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.

[loiner1965]

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 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.

as above

[tacfoley]

I've just been huddled in my little loading shop at the end of the garden, reading about Unique and reloading using cast bullets in the Lee-Enfield.

Seems that the cast bullets DO, in fact, weigh 200gr, when cast in the Lyman #314299 mould, and that the starting load of only 11gr is the minimum recommended load, going up to 14.5gr. This bullet, however, also requires the fitting of a gas-check, and it is recommended that this tiny load be helped to stay in position by using a couple of wisps of some kind of filler to keep the powder near the flashhole. Failure to do so will give all kinds of irregular burn propagation, resulting in wildly varying muzzle velocities.

The use of a chronograph is, in my view, essential when developing a load of this kind, that has so many variables 'built-in'.

I shoot reduced/cast bullet loads in my Swiss rifles, but they are both somewhat lighter than 200gr and I use a bulkier powder, 5447 in much larger amounts. AND they are fitted with a gas-check. Shooting any centrefire rifle at 20 yards is not something I'd ever care to do, though.

It might also be an idea to try and persuade your pal to join us here, so that we can get the skinny of what he is actually doing, rather than join in a verbal relay team with the obvious risk of misinformation going in either direction.

tac

[Eyefor]

......

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

COL = Cartridge Overall Length. Is measured from base of case to tip of bullet.

Come on guys...

Measuring to "the tip" or "the point" will completely screw up anyone's reloading.

COL is measured to the ogive.

[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?

[tacfoley]

Lapua manual - 'You must absolutely follow the given cartridge overall lengths (C.O.L.) according to the reloading tables. The change in the bullet seating depth has a significant influence on the cartridge pressure.'

E. Arthur Brown site - 'Cartridge Overall Length (COL) is the distance from the case head to the tip of the bullet. Also referred to as Over All Length (OAL), it can be a confusing dimension because different bullets have different shapes that influence the Overall Length (see the diagram at right). For example, if you try to duplicate COL for a published load using a bullet that weighs the same but is a different brand or shape, it will most likely NOT fit the same COL specification... And therefore, will not perform the same.'

Cartridges of the World - 'The overall length of an ammunition cartridge is a measurement from the base of the brass shell casing to the tip of the bullet, seated into the brass casing.'

Berger Bullets - the difference between COL and CTBO - Effects Of Cartridge Over All Length (COAL) (sic) And Cartridge Base To Ogive (CBTO) – Part 2

'Posted May 23, 2013
Cartridge Base To Ogive (CBTO)
The first half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc. There is another measure of length for loaded ammunition which is highly important to precision.
Figure 2. Chamber throat geometry showing the bullet jump to the rifling or lands.
Figure 2. Chamber throat geometry showing the bullet jump to the rifling or lands.
Refer back to Figure 2. Suppose the bullet was seated out of the case to the point where the base of the bullet’s nose (ogive) just contacted the beginning of the riflings (the lands) when the bolt was closed. This bullet seating configuration is referred to as touching the lands, or touching the riflings and is a very important measurement to understand for precision handloading. Due to the complex dynamics of internal ballistics which happen in the blink of an eye, the distance a bullet moves out of the case before it engages the riflings is highly critical to precision potential. Therefore, in order to systematically optimize the precision of his handloads, it’s critically important that the precision handloader understands how to alter bullet seating depth in relation to the riflings.
Part of the required knowledge is understanding how to accurately and repeatably measure the Cartridge Base To Ogive (CBTO) dimension, and furthermore how to communicate this dimension to other shooters. The following material will shed some light on the subtleties, and pitfalls of the various methods available for measuring CBTO.'

Definition of COL - 'The maximum overall length is dictated by the need to fit into a box magazine of standard manufacture. For example, the .223 Remington cartridge, when loaded for use in the AR-15 rifle (or the military's M-16 rifle), has to fit into the removable box magazine for that rifle. This dictates that the cartridge's maximum overall length be no greater than 2.260". However, for competition purposes during off-hand and slow fire prone match stages, the .223 Remington is loaded one cartridge at a time into the rifle's receiver. This allows for the cartridge to be longer than the standardized 2.260" SAAMI maximum overall length. These cartridges can be safely loaded to a length that has the ogive portion of the bullet just touching the rifle's lands. Many competitive shooters will make these cartridges 0.005" less than the truly maximum allowable overall length, for the sake of safety.'

You do it your way, and I'll do it the way that the bullet-makers and reloading manuals do it.

tac

[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