12-02-2005, 19:14
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#1
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Guerrilla Chief
Join Date: Sep 2005
Location: DFW area
Posts: 861
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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
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dr. mabuse is offline
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12-02-2005, 19:54
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#2
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Area Commander
Join Date: Feb 2004
Location: Phoenix, AZ
Posts: 1,691
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I believe it is a harmonics issue.
But I'm no expert in the field.
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Smokin Joe is offline
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12-02-2005, 20:07
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#3
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Quiet Professional
Join Date: Sep 2004
Location: Ohio
Posts: 982
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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
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Doc is offline
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12-02-2005, 20:45
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#4
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Quiet Professional
Join Date: Jan 2004
Location: Phoenix, AZ
Posts: 20,929
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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
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Team Sergeant is offline
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12-03-2005, 00:30
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#5
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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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
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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12-03-2005, 15:32
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#6
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Guerrilla Chief
Join Date: Sep 2005
Location: DFW area
Posts: 861
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Quote:
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Originally Posted by The Reaper
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
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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. 
Last edited by dr. mabuse; 12-03-2005 at 15:35.
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dr. mabuse is offline
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12-05-2005, 18:56
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#7
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Asset
Join Date: Nov 2005
Location: Manitoba, Canada
Posts: 22
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Quote:
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Originally Posted by dr. mabuse
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
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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
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SeekHer is offline
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12-05-2005, 19:11
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#8
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Quiet Professional
Join Date: Jan 2004
Location: LA
Posts: 1,653
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What distance did you shoot your groups?
Can you post a pic of your rifle with the bipod attached?
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NousDefionsDoc is offline
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12-05-2005, 21:58
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#9
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Guerrilla Chief
Join Date: Sep 2005
Location: DFW area
Posts: 861
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Quote:
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Originally Posted by NousDefionsDoc
What distance did you shoot your groups?
Can you post a pic of your rifle with the bipod attached?
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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?
Last edited by dr. mabuse; 12-05-2005 at 22:01.
Reason: attaching picture
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dr. mabuse is offline
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12-05-2005, 22:09
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#10
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,825
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Usually file size, file type, or already posted elsewhere here.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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12-05-2005, 22:18
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#11
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Guerrilla Chief
Join Date: Sep 2005
Location: DFW area
Posts: 861
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Quote:
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Originally Posted by The Reaper
Usually file size, file type, or already posted elsewhere here.
TR
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Just a standard jpeg at 811Kb. I just took the picture about ~20 minutes ago so it couldn't have been previously posted. Let's try it again. Had to resize to make under the 800 X 800 limit.
Well, it uploaded but I don't see it in the "Attached Thumbnails" field?
Last edited by dr. mabuse; 12-05-2005 at 22:22.
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