I have loaded exactly the same load and had tested them in my .222 Rem Sako and .222 Rem Brno. The Bruno with ordinary grooved barrel had yielded +-50fps faster than the Sako with Micro Grooving. The barrels are the same length. Could this be due to the higher pressure of the ordinary grooved barrel of the Brno? Your advise is appreciated.

A sample of one proves nothing; Try another barrel of each type and the results might be different.
Or it might be what you say; but more data is needed to say for sure.

A hundred barrels of each might prove something then might not.

It is not possible for me to do more tests with other barrels. I was hoping for somebody who had experience on this to give me a probable answer.

The answer is, as you have already found, with those two barrels. One is faster than the other; it is a common occurrence among barrels even with the same type of rifling.

quote:

yielded +-50fps faster

I've had identical barrels give more than that.

Sorry as dpcd said you have proved that one of your barrels is faster than the other. Different chamber can cause that much.

The more you test, the more you will find velocity differences between barrels. You would think a tight barrel would give the highest velocity, and that should be true, but I have a two groove M1903, which ought to be tighter than any four or six groove, and it is the slowest 30-06 barrel I have seen.

You would think that a longer barrel automatically means more velocity, but this week, I took my 29" barreled Swiss M1911 out to the range, and with identical loads, it was just a little slower than 24" K31 Swiss rifles. That surprised me.

It will take gaging and measuring at a capability that none of us have, and even then, it might not prove why one barrel is faster than another.

We were given 5 Mannlicher Luxe rifles in 270 Winchester. All brand new and identical save fir the serial numbers.

We were asked to install scopes, and were provided with Norma 150 grain soft ammo.

Remember, these were identical rifles, from the same manufacturer using the same factory ammo.

The velocity difference between the fastest to the slowest rifle was 150 fps!!!???

We were amazed by this result.

quote:

Originally posted by Reloader270:
I have loaded exactly the same load and had tested them in my .222 Rem Sako and .222 Rem Brno. The Bruno with ordinary grooved barrel had yielded +-50fps faster than the Sako with Micro Grooving. The barrels are the same length. Could this be due to the higher pressure of the ordinary grooved barrel of the Brno? Your advise is appreciated.

As everyone has indicated, comparing only two barrels means nothing.

I'd also like to point out that, unless your Sako .222 is actually a Marlin with a genuine "Microgroove" barrel, then your factory Sako Vixen has a barrel with conventional riflings, only there are 12 rather than the more frequently seen six. It is not a "Microgroove" barrel, but Sako owners often refer to these barrels as "multigroove", indicating the large number of grooves. The Marlin Microgroove barrels (found on the Marlin 322 and 422 rifles built on Sako actions) had more and much shallower grooves than the Sako barrels.

Whether the rifling style, be it conventional, "multigroove" or Marlin's "Microgroove", has any effect on velocity would be very difficult to illustrate even with a larger universe of comparisons since velocity can be affected by chamber dimensions, throat length, throat wear, bore size, bore finish, and a number of other factors.

On a side note; even Marlin does not know what Microgroove means. They marked their 444 and 45-70 barrels as Microgroove, when in fact, they have 12 standard grooves of about .004 deep rifling. First 45-70s have 8. . Not the very shallow, earlier barrels that had .002 or less, deep 16 groove rifling. So, just saying the word Microgroove, could mean different things.