Lapua Center X trending higher over time?

[USMC22]

04/15/2024 - 20 Shots - 1072.2 MAX - 1040.4 MIN - 1055.8 AVE - 31.8 ES - 8.3 SD Notes: 54*F 68% RH 28.92inHG SP 963' DA 80 Fouling Shots
04/17/2024 - 50 Shots - 1077.9 MAX - 1039.9 MIN - 1062.9 AVE - 38.1 ES - 6.4 SD Notes: 44*F 45% RH 29.34inHG SP -167' DA 100 Fouling Shots
05/03/2024 - 50 Shots - 1082.3 MAX - 1041.1 MIN - 1060.7 AVE - 41.2 ES - 8.1 SD Notes: 59*F 59% RH 29.34inHG SP - 771' DA 0 Fouling Shots CCB
05/20/2024 - 155 Shots - 1100.1 MAX - 1056.6 MIN - 1075.8 AVE - 43.5 ES - 7.9 SD Notes 66*F 63% RH 29.17inHG SP - 1430' DA 100 Fouling Shots
Averages 1083.13 1044.5 1063.8. 38.7 7.7

Above is my log for a lot of Lapua Center X. Wondering if the trending higher velocities is the barrel "breaking in" or possibly temp related. Extreme spreads and standard velocity are staying around ~ 38.7 and 7.7 FPS respectively but the MAX, MIN and AVE are creeping up.

Using a Garmin Xero Chrono.

Rifle is a Vudoo 360 w/ a 24" 1:16R 5 Groove 1.20" Bartlein Barrel.

 

[oldrifleman]

Are these shots at a paper target or at steel? If paper how were the groups? Fact is that's what really matters.

 

[USMC22]

Are these shots at a paper target or at steel? If paper how were the groups? Fact is that's what really matters.

It isn’t holding me back. On paper.

 

[justin amateur]

4/15 to 5/20....I'd be looking at temperature related velocity increase.

Check weather records for the day/time shot.
Compare velocity to temperatures, see how they relate.

 

[USMC22]

4/15 to 5/20....I'd be looking at temperature related velocity increase.

Check weather records for the day/time shot.
Compare velocity to temperatures, see how they relate.

Environmentals are in the notes following each chrono session obtained from a kestrel elite

 

[oldrifleman]

It isn’t holding me back. On paper.

If this started as a new barrel I would write it off as breaking in, If it is an existing barrel with several hundred rounds through it, I would be left scratching my head. In the end the result are what matters and what everyone will remember.

 

[USMC22]

If this started as a new barrel I would write it off as breaking in, If it is an existing barrel with several hundred rounds through it, I would be left scratching my head. In the end the result are what matters and what everyone will remember.

Brand new from Vudoo no rounds through prior. Approaching 500 rounds total through it.

 

[oldrifleman]

I will be interested in the round count where it stabilizes, I would bet it does in the next brick or so. What brand barrel?

 

[justin amateur]

D'oh! Never used a Kestrel, whizzed right past the data. dumadze.

12 degree increase would change the rate of combustion reaction.
Higher pressure peak, higher velocity.
Type of powder changes how temperature affects burn rate.

Temperature Effects on Gunpowder Explained - Guns and Ammo

Have you shot ammunition in the winter without issue, only to experience stiff bolt lift and cratered or pierced primers in the summer heat?

www.gunsandammo.com

 

[Williwaw]

What brand barrel?

Refer to post1

 

[USMC22]

I will be interested in the round count where it stabilizes, I would bet it does in the next brick or so. What brand barrel?

24” bartlein 1.20” straight

 

[grauhanen]

Two things worth keeping in mind.

One is that different boxes of ammo from the same lot can easily have different average muzzle velocities.
The other is that temperature affects MV averages. As temps go up, so too do MV averages.

 

[USMC22]

Two things worth keeping in mind.

One is that different boxes of ammo from the same lot can easily have different average muzzle velocities.
The other is that temperature affects MV averages. As temps go up, so too do MV averages.

Tracking that, it hasn’t been a huge shift in temp.

 

[Jefe's Dope]

I'm assuming it's all from the same lot #. Can you post the lot number so we can see what Lapua states what speed they have it at?

 

[USMC22]

I'm assuming it's all from the same lot #. Can you post the lot number so we can see what Lapua states what speed they have it at?

Yes all same lot # 24558/704186

 

[acourvil]

I don’t have solid data, but I will say that I stopped shooting the lot of Center-X that I have when the temp drops below 60F because the speed drops off noticeably.

 

[USMC22]

I don’t have solid data, but I will say that I stopped shooting the lot of Center-X that I have when the temp drops below 60F because the speed drops off noticeably.

That's 99.9% of the year here in New Hampshire. Seriously we have like 10 minutes where the mosquitoes big enough to carry you away come out and then they die and it starts snowing.

 

[oldrifleman]

Mine seems to be good at least down to 40 ( I don’t shoot colder than that).

 

[Jefe's Dope]

Your overall average tracks w/ the lot #. 324 m/s = 1063 fps. It's surprising to see it speed up from 54* to 44* and then slow down at 59*. But at 66* is speeds back up again, which would be "normal". I would say that since it's a new barrel, this might be somewhat expected and tracks as it's slow at first then speeds up at a lower temp. But then is slows down again at a higher temp only to speed up at the highest temp. At this point I would consider the barrel broken in and expect it to stabilize at the last speed shown. This is assuming you're posting these results in chronological order. .22lr is definitely temp sensitive. I lost 2/10s, ballistic calculator, of MRAD value at 200 yards on Saturday as the temps rose and was seeing this on target shooting CX.

I chrono'd 35 rounds Saturday morning before the match confirming dope using the Garmin and my numbers were: Max = 1110.0, Min = 1060.6, ES = 49.4, SD = 9.0, and AVG = 1084.9.

This was the last of that brick and I chrono'd the new brick. It was a lot faster. 19 rounds (shot 20 but only picked up 19) and this is what I got: Max = 1108.3, Min = 1078.2, ES = 30.1, SD = 7.8, AVG = 1092.9.

I hope this helps you figure it out. Again, I would expect your numbers to settle in at the last series you shot. FYI, I probably have close to 10,000 rounds on my Ace barreled Vudoo. I would remove any fouling shots on a clean barrel and use the remaining rounds as my dope.

 

[USMC22]

@Jefe's Dope I’ve got probably 3k rounds left of this lot. Are you saying I should clean the barrel and just dope the rifle vs getting more data points?

The Garmin zero is nice just setting up and getting the chrono data while I shoot anyways.

 

[Jefe's Dope]

@Jefe's Dope I’ve got probably 3k rounds left of this lot. Are you saying I should clean the barrel and just dope the rifle vs getting more data points?

The Garmin zero is nice just setting up and getting the chrono data while I shoot anyways.

Yes. But still chrono to see if it's doing the same as above or has settled in. I would think that after nearly 300 rounds, the barrel is broken in. I don't think there's much breaking in on the barrel to begin with. It's more the chamber and throat. Lead is very soft and just generally fils the pits and grooves. Wouldn't hurt to test another brick of another lot number either. But yes, find dope on targets and shoot it.

 

[USMC22]

Yes. But still chrono to see if it's doing the same as above or has settled in. I would think that after nearly 300 rounds, the barrel is broken in. I don't think there's much breaking in on the barrel to begin with. It's more the chamber and throat. Lead is very soft and just generally fils the pits and grooves. Wouldn't hurt to test another brick of another lot number either. But yes, find dope on targets and shoot it.

Sounds like a plan. I’ve got another 5k of a different lot# center x. Next range trip I’ll do both.

 

[silphidae]

CenterX is fairly linear when I do MV Temp. The temperature is of the actual ammo that I put in coolers and has about an hour to stabilize at that temp. Been pretty reproducible with multiple lots.

 

[1911Shootist]

Looks like it trends with temp and within +/- 1 SD.