Can a 5.45x39 upper receiver fit a 5.56 lower receiver?

Formyguns · December 23, 2011, 07:57 PM

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.

357 Python · December 23, 2011, 08:03 PM

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.

Formyguns · December 23, 2011, 08:24 PM

Never thought about that but that makes sense

pilpens · December 23, 2011, 11:10 PM

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.
=============
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.
=============

Logs · December 24, 2011, 07:19 AM

Yes, I use to have one.

tahunua001 · December 24, 2011, 12:07 PM

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.

Formyguns · December 24, 2011, 12:49 PM

I was looking at the spikes tactical lower. When i go to the range i like to shoot atleast 100 rounds. Thanks for all the advice, and this helps me a lot!

Formyguns · December 24, 2011, 01:10 PM

Also is there any attachments, stocks, ris systems, etc that you guys prefer for a 5.45x39 ar rifle?

tahunua001 · December 24, 2011, 05:58 PM

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 · December 24, 2011, 06:55 PM

Quote:

I was looking at the spikes tactical lower. When i go to the range i like to shoot atleast 100 rounds. Thanks for all the advice, and this helps me a lot!

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.

December 23, 2011, 07:57 PM	#1
Formyguns Junior Member Join Date: December 23, 2011 Posts: 4	Can a 5.45x39 upper receiver fit a 5.56 lower receiver? 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.

December 23, 2011, 11:10 PM	#4
pilpens Senior Member Join Date: April 24, 2008 Location: Ohio Posts: 1,696	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. ============= 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. ============= Last edited by pilpens; December 23, 2011 at 11:20 PM.

December 24, 2011, 12:07 PM	#6
tahunua001 Senior Member Join Date: July 21, 2011 Location: Idaho Posts: 7,839	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. __________________ ignore my complete lack of capitalization. I still have no problem correcting your grammar. I never said half the stuff people said I did-Albert Einstein You can't believe everything you read on the internet-Benjamin Franklin

December 24, 2011, 05:58 PM	#9
tahunua001 Senior Member Join Date: July 21, 2011 Location: Idaho Posts: 7,839	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. __________________ ignore my complete lack of capitalization. I still have no problem correcting your grammar. I never said half the stuff people said I did-Albert Einstein You can't believe everything you read on the internet-Benjamin Franklin

December 23, 2011, 08:03 PM	#2
357 Python Senior Member Join Date: June 7, 2007 Location: Charlottesville, VA Posts: 941	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.

December 23, 2011, 08:24 PM	#3
Formyguns Junior Member Join Date: December 23, 2011 Posts: 4	Never thought about that but that makes sense

December 24, 2011, 07:19 AM	#5
Logs Senior Member Join Date: November 26, 1999 Location: BLUEGRASS STATE KY USA Posts: 1,780	Yes, I use to have one.

December 24, 2011, 12:49 PM	#7
Formyguns Junior Member Join Date: December 23, 2011 Posts: 4	I was looking at the spikes tactical lower. When i go to the range i like to shoot atleast 100 rounds. Thanks for all the advice, and this helps me a lot!

December 24, 2011, 01:10 PM	#8
Formyguns Junior Member Join Date: December 23, 2011 Posts: 4	Also is there any attachments, stocks, ris systems, etc that you guys prefer for a 5.45x39 ar rifle?