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6.8 SPC accuracy question

 
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  #1  
Old 03-22-2013, 06:30 PM
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6.8 SPC accuracy question

I have a stag arms 6.8 SPC II 16" upper. Free floated barrel. DPMS lower with Timmney trigger.
I have been shooting SSA 85 grain frangible and a 90 grain Speer TNT hand load. Both these shoot fairly well.

The kicker is my cold bore shot is exceptionally good. But subsequent shots seem to move an 1.5"-2". And start a whole new group.

I can only assume there is some variable in the bolt lockup between when I drop it manually and when it runs it's own cycle.

Anyone have experience in this area?
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  #2  
Old 03-22-2013, 06:42 PM
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Re: 6.8 SPC accuracy question

It if I could could fix this little issue without a new barrel/ matched bolt combo that would be great. It serves its purpose as you can see but more accurate is the goal
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The best gun to have? ... The one in your hand when the fight starts!

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  #3  
Old 03-22-2013, 08:29 PM
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Re: 6.8 SPC accuracy question

Quote:
Originally Posted by Lyons7STW View Post
I have a stag arms 6.8 SPC II 16" upper. Free floated barrel. DPMS lower with Timmney trigger.
I have been shooting SSA 85 grain frangible and a 90 grain Speer TNT hand load. Both these shoot fairly well.

The kicker is my cold bore shot is exceptionally good. But subsequent shots seem to move an 1.5"-2". And start a whole new group.

I can only assume there is some variable in the bolt lockup between when I drop it manually and when it runs it's own cycle.

Anyone have experience in this area?

I have several rifles that don,t like the first clean barrel shot so I shoot a fowler, dry patch and they
group well.(Some loads are sensitive to a clean oiled barrel) Also some bullets react differently to
bore conditions. Try setting your zero after shooting one round and if that doesent work try a 110
or 115 grain bullet with more body to engage the rifling.

J E CUSTOM
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  #4  
Old 03-22-2013, 09:00 PM
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Re: 6.8 SPC accuracy question

I probably did no phrase that correctly. I have tried the heavier bullets and was disappointed. The two listed are the best so far.

I shoot a fouler first even in my bolt guns. It can make a big difference. The issue appears to be between first shot from a dropped bolt and cycled rounds. I am not cleaning in between.

Thank you for the response
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An unarmed man can only flee from Evil and Evil is not overcome by fleeing it.

The proper use of a Pistol is to fight your way back to where you left your Rifle.

The best gun to have? ... The one in your hand when the fight starts!

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  #5  
Old 03-23-2013, 07:06 AM
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Re: 6.8 SPC accuracy question

Quote:
Originally Posted by Lyons7STW View Post

I shoot a fouler first even in my bolt guns. It can make a big difference. The issue appears to be between first shot from a dropped bolt and cycled rounds. I am not cleaning in between.

Thank you for the response

Stranger things have happened in the AR platform.

If this appears to be the problem, It sounds like you need to size the brass smaller. (Factory ammo for
autos is small base sized.) with more head space and a smaller body for ease of chambering in a tight
chamber. If your dies are adjuster all the way down you can grind .002 to .003 thousandths off the bottom of the sizing die or buy a small base sizing die. Hornadys New dimension dies will also do this.

At one time all AR15/M16s had a forward assist button to help seat the bolt in battery, if yours doesn't
you will have to size the brass a little more.

Hope this helps.

J E CUSTOM
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  #6  
Old 03-23-2013, 09:26 AM
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Re: 6.8 SPC accuracy question

My dies are small base and I had considered this so I checked and factory ammo produced the same result. I think I will take it to a good smith and see what steps can be taken to true up the receiver face, barrel, and locking lugs. Then insure barrel nut is properly torqued.

I am not as well versed on autos so I had to research and it appears there are some some steps to take and improve this.


Does this sound reasonable?
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An unarmed man can only flee from Evil and Evil is not overcome by fleeing it.

The proper use of a Pistol is to fight your way back to where you left your Rifle.

The best gun to have? ... The one in your hand when the fight starts!

Respect All - Fear None
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  #7  
Old 03-23-2013, 09:52 AM
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Re: 6.8 SPC accuracy question

This conversation is a bit silly, how much deviation are we talking about at 100m, how fast are you shooting and what is your barrel profile? Also consider the magazine your using it may be a factor, I don't believe bolt lock up it the issue.
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