Grayfox
US Veteran
I'm considering a .22LR conversion unit for my M&P-15. I know nothing about them. Please educate me. 
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.22LR conversion?
- Thread starter Grayfox
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cyphertext
US Veteran
Just buy a S&W M&P 15-22. We have one of those and a CMMG dedicated .22lr rifle. The S&W runs better, and has the same manual of arms right out of the box. I purchased a redi mag adapter for my CCMG lower so that it could use the M&P 15-22 magazines and have last round bolt hold open. The 15-22 will also be more accurate than your AR with a conversion kit, as the 15-22 will have the proper twist rate for .22lr.
ARVOL
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ARVOL
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I'm considering a .22LR conversion unit for my M&P-15. I know nothing about them. Please educate me.
I read here a lot. I don’t post as much as I’d like. However, cyphertext seems extremely knowledgeable and has set me straight and helped me out several times.
I would like to read others’ opinions though. I have a .22 LR conversion kit that I have never used.
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cyphertext
US Veteran
Don't get me wrong, there are pros and cons to both...
With the conversion bolt, you are using your same lower, so you can use the same trigger... not the same model of trigger, but the exact trigger. You also don't have the expense of two sets of sights, or two optics to kit out a dedicated .22lr to match your 5.56mm rifle.
A rifle with the conversion bolt will also be the same weight, where the 15-22 is pretty light.
With a conversion bolt, you may find that you have to re-zero your sights as the .22lr may have a different POI than the 5.56mm. With the 15-22 (or a dedicated upper with the conversion bolt) you don't have to worry about POI shift since you are not changing between calibers.
And, like I stated before, most conversion kits do not have last shot bolt hold open. I purchased a Redi Mag adapter to add this feature to my CMMG rifle. But I also bought the Redi Mag so that I could use M&P 15-22 magazines... I could go purchase M&P 15-22 magazines at Cabela's with ease, so I wanted to use those instead of the Black Dog magazine that was compatible with my CMMG.
My CMMG also cost more than the 15-22. Granted, I bought the Quebec-A, which is a multi-caliber marked lower with a dedicated .22lr upper to make up a complete rifle, but it cost more than the 15-22 as a complete rifle.
Just some thoughts to help you decide which way you want to go.
With the conversion bolt, you are using your same lower, so you can use the same trigger... not the same model of trigger, but the exact trigger. You also don't have the expense of two sets of sights, or two optics to kit out a dedicated .22lr to match your 5.56mm rifle.
A rifle with the conversion bolt will also be the same weight, where the 15-22 is pretty light.
With a conversion bolt, you may find that you have to re-zero your sights as the .22lr may have a different POI than the 5.56mm. With the 15-22 (or a dedicated upper with the conversion bolt) you don't have to worry about POI shift since you are not changing between calibers.
And, like I stated before, most conversion kits do not have last shot bolt hold open. I purchased a Redi Mag adapter to add this feature to my CMMG rifle. But I also bought the Redi Mag so that I could use M&P 15-22 magazines... I could go purchase M&P 15-22 magazines at Cabela's with ease, so I wanted to use those instead of the Black Dog magazine that was compatible with my CMMG.
My CMMG also cost more than the 15-22. Granted, I bought the Quebec-A, which is a multi-caliber marked lower with a dedicated .22lr upper to make up a complete rifle, but it cost more than the 15-22 as a complete rifle.
Just some thoughts to help you decide which way you want to go.
Ditto...... good advice .....it is lighter but it's still a great trainer and an excuse to buy another rifle!!!!!
15-22s are just plain..... fun guns
I have conversion kits for my Beretta 92 and Browning HP..... find myself just grabbing my CZ Kadet a dedicated .22
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I have a spikes conv and just never liked using it. I have more than a few .22s and I bought a MP 15-22. I think it is the funniest .22 I own. I say this and I have two purpose built .22 AR15 rifles with CMMG barrels
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I have both AR-15s with conversion kits as well as a dedicated .22 LR (a CMMG upper half on an AR-15 lower) and a Colt M4 Tactical .22 LR.
Accuracy wise the Colt M4 .22 LR is the most accurate of the bunch, even though it's a rifle that AR snobs love to hate since it really isn't an AR-15. My dedicated .22 LR will almost hold its own with the Colt. The difference is that the Colt's bolt carrier and recoil spring allow it to be tuned to the load, and make it very standard velocity ammo Friendly.
However, my 20" 1-12" Colt SP1 with a Ceiner .22 LR conversion installed comes close to the accuracy of the above rifles.
In contrast, a CMMG or Ceiner conversion in one of my 1-9" AR-15s is not nearly as accurate. The barrel twist makes a difference and the slower the better when .22 LR likes a 1-16" twist. I don't have a 1-7" barrel, but I'm positive the accuracy with .22 LR would be awful.
Barrel twist is the detail that is usually missing when shooters start comparing .22 LR AR-15 style rifles, dedicated .22 LR AR-15 uppers, and .22 LR AR-15 conversion kits. If you have an old school 1-12 twist barrel a conversion kit will give good accuracy. With 1-9" twist it'll give ok accuracy, and with 1-7" twist it's about as accurate as the average slug gun.
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What a .22 LR conversion kit can offer is flexibility.
For example, I built a lightweight AR-15 using a slick side M16 style upper, 1-12" twist pencil weight carbine barrel, carbine length triangular handguards and a short entry stock. It weighs 5 pounds 7 oz with empty magazine. I pack it in a take down carry case with a couple 30 round magazines of .223, along with a Ceiner conversion, a .22 LR magazine and 150 rounds of .22 LR and a sight adjustment tool.
I have to remember the sight settings to re-zero to and from .22 LR, (which are written down in the case) but it gives me a portable survival rifle that will shoot either .223 for larger game, or .22 LR for small game in a single package that I can throw in a baggage compartment in pretty much any GA aircraft.
If I am flying to a destination state (or Canada) that does not allow semi-autos, I have to take my Springfield M6 instead, and it is a lot less capable. In fact, it is so much less capable that I generally just carry my 9422 Trapper in a take down case.
Accuracy wise the Colt M4 .22 LR is the most accurate of the bunch, even though it's a rifle that AR snobs love to hate since it really isn't an AR-15. My dedicated .22 LR will almost hold its own with the Colt. The difference is that the Colt's bolt carrier and recoil spring allow it to be tuned to the load, and make it very standard velocity ammo Friendly.
However, my 20" 1-12" Colt SP1 with a Ceiner .22 LR conversion installed comes close to the accuracy of the above rifles.
In contrast, a CMMG or Ceiner conversion in one of my 1-9" AR-15s is not nearly as accurate. The barrel twist makes a difference and the slower the better when .22 LR likes a 1-16" twist. I don't have a 1-7" barrel, but I'm positive the accuracy with .22 LR would be awful.
Barrel twist is the detail that is usually missing when shooters start comparing .22 LR AR-15 style rifles, dedicated .22 LR AR-15 uppers, and .22 LR AR-15 conversion kits. If you have an old school 1-12 twist barrel a conversion kit will give good accuracy. With 1-9" twist it'll give ok accuracy, and with 1-7" twist it's about as accurate as the average slug gun.
-----
What a .22 LR conversion kit can offer is flexibility.
For example, I built a lightweight AR-15 using a slick side M16 style upper, 1-12" twist pencil weight carbine barrel, carbine length triangular handguards and a short entry stock. It weighs 5 pounds 7 oz with empty magazine. I pack it in a take down carry case with a couple 30 round magazines of .223, along with a Ceiner conversion, a .22 LR magazine and 150 rounds of .22 LR and a sight adjustment tool.
I have to remember the sight settings to re-zero to and from .22 LR, (which are written down in the case) but it gives me a portable survival rifle that will shoot either .223 for larger game, or .22 LR for small game in a single package that I can throw in a baggage compartment in pretty much any GA aircraft.
If I am flying to a destination state (or Canada) that does not allow semi-autos, I have to take my Springfield M6 instead, and it is a lot less capable. In fact, it is so much less capable that I generally just carry my 9422 Trapper in a take down case.
sgtsandman
US Veteran
I find having a dedicated .22LR with the same form and function as the higher caliber model is the better option than a conversion kit. Mainly because of the re-zero issue, assuming it shoots accurately when converted.
rockquarry
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An old time shooter told me a long time ago regarding conversion units, "If you want a .22, get a .22." Still sound advice.
OP
Grayfox
US Veteran
Well, its winter, I can't go out to play, I'm bored and all kinds of strange ideas are running through my mind. 
These things show up on Armslist every now and then. I think I'll just wait until another one pops up and make a decision then.
These things show up on Armslist every now and then. I think I'll just wait until another one pops up and make a decision then.
Scott in NCal
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One of the advantages of the conversion kits is it turns a "California assault weapon" into a ordinary 22 rimfire rifle.Add all the scary looking attachments you want.
cyphertext
US Veteran
Really? Crazy laws out there. I would have expected CA to apply their assault weapons laws to all guns, and especially any gun with a "multi caliber" lower.
Scott in NCal
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