Compound Bow - Pressure Against Back Wall and Effect on Grouping

I was doing some practice the other day with a new release aid and trying to find a comfortable new anchor point and discovered something I hadn't come across before in shooting a compound.

Normally when I draw fully, I pull into the "back wall" with a moderate degree of pressure. I couldn't quantify it but it is pretty consistent and firm. My bow, a Martin SlayR with solocam has a very hard back wall.

Whilst playing with this new release aid I tried pulling really hard into the "back wall" and noticed an immediate effect on where the arrows were landing. They started to group well to the left of their normal position.

I went back to my normal hold and the group moved back to its normal place. Playing around with the degree of back pressure caused the group to move to the left by amounts which varied directly with the amount of back pressure.

Anyone else ever noticed this and if so any idea of the cause?

[hallso]

I've been reading the book "Tuning you compound bow" by Larry Wise and according to the book pulling hard into the wall as you release will cause the arrow to start away sharply , then slow as it goes into the valley then accelerate again as it reaches peak weight. This would cause erratic arrow flight and is probably the cause of your problem The book also says that you will get the most consistant arrow flight by having your achor point in the middle of the valley.

Hope this helps, but I'm by no means an expert so maybe someone else can give some more advise.

Rob.

[greydog]

You may also find that, as a single cam your string sits in the middle of your top limb (in the idler), but is offset as it anters the cam at the bottom, so the string in effect crosses the bow in a very slight angle to the riser.
As you pull harder into the stops, the bow force applied through the limb tips increases, and any deviation to the vertical axis is magnified.......in effect, the offseting of the string in the bottom cams causes a small amount of tourque.....when you release, the string has to move a little more sideways than usual, changing the course of your arrow.....harder you pull, the greater the deviation (up to a point where it won't deviate any more, or you'll pull your bow apart )

You could also be increasing the amount of hand torque as the forces increase.

The recommendation for most single cam bows is to shoot from the back wall. Larry Wise used to recommend you shoot from the valley, but that was when target wheels were very common and most cams still had quite large valleys, by todays standards. As long as you're consistant I don't think it matters.

[Rik]

My suspicion is that any variation is due to the form rather than the equipment. Pulling hard against the stops produces a different effect than pulling softer. That doesn't surprise me.

Are the groups better when you pull hard, or not so hard?

I'm a little wary of the Larry Wise take on drawing against the wall from all that time ago, I think it was fairly firmly rebutted at the time. Results since have shown no problems with using the wall as a draw stop.

[Jerry Tee]

I go with Rik on this one. I set my draw stops for the center of the valley and pull hard into them and I don't get any change in point of impact.

Hi Guys

Thanks for that. It's not something I've come across before because I have a pretty consistent hold position which is moderately hard against the back wall and normally never vary it.

I really didn't think that it would change the point of impact of the arrow all that much by varying the back pressure but it does and I accept your views on the cause.

I'll see if I can adjust the draw stop to put it in the middle of the valley and see if that helps. I suppose if worse comes to absolute worst, I could fit a clicker to the bow and fire on the click.

I've never had this problem with previous bows because they have all been dual cams. This is my first time with a solocam bow.

Anyway, thanks again for the input. I'm going to have to be careful in future.

[geoffretired]

I wonder if it is to do with form, too, like Rik says.
The harder you pull, the quicker is the body's follow through. In the follow through, the bow arm is moving to the gold with a bit of "left" in there too. Perhaps that left movement is faster and more pronounced, causing the arrows to be moved left.Greydog mentioned hand torque, which could add to the problem. If the hand position has any tendency to torque the bow, as the poundage increases so does the amount of torque.If that torque turns the bow so the sight moves to the right, you would get arrows to the left. You have not noticed this with other bows, but that could be because of the grip on this one.
It's an interesting puzzle. The results of your tests will be worth reading.

[Marcus26]

Left-right when pulling harder into the wall is more likely due to technique than gear, asuming the gear is in good condition.
high-low shots while pulling into the wall are indictive of nock travel issues.

[Merlin Archery]

Left-right when pulling harder into the wall is more likely due to technique than gear, asuming the gear is in good condition.
high-low shots while pulling into the wall are indictive of nock travel issues.

I agree.

You said you changed your release aid too. Different release aids can impact differently and might explain why you shot to the left with your new back tension release.

[Marcus26]

Could also be asyou pull harder into the wall you are also exerting more pressure on the side of your face, which can have profound effects on left-right.