A good pal is now a retired SEAL. He was a career long distance guy. Went to work for a long arm manufacturer and is now teaching again. He - and so many other SEAL NCOs and Warrants - helped me over the years while I was an intel geek for the SEALS. Thought I'd share his input.
I recently asked him about a break in for my new MR556. Here is what he advises:
Biggest thing on the chamber types mostly applies to guns with .223 barrels as they need to be careful not to shoot 5.56 mm. The 5.56 mm ammo your gun will shoot is 5.56x45. Your gun will shoot either .223 or 5.56.
The biggest concerns would be price, level of accuracy desired, or effect desired (i.e. hunting or home defense or limited penetration). Black Hills or Hornady in a 75-80 grain BTHP would be my choice, at least to start, for an accuracy and defense round.
When I say starting, I mean buy it, shoot and zero with it and see if it meets your accuracy needs at the distance you want.
After that for just target shooting I would use either a .223 or 5.56 in 62-64 grain medium quality like American Eagle made by Federal or other similar type depending on cost.
I would not buy cheap steel jacket rounds if there are any in those calibers or steel projectile ammo, stick to brass cartridges and copper jacketed rounds. I would also not buy someone else's reloads under any circumstances.
I would break in the barrel following the steps below. Some folks say it is a superstition but if it is, it won't hurt to do it!
Clean bore, shoot 1 round, clean bore, repeat process through first 10 rounds.
Then repeat shooting 2 rounds fast, clean, 3 rounds fast, clean, 5 rounds fast, clean.
Cleaning should be done with a good copper cutting solvent like Shooter's Choice. Keep muzzle end lower than chamber end to prevent excess fluid from entering trigger/lower receiver area as it is corrosive.
Use a bore guide made for AR-15. Always patch after using this fluid till barrel is dry and when finished for the day run a final patch through with Breakfree to apply a light coat to the inside of barrel for storage.
I recently asked him about a break in for my new MR556. Here is what he advises:
Biggest thing on the chamber types mostly applies to guns with .223 barrels as they need to be careful not to shoot 5.56 mm. The 5.56 mm ammo your gun will shoot is 5.56x45. Your gun will shoot either .223 or 5.56.
The biggest concerns would be price, level of accuracy desired, or effect desired (i.e. hunting or home defense or limited penetration). Black Hills or Hornady in a 75-80 grain BTHP would be my choice, at least to start, for an accuracy and defense round.
When I say starting, I mean buy it, shoot and zero with it and see if it meets your accuracy needs at the distance you want.
After that for just target shooting I would use either a .223 or 5.56 in 62-64 grain medium quality like American Eagle made by Federal or other similar type depending on cost.
I would not buy cheap steel jacket rounds if there are any in those calibers or steel projectile ammo, stick to brass cartridges and copper jacketed rounds. I would also not buy someone else's reloads under any circumstances.
I would break in the barrel following the steps below. Some folks say it is a superstition but if it is, it won't hurt to do it!
Clean bore, shoot 1 round, clean bore, repeat process through first 10 rounds.
Then repeat shooting 2 rounds fast, clean, 3 rounds fast, clean, 5 rounds fast, clean.
Cleaning should be done with a good copper cutting solvent like Shooter's Choice. Keep muzzle end lower than chamber end to prevent excess fluid from entering trigger/lower receiver area as it is corrosive.
Use a bore guide made for AR-15. Always patch after using this fluid till barrel is dry and when finished for the day run a final patch through with Breakfree to apply a light coat to the inside of barrel for storage.
I wonder how much life is left in the barrels of some of my guns.