Load development help needed

[Bang4theBuck]

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.

Huntoregon,
I listened to a very lengthy, very technical podcast on the Hornady Podcast channel, where their senior ballstician reviewed extensive ballistic details regarding almost everything that could be learned from a test they performed of over 10k shots fired in laboratory-type conditions. Among other things, the test concluded that velocity nodes really do not exist. Meaning all other things being equal‐ more powder equals more pressure, more pressure equals more velocity, period. 'Velocity flat-spots' across increasing powder charges is not any sort of node or sweetspot, etc, it is mearly a representation of the deviation in velocity inherent to the load combo, and loading practices. Stated differently, if you are shooting 3-5 shot groups as an example and two or three different powder charges show similar velocity, this is really jist a result of a small sample size where those particular lower charges were on the higher end of the velocity deviation and the higher charge happenned to be on the lower end of the velociry deviation. The test proved that if you increase your sample size, those different powder charges will always produce a mean velocity that is dissimilar from a higher lower charge.
This kind of puts my whole load development on its head, but 10k+ rounds of testing without any bias toward anything that they market seems like information worth paying attention to.
TAKE THAT FOR WHAT IT IS WORTH! Maybe take a listen to that podcast to hear the details. There were about a dozen theories/myths tested and discussed in that podcast.

 

[huntoregon]

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):

View attachment 649862

Interesting, to look at what we all talk about the more data points the truer the information. Just load all your rounds like 11-15 and you're golden

 

[Mike6158]

Interesting, to look at what we all talk about the more data points the truer the information.

Yup. That's why I did it. I probably could have used something a little more "gentle" to do the test with

If only there was an automatic selector gizmo to pick the best 10 of 20 before I shot them :)

 

[Okanogan]

If you are having issues with SD and using F215 primers with your 7 PRC, I would suggest trying F210 primers. I put maybe 300 chrono graphed loads through my 7 PRC and found F210 primers working better with every powder I tried than the F215s I started with. CCI 250s also worked better than F215s but not as well as the F210s. Using the cooler primers might cost a little velocity but the improved SDs should more than make up for the relatively minor loss at longer ranges.

 

[mdmiller]

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.

Use pin gages instead of calipers, they are cheap.

 

[88mustang]

I use n560 65.8 with 180 Berger bullets I try 9 1/2 mags and 215

My 7prc liked the 9 1/2 large mags

 

[bonie]

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.

I would say your load at 2931.3 is your sweet spot. I would load both sides of that in .2 progression and look for an accuracy load then do steps at .1 around it then play with seating depth. accuracy out ways speed IMOP . a miss is miss and it doesn't matter how fast it is.

 

[BRADMOTO]

Use pin gages instead of calipers, they are cheap.

Maybe, but a set of calipers already on hand is cheaper.

 

[bonie]

I would say your load at 2931.3 is your sweet spot. I would load both sides of that in .2 progression and look for an accuracy load then do steps at .1 around it then play with seating depth. accuracy out ways speed IMOP . a miss is miss and it doesn't matter how fast it is.

@*#!.3 sorry tyepo

 

[RichCoyle]

huntoregon,

I didn't read past your question and I am not conservative. Therefore I would keep going. Might find a good load at a higher velocity.

 

[coastrange]

Huntoregon,
I listened to a very lengthy, very technical podcast on the Hornady Podcast channel, where their senior ballstician reviewed extensive ballistic details regarding almost everything that could be learned from a test they performed of over 10k shots fired in laboratory-type conditions. Among other things, the test concluded that velocity nodes really do not exist. Meaning all other things being equal‐ more powder equals more pressure, more pressure equals more velocity, period. 'Velocity flat-spots' across increasing powder charges is not any sort of node or sweetspot, etc, it is mearly a representation of the deviation in velocity inherent to the load combo, and loading practices. Stated differently, if you are shooting 3-5 shot groups as an example and two or three different powder charges show similar velocity, this is really jist a result of a small sample size where those particular lower charges were on the higher end of the velocity deviation and the higher charge happenned to be on the lower end of the velociry deviation. The test proved that if you increase your sample size, those different powder charges will always produce a mean velocity that is dissimilar from a higher lower charge.
This kind of puts my whole load development on its head, but 10k+ rounds of testing without any bias toward anything that they market seems like information worth paying attention to.
TAKE THAT FOR WHAT IT IS WORTH! Maybe take a listen to that podcast to hear the details. There were about a dozen theories/myths tested and discussed in that podcast.

Yeah I listened to that one. You recall the episode # or name?

 

[06 SB]

What bullet? It matters. If you are shooting a Berger use their info as a data point. If using Hornady, the Berger data is not relevant.

Pressure signs may not show until you are way over max. I look at the various recipes like you did but note the given velocity for the max loads. Stop when you reach the max load or max velocity (corrected for barrel length). That is my method for what its worth.

 

[waveslayer]

So just asking... are you looking for your max load or actually load that works in your rifle? That's two different things. Most rifles have a good node near or at max and one well below. It will depend on the velocity you are wanting to get.

Best is to do an OCW test. Tells you more then what a ladder will accomplish. OCW will account for heat and not just single shots looking for vertical dispersion. Shooter error can throw off a ladder with 1 to 2 shots!

 

[huntoregon]

So just asking... are you looking for your max load or actually load that works in your rifle? That's two different things. Most rifles have a good node near or at max and one well below. It will depend on the velocity you are wanting to get.

Best is to do an OCW test. Tells you more then what a ladder will accomplish. OCW will account for heat and not just single shots looking for vertical dispersion. Shooter error can throw off a ladder with 1 to 2 shots!

A load that works in my rifle. I only loaded what I did to check for pressure. I was trying to avoid loading a bunch of rounds only to find out they are too hot and I have to dismantle them.