point of impact drops in 15 to 20 shots

[dannej]

Hi,
I have an air arms 510 and shoot benchrest with it. Starting with a full charge, I fine tune the scope with about five shots before I start the 25 shot competition. Somewhat consistantly the point of impact drops rather quickly, like anywhere between 15 to 20 shots. I thought this rifle was not supposed to do that, that I should get about 40 or more shots before it became a problem. The power is set at about 1/4 of full power which is the most accurate setting. The gauge when full shows just over 150 and can not be filled any higher. Is there something wrong with the rifle or is this just the way it works?

[Blackbaronfish]

What distance are you shooting at ?

BBF

[Timmytree]

Hi,
I have an air arms 510 and shoot benchrest with it. Starting with a full charge, I fine tune the scope with about five shots before I start the 25 shot competition. Somewhat consistantly the point of impact drops rather quickly, like anywhere between 15 to 20 shots. I thought this rifle was not supposed to do that, that I should get about 40 or more shots before it became a problem. The power is set at about 1/4 of full power which is the most accurate setting. The gauge when full shows just over 150 and can not be filled any higher. Is there something wrong with the rifle or is this just the way it works?

If you're only getting 150 bar in that may be part of the problem.

[dannej]

I am shooting at 25 yards.

[eddie666]

the more you shoot the hotter things get and will expand and compress ,some parts will start to move faster some parts will move slower.

with multi shot rifles its easy to fire 10 after 10 after 10 shots with out letting your rifle to cool down, if there is some thing week or about to fail it may show up now and then when things are warming up,

[gary martin]

Hi,
I have an air arms 510 and shoot benchrest with it. Starting with a full charge, I fine tune the scope with about five shots before I start the 25 shot competition. Somewhat consistantly the point of impact drops rather quickly, like anywhere between 15 to 20 shots. I thought this rifle was not supposed to do that, that I should get about 40 or more shots before it became a problem. The power is set at about 1/4 of full power which is the most accurate setting. The gauge when full shows just over 150 and can not be filled any higher. Is there something wrong with the rifle or is this just the way it works?

is it a sub12 ft/lbs rifle or an fac tuned to 1/4 power? 150bar max! my old s400 sweet spot was approx 170-140 bar.

[Mark112]

Hi,

My old S400 Classic .177 would give 60+ shots within a spread of +/- 6fps at its sweet spot. At 50 yards this equates to +/- 0.13" and at 25 yards this equates to +/- 0.03" or in metric terms about 1.5mm total difference (commonly called bugger all!). At 25 yards you should be able to get 80 shots with no real discernable drop in POI (20fps sweet spot). If you are shooting a carbine this quantities with be 2/3rds of mine i.e 40 shots within 12fps and 60 within 20fps. The valve arrangements are the same .... only the magazine loading differs between any of the S4/S5 series. I also shoot my S410 in rapid fire mode often and have suffered no drop in POI during this type of shooting. The rifle wont get hot in fact when you fire a shot the drop in pressure of the air pushing the pellet will cause a drop in temperature in the valve.

I don't know if you are shooting an FAC S510 and maybe it's wasting a lot of air. A full shot string may give you an idea of the power curve of your own individual rifle.

Mark

[Pav]

How old is the rifle and how long since you had it serviced? I had a similar problem with my S510 with point of impact dropping after about 20 shots or so from a full 190bar charge. This began immediately following a service and a telephone conversation with Julian (bgaltd) eliminated all the possible causes apart from the exhaust valve. The problem was indeed the exhaust valve which had a deformed seat and replacing it cured the problem. In my particular case the face that the exhaust valve contacts within the firing valve body was also damaged, so that required replacing also. It has not missed a beat since, me however, that's a different matter.

Here is a link to a thread that shows the deformed valve alongside a new one, with the publisher explaining how he came to discover the problem.
http://www.airgunforum.co.uk/forums/sho ... ring+valve

If you are charging from a cylinder, does this need re-filling? If the charge in the bottle is low, then this could explain why you are not getting more of a charge into the rifle.

All the best
Pav