Keyholing with a new barrel

[Bill K]

if you have a 25, 6mm & a 6,5 bullet take each and hold the pointed end into your muzzle and see which one seems to fit that bore. Other wise do a chamber cast and measure things.

 

[Keith Glasscock]

If it was a 6.5 barrel blank chambered with a 25 Creedmoor reamer, a 6.5 Creedmoor round still wouldn't chamber because the neck would be too small. Best practice would be to check the barrel for twist and bore before doing much else.

Think horses before zebras. If the obvious stuff doesn't give you an answer, go ahead and start looking at the more exotic possible causes.

 

[dellet]

A .257” bullet would likely press completely with thumb pressure into a 6.5 bore thats roughly .255-.257” diameter.

 

[ebb]

If it was all done by Mc Gowen, why not let them figure it out? If it has the wrong twist or the wrong bore size, it's not like you can fix it without a new barrel anyway.

 

[SD guy]

If it was all done by Mc Gowen, why not let them figure it out? If it has the wrong twist or the wrong bore size, it's not like you can fix it without a new barrel anyway.

Agreed. Send them a E-mail & or dial them up, on the phone & work this out with the folks who provided this barrel.

Someone here is likely on the right track for the root cause though, unless the vender is involved your are no closer to a solution, or so I suspect.

Though running a tight patch down the barrel to get a good idea on, verifying if the twist is close to what you need for the application at hand may be good information to have, while discussing your keyhole issues with your barrel supplier.

 

[Jerald]

McGowen blank, chamber cut by a gunsmith or a McGowen cut chamber? Call the seller get your money back.

Frank

 

[Jerald]

Post picture(s) of the crown…

1st pic crown with tread protector 2nd with out tread protector 3rd pic another crown I have on another barrel all with 11° angle crown

 

[AlNyhus]

So....what did the twist check out to be???

 

[expiper]

I agree with Post number 48 you're getting advice from some of the best shooters in the country and it would take 10 minutes to figure out what the twist is please let us know the results .... Roger

 

[6ShotsOr5?]

You can decide whether this is relevant but I had a brand new S&W snub nosed 38 special that keyholes everything from day 1 with factory ammo. I couldn’t see anything wrong with the crown, but S&W thought the crown was the problem. They replaced the barrel, and after that it shot great.

You told us “the crown looks rough”. The twist rate certainly isn’t too slow, and a faster than needed twist does not cause keyholing.

Seems pretty obvious the crown is the problem.

 

[tommeboy]

nothing with that crown is going to cause a keyhole. Twist or diameter is the reason.

 

[DShortt]

nothing with that crown is going to cause a keyhole. Twist or diameter is the reason.

Agreed. As it's turned down for threading it might be .001"-.002" loose at the muzzle, but that won't cause keyholes. Just crappy groups. Like 2-3 MOA IF it is in fact loose.

 

[Jerald]

Post picture(s) of the crown…

 

[Jerald]

So....what did the twist check out to be???

1 in 7

 

[Webster]

25 creedmoor 1 in 7 twist. 26 inch. A round 30 shots , all keyholed. 133 berger , 117 sst,and 117 round nose bullets. All keyholing. Brass looks normal
But the crowd looks rough. I'm no machinist. And it's a McGowen barrel. Any suggestion?

Should be a quality barrel. I think the bearing length of the bullet is related to stability. Either the Berger or Sierra website that has a stability chart.

The Berger stability calculator says the bullet is marginally stable.

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

 

[Just Say Moe]

I had a 338-06 chambered in a 35 cal barrel that key holed. The 35 cal blank was put in the 338 bin by mistake. Don't know if it was mis-stamped or not. The company made it right and gave me the long chambered 35 Whelen barrel for free.

 

[effendude]

Years ago, I read an article in a shooting magazine about rifle barrel crowns. I don't recall all the specifics, but the author intentionally damaged the crowns of several rifles to see the affect on accuracy. These experiments included cutting the barrel shorter and crooked with a hack saw, purposely filing a groove in the crown with a round file, dropping the muzzle repeatedly on concrete and probably a few other destructive tests I don't recall. The author was surprised that none of these damages severely affected the accuracy of the rifles. Obviously, they were not match rifles expected to shoot sub MOA groups, but the before/after accuracy tests were basically similar. They couldn't get a bullet to keyhole or dramatically off point of aim.
Scott

 

[Webster]

Years ago, I read an article in a shooting magazine about rifle barrel crowns. I don't recall all the specifics, but the author intentionally damaged the crowns of several rifles to see the affect on accuracy. These experiments included cutting the barrel shorter and crooked with a hack saw, purposely filing a groove in the crown with a round file, dropping the muzzle repeatedly on concrete and probably a few other destructive tests I don't recall. The author was surprised that none of these damages severely affected the accuracy of the rifles. Obviously, they were not match rifles expected to shoot sub MOA groups, but the before/after accuracy tests were basically similar. They couldn't get a bullet to keyhole or dramatically off point of aim.
Scott

On VarmintAls website I think he said he touches up the crown by hand spinning a fine round grinding stone on the muzzle like you might have on a Dremel tool. It's been att least 5 years since I read the article.

 

[6.5 forever]

Bore scope it and see if the throat is rough and check the crown. I would also check the actual twist rate.

Start here.

 

[ZenArchery]

Have a 22CM AI running 1-6.5TR to see if I could over stabilize the lightest copper monos. I believe it was a 1-14 bullet in a 1-6.5TR barrel. I tested some 55gr Hornady CC and it ripped them apart. Kinda cool watching them mist about 10 feet from the barrel. I looked for “over stabilization” out to 300 yards with 33gr copper mono. Paper target was fine.

As everyone said figure out to TR and get back with us.