groups suddenly opened up

[dmax1800]

AZShooter - checking the bore and crown is a good idea. I never thought of it.
Do you know of a brand and model of borescope that is the least expensive but still will do the job of looking at the bore and the crown? Seems like the ones I've looked at are either big bucks or they don't work according to the reviews?
Thanks.

 

[AZShooter]

I don't know about other models. I own a hawkeye borescope. A friend got out of shooting and sold it to me for 1/2 what a new one would cost. Few people in Tucson have one. Even the gunsmiths around here don't own a borescope.

 

[dmax1800]

Thanks AZ, but a Hawkeye kit is ~ $700, plus or minus. TOOOO rich for my blood.

 

[AZShooter]

I agree

 

[MarkA]

BIGEDP51,
Temperature. Yes, the last 3 sessions has been colder than before. The last 3 sessions has been between 20 and 35 degrees. Before that the temps were 40 to mid 50s. I checked the torque of the action screws after next to the last session. IE 2 sessions ago, so I have shot it in cooler temps after re-torqueing the action screws. But that was a good thought.

I cleaned the rifle before the last session. I did get a lot of carbon and copper. Maybe I need to clean it thoroughly again. I'll try that.

Thanks for the input.

What is twist rate of barrel? I know this was mentioned way back earlier but takes more twist as temperatures drop to stabilize bullets. If they are barely stable say 1.2 - 1.3 at 60 degrees then dropping temps to 20's will prolly make it unstable.

 

[dmax1800]

The barrel is 1 in 14. Someone else mentioned that with this 55 grain Nosler Ballistic Tip Varmint bullet that it may not stabilize at colder temps (20 to 30) degrees. I talked to the ballistician at Nosler and while he said that it would be harder to stabilize the bullet at 20 degrees, it shouldn't be a real problem. But it may be marginal at colder temps at thus sometimes it stabilizes and sometimes it doesn't.

A rep at Hornady said that it would be absolutely no problem to stabilize their 55 grain V-max bullet at 20 degrees with a 1 in 14 barrel.

The lower temps is the only difference I can come up with. I hadn't cleaned the barrel 3 sessions ago when the groups opened up AND it was colder, so there should be no way that I could have niched the crown.

Is there any way to tell if the bullet has or has not stabilized when it hits the paper target? Would the hole be not exactly round?

 

[MarkA]

The barrel is 1 in 14. Someone else mentioned that with this 55 grain Nosler Ballistic Tip Varmint bullet that it may not stabilize at colder temps (20 to 30) degrees. I talked to the ballistician at Nosler and while he said that it would be harder to stabilize the bullet at 20 degrees, it shouldn't be a real problem. But it may be marginal at colder temps at thus sometimes it stabilizes and sometimes it doesn't.

A rep at Hornady said that it would be absolutely no problem to stabilize their 55 grain V-max bullet at 20 degrees with a 1 in 14 barrel.

The lower temps is the only difference I can come up with. I hadn't cleaned the barrel 3 sessions ago when the groups opened up AND it was colder, so there should be no way that I could have niched the crown.

Is there any way to tell if the bullet has or has not stabilized when it hits the paper target? Would the hole be not exactly round?

Use this to help you along the way...... I will NOT use any bullet that does not stay at 1.3 down to at least 20 degrees

JBM - Calculations - Stability

You can get most lengths from here for checking this http://www.jbmballistics.com/ballistics/lengths/lengths.shtml

Here is your huckleberry, I estimated MV.

JBM Stability 55NBT
Input Data
Caliber: 0.224 in Bullet Weight: 55.0 gr NBT
Bullet Length: 0.806 in Plastic Tip Length: 0.117 in
Muzzle Velocity: 3675.0 ft/s Barrel Twist: 14.0 in
Temperature: 20.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.011 (Marginally stable at best in cold temps!!)

JBM Stability 55 Vmax
Input Data
Caliber: 0.224 in Bullet Weight: 55.0 gr
Bullet Length: 0.811 in Plastic Tip Length: 0.140 in
Muzzle Velocity: 3675.0 ft/s Barrel Twist: 14.0 in
Temperature: 20.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.054 (still not there)

Looks to me like you gonna need to be in the 40 grain class bullets.

JBM Stability 40gr Blitzking
Input Data
Caliber: 0.224 in Bullet Weight: 40.0 gr
Bullet Length: 0.677 in Plastic Tip Length: 0.140 in
Muzzle Velocity: 3900.0 ft/s Barrel Twist: 14.0 in
Temperature: 20.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.384 (now were getting somewhere) PS The 40 grain Sierra Blitzking is the best 14 twist bullet I have tested!

OR now the big question, change barrels??!! To a 12 twist.

JBM Stability 55NBT
Input Data
Caliber: 0.224 in Bullet Weight: 55.0 gr
Bullet Length: 0.806 in Plastic Tip Length: 0.117 in
Muzzle Velocity: 3675.0 ft/s Barrel Twist: 12.0 in
Temperature: 20.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.376 (this will work all day)

 

[dmax1800]

Mark,
I also ran the JBM calc with both the Nosler and Hornady bullets. My MV is only 3420, but still according to the calc its only marginal. I also ran it with 60 degrees and it was still marginal. Interesting that at 60 degree temps I could get around 3/4" groups at 100 yards. I wonder if the calculator is not totally accurate. Seems like it may be difficult to get a relatively short 22 cal bullet to be above 1.5. But maybe a dirty barrel added to the groups opening up.

I talked to the Hornady guy again and they have not had ANY problems stabilizing a 55 gr .224 Vmax bullet in cold weather. He also said that there are a ton of guys killing coyotes with the Vmax in cold weather.

According to Nosler load info I should be around 3600 fps, but I'm only at 3420. I'm going to try loading incremental powder charges until pressure signs and see how far I can go with powder and MV. Plus I'm going to THOROUGLY clean the barrel. I may have to try the Vmax for comparison to see if they open up as well. I've not tried the Vmax bullets in this rifle.

Many thanks for the reply and info.

 

[MarkA]

Mark,
I also ran the JBM calc with both the Nosler and Hornady bullets. My MV is only 3420, but still according to the calc its only marginal. I also ran it with 60 degrees and it was still marginal. Interesting that at 60 degree temps I could get around 3/4" groups at 100 yards. I wonder if the calculator is not totally accurate. Seems like it may be difficult to get a relatively short 22 cal bullet to be above 1.5. But maybe a dirty barrel added to the groups opening up.

I talked to the Hornady guy again and they have not had ANY problems stabilizing a 55 gr .224 Vmax bullet in cold weather. He also said that there are a ton of guys killing coyotes with the Vmax in cold weather.

According to Nosler load info I should be around 3600 fps, but I'm only at 3420. I'm going to try loading incremental powder charges until pressure signs and see how far I can go with powder and MV. Plus I'm going to THOROUGLY clean the barrel. I may have to try the Vmax for comparison to see if they open up as well. I've not tried the Vmax bullets in this rifle.

Many thanks for the reply and info.

Wishing you best of luck. Keep us posted.

 

[Kansaswoodguy]

I have one gun that takes about 30-40 rounds of fouling to shoot sub MOA if I clean it I'll be shooting 30-40 foulers or so before the accuracy comes back first time I had this happen I cleaned it out really well and started to freak out a little until the group's finally came back to normal. I quit cleaning barrels after that if they shoot to their normal accuracy capability I don't clean if accuracy seems like it took a nose dive I'll clean but not before.

 

[engineer40]

I have one gun that takes about 30-40 rounds of fouling to shoot sub MOA if I clean it I'll be shooting 30-40 foulers or so before the accuracy comes back first time I had this happen I cleaned it out really well and started to freak out a little until the group's finally came back to normal. I quit cleaning barrels after that if they shoot to their normal accuracy capability I don't clean if accuracy seems like it took a nose dive I'll clean but not before.

You don't even clean some of the carbon out with some Hoppe's? I can understand and have seen first hand the benefits that leaving some copper fouling in the barrel can do. Just curious, thanks.

 

[bigedp51]

You don't even clean some of the carbon out with some Hoppe's? I can understand and have seen first hand the benefits that leaving some copper fouling in the barrel can do. Just curious, thanks.

engineer40

The British military would pore at least 2 pints of boiling water down the bore after shooting their Enfield rifles. Then a pull through was used to pull a oiled cloth the length of the bore. This would remove the corrosive primer salts and the carbon, and it was up to the armourers when to remove any copper from the bore.

In Hemingway's "The Snows of Kilimanjaro" was the first I read about the boiling water to clean the bore when on safari.

With the advertising and all the bore cleaning products we tend to over clean our bores to the point of actually harming the the bore. As you can see less is more when it comes to bore cleaning. I have a bore gauge used on the Enfield rifle, if the gauge will not travel the length of the bore the Armourers would mix up a copper cleaning solution to remove the copper.

On my rifles I give the bore one shot of foam bore cleaner, flush it out with carb cleaner and then oil the bore. Meaning spare the cleaning rod and spoil the bore.

Below is a bore scope photo of a new Savage button rifled barrel and makes some of my pitted and frosted milsurp barrels look good. If you use a cleaning rod and a copper bore brush the "speed bumps" will eat the brush and give a false copper reading.

Below a custom hand lapped barrel as another example.

 

[dmax1800]

Latest update.
I thoroughly cleaned the bore with Bore Tech. It took 3 cleanings to get all the copper. Shot 2 groups and 2 mini ladder tests this morning. Cleaning seemed to help some. I got some holes that are 3 inches away and some holes that are in a 1/2 inch circle. Ladder test holes are not all stacked vertically. Some of the holes don't measure exactly round as if the bullets are wobbling. As discussed before they may not be stabilizing totally because of the temp. It was 26 degrees this morning.

Recall that this rifle with these bullets and powder would shoot 3/4" groups consistently when it was in the 50s and 60s.

Here is what I'm going to do unless someone has a better idea.
- check to make sure the action is not touching the stock somewhere it shouldn't be.
- use a target material that would make a clean entrance in order to see if the hole is exactly circular.
- if the action isn't touching and if the 55 gr shows any sign of wobble, get some 50 grain bullets that may stabilize better.

My question now is what can I use for a target material such that the bullet would a clean entrance so that I could measure the hole to see if it is perfectly round???

Many thanks in advance.

 

[dmax1800]

I checked the stock and there were 2 minor spots where the receiver was barely touching the bedding block. Sanded them out and the receiver doesn't touch the block were it shouldn't. HOWEVER, the rear tang (the triangle around the rear action screw) does NOT contact the bedding block. Plus the front of the receiver behind the recoil lug only contracts the aluminum block with 2 lines running lengthwise with the barrel and only about 1/8 inch wide. Seems to me that I need to bed the action. But even if the action is not bedded the way it should be, would that explain the groups opening up sometimes? Or is the bedding contributing to, but not causing the groups opening up???