Cold Bore Remedy

[Kren]

I have chronographed it several times, would have to look back in my notes which aren't right at my finger tips, but there was never anything that left me saying what the bleep happened there? Spreads always seemed close.

So what i am hearing is go shoot 5 shots, let it cool 5-10 minutes, shoot 5 more and see where it's at?

 

[Vern400]

If you're running all your groups through a chronograph, then your first shot should be substantially lower in velocity. It takes a significant change to screw up a powerful rifle at 100 yards. I'm going to step out on a limb and say if you're not running a chronograph, you cannot validate a great load at 100 yards. You can get by with things at a hundred yards that mess you up at 600. By this, I simply mean you may fail to observe the problem because of the short range. I chronographed a new load a few weeks ago that had an ES of 160 ft per second, and it still shot a 1-in group at 100. I changed powders and the ES went down to 26 in a 10 shot group. And it shot a 1-in group. I know which one I'll bet my money on at 400 yards!

Another thing to think about

The lighter your rifle is, and the harder it kicks, the harder it is to shoot well, and the more HOW you hold the rifle consistently every time matters. If I'm shooting with a big puffy Carhartt jacket on I have to be careful to pull the rifle in tight. If I'm just wearing a flannel shirt or a t-shirt, not so much to get the same POI.

If you are mixing terms, and your cold bore shot is also a clean bore shot, I'm going to say you better learn where first bullet is going, and send it accordingly. Because you ain't going to fix that. You can only anticipate it.

My rifles don't care much about Cold bore but they DO care very much about clean bore.

 

[PathFinder]

Shoot 3, ten shot groups without waiting between shots. Let it cool between the 10 shot groups. Then, do the same with the barrel allowed (or forced) to cool down to ambient temperature.
You'll find that the rifle shoots to the same cone/circle, if everything is working correctly.

 

[Harvey_NW]

There’s no advantage to shooting a single 10 shot group vs three three-shot groups or two two-five shot groups stacked on top of each other. It should be common sense, but gets repeated so often that 10 shots all at once is somehow giving better information.

No one ever said it was, it's the sample size of at least 10 that's important.

Shoot 3, ten shot groups without waiting between shots.

This aged well..

 

[Harvey_NW]

I have chronographed it several times, would have to look back in my notes which aren't right at my finger tips, but there was never anything that left me saying what the bleep happened there? Spreads always seemed close.

So what i am hearing is go shoot 5 shots, let it cool 5-10 minutes, shoot 5 more and see where it's at?

For the sake of your theory, note where the cold bore lands before shooting the group. But yes, then use the same POA and shoot at least a 10 shot group. 20 is better.

 

[PathFinder]

The idea is that it will reveal that there's zero difference between a warm and cold bore.

Sent from my SM-S901U using Tapatalk

 

[mxgsfmdpx]

I have chronographed it several times, would have to look back in my notes which aren't right at my finger tips, but there was never anything that left me saying what the bleep happened there? Spreads always seemed close.

So what i am hearing is go shoot 5 shots, let it cool 5-10 minutes, shoot 5 more and see where it's at?

What you need to hear is the following…

Understand the true accuracy of the gun, and you shooting the gun.

As I said, you’re going to land somewhere around 2 MOA, maybe a bit better, between you and the gun shooting 30 shots at a 1” target at 100 yards.

“SUB MOA ALL DAY” is not a thing for folks who see guns shot and shoot guns nearly daily.

Cherry picking 3 and 5 shot groups is not the way.

 

[nm.otter]

There’s no advantage to shooting a single 10 shot group vs three three-shot groups or two two-five shot groups stacked on top of each other. It should be common sense, but gets repeated so often that 10 shots all at once is somehow giving better information.

Time stacking difference should be nil, barring a poorly heat-treated or cut barrel.

There's a big advantage in not 'space stacking' ten shots on one target. A sheet of spots with 3-5 shots on each is significantly easier to measure off.

Do that at 200 yards and you get a representative cone of fire that's easier to accurately measure.

 

[TaperPin]

A 300 mag is no pussy cat in the recoil department. Not saying this is happening, but it happened to me one summer. I didn’t think recoil was an issue since the years before everything was working just fine, but every winter we tend to lose our recoil tolerance with time, and that spring I hadn’t shot big guns a lot, but enough I thought.

We tend to think of a flinch as tightening up the face while the eyes close, but that summer I learned any number of body parts can be tightening up. The good old technique of putting 5 dummy cartridges in a hat with one live one showed for whatever reason my hands and arms were clenching up anticipating the shot which increased groups something like 30%. Not huge, but enough to know something was different. Knowing what it was, made knowing what to focus on easier. Ever since then I’ve been more aware of tensing up the arms.

I’ve also been more aware of what other folks are doing at each shot, and not just looking for an eye flinch.

 

[wind gypsy]

There’s no advantage to shooting a single 10 shot group vs three three-shot groups or two two-five shot groups stacked on top of each other. It should be common sense, but gets repeated so often that 10 shots all at once is somehow giving better information.

Shooting a group without breaking position is more likely to result in tighter groups than breaking position and rebuilding it for each shot.

 

[NSI]

Shooting a group without breaking position is more likely to result in tighter groups than breaking position and rebuilding it for each shot.

This is particularly true if the shooter maintains their cheek weld the entire time, for parallax error reduction. But in the context of OP's group sizes posted, I don't think it'll show up.

-J

 

[The Harbor Master]

It continually fascinates me that folks are willing to burn diesel driving multiple times to the range, burn time posting on forums, and burn ammo shooting multiple small groups, but are simply unwilling to lie down on the ground to shoot a 10 round group ONCE and slip turrets ONCE, arriving at a definitive answer and a usable system within a box of ammo. This is bare minimum (and in my view STILL short of sufficient).

Don't clean the rifle. Don't mainline caffeine. Go back to the range. Double up your ear pro. Get low, get stable. Check your parallax. Then get more stable. Dry fire 20 times. Fire 10 rounds at whatever cadence you personally believe makes sense. If that's 10 minutes between shots so be it. Pretend you're shooting your bow - build pressure on the trigger slowly and do not allow bad shots.

I think a field rifle ought to be able to go 10 rounds without wandering, but my opinion doesn't matter here - just yours. Note the position of your first shot. Draw a circle around the whole group. Post it here. Then we can actually help you diagnose an issue, if there is one.

Love,
-J

Post of the day.

 

[khuber84]

Shoot a 10 shot zero. If the very first round is still 1" low to the 10 shot cone of fire, let rifle cool completely and repeat the test at 300-400y. If the cold bore is still 1" low of group this is not a problem, it's all lost in the noise. If the cold bore is now 3-4" low of the group, then there is a problem.

 

[TaperPin]

Shooting a group without breaking position is more likely to result in tighter groups than breaking position and rebuilding it for each shot.

Maybe. At hunting rifle accuracy levels I think that advantage is very over stated. Many of us wait minutes between shots at times, essentially breaking position every shot, and shoot more shots at once other times. If it made a difference on target me or the guys I shoot with don’t notice it, even on quite accurate rifles.

I don’t doubt that a person’s ability to get into a good position repeatably at shot one makes a noticeable difference, so our collective experience may not be representative of guys that shoot less with sloppy form.

 

[wapitibob]

Hey Guys,
I have a question for some of you out there that are way smarter than me when it comes to reloading/firearms.

I have a 300prc that I have been shooting and it is shooting extremely well, except for the cold bore shot. My first shot is consistently .75-1" low at 100 yards with this rifle. This has been true with a handful of different load recipes. I have 2 questions for you fellas.

1.) Is there a remedy for this?

2.) I bought this/set this up to be a long range hunting rifle. Right now, the cold bore shot equates to roughly .25mil low at a 100, so will this always be .25 mils low? So, if i am taking a shot at 500 on an elk is my cold bore shot gonna hit roughly 4" low, or would it likely come in the same 3/4" low as it does at a 100yds? I will be testing some more here this summer but was curious what you all think/know.

Lastly what causes cold bore issues? This gun has been impressive after "warming up" and i have many other rifles that have no difference at all on there cold bore shot. Just curious.

As always appreciate the advice.

After cleaning, swab the bore with lock-ease. It fixed my 1st shot issues, maybe it'll work for you. I'd also take my 1st shot of each range session at the max distances I plan to shoot when hunting.

 

[hibernation]

It continually fascinates me that folks are willing to burn diesel driving multiple times to the range, burn time posting on forums, and burn ammo shooting multiple small groups, but are simply unwilling to lie down on the ground to shoot a 10 round group ONCE and slip turrets ONCE, arriving at a definitive answer and a usable system within a box of ammo. This is bare minimum (and in my view STILL short of sufficient).

It took me awhile to get there, but this solved a lot of issues for me. Shoot more upfront, dial something in for sure, and then stop messing with it. Record the zero, check it periodically, and know what to actually expect from a rifle.

 

[HandgunHTR]

Let’s say his first shot is 150 FPS slower than his 3rd shot. What is your estimate on what that group looks like when a robot shoots the gun at 100 yards?

I would bet that they don't look that different from the others. I would guess that the slower round would impact somewhere around 0.05-0.1 mils off of the statistical center of the group, which honestly would be lost in the "noise".

To be perfectly honest, that part was my attempt to very passively state "the problem is most likely the shooter". When you come straight out and say that, it is almost always ignored because people don't want to hear that and aggressive positions usually provoke aggressive responses. So, you tell them to test this thing, knowing full well what the outcome will be, so that they can eliminate that excuse from there list of things that could be causing it, thereby getting them to think about the rest of your response. That is why the majority of my answer focused on how first round recoil expectation can cause first round impacts outside of the norm.