Barrel to barrel, is it possible?

[lrgrendel]

On my second 24" barrel. First one gave me 2640 FPS with 30.0 g AA2520, CCI 450, 123 g Amax.
Put my new one (2nd) over the Chrony today for the first time during some load development. 29.8 g AA2520, CCI 450, 123 g Amax gave me the following results.

Low 2705
High 2723
Ave 2716
ES 18.26
SD 7.68
This load shot exactly 1 MOA at 100 yds.

I initially thought the Chrony was giving me bad info but then I used it on my 6.5 Creedmoor and all the results were spot on so......

Is it possible to get these velocities from a 24" barrel?? Not sure what is going on. I know for sure these chronographs are not accurate all the time.

[NugginFutz]

Sure, it's possible. You're looking at the real world there, right?

Assuming it's the same barrel, same manufacturer, same profile, same twist, etc. (you get the idea) you could still see a variance in average velocities between barrels. On further assumption, if the chamber is a bonafide compound throated Grendel, then it's possible that you could be seeing pressure spikes from loading too long for that newer barrels profile, resulting in increased velocity. Have you checked for max COAL? Being that this is a new barrel, I'd make a point of measuring your new chamber for max seating.

Having said all this, I would say that a 24" barrel is quite capable of 2700 fps. My 22" BHW is nearly there with factory 123 SST's, at 2645.

Now, where in the world are you finding 2520?

[Kendoist4162]

Now, where in the world are you finding 2520?

What he said!! Inquiring minds would like to know....;-)

[LR1955]

Wait, 2700 with a 24" barrel? What about the guy on this site that keeps posting that you only get 50 fps going from 18" to 24" barrels? What's different here, the powder? Maybe the bullets? Maybe you actually tried a longer barrel?

RHW:

Thats pretty fast with a 123 grain bullet and that load of 2520. I shoot 120's out of a 26" barrel with 30 grains of 2520 and am happy to get 2650.

18 to 24 inch barrel -- probably 25 fps or so per inch but there comes the point where your increases are not as much per inch anymore.

I would get nervous if I were hitting 2700 with a 123. I have hit 2700 with 120's out of an Overwatch and it was very hard on the brass and bolt.

Stranger things have happened.

LR55

[lrgrendel]

Yes, I am slightly nervous, that is why I posted!! I will check the velocity using a friend's magnetospeed chronograph next time out.

Both barrels are the same length and from the same manufacturer and loads were identical. I loaded them to 2.245 "( same as factory ) I will change seating depths once I find a good load.

I bought 8 lbs of AA2520 about 18 months ago, and have 2.5 lbs of that left. Recently I picked up another 4 lbs from a buddy.
I have not seen it any where recently.

[Hoser1]

Are you moly coating the bullets? Didn't see anything mentioned, but is possible to get that speed and keep pressures down.

[lrgrendel]

Are you moly coating the bullets? Didn't see anything mentioned, but is possible to get that speed and keep pressures down.

No moly coating

[LR1955]

Maybe you actually tried a longer barrel?

RWH:

You got me digging up some of my load testing from when the Grendel was something new. Maybe eight years ago.

My barrels are made for me by a trusted barrel maker who is not a commercial enterprise.

I bought a couple of Grendel barrels from him over the years. Two of them that I used for testing (before anyone but Alexander had any data) were made at the same time, using the same button, same reamer, same steel, and stress relieved at the same time. So, I doubt anyone could get two barrels made more identically.

One was a 20 inch and one a 26 inch. Both were 1/8 turn twist. I bought them because I was one of those 'guys' who wanted to see the differences between barrel lengths over a variety of uses.

I loaded both with 120 Sierras, CCI 450's, and 30 grains of 2520.

I tested both the same day so the environmental conditions were the same. My chronograph is a CED and I used the external IR lights to ensure uniformity of lighting.

The 20" chronographed at 2438 fps with an SD of 6. Shot about 1 1/2 inches at 200 yards.

The 26" chronographed at 2551 with an SD of 6. Shot about 1 inch at 200 yards.

So, in this case, I got an additional 113 fps from six more inches of barrel length. That comes out to about 20 fps per inch.

My comment about an additional 50 fps for an additional 6 inches was wrong. It is probably around 100 fps.

Some of us were so into the Grendel when it came out that we spent a lot of money and time testing things.

Like buying two basically identical barrels of differing lengths to see the differences.

Anyway, I wish my 26" Match Rifle shot 120 and 123's at 2700 fps but it isn't going to happen. So, if I get 2600 or a little more (31 grains of 2520) and don't need a new bolt after a couple hundred rounds, I am happy.

LR55

[sneaky one]

lr Grendel- see if you can compare to a different chrono.

I trusted mine for 5 years- then after comparing notes with fellow forum members- plus the bullets I sent, with same as load data---etc.-etc.,,

Turns out my chrono is 110-130 fps. too slow on the readout . I'm to try a fileable shim at base - to see if I can salvage the unit, using Factory ammo speeds as a check.

[LRRPF52]

It's possible to hit 2700fps with a 123gr, barrel dependent, but most 24" are closer to 2600fps. Bwild97 got 2740fps with LVR under the 123gr AMAX with his 24" J&T upper.

With max loads of CFE223, I hit 2550fps with a 16" Grendel shooting 123gr AMAX. It wasn't until several increments later at 2640fps that I started to see slight cratering, but that load was well over max. A lot of people might look at their brass and think all was well with that load.

With CFE223, LVR, and AA2520, you can get substantial velocities with 123gr, especially if the barrel runs faster than others. Then you could take the next barrel from the same maker and be 100fps slower with the same load.

[lrgrendel]

Went back out today and put it on a Magnetospeed.

My Chrono is worthless!!

High 2629
Low 2604
Ave 2616
ES 25
SD 8.8

These of course are more realistic. I still have more powders and bullets to try.

Funny this group was terrible at about 2".....

[NugginFutz]

Before you start looking for the trash bin, you may want to check to see if that Crony is not being prevented from unfolding completely (bent or obstructed in some way). More than one member of the Horde has reported issues with some of the folding brands when not opened flat. The net effect of such an event is uncharacteristically high readings due to the shorter distance travelled between the sensors.

[lrgrendel]

Before you start looking for the trash bin, you may want to check to see if that Crony is not being prevented from unfolding completely (bent or obstructed in some way). More than one member of the Horde has reported issues with some of the folding brands when not opened flat. The net effect of such an event is uncharacteristically high readings due to the shorter distance travelled between the sensors.

Haha. Yes I have read that plenty of times before. It is straight. In fact I nearly bent it the other way too much to make sure it was straight.

I am just fed up with it. Not reliable, too many errors and now in accurate.

I may get that Magnetospeed Sport but my brake is fairly long so I need to do some research