Beautiful Keyholes :)

[garandsrus]

Hi,

I just wanted to share a target with 6 keyholed boolits. It would be hard to reproduce such a perfect set of profiles!



The same boolit groups < 2" at 50 yds in the same rifle, so it's not a rifle, boolit, lube, or alloy problem. I changed a few things so I need to figure out which one is the culprit. Here are the specifics for the rounds that tumbled:
Rifle - H&R 38-55 Target Rifle
Boolit - Lyman 375449, gas checked
Alloy - WW
Size - .379
Lube - Bullshops Speed Green
Brass - Starline 38-55
Powder - 20gr and 21gr 2400

The thing that I changed from the "good" load was the brass and seating die.

The brass I used in the past was blown out 30-30 and .375 Win. The loading dies were .375 Win. The boolit was seated to where it lightly engraves. This leaves the last lube groove (without lube) seated out of the case. The groups are about 3-4" at 100 yds. with the issue sights.

The new batch of boolits that keyholed were loaded with Starline 2.125" 38-55 brass and a set of RCBS Cowboy dies. These were new cases and were not resized. Only the seater die was used. A light crimp was used. I loaded the rounds on a Dillon 550B so the expander die wasn't used. The powder funnel expanded the case enough to start the boolit without shaving any lead.

The overall length of the two loads was almost identical. It will be interesting to figure out what caused the difference in performance.

Any thoughts on what the cause will be?

John

[Bass Ackward]

Any thoughts on what the cause will be? John

John,

No offense, but that group looks like a typical driving pattern for my wife in the winter. Scared hell out of me for a second.

[Ricochet]

You're getting excellent consistency with that load!

[Larry Gibson]

That's an accurate load....ya got one 10X!

Seriously, something really went wrong there, will have to ponder on that for awhile.

Larry Gibson

[garandsrus]

Larry,

That shot in the middle is really beautiful....

I may have to crop the others out of the picture, which isn't hard since they are not in the 9 ring or better and use it as a new wallpaper or something

I forgot to mention that the target is from 50 yds. I couldn't hit it from 100...

John

[Tom Myers]

Check the length of the brass that was giving fair results against the Starline 2.125" brass. Then either make a chamber cast or a pound cast of the chamber to determine the correct length for the brass.

It is quite probable that the rifle is chambered for the new, short 38-55 brass and not the old style 2.125" brass.

Tom Myers
Precision Ballistics and Records

[grumpy one]

This may be way out, but was there by any chance a larger seating force required than with your previous more successful loads? If so, perhaps your new brass either has a thicker or a harder neck, or your new sizing die is a bit undersized, and you have swaged down the bullets when forcing them into the cases. I suggest this on the basis of two prior experiences. First, if I shoot factory loads from the grossly oversize barrel in my 336 30-30 I get targets that look exactly like yours. If I use either properly sized cast bullets or 0.311 J-bullets I get decent groups with no slightest sign of bullet tipping. This suggests that your bullets may be ending up undersized. The second prior experience is that I find if I use new Winchester brass in my 30-06 it lasts well, but if I use new R-P brass I need to anneal it before first use or the necks crack after 5 loadings or so. Annealing the brass makes bullet insertion way easier and I end up with much less neck tension.

I'm not suggesting that I've found your solution here, but it does look to me like a possibility you could consider - especially if you are finding bullet insertion force higher with your new brass and different sizing die. My suggestion has much the same outcome as Tom's - if your brass is overlength the bullet will be getting swaged down as it emerges from the case.

[686]

unless you turned the target you are hi and to the right. would make good holes in a deer. maybe they would be stright at 150 yrds.

[Blammer]

what primer? did you go to a normal from a magnum or vice versa?

I'd also check your case volume, may have gone to a larger case that would reduce pressure and velocity.

Looks like your boolits need some more speed.

[Old Ironsights]

That target's a keeper...

[Dale53]

Now, THOSE are Keyholes! So often you see someone call a "tipping bullet" a keyhole. THESE are keyholes.

I agree with the consensus. It appears to me that we are dealing with something that reduced the size of the bullets.
Keep us posted.
Dale53

[Misfire99]

One of the ways you can get the OAL for a chamber is to drop a rod down the bore with no round in place. Mark the rod,I use a file. The drop the bullet you want to use into the chamber and hold it in place with something. A dowel of even a sized brass will work. Then drop the rod in again, but don't unseat the bullet. Then mark the rod again. The distance between the marks is the max OAL. You can use this as a starting point when setting the OAL for your rounds.

[45 2.1]

Any thoughts on what the cause will be? John

That's an easy one. The cause is the dead soft annealed cases. Try work hardening some of the new cases by sizing and expanding without belling several times and retest. Several of us have ran into the same problem with higher intensity straight walled cartridges.

[mooman76]

Looks like you were using the ladder method!

[Scrounger]

Now, THOSE are Keyholes! So often you see someone call a "tipping bullet" a keyhole. THESE are keyholes.

I agree with the consensus. It appears to me that we are dealing with something that reduced the size of the bullets.
Keep us posted.
Dale53

Like the Lee Factory Crimp Die?

[Pat I.]

I'm going with the brass being too long. Chamber a resized case minus the bullet and see if it looks like it had a trip through a crimp die.

[Onlymenotu]

jeesh what's the problem instead of 3/8's holes...... your get'n perfect 3/8's x 1" holes * makes for a bigger blood trail* now all ya gota do is tight'n the group up to the 9x and 10x rings and your all set

[garandsrus]

Thanks for all the ribbing... I mean help

Here are a couple responses to the ideas presented, in order of the post it was submitted in:

Tom Myers - It is quite probable that the rifle is chambered for the new, short 38-55 brass and not the old style 2.125" brass.

Several other folks had reported using this same brass in the rifle with very good results which is why I bought it. I had been happy with the blown out 30-30 and .375 cases. Before I loaded any rounds, I took a new case and tried it in the rifle. It slid right in and the action locked up with no hesitation. I measured the OD of the case neck before chambering and then closed the chamber on it 5 times. The neck measurement didn't change. The loaded cases chambered without any hesitation also so the brass isn't getting hung up. I do have some cerrosafe so I can make a chamber cast. I have never done one before.

Grumpy One - If so, perhaps your new brass either has a thicker or a harder neck, or your new sizing die is a bit undersized, and you have swaged down the bullets when forcing them into the cases.

This is what I though would be the culprit so I saved one loaded round. Maybe I was just chicken, I didn't want to ruin my target! I pulled the boolit with a kinetic puller and pulled one that was loaded in a blown out 30-30 case. The result is that neither boolit was sized down when loaded and they both measure the same. The Starline brass actually has thinner necks than other brass which is why people suggested it for the H&R which sometimes(?) has larger bores than throats. I don't think I have the chamber/throat mismatch since I was able to chamber .379 boolits when other people were not.

686 - The target is rotated in the photo. The bullets were impacting a little low and quite a bit right.

Blammer - No primer change... I did check the primers for pressure signs after your comment. I hadn't noticed anything unusual at the range. The 38-55 primers are a little flattened and showing higher pressure signs than any of the re-formed 30-30 cases I looked at. I knew that 20 to 21 gr 2400 was near a top end load.

54 2.1 - That's an easy one. The cause is the dead soft annealed cases. Try work hardening some of the new cases by sizing and expanding without belling several times and retest. Several of us have ran into the same problem with higher intensity straight walled cartridges.

I understand what you wrote, and understand that neck tension could be less on these rounds, but don't understand why this would cause tumbling. Can you elaborate? The only thing I can think of is that the reduced case tension might release the boolit too easily, causing the powder to not burn with enough intensity, resulting in low velocity. I didn't chronograph these rounds but the recoil was about what was expected. I will chronograph them next time. I have had good accuracy with 8gr Unique, which I also didn't chronograph. I did chrono 9.5 gr Unique in the blown out brass and it gave me 1200fps so 8.0gr would probably be just over 1000fps with OK accuracy. I also chrono'd 20gr 2400 with the old brass and it came in at 1670fps. I was looking for a higher velocity load (1500-1600 fps) as I am running out of rear sight elevation at only 100 yds.

Scrounger - I didn't use the factory crimp die on the 38-55 brass. I used the seating die to lightly crimp the round. I did use the FCD on the 375 Win loading dies. The crimp is light.

Pat I - Chamber a resized case minus the bullet and see if it looks like it had a trip through a crimp die.

I haven't chambered a resized case yet. I didn't get any change in measurement at the case mouth when a new case was chambered multiple times. I re-chambered a fired case 5 times also and there wasn't any difference in the case mouth diameter either. The case wall appears to be straight. I checked a new case and the mouth OD was .386. A fired case is .392. The case wall is .014-.015 thick, measured with a standard caliper.

Onlymenotu - I did see a lot of confetti from the target after each shot!

I now have some once fired brass to test 45 2.1's solution.

There is no visible leading in the barrel... I put a couple patches through it and all I got was powder fouling.

Thanks again for all the ideas...
John

[45 2.1]

I understand what you wrote, and understand that neck tension could be less on these rounds, but don't understand why this would cause tumbling. Can you elaborate? Annealed case necks can produce very poor accuracy out of some straight walled (or some BN cartridges for that matter) cartridges, why we don't really understand fully. Probably from no guidance or reduction of ignition pressure, but we know it happens and don't fully anneal anything because of it. The only thing I can think of is that the reduced case tension might release the boolit too easily, causing the powder to not burn with enough intensity, resulting in low velocity. I didn't chronograph these rounds but the recoil was about what was expected. I will chronograph them next time. I have had good accuracy with 8gr Unique, which I also didn't chronograph. I did chrono 9.5 gr Unique in the blown out brass and it gave me 1200fps so 8.0gr would probably be just over 1000fps with OK accuracy. I also chrono'd 20gr 2400 with the old brass and it came in at 1670fps. I was looking for a higher velocity load (1500-1600 fps) as I am running out of rear sight elevation at only 100 yds.

[Wayne Smith]

Since Those Who Know More Than I haven't mentioned this, I may be wrong. It strikes me that your crimp was vastly different between the two, one with a "light crimp" from seating die, the other with the Lee Factory Crimp Die. Combined with the evidence of higher pressure in the Starline cases, i.e. primer flattening, could we not be looking at significantly faster velocity? Would this be enough to cause keyholes? I have no idea, but thought it should be mentioned.