Key-holing Bullets, again.

[Jellymon]

I bought my knight disk extreme (western setup with musket caps) about 7 or so years ago. The first few seasons it shot very well with the German musket caps, 100g of FF T7 with 300g bloodlines and 240g xtp. Usually 2”, sometimes 3” groups.

A couple years ago I started seeing a random shot slightly key hole with the 300g bloodlines so I posted a thread here and got advice to up my powder charge. So I went to 115g of T7 and it seemed to help, even though the groups had opened up a little.

Last week I went out to verify my zero and practice for the upcoming season and try out some barnes 290g spitfire t-ez’s. So I set up at 50yds and my groups are 8-10" with Bullets hitting sideways and other variations of keyholing. Thinking my gun just doesn’t like those Bullets I tried out my bloodlines and XTP’s, same thing, Bullets hitting sideways, and keyholing at 50!

So, the ff triple 7 was from last year, so thinking i had bad powder I went and bought some new fff triple7 thinking the extra velocity would help me. Nope, same results. So I looked at the bottle and noticed it says 100g max for a 250 and 300g bullet. So I tried 95g and the bloodlines grouped 3” at 100yds with only one hole very slightly keyholed. The Barnes spitfires still didn’t group very well at 50 and one keyholed. I ran out of light to test ferther.

So far the lighter powder charge seems to be helping, I’m going to need to test more. So any input? Am I on the right track using a lighter charge, or am I missing something? The barrel looks to be in very good condition and the crown looks perfect. Probably has 300+ rounds through it. Anything is appreciated, sorry for so much info. Very frustrating since this gun was so accurate and reliable for so long and the cause of many dirt naps. Pics to come.

[Jellymon]

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[Jellymon]

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[jbeaumont21]

My buddy went through the same thing with his Knight Disc Extreme that he bought about 6-7 years ago.  Finally sent it into Knight and they sent him a new rifle.  They must have made a few bad batches during that time 

[Jellymon]

My buddy went through the same thing with his Knight Disc Extreme that he bought about 6-7 years ago.  Finally sent it into Knight and they sent him a new rifle.  They must have made a few bad batches during that time 

That’s what I’m afraid of...

[jbeaumont21]

I found his post on it from back in 2013 which means he must have bought it in 2012. That makes it 7 years old so could be from the same batch.  On the brighter side you should get a new gun out of the deal.  I'm pretty sure he sent his in just a couple years ago and he got a new gun in place of it.

https://hunting-washington.com/smf/index.php/topic,128763.msg1716477.html#msg1716477

[Jellymon]

Just looked. Bought mine in 2012 as well.

[MountainDevil54]

is it a  1:30 twist? Could be that it doesnt stabilize those longer bullets.

[Jellymon]

is it a  1:30 twist? Could be that it doesnt stabilize those longer bullets.

It’s a 1:28 twist. I’m having the short 240g xtp keyhole as well. The first few years I had it it shot very well. But it’s gotten progressively worse the last few years.
I’m going to test one more time letting the barrel cool between shots like what I read in the link JB posted above, and if I get the same thing I’m contacting Knight. This gun should easily shoot with the loads I’m feeding it.

[Jellymon]

This is how it shot 100g of ff T7 and 300g bloodlines when i first got it. The tight group is 3 shots at 100yds open sights. Obviously though the other pic is more of an average of what it shot in the past.

[Sabotloader]

Jellymon

I am not totally sure what might be the problem with you rifle, but after reading your last post where you indicate at one time it shot well but now isn't - I do wonder about the bore itself.

Tumbling usually occurs when the sabot bullet combination does not get to the revolution speed (spin) it need to stabilize the bullet.  In my thoughts two things possibly a third may be happening

1. the bullet is slipping in the sabot and not turning with the sabot.  Again in my mind there is only a very remote chance this is happening since the 458-300 has distinctive knurls on the bullet to catch/latch into the sabot.

2. Somehow the sabot is slipping up the bore and not catching the lands of the bore to achieve the correct spin rate. I believe this to be the more probable answer.

There may be a real possibility that material (burned powder - even some plastic fouling which is very rare anymore) has built up on the back side of the lands and the sabot is unable to grasp the lands.  Since I do not know you your cleaning routine that is only a guess.

Also before you shoot do you remove as much oil or cleaning materials as you can before loading those first shots.  Do you shoot a few caps or primers before loading and shooting.

My first guess is really the bore needs to be thoroughly cleaned with an aggressive product like Barnes CR-10, Montana Extreme Bore Solvent, or some such product.  When applying these products they need to sit in the bore for 10-15 minutes and allowed to dissolve materials out of the bore.  Then use a good fiber brush to help dislodge the dissolved materials.
 
3. You actually do have a problem with the bore itself - not impossible at all but far down on my list of checks

Have you looked at your bore with a bore light or removal of the BP and look through bore at a light? Do the lands stand out in the bore from top to bottom.

Next when you are pushing your sabot/bullet combination down the bore, and after it passes through the crown, does it go down the bore with the same pressure top bottom.  No place along the bore that it seems to get larger and is far easier to push the load down?

Just some suggestions as to where I would start.

[Jellymon]

Thanks for the reply. Yes looking through the bore with a light the lands stand out and the bore looks shiny when clean. When clean, the first loading feels like it takes consistent pressure all the way down. Same thing after swabbing the bore between shots. If I don’t swab between shots, the first few inches are very hard to load, the middle gets easy, then towards the breech gets hard again, and there is a noticeable “white” residue in the last few inches of the bore that looks like it fills the grooves. No I don’t do anything to the clean barrel before firing my first shots.

I start cleaning with a  wet patch of TC #13 bore cleaner. 2-3 patches of that before the patches start to come out clean. Then I use a brass brush for 5 passes, followed by 2-3 more patches with the TC #13 which usually are coming out clean at this point. Then I put a few dry patches through until dry. I usually do this every 6-9 shots.

[Jellymon]

Looking closer I see some of the white residue (plastic?) in streaks going straight through the bore not following the rifling. Not sure if it’s from cleaning or not. Before shooting again I’m going to a more thorough cleaning. Thanks for the help. 

[Sabotloader]

Of course I really can tell - but looking at the pics It really looks like the grooves are coated with something.  So doing a bore cleaning with a good bore cleaning solvent might really do something for you.  Remember to give the bore solvent time to work in the barrel before patching it out. Actually you may need to do a treatment 2 or 3 times.

Those really are good pics of the muzzle you posted.

This is the type of bore brush I use - it is not a metal brush.  Just thinking you might need a brush at this point. Normally I do not use one in the bore.



A couple of additional pics....

Once you get the bore clean this is my quick and easy way to maintain it.  But, again make sure you give the 2-n-1 bore cleaner time to work. 



The 2-n-1 Bore cleaner shown here probably is not strong enough to get you need done now, it is more or less maintenance for me.

One more pic showing how I make the Windex Patches



The Ammonia in Blue Windex - is a natural metal stripper. There is not a lot of Ammonia in the in Windex but it really dissolves powder residue. 

[Jellymon]

Thanks, I appreciate it. Will be trying this this weekend.