Author Topic: 22-250 75gr. Keyholing (Read 1237 times)

Crudders32 · « **on:** October 03, 2005, 09:27:27 AM »

I was trying some new loads for my savage 110 in 22-250. My normal load is 55gr nosler BT and 36 grs. of IMR 4064. This load shoots pretty well, but b/c of the short length of the bullet and long throat in my rifle I cannot load the bullet so it is slightly behind the rifling in my gun. To fix this my gunsmith said to try a heavier bullet since it will be longer and therefore be seated in the brass more while still being close to the rifling. I think the rate of twist for my barrel is 1:12. I wasn't sure if this would stabilize a heavier bullet, but it is quicker than some guns that use 1:14. I made a load with a 75gr. Hornady match and 30grs. of IMR 4064. I went to the range and tried it out at 100yds and couldn't hit the paper. I tried at 50yds and noticed some serious keyholing. Is this bullet just too heavy for my gun, or is there another factor that may be causing this? Thanks.

R.W.Dale · « **Reply #1 on:** October 03, 2005, 09:38:21 AM »

The bullet is brobably just too heavy to stabilize. Secondly you brobably need to find a new gunsmith because the proper answer to the question you asked him should have been. "If it shoots good who cares how close the bullet is to the rifling."

Crudders32 · « **Reply #2 on:** October 03, 2005, 10:04:08 AM »

I forgot to ask this in my original post, but does anyone have any experience with a heavier bullet that will work better. Maybe something around 62 or 65 grns.

PA-Joe · « **Reply #3 on:** October 03, 2005, 10:12:22 AM »

Some 223s have a 1/9 or 1/7 twist. These are designed for the heavier +62 grain bullets. 1/14 are desgined for -42 grains.

R.W.Dale · « **Reply #4 on:** October 03, 2005, 10:51:27 AM »

I have gotten the 69gr Hornady bthp to stabilize through a 1-12 twist bore in a .223 handi rifle they would group OK at 100 but every so often one of the bullet holes would be slightly oblong. IMHO 69grs was pushin it 75grs no way.

Catfish · « **Reply #5 on:** October 05, 2005, 02:46:38 AM »

If you get any bullets heaver than 55 gn. to shot well at long range with the 1 in 12 twist you will be very lucky. For the 75 gn. bullet you should have a 1 in 9 twist for best results.

trotterlg · « **Reply #6 on:** October 05, 2005, 04:36:07 PM »

Velocity is everything to stabalize a bullet. It is how many RPM it is spinning not the twist rate of the barrel. You can get exactly the same stability shooting a bullet 4000fps with a twist rate of 1 in 18 as you get shooting one 2000fps in a barrel with a twist rate of 1 in 9. I had a 1 in 17 twist 22-250 barrel that was great with 45gr bullets if you shot it over 4000fps. The bullet would go unstable if it were shot at 2500fps and it would shoot the 55gr bullets stable to 100 yards. here is a link to a bullet stability calculator, if you work with it you will see that twist rate that people say you need is vastly over what is really needed. Remember the velocity of a bullet decreases faster than it's spin rate does, so spin it up fast to start and it will remain stable down range. You will need Microsoft XL (the spreadsheet to work with this). Also it is the length of the bullet not the weight that deterrmines whether or not it will be stable. Larry http://www.22-250.com/bullet/bulletstabilitycalc.xls

cal sibley · « **Reply #7 on:** October 07, 2005, 09:36:47 AM »

I have 5 different .22 Centerfires. They all have 1 in 14" barrel twists, and none of them do well with anything heavier than a 55gr. bullet. If you want to shoot 70gr. bullets you're going to need a faster twist. Best wishes.

Cal - Montreal

Ramrod · « **Reply #8 on:** October 07, 2005, 02:17:45 PM »

I'm thinking that trotterlg has the best answer here. If you think you have to shoot heavy bullets in the .22-250, load them up to max velocity to get them to stabilize. But my question is why bother when 52-55 grain bullets have alot more velocity, and are better killers.

Lone Star · « **Reply #9 on:** October 07, 2005, 04:45:12 PM »

Quote

...if you work with it you will see that twist rate that people say you need is vastly over what is really needed....

Mathematical models like the one linked are good - up to a point. Once reality proves the model wrong, believe reality. Yet the model seems to support what the bullet makers suggest anyway.

Example #1: The Sierra 69-grain bullet is ca. 0.95" long. Fired in a .22-250 it can reach 3250 fps. According to the spreadsheet linked, to be fully stabilized (SF=1.3) you need a 8.9" twist. Guess what Sierra recommends for this bullet? Nine to ten inches.
Example #2: The Sierra 80-grain bullet is ca. 1.05" long and the spreadsheet says at 3050 fps it needs a 7.6" twist. Sierra recommends between 7 and 8 inches. These are hardly vast differences....

But back to the OP's point - he wants to get the bullet ogive closer to the lands. Try the heavier non-boattailed bullets like the Sierra 60 HP, the Hornady 60 V-Max or the Speer 70 SP. This latter stabilized for me in a 1:12" .223 at below 3000 fps, it should work in a .22-250. The long boattails can't be seated too far out because the boat tail is hanging in the air...not the case with flat based bullets.