Take your arrows home, get a small saw and CUT OFF THE HEADS!!!!!!!! (yes - there are some people who need to be told this. Cut off the metal point, throw it away, use it for jewelry but get it away from the arrow. No you can't just put a bung over it or you will kill someone, okay!!
Many UK LRP organisers may decline arrows with more than a 28 inch draw (distance from the trough of the nock to the back of the head).
Most archery shops make up arrows as they go along, and where I have bought shafts they will make you up shafts without heads, and, strangley enough, charge you less than for an arrow that you will have to butcher.
So, let's assume you now have one or more sticks with feathers and a plastic widget at one end and nothing on the other.
To this end, the tip is a composite of a number of layers of different textures and wider than the eye socket (i.e. minimum of 2 inches / 50 mm).
The 'classic' way is to take two blocks of rigid foam each at
least one inch thick and two inches on a side. Mark a line on one face
of each block perpendicular to one chosen edge. Sand along this line to
form a groove. Glue the block to the end of the shaft so that the shaft
runs along the groove in the block and the face from which the perpendicular
line was drawn is flush with the end of the shaft. Then glue the matching
block onto the first block and onto the shaft. You now have a big block
of rigid foam glued around the end of the shaft. Carve off the corners
to form a rough cylinder (keeping it at least two inches wide)
After the main tip has been fitted, this can be carved to be more cone shaped.
An alternative is to take a sheet of rigid foam of any thickness
and cut a number of discs out of it. The best way to do this is with a
press and one of those really dangerous drill attachments which is
made to take one of a set of cylinderical saw blades. Anyway, produce a
set of anulli (discs with holes in the middle) which will push onto the
end of the shaft. Make them in reducing sizes so that the largest is at
least 2 inches wide and the smallest is about an inch. Cut as many discs
as you need to build up a cone running down the shaft for about three inches.
Slide them a little way further up the shaft. Now glue the big disc to
the shaft, flush with the end. Glue the other discs to it and to the shaft,
one by one.
At a later stage the steps in this support can be trimmed to form a smoother cone.
A third but much less satisfactory method is to take a long strip of normal foam abut three inches wide and glue it around the end of the shaft in a spiral until the 'bandage is mor then two inches wide.
For various reasons, I have been using an alternative material for my blockers. The modern house seems cluttered with expired credit cards. These are made from a very durable plastic and are 'free'. Cut a piece off and trim it to about 0.75 inches in diameter. Glue it on the end of the supported shaft.
If you are using the multi layered disc support heads described above, you could glue the barrier plate right onto the end of the shaft before you glue the discs, to ensure hard contact.
(The reason I started to do this was that I heard that some game organisers were going to use metal detecters to check the people really had taken the metal heads off of their arrows. I have found that IMHO these plastic buttons take glue better than metal coins. And thank you Tesco for supplying me with plastic cards on every visit :-) )
The rigid foam must be stiff enough not to flex when the end is made up but not brittle enough to take permanent deformation under normal use. Or heavy. Checkout the foam
The normal foam can but the same foam as is used fro latex swords. It can be the rigid foam from above, depending on the foam.
Soft foam is what some people call furniture foam very soft and fluffy.