammer to lift the valve higher. I used A blister pack plastic of .025 thickness .... I ordered .030 and .040 from McMaster Carr today !! I will probably use the .040 thickness, as all my measurements indicate that thickness will work. A .04 higher lift SHOULD let a lot more air past the valve head and into the TP quicker, equating to higher velocity ----- We will see !wll
Is this the same gun that you were getting 580-590 fps from w/10.5 gr ammo? If it is, there might be something else going on because changing the probe shouldn't cost you any power as long as the TP isn't blocked. I seem to remember you mentioning bolt O-rings but cannot recall what was said, but have you tried the tissue/talc test to see if it's blowing back at the bolt?Anyway, just a thought and good luck.
Quote from: wll2506 on January 10, 2019, 09:35:45 PMQuote from: cobalt327 on January 10, 2019, 07:20:49 PMIs this the same gun that you were getting 580-590 fps from w/10.5 gr ammo? If it is, there might be something else going on because changing the probe shouldn't cost you any power as long as the TP isn't blocked. I seem to remember you mentioning bolt O-rings but cannot recall what was said, but have you tried the tissue/talc test to see if it's blowing back at the bolt?Anyway, just a thought and good luck.If this was a brass compression tube gun I'd suspect the barrel had gotten turned a little causing the TP to not be in perfect alignment w/the valve body but that's not a problem w/the aluminum tube guns.Are you going to do the high lift mod before you sort out the power being a little off? Really doesn't matter that much either way, in the bigger picture as long as you get the power where you want it, it's all good anyway!
Quote from: cobalt327 on January 10, 2019, 07:20:49 PMIs this the same gun that you were getting 580-590 fps from w/10.5 gr ammo? If it is, there might be something else going on because changing the probe shouldn't cost you any power as long as the TP isn't blocked. I seem to remember you mentioning bolt O-rings but cannot recall what was said, but have you tried the tissue/talc test to see if it's blowing back at the bolt?Anyway, just a thought and good luck.
Quote from: cobalt327 on January 10, 2019, 10:21:24 PMQuote from: wll2506 on January 10, 2019, 09:35:45 PMQuote from: cobalt327 on January 10, 2019, 07:20:49 PMIs this the same gun that you were getting 580-590 fps from w/10.5 gr ammo? If it is, there might be something else going on because changing the probe shouldn't cost you any power as long as the TP isn't blocked. I seem to remember you mentioning bolt O-rings but cannot recall what was said, but have you tried the tissue/talc test to see if it's blowing back at the bolt?Anyway, just a thought and good luck.If this was a brass compression tube gun I'd suspect the barrel had gotten turned a little causing the TP to not be in perfect alignment w/the valve body but that's not a problem w/the aluminum tube guns.Are you going to do the high lift mod before you sort out the power being a little off? Really doesn't matter that much either way, in the bigger picture as long as you get the power where you want it, it's all good anyway!Bought the "O" rings a few hours ago and will give that a shot when they come in. He made a few split ring washers of .025 so i may try those. Will do a powder test tomorrow for sure. The only other thing I wonder is, this gun I believe has an old style flat piston .. I wonder if I should install a new piston and fill with JB Weld. I measured piston length before and they seemed to be the same, but this was a US made gun as I remember ?wll
Well velocity is staying the same even with a .060 shim under the hammer spring. I put a .025 shim under the poppet valve and that made no difference in velocity, this gun is a problem child.Here are my readings on the Black 880 using 10.5 gr Crosman Premier Heavies.:9 pumps - 562 fps10 pumps - 581 fps12 pumps - 607 fps (I never do 12 pumps, but with this gun I don't feel it pumping hard !)I will work on the Brown 880 tomorrow by adding a .060 washer under the hammer spring and a .025 shim under the valve poppet !See you tomorrow (If I can wait that long) ;- )wll
Good deal. Now, is this with the "short" finishing nail probe or has any of that been changed?
Quote from: cobalt327 on January 11, 2019, 07:46:11 PMGood deal. Now, is this with the "short" finishing nail probe or has any of that been changed?I used a 3/32 rivet and have a probe length of about .285. It shuts off the BB port but it actually makes loading easier as the thin probe is used as a guide. Loading lead balls is very, very fast also.Will chronicle lead balls and report back after I do testing at work tomorrow.I will decide on what velocity I will use for the lead ball based on a ~ 15 yard range.We will see tomorrow !wll