Need advice on shooting gremlin
 

I'm new to this type of rifle set-up and observed something strange today.

Put together a Bushmaster lower w/~3# trigger, A3 upper with 24" bull barrel, 1/8 twist, floated fore-end, Harris bipod and Leupold Mark IV on top.

I shot small 3 shot groups and reloaded after each group but each group was floating around within a ~ 3 1/2" diameter.

I folded up the bipod and shot off a ruck and then got consistent 1/2" or less groups without the groups wandering around.

Used the bipod and the problem returned.

I don't have to use the bipod but is there a way to cure this with a bipod attached?

Never saw this before with a bolt gun or a shorter AR.

Thanks

I believe it is a harmonics issue.

But I'm no expert in the field.

I'm thinking the same thing as smokin joe and I too know little about this type of issue.

Sounds like your barrel doesn't like the bipod.

I could be wrong. Wouldn't be the first time.

Doc

Doc and Joe are all over it.

Lose the bi-pods. They were designed for machine guns, not for precision shooting, not unless they are attached to a free floating stock. Even then they should be specialized bi-pods, make to take shock away from the weapon.

The internal ballistics can be affected if the rifle is fired while in contact with a "hard" surface (frozen ground, wood, rock, road, building, window ledge, table top, truck bed etc.). Contact coming from the surface, transmitted to the bi-pods, transmitted to the barrel, before the bullet has left the barrel, you get the picture.

Could also be you changed your body position when shooting off the ruck. Could be due to a number of reasons, stock weld/spot weld might also have changed when you went from a bi-pod position to a ruck position.

Mr. Long-range and Mr Econ are the heat here as far as long rifles go. I’m sure they might offer more in the way of opinions.

TS

TS is right, though you can shoot off the bipod on a soft surface with better results.

I would also tell you that I am not a fan of three shot groups. Five to ten will tell you much more about the consistent (and probable) accuracy.

TR

Thanks TR, TS, Doc, Smokin Joe.

TR, the 3 shots were a quicky group to find out where the initial bore sight was on target on a new gun. I also prefer 5-10 shot groups.

Shot this morning on ground with bipod and the ground seemed to "decouple" the vibration. Cold bore shot produced 1/2" group with bipod, ~3/8" with ruck.

I'll probably stick with the ruck because it settles the rifle lower to the ground. I usually shoot heavy bolt guns and hadn't seen this before.

Also, maybe I was just excited by that new gun smell yesterday. :p

2004 Shot show I swear I saw a Vibration dampener made for rifle. Kind of the same idea when using vibration dampeners used on bows. Having shot a bow I know they work. I've yet to hear about anyone using one on a rifle. Next time i'll buy one and check it out!

I have hydraulic stabilizers on my bows. It was explained to me they keep harmonic balance within the bow, decrease vibration, and improve accuracy.

I've used them for years and like the performance I get with them.

Doc

dr, interesting thread. The only additonal idea that MAY be benefitical is that, your barrel may not actually Free Float. Maybe a picture if that is possible. I saw a Ar with a advertised "free floating" fore piece and it was attached to the rear and just before the front site on the barrel. I would think any attachment forward of the chamber would defeat the idea of a free floating barrel. Check your barrel nut besure it is tight.

On all of my free floating barrels nothing touches the barrel forward of the chamber. No slings, bi pods (not a fan of them) or fore piece.

Hollis, the only thing I see is the "collar" that the fore end tube screws onto behind the barrel nut. The fore end does not touch anything else and clears the A3 gas block by about 1/8" or more. The gas tube is not rubbing or touching anything in there.

As long as I don't shoot with the bipod on a hard surface, it behaves.

LimbSaver™ Barrel De-Resonator made by Simms Vibration Laboratory is the product you’re referring to and they work great...my friend has one mounted on his .223 tactical rifle and has improved his groups by about 20%...previously ¾ to 7/8 inch now ½ to 5/8 inch consistently…no change in ammo, firing style, temperature or humidity, just this little $20.00 piece of rubber like material…

When fired, rifle barrels resonate on certain frequencies, just like speakers, and when you add any distortion (pressure) to the vibrations, mounting on hard surfaces etc. the resonance changes and the bullet goes somewhere different...why some speakers sound better in different parts of your house...the principal has been applied to bows for a number of years and any archer will tell you they add in the accuracy department...

This device slides down the barrel (no bull, sorry) and stops at the forend, when you fire, it dampens the vibrations to the same consistent level each time and makes the bullets fly straighter, maybe not straighter, but just to the same point of aim (Browning BOSS is a system similar, which also works very well---I use a BAR .300 mounting it---and it now comes with a built in, closable, muzzle brake)...simple little thing like that and it works...it's one of those "why didn't I think of that"…

I’ll be picking up a couple for my rifles as well, supposed to work from .22LR to stopping calibers…nice thing about it—you can switch them between rifles any time you want…hope this helped

If the bipod is mounted to the barrel there is your problem, if it is mounted to the forend then I don't really know, but what comes to mind is maybe a loose screw/bolt that needs to be tightened--not the same but I had that problem with one of my bolt guns...a possible solution for the barrel mount would be to shoot the bipod with padding attached to the feet, dampen the vibration as you say this only occurs off hard surfaces...you can't always put a duffle roll under your gun in the field and you'll have to rely on the bipod...just a thought

What distance did you shoot your groups?

Can you post a pic of your rifle with the bipod attached?

Shot groups at 100 yards. Pardon the iffy picture. I just went out in to the garage and shot the pic in the dark with the wife's digital.

Well, I get an error for an "invalid post" when I click on upload. Pic size is o.k.

Any ideas?

Usually file size, file type, or already posted elsewhere here.

TR