Fps V Pellet Weight = ? Legal?

[Cedric 132]

Is it sensible to assume that a heavier pellet will generate a lower fps speed ?

 

My .177 HW99 showed 740fps with an 8.4g pellet (= 10.2ftlbs). A quick calculation showed that, at the same speed a 10g pellet would take it over the legal limit to 12.2 ftlbs. Is it likely that the heavier pellet would slow the speed, keeping it under the limit?

 

My concern is that if I raise the power to acheive 11.3ftlbs with my 8.4 g pellets it would only take a 9g pellet to put it over the limit.

 

I'm just theorising at the moment and could do with a chrono for accurate testing.

 

In the unlikely event of my rifle being tested by the police does anyone know how they go about it - use a standard weight pellet etc. as it seems to me the weight could have a considerable effect on the results.

 

On another point, do the police have the powers to seize any air rifle for testing even if there are no grounds to suspect that the weapon might be overpowered ?

[Rez 4,961]

This is an interesting point.... Funnily enough Ive recently thought this with a v-mach mod going into my 98. With H&NFTT, its registering a nice 11.4-11.6, however a lighter pellet may take it over the top. Rifles that are set closer to the limited may easily be over 12 on another diet of lighter pellet, referring to spring rifles here. What is the situation with these? Some pellets legal, some others it may not be.

 

Im thinking about swapping my pellet to the heavier Barracudas, just for this reason, but wondered what others thought. Is it a legal rifle, based on one diet of pellet, an illegal one based on another. Surely, with most air weapons set around the 11 to 11 1/2 mark, and with such a varied selection of ammo to choose from, any rifle could be over the limit depending on the pellet thats put through it...

 

But yes, it is right to assume the heavier pellet with lower the fps speed, with spring rifles.

Edited May 30, 2014 by Rez

[barrywhite 282]

pellet weight is not the only factor some pellets could be a tight fit in the barrel giving a lower power .test a spring gun with different medium to light weight pellets test a pcp with medium to heavy pellets at least .all shots must be under 12 ft lbs .

[Skot Ruthless Teale 1,701]

I think .177 flying at averages of 700-800 and .22s going at only 500-600 shows that heavier pellets go slower

 

Test same gun with 11.9 hobby 14.3 accupel and 16 aa fields and then 20 ish grain bisley mags and see the differences mate.

 

I would if my chrono wasnt annoying to set up lol

[treecreeper 1,136]

don't think anyone has ever managed to get an answer regarding a set procedure for testing air rifles.

So all you can do is make sure your legal with both end of the scale of pellets. Think the law just states "capable" of producing over 12ftlb.

where abouts are you?

[Cedric 132]

Rez - what calibre is your rifle? Increasing pellet weight greatly increases your muzzle ft. poundage, so , unless the heavier pellet reduces the muzzle velocity considerably there would be a problem.

 

The problem with trying to keep a rifle under 12ftlbs with any pellet is that it is nearly impossible and inefficient.

 

To keep under the limit using a 10.65gr pellet (i.e. H&N Barracuda in .177) it would have to leave the barrel at no more than 700fps. At the same speed a 8.4gr pellet (which is what I would choose to use) would only produce 9.4ftlbs, not really efficient.

 

I watched a Si Pittaway vid. in which he weighed a tin of pellets, supposedly 14.4 grs, nearly half were 15.4grs. He was concerned with the differing impact points of the heavier pellets in competitions. However, if you calculate the ft. poundage, supposing the 14.4's were at 11.5ftlbs the 15.4 came out at 12.3ftlbs.

 

So, pellets out of the same tin could be over or under the legal limit - or am I missing something ?

[Rez 4,961]

Impossible, or enifficiant, I like the way you have put that.

 

I'm using a 98, in 177.

 

At the moment, my FTT's fit nice and snug. But I put in any RWS brand and it's 'slightly' loose. Naturally, nothing that the 'un touched trophies finger' would worry about but there is a difference. Basically, what your saying is that if it's innificiant, it wouldn't be producing the nice 11'ish ftlbs with any pellet? Or are we saying the same thing, some pellets over, some under: going on the mr pittaway point? Apologies, been down the watering hole as per usual on a Friday...

 

No idea how to spell innifiicnt btw.

[Cedric 132]

Hi Rez, I meant inefficient in that a rifle calibrated to be under the legal limit with the heaviest pellets available would not perform to anywhere near it's potential with "normal" pellets.

 

I just calculated that if your rifle produces 11.5ftlbs with H&H FTT (8.66gr), using H&N Barracuda (10.65gr) will give you nearly 14ftlbs ! That's assuming no drop in muzzle velocity due to the heavier pellet. It would take a drop of 65fps to take it under the limit.

 

I wonder just how many air riflles out there would fail if tested ?

[sharpshooter25 7]

I maybe wrong but I always thought that heavy pellets in a springer reduced the fps a lot. So for higher ftlbs of energy a lighter pellet had to used but with a pcp the results are reversed ?

[Skot Ruthless Teale 1,701]

In a fair world you would expect the cops to test your rifle with the pellets you were using at the time..

After weighing out 10 and using the average weight of those pellets.

 

But i suppose they could just falsify the results if they really wanted to 'do' you..

[Skot Ruthless Teale 1,701]

I maybe wrong but I always thought that heavy pellets in a springer reduced the fps a lot. So for higher ftlbs of energy a lighter pellet had to used but with a pcp the results are reversed ?

Thats the general jist of it mate.. try it with one of your spring guns and loads of different weight pellets and see what happens. Then try it with a pcp and compare results

Lol

[sharpshooter25 7]

Skot will do and will share, just put the TX back together after the polish and relube and tbt kit and put some pellets down the garden. Need some light so the chrono works, it's gonna be hot, the firing cycle is smooth but Fast

[Stingrey 0]

Right lets sort this out......

 

Kinetic Energy at the muzzle is calculated by using the following calculation:

 

E=WxV2/K

 

I have tried numerous pellets and the results are conclusive in that a heavier pellet will decrease muzzle velocity for any given power as to will a pellet that is too light.

 

Here is an example....

 

Take my favourite pellet JSB Exacts in .177 (8.44g) passed through my Airwolf at 790ft/s that equates to 11.7ft/lb

 

Then

 

Take the H&N Barracudas Match in .177 (10.4g) passed through my Airwolf at 685ft/s that equates to 10.8ft/lb

 

Then

 

Take the Daystate Li .177 (7.9g) passed through my Airwolf at 805ft/s that equates to 11.4ft/lb.

 

You can see from the results that there is a sweet spot for the riffle in terms of the weight of the pellet and no doubt there are even more complex calculations that the manufacturers use to set a rifle to in order to prevent a sub 12ft/lb rifle from ever breaching the legal limits.

 

 

 

 

 

 

[David.evans 5,323]

Don't know if it's true

But I was told that the old bill would chrono with 10.4 , in 177 as a rule of thumb

Don't know about .22

I'm sure I read a couple of threads the other day , where a bobby was on

May be he could enlighten the masses

Atb

Dave

[villaman 9,983]

Right lets sort this out......

 

Kinetic Energy at the muzzle is calculated by using the following calculation:

 

E=WxV2/K

 

I have tried numerous pellets and the results are conclusive in that a heavier pellet will decrease muzzle velocity for any given power as to will a pellet that is too light.

 

Here is an example....

 

Take my favourite pellet JSB Exacts in .177 (8.44g) passed through my Airwolf at 790ft/s that equates to 11.7ft/lb

 

Then

 

Take the H&N Barracudas Match in .177 (10.4g) passed through my Airwolf at 685ft/s that equates to 10.8ft/lb

 

Then

 

Take the Daystate Li .177 (7.9g) passed through my Airwolf at 805ft/s that equates to 11.4ft/lb.

 

You can see from the results that there is a sweet spot for the riffle in terms of the weight of the pellet and no doubt there are even more complex calculations that the manufacturers use to set a rifle to in order to prevent a sub 12ft/lb rifle from ever breaching the legal limits.

 

 

 

 

 

 

One of the most efficient heavy pellets in most guns are jsb heavies 10.3gr