CMMG .22LR Conversion - Windage Accuracy Issues

[james_bond_007]

SUMMARY: CMMG Evolution Conversion Kit seems to shoot 4"-6" to the right @ 50 yards

EQUIPMENT:

• CMMG Evolution .22LR Conversion kit Similar to http://www.cmmginc.com/product_p/22ba68d.htm
• Rifle: CAI .223 C15A1 A1-style AR-15 1:9RH twist http://www.centuryarms.com/manuals/p...fle/index.html
• Various .22LR bulk ammo
• Federal XM855 and M193 5.56x45 Ammo

ISSUE:
When using the open sights (A1 style) and windage zeroed at 50 and 100 yards using the 5.56 bolt, the rear sight seems fairly centered. ( I am concerned with windage, not elevation. I understand that the sights will not be zeroed in elevation at BOTH these ranges, AND that typically the rifle sights are supposed to be zeroed and 25m/300m for the A1 sights/5.56 )
With the CMMG .22 kit installed, the rifle seems to shoot about 6" to the right at 25-50 yards.

I CAN get it zeroed, but have to move the rear sight almost all the way to the left.

I do not have a scope for this, as it has an A1 non-removable handle on top.
I tried a friend's "handle mounted" scope once , but did not like the scope sitting another 2-3" above the already high handle.
I only use it for plinking and wanted the .22LR for "inexpensive" plinking.

I am not looking for PINPOINT accuracy, but believe the .22LR zero should be pretty close to the 5.56 zero, at that range, without moving the sights.

SUGGESTIONS:
It was suggested that the front sight might be incorrectly pinned. If true, I cannot, however, understand why 5.56 shoots "straight" and .22LR slides to the right, at such a short range.
It was suggested that the barrel may be misaligned.
It was suggested that I might be jerking the trigger on the 5.56 (probably not on the .22LR)
It was suggested that maybe there was more wind when firing the .22LR. I'm not buying this, as at the short distance, minor wind changes should not be this big a factor.
It was suggested that the CAI rifle is a piece of junk. I'm not expecting it to be competition-level accurate, but it seems fine for plinking.

ACTIONS:
Rifle was still under warranty, so I sent it back to CAI. They test fired it at 100 yards (with a 5.56 tracer) and returned it certifying it was zeroed at 100 yards.
I tried 5.56 again...seemed a pretty good "windage" zero.
I tried the .22 Kit again, without moving the sights, and still 6" to the right.
I tried 5.56 again (in case something got bumped etc.)...still seemed a pretty good "windage" zero.
Since MY 5.56 was on zero, I tried out the " me jerking the trigger " theory.

REQUEST:
As I said, I'm not looking for 1:1 accuracy between .22 and 5.56, but am expecting things to be close.
Am I expecting too much?
If not, any suggestions as to why the .22 Kit behaves this way ?
Anyone else have a kit? Can you comment on your experiences ?

[Delfuego]

Whats your barrel twist? 22lr normally like a 1:16 twist. If your 5.56 barrel is a 1:7 RH twist? That is a lot faster right-hand twist and could account for your results. My conversion shot considerably better from a 1:9 than a 1:7, but still is not "shooting groups" like a dedicated 22 setup would. They also shot better with high velocity 22lr ammo.

[mutt]

There's is a definate POA/POI difference between .22lr and .223/5.56. My .22lr coversion bolts would shoot about an inch to the left and low at 25 yards. At 50 yards the shift was about 3 inches and the group sizes were terrible. This is one of the reasons I switched to a dedicated .22lr upper. Using a proper .22lr barrel greatly improves accuracy and there's no need to compensate for POA/POI shift between 2 calibers.

The 6 inch shift you're getting sounds a bit extreme but then again every barrel is different. If you can get a proper zero @ 100 yards, and a good 10 shot grouping (3 inches or better) with .223/5.56 then I'd say your rifle is ok. One thing to check is the chamber adapter on the conversion bolt. Maybe it has some kind of imperfection that is causing aligment problems.

[james_bond_007]

Whats your barrel twist? 22lr normally like a 1:16 twist. If your 5.56 barrel is a 1:7 RH twist? That is a lot faster right-hand twist and could account for your results. My conversion shot considerably better from a 1:9 than a 1:7, but still is not "shooting groups" like a dedicated 22 setup would. They also shot better with high velocity 22lr ammo.

1:9 RH

Ammo is the high velocity bulk (550 and 330 packs et al.) like:

Remington Thunderbolt
Caliber: 22 Long Rifle
Bullet Weight: 40 Grains

Bullet Style: Lead Round Nose

Muzzle Energy: 140 ft. lbs.

Muzzle Velocity: 1255 fps



Federal Champion

Caliber 22 Long Rifle

Bullet Wt/grains 36

Muzzle Velocity 1260

Rounds/Box 525

[james_bond_007]

There's is a definate POA/POI difference between .22lr and .223/5.56. My .22lr coversion bolts would shoot about an inch to the left and low at 25 yards. At 50 yards the shift was about 3 inches and the group sizes were terrible. This is one of the reasons I switched to a dedicated .22lr upper. Using a proper .22lr barrel greatly improves accuracy and there's no need to compensate for POA/POI shift between 2 calibers.

The 6 inch shift you're getting sounds a bit extreme but then again every barrel is different. If you can get a proper zero @ 100 yards, and a good 10 shot grouping (3 inches or better) with .223/5.56 then I'd say your rifle is ok. One thing to check is the chamber adapter on the conversion bolt. Maybe it has some kind of imperfection that is causing aligment problems.

Let me say it was more like 4"-6" that always 6" .

You identified the issue : my POI was 4"-6" to the right of POI for .22LR. Shots "grouped" OK (not fantastic, nor did I expect fantastic grouping), but just did not land where aimed.

[james_bond_007]

... One thing to check is the chamber adapter on the conversion bolt. Maybe it has some kind of imperfection that is causing aligment problems.

Please explain more. I'd like to understand what you are getting at ...

To me, it would seem that if the bullet is getting out of the adapter, and traveling 20" down the barrel, and probably engaging the rifling most (if not all) the way, there is not much the bolt adapter can do to affect the direction of travel in 25-50 yards.
What are you thinking could be going on ?

[mutt]

Let me say it was more like 4"-6" that always 6" .

You identified the issue : my POI was 4"-6" to the right of POI for .22LR. Shots "grouped" OK (not fantastic, nor did I expect fantastic grouping), but just did not land where aimed.

Yeah, unfortunately that is completely normal. .22 and .223 will not have the same POA/POI. On the rare occasions I use a conversion bolt it's for 25 yards or less. I'd recommend getting a dedicated upper if you want better accuracy. CMMG used to sell their .22lr uppers without a bolt. If they still do that, you can save some money by using your current conversion bolt in the dedicated upper. You just have to switch out the chamber adapter.

[james_bond_007]

Yeah, unfortunately that is completely normal. .22 and .223 will not have the same POA/POI. On the rare occasions I use a conversion bolt it's for 25 yards or less. I'd recommend getting a dedicated upper if you want better accuracy. CMMG used to sell their .22lr uppers without a bolt. If they still do that, you can save some money by using your current conversion bolt in the dedicated upper. You just have to switch out the chamber adapter.

OK. If it is typical that the POI for .22LR Kit and 5.56 are not the same, then I'm OK with that.
I was EXPECTING them to be close to the same at <50 yards ...but it sounds like I was expecting something that is just not going to happen.

The good news is that it sounds like the rifle is setup properly.
Unless I get any other suggestions telling me otherwise, I'll just deal with the POI shift, either by moving the rear sight or by the "Kentucky" method.

Thanks !

[mutt]

Please explain more. I'd like to understand what you are getting at ...

To me, it would seem that if the bullet is getting out of the adapter, and traveling 20" down the barrel, and probably engaging the rifling most (if not all) the way, there is not much the bolt adapter can do to affect the direction of travel in 25-50 yards.
What are you thinking could be going on ?

If the chamber adapter isn't centering properly it may contribute to poorer than expected accuracy. I know spikes used to put o rings on their chamber adapters to help keep the bolt centered in the chamber (and to minimize carbon blowback). In the great scheme of things it probably matters very little.

[Great-Kazoo]

OK. If it is typical that the POI for .22LR Kit and 5.56 are not the same, then I'm OK with that.
I was EXPECTING them to be close to the same at <50 yards ...but it sounds like I was expecting something that is just not going to happen.

The good news is that it sounds like the rifle is setup properly.
Unless I get any other suggestions telling me otherwise, I'll just deal with the POI shift, either by moving the rear sight or by the "Kentucky" method.

Thanks !

Not going to happen the 22 is a .222 dia vs a 223 which is a .224 dia bullet. one is a tad smaller giving you different POI. There are a few discussions regarding bullet dia and accuracy/ POI in a few reloading forums.