Constant POI change?
Select Gate
READ GTA FORUM RULES BEFORE POSTING
GTA Forum Help Desk
GTA Announcement Gate
Dealer Area
GRIP
AirgunWeb Airgun Videos
Airgun Repository of Knowledge
Vendors and Vendor Videos
AirGun Expo 2021
Airgun Expo 2022
Contests and Giveaways!!!
Welcome New Members
In Memoriam
GTA Contributing Members
Shot Show Videos
Hajimoto Productions
Airgun Detectives
Air Gun Gate
BB Guns and Such
"Bob and Lloyds Workshop"
American/U.S. Air Gun Gates
European/Asian Air Gun Gates
PCP/CO2/HPA Air Gun Gates "The Darkside"
Air Archery
Vintage Air Gun Gate
Air Guns And Related Accessories Review Gates
Hunting Gate
Machine Shop Talk & AG Parts Machining
3D printing and files
Buyer's, Seller's & Trader's Comments
Bargain Gate
Back Room
Target Shooting Discussion Gate
Target Match Rules
Shooting Match Gates
Field Target Gates
The Long Range Club
100 Yard Match
Discussions By States
Welcome,
Guest
. Please
login
or
register
.
Did you miss your
activation email
?
1 Hour
1 Day
1 Week
1 Month
Forever
Login with username, password and session length
Home
About
Help
Old GTA
Gallery
Search
Stats
Login
Register
Advertise Here
GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
European/Asian Air Gun Gates
»
Gamo & Spanish AirGun Gate
(Moderator:
Tpatner412
) »
Constant POI change?
« previous
next »
Print
Pages: [
1
]
Go Down
Share This!
Author
Topic: Constant POI change? (Read 9455 times))
1shotwonder
Guest
Constant POI change?
«
on:
July 16, 2010, 12:13:52 PM »
What could be causing a constant POI change? 1 day i'll shoot the gun.. resight the POI in, it'll shoot fine for the rest of the day....But the day after it'll have another POI... I dont think that it's the spring as the POI wouldn't be constant for the rest of the day would it?
A little about my gun... It's a BigCat.. It's got 5000 CPHP's though it... About 10 or so PBA's and prolly around 30 or so of my 11.6 grain 'custom' pellets... Which consist of 1 lead birdshot glued in the hp cup of the CPHP... Yes i know that 11.6grains isn't the best for the spring,
«
Last Edit: July 16, 2010, 12:16:27 PM by 1shotwonder
»
Logged
Cptjbud
Guest
Re: Constant POI change?
«
Reply #1 on:
July 16, 2010, 12:25:48 PM »
Well if you have 5000 rounds through it, I'm sure you've probably learned to make sure all the screws are tight. Are the outside temps / pressures changing drastically on a day to day basis? Are the different types of pellets all giving you the same inconsistencies? If it's just the custom pellets, I'd say that the extra weight on the nose of the things are throwing off the ballistics, or maybe the amount of glue isn't the same, or that some of it is hardening outside of the hollow point throwing the shape out of whack.. I'm sure others will chime in.
Logged
RedFeather
GTA Senior Contributor
Posts: 4741
Re: Constant POI change?
«
Reply #2 on:
July 16, 2010, 12:29:27 PM »
Might want to check your stock screws, although loose screws likely would not shoot well the rest of the day. You adding anything such as chamber lubes, etc? Only ask since you seem to like to fiddle with fodder. (You know, I thought about gluing a BB to a hollowed out wadcutter years ago. Look at all the money Gamo has made on that one!)
(Bodjie, you beat me to it, LOL!)
Logged
1shotwonder
Guest
Re: Constant POI change?
«
Reply #3 on:
July 16, 2010, 06:04:59 PM »
Yup, all the stock screws are tight... Nope haven't fiddled with the gun any.. everythings still stock.. I know that the mainspring is going, but i dont think that would lead to the inconsisancy... I think that every shot would be effected differently
Nope the day to day outside temps aren't changing that much... Mostly all in the high 80's to mid 90's.. Gun stays out in the shop, so it's constantly in those temps.. It stays out of the sun..
The cphp's will shoot just about the same spot at 10 yards after it gets dialed in for the rest of the day... same goes for the one's with the lead shot infront.. the next day both types of pellets will be shooting a different POI... redial the scope in and it's all good for the rest of the day
Logged
GamoHunter
Guest
Re: Constant POI change?
«
Reply #4 on:
July 16, 2010, 06:47:37 PM »
Are the scope screws tight?
Logged
vadalejrfan
Big fan of NASCAR and Dale Earnhardt jr.
Plinker
Posts: 235
My Grandson-future airgunner
Real Name: Don
Re: Constant POI change?
«
Reply #5 on:
July 16, 2010, 08:37:01 PM »
I had the same kind of trouble with my Hunter Sport, but I just did a lube tune and added polished SS washers at the spring ends and polished the spring ends and problem solved, amazingly more consistent and accurate. Good luck
Logged
Mathias WVa
Crosman 760 .177
Bam B3-3 .177
Crosman 1077 .177
QB-78 Deluxe TH .22
Hatsan 125 TH .22
Bam B-50 .177
Benjermin Marauder .22
Career III Single tube .22
Career Ultra 9mm
Crosman 2240 .22
Hatsan 125TH .22
Davee1
Plinker
Posts: 128
Re: Constant POI change?
«
Reply #6 on:
July 16, 2010, 10:04:50 PM »
Here's a general list of things to check, but not necessarily in this order...do the easiest first. Sometimes its just a process of elimination.
Maybe the piston seal has some nicks or cuts in it from the factory installation...which is quite common. That causes variations in the velocity/consistency and can even affect the way it jumps in your hold. Same with the factory spring, which gradually gets a bend in it, and/or breaks too...causing erratic behavior.
Replace the breech seal or shim it. Do you have a chrony? Check the side to side, and up/down movement of the barrel at the forks. There shouldnt be any play there.
Then there's scope issues....which you can rule out by putting on a known good scope, or using open sights, but that model doesnt come with open sights. If its the factory scope, I would highly suspect that it may have gone bad on you.
The mount(s) may be moving too.
Next, I would evaluate your hold(s). I've encountered similar problems, and it turns out that one day I was resting the stock on a chair and getting one holers or close to it. Then the next day time I would lean against a pole, shoot standing up, or cradle the stock in a fork made with my fingers against a post...and the POI was off. Adjust the scope a little, and next day I'd go back to my chair and the POI was off again. Drove me crazy. Springers are like that. They are highly affected by the type of hold that is used.
I cant remember if you said you were using the same type of pellet each time. Different types of pellets have different POIs, although you may find some types that are close enough not to adjust your scope.
Logged
Gamos all with GRTIII trigger... Whisper.22, Shadow1K.177, CFX.22/177, ShadowExpress.22/shotshell, a .177 Bone Collector with the new plastic trigger(not worthy), Diana 350M.177/22, P5.177, LP8.177, HammerliX2.177/22, Storm22, Chinese B3.177, B3AK47.22, B4.22, B21.22, Beeman1073SwitchBarrel.177/22, P1.177, P3.177, P17.177, Browning B800.177/22, Crosman1377, Benji HB22, Marauder.22/25.
gamo2hammerli
GTA Moderator
GTA Senior Contributor
Posts: 6322
Re: Constant POI change?
«
Reply #7 on:
July 16, 2010, 10:17:57 PM »
How do you rest/place the rifle after a day's shooting? Sometimes resting it on one side or standing on it's butt (Different than when you're shooting) can affect the spring in the scope.
Logged
Airguns Forever
2013 Starling count: 13, Grackel count: 02
2012 Starling count: 16, Grackel count: 01, Mouse count: 3
2011 Starling count: 38
RedFeather
GTA Senior Contributor
Posts: 4741
Re: Constant POI change?
«
Reply #8 on:
July 16, 2010, 10:43:08 PM »
My guess, too. Everything else should make the gun shoot inconsistently rather than go to and hold a new zero. This almost sounds like what they used to talk about with rimfire semi-auto pistols where the first shot goes off but the remainder shoot to the same poi. In that case, it has been argued that the powder, springs, etc, are forced to a new resting position by the recoil of the first round. Maybe something similar is happening with your gun? At least you can be thankful that it does hold a new zero. As such, I wouldn't worry about it too much. And, you know, the shot cycle of a magnum springer does heat up the first few shots since those combust the lube fumes (normal according to Cardew).
Logged
1shotwonder
Guest
Re: Constant POI change?
«
Reply #9 on:
July 17, 2010, 02:17:19 AM »
I was thinking of cracking it open once and checking out how the main spring and such looks... It's not like it's a major problem, but it's just kinda annoying if i see a squirrel or such in the yard... i just cant take the gun out and take care of the problem, i gotta let the problem go.. grab the gun, go down stairs and see what the new days POI is, than it's game on...
I usually just keep the gun either on its butt or laying on the right side
Logged
Rocker1
Administrator
GTA Senior Contributor
Posts: 4764
Executive administrator
Real Name: David
Re: Constant POI change?
«
Reply #10 on:
July 19, 2010, 07:00:24 AM »
I agree with fltom, thats a heavy pellet to be shooting in that type of springer, 5000 rounds thats a lot you may have spring or seal problems if its not the scope........... thanks david
Logged
Fruitland Park, Florida
1ST CAV,1971 VIETNAM 11 BUSHBABY LRRP
I MISS MY FRIEND GENE
OLD GUYS PLAYING WITH BB GUNS NEVER GROW UP
lots parts and pieces for something
CZ200 Hunter 22 unbeatable
disco 22 with the works
Disco 22 fine gift from a special friend
FX CROWN 22 AND 30 , 25 caliber
bsa Lonestar 25
Gamo swarm magnum 22
B40 177
avenger 22
Liberty 22
HotRod Prod 22
RWS 350 MAG
Rws 45 177
rws 36 22
rws 34 22
Gamo extreme 22
Rocker1 tuning and custom works
davidjfurr@outlook.com
RedFeather
GTA Senior Contributor
Posts: 4741
Re: Constant POI change?
«
Reply #11 on:
July 19, 2010, 12:05:34 PM »
I should think the scope is OK. If it were shot, you wouldn't be able to hold a zero for the rest of the day. If you are shooting heavy pellets, you are putting quite a bit of stress on the gun with that first shot. This wears out the spring more quickly. Might be you have a broken spring that is rebinding enough to settle in after the first shot forces it back together. Have you tried zeroing the gun, then letting it stand for a couple of hours to see if it holds? That would allow any parts expanded from the heat of shooting to cool and contract.
Logged
454 Big Block Chevy
454 BBC///Edward
GTA Senior Contributor
Posts: 2547
Real Name: Edward
Re: Constant POI change?
«
Reply #12 on:
July 19, 2010, 07:19:26 PM »
IF, you are still using the gamo scope that came with it, that is your problem. i was having the exact same problem... over 3k-5k shots through my bc, factory 1 piece scope mount, and factory 3-9x gamo scope. its deadly accurate, but would randomly change POI, sometimes in the middle of a shooting session, yet would hold the POI for 40-50 shots, then change. replace the scope.
Logged
Center township PA(North West of Pittsburgh about 30 miles)
FX Impact X MKII .25 ////700mm 25.4 JSB Kings @ 925 FPS, 75+ shots. Tuned by Tony at Talon Tunes
USAF VET SSGT, 10 YEARS, AFGHANISTAN CAMPAIGN MEDAL
RedFeather
GTA Senior Contributor
Posts: 4741
Re: Constant POI change?
«
Reply #13 on:
July 19, 2010, 11:32:53 PM »
One other possibility I will throw out here. Seen some posts about the barrel lockup on these guns with the plastic breech block - where the barrel is inserted. Is yours steel or plastic? Apparently, some of the guns suffer fatigue here and end up with inconsistent lockup. That can certainly throw things off. Could be, once you've shot it, it locks up the same for the rest of the session, then settles back a bit off when the gun is put away.
Logged
Big_Bill
Guest
Re: Constant POI change?
«
Reply #14 on:
July 23, 2010, 01:20:50 AM »
When everything else is OK,
Then it may be time to give your air rifle a good cleaning, and re-season the barrel ?
Otherwise it may be you, I know that I need 10+ rounds to get into my normal routine !
Bill
Logged
Print
Pages: [
1
]
Go Up
« previous
next »
GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
European/Asian Air Gun Gates
»
Gamo & Spanish AirGun Gate
(Moderator:
Tpatner412
) »
Constant POI change?