Advanced Marksmanship Mirage from Barrel Heat

[BamaAl]

This is probably a pretty obvious thing but I wanted to ask if what I think I saw is really what I saw.

I have been thinking about shooting in a 200 yard high power precision match this weekend so Sunday I went to the range to practice. I thought the match description (target sizes) seemed a little easy but after what happened Sunday now I think it is actually pretty challenging and just appears relatively easy if you don't know any better (like me). I'm used to shooting slowly. About 20 rounds in 30 minutes. But this match is 30 rounds in 20 minutes. Low and behold after about 10-12 rounds my POI starts moving all over the place. Well, maybe not all over the place but anywhere within about 1 moa of my POA. I also noticed that the mirage seemed to be very very heavy and it shouldn't have been given the conditions. In fact, the mirage was heavier than I have experienced before, to the point I couldn't see the target clearly, and it seemed to get worse the more I shot. The same thing happened on the second 30 round series.

So my question is this. Does this sound like mirage caused by heat from the barrel and could that cause the POI shift I saw? I should mention that I shot the 30 rounds in about 15 minutes so heat dissipation was even less.

 

[ShtrRdy]

Re: Mirage from Barrel Heat

I've noticed mirage grow when I shoot a string of shots. It's certainly possible that this was causing you POI shift. But it's also possible that your rifle is shifting your POI. Maybe you can try using a mirage shield over your barrel to sort it out?

 

[BamaAl]

Re: Mirage from Barrel Heat

I picked one up already. I just never used t because I never actually experienced mirage frm barrel heat before and didn't see the need. Learn something new every time I go to the range. Lol

 

[memilanuk]

Re: Mirage from Barrel Heat

Sounds pretty much exactly like barrel heat induced mirage. The mirage band work (I don't keep one on my match rifle because it looks nifty...) but if you don't have one, or like me, happened to grab a rifle and forget the mirage band... here's a little field-expedient trick that might help.

Take a deep breath, and exhale steadily, blowing down the side of the rifle across the receiver and barrel. Now look through the scope... you should see the mirage (from the barrel) is gone, or at least greatly diminished, for about 5-10 seconds before the air currents settle back to normal.

It is entirely possible to give yourself an extra shot or two after the barrel heat starts becoming a problem with this technique. Generally I don't recommend huffing and puffing while trying to make a precision shot... but if its the difference between getting one last shot off or pack it up and go home, its worth a try.

YMMV,

Monte

 

[Lowlight]

Re: Mirage from Barrel Heat

what magnification are you shooting this on ?

 

[coldboremiracle]

Re: Mirage from Barrel Heat

I have experienced the same thing, and with a suppressor it is even worse. I like the suggestion above to blow down the length of the rifle, I have also done similar by "wagging" the rifle left and right just prior to the shot to break up the heat waves just long enough to make the shot. Not sure which is better, but give it a try.

ETA: LL makes a good point as well, using a lower magnification may decrease the effect somewhat as well.

 

[Guest]

Re: Mirage from Barrel Heat

You will notice that problem faster in cool weather, but it's telling you to drop the scope power. Most shooters over glass/power targets the bulk of the time. The only reason to have a high power scope on a tactical rifle is for target detection when you don't tote a spotting scope. For a one way, portable fans, mirage bands/tubes an can covers will allow high powered glass to work. Try shooting with less power, you might find your on target performance is better.

 

[BamaAl]

Re: Mirage from Barrel Heat

I didn't think of dropping the power. The magnification was set at 25. I'll try the lower power this weekend and try the barrel shield too.

Just another trick learned. They seem to be multiplying like rabbits.

 

[Greg Langelius *]

Re: Mirage from Barrel Heat

Try rolling black construction paper into a tube of slightly (maybe 1/4") larger diameter than the scope's objective, about as long as the length of the barrel exposed beneath/ahead of the scope bell. Mount it atop the barrel (I use sticky Velcro dots), positioned to slip over about 1/2" of the bell, and stopping just short of the muzzle (so muzzle blast won't upset/damage the tube).

This mirage tube is more effective than a band. The extra diameter around the bell allows some airflow, which I think may be beneficial. I could be wrong about that.

Greg

 

[seanh]

Re: Mirage from Barrel Heat

how about just a mirage shield...

http://www.riflebarrels.com/products/mirage_shield.htm

 

[JRWALLSIII]

Re: Mirage from Barrel Heat

This is a big problem with the high humidity we have in Florida. Basically the biggest problem it causes me is while trying to shoot bugholes on paper. On steel it is not as big of a deal. I am using a higher set of scope rings than I originally did. I also added a sunshades to my scope. Both seemed to help. At the range I like to shoot paper from 100-500 yards. I use a portable fan at the 3 or 9 o'clock position. It's a huge help.

Real world,

Dial back mag and bang steel

 

[gstaylorg]

Re: Mirage from Barrel Heat

Here's another source as well:

http://www.shotmaster10x.com/ProductDetails.asp?ProductCode=MSHIELDS

 

[Mudcat-NC]

Re: Mirage from Barrel Heat

I would think even low power on the ol' scope would be an issue. Heck, we use mirage bands on our iron sighted rifles! Much needed when you bang out 22 shots, or more if LR with unlimited sighters, in sometimes less than 10 minutes. Heavy bbl or not, irons or not, its going to cause problems.

 

[gstaylorg]

Re: Mirage from Barrel Heat

It's important to note that there are really [at least] two places where mirage can be an issue. The mirage between the shooter and the target is one. Caused by convection currents in the air between shooter/target, this type of mirage can be dealt with to some degree by turning down the mag on the scope. Mirage caused by barrel heat is a different animal. It's directly in front of the scope and way, way, way out of the focal plane. I'm sure someone will correct me if I'm wrong, but I strongly suspect turning down the scope mag will have little effect on mirage caused by barrel heat and the resultant distortion of the sight picture.

 

[Bill Larson]

Re: Mirage from Barrel Heat

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gstaylorg</div><div class="ubbcode-body">It's important to note that there are really [at least] two places where mirage can be an issue. The mirage between the shooter and the target is one. Caused by convection currents in the air between shooter/target, this type of mirage can be dealt with to some degree by turning down the mag on the scope. Mirage caused by barrel heat is a different animal. It's directly in front of the scope and way, way, way out of the focal plane. I'm sure someone will correct me if I'm wrong, but I strongly suspect turning down the scope mag will have little effect on mirage caused by barrel heat and the resultant distortion of the sight picture. </div></div>

Most LR shooters have and use barrel bands/sunshades.....check creedmor/sinclair...or make one yourself outa black velcro....
bill larson

 

[gstaylorg]

Re: Mirage from Barrel Heat

I have plenty of mirage bands from the vendor above that I use every time I shoot. I was trying to point out for the OP that decreasing mag on the scope can help with mirage at or near the focal plane of the scope/target, but that a mirage band (or similar device) would be necessary to minimize mirage generated right in front of the scope by barrel heat. Perhaps my impression was mistaken, but it seemed to me that it was being suggested that turning down the scope mag might help with barrel mirage, which I doubt is as good a solution as a mirage band.

 

[Sterling Shooter]

Re: Mirage from Barrel Heat

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gstaylorg</div><div class="ubbcode-body">It's important to note that there are really [at least] two places where mirage can be an issue. The mirage between the shooter and the target is one. Caused by convection currents in the air between shooter/target, this type of mirage can be dealt with to some degree by turning down the mag on the scope. Mirage caused by barrel heat is a different animal. It's directly in front of the scope and way, way, way out of the focal plane. I'm sure someone will correct me if I'm wrong, but I strongly suspect turning down the scope mag will have little effect on mirage caused by barrel heat and the resultant distortion of the sight picture. </div></div>

I think you and Mudcat are right on it. When I first got into NRA LR, I shot a match conditioned M14. After a few sighter rounds, my front sight just seemed to disappear along with the target. I eventually developed a cadence which precluded the problem; however, the cadence introduced a new problem with wind analysis. Go figure. I never resolved that problem and now I shoot the AR based Service Rifle which does not have such an issue.