Advanced Marksmanship RRA A4 Varmint POA/POI Changes

[Sniper1*]

OK, In a nutshell!

I am shooting a RRA A4 Varmint 18"(as it came from Factory).
Magpul PRS Stock
USO 1.8x10 Tpal
Nightforce Unimount
Harris Bipod
Hornady 55gr TAP

After zeroing the rifle and scope I would return to the range on several occasions and the CB and subsequent 5-8 shots would be about 3/4" up and 3/4" right. Eventually the remaining groups would fall into the existing zero. I could adjust the zero and make the early rounds hit POA but eventually they would then start to fall 3/4" low and 3/4" left putting me back to my original zero.

I have read and researched here, so I tried this test.

I read somewhere that if I was using a full mag the bolt would drag on the top round in the mag more when the mag was full. So the last time out I loaded only five rounds in a 20rd mag. Same results.

I also tried shooting from a pack instead of a bipod. Same results!

I do keep a data book and this has been consistent from the original zero date.

The scope tracks well and goes back to zero after running box drills and such.

Everything is tight, I checked it all again.

Thought about trying and accu-wedge and a JP Ent. rear pin to tighten things up a little more.

The gun is accurate. 1/2 moa when I do my part.

Position/comfort is good. I can get my AI out and it is a hammer. Good old reliable. I don't have another scope to put on it to try.

Was wondering/hoping you guys might have some secret voodoo tips to pass along.

Considering sending scope back to USO to make sure all is in order. It was one of the early 1.8x10 Tpals.

Also considering sending the gun to a smith to have him tweak and twist and bend whatever he can do to make sure all is good with the gun.

Thanks for any input!

 

[J.Boyette]

Re: RRA A4 Varmint POA/POI Changes

Do you shoot a clean barrel every time?

If so shoot 20 to 100rnds and let it sit. Next range trip shoot a dirty barrel.

Might help.

Next idea.

Do you dryfire before shooting?

John

 

[Sniper1*]

Re: RRA A4 Varmint POA/POI Changes

J.B.,

Yep and Yep.

I have shot it both ways. Clean and dirty with the same results.

and

Yes, I do dry fire sometimes. I have read the Cold Bore vs Cold Body - doesn't seem to matter for me.

I tried it with this rifle and my AI and Cold Bore Cold Body all seems to print the same or very close for me.

Thanks for the input.

I am going to try to get to the range today. I will try to post a pic of the target and an explanation of said target if I can get it done.

 

[DustyJacket]

Re: RRA A4 Varmint POA/POI Changes

I have the same, but 26" barrel.

It does the same thing for the first two shots until the barrel warms up.

Then later:

 

[McN]

Re: RRA A4 Varmint POA/POI Changes

I have not experienced this, but from the perspective of eliminating causes, I would say to try firing 5-10 shots into another target or into the berm without really aiming-just to heat the barrel. Then take careful aim and see if you're right on immediately. Won't pinpoint it, but it's probably data worth having in trying to figure this out.

Nick

 

[ker2222]

Re: RRA A4 Varmint POA/POI Changes

seems the simpliest answer is maybe not the answer wanted......that cold bore zero is different from warm barrel zero.

Working shooters need to know both--warm and cold bore zero's for this very reason.

 

[Sniper1*]

Re: RRA A4 Varmint POA/POI Changes

I just got off of the phone with my smith. He says he can suggest a few things. Easiest - JP Tension pin for upper/lower tightening and he is going to square the front of the receiver with the barrel, recrown the barrel (and thread it while it's out), and put the barrel nut and forearm on, as he put it, "the right way". He thinks this will fix a lot of issues and it sure couldn't hurt.

Anyway, I will let you know how it all turns out!

Thanks for the input!

 

[ARCOREY]

Re: RRA A4 Varmint POA/POI Changes

I'm by no means an AR expert, regardless of what my screen name looks like

, but I thought AR accuracy was contributed to the upper and sight mounting system alone and the upper to lower fit did not contribute to this. The only part of the lower from my understanding that can help with accuracy was the comfort of the trigger to the shooter. If I'm wrong someone please chime in and help me understand this too.

 

[Sniper1*]

Re: RRA A4 Varmint POA/POI Changes

I thought the same thing, so, I would be all ears!

 

[Sterling Shooter]

Re: RRA A4 Varmint POA/POI Changes


Re-barrel, or accept the pattern you're getting. BTW, a barrel that shoots the first round and then others to the same place is going to be the exception.

 

[Sniper1*]

Re: RRA A4 Varmint POA/POI Changes

Well, had some work done!

The receiver face was out of square by .004" as was the crown of the barrel. So, both have been redone and put back together. I have also installed the JP rear tension pin.

The gun still shoots very well but in am inconsistent.

I think I have learned a thing or three. When putting the gun back together I used my boresighter to get it close and when I did I grabbed one leg of my bipod. Not meaning to, I put a little torque on it and noticed the crosshairs in the collimator moved significantly. I messed around with it a little more and was actually surprised by the minor amount of torque it required to move the crosshairs that much.

Anyway, I went back to the range and fired several rounds.

Now, after several trips to the range and cleaning and going back again, I have found that I am apparently putting too much torque on the rifle especially the CB. I know I get in position and pay more attention to my shooting position during the CB shot. I think I was causing this and started to relax as my shooting continued.

Today I started shooting from a bag instead of the bipod for my AR. I found that I am much more consistent. Now, I will be testing this theory on my CB shot for the next several outings.

Long story short, I was trying to pre-load the bipod on my AR like I do my AI. Well, there is a weak point in the AR - the barrel nut/barrel/receiver flexes quite easily from what I am finding out.

Any more thoughts from you all?

 

[Sterling Shooter]

Re: RRA A4 Varmint POA/POI Changes

As it appears, you're learning a thing or two about the importance for a consistent position. Remember, all contact with the gun and ground must be consistent: elbows, stockweld, grip, non-firing hand, and butt-to-shoulder. Attempting to make the contact exact to a molecular level, will promote predictable recoil; and, since recoil is an angular concept which cannot be eliminated, making it more predictable will reduce group size, as well as help to refine zero.

Be sure to perfect your position and dry fire, calling your shots. Typically, anything less than perfect will reveal the elements and factors of a steady position which need attention. If you accept that the bullet will always go in the direction the barrel is pointed, then you will also accept that if the bullet does not go where aimed, you did not know where the barrel was pointed-usually, it's about recoil that has not been controlled consistently. An elbow, or some other body part, just a few thousandths of an inch off from the previous shot will change the angularity of the shot (line of departure) enough to place the bullet some place out there other than where desired.

BTW, making recoil predictable is the secret to great shooting. Those who develop this skill will produce better results than shooters who either dismiss or remain ignorant of the concept.

 

[Sniper1*]

Re: RRA A4 Varmint POA/POI Changes

Sterling,
Thank you for all of your input. I see Gunny Hathcock knew what he was talking about with his 7 points. Especially his catch phrase - "pay attention to the details". I will keep working on it!
Thanks,