Keyhole issue with M&P Shield 40

[oldmanontheriver]

I am curious about what causes keyhole. I recently bought an M&P Shield 40. I fired 100 round of handloads with 165 grain Berry FP's and 8.0 Gr of Blue Dot. This load has worked well in my Taurus 24/7 G2 40 cal. Out of 100 rounds about 10% keyholed.

What causes keyhole? My Taurus has 4.25" barrel and the Shield a 3.125" barrel. I understand keyhole is due to instability in the flight of the bullet, but how do I fix it?

 

[Steve C]

Your load is probably too light to get the bullet spinning fast enough out of the muzzle to stabilize it. Speer13 has no BD load for their 165 gr bullet but list 8.0grs as a start load for their 180gr bullet at 922 fps and 10.0gr for their 155gr bullet. That should put the start load for a 165gr bullet at around 9.0 gr of BD.

Increase your load a bit and it should stabilize.

 

[oldmanontheriver]

Steve, thanks for the advice. I am pretty new at this and probably a little too "gun shy".

OMOTR

 

[Safetychain]

I want you to understand that I am not saying that you are not reading your targets correctly but, I have and several friends have on occasion thought that we were getting keyholing when it was just that a paper target with either no or very little backing was used. The bullet was thought to be keyholing when it was actually just not clearly cutting a symmetrical hole in the paper. The bullet normally pushes through the paper leaving a hole with equal distance radial tears as the paper splits open (wad and semiwadcutters cut a perfect round hole). With nothing firm behind the paper target, sometimes the center of the paper hole tears loose and stays on the nose of the bullet and tears the target on one side of the hole making it appear that the bullet keyholed. Just taping the target tightly to a cardboard backer eliminated the keyhole effect.

 

[JTQ]

it was just that a paper target with either no or very little backing was used.

Excellent point. I would verify this is not the issue before changing your rounds.

 

[Fremmer]

Yup maybe try a piece of cardboard behind the paper target.

 

[mgmorden]

Overcrimping can cause keyholing, or bullets that are out of spec.

 

[Walt Sherrill]

As Safetychain notes, above:

BE SURE that what you're seeing in keyholing.

A lot of folks look at the tears in unsupported paper targets, and they see very irregular and unusual edges where the bullet hits, and not clear cuts. We've seen photos of some of this on the forum, here, and it's simply cheap paper being ripped rather than cut by the bullets.

You don't always see clear cuts with good factory ammo, unless it's wadcutter or premium SD ammo. I'll bet the paper has you fooled.