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The AR-10, LR-308, and SR-25 are different rifles that all have something in common. They are all designations for a Large Frame Modern Sporting Rifle (MSR). Small Frame MSRs (aka AR-15s) are commonly chambered in .223/5.56 but also come in a variety of other calibers such as 6.5 Grendel, 7.62x39, 5.45x39, 300 BLK, and more. But if you want an MSR that shoots a larger caliber, like .308 Winchester, 7.62 NATO, or 6.5 Creedmoor ammo, then you need a Large Frame firearm. 
Compatibility of Gun Parts and Tools
Unlike the AR-15, Large Frame MSRs are not standardized. In general, there are 2 main styles of lower receivers: the Armalite AR-10 and the DPMS LR-308/Knight's Armament SR-25. Unlike Small Frame MSRs, getting the right gun parts that match the style or pattern of your lower receiver is paramount. More often than not, rifle parts are not interchangeable between these two patterns. So if you have a DPMS pattern lower receiver, you need a DPMS-pattern barrel, DPMS Bolt Carrier Group (BCG), and DPMS handguard as well. One pattern is not better than the other, although the DPMS pattern tends to offer a wider variety of compatible parts.
While many of the components for a Large Frame MSR are different than those for a Small Frame MSR, there are some common gun parts, such as the safety selector and trigger.Â
The following parts are NOT interchangeable between a Large and Small frame lower receiver:
- Bolt Catch
- Takedown Pins
- Buffer
- Magazine Catch
Other parts, such as the pistol grip, buffer tube, and gun stock, can depend on the pattern of your large frame receiver as well as the manufacturer or design of the component.
Assembly tools will also need to be designed specifically for Large Frame MSRs for the most part, as the majority of parts are larger than AR-15 components. Otherwise, the assembly process is virtually the same as building an AR-15.
What AR-15 Parts Work on an AR-10?
|
AR-15 |
DPMS .308 AR |
Armalite .308 AR |
|
Forward Assist Assembly |
Yes |
Yes |
|
Charging Handle |
No |
No |
|
Ejection Port Cover |
No |
No |
|
Barrel |
No |
No |
|
Barrel Nut |
No |
No |
|
Handguard |
No |
No |
|
Gas Tube |
Yes |
Yes |
|
Gas Block |
Yes |
Yes |
|
Gas Tube Roll Pin |
Yes |
Yes |
|
Bolt Carrier |
No |
No |
|
Trigger |
Yes |
Yes |
|
Hammer |
Yes |
Yes |
|
Trigger and Hammer Springs |
Yes |
Yes |
|
Trigger and Hammer Pins |
Yes |
Yes |
|
Disconnect |
Yes |
Yes |
|
Disconnect Spring |
Yes |
Yes |
|
Bolt Catch |
No |
No |
|
Bolt Catch Roll Pin |
No |
Yes |
|
Bolt Catch Spring and Plunger |
Yes |
Yes |
|
Magazine Catch |
Yes |
No |
|
Magazine Release Button |
Yes |
Yes |
|
Magazine Release Spring |
Yes |
Yes |
|
Pistol Grip |
Yes |
Yes |
|
Pistol Grip Screw and Washer |
Yes |
Yes |
|
Pivot Pin |
No |
No |
|
Takedown Pin |
No |
No |
|
Takedown and Pivot Pin Spring |
Yes |
Yes |
|
Takedown and Pivot Detent |
Yes |
Yes |
|
Safety Selector |
Yes |
Yes |
|
Safety Selector Spring and Detent |
Yes |
Yes |
|
Trigger Guard Assembly |
Yes |
Yes |
|
Buffer Tube |
Yes |
Yes |
|
Buffer |
No |
No |
|
Buffer Retainer |
Yes |
Yes |
|
Buffer Retainer Spring |
Yes |
Yes |
|
Buffer Spring |
No |
No |
|
Receiver End Plate |
Yes |
Yes |
|
Castle Nut |
Yes |
Yes |
|
Buttstock |
Yes |
Yes |
Build an AR-10, LR308, or SR-25 Rifle by Yourself
Whether you build a lower receiver and buy a complete upper receiver, or choose to build the entire rifle yourself, you can have an excellent semi-auto hunting or long-range precision platform as long as you take a little extra care in selecting components.
