Load development help needed

[huntoregon]

I am attempting to work up a load for my 7PRC. Using H-1000 and Federal 215 primers. Hodgdon and Hornady both listed 67.2 as max while Berger listed 70.6 as max powder charge. So I loaded up 11 rounds starting at 65.0 in .5 grain increments up to 70.0 just looking for pressure. Well I never found any sign of pressure up to 70. Would you guys keep going until you found it? I will also attach the 11 shot chronograph data so you guys can see. I didn't really see any areas that looked like a node up top.

 

[Huntnful]

You're plenty close to pressure with a 175gr. bullet and H1000 with that 70gr. charge. If that's virgin brass, you'll likely be in pressure with the next firing.

 

[lancetkenyon]

70.0 has to be close. I have hit 70.5, but that is about it.

Did you shoot that ladder at distance? Like 400 yards or more?
To me, a flat velocity between charge weights in almost meaningless with 1 shot per charge weight without seeing how barrel harmonics come into play for vertical dispersion.

 

[Bob Wright]

You can keep creeping up at .2 grain intervals if you know how to look for pressure signs.
I see the top 4 have 2 possible nodes. On that, what did the target show in this area? That tells a lot of the story. Many times larger ES is not an indicator of accuracy. The targets give you a lot of data.

 

[huntoregon]

70.0 has to be close. I have hit 70.5, but that is about it.

Did you shoot that ladder at distance? Like 400 yards or more?
To me, a flat velocity between charge weights in almost meaningless with 1 shot per charge weight without seeing how barrel harmonics come into play for vertical dispersion.

No I did not shoot at distance. So you recommend shooting groups of the same charge weight over several powder charges?

Also another rookie question, what type/size target do people use to shoots groups at distance?

 

[huntoregon]

You can keep creeping up at .2 grain intervals if you know how to look for pressure signs.
I see the top 4 have 2 possible nodes. On that, what did the target show in this area? That tells a lot of the story. Many times larger ES is not an indicator of accuracy. The targets give you a lot of data.

To be honest it was a semi wasted trip. It was about a 30 minute drive to get where I was shooting. Fog rolled in thick for a while and I couldn't even see my target at 100 yards for several of the shots. I was more or less trying to find pressure and crossing my fingers I may see a node along the way. Probably not a great method.

 

[huntoregon]

You're plenty close to pressure with a 175gr. bullet and H1000 with that 70gr. charge. If that's virgin brass, you'll likely be in pressure with the next firing.

It was once fired Hornady brass.

 

[huntoregon]

Maybe my question should have been what should my next step be? Keep looking for pressure or try to start a load with ranges around one of these?

 

[Bob Wright]

Maybe my question should have been what should my next step be? Keep looking for pressure or try to start a load with ranges around one of these?

With some of the comments above you might just call 70 as max and re-shoot 5 each of the top four and see what shows up on paper out farther like 200 to 300 yards if you have the distance available. Looking for vertical dispersion. Not much to go on without target data.

 

[Huntnful]

Maybe my question should have been what should my next step be? Keep looking for pressure or try to start a load with ranges around one of these?

With some of the comments above you might just call 70 as max and re-shoot 5 each of the top four and see what shows up on paper out farther like 200 to 300 yards if you have the distance available. Looking for vertical dispersion. Not much to go on without target data.

Exactly what Bob said is what I would do as well

 

[huntoregon]

With some of the comments above you might just call 70 as max and re-shoot 5 each of the top four and see what shows up on paper out farther like 200 to 300 yards if you have the distance available. Looking for vertical dispersion. Not much to go on without target data.

Ok I will give this a try. One more question I have, if it shoots good at 2-300 yards but S.D. Is not good do you guys worry much? I would like to trust this load to hunt out to at least 700 yards. I guess if it groups at 300 I'll stretch it out to 700 and see?

 

[Bob Wright]

Ok I will give this a try. One more question I have, if it shoots good at 2-300 yards but S.D. Is not good do you guys worry much? I would like to trust this load to hunt out to at least 700 yards. I guess if it groups at 300 I'll stretch it out to 700 and see?

Absolutely stretch it out after you see good results from whatever node you want to work in. The node should allow you to have some variation in powder measurement and not throw rounds out of a group. +/-.1 grain type tolerance should print "tight" groups. You have work to do. You may find nothing works and starting with another powder. Stick with it.

 

[BRADMOTO]

Ok I will give this a try. One more question I have, if it shoots good at 2-300 yards but S.D. Is not good do you guys worry much? I would like to trust this load to hunt out to at least 700 yards. I guess if it groups at 300 I'll stretch it out to 700 and see?

More will choose a load that shoots great, but not so great SD. I know nobody that shoots a terrible grouping load because it has a great single digit SD. Lord knows how many have shot great and never knew their tech data.

A technique I found works great for detecting pressure increases before anything else is to track the relative measurement of the primer pockets. Spin the top/opposing blades of the calipers inside the primer pocket. If that size increases more that .001 the first firing you are into pressure. You choose how long you want the brass to last. Pressures that blow a pocket to 0005 will last lots of loadings. Pressures that blow the pocket over .001 from virgin state, not so many more loadings.

 

[Mike6158]

Lance hit on the point I was going to make. It took me far too long to warm up to using SD. I'll go looking for a good SD with 5 shot groups. If I run into pressure issues with the first round, I set that group of 5 (4 remaining) and anything with a higher charge weight aside and pull the bullets / dump powder when I get home. If a low (single digit preferably) SD shows up in one of more of the 5 shot groups I reshoot it and the charge either side of it with 10 shot groups. Shooting 5 for single digit SD is like going fishing with more than one bait. You might find one bait that works great on the day your shooting fishing with it but not work so great later. Just for fun (I like to reload and shoot so...) I did a test. I loaded 20 rounds at the same powder charge. I put them in a my load data spreadsheet, modified for 20 rounds instead of 10. Then entered the data in 4 groups of 5, 2 groups of 10, and finally one group of 20 in the order that I shot them. I shot groups of 5 then took that data and copied it, in order, to the groups of 10 column, then combined the groups of 10 into the 20 column. The point was to see what shot count did to SD.

It looked like this (read it right to left, that's the order I shot it):