Point of Impact. What does that mean?

Whatever sort of person I am, I seem to become extremely interested in things very quickly. Fascinated by them even. Whether it is a trait of introversion or something else embedded in my personality, I really don't know.

It all stems from my last blog post about high shooting trap shotguns that people use for DTL clay shooting. I've heard percentages mentioned and shooting inches or feet below a target, which I know is true. I understand that a shotgun with a high stock and a low rib will require a greater gap between the front bead and the target than a lower stock for example. Not satisfied with this I began to look at "Point of Impact". POI has really stoked my geekyness! The centre of pattern above a horizontal line at 40 yards.

Representation showing how as your head gets higher, so does the POI at the target.

As a start point and as an example of what I mean. If you have a flat shooting sporter that has your head in a position that your eye is looking straight along the rib of the shotgun at the bead. If you place the bead at the centre of a 'cross-hair' on a pattern plate or large piece of paper and pull the trigger, there should roughly be the same number of pellets above the a horizontal line as below it. So 50% above the line and 50% below. This is what is known as a 50/50 POI. 

Representation of a 50/50 POI

Now, I know, and it is generally accepted, that the vast majority of trap guns shoot 'high'.  But how high is high?

I have said before that I can lift almost any gun sitting on a gun rack at my club and have a pretty good idea, from how much of the rib I see, how much of a gap to leave between the target and the bead to break a clay. In saying that, I am more comfortable with flatter shooting guns than I am with very high shooting guns. These require much more guess work from me personally.

One phrase I've heard at shoots is people saying that their guns shoot 100% high. What does that mean? Well, in the scenario I mentioned before about the sporter aiming at the crosshair and half of the pattern being above the horizontal line and the other half below, in the case of 100% high, all of the pellets, 100% of them, will be above the horizontal line at 40 yards.

Representation of 100% High POI

I then did some searching online and came across mentions in various online forums etc about people setting up their shotguns to shoot up to 150% high. Krieghoff for example have a version of the Trap Special call the 'Pro Trap Special' that can be set to shoot 120% high.

That is where I started to get confused. What the hell does 150% high mean? Surely nothing can be higher than 100%? Right?

It didn't take much searching until I found a very useful graphic on the Browning website about POI and how this roughly translates in real terms.

If we go back to the sporter shooting a 50/50 pattern and look at it from a trap gun view point, for every increase of 5% of the ratio above, the centre of the POI rises by an inch and a half. So the centre of a 55/45 POI would be hitting 1 1/2" above the horizontal line of the cross-hair at 40 yards with the bead in the same place as for the 50/50 firing gun.

That would leave the ratios and corresponding heights as follows:

POI                  Height above centre in Inches

50/50                                      0
60/40                                      3
70/30                                      6
80/20                                      9
90/10                                     12
100% High                            15

If you expand that further into some of the really high figures mentioned:


POI                  Height above centre in Inches
110% high                             18
120% high                             21
130% high                             24
140% high                             27
150% high                             30

Those last numbers scare the bejesus out if me!!! 

I completely understand that these last set of figures and heights are not even thought about for DTL shooting and are used more for Olympic Trench and Olympic Double Trap.  However, sometimes when I say to people that their guns are shooting very high they look at you like you have two heads. 

I would think, or believe, that most trap guns for DTL would shoot between 60/40 and 80/20 POI.  I have really only come across one gun that I would say is in those scary numbers I mentioned above and it is a Perazzi MX2000.  I would honestly say that it is shooting 120-130% high and is a real pig of a gun to shoot for me personally.

Now, is it possible to test how high our guns shoot.  Of course it is. I'll be the first to admit that it is almost 10 years since I last shot at a pattern plate or tried to see where a gun was shooting.  The last time I did so, I was swapping about between two trap guns almost every week.  At the time I owned a Beretta 391 Semi Auto Trap Gun (wasn't I popular on the DTL lines ) and I had just bought my Miroku 3800.  Whichever one I picked out of the cabinet that morning, the first thing I would do at the ground when I arrived was to fire a few shots at the pattern plate to get an idea where they were shooting.  It probably didn't make any difference but it was just something I liked doing for myself and my confidence.  

I'll hold my hands up again and admit that I have never pattern tested a gun or cartridge. A lot of people swear by pattern testing but it is not something I have never tried.  With the costs of cartridges changing so much, it is very hard to pick a cartridge and decide that that will be the shell you will use for the rest of your shooting life.  You could go the same gun dealer the following week and he can no longer get your favourite shell so do you start pattern testing another?  I am just not that much into shooting these days to go to that trouble.  I know if I like a shell or not and will make it do me.

However, if you wish to pattern test a gun or particular shell,  shoot at a 30 inch circle from 40 yards and then count the individual pellet holes above the centre line and below, this will give a good indication of your POI.

I really don't like shooting at a pattern plate or large piece of paper from 40 yards if I am just looking to see where a gun is hitting.  From 16 yards, the ball of pellets hadn't separated much so they hit the pattern plate like a hammer leaving no question to where the shot was hitting.   If they were two inches above centre at 16 yards, this would leave them a good bit higher again at the distance where you would be looking to shoot a clay leaving a trap.

It would appear that others have thought something similar to myself. There is a lot of information available online and one I have only just discovered in the last day or two is "Point of Impact & Pattern Testing at 13 Yards" by Neil Winston.  It seems to be very interesting and well thought out and something I intend to try myself.  I'll report back on my results if I ever get round to doing a few tests.

So, what can you do if you discover your POI is to low or too high?

If your POI is comfortable enough for you then that's great.  If it's not, then too low is a lot easier to fix than too high.

Too low usually means your head is too far down on the stock.  If you have an adjustable stock then you can raise the comb a few millimeters until you can see enough of the beads or the rib to keep the bead below the target and break it.  There are other comb raising options available as temporary fixes and you can always get a fixed stock cut by a gunsmith and have it made adjustable.

Too high is a different animal altogether and can be a lot more difficult and costly to fix.  There are really only two options available if you have a fixed stock and rib.  You either raise the front bead or you take a few millimeters off the stock.  Raising the bead temporarily with a strip of wood is probably the easiest way to help with this situation.  It is just trial and error and trial and error until you get something that you feel comfortable looking down and shooting.  You could perhaps buy an aftermarket rib close to the height of the piece of wood. There are both fixed and adjustable aftermarket ribs available online.

Lowering the stock can be costly as the top of the comb needs to be taken down, reshaped and re-oiled after the work is done.  If you take it too low, the only option then is to have the stock cut and an adjustable comb added.  It could end up costing a lot more at the end of it all.

I suppose it is possible to have an adjustable heel plate fitted which might lower the gun overall.  I have never had any experience of these so cannot give any advice as to whether they would work or not.  The theory behind them seems to make sense in that you could lower, or higher, the entire gun but I just don't have any experience of them.
So, there we have a bit of a look at POI.  I hope to get a look at Neil Winston's 13 Yard testing at some stage and I'll post some results if and when I do.  I am completely happy as to where my gun is shooting as I look at the target but it will something else to pass a bit of time just out of curiosity.