[bunnyrabbit]

Here are a few reasons a crossbow will not shoot the advertised speed:
1)most manufactures advertise their speed using a lighter weight arrow
point combination but do not recommend shooting that light. As a rule
for every 10 grains over the advertised arrow point combination weight
the manufacture used, one will lose 3 feet per second.
2)cams can be in time but if not properly advanced this will result in slower
speeds.
To obtain many shots on the bowstring and cables, keeping them lubricated,
choose a crossbow where the bow string comes down outside of the cams.
This design reduces the smaller string angle at the latches helping to prevent
additional wear and serving separation in that area.
A crossbow where the bowstring comes down inside the cams is faster as
it has a longer power stroke but a much narrower string angle at the latches
which is harder on the serving as it tries to force it to separate.
A crossbow with the adjustable butt stock is nice when wearing different
clothing for weather conditions.
A crossbow with a crank cocking device is slower than using a rope but much
more accurate. Using a rope as one nears the fully cocked position, one may
pull a bit harder on one side off setting the serving in the arrow latch area.
This will create a different point of impact than the point of aim.
If using a crank cocking device one wants it in direct line with the rail stock,
not pulling downwards which creates extra stress and wear on the bowstring.
Some butt stocks can be modified for that crank as a plug in.
The higher the draw weight, the faster the crossbow and the more maintenance
and expense to keep it operating. Also much harder on targets.
Go to some bow shops and check out the crossbows for weight, length etc.
What suits one may not suit another. Some bow shops may have a small archery
range where the crossbow can be shot.
Check the classifide section on this forum as sometimes these crossbows are up
graded or come with accessories.
A crossbow that can be decocked is nice but is much more costly and more to
go wrong.
Wishing you all the best.
Take care.