First Round POI shift?

[m1ajunkie]

I have been shooting my .308 ar with 20" SS barrel by single loading a round in the mag, and then releasing the bolt to chamber it. Results are very nice when doing this, usually 1 moa out to 675yds which is my max.

Today I decided to load 5 in the mag and shoot 5 round groups letting the rifle function like normal. I installed a new NF scope and cleaned the rifle prior to this range trip. I shot 50 rounds today and experienced a 1-1.5" vertical shift in poi with the first round off of the mag.

This shift occured with both my 178gr handloads that have performed really well when single loading and FGMM. Both types of ammo shot the remaining 4 rounds into an inch, but the first round always went high.

Shooting was done off of bags from the bench. Conditions seemed very nice for shooting, no mirage or wind and nice temps. My bench position was a little wierd as I had to lean to the right to get behind the rifle in order to utilize my rear bag.

Any idea what could cause this? My contorted position? Should I be looking for a new barrel? Prior to today, the barrel had 400-500 through it, could the barrel simply need more fouling shots prior to shooting good again? I could probably just hold .5mil low every first round, but that is more trouble than I expect out of my rifle.

 

[SwatSgt]

Re: First Round POI shift?

Ok I read it twice so lets see if I understand what you are doing, You are starting with the bolt locked open, loading the mag, hitting the bolt release and then shooting.

I had the same issue with my LR-308 and someone on here told me how to fix it. Instead of hitting the bolt release to send the bolt forward use the charging handle and pull the bolt all the way to the rear then send it forward. OR option number two that I use is just leave the bolt forward, load the mag and then pull the charging handle all the way to the rear and release. At 100 yards my first round was impacting about 3/4" high and now they all group together with no POI shift between rounds. Hope it helps you as much as it helped me.

 

[toadbrown]

Re: First Round POI shift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SwatSgt</div><div class="ubbcode-body">Ok I read it twice so lets see if I understand what you are doing, You are starting with the bolt locked open, loading the mag, hitting the bolt release and then shooting.

I had the same issue with my LR-308 and someone on here told me how to fix it. Instead of hitting the bolt release to send the bolt forward use the charging handle and pull the bolt all the way to the rear then send it forward. OR option number two that I use is just leave the bolt forward, load the mag and then pull the charging handle all the way to the rear and release. At 100 yards my first round was impacting about 3/4" high and now they all group together with no POI shift between rounds. Hope it helps you as much as it helped me. </div></div>

Good info to keep in mind SWAT!

 

[m1ajunkie]

Re: First Round POI shift?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Speedgoat_ Junkie</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SwatSgt</div><div class="ubbcode-body">Ok I read it twice so lets see if I understand what you are doing, You are starting with the bolt locked open, loading the mag, hitting the bolt release and then shooting.

I had the same issue with my LR-308 and someone on here told me how to fix it. Instead of hitting the bolt release to send the bolt forward use the charging handle and pull the bolt all the way to the rear then send it forward. OR option number two that I use is just leave the bolt forward, load the mag and then pull the charging handle all the way to the rear and release. At 100 yards my first round was impacting about 3/4" high and now they all group together with no POI shift between rounds. Hope it helps you as much as it helped me. </div></div>

Good info to keep in mind SWAT! </div></div>

Thanks for the tip SWATsgt.

I will give that a try when I get back out. I am also going to shoot prone using front and rear bags so I can get squarely behind the rifle. I was in an odd position and I wasn't getting consistent pressure on the stock with my shoulder.

Looking back over my notes I am feeling like this position was causing me to shoot the first round high, then I would get settled and shoot the rest of the rounds much better.

In the past during load development, I shot several 5 round groups at the powder charge I am using and all five rounds went under an inch with no fliers. This was prone off of sandbags.

I made this post last night before reading through my notes and thinking through what I was experiencing on the range.