22-250 is shooting keyholes

[prairie dog hntr]

I have a thompson contendor encore rifle chambered in 22-250. I have a custom muzzle break on the barrel. I was at the range last weekend getting ready for my annual prairie dog trip and started to get keyholes at 100 yds. I have been trying to figure out what is causing this. I am using a 55 gr v max and never had a problem before. I have cleaned the barrel thoroughly and the rifleing looks good. The barrel is only 4 years old and probably has 800 rounds through it. I have read that it could be caused by a worn barrel or that the round is either going to slow or too fast for the rifling. I am using 34 grains of BLC2 powder and magnum primers. Can anyone explain what this could be and why it keyholes. Surprisingly at 100 yds the groups are still around 1". This is consistent the out of 15 rounds the last 5 went in side ways.

Chris

 

[Afy]

I would suspect not enough powder.

 

[Mal H]

If you're positive you are getting keyholes and not target paper tearing (some mistake that for keyholing), then you have either too slow a speed, or the incorrect twist rate for that bullet.

Can you chronograph the rounds? What is your barrel twist rate?

You might try either more BL-C2 or switch to a faster burn rate powder such as 3031 to increase the velocity in your shorter than average barrel.

 

[bigedp51]

I have a thompson contendor encore rifle

He said "rifle" and not pistol, so he has at least a 24 inch barrel.

prarie dog hntr

Use some foam bore cleaner and make sure you get plenty inside the muzzle break. Something may be disturbing the blast pattern forcing the bullet to tip as it leaves the barrel.

 

[deacon8]

Have you looked at the muzzle and crown? Damage to the muzzle will cause bullets to fly incorrectly. Out of curiosity, what is the accuracy like (when the bullets don't keyhole)? How long have you been using that load with and without problems (when did you start noticing problems)? And does it keyhole with other loads?

 

[Grumulkin]

All Thompson/Center .224 caliber barrels are 1:12 twist and should stabilize 55 grain bullets just fine. In fact, my 222 stabilizes 70 gr. Speer Semi-Spitzers just fine. I think it's unlikely that too light a load is at fault. I would be looking very closely at the crown and rifling.

 

[MtnCreek]

How well supported is the target? Did the target have a good, solid backing?

 

[Mal H]

"He said "rifle" and not pistol, so he has at least a 24 inch barrel."
Ah! Right.

pdh - can you remove the muzzle brake and fire a few groups? That has to be the most suspect part of the equation after you've examined all other parts of the barrel.

(Why do you need a muzzle brake on a 22-250?)

 

[BoilerUP]

(Why do you need a muzzle brake on a 22-250?)

Spotting his own shots, wanting to see the red mist from his hits, or simply incremental decrease in recoil over a long day on a dog town?

 

[243winxb]

Clean the muzzle brake

 

[GooseGestapo]

I'm going to suggest that it's the bullets.

My Remington M700 ADL synthetic is an absolute tack driver with Sierra bullets up through 55gr including the Boat Tail soft point and Boat Tail Hollow Point bullets. Groups will run 0.4" or so for 5-shots with a 50 or 55gr bullet such as the Sierra or Hornady flat-based bullets w/o a cannulure.

However, it will not hit the target at 100yds with a 60gr Hornady V-max, and a 55gr V-max will shoot 3-5" groups. Same powder charges and similar seating depths.

Rifle has a 1/14" twist barrel which is common to most .22-250's.

I have a 1/12" twist Remington M7 in .223 that will shoot at best 1.0" groups for 5-shots, but it will shoot 1.0-1.3" groups with the 60gr V-max bullets and 1.0" groups with any decent 55gr bullet including the Hornady 55gr V-max.

My 16.5" bbl AR15 with a 1/9" bbl will shoot any decent bullet under 70gr into very, very small groups. But "scatters" 77gr A-max bullets at 100yds.

Hence, I suggest you use at maximum, a 50gr Poly-Tip bullet through a 1/14" twist (.22-250 or some .22-Hornet's) barrel.

Or, get a 1/9 or 1/8 twist barrel for your T/C frame.I noticed that you said it was the last 5 rounds that did this. Combine a marginally stabilized bullet and a fouled bore, you'll get keyholing.

Also, I had a friend that 4yrs ago got excited on a prararie dog town with his Savage M112 HB in .22-250. He went through about 400rds of 40gr V-max bullet over 40.0gr of Varget. When he got home and cleaned his rifle, he went to the range and tried to reset the zero and work up a load for the 50gr V-max. He couldn't get it to hit the target with anything. He later found out that he had shot out the first 6" of the throat of his barrel. He had to sent it back to Savage and had them rebarrel it.
He had a total of about 1,000rds through his barrel!!!

 

[prairie dog hntr]

Thank you everyone for replying. There is a correction. I am using WC 840 powder at 31 gr. I have cleaned the gun very well before I had this problem and there is nothing that I can see wrong with the barrel except some build up between where the barrel stops and the muzzle break starts that I can not clean out but it isn't close to the barrel or break. I am ruling out the muzzle break at this point. I think the problem is the bullets. I used to use BLC2 but changed. Always on the lighter side of the charts because I don't want to get excited and shoot the barrel out when on a good dog town. I am going to chronograph them tomorrow and see if they are possilbly moving to slow. I am also going to compare to some factory ammo to see if I get the same problem. I will give a range report tomorrow with velocities and see in it confirms what I think might be the problem.

Chris

I used hoppes and sweets to clean the barrel. I ran patches until no more copper was coming out and no more residue from the hoppies was coming out. The barrel is definetly clean.

 

[prairie dog hntr]

Exactly like to see the red mist. We do use spotters but its not the same.

 

[prairie dog hntr]

I cannot remove the muzzle break as it is welded onto the barrel. I have an old barrel without a muzzle break. That I am also going to try tomorrow. It isn't in as good of condition but I want to see if they do the same thing. I suspect that the bullet isn't traveling fast enough.

 

[prairie dog hntr]

The bullets are definetly key holed. I am puting the targets on a piece of fiber board and you can take a bullet and it matches exactly. It is even tearing through the fiber board side ways. When the bullets don't keyhole they are very tight groups at 100 yds less than 1/2". Surprisingly when they do key hole I still manage to hold about a 1" group.

 

[Mal H]

Two spelling suggestions for you. I don't normally do this, but you keep repeating the error:

1) It's a muzzle brake. If you have a muzzle break, then it's time for a new barrel!

2) Do you want me to correct your user name for you? Those dogs you hunt are prairie dogs.


It definitely sounds like you are getting keyholing. Since the groups for the keyhole rounds are still in the 1 MOA range, that probably means they are going unstable very close to the target at 100 yds. It would be interesting to try groups at both 50 yds and 200 yds. I'd bet you get almost no keyholing at 50 and a lot more at 200.

The chrono work should shed some light on the problem.

Where did you find the load data for WC 840?

 

[snuffy]

So, is your rifle a contender or is it an encore? Can't be both. I never heard of a 22-250 in a contender, so I'm assuming it an encore.

I'm gonna go against the tide and say you might be pushing those v-max bullets too fast. The v-max is a lightly constructed varmint bullet. The jacket is thin so that it fragments in small animals like a PD. As such, if you push 'em too hard they will self-destruct. Look closely at those targets. See any gray smudges around the bullet holes? That would be vaporized lead from a bullet coming apart.

WC-840? Never heard of it! WC-844, yup that's similar to H-335. Don't know how H-335 loads in a 22-250, or how 31.0 grains figures as for velocity. You might be above 3500 fps, then experiencing bullet self destruction.

I had a M700 Remington in 22-250. I was loading the 55 grain SX Hornady. I was aware of the speed limit on those extremely thin jacketed bullets. I picked a load that was well under the 3300 fps limit. The rifle was being used for a jug shoot, water filled milk jugs from 50 to 100 yards. My son was shooting the rifle, he was missing the close jugs, said he was right on them. THEN we noticed what appeared to be a gray rope in the air on the bullets that were missing. The bullets were breaking up in mid air! One of the jugs that was missed @ 56 yards had little gray particles of lead on the surface.

 

[Mal H]

WC-840? Never heard of it!

I hadn't either, but danged if I was going to show my ig-o-rents!

He indicated in the first post that it was an Encore rifle (I missed the rifle part initially).

 

[snuffy]

Mal, I'm nit picking, the TC contender is mainly a pistol, but they did make a .223 long gun. The encore is both a pistol and a rifle but is a beefed up version of the contender.

I never heard of a welded on muzzle brake. I would say it would be VERY hard to weld a brake on straight AND without damaging the crown. (I made my living as a welder for most of my working life). In order to steel weld, you have a LOT of heat involved, more that can be applied to precision barrels. I HAVE heard of silver soldering a brake on, the heat required is much less. Most have the muzzle threaded for the brake.

 

[prairie dog hntr]

The rifle/pistol is an encore. Sorry for the spelling I wasn't using spell check and I was writing this late at night. The powder again another typo was WC846. That being said. The range report for today.

I have concluded that the velocity was too low. I used a chronograph and checked this round compared to factory. The velocity was 3150 ft/sec. The velocity of a factory round was 3400 ft/sec.

I didn't have any keyholes when shooting the factory rounds so I am ruling out the barrel and muzzle break.

I also tried some hotter loads that were at 3700 ft/sec and again no problems with keyholes.

My conclusion is the bullet was going to slow and the bullet was not stabilizing out of the muzzle.

The muzzle BRAKE is welded to the barrel. If you google muzzle brakes for the encore there is a company out there that makes them and they do weld them / braze them to the barrel. In hind site I don't like how they did it and wouldn't recommend them but the muzzle brake does work. Something like howitzer muzzle brake comes to mind.

I want to thank everyone for responding and trying to point me in the right direction. Any and all help was better than aimlessly searching in the dark.

I didn't try the old barrel for those wondering. Once I started getting better results with faster velocities I didn't bother switching barrels.

Chris

 

[prairie dog hntr]

Mal H could you please revise my username I would appreciate it. I keep trying to log on using the correct spelling and keep getting the message that my username and password don't match.

 

[Mal H]

You got it.