Rookie question about groupings - RimfireCentral.com Forums

Go Back   RimfireCentral.com Forums > >

Notices

Join Team RFC to remove these ads.
Reply
 
Thread Tools Display Modes
  #1  
Old 02-15-2017, 05:56 PM
LukeSkywarner

Join Date: 
Jan 2017
Posts: 
67
TPC Rating: 
0% (0)
Question Rookie question about groupings



Log in to see fewer ads
I've started sighting in my 21133 Target Takedown with a Nikon ProStaff 4-12x40 scope. Mostly shooting bulk Federal and doing OK (I'm confident the majority of inconsistency is me). I also picked up some Eley Contact subsonic ammo to give it a try. Much smaller groupings, but they were consistently to the left. I'm curious why the change in ballistics would move it left? If anything I would have thought it would stay stationary and just get tighter, or maybe go up or down.

I'm sure this is rudimentary, just trying to get edumucated.
Reply With Quote
  #2  
Old 02-15-2017, 07:22 PM
rawhp's Avatar
rawhp
NRA Member - Click Here To Join!

Join Date: 
Feb 2015
Location: 
USA, CA
Posts: 
969
TPC Rating: 
0% (0)
Similar thread from a couple of weeks ago:

http://www.rimfirecentral.com/forums...d.php?t=852433
Reply With Quote
  #3  
Old 02-15-2017, 11:23 PM
Tyendor's Avatar
Tyendor
US Navy Veteran NRA Member - Click Here To Join!

Join Date: 
Nov 2014
Location: 
Kansas
Posts: 
939
TPC Rating: 
100% (12)
What distance are you shooting at? Most rimfire scopes have the parallax set for 50 yards or have an adjustable objective lens. Your scope has the parallax set for 100 yds. At closer distances you eye placement can cause the cross hairs to shift in relationship to the target.

Another thing that could be causing your problem is the fact that you are using a takedown rifle.. Unless you have a good solid lockup between the barrel and receiver your point of impact will not be consistent.
Reply With Quote
 
  #4  
Old 02-15-2017, 11:32 PM
Nick7274
NRA Member - Click Here To Join! GOA Member

Join Date: 
Dec 2016
Location: 
Central Ma.
Posts: 
1,328
TPC Rating: 
100% (3)
A lot of ammo will shoot different, especially bulk rimfire. I've sighted my rifle in at 50 yards hitting dead center then switched ammo and had them grouping 4" -"5 left or right. Depending on what distance your shooting you will need to sight in almost every time you switch ammo. And as stated above you have the parallax issue to deal with also.
Reply With Quote
  #5  
Old 02-15-2017, 11:35 PM
Sophia's Avatar
Sophia

RFC Admin Team
Join Date: 
Dec 2006
Location: 
Raggedy Edge of the 'Verse
Posts: 
20,476
TPC Rating: 
100% (22)
Quote:
Originally Posted by rawhp View Post
Similar thread from a couple of weeks ago:

http://www.rimfirecentral.com/forums...d.php?t=852433


It's hard to believe "solid" metal can whip around like a wet noodle but that's a good analogy. The tip of the barrel moves when a round is fired. It's not just up-and-down but more like a circular motion. Changing from one load of ammo to another could have the tip of the barrel in a slightly different location as the bullet exits the barrel. That accounts for a tight group moving from one location to another with a change in ammo.

As for tight groups, the single most important change you can make is to start with good ammo. Bulk ammo ain't it.... just not enough QC on the consistency in the things that contribute to consistent performance which is what matters when you are shooting for accuracy/precision. Tiny variation in primer quantity or distribution, amount of powder, bullet weight, etc is all it takes to open up a group.

Also, as a general rule you will get better results when shooting for accuracy/precision if you stick with ammo that stays below the speed of sound. Look for ammo with a MV of 1050 - 1100 fps or so for the best results.
__________________
Pink Cadillac
Reply With Quote
  #6  
Old 02-16-2017, 09:27 AM
LukeSkywarner

Join Date: 
Jan 2017
Posts: 
67
TPC Rating: 
0% (0)
Thanks for all the replies. It sounds like there may be a few things affecting this from what I'm hearing:
  1. The Nikon ProStaff has a parallax of 75 yards according to their website. I'm shooting at 24 yards, because that's the length of my range.
  2. Harmonics could be affecting the barrel. This seems less intuitive to me since I'm not shooting high power rounds (Federal bulk and Eley subsonic) through a bull barrel, but I'll do more research.
  3. Federal bulk ammo is unreliable. This I'm confident of, considering how much tighter the groups got with the Eley.

I'll have to try and found an outdoor range with greater distances and try and center he scope for Eley just to see what I can manage. It's very frustrating to me that living in central Colorado it can still be so difficult to find a place to shoot. Too many rich people who don't want noise to reach their property.

Edit: According to this article, parallax shouldn't be affecting me very much at the range I'm shooting at.

Last edited by LukeSkywarner; 02-16-2017 at 09:40 AM.
Reply With Quote
  #7  
Old 02-16-2017, 10:40 AM
CardPuncher's Avatar
CardPuncher
US Air Force Veteran NRA Member - Click Here To Join!

Join Date: 
Sep 2011
Location: 
Northern Florida
Posts: 
1,660
TPC Rating: 
100% (6)
Quote:
Originally Posted by LukeSkywarner View Post
.... According to this article, parallax shouldn't be affecting me very much at the range I'm shooting at.
That's news to me about parallax being caused by using one eye instead of two. I thought it was because you're looking down a tube with lenses and the target and your crosshairs are in completely different focal planes. Regardless of what causes it, you can see it by steadying your rifle on a rest and moving your head side-to-side and seeing how the crosshairs seem to move across the target. Or don't, at the right distance or when it's adjusted out.

With adjustable parallax, that's how you should adjust it until you find out how accurate the range markings on the scope are. Only one of mine (the $80 Centerpoint from Walmart) is marked accurately for range.

If you position your eye so it's centered in the scope, parallax will not be a problem. It's only when your eye is off-center and not in the same position every time that parallax matters. Your eye is centered when the fuzzy ring from the eyepiece or the vignetting at the other end (depending on whether your eye is too close or too far from the scope) is even all around. You might have to move your head forward or back to see it. I like my scopes positioned so the eye relief is almost too long to make that easier to see.

BTW, it's been a few years since I shot much Federal bulk, but I thought it was pretty good stuff for the money.
Reply With Quote
  #8  
Old 02-16-2017, 11:15 AM
LukeSkywarner

Join Date: 
Jan 2017
Posts: 
67
TPC Rating: 
0% (0)
That's a good suggestion, I'll give that a try. It's a small range and can be quite loud depending on what others are shooting, even with earplugs and OTE protectors. The OTE I have that fit me well are quite bulky, so I'm likely not getting a good cheek weld.

I've now shot almost 700 rounds of Federal bulk out of a Browning Buck Mark as well as my 10/22. I have not had a single FTF or ejection problem. Granted I clean my guns fastidiously after every use, but for the price it can't be beat.
Reply With Quote
  #9  
Old 02-16-2017, 10:50 PM
rawhp's Avatar
rawhp
NRA Member - Click Here To Join!

Join Date: 
Feb 2015
Location: 
USA, CA
Posts: 
969
TPC Rating: 
0% (0)
If your eye is consistently in the same location, relative to the scope, then parallax wouldn't cause a shift between ammo types. Test by switching back and forth between the two ammo types and see if the relative shift is always the same (to the left?). That would rule out parallax, unless you're consistently shifting your eye/head depending on the ammo you're shooting.

I'm using a floated 18" bull barrel with the action solidly bedded, and some standard velocity ammo will shoot 1/2" or more higher than other high velocity ammo, due to harmonics.
Reply With Quote
  #10  
Old 02-17-2017, 08:38 AM
Rimfire5
NRA Member - Click Here To Join!

Join Date: 
Jul 2009
Location: 
Northern Virginia
Posts: 
542
TPC Rating: 
0% (0)
Variations in point of impact caused by using different brands of ammo is not uncommon. In fact, you might even see a smaller variation from lot to lot in the same brand of ammo. You didn't say how much of a difference you measured in the point of impact between the two ammos or whether you compared one group with each ammo of the average of all the groups you shot with each.

Federal Bulk ammo uses 40 grain bullets and is transonic at around 1200 fps.
Eley Contact is just barely subsonic but with a 42 grain bullet at 1095 fps. Changes in muzzle velocity alone will change the point of impact. Changes in bullet weight and bullet shape differences between manufacturers can cause changes as well.

The 42 grain Contact bullet will be travelling at about 1045 fps at 24 yards at 50 degrees F (50 fps slower than at the muzzle velocity).
At 24 yards, the Federal bulk bullet velocity would still be above 1125 fps at 50 degrees F (75 fps slower than at the muzzle). I would expect that there should be little impact from the Federal bullets passing through the transonic zone but the vibrations would open up the group more than change the average point of impact.

Most likely the muzzle velocity difference of 105 fps should have the biggest impact and for these two brands there is a 0.2 inch difference drop at the 25 yard point according to a ballistic calculator. The faster Federal ammo bullets are in the barrel for a slightly shorter amount of time. That also can change the point of impact slightly because of the harmonic barrel movement that Sophia describes in a previous post in this thread. The barrel does not move only up and down but it actually moves in an oval caused by the movement of the bullet against the rifling as it moves down the barrel.

But there are other reasons for movement in the point of impact that can even create variations from group to group with the same ammo. The first thing to realize is that the consistency of your positioning behind the rifle and behind the scope and your consistency of trigger pull will cause a lot more variation than the ammo will cause, especially at 24 yards. If you compare different groups with the same ammo, you might find that the point of impact changed from group to group, when you reloaded sometime during shooting the groups. This is an indicator of variations in set up and technique.

Most 22LR rifles are light, especially 10-22s, and they are easily moved around by variations in pressure on any part of the rifle. Those variations will cause changes in point of impact. Having to get into your shooting position again after changing ammos can be a cause for changes in POI after setting up. There is a reason why 22 rifles designed for target shooting are much heavier. They aren't going to move the POI around all that much with slight pressure variations on the stock.
Reply With Quote
  #11  
Old 02-17-2017, 09:31 AM
Tiger-Ock

Join Date: 
Dec 2016
Location: 
Free State of Georgia
Posts: 
68
TPC Rating: 
0% (0)
All right, whip it good.

I have a 21133. Fine little piece.

Make sure that:

scope and mounts are secure, blue Loctited.

for 24 yards use around 4-5x for magnification.

you get some Aguila Super Extra Lead Round Nose or some CCI SV. (your Eley edge is fine but much too expensive for your purpose.)

Make sure that the Take Down lockup is tight, tight, tight.

Shoot it. Don't worry about where them Federal bullets went, only about where you want those CCIs to impact.

You will find that this rifle in its factory form will not especially like HV ammo but will insist upon a diet of Standard Velocity to perform at its most accurate. I am not saying that it will not shoot HV but in my experience the groups will be larger and less accurate.

"...you will need to sight in almost every time you switch ammo."

and this^^

Always check your zero after cleaning; always check your zero after taking it down; leaving it dirty is not really a bad thing. You will spend some time zeroing this rifle if you make any sort of change.
Reply With Quote
  #12  
Old 02-17-2017, 09:53 AM
LukeSkywarner

Join Date: 
Jan 2017
Posts: 
67
TPC Rating: 
0% (0)
Wouldn't the Super Extra or SV equate to Stingers, which my manual specifically states not to use in my Target barrel?
Reply With Quote
  #13  
Old 02-17-2017, 10:10 AM
Chaser's Avatar
Chaser
NRA Member - Click Here To Join! UotM

Join Date: 
Aug 2005
Location: 
S.E. Idaho
Posts: 
19,050
TPC Rating: 
100% (73)
Send a message via AIM to Chaser
Quote:
Originally Posted by LukeSkywarner View Post
Wouldn't the Super Extra or SV equate to Stingers, which my manual specifically states not to use in my Target barrel?
Stingers are Hyper Vel. and NOT recommended in a good aftermarket barrel with a tight chamber.. the casing is longer with a smaller 32gr. bullet and may erode the chamber.. and the accuracy is NOT what you seek.. stay away... same with any High Velocity or Hyper round.
As Sophia stated stick with 1050-1100 fps.
The Super Extra is High Velocity.. average accuracy and will frustrate you with flyers.
The CCI SV is 1070 fps and will shoot with more expensive German ammo's... real good accuracy/best bag for the buck IMO.

This chart may help you.. http://www.coolguyguns.com/bAMMO-b_ep_46-1.html
Reply With Quote
  #14  
Old 02-17-2017, 10:33 AM
LukeSkywarner

Join Date: 
Jan 2017
Posts: 
67
TPC Rating: 
0% (0)
Thanks!
Reply With Quote
  #15  
Old 02-17-2017, 10:54 AM
Tiger-Ock

Join Date: 
Dec 2016
Location: 
Free State of Georgia
Posts: 
68
TPC Rating: 
0% (0)
CCI Standard Velocity is 1070 fps.

Aguila Super Extra Lead Round Nose is 1130 fps.

Stock 21133 Ruger runs a 16 inch barrel. I doubt that anything comes out of the muzzle at advertised speeds.

I cannot attest to CCI SV performance compared to "expensive German ammos..." but CCI SV is good stuff; Aguila is also very accurate from this rifle and its flier quotient is about equal to CCI SV--heresy, I know, but true.

Proof is in the puffin'.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off




All times are GMT -5. The time now is 05:27 AM.

Privacy Policy

DMCA Notice

Powered by vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Search Engine Optimisation provided by DragonByte SEO (Lite) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 2000-2015 RimfireCentral.com
x