Why Are My 158 Grain LSWC Key Holing ?

[FredMcIntire]

The gun is an H&R Handi Rifle, that has been reamed to .357 Maximum, 22 inch barrel, 2-7x32 Scope.

I loaded up some .357 Magnum cases with Missouri Bullet Company 158 grain LSWC bullets over 6 grains of Universal powder, using a CCI Small Pistol Primer.

I was having trouble with the bullets key holing at 25 and 50 yards.

Was I running these bullets too hot ? This was under maximum load as listed on the Hodgdon web site.

I also ran some .38 Special loads with this same bullet using 3.5 grains of Universal. No key holing but the group was a little big. I attributed this to our unsteady off hand shooting.

Thanks for your input !

Fred

[Goatwhiskers]

First questions would be have you slugged your barrel, and what diameter are the bullets? Fit is king. IIRC your gun has a 16" twist, as does my Cadet Max. May not mean much but my Max will not shoot 158's worth a hoot, I get acceptable results with 175-190gr boolits. Acceptable means <1" groups. GW

Edit: I also don't use the shorter cases, Max cases only.

[MtGun44]

Keyholing is caused by understabilization. Understabilization is caused by one of
two things.

1) not gripping the rifling and therefore not spinning at the rate of the rifling.

2) rifling twist inadequate to stabilize the boolit/bullet - based on length of the projectile.

1 is VERY often caused by undersized and too hard boolits. What diam boolit, what
groove diam barrel? How hard are your boolits? This is a bit unusual in the caliber,
but if the barrel is big and the boolits are small and expecially if commercial hard cast
(mediocre quality much of the time, IMO) then this can happen.

Try bigger diam and softer if you don't want to slug and measure.

2 should not happen unless the twist is very slow, I'd be surprised if this is the cause.

Bill

[popper]

Use the twist calculator to see if you are in the ball park.

[FredMcIntire]

Oops ! I meant to include that information in the original post.

The Missouri Bullet 158 gr LSWC's are .358 diameter with a Brinell 18 hardness. They say "Optimized For Magnum Velocities" .

The 185 grain Wide Flat Nose, gas checked bullets from Beartooth Bullet are .359 diameter and give very good accuracy in this gun out of the Maximum cases with 20 grains of H110.

I got a good buy on a box of 300 of these Missouri Bullets. I may know why now ! LoL.

[fredj338]

Oops ! I meant to include that information in the original post.

The Missouri Bullet 158 gr LSWC's are .358 diameter with a Brinell 18 hardness. They say "Optimized For Magnum Velocities" .

The 185 grain Wide Flat Nose, gas checked bullets from Beartooth Bullet are .359 diameter and give very good accuracy in this gun out of the Maximum cases with 20 grains of H110.

I got a good buy on a box of 300 of these Missouri Bullets. I may know why now ! LoL.

There, you just answered your own question. The larger bullets are shooting better. IME, keyholing is almost always a bullet too slow for the twist rate or too small for the bore.

[Gohon]

A .358 diameter shouldn't be key holing. Maybe lousy patterns and leading but not key holing. Universal is a fairly fast powder compared to most powders used for the 357 magnum. Might be fine in a short barrel revolver but not so good in a rifle.

Now having said that, I have never gotten good results with a SWC design out of my Handi. Whether 357 mag or 357 max, they just aren't very accurate. I get the same results with a Marlin 357 though not as severe on the pattern spread. On the other hand, bullets designed like Ranch Dogs RFN bullets of the same weight shoot just fine. The one exception is the Lee TL/SWC but it's design is not a true SWC and it is a plain base and not shot at high velocities.

First thing I would try is switch to a different powder such as Lil'Gun, H110 or WW296. If you get the same results then it is most likely bullet size as the culprit.

[Goatwhiskers]

I will say that my Beartooth 185's in .359 produced excellent accuracy, likewise my RD359190 sized .359 GC or PP. I did not have very good performance with 2400 or 4227, my best powder has been A1680 in fairly heavy loads. You can PM me for info, I don't like to publish loads as it stirs up too much stuff. GW

[leadman]

You could reduce your powder amount and see if the keyholing stops. If it does then increase the powder until it starts again and you will know it is the boolit stripping the rifling, probably.

[Shiloh]

There, you just answered your own question. The larger bullets are shooting better. IME, keyholing is almost always a bullet too slow for the twist rate or too small for the bore.

Yep.

As stated, fit is king.
Been there, done that.

Shiloh