Can a 5.45x39 upper receiver fit a 5.56 lower receiver? I've been looking at the 5.45x39 AR-15 rifles. I found a really nice upper but i cant seem to find a 5.45x39 lower. So i was wondering if it would fit a 5.56 since they are so close of a caliber.I would also like to know if i could use regular AR-15 mags for the 5.45x39 round.
Can a 5.45x39 upper receiver fit a 5.56 lower receiver?
- Thread starter Formyguns
- Start date
357 Python
New member
Considering that a .50 Beowolf upper will fit the 5.56 lower, My guess would would be yes. This is a guess only so don't hold me to it.
5.45x39 upper will fit a milspec lower.
The only real difference between a 5.45 vs 5.56 AR is the barrel and the bolt. Maybe, the hammer spring may need to be stronger for a 5.45 depending on ammo you use.
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My S&W 5.45x39 upper is on a Spike's tactical lower. Prior to the S&W 5.45x39 S&W, I used the lower with a BCM 5.56x45 upper.
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More than 7 rounds of 5.45 in a 20 round 5.56 magpul polymer magazine will produce a jam.
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30 round C-products SS 5.45x39 magazine is good --- came with the S&W upper.
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I like the felt recoil with the 5.45 than 5.56. It is milder and it shoots just as well as any 5.56 at 50 and 100 yards.
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Beware of corrosive ammo. My S&W bolt has pits after 2000 corrosive rounds. Must clean after range trip.
If you plan to shoot a lot of rounds per range session, 5.45 corrosive is good to save on cost. If you shoot a few rounds once or twice a week, stay away from corrosive --- too much cleaning.
Non-corrosive 5.45 steel case ammo is just as expensive as low end steel cased 5.56.
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The only real difference between a 5.45 vs 5.56 AR is the barrel and the bolt. Maybe, the hammer spring may need to be stronger for a 5.45 depending on ammo you use.
=============
My S&W 5.45x39 upper is on a Spike's tactical lower. Prior to the S&W 5.45x39 S&W, I used the lower with a BCM 5.56x45 upper.
=============
More than 7 rounds of 5.45 in a 20 round 5.56 magpul polymer magazine will produce a jam.
=============
30 round C-products SS 5.45x39 magazine is good --- came with the S&W upper.
=============
I like the felt recoil with the 5.45 than 5.56. It is milder and it shoots just as well as any 5.56 at 50 and 100 yards.
=============
Beware of corrosive ammo. My S&W bolt has pits after 2000 corrosive rounds. Must clean after range trip.
If you plan to shoot a lot of rounds per range session, 5.45 corrosive is good to save on cost. If you shoot a few rounds once or twice a week, stay away from corrosive --- too much cleaning.
Non-corrosive 5.45 steel case ammo is just as expensive as low end steel cased 5.56.
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tahunua001
New member
well just to reiterate what has already been said, yes. however a word of caution;
it may not be completely hot swappable with your existing 5.56 lower. some of them require heavier hammer springs, some require beefier hammers in addition to. if you have a 2 stage trigger it may cause light strikes. the reason for this is 5.45 primers are harder than 5.56 primers.
it may not be completely hot swappable with your existing 5.56 lower. some of them require heavier hammer springs, some require beefier hammers in addition to. if you have a 2 stage trigger it may cause light strikes. the reason for this is 5.45 primers are harder than 5.56 primers.
tahunua001
New member
a 5.45 has almost identical recoil to a 5.56 so there is no real need to swap furniture to compensate. if I did have a 5.45 upper to swap out I would probably go with a MOE handguard and red dot to lighten up the front for easier off hand shooting. it depends on if you want a wabbit swayor or a long range coyote thumper. more weight up front stabilizes the gun from a rest position but less weight up front puts less stress on the non firing arm while shooting free hand.
5.45 Shooter
New member
If you like to shoot 100rds at a time you could try one of these 100rd mags.
http://centerfiresystems.com/drum-ar-100.aspx
I know they are made for the .223/5.56 but they will also work for the 5.45.
Just be alert to what mags have which ammo in them if you are shooting ,223 ARs with the 5.45s. I have found some duct tape on the mag with the cal. on it helps a lot.
Full mag of 5.45.
Full mag of .223/5.56
Make sure you use the dry lube on the follower before you load your ammo.
My S&W 5.45 AR just eats them up.
