28n 155 hammers and n570

[JMack]

Something weird going on can't put my finger on it. ordered a sample pack and just started tinkering here are some results:
This is with ADG brass 2x fired, CCI magnum 250 primers jumping .03" using a prochrono

85gr (1-1/2" group @ 100)
1st 3127
2nd 3176
3rd 3209

85.5 (3" group @ 100)
1st 3158
2nd 3222
3rd 3163

86.0 (.63" group @ 100)
1st 3172
2nd 3085
3rd 3248

i have brand new batteries in the chrono and my load development with the accubonds and retumbo has been consistent with no crazy readings all else is equal. What's up with the speeds all over the place?

 

[JMW67]

Something weird going on can't put my finger on it. ordered a sample pack and just started tinkering here are some results:
This is with ADG brass 2x fired, CCI magnum 250 primers jumping .03" using a prochrono

85gr (1-1/2" group @ 100)
1st 3127
2nd 3176
3rd 3209

85.5 (3" group @ 100)
1st 3158
2nd 3222
3rd 3163

86.0 (.63" group @ 100)
1st 3172
2nd 3085
3rd 3248

i have brand new batteries in the chrono and my load development with the accubonds and retumbo has been consistent with no crazy readings all else is equal. What's up with the speeds all over the place?

just curious did you clean the copper from the barrel before shooting the hammers

 

[JMack]

Yes. Thoroughly

 

[JMW67]

Yes. Thoroughly

might give steve a shout

 

[Capt RB]

If the chrono is correct I don't think you are getting to the proper pressure.
I just don't think your chrono is working correctly

 

[JMack]

If the chrono is correct I don't think you are getting to the proper pressure.
I just don't think your chrono is working correctly

I guess it's possible

 

[JMack]

If the chrono is correct I don't think you are getting to the proper pressure.
I just don't think your chrono is working correctly

Maybe I should jump them a little more

 

[Mram10us]

Do you have a borescope to check for a carbon ring?

 

[JMack]

Do you have a borescope to check for a carbon ring?

I do not. I have 87 rounds on this barre.

 

[Capt RB]

Maybe I should jump them a little more

Can you jam them? it builds pressure faster

 

[Mram10us]

I do not. I have 87 rounds on this barre.

Ryan Pierce and others who do a lot of 28 nosler stuff have mentioned the need for cleaning very often. I think he said 30 rounds. I also use n570 and have to get that ring out every 20-30 rounds. Huge difference in accuracy.

 

[JMack]

Ryan Pierce and others who do a lot of 28 nosler stuff have mentioned the need for cleaning very often. I think he said 30 rounds. I also use n570 and have to get that ring out every 20-30 rounds. Huge difference in accuracy.

I've cleaned after each range trip, typically 10-15 rounds. I use cu2 bore tech run a few wet patches through let it sit flat overnight the scrub with brush then few more patches with cu2 which progressively come out cleaner as I go then dry patch which comes out pure white. I use a proof positive jag.

 

[JMack]

Can you jam them? it builds pressure faster

I'm not sure suppose I could

 

[RockyMtnMT]

I think you are not building enough pressure to get consistent burn. The last 28n that we loaded with n570 and the 155g HH we started at 84g and finished at 87g with a vel of 3470 fps. This was with Nosler brass which is soft. 3.50" coal. Loaded another with the same and finished at 88g with a vel of 3340 fps. The slow powder will do better with some pressure. Work up carefully.