08 Jan 2005 02:24:32
BizkitShooter
Advertised Velocity for Gammo CFX

I have had a CFX for a while now. I just got a chrono for Christmas because
I started reloading. I tested the chrono against my Gamo and the velocity
for various pellets was consistently around 850fps. Is this normal for a gun
that is advertised to shoot 1000fps? Thanks!!

Tim




07 Jan 2005 23:00:25
R
Re: Advertised Velocity for Gammo CFX

Some inflate their numbers more than others. Usually, when recording
numbers, they use the absolute lightest pellets around to get the high
numbers. I think they add on a bit even after that. If you're getting 850 of
an advertised 1000 out of it, be thankful.
"BizkitShooter" <tmccrimmon@nc.rr.com > wrote in message
news:AvHDd.5375$fE4.532097@twister.southeast.rr.com...
>I have had a CFX for a while now. I just got a chrono for Christmas because
> I started reloading. I tested the chrono against my Gamo and the velocity
> for various pellets was consistently around 850fps. Is this normal for a
> gun
> that is advertised to shoot 1000fps? Thanks!!
>
> Tim
>
>




07 Jan 2005 21:26:04
Mike Nelson
Re: Advertised Velocity for Gammo CFX

R wrote:

> Some inflate their numbers more than others. Usually, when recording
> numbers, they use the absolute lightest pellets around to get the high
> numbers. I think they add on a bit even after that. If you're getting 850 of
> an advertised 1000 out of it, be thankful.

I'll second that. Even the more reputable manufactures fudge the
numbers. Check out the specs for the RWS 350. I'd buy one in a heart
beat if it really shot that hard.

On any given spring gun, the spring will produce a very constant and
fixed amount of energy. If they didn't, they'd shoot like crap because
the velocity would be all over the place. The only way to get more
energy from one is to get a stronger spring or compress it further.
It's physics and not subject to marketing claims.

If a .177 gun shoots an 8 grain pellet at 850 fps, that's 12.8 ft-lbs.
There are a few other variables, but for the most part, that gun will
only shoot at 12.8 ft-lbs ever. (OK it goes down as the spring weakens
over time.) In reality it's a range, probably from 12.5 to 13.

Run the equation backwards and you'll find that in order to get a 1000
fps out of the gun, the pellet can only weigh 5.8 grains. A gun offered
in multiple calibers still uses the same spring. The same gun in a .22
caliber will only shoot a 16 grain pellet at 600 fps.

Here's what I got out of my .20 cal R9 with different pellets. Weights
are measured on a RCBS reloading scale and velocities were measured with
a F1 Chrony, adequate, but not high precision.

Pellet wt. velocity ft-lbs
H&N 10.1 811 14.7
FTS 11.5 755 14.5
Ram Jet 11.7 753 14.7
Crow Mag 12.3 725 14.4
Kodiak 14.1 660 13.6

Note that the heavier pellets produce less muzzle energy, but they group
well and had by far the lowest standard deviation at 3.1 (that's part of
those 'other variables' part. :) )

Bottom line, if you shave a pellet down to ~5 grains you will get the
1000 fps you are looking for, but you won't get any more energy from the
gun. It will shoot a little flatter, but in strong guns and with light
pellets, the groups tend to open way up.


Regards

Mike


08 Jan 2005 12:32:46
Alf Sauve
Re: Advertised Velocity for Gammo CFX

Straight Shooters actually tests the models they sell and publish the
velocities they got from various pellets. They don't sell Gammo, but it is
still worth while to compare manufacturer's claims with actual tests.

Alf

"BizkitShooter" <tmccrimmon@nc.rr.com > wrote in message
news:AvHDd.5375$fE4.532097@twister.southeast.rr.com...
>I have had a CFX for a while now. I just got a chrono for Christmas because
> I started reloading. I tested the chrono against my Gamo and the velocity
> for various pellets was consistently around 850fps. Is this normal for a
> gun
> that is advertised to shoot 1000fps? Thanks!!
>
> Tim
>
>




08 Jan 2005 12:32:46
Alf Sauve
Re: Advertised Velocity for Gammo CFX

Good dissertation, however I do take exception to one item. If a gun is
producing 12fpe with .177 it may actually produce more, or less, fpe with
other calibers due to efficiency of transfer of energy from the compress air
to the pellet speed.

Take Straight Shooters actual test with a Beeman R1 firing Beeman Ram Jets,
in .177 they got 16 fpe, in .20 they got 17 fpe and in .22 they got 18fpe.

I agree manufacturer try to make their guns look good and the best defense
is to find someone whose done real world testing.

Alf

"Mike Nelson" <mnelson62@comcast.net > wrote in message
news:e6qdnYkYaK1280LcRVn-tg@comcast.com...
>R wrote:
>
>> Some inflate their numbers more than others. Usually, when recording
>> numbers, they use the absolute lightest pellets around to get the high
>> numbers. I think they add on a bit even after that. If you're getting 850
>> of an advertised 1000 out of it, be thankful.
>
> I'll second that. Even the more reputable manufactures fudge the numbers.
> Check out the specs for the RWS 350. I'd buy one in a heart beat if it
> really shot that hard.
>
> On any given spring gun, the spring will produce a very constant and fixed
> amount of energy. If they didn't, they'd shoot like crap because the
> velocity would be all over the place. The only way to get more energy
> from one is to get a stronger spring or compress it further. It's physics
> and not subject to marketing claims.
>
> If a .177 gun shoots an 8 grain pellet at 850 fps, that's 12.8 ft-lbs.
> There are a few other variables, but for the most part, that gun will only
> shoot at 12.8 ft-lbs ever. (OK it goes down as the spring weakens over
> time.) In reality it's a range, probably from 12.5 to 13.
>
> Run the equation backwards and you'll find that in order to get a 1000 fps
> out of the gun, the pellet can only weigh 5.8 grains. A gun offered in
> multiple calibers still uses the same spring. The same gun in a .22
> caliber will only shoot a 16 grain pellet at 600 fps.
>
> Here's what I got out of my .20 cal R9 with different pellets. Weights
> are measured on a RCBS reloading scale and velocities were measured with a
> F1 Chrony, adequate, but not high precision.
>
> Pellet wt. velocity ft-lbs
> H&N 10.1 811 14.7
> FTS 11.5 755 14.5
> Ram Jet 11.7 753 14.7
> Crow Mag 12.3 725 14.4
> Kodiak 14.1 660 13.6
>
> Note that the heavier pellets produce less muzzle energy, but they group
> well and had by far the lowest standard deviation at 3.1 (that's part of
> those 'other variables' part. :) )
>
> Bottom line, if you shave a pellet down to ~5 grains you will get the 1000
> fps you are looking for, but you won't get any more energy from the gun.
> It will shoot a little flatter, but in strong guns and with light pellets,
> the groups tend to open way up.
>
>
> Regards
>
> Mike




08 Jan 2005 10:42:38
Mike Nelson
Re: Advertised Velocity for Gammo CFX

Alf Sauve wrote:
> Good dissertation, however I do take exception to one item. If a gun is
> producing 12fpe with .177 it may actually produce more, or less, fpe with
> other calibers due to efficiency of transfer of energy from the compress air
> to the pellet speed.
>
> Take Straight Shooters actual test with a Beeman R1 firing Beeman Ram Jets,
> in .177 they got 16 fpe, in .20 they got 17 fpe and in .22 they got 18fpe.
>
> I agree manufacturer try to make their guns look good and the best defense
> is to find someone whose done real world testing.
>
> Alf
>
You are correct. These are some of those 'other variables' I left out.
Straight shooters is a great site to get some real info.

One way to tell that they use the same spring is to look at the cocking
force listed for the gun. If the gun dimensions are the same except for
caliber (i.e. no increased length to provide extra leverage) and the
cocking force is the same, you can be very certain that the spring is
the same.

In many respects the cocking force is almost as good an indicator of the
power of the gun as the listed velocities. If you check the cocking
force of the Beeman Crow magnum vs. the RWS 350 and then compare the
dimensions of the guns, you'll quickly realize that there's no way the
RWS is going to shoot that hard.

Basically when you cock the gun, you're putting in the force that will
go in to the pellet. A hard shooting springer will be tough to cock.
If it has an average cocking effort, it will shoot at a more moderate
level.

Naturally, it's also a function of the cocking lever mechanics and
especially its length, so this is only good for a ball park estimate.

Mike


08 Jan 2005 10:46:56
Mike Nelson
Re: Advertised Velocity for Gammo CFX

BizkitShooter wrote:

> I have had a CFX for a while now. I just got a chrono for Christmas because
> I started reloading. I tested the chrono against my Gamo and the velocity
> for various pellets was consistently around 850fps. Is this normal for a gun
> that is advertised to shoot 1000fps? Thanks!!
>
> Tim
>
>

This site has some gamo shadow 1000's listings, but I couldn't find a
CFX listed.

http://www.airgunexpo.com/airgundb/airgundb_list.cfm

Regards

Mike


08 Jan 2005 21:16:03
R
Re: Advertised Velocity for Gammo CFX

Great reference site. Thanks!
"Mike Nelson" <mnelson62@comcast.net > wrote in message
news:9NGdnZV04asDt33cRVn-3Q@comcast.com...
> BizkitShooter wrote:
>
>> I have had a CFX for a while now. I just got a chrono for Christmas
>> because
>> I started reloading. I tested the chrono against my Gamo and the velocity
>> for various pellets was consistently around 850fps. Is this normal for a
>> gun
>> that is advertised to shoot 1000fps? Thanks!!
>>
>> Tim
>>
>>
>
> This site has some gamo shadow 1000's listings, but I couldn't find a CFX
> listed.
>
> http://www.airgunexpo.com/airgundb/airgundb_list.cfm
>
> Regards
>
> Mike