slow speed in 40 degree temp.

[wlaursen]

I changed lot of H4895 from 5715 (last 4 oz) to 5825. I did load testing at the 1000 yd BR match last week. The first relay for lg and hg shoot 30.5 gn, second relay 30.6 gn, and third relay 30.7. I shoot poor, this is the same gun and barrel that I finished 2nd overall at lg national in Octorber. Last week I did a test using Labradar with ammo from the last match and some from the nationals (5715, 30.7 gn, 2/16/21 speed was 2950) last week speed was 2900. 6BRA, 28 in barrel, bart's 105 (+007), BR4. lot 5825 speeds were 2883, 2884. and 2908. I called Jeff Locke, to see if he had any ideas on the slow speed, because he lived in Seattle. He had no clue for a 40+ drop in speed. Anyone have a clue?

 

[JFrank]

Trolling…
I shot that lot number last Aug at the nationals, I don’t have a labradar though.

 

[JEFFPPC]

You mention 40 degree temp now but did not mention temp from October. If you went from say 70 to 40 degrees that is a definite speed loss. Change lots of powders speed might go up, might go down, and of your a lucky fellow on ocassion it might stay the same. You have 2 very obvious reasons for a velocity change certainly big enough to take you out of your node. When you hear non temp sensetive thing of a politician giving a speech.

 

[BartsBullets]

I changed lot of H4895 from 5715 (last 4 oz) to 5825. I did load testing at the 1000 yd BR match last week. The first relay for lg and hg shoot 30.5 gn, second relay 30.6 gn, and third relay 30.7. I shoot poor, this is the same gun and barrel that I finished 2nd overall at lg national in Octorber. Last week I did a test using Labradar with ammo from the last match and some from the nationals (5715, 30.7 gn, 2/16/21 speed was 2950) last week speed was 2900. 6BRA, 28 in barrel, bart's 105 (+007), BR4. lot 5825 speeds were 2883, 2884. and 2908. I called Jeff Locke, to see if he had any ideas on the slow speed, because he lived in Seattle. He had no clue for a 40+ drop in speed. Anyone have a clue?

My guess would difference in speed produced by changing lots of 4895 combined with different temp.

4895 varies vastly from lot to lot, as well as all powders speed up and slow down depending on environmental conditions.

Bart

 

[newbieshooter]

Puzzling is that using the same lot H4895 (5715):

1. After load development (lot 5715) back in Feb 2021 (2/16/21): speed measured 2950. (40-55 degrees?)

2. Shoots Nats (5715) in October (50-55 degrees) and shot super (speed not measured?)

3. Last week -> takes left over rounds from Nats (same 5715 load shot all year) - @ 40 degrees: speed measured 2900.

 

[BartsBullets]

What makes this a puzzle is that using the same lot H4895 (5715):

1. After load development (lot 5715) back in Feb 2021 (2/16/21): speed measured 2950. (40-55 degrees?)

2. Shoots Nats (5715) in October and shot super (speed not measured?)

3. Last week -> takes left over rounds from Nats (same 5715 load shot all year) - @ 40 degrees: speed measured 2900.

Missing a lot information. Would have been nice to know how fast it was shooting at the Nationals. Also if he could have freshly loaded rounds from each different lot of powder to test velocity.

I see large swings in velocity going to a different ranges even tho the weather Conditions and altitudes are close to the same. I know from my place to Memphis I need to add 2 to 3 tenths if not I’ll be slow.

Sounds like he needs to go back to the drawing board and retune.

Bart

 

[wlaursen]

Bart, the barrel was clocked on 2/16/21 at 2950. I set the score records on 2/28/21 (were disallowed for bad target handling). The barrel was pulled and not shoot until the nationals (mid 50's to 60's). The 2/16/21 and the 12/21/21 tests were at the same range, only deference's is temperature. My shooting notes for matches include loading data, range conditions , but not temperature. I have shoot some F-Class match in 30 degrees, but the loads allways shoot the same. I'm going to rerun the test, but I'm going to use my P35 and my labradar to test both.

 

[BartsBullets]

Bart, the barrel was clocked on 2/16/21 at 2950. I set the score records on 2/28/21 (were disallowed for bad target handling). The barrel was pulled and not shoot until the nationals (mid 50's to 60's). The 2/16/21 and the 12/21/21 tests were at the same range, only deference's is temperature. My shooting notes for matches include loading data, range conditions , but not temperature. I have shoot some F-Class match in 30 degrees, but the loads allways shoot the same. I'm going to rerun the test, but I'm going to use my P35 and my labradar to test both.

For what it’s worth I usually see H4895 (generally speaking) change velocity about 1fps per degree. Things like humidity, density altitude, moisture content, can effect the bullet’s speed but as rule of thumb 1 ft per degree works pretty well.

Bart

 

[JFrank]

Looking at my notes from last March around 30 degrees that lot number shot 30.5 at 2943-2956
Than again in May around 60-70 degrees that same charge ran 2969
My elevation is 2000 ft

 

[LCazador]

Bart, the barrel was clocked on 2/16/21 at 2950. I set the score records on 2/28/21 (were disallowed for bad target handling). The barrel was pulled and not shoot until the nationals (mid 50's to 60's). The 2/16/21 and the 12/21/21 tests were at the same range, only deference's is temperature. My shooting notes for matches include loading data, range conditions , but not temperature. I have shoot some F-Class match in 30 degrees, but the loads allways shoot the same. I'm going to rerun the test, but I'm going to use my P35 and my labradar to test both.

Always record humidity and temp with every load test as well as the other conditions you mentioned above. My experience with different powder lots has been similar to Barts. I think you need to retune with your new lot of powder. Try a new seating depth too.

 

[KenOath]

I changed lot of H4895 from 5715 (last 4 oz) to 5825. I did load testing at the 1000 yd BR match last week. The first relay for lg and hg shoot 30.5 gn, second relay 30.6 gn, and third relay 30.7. I shoot poor, this is the same gun and barrel that I finished 2nd overall at lg national in Octorber. Last week I did a test using Labradar with ammo from the last match and some from the nationals (5715, 30.7 gn, 2/16/21 speed was 2950) last week speed was 2900. 6BRA, 28 in barrel, bart's 105 (+007), BR4. lot 5825 speeds were 2883, 2884. and 2908. I called Jeff Locke, to see if he had any ideas on the slow speed, because he lived in Seattle. He had no clue for a 40+ drop in speed. Anyone have a clue?

I’m not convinced my lab actually agrees with itself when taking it out on different days, weeks or months apart or next day! …even with exactly the same loads.

 

[LRPV]

Labradar and Magneeto speed are the two most trusted chronos on the market today. Anytime I’ve ran both together, if the units didn’t read exactly the same, they were within at most 2fps and most generally only 1fps different. With that said, neither is 100% due to the fact that humans do have to set them up.

 

[KenOath]

Im Not questioning there accuracy on the day, but I have questioned my day to day speed differences everything being equal accept the date and maybe 1/2” placement difference either way on the bench or ground..

 

[LRPV]

Im Not questioning there accuracy on the day, but I have questioned my day to day speed differences everything being equal accept the date and maybe 1/2” placement difference either way on the bench or ground..

I feel pretty confident in my Labradar but with that said, the way I set up is exactly the same every time too. IF that makes a difference, I don’t know.

 

[Ned Ludd]

I have directly compared velocities obtained using different Lot#s of H4895 on numerous occasions (i.e. using identical brass, charge weight, primer, bullet, different Lot#s of powder, velocity determined on the same range trip). Although velocities obtain with different Lot#s of H4895 are usually well within 10-15 fps of one another, I have had a couple Lot#s where the velocity differed by as much as 75 fps for the exact same charge weight. You may have encountered such a Lot.

It's important to note that the velocity of a tuned load using the [apparently] much slower Lot of H4895 may or may not be the same as with a previously-developed load using a faster Lot# of H4895. In other words, simply reproducing your previous velocity by increasing the charge weight with the new Lot# of H4895 may or may not reproduce the same precision. You will have to test across a sufficient charge weight range with the new Lot of powder to determine where the new optimal charge weight is located.

 

[LCazador]

I’m not convinced my lab actually agrees with itself when taking it out on different days, weeks or months apart or next day! …even with exactly the same loads.

I have a LabRadar and an Oehler 35P. If I find that I have to take both out on any given day then I will question myself. Never ever think you are done with testing any load!

 

[LCazador]

I have directly compared velocities obtained using different Lot# of H4895 on numerous occasions (i.e. using identical brass, charge weight, primer, bullet, different Lot#s of powder, velocity determined on the same range trip). Although velocities obtain with different Lot#s of H4893 are usually well within 10-15 fps of one another, I have had a couple Lot#s where the velocity differed by as much as 75 fps for the exact same charge weight. You may have encountered such a Lot.

It's important to note that the velocity of a tuned load using the [apparently] much slower Lot of H4895 may or may not be the same as with a previously-developed load using a faster Lot# of H4895. In other words, simply reproducing your previous velocity by increasing the charge weight with the new Lot# of H4895 may or may not reproduce the same precision. You will have to test across a sufficient charge weight range with the new Lot of powder to determine where the new optimal charge weight is located.

^^^ well said!!

 

[KenOath]

I have a LabRadar and an Oehler 35P. If I find that I have to take both out on any given day then I will question myself. Never ever think you are done with testing any load!

Agreed..

 

[JFrank]

Im Not questioning there accuracy on the day, but I have questioned my day to day speed differences everything being equal accept the date and maybe 1/2” placement difference either way on the bench or ground..

I can echo this as well