TargetTalk

The team I help coach has over 20 Benelli MP90/95 standard pistols. My daughter & I also shoot them. I've learned over the years that after about 10 to 15 thousand rounds, the bore gets fouled to the point where you can start getting keyholing:
I've tried a variety of bore cleaners over the years, and with enough scrubbing, the pistols would be good for a couple more cases of ammo. I recently decided to try one of the newer bore cleaners specifically designed for .22's. After reading various reviews, I tested a bottle of "Bore Tech Rimfire Blend". I followed the instructions to the letter, and I must say, I am impressed. It wasn't a lot of work, and when I was done, I have NEVER seen a patch come out of a .22 barrel as clean as what I saw:
The usual disclaimers, YMMV, etc.

All of Bore tech's stuff is good

I use it exclusively for all my centerfire rifles.. Have been using the rimfire stuff for a while.

In my experience, keyholing occurs with a leaded bore, not merely a fouled one. The fact of your patches coming clean is not necessarily an indication of the bore being lead-free.

shaky hands wrote:In my experience, keyholing occurs with a leaded bore, not merely a fouled one. The fact of your patches coming clean is not necessarily an indication of the bore being lead-free.

Rimfire Blend claims to remove lead, and the pistols I have used it on show no signs of keyholing after being treated. I've already put about 3000 rounds through mine after the last treatment, with no sign of any issues.

Great, I will try Rimfire Blend then.

By the way, your target has something I have also been observing with my keyholing gun on many occasions. The more the shot is off center the bigger the keyhole. How do you explain this? (I am entertaining some hypothesis, but would like to hear other thoughts first.)

In my experience keyholing is generally caused by an issue at the crown, causing the bullet to tumble just as it leaves the barrel. Lead buildup squeezing the round, or exiting with the round could do the same, also moving the POI. The more the tumble, the wider the potential flyer, so outer ring hits make sense.

My Benelli isn't quite up to 15K, but I'm going to keep this product in mind!

-TT- wrote:Lead buildup squeezing the round, or exiting with the round could do the same, also moving the POI. The more the tumble, the wider the potential flyer, so outer ring hits make sense.

But this explanation presumes that the flier itself (not just a keyhole) was caused by the lead/crud build up. I doubt that it can have such a dramatic effect on accuracy (crown defect can be ruled out -- that would not have been removed by a cleaning solution). Also, I have called quite a few fliers that produced pretty keyholes -- so at least in my case the fliers were caused by the operator.

shaky hands wrote:Also, I have called quite a few fliers that produced pretty keyholes -- so at least in my case the fliers were caused by the operator.

Absolutely. Not all flyers land way off the POA. The circle of uncertainty is larger with them, but they can still land where they were pointed. Sometimes. :-)

I think SCATT tries to compensate for this, doesn't it? There's some sort of setting for the impact radius, and hits outside that distance are correlated with the shooter's wobble.

shaky hands wrote:Great, I will try Rimfire Blend then.

By the way, your target has something I have also been observing with my keyholing gun on many occasions. The more the shot is off center the bigger the keyhole. How do you explain this? (I am entertaining some hypothesis, but would like to hear other thoughts first.)

When my Benelli starts keyholing, my shots go pretty much on-call, but the holes are usually are just a bit oversized. The sample target was a rapid fire target from a student, who was just learning. It was too good to pass up, so I grabbed it to photograph before he shot his second string.

The shot that went in sideways was probably not very accurate. I had keyholing issues with a 30-06 rifle years ago. It belonged to our club, and freshly cleaned, it shot fine and I was putting all my shots in the black. After about 8 rounds, they started going all over the place, and some were barely on the target. The really wild ones were going in sideways. An examination of the bore showed that the rifling was pretty much absent at the throat, slowly fading in over the first half of the bore. All it took was a little extra fouling to push it off the stability cliff. To address an earlier comment, the crown was fine...

Gwhite wrote:An examination of the bore showed that the rifling was pretty much absent at the throat, slowly fading in over the first half of the bore. All it took was a little extra fouling to push it off the stability cliff. To address an earlier comment, the crown was fine...

Compromised rifling definitely makes sense; if it's not spinning, the bullet will knuckle and do any manner of unpredictable thing. Undersize ammo can do the same. I'd assume those type of issues would be ruled out early, for a competition gun, and they won't "clean out". Anyway, point taken.