Keyholing

[markwarren]

I am posting this on behalf of a fellow club member. I am not knowledgeable about this subject so if I make a c*ck of myself please bear with me.

He has recently bought a Lee .303 and is currently tuning his self loads. He is meticulous in weighing his loads (Unique) and does everything the same for each bullet. However, he is getting the odd bullet going in to the target sideways! Last night he shot a card with 8 tens a 9 all lovely round cut holes but 1 end up in the 6/7 ring and was the perfect cut out of the bullet shape sideways on. This has now happened on a few occasions but it is just the odd one and not 2 or 3.

Any help, advice or pointers would be gratefully received by him as it is driving him nuts.

All the best

Mark

[Turnup]

At what range and what MV is this occurring?

Does it happen with all loads he has tried?

First thing to look at is the barrel bore. If there is any pitting, what can happen is that bullet material lodges there and builds up until at some point the clag is removed all in one piece, destabilising the bullet, barrel is now relatively clean again and the cycle repeats.

I presume that his meticulousness includes control of COL.

Other possibilities:

Twist rate is not compatible with bullet weight - but marginally, so that some bullets are not stabilised. (Bit of a stretch this one). Could try some significantly lower MVs, or higher if safe.

MV is supersonic but falls to marginally transonic (and hence unstable) before reaching target - higher MV would prevent this - or lower so that is subsonic at muzzle if this is practical.

Crap bullets? Does he weight match them?

[zx10mike]

lighter bullets needed imo

[markwarren]

Thanks for the replies guys.

@Turnup - could you tell me what COL is please? He may know or he may not He is testing at 20 yards and I don't know the MV off hand. I will ask him. I believe he does weight match his bullets. From a laymens point of view the pitting in the barrel would explain what is happening.

I don't get any of these issues with my 10m Target Air Pistol

All the best

Mark

[amc577]

Not likely to be twist rate with the 303...probably a bad bullet fit....I assume a cast bullet is used with the Unique? Need to slug the bore...the 303 can be anything from .312 to .316....

I had keyholing with my ancient 32/40...the normal bullet size is .321...keyholing....used .323...one inch groups...same bullet.

amc577

[tacfoley]

There's something of a confusion here, on my part, at least.

The Lee is not a .303 anything, being a 6mm calibre.

Do you mean a Lee-Enfield?

Be advised then, that the Lee-Enfield can have a bore between .311" and .316", as Mr amc577 notes. It does NOT like to shoot anything much except the 174gr bullet that was the principle weight, unless of course, is is NOT a Lee-Enfield, but a Lee-Metford/Speed. In that case all bets are off, as they shot a 200gr round-nosed bullet.

COL = Complete/cartridge Overall Length - from the point of the bullet to the base of the cartridge case.

By using Unique I'm hazarding a guess that he is using cast bullets, as Unique is a pistol powder. The advice to slug the bore to ascertain the correct diameter bullet is the very next thing that your pal should do.

[Turnup]

Thanks for the replies guys.

@Turnup - could you tell me what COL is please? He may know or he may not He is testing at 20 yards and I don't know the MV off hand. I will ask him. I believe he does weight match his bullets. From a laymens point of view the pitting in the barrel would explain what is happening.

I don't get any of these issues with my 10m Target Air Pistol

All the best

Mark

COL = Cartridge Overall Length. Is measured from base of case to tip of bullet. Can be critical in some barrels - the idea is to control the distance the bullet has to travel before it engages the rifling. Too short and chamber pressures can rise as the bullet decelerates when it reaches the rifling (particularly with low MV loads). Too long and the bullet can be travelling fast enough that it gets damaged as it tries to spin up almost instantly when it reaches the rifling. The optimum COL for a particular barrel is dependant on a lot of variables, and again at 20 yards, provided that the COL is within the limits then it is difficult to see how this could be causing keyholing. Some riflists actually use over length cartridges so that the bullet is already partially in the rifling - something to be undertaken only with very careful load development.

At 20 yards we can discount supersonic/transonic transition - I presume that this is an indoor range and MV will probably be subsonic, anyway there just isn't enough time for it to have much effect. In fact at 20 yards keyholing as bad as you describe it pretty extreme and the cause is probably something gross. A member at my club suddenly had similar behaviour in his target barrelled 10/22 (different beast entirely but serves to illustrate the point). We found that it had a ring bulge about 3 inches from the muzzle. Barrel chop and re-crown sorted it.

Badly damaged crown would be expected to affect every bullet to some extent.

Not an expert on bore size/bullet size tuning so I defer to those who know about this. As Tac has suggested, slugging the bore will at least provide a basic datum for bullet selection.

If the homeloads are reasonably consistent then my money is on pitting or some other kind of barrel damage. If the barrel is really clean then damage should be visible, but you have to inspect very carefully. Damage can also sometimes be felt as you run a tight patch through the barrel - extra or less resistance at a certain point - particularly when dirty. Another trick it to run a tight dry patch on a jag through the barrel after every shot - lead buildup on a bore flaw will mark the patch in the same place every time.

Good luck with this, and if you get an answer please share with us on here.

[strebblo]

...
First thing to look at is the barrel bore. If there is any pitting, what can happen is that bullet material lodges there and builds up until at some point the clag is removed all in one piece, destabilising the bullet, barrel is now relatively clean again and the cycle repeats.

...

I'm sorry but you just can't peddle that kind of nonsense - how did you come up with that idea, can you back that up with any real evidence or proof?

[Turnup]

I'm sorry but you just can't peddle that kind of nonsense - how did you come up with that idea, can you back that up with any real evidence or proof?

I have no evidence or proof other than personal experience. It happened to my Marlin .357. About one shot in three or four with target loads at 25 yards indoors. Flyers which also keyholed (not as badly as the OP has described). Brush the bore after every shot and it was shooting fine. 'Twas badly pitted about 2/3 towards the muzzle. New barrel job Also similar effects in a mate's 10/22 (which if you had read my post #7 you would already know) due to a ring bulge near the muzzle. That's two examples.

Now please explain your credentials and why you believe my post to be nonsense.

[strebblo]

I have no evidence or proof other than personal experience. It happened to my Marlin .357. About one shot in three or four with target loads at 25 yards indoors. Flyers which also keyholed (not as badly as the OP has described). Brush the bore after every shot and it was shooting fine. 'Twas badly pitted about 2/3 towards the muzzle. New barrel job

Also similar effects in a mate's 10/22 (which if you had read my post #7 you would already know) due to a ring bulge near the muzzle. That's two examples.

Now please explain your credentials and why you believe my post to be nonsense.

You're asking someone on an internet forum for their credentials? Well done. I'm obviously the president of the NRA in space, and I also invented shooting. What's more is that ferrets are far more accurate target shooters than humans, but are not allowed to compete at club level anymore, so only a few of us who were lucky enough to be their apprentices have this knowledge.

Happy with that?


My point was that you were portraying your theory as some kind of fact, when you can't see what goes on in the bore and have built a 'fact' around a conclusion, based on a symptom that might not be related, from the evidence of just one rifle - at 25 yards? Come on, there's something else more serious going on if you can get your bullets sideways through the target in the space of 25 yards. 25 yards.

Your mates 10/22 with a bulge in the barrel is totally the opposite symptom to your pitted barrel. Two examples of not the same thing does not make any kind of statistical pattern.

Have a read of this: http://www.longrangehunting.com/arti...le-crown-1.php
that takes a commonly held belief that an absolutely immaculate crown is a must, and just smashes it. Those blokes went to quite some effort to still be unable to answer the question, and even then they could have been a lot more methodical and the experiment was far from exhaustive. But it proves the point to me that a lot of bollocks is talked by a lot of people who should be spending more time out there shooting and less time talking about it.

There are so many things in shooting that are unproven, but a few people come up with some things that sound plausible (sometimes not even that good) but without any proof or any thorough checking, and it gets lapped up.

I'm no expert, but I try to be methodical and question everything I do because this is a precision game. I know what I know until someone challenges that knowledge and if it can be proven or backed up then I need to learn from that.

My credentials? I'm a sceptic - give me a sound reason why you think your theory could be correct and why it can't be anything else.

...Because it's your theory to prove, not mine.

[Turnup]

You're asking someone on an internet forum for their credentials? Well done. I'm obviously the president of the NRA in space, and I also invented shooting. What's more is that ferrets are far more accurate target shooters than humans, but are not allowed to compete at club level anymore, so only a few of us who were lucky enough to be their apprentices have this knowledge.

Happy with that?

If you say so.


My point was that you were portraying your theory as some kind of fact, when you can't see what goes on in the bore and have built a 'fact' around a conclusion, based on a symptom that might not be related, from the evidence of just one rifle - at 25 yards? Come on, there's something else more serious going on if you can get your bullets sideways through the target in the space of 25 yards. 25 yards.

In one of my posts (#7 in this thread), when the OP revealed that this was happening at 20 yards, I did state that this was a pretty gross.

Your mates 10/22 with a bulge in the barrel is totally the opposite symptom to your pitted barrel. Two examples of not the same thing does not make any kind of statistical pattern.

The symptoms were similar, the ranges similar. No statistical pattern was claimed, but the evidence of just one example proves that it can happen at least once for each cause.

Have a read of this: http://www.longrangehunting.com/arti...le-crown-1.php
that takes a commonly held belief that an absolutely immaculate crown is a must, and just smashes it. Those blokes went to quite some effort to still be unable to answer the question, and even then they could have been a lot more methodical and the experiment was far from exhaustive. But it proves the point to me that a lot of bollocks is talked by a lot of people who should be spending more time out there shooting and less time talking about it.

I have not claimed that am immaculate crown is imperative. I do claim that a damaged crown can cause inaccuracy. Do you honestly believe that, while some barrels will shoot well with pitting or crown damage (outside of my experience but I am happy to accept the claims of others as possibilities), therefore pitting and crown damage cannot cause the reported symptoms?

There are so many things in shooting that are unproven, but a few people come up with some things that sound plausible (sometimes not even that good) but without any proof or any thorough checking, and it gets lapped up.

I'm no expert, but I try to be methodical and question everything I do because this is a precision game. I know what I know until someone challenges that knowledge and if it can be proven or backed up then I need to learn from that.

My credentials? I'm a sceptic - give me a sound reason why you think your theory could be correct and why it can't be anything else.

Show me where I stated that there can be no other cause?

...Because it's your theory to prove, not mine.

Not attempting to prove anything, just offering suggestions to the OP

You are the one who started asking for evidence.

You seem to be reading things into my posts which are not there.

The OP was asking for pointers to the cause of his friend's problem. I was not stating that the observed behaviour has an obvious cause, but listing some possibilities to look into, based upon some personal observations. I have witnessed a ring bulge cause similar behaviour at 25 yards. I have personally experienced severe pitting cause similar behaviour at 25 yards. Different cartridges to the OP's but still these are facts, when applied to the specific barrels which produced these effects. Therefore I believe that my theory could apply to the OP's problem. Review my posts and you will see that at no time have I stated that the symptoms can have only one cause, and no other, nor have I dismissed any other suggestions made (particularly the one regarding bullet fit).

[bewsh]

First thing to look at is the barrel bore. If there is any pitting, what can happen is that bullet material lodges there and builds up until at some point the clag is removed all in one piece, destabilising the bullet, barrel is now relatively clean again and the cycle repeats.

What?
No-one told my .222 then
it has a stretch of pitted barrel about 2" long where half the rifling is gone!

shoots sub inch all day long
shoots cloverleaf holes from a bench and stabilises 60gr in a 1:14" twist....


OP, your problem is bore and groove diameter vs. bullet diameter check both

[strebblo]

Good point, well made. I also have pitted tubes on a 222 & 308, and both give me excellent, consistent accuracy.

[markwarren]

Thanks for all of the replies chaps.

@tacfoley - thanks for pointing that out. It is indeed a Lee Enfield.

Thanks

Mark

[ug4758]

Bullets tumble, i.e. go through the target at an angle, because they aren't rotating fast enough. There are many reasons for this, some of which have been already mentioned, and some of the mentioned are a bit rare, but the reason is, they aren't rotating fast enough.