Bullet stability

[Neil S.]

I have been working on a load with the 39 BK in my savage and have been getting mixed/confusing results. It seems that as soon as I think I've found the right load, the next time I go to the range it groups poorly. I don't have this problem with my 32 V-max reloads as the gun shoots those into ~ 0.5" consistently and will probably do better when I develop that load more. Recently I happened to shoot my 39 BK load onto a target at 30 yards and found that the bullet was partially key holing. I shot a few more times to confirm and then shot the same load at 100 yards and the holes were perfectly round which tells me that at some point between 30 and 100 yards my bullets "go to sleep" and become stable. I believe my barrel is right on the edge of stabilizing these bullets which would explain the strange groups I have been getting (like 5 rounds into .15", 9 rounds at just over an inch, and 1 round pulling the group to over 2"). Other groups are similar with some rounds nice and tight together and some "fliers" pulling the group out quite a bit. I'm thinking that some bullets are being stabilized better than others. I am about ready to give up on the 39 BK's but wanted to get some experienced input first. Will changing powder charge (read velocity) effect stability? Should I try pushing them faster or slower? Thanks in advance.

[204Shooter]

Assuming that this is your problem, higher velocity will increase the RPM of the bullet so the bullet would stabilize better. If you have room, you could try a little hotter load and see how it affects your groups.

[jo191145]

Sounds just like the classic "go to sleep theory. Your results on paper suggest otherwise.
My quess is its not the twist of your rifling but the condition of your rifling

Put some JB in the throat. Scrub like theres no tomorrow.
Personally I'd start with 600 grit paste but thats just cuz I have it
JB will do.

The Sierras are very soft bullets. If theres a problem with your bore condition they'll show you first.
I spent almost a year expierimemting with this phenomonon in two Savage barrels (at seperate times).
Results similar to yours but worse.
Developed some theories, without a bore scope all results are just conjecture
I was able to intentionally keyhole 32 bk's also by following my theories to extreme levels. To me this proves its not a twist issue.
Both those barrels were capable of shooting very small groups with hard bullets.

A fellow BR shooter on another forum was toying with the 204R. Hart barrel 1/12 with zero freebore on a custom action.
For reasons I do not know he could'nt get that gun to shoot. We emailed back and forth regularily.
Me with my opinions (considered crazy by most) he with his lackluster results. Nothing was working well.
He also reported severe firecracking in the throat. I consider that abnormal but.......what do I really know, no bore scope.

The last load combo he decided to try was 39bk's and 10X. I gave him my opinion on 10X. Filthy stuff.
Fine if you can use a brush and rod regularily. If you need to shoot long strings without cleaning look elsewhere.
He went to the range and the 39's eventually started keyholing, blowing up just like my Sav tubes did.
Upon inspection with his bore scope he found a hard layer of shiny black carbon in the throat with "silver" streaks in it.
My thought is those silver streaks were molten lead. He agreed.
Add constriction from the carbon layer and a liitle friction on a paper thin copper jacket and you'll begin melting the core.
Severe fliers are just the first indicator

I've never fired a Sierra bk in competition. Theres always that chance of a flier and doubt in my mind
Try scrubbin.

[Neil S.]

jo191145- Thanks for the detailed response. Your theory that the thin jacket is being ruptured sounds reasonable. It might explain some of the confusing results of my tests that have been driving me crazy . My only problem with this theory is that many people have reported great results with the 39 bk, in savages along with other rifles. I suppose my barrel could be more "rough" than others. I will try the JB paste polishing method, as I'm sure it couldn't hurt. This barrel is already pretty well broken in with 844 rounds down the barrel. I will report back with my results this weekend.

-Neil

[Tadunga]

Hey Neil,

Try the JB for sure. My Savage 11 was key holing the 32bk's & Sierra suggested the JB. At the time I had over 700 rounds through the bbl & I thought it should have been pretty well broken in, but I was wrong. After a couple hundred passes with the JB compound on a tight patch, changing patches regularly, I took my rifle to the range & shot my best groups ever using the 32bk's. I have yet to see another key hole.

Hope things go as well for you as they did for me.

♣ Michael

[Pepe-Lepew]

I had 39 gr. BK's key holing at 100 yds with CZ. I had cleaned the barrel with JB and copper remover before trying BK's so it was not fouling. I pushed the bullets out to max length for the mag and the bullets stabilized. I have yet to determine why my CZ does not like 39 BK's but will shoot other bullets very well.

[Neil S.]

Tadunga- I'm glad to hear of your success and that sierra suggested jb compound. I have some on the way so I will find out if it helps this weekend.

Pepe-Lepew-I have tried all sorts of seating depths w/out much luck

-Neil

[Tadunga]

Let us know how it turns out.

[Neil S.]

I just loaded up some 39 bk with what I believe to be its favorite load of RL-10x. I will let everyone know how it shoots after the bore is polished.

-Neil

[Neil S.]

Well the jb compound that I ordered came in so I went to work on my barrel today. I first cleaned all of the powder out then the copper with CR-10. I made sure there was no trace of carbon or copper in the barrel before I started scrubbing with jb. I followed the directions to a "T", and after maybe 300-400 passes (continuously patching out and reapplying jb), I cleaned out all the regular jb and switched to jb BoreBrite. This is the finer compound that puts the final finish on the bore. I made about 200 passes with this and then thoroughly cleaned the barrel. On inspection the barrel appeared nice and smooth and I believe the jb did a good job. I then wet a patch with LockEase (as I always do as the last step in cleaning) and ran it through the barrel followed by two dry patchs and headed to the range with my 39 bk loads. I set up targets at 20 yards and 100 yards. Here are the first 3 rounds out of the barrel at 20 yards:



Just like before, you can clearly see that the bullets are partially keyholed . I was not shooting for a group, I just wanted to see if the bullets were stable. Here is the first group at 100 yards:



As you can see three nice and tight, 1 flier and 1 waaay out there. groups like this have been the norm for the 39's in this gun. Also, notice how the holes are nice and round indicating that the bullets have regained their stability. Very strange. Second group:



This was a four shot group. Not bad really. I would have seen promise if I had no knowledge of these bullets wobbling early in their flight. Still, all bullet holes are round. Third group:



Interestingly, two bullets in one hole and three nice and tight next to it. As you can see, these results are pretty confusing and I have been chasing my own tail trying to find a good load with this round. I have concluded that the jb did not solve the problem although it did put a nice finish on my bore and I will be interested to see how the barrel cleans up now. I guess this is a twist rate issue and with the bullets wobbling so much within the first 20 yards I just don't see them printing consistent groups no matter what I do. Any other theories or opinions? I guess I will have to stick with the smaller pills.....

[sand rat]

I have a question for you. Is your 20 yrd target just stapled to a cardboard backer or piece of wood? Next time your at the range try shooting at 20yrds with just a piece of hard cardboard, no target. Let me know what the holes look like then. Make sure your target is straight up and down vert. and horz.

I have seen tears like this with round balls form muzzloaders when I shot in competition. It was caused by a loose target to the backer. The tighter I made the target to the cardboard backer the crisper the hole. Its kind of hard to make a round ball tumble. It also showed up usually on the closer targets.

I'm just curious.

Sand Rat

[Neil S.]

Sand Rat- I used a piece of single ply hard cardboard instead of a target to prevent tearing.



I stapled it tight against a piece of plywood. Sometimes plywood can splinter and tear up a target and I wanted to prevent this by using a stronger material. I understand that if the target was leaning back at an angle it could cause similar tears, but all 3 times I have tested this the target has been square with the rife.

-Neil

[jo191145]

Neil

Odd, very odd.
Quess my first theory was off
I would take a close look at the crown.
Odd that they all seem to be flying tip up. Seems strange to me anyway.

I've noticed on my most recent Sav 204R barrels the crown/bore junction is not particularily sharp.
Almost looks like someone hits it with a buffing wheel.
Its never been an issue for me with flat based bullets. Does'nt look proffessional but they still shoot.

If I ever dig out from this snow I'm gonna try some 39's at 20yds just to see what happens.

Quess I should ask. Have you ever shot any other bullet at 20yds?

[Neil S.]

jo191145- I have shot 32 V-max at about that range and never noticed anything but round holes. I have some factory 40 V-max that I should have tested at 20 yards as well but it slipped my mind. It is interesting that they are all pointing in the same direction. My theory is that each bullet wobbles fairly consistantly until they stablize. This would explain how some rounds can group tightly but some random ones go wide. The crown on my rifle appears sharp and uniform. If you do any testing I'd be interested to know your results.

-Neil

[jo191145]

My Wild A$$ Guess would be they're not so much wobbling.
Merely flying out the barrel tips up and eventually straightening out.
I now and always retain the right to be totally wrong.
Odd either way.

Maybe I'll try blasting some into the snowbanks in my driveway.
Trigger finger sure is getting itchy this winter. Need to hear something go bang.

In an attempt to duplicate your velocity....
How much 10X are you using?