Barrels

[outerlimits]

ok, looking for theories as to why some barrels like certain bullets, while others don't. personally, i've had 4 AR barrels over time. the last two were JP 18", same contour. on the first, it loved 77's. on my newest one, it can't hold a group with anything above 69's. both loved 55 NBT's. go figure. IAC, im curious what theories there might be as to the variances.

[Graham Smith]

ok, looking for theories as to why some barrels like certain bullets, while others don't. personally, i've had 4 AR barrels over time. the last two were JP 18", same contour. on the first, it loved 77's. on my newest one, it can't hold a group with anything above 69's. both loved 55 NBT's. go figure. IAC, im curious what theories there might be as to the variances.

Have you factored in the twist rate? It makes a huge difference.

[TruePunisher]

Have you factored in the twist rate? It makes a huge difference.

If they are both 18" JP mid-weight barrels bought within the last few years they would both be 1:8.

[Dan Sierpina]

I think that minute differeces in the batches (heat) of the steel, can give different harmonics. The same barrel, with the length shortened can turn into a tack driver. I have a barrel that the original owner, said didn't shoot. I rebarreled the rifle and for the heck of it, shortened it 1 1/2" to 18 1/2" It turned into a sub 1/2 moa barrel.

[3gunpinoy]

I think that minute differeces in the batches (heat) of the steel, can give different harmonics. The same barrel, with the length shortened can turn into a tack driver. I have a barrel that the original owner, said didn't shoot. I rebarreled the rifle and for the heck of it, shortened it 1 1/2" to 18 1/2" It turned into a sub 1/2 moa barrel.

could it be that the original barrel had a bad crown and once you shortened it, put in a new crown, then it worked better?

[jobob]

I've been doing some work with a BCM 16" stainless with 1:8 twist. It doesn't want to shoot 55s, but groups the 69s and 75s well. That's nice, but I really want it to shoot 55s, cause I want to shoot it a lot and they are cheaper. I'm thinking of selling and getting a JP.

[Wicked Wrister]

How the upper is assembled has a lot to do with it also. It's difficult to do a side-by-side comparison on two of the "same" barrels because they are going in two "different" upper receivers with two "different" handguard assemblies holding everything together and who put everything together and how means something. Those little tolerances can have a noticeable affect, not to mention the earlier comment about variation in the barrel making process. Then how the scope/irons are installed and set-up, and on and on and on... Tough to quantify and it's too bad those true tack-drivers won't last forever!

[mpeltier]

ok, looking for theories as to why some barrels like certain bullets, while others don't. personally, i've had 4 AR barrels over time. the last two were JP 18", same contour. on the first, it loved 77's. on my newest one, it can't hold a group with anything above 69's. both loved 55 NBT's. go figure. IAC, im curious what theories there might be as to the variances.

Thats a tough question to answer, as there are so many things from Manufacturing tolerances, tool wear, ammo, poor upper quality/assembly,bbl harmonics, and how you are shooting on a given day. Sometimes you just need to feed it what it likes, or you change bbls until it does what you like. I have found the best consistancy from the premium bbl makers who specialize in well....just top notch bbls.

[RH45]

I've been doing some work with a BCM 16" stainless with 1:8 twist. It doesn't want to shoot 55s, but groups the 69s and 75s well. That's nice, but I really want it to shoot 55s, cause I want to shoot it a lot and they are cheaper. I'm thinking of selling and getting a JP.

Try 50, or 52 grain. I don't remember which one ran well in my old 1-8, but, I do remember that it didn't like the 55s.

[benny hill]

After shooting preminum barrels for 30 yrs, I have found they are like people, each has a personalty of it's own. You have to find what it likes & feed it.

[Dan Sierpina]

I think that minute differeces in the batches (heat) of the steel, can give different harmonics. The same barrel, with the length shortened can turn into a tack driver. I have a barrel that the original owner, said didn't shoot. I rebarreled the rifle and for the heck of it, shortened it 1 1/2" to 18 1/2" It turned into a sub 1/2 moa barrel.

could it be that the original barrel had a bad crown and once you shortened it, put in a new crown, then it worked better?

Since I had machined that particular barrel from a blank, I rather doubt that I had messed the crown the first time, then did it right the second.

Some years back, a bunch of benchrest shooters had access to a warehouse, where they "played" with no wind or lighting changes to add variables to their testing. They found that a 6PPC shot best at a specific length. This was using the same contour barrels. Minor changes in the harmonics of a barrel can impact group size. Just look at the Browning BOSS system and it's ability to make groups shrink of grow, at the twist of the unit.