Hot Barrel Accuracy

[WoolSocks]

Hello. Took my new (to me) browning x-bolt 300 prc to the range today. First three groups of 3 were great, sub MOA, if not a little better. After those 9 shots, the groups opened up to 3 MOA or so. I stopped shooting at 20 rounds cause it wasn’t getting any better.

Is is typical? The barrel is floated and fluted. which I thought would help with the hot barrel inaccuracy.

[Fidelk]

Not any kind of expert but how long between shots? When I'm shooting from a bench rest and going after a tight group, I use a watch and wait 2 minutes or more between shots to allow a bit of cooling. Good news is when hunting, your most effective shot should be coming out of a cold barrel.

[WoolSocks]

Probably 1-2 min between shots. I take my time when sighting in.

Did check the barrel after 15 rounds or so. It was pretty hot. Not hot enough to burn ya, but on the edge of uncomfortable to keep your hand on.

[Fidelk]

I feel my barrel (Rem 700 Long Range, .300 Win Mag.....bull barrel) when sighting in to see how warm it is.......you are describing a much hotter barrel than I have encountered. Why not try another range session and time 5 minutes between shots. To be scientific about it, if you expanded the cool down time, you should see how 3 x 3 shots compare to your first groups.......then shoot a couple more 3 shot groups. If they don't open up, then heat might be the main factor. The 3 sub-MOA groups is a positive sign.

Is the .300 PRC known to shoot "hot"? Does it have a lot of recoil and could that have you anticipating it enough to open up those groups after a certain number of rounds have been fired?

Again, no expert.......I just go with trial and error. My first outing with my Rem 700, I couldn't even find any holes in the target......someone took pity on me and loaned me a large piece of white cardboard.......my scope was way out of whack.   

[JimmyHoffa]

Copper fouling?

[wheels1]

Prc can be a toasty round  wouldn't shoot more then 5  rounds with 2 to 3 minute break

[Bob33]

Do the same test another day. If the first three groups are good then barrel heat is the likely culprit. If the first group from a cold barrel is 3 MOA then thoroughly clean the barrel, come back another day and try again.

[buckfvr]

  If its your new hunt rifle, first 2 shots same hole or as close as you can get.  Third shot will be starting to move on you, I do 5 minutes between shots when dialing in and checking loads.  If its hot out, even longer.  Between groups, you must let the barrel cool down all the way.  That rifle should do better than moa if you handload or use premium ammo.

[KNOPHISH]

Add the hot weather and it takes longer to cool down. Bring multiple guns to range and switch after a few shots so you don’t have to sit around waiting.

[boneaddict]

The only other thing might be a screw coming loose on a scope mount?   

[boneaddict]

This is the one that always got me...

ot any kind of expert but how long between shots? When I'm shooting from a bench rest and going after a tight group, I use a watch and wait 2 minutes or more between shots to allow a bit of cooling. Good news is when hunting, your most effective shot should be coming out of a cold barrel.
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My DAD always fouled the barrel when we got on the range to shoot for accuracy or when working up loads.  I always thought to myself, well, I have a cold cleaned barrel when I was putting a drop on something downrange.........

[Farmer72]

This is the one that always got me...

ot any kind of expert but how long between shots? When I'm shooting from a bench rest and going after a tight group, I use a watch and wait 2 minutes or more between shots to allow a bit of cooling. Good news is when hunting, your most effective shot should be coming out of a cold barrel.
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My DAD always fouled the barrel when we got on the range to shoot for accuracy or when working up loads.  I always thought to myself, well, I have a cold cleaned barrel when I was putting a drop on something downrange.........

I never had a clean barrel when I was rifle hunting. I always shot a fouling round or 2 before we left for a trip.

[OltHunter]

Hello. Took my new (to me) browning x-bolt 300 prc to the range today. First three groups of 3 were great, sub MOA, if not a little better. After those 9 shots, the groups opened up to 3 MOA or so. I stopped shooting at 20 rounds cause it wasn’t getting any better.

Is is typical? The barrel is floated and fluted. which I thought would help with the hot barrel inaccuracy.

Hot barrels due decrease accuracy. From sub to 3 moa, not sure. Might be something loose.

But hunting, big taper, thin barrels do not maintain accuracy as they heat up. 3 shot strings, with full cool between strings is the best way to figure out accuracy at the range. That equals long range trips.

The thicker the barrel, the more you can shoot in a row without an effect.

[dreadi]

At 25yds, 100yds, 300yds, 600yds?
Did you check your base and rings torque between groups?
Were you changing positions? Did you have the rifle locked into a rest?
Could you clearly see the target or was it like a mirage?
Were you getting tired? Shooting in direct sun, getting hot and uncomfortable?

There’s so many factors that have to come together. The only way to get as close to a conclusion is to eliminate as many variables as possible and keep the shooting as consistent as possible.

9 sub MOA shots sounds like a good shoot to me when you’re past and well past 100yds.


BLACK HAMMER ARMS
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[Fidelk]

This is the one that always got me...

ot any kind of expert but how long between shots? When I'm shooting from a bench rest and going after a tight group, I use a watch and wait 2 minutes or more between shots to allow a bit of cooling. Good news is when hunting, your most effective shot should be coming out of a cold barrel.
Modify message

My DAD always fouled the barrel when we got on the range to shoot for accuracy or when working up loads.  I always thought to myself, well, I have a cold cleaned barrel when I was putting a drop on something downrange.........

I never had a clean barrel when I was rifle hunting. I always shot a fouling round or 2 before we left for a trip.

I've always heard that you NEED to fire a round if you've cleaned your barrel and have used any oil or solvent. Fire a round and that gets burned out of there. If I clean a barrel close to a hunting trip, I'll only use a dry patch.

[Karl Blanchard]

Question for OP, if you took those 3 seperate groups that were all sub moa and laid them on top of each other what would that 9 shot group look like?

[hunter399]

This is the one that always got me...

ot any kind of expert but how long between shots? When I'm shooting from a bench rest and going after a tight group, I use a watch and wait 2 minutes or more between shots to allow a bit of cooling. Good news is when hunting, your most effective shot should be coming out of a cold barrel.
Modify message

My DAD always fouled the barrel when we got on the range to shoot for accuracy or when working up loads.  I always thought to myself, well, I have a cold cleaned barrel when I was putting a drop on something downrange.........

I never had a clean barrel when I was rifle hunting. I always shot a fouling round or 2 before we left for a trip.

I've always heard that you NEED to fire a round if you've cleaned your barrel and have used any oil or solvent. Fire a round and that gets burned out of there. If I clean a barrel close to a hunting trip, I'll only use a dry patch.

Everybody always does it different.
I've always got 10- 20 rounds dirty.
Clean it ,final sight in,which was a week ago.
Then I don't touch it till season.
I want a fouled,slightly dirty barrel ,I want it to shoot like my last shot on sight in.

Range trip I do take three rifles,hot weather like now ,I don't shoot more than three shots before I let it cool.

One other thing I like to check,on a different day than range day is. Cold bore shot. Your first cold bore shot is the only one I care about. If it turns into a 2 moa gun on hot barrel ,that doesn't bother me. My most important is the cold bore accuracy.

20 rounds dirty barrel doesn't bother me.
After 50 rounds I like to clean.

Like said everybody does it different.
You have to find your process.

[Stein]

Question for OP, if you took those 3 seperate groups that were all sub moa and laid them on top of each other would would that 9 shot group look like?

 

3 shot groups do not provide any value statistically.

I would load 20 rounds.  Shoot the first 10 shot group real slow, I wait 3 minutes between each shot or use a barrel fan.  Second group shoot all 10 as fast as you can get 100% good shots.

[fishngamereaper]

Barrel heat maybe
 Although I've shot several comps before that required 10-20 round rapid succession target engagements...
No issues with heat affecting poa/ poi...(quality barrel though)
Fouling/ cheap ammo would be more likely.
And flinching would be another.
Have a buddy blind load (or not load) your rifle after 5-6 rounds and see what you do.
Sometimes after a few rounds the body naturally flinches. You won't notice it until you press the trigger on an empty chamber...
Anyway..

[WoolSocks]

Question for OP, if you took those 3 seperate groups that were all sub moa and laid them on top of each other what would that 9 shot group look like?

Here’s the target with the 1st-5th groups labeled. 2nd and 3rd groups have 2 of the 3 rounds through the same hole. 4th and 5th get progressively worse. 5th group has 4 rounds.

Did some adjusting during this, so look at the groups, but disregard their location relitive to the red dot bullseyes.

[WoolSocks]

At 25yds, 100yds, 300yds, 600yds?
Did you check your base and rings torque between groups?
Were you changing positions? Did you have the rifle locked into a rest?
Could you clearly see the target or was it like a mirage?
Were you getting tired? Shooting in direct sun, getting hot and uncomfortable?

There’s so many factors that have to come together. The only way to get as close to a conclusion is to eliminate as many variables as possible and keep the shooting as consistent as possible.

9 sub MOA shots sounds like a good shoot to me when you’re past and well past 100yds.


BLACK HAMMER ARMS
07/02 NFA Dealer

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I did check the base and rings a few times. Everything kept tight to vortex torque specs.

Shooting eld-x ammo at 100 yards.

There was a “mirage” effect, with the heat radiating up from the ground. Still had a clear view of the bullseye though.

[Buckjunkie]

You have a problem. You should expect good groups hitting the same impact point, not walking around the target.

Temp can make a difference, but if it’s more than a one MOA from group to group, you need a new load…or work done on the rifle.

I shoot two fowlers with a clean barrel, 5-10 if I have stripped copper.

I wait until the barrel is cool to the touch between groups. Easier when it’s 40 than 70-80. I don’t work up loads when it’s hot.

Check, the scope stick screws… make sure your rest is solid. I don’t care for lead sleds and I remove the front sling swivel when shooting on a bag. I prefer free recoil.

Most of my rifles like a carbon free barrel, but all need to be fowlers to shoot their best. If you strip copper, make sure you shoot 5-10 rounds before working up loads. All this is assuming you are shooting cup and core bullets. If you shoot mono’s, the recipe changes.

[JWBINX]

Maybe a little shooter fatigue?

[yogru]

I shoot a Browning A-bolt (predecessor) and have always noticed the same thing.  My barrel heats up and the groupings get all wonky.  A few years ago I bought this plastic barrel fan you put the nose in your chamber and turn on the mini fan and it cools the thing down in a hurry.  Had much better luck getting groupings since.   I see amazon has something resembling mine called a "chamber chiller" but mine just uses a AA batery and cost like $15.  Can't recall exactly where i got it.

[huntnfmly]

Maybe a little shooter fatigue?

You just beat me to it a little fatigued and hurrying and flinching

[fishngamereaper]

Try different ammo
I haven't had much luck with eldx groups...
Eldm shoots much better for me.

[WoolSocks]

You have a problem. You should expect good groups hitting the same impact point, not walking around the target.

Temp can make a difference, but if it’s more than a one MOA from group to group, you need a new load…or work done on the rifle.

I shoot two fowlers with a clean barrel, 5-10 if I have stripped copper.

I wait until the barrel is cool to the touch between groups. Easier when it’s 40 than 70-80. I don’t work up loads when it’s hot.

Check, the scope stick screws… make sure your rest is solid. I don’t care for lead sleds and I remove the front sling swivel when shooting on a bag. I prefer free recoil.

Most of my rifles like a carbon free barrel, but all need to be fowlers to shoot their best. If you strip copper, make sure you shoot 5-10 rounds before working up loads. All this is assuming you are shooting cup and core bullets. If you shoot mono’s, the recipe changes.

I don’t think it’s “walking around” - I was trying to site in, so you’re seeing groups in different places as I make adjustments.

Interesting notes on “Fowlers” have never heard that before, but I guess it makes sense. You can’t swab every bit of oil out.

[WoolSocks]

I shoot a Browning A-bolt (predecessor) and have always noticed the same thing.  My barrel heats up and the groupings get all wonky.  A few years ago I bought this plastic barrel fan you put the nose in your chamber and turn on the mini fan and it cools the thing down in a hurry.  Had much better luck getting groupings since.   I see amazon has something resembling mine called a "chamber chiller" but mine just uses a AA batery and cost like $15.  Can't recall exactly where i got it.

This is good to know. I’ll get a fan. As I mentioned before, the barrel got HOT by that last round, even though I was waiting several minutes between shots. Hot enough to be uncomfortable to touch.

My main question here is if the floated barrel should mitigate hot barrel inaccuracy, but maybe it only partially does. It’s a 300prc, and the barrel isn’t particularly heavy. Perhaps a floated barrel only does so much..

Not ruling out recoil flinch, but this thing doesn’t kick much with the muzzle break. It’s a real pleasure to shoot, except that you have to get a second mortgage to buy ammo. .

Will try some cold groups and report back.

[idaho guy]

 I don’t think that’s a hot barrel issue. I agree an easy test would be to just shoot a new group with a cold barrel taking a few minutes between shots. My experience is my first round from a newly cleaned barrel is often a flyer. Once I break a barrel in and get it shooting I won’t clean it again until I notice it’s not shooting well. There’s lots of theories on cleaning guns and accuracy but leaving them alone has worked well for me. People tell me they have great luck with vortex scopes. My experience with vortex rifle scopes is not good and I had a similar issue with my 28 Nosler with a vortex scope. Tight group but as I tried to dial the scope to zero, the groups got larger and wild. I replaced with leupold and fixed issue. I just wanted to mainly mention the scope issue as your target gave me a little deja vu. Not wanting to beat up on vortex’s but that looks very similar. If your cold bore shots don’t group I would definitely look at the optics.

[jaymark6655]

If you can put your hand on it, it is not a hot barrel issue.

I would check scope base screws, scope rings screws, and action screws.

In one rare case I had a bad scope and reticle was moving with each shot.

From there, if it were me, I would start wondering if it was me or the ammo.

Maybe its fouled barrel, but I can't imagine 15 rounds being too many between cleanings.

[Stein]

Another option would be to send the scope back and have it looked at.  You have time until fall and it would be good to at least have that checked off the list.  Sounds like you have a Vortex?  They turn those around pretty quickly in my experience.

[Fidelk]

I shoot a Browning A-bolt (predecessor) and have always noticed the same thing.  My barrel heats up and the groupings get all wonky.  A few years ago I bought this plastic barrel fan you put the nose in your chamber and turn on the mini fan and it cools the thing down in a hurry.  Had much better luck getting groupings since.   I see amazon has something resembling mine called a "chamber chiller" but mine just uses a AA batery and cost like $15.  Can't recall exactly where i got it.

This is good to know. I’ll get a fan. As I mentioned before, the barrel got HOT by that last round, even though I was waiting several minutes between shots. Hot enough to be uncomfortable to touch.

My main question here is if the floated barrel should mitigate hot barrel inaccuracy, but maybe it only partially does. It’s a 300prc, and the barrel isn’t particularly heavy. Perhaps a floated barrel only does so much..

Not ruling out recoil flinch, but this thing doesn’t kick much with the muzzle break. It’s a real pleasure to shoot, except that you have to get a second mortgage to buy ammo. .

Will try some cold groups and report back.

If you had stopped after the first three sub-MOA groups, you wouldn't be thinking that you have a problem. You posted that the barrel got "HOT" (which you spelled in capital letters).......I believe you. I'm still guessing that it is heat caused. Try with the fan, etc......but wait 5 minutes between shots (or as long as it takes until you feel that heat diminish) and go past the first three groups of three. Last time the first 9 shots were tight......then they opened up with shots 10 through 15. To truly compare and determine if there is a difference, repeat the 5 groups of 3 and wait the 5 or more minutes between shots.

Don't be distracted with the fluted/free floated barrel......that's what you have and you are trying to work with what you have.

[Karl Blanchard]

If I were you, this is what I would do....

1. Thoroughly clean out all carbon and copper. A virgin barrel fouls fast as it strips out all the chamber imperfections. After that initial scrubbing I never clean a rifle until accuracy degrades. That could be a few hundred or never, depending on the caliber/powder/etc.


2. Go back through your rings and bases and make sure everything is properly torqued.

3. Shoot a slow min 5 shot group. 10 is even better. 3 shot groups are basically pointless. I've shot a lot of really small 3 shot groups but when you stack them all together you realize your quarter minute rifle is more like an moa rifle. Don't touch your dials until you've printed at least 10, then zero off that group.

Where heat can get you is that powder heating heating up in a hot chamber. Some powders are temp sensitive. Like north of 1fps per degree of temp. So if that chamber is hot you're gonna get wild velocity spreads.

[buckfvr]

Put another shooter behind the scope.

[Fidelk]

Put another shooter behind the scope.

That would be a useful verification/comparison. I would still recommend repeating the original session (5 x 3 shots) WITH added wait times to possibly rule out heat as the main factor. Then follow with another shooter doing the same thing......to expand the test, if desired.

If the added wait times result in five 3 shot tight groups.......for WoolSocks and/or the other shooter......it would be logical to assume that HEAT was the issue, especially since the OP has mentioned that the barrel was HOT to the touch.

[okie john]

There was a “mirage” effect, with the heat radiating up from the ground. Still had a clear view of the bullseye though.

I grew up in the long range target-shooting (Palma, F-Class, NRA Service Rifle, etc.) world. I'd bet this is your issue. Mirage will definitely open up groups in any rifle. That's why long-range target shooters use a mirage shield, which looks like this:

https://bulletin.accurateshooter.com/tag/mirage-shield/

There's no need to put one on a hunting rifle. But as others have said, once you fire a group, let the barrel cool down until you can touch it without discomfort. Mirage will seem to disappear before this, but it's still there--you just can't see it.

I do most of my load development work in cool weather because barrels cool down more quickly. A sporter-weight 308 like the Remington 700 will usually make two or three 3-shot groups before mirage becomes a factor. A similar 30-06 will make one or two groups unless I use a hot-burning powder like N560, in which case I need to let it cool after each 3-shot group.

There are lots of ways to cool a barrel: blow air through the bore with a scuba tank or compressor, use ice packs, or build one of the field-expedient chillers you can find online and on YouTube. Shooters in Arizona and other desert states are experts at this.

I use this one: https://magnetospeed.com/products-riflekuhl The only thing I don't like is that it eats batteries like a fat kid eats cake.

Without a cooler, take the bolt out of your rifle and let it sit on the bench with the muzzle up at about a 30-45 degree angle. It will cool faster than if you leave it horizontal or vertical, or if you leave the bolt in place.


Okie John

[WoolSocks]

[/quote]

I grew up in the long range target-shooting (Palma, F-Class, NRA Service Rifle, etc.) world. I'd bet this is your issue. Mirage will definitely open up groups in any rifle. That's why long-range target shooters use a mirage shield, which looks like this:

https://bulletin.accurateshooter.com/tag/mirage-shield/

There's no need to put one on a hunting rifle. But as others have said, once you fire a group, let the barrel cool down until you can touch it without discomfort. Mirage will seem to disappear before this, but it's still there--you just can't see it.
[/quote]

Fascinating. So is the optical effect of the mirage the problem, or is the mirage just an indication of a too-hot barrel?

[jaymark6655]

I would say just the mirage itself. It bends the light, so the target could look clear or be just a little bit blurry, but the position of the actual target and the image of the target could be in different spots.

While mirage is an indicator that the barrel is getting hot, usually if you can hold onto, it isn't too hot. Also, other conditions can cause mirage, like the sun heating the ground between you and the target, especially if there are different surface that absorb sunlight at different rates. Example: Shooting across a paved road that might be used to travel to target location on larger/longer shooting ranges.

Example: Light hits target, it is reflected toward the scope. As the light passes through the air above the barrel, the heat causes difference in air refractive index, this difference refracts light just before enter scope. Just like fish in water being in a different location than we observe, just on a smaller scale because the air transition is more similar than the water to air transition.

[okie john]

Fascinating. So is the optical effect of the mirage the problem, or is the mirage just an indication of a too-hot barrel?

Both.

The optical effect will definitely open up your groups. A hot barrel can shift point of impact, but the heavier your barrel and the more precisely your rifle is built the less of an issue it is. Palma shooters fire unlimited sighters and 15 rounds for record in 22 minutes. They start at 800 yards, move to 900 yards, and finish at 1,000 yards. POI on those guns either doesn't shift or they've graphed it so that it's predictable.

But they all use mirage shields...


Okie John

[buckfvr]

Being able to "hold on to" the barrel to sense the temperature is NOT an indication of the temperature at the throat of the chamber where damage will occur first.

[Bushcraft]

Clean the barrel, chamber, and all aspects of the fire control group.  Use a bore scope for chamber and barrel.  Cleaning a rifle without one is an exercise in fooling yourself and is giant waste of time.

Make certain that the contact areas between action and stock are absolutely clean and dry.  Snug action and all scope related screws/fixtures to torque specs.

Shoot at least 5-10 rounds to "foul" the barrel and stabilize velocities.  Note how the velocities and impact locations of these shots.

Then, shoot 10 consecutive rounds with the exact same point of aim, with a different point of impact (so that you're not blowing a hole or obscuring your POA).

The 300 PRC generates a lot of heat that's absorbed by your barrel.  The thinner the barrel, the faster it's going to heat up.  Heat sometimes does funny things to metallurgy.  You'll need to be doing this early in the cooler part of the day and time.  Make certain you engage your rifle IDENTICALLY every time you shoot.  Do a lot of dry-firing. If you can have a buddy load dummy or live rounds while you shoot to expose a flinching problem...so much the better.  It sounds like you have a lighter weight rifle system, which can be more difficult to shoot to the same POI consistently.

If you run into the same issues, try changing out scopes for one that isn't going to puke its guts out from a heavy recoiling rifle.  Finally...sorry to say it, but outside of their highest end models, most Vortex scopes are entry level garbage that just don't hold up over time.

[jaymark6655]

Being able to "hold on to" the barrel to sense the temperature is NOT an indication of the temperature at the throat of the chamber where damage will occur first.

Agreed, especially if the heat hasn't had time to spread out of those areas. Even if you shoot one shot a day vs 10 rounds a day, the throat is still going to be damaged to almost the same extent per shot, it will just take 10 times as long to see that damage. If you really get the barrel hot, ie can't hold it just in front of the chamber or scope, then the cracking and erosion can occur much faster depending on how hot you get it.

For me a barrel isn't considered hot until it hits 165, which takes quite a few magazines of .300 WM fired roughly every 30 seconds and then I won't shoot until its cooled to about 125 or were I can hold my hand on the barrel without feeling any discomfort. Rifle doesn't really have a target barrel on it, but isn't a lightweight hunting rifle either. I haven't seen any groups really open up due to heat when mirage is mitigated or eliminated by firing from a fixture with shooter completely removed from the loop and no adjustments after initial aiming before a group is fired.

[WoolSocks]

Hot barrel was the culprit. I lapped the rings and cleaned it thoroughly to make sure. Took it to the range and consistently found on the third round with 2 minutes between shots the barrel was hot to the touch and started throwing fliers. Progressively worse with 4th and 5th rounds.

Switched to doing 2 shots at a go and 5 minute rest with a cooling fan. Put 6 shots in a .5MOA group. Looks like a thin-barreled 300prc just gets hot fast.

[Fidelk]

You have a good one.