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Posted: 1/27/2006 3:36:21 PM EDT
I finally shot my Colt 20" HBAR today. I have a Simmons 6.5x20x40 scope in Burris Zee rings on an A.R.M.S. #5 riser block. I also have a benchrest height Harris bipod. I was shooting Winchester 55gr bulk pack ammo.
I noticed the groups were a little large but since I have never owned an AR before I put that down to me.
The groups were around 2" to 3", but I only fored 40 rounds total, was tired and the cold wind blowing in my face made me rush a few shots.
It has also been a long time since I used a scope, and my heartbeats were tough to time my shots around- it kept bouncing the scope sideways.
My rifle also has the original trigger, I'm guessing about 10 pond pull. That has got to go.
This is also the first bipod I have used.
I noticed some of my groups were stringing slightly vertically. I also noticed that the rifle tended to bounce when I shot it. Is this from the bipod?
Jim
Link Posted: 1/27/2006 4:49:23 PM EDT
I would suggest that you remove the bipod and put the rifle forearm on a good sandbag rest. I have seen vertical stringing caused by bipod on several rifles. You did not mention the twist in the barrel you are using. If you can provide this info perhaps your question could be answered in a more specific manner. Charles.
Link Posted: 1/27/2006 4:53:29 PM EDT

Originally Posted By 1911builder:
I would suggest that you remove the bipod and put the rifle forearm on a good sandbag rest. I have seen vertical stringing caused by bipod on several rifles. You did not mention the twist in the barrel you are using. If you can provide this info perhaps your question could be answered in a more specific manner. Charles.


Sorry about that. I was trying to think of everything that might make a difference.
It has a 1 in 9" twist rate.
The bipod is mounted with an adapter to the stock bottom round handguard. It was rested on a piece of carpet on a concrete bench.
I didn't have time to sandbag it. I also had to sight in a reddot on a Ruger MkII .22 pistol, then solve a jamming problem.
Thanks,
Jim
Link Posted: 1/27/2006 5:10:35 PM EDT
Link Posted: 1/27/2006 5:12:48 PM EDT
Like the previous poster pointed out the bipod may very well be a contributing factor (especially in vertical separation). I'd also suggest trying some heavier bullets. The Winchester 62 grain white box stuff is usually pretty good.

I've got a CMP rifle with a 1 in 8 twist that doesn't even start to give really good groups with anything less than a 62 grain bullet (and it really seems to prefer 68 and 70 gr bullets). When I shoot the 55 gr stuff it's only for plinking and fun.
Link Posted: 1/27/2006 5:25:15 PM EDT

Originally Posted By USAFhack:
Like the previous poster pointed out the bipod may very well be a contributing factor (especially in vertical separation). I'd also suggest trying some heavier bullets. The Winchester 62 grain white box stuff is usually pretty good.

I've got a CMP rifle with a 1 in 8 twist that doesn't even start to give really good groups with anything less than a 62 grain bullet (and it really seems to prefer 68 and 70 gr bullets). When I shoot the 55 gr stuff it's only for plinking and fun.




I was ready for large groups with this cheap ammo, but the vertical stringing had me wondering. It wasn't a perfect vertical string. I scattered a few, called most of 'em.
The trigger is a problem.
I will post pics when I go next time. It started raining before I left and those groups were not worth getting soaked for.
I will try heavier factory ammo, but I plan on handloading once I have an idea what she likes.
Jim
Link Posted: 1/27/2006 5:35:49 PM EDT
yep, 10lb trigger is not manageable (my original colt trigger had to be 15+ lbs with a gritty break)...colt's match trigger (5-6lbs ?) is what i chose...crisp trigger, a free float barrel and winds 5-10 mph or less should get you 10 shot 1" groups from most high grade commercial ammo
happy shooting !
Link Posted: 1/27/2006 6:11:26 PM EDT
Sorry for the hijack, but what is the average trigger pull for an AR? I was thinking they were heavy, but I didn't think they were that heavy...
Link Posted: 1/27/2006 6:19:40 PM EDT
I think around 8 pounds.
I haven't measured mine, and 10 pounds may be an exaggeration, but dad's description of it feeling like a gate hinge is right on!
Jim
Link Posted: 1/27/2006 7:34:41 PM EDT
Wow! Talk about perfect timing (the post or me reading it??). Couple weeks ago fired my Colt HBar Competition (20" bbl, 1-9 twist, Simmons A-Tec 3.8-12) from a front rest, shoulder held in the rear. Tried with an assortment of ammo, mostly got groups in the 1-1/4" range. Wierd thing was they all grouped pretty much in same place, so when I centered the clusters, they were pretty consistent for all ammo types.

Trigger was factory (lousy and went "sproing" on release!) at 8+ lbs; installed a Jard 3 lb tonite ($135 with hammer from Brownells); haven't shot it yet.

Was expecting tighter groups, but guess it's pretty good as it is... Just read about an Olympic Arms in "Gun Tests" that got around 3.4" and they thought that was pretty good!!

As long as it's "Minute of Groundhog @ 100', guess I'll leave the bbl alone!

Arden
Link Posted: 1/27/2006 8:36:06 PM EDT

Originally Posted By ColtHBarComp:
Wow! Talk about perfect timing (the post or me reading it??). Couple weeks ago fired my Colt HBar Competition (20" bbl, 1-9 twist, Simmons A-Tec 3.8-12) from a front rest, shoulder held in the rear. Tried with an assortment of ammo, mostly got groups in the 1-1/4" range. Wierd thing was they all grouped pretty much in same place, so when I centered the clusters, they were pretty consistent for all ammo types.

Trigger was factory (lousy and went "sproing" on release!) at 8+ lbs; installed a Jard 3 lb tonite ($135 with hammer from Brownells); haven't shot it yet.

Was expecting tighter groups, but guess it's pretty good as it is... Just read about an Olympic Arms in "Gun Tests" that got around 3.4" and they thought that was pretty good!!

As long as it's "Minute of Groundhog @ 100', guess I'll leave the bbl alone!

Arden



I had the front rested by the bipod and the rear into my shoulder. I crossed my left arm under the pistol grip but it really didn't rest on it.
I didn't measure the groups but guesstimated by looking through the spotting scope at a known target (NRA Official Smallbore)
Today was more to get the scope here the rifle would print on paper and to get familiar with the rifle. Any group was a bonus.
I have never used a bipod before and have no idea what to look for if problems come up, like stringing, or if the bipod can ause group error.

If I get a FF tube and mount the bipod on that will the problem be reduced?
Jim
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