[dont_tread_on_me]

Ok I have a few questions for Alex.IF there is going to be a 22 conversion kit,will it be like some of the other kits on the market in that it uses the 5.56/.223 barrel or will the barrel be specific to the rimfire cartridge? I know Ciener and some other companies,from my understanding,use a chamber insert the has a short smoothbore area right before the bullet enters the rifling.This chamber insert, along with a proprietary bolt carrier /recoil spring assembly,and magazine makes up the kit.
The problem with the kits that use the 5.56/.223 barrel is threefold.First the bore diameter is larger on the centerfire.Second,the bullet has to bounce around the smoothbore chamber insert before engaging the rifling,and three,the twist rates for the rimfire are much different than for the centerfire.The point being here is that none of these things are conducive to accuracy.
Now I know most of you who want this kit won't be using it for match or benchrest purposes.Most of you would use it for the same thing I would,as a supplement to your centerfire training at reduced cost.At the same time however,You want to be able to hit what your shooting at,or your endeavors are pointless,thus the reason for my asking this.
Oh and while I'm at it,what type of magazines will it use.It would be nice having a headstart pending the wake of a potential Obamaban.

 

[aziator]

Well, if I can put my :2cents: in, I want a dedicated .22 barrel. I know this moves the cost up a little more but I think you get a better product when everything is made to work together instead of adapting to use the 5.56 barrel. I would hope he would use the Black Dog mags.

 

[dont_tread_on_me]

I want a dedicated .22 barrel. I know this moves the cost up a little more but I think you get a better product when everything is made to work together instead of adapting to use the 5.56 barrel

My point exactly.I don't have much experience with magazines for these conversions,and hope that anyone that does will share their experience so we all can be more informed.

 

[DSM]

As long as it'll hold 'Minute of Tin Can' accuracy to about 50yds I'd be satisfied either way. +1 on the BDM mags.

If the 5.45 is on the table, is that bore size compatible?

 

[dont_tread_on_me]

The 22l.r. is .221,the 5.45x39 is .221 and the 5.56x45/.223 Remington is .224.So to answer your question,I'm pretty sure it is.Nice idea,by the way.I'm kinda surprised I didn't think of it myself.It would be nice to be squirrel head accurate at 50 yards,I can see myself now trapsing through the woods with it.

 

[aziator]

I am not sure if 5.45 is on the table right now, it would make economic sense to make a barrel that would work in 2 different guns. The problem I see is twist rate. I think you need somewhere around a 1 in 16" for .22, not sure what the 5.45x36 needs.

 

[dont_tread_on_me]

I would think that being the 5.45x39 uses heavier bullets,it would have a relatively fast twist rate of say the 1:7 variety.I'm not sure if that's correct,but it makes the most sense to me.I don't think that would work well for the little rimfire.I think your close on the twist rate for a 22l.r.,I believe they are 1:14,but again I'm not sure.

 

[aziator]

A generic formula I use is

(Bullet Diameter x Bullet Diameter x 150)/length=twist rate

You can also divide by twist rate and get Max Bullet length.

With that formula the max length for a 22 cal in 1:16" twist is .45 and it gets longer as the twist rate goes down. No, this doesn't take into consideration the weight of the bullet. I have a formula around here somewhere for that but can't think of it off the top of my head.

 

[gunner69]

I'm with Aziator on the "dedicated .22LR" concept. I don't want crap deposited in my gas piston area. A dedicated .22RF using blowback sounds the best. :duh: Better accuracy with no complications. :2cents:

 

[MickeyC]

Bullet weight has little to do with ideal twist rates.

Rifling should be matched to bullet length. It just happens that for a given caliber, say .223 REM which actually uses .224 bullets a 62 grain bullet form one vendor is usualy a similar length to a 62 grain tip from another company. some vendors play with their tips however, so a Hornady 75g A-Max is a little shorter than a 77g SMK and shoots tighter groups oout of a 1:9 barrel. If you want to get real tricky one can also discuss bullet construction and explain why light weight varmint bullets explode when shot thought a 1:7 barrel, basically they spin so fact that they rip themselves apart.

We all talk about weight, but what we should disucss is the relationship between bore, bullet length and twist.

The ideal length for a .22lr in the 35-45gr weight group is around 1:16.

 

[aziator]

Thanks for the clarification Mickey, I knew there was a reason I had the one formula memorized and not the one that I found that discussed weight.

 

[1redgmc]

This is an interesting thread... and I like the idea of a .22LR XCR, and suppressed SBR like the Gemtech T2 would be the ultimate setup.

I just this week bought one of the Ceiner drop-in kits off GunBroker to install in my Rock River AR

Upon arrival, I performed the following:

- Opened the package
- Inspected the bolt assembly
- Doused it with Militec
- Set it aside while I removed the Rock River bolt
- Installed the Ceiner bolt
- Cycled the action a few times to spread the lube
- Put on my AAC M4-2000 suppressor
- Loaded up a Black Dog (27) round magazine
- Toted four old skunky beers (full cans) out to ~55 yards
- Came back to the deck
- Turned on the EoTech 512
- Aimed at the first beer can
- Hit it dead on, followed by three more dead on shots

I was very pleased with the performance. I dumped the rest of the mag and hit the cans a few more times.

I've read a lot of good/bad regarding the Ceiner kits, but for $179 I figured what the hell...

I paid $27/ea for the Black Dog mags (bought five of 'em) and although I don't have many rounds through it - I find 50+ yard accuracy with the suppressor to be very good - certainly beer can accurate - and acceptable to me for plinking. With the suppressor, I still have the supersonic crack to deal with when using standard velocity ammo, and have two types of sub-sonic ammo to try (Remington and CCI) - which I expect to perform in a similar manner at less than 50 yards.

I picked up a couple cheap .22 rimfire spinner targets off of Cheaper Than Dirt for $10 each and will give them a try as well.

I suspect I'll have to adjust the EoTech for the shorter range as I pull back to 25 yards...

I also realize the dirty aspect, and would also prefer a dedicated upper to avoid the potential problems associated with dirty rimfire ammo - but for now, I'm having fun! :2cents:

 

[gunner69]

Be sure to use the long pipe cleaners to swab out your gas tube. A shitload of crap is deposited in the gas tube. Wonder what all that crap goes if you follow up with a couple of full 30 rounders???

 

[aziator]

Also be sure to clean out your M42K, don't want a lot of lead buildup in there. Some guys recommend shooting 5.56 through it after a .22 session. I would think a good soak would be better. I have a dedicated 22 can so i haven't ran into this problem yet. I am planning on purchasing 4 AAC Cans when i get back.

 

[1redgmc]

I hear ya Gunner and AZ...

I need to buy a pack of the long pipe cleaners.

I bought a gallon of WD-40 from NAPA and had to soak my AAC Pilot in it after 500 rounds of sub-sonic. It had a significant lead build-up on the first baffle after using it on my SIG Mosquito. An overnight soak proved to be useless - but leaving it in there about a week did the trick. WD-40 obviously doesn't dissolve lead, but it sure as hell penetrates and allows you to use a nylon bore brush to break it loose such that it scrubs right out. I did have to use a small dental pick, but after soaking and brushing, a couple shots with compressed air finished it off and blew out any residue that remained.

AZ - what AAC cans are ya picking up?

I wish AAC would sell that BlackBox .45 suppressor - as I really liked that offset (using standard sights) setup. I was a little put off by having to install those super tall sights on my USP45 with the AAC Evolution 45 and decided to pick up an AAC Ranger for my SBR instead.

How much time ya got left in the penalty box?

 

[aziator]

Red, you should try PB Blaster.

http://blasterchemical.com/display.cfm?p=50003&pid=4

This stuff is way better than WD-40, and it lubricates better too. You spray it in a styrofoam cup and it will eat the cup away. They talk about this and that Kroil stuff over on ST.

I am planning on getting a prodigy, Evo9mm, M42K and 762SD.

I will be here for a few months still, probably home in Feb.

 

[1redgmc]

I use PB for most everything that is stuck! Great stuff.

But I've never seen it in bulk / gallon containers? I do know Kroil does - but I've nit seen it locally.

WD40 costs about $25/gallon - high $$ for sure, so I'm curous how it compares in price.

Be safe over there. I attended the 20th SOS deactivation ceremony and Justin will train on a new airframe in a few weeks. He won't know which one until he gets to San Antonio. He said to say hello and thanks!

 

[MickeyC]

Try copper washed .22LR rounds. Less crap left in the barrel and gas tube.

 

[wilki]

How about a kit with a adapter that would attach to any 10/22 barrel and fit it to the XCR. That would give us a unlimited selection of barrels

 

[aziator]

That may actually not be that difficult, especially if they used 1 barrel type. Say for example they specified a GM heavy barrel. Robarm would have to manufacturer a Slip On/Press On collar that would fit onto the barrel and slide into the upper reciever and be locked into place like any other XCR Barrel. .22 doesn't need to be gas operated, though it may be difficult to design the bolt to operate effectively. That would actually cut down on the cost of the kit though. Customer supplies the barrel, buys a bolt and barrel adapter from Robarms. You could probably keep the price around $200 (+ a barrel).