Sniper Country Duty Roster collective wisdom


Cold Bore Shot:


Gooch, Rick, et al: how much difference do you notice in the cold bore shot? I'm regularly getting the cold bore shot in my rifle about 1/2 to 1 MOA up and right (about 2 o'clock) from the rest of the group. Is this common, and how much do you have to account for it on an op?
 
Bach Melick <tmelick@monbar.com>
New Orleans, LA USA - Monday, October 12, 1998 at 11:29:02 (EDT)


1) Usually how much difference is there between the cold bore shot and the rest of the shots?

Bach Melick <tmelick@monbar.com>
New Orleans, LA USA - Thursday, October 15, 1998 at 11:45:50 (EDT) 


Cold bore shots. In my experience it depends on the gun. I have found that relitively new barrels show less effect than ones that are near being shot out. A good way to prevent this is to fire fouling shots out of a freshly cleaned bore.

The best way to predict the effects of a cold bore is just like a lot of other things. Shoot a lot and keep a good data book and analyze it for trends.

Gooch
 
gooch <kdgooch@aol.com>
Sherwood, AR USA - Thursday, October 15, 1998 at 13:05:34 (EDT) 


Melick - Cold Bore shots are more pronounced with the gas guns than the bolt guns. On the bolt guns it becomes more pronounced with bore burn out as indicated by Gooch. As a matter of interest, it is a good indicator that your bore is becoming worn and you need a new barrel. This will show before thrown flyers. On gas guns you can reduce the cold bore change by manipulating the bolt rapidly and taking most of the spring set out of the weapon. However you will never "lock up" the bolt the same way the gas does it, so change is inevitable.

Rick <RBowcher@aol.com>
Fayetteville, NC USA - Thursday, October 15, 1998 at 21:55:12 (EDT) 


Re: First shot out of clean cold bore.

My experience is shooting a couple of 1000 yd. matches at Camp Perry per year. This is a semi-controlled
environment. My Wimbledon gun is a Hall actioned, Hart barreled (1:12 twist, fluted), .300 Win. Mag. chambered
(tight neck), McMillan prone stocked, Jewel 1.5 oz. triggered, Hammond's built prone rifle. A very solid HONEST
10-shot ½ moa rifle. Day in, day out. Notice that I specified 10-shot groups. Ten-shot groups are not lucky,
occasional groups, but repeatable ones.

My experience over the years is that (with this rifle) the first shot will be about 24 to 30 inches low at 1000 yds. The
next will come up about a 12 inches. The next will come up about 6 inches or so, etc. Obviously, I do not correct on
the first shot anymore, but wait until the barrel heats up (stabilizes). The cold barrel absorbs a lot of heat, and heat
equals pressure.

As an aside, another rifle my put its first shot high because of "compensation". It is well known that in some rifles
a lower velocity shot may actually shoot higher on target than a higher velocity shot. In short, this is due to barrel
vibrations, etc. I've read that in the M14 that this is so at 800 yards. This rifle has a sweet spot to where velocity
variations cancel themselves out and the target will show less "vertical" at this range compared to 700 yds. and
900 yds.. Just how much I don't know. I've read it, but don't want to look it up.

Just passing along info to be stuck WAY back in your mind. Pull it out when you need an excuse. I do.

That's all for now.

Ron N. <rnosack@accnorwalk.com>
Ohio USA - Thursday, October 15, 1998 at 22:45:56 (EDT)


Have read "cold bore shots" and the poop on cleaning. Here's the question:
After let's say a military or SWAT sniper cleans his weapon after range time, how can he be sure of shot placement on the cold bore shot? Do duty slotted snipes fire a fouling shot after cleaning or are they guessing at where the first shot is going to land?
Having only hunted at realitively short distances, I have never really thought about fouling shots perty much knowing that up to 200 yards the bullet will be in the vital with the old 30-06. Now that I am more aware, I ponder which to do; sight the rifle in based on the first shot out of a clean bore instead of the group, or sight in for a dirty bore shot. The problem is that one may not want to disturb the four legged critters at 4 in the morning with a fouling shot.

Mike Bolt <mbolt34547@aol.com>
W-S, NC USA - Sunday, November 08, 1998 at 12:22:35 (EST) 


Mike; There are a couple of ways to work with the first shot out of a CC barrel. First, if your (lucky) and/or your equiptment is good that first shot will either be close, 1/2 moa "consistantly" or shoot to the same spot (though not on x). This is probably good enough for most to hold over out to 400 or maybe 500 for a body hit. With LE apparently it is not as much of a problem as much of the shooting is closer range.

A civilian on the other hand is not bound by regulations and inspections and probably has a little more freedom when it comes to answering to no one but yourself. So a lot of people leave the bore fouled during hunting season or before a match. If you shoot regularly the problem is not as sever with cleaning every other time and fouling before you leave range. My wife thinks I am leaving her everytime I go to the range because I take more with me for that as when we go on vacation. But accually it only takes bringing a rod with you, a couple of patches and some cleaning solution. A couple of wipes and you are good to foul one before you leave.

Something I noticed the other day in a catolog was Moly Prep. It was something (solution?) that you patched a clean barrel with that is supposed to reduce or eliminate the need to foul (whatever that means). I have not tried this product so cannot vouch for it.

Got a little long winded, so I'll end here.

Pictures <billmohr@borg.com>
Somewhere, Ny USA - Sunday, November 08, 1998 at 18:49:36 (EST) 



I am primarily a handgun person, so I have two quick questions....

COLD-BORE Zero: I have a customized AR-15 that is set up for urban Counter-Sniper work. The gun prints beautiful (1/2 MOA)groups after a couple of fouling shots, but the cold-bore zero is about 1 MOA RIGHT of the rest of the group. This is very consistent. On "picture targets", the first round will be on the center of the left eye (perps left, shooter's right) and the next 4 will be perfectly clustered in between the eyes. This is driving me nuts. I was expecting a vertical error, but a horizontal one?

Thanks.

Bruce Braxton
College Park (GA) P.D.
Bruce Braxton <Braxton1@aol.com>
College Park, GA USA - Wednesday, December 09, 1998 at 20:06:13 (EST) 



Bruce (College Park) I am going to take a stab in the dark here. This is probably wrong, but worth looking into. Is your barrel free floated? If not, what you could be seeing is the relaxation of your hold after the first shot. If you are applying a lot of pressure on the barrel via sling, or bi-pod, it could theoretically change this much in point of impact. But I got to say I am reaching for straws here! Under this idea, you'd probably not group as well as you are. There is some talk that the first round chambered into a semi-auto will shoot out of the group as it is not fed into the chamber with the same speed and action as the following shots fed under the power of the operating system. Supposedly this can change POI. I have not seen this much in my AR though.

Scott <Xring@voicenet.com>
USA - Thursday, December 10, 1998 at 15:57:22 (EST) 



Bruce Braxton - My guess is that the bolt is not locking up the same with a manual locked and loaded round and once the weapon fires it locks up enough differently that the zero shifts. Another question would be how long is the weapon stored between shoots. A semi stored for any length of time will take a spring set that changes with the first round fired. Try operating the bolt vigorously several times before shooting and see if that reduces the amount of the difference in the shots. Those were the primary causes of the shift in that old M21 that I bombed on Gramps about. Where the round goes will depend on a number of factors and the twist that the AR has in its bolt head inside of the bolt carrier may have something to do with it. That was a wild assed guess by the way!

Rick <RBowcher@aol.com>
Fayetteville, NC USA - Thursday, December 10, 1998 at 17:16:55 (EST) 



Scott; I think you have brought up something about the sling pulling it a bit. The AR can be moved a small amount with improper application of the sling. This isn't apparent to GI's who don't hold or at least don't know how to measure in .5 minute increments. I have a fairly good AR that can be bothered in such a manner. I have often wanted to ask if anyone has had trouble with rifles when the sling is tightened against the length of the rifle. Obviously the problem is more pronounced with some types of rifles and stocks but I do think it is a factor. A bit hard to measure without using sandbags with and without sling to see where the groups go. A better way might be to put in a boresighter and zero it. Then sling up in your best position and see how far the cross hair has moved. This would tell us more about the affect because bench or sling positions might vary the impact point on it's own not to mention the tight sling. If the barrel is not free floated prepare for a real surprise.
B.Rogers <brogers@elkhart.com>
USA - Thursday, December 10, 1998 at 20:51:30 (EST) 

B.Rogers: On AR barrels. As you mentioned, Sling tension on an AR can really effect it. The old M16 and M16A1 were very susceptible to this as their barrel was pencil thin. The M16A2 ainít much better as the barrel is equally thin under the handguard. Happily it doesnít matter as very few GIs bother with the sling in an actual fur ball. I can not think of any I knew who used it for more than a method of toting the weapon occasionally and most didnít even use it for that! At least not in any training I even attended. Nice thing about a light rifle is that you can have it always ready to employ with little distress to the body.

Anyway, the heavy barreled competition ARs are much less effected by sling tension but they still change POI. I think mine would pull about 1.5 MOA @ 300 Yards if I cinched in real tight. To avoid this I usually left the sling only tight enough to absorb what muzzle rise there was during rapid fire. For competition, free floating is the answer but not a must depending on your goals. A new shooter need not concern himself with it as long as his zeros are recorder with the sling on. Once they start getting good and shooting in the mid to high 700s they may want to float the barrel to stay competitive.
 
Scott <xring@voicent.com>
Anytime, Anywhere USA - Friday, December 11, 1998 at 11:36:26 (EST) 



Gentlemen:

Re: The AR-15 Counter-Sniper gun that shoots 1.5 MOA Right on "Cold-Bore Shot"....

Slings are not an issue. I don't use one normally. This was first noticed on a bipod front/bagged rear setup.

The barrel is free-floated, also.

About the only solution that I could find was to fire two "fouling" shots and (EGAD!!!) store the gun dirty. I could handle a small variance in elevation based on "cold-bore", but this windage thing is a pain in the arse.

Bruce Braxton <Braxton1@aol.com>
College Park, GA USA - Saturday, December 12, 1998 at 03:43:13 (EST) 


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