Irregular velocities with 7prc loads

[Tommy T]

I recently built a lightweight 7prc and started trying to work up a load. I am running into some odd velocities and wanted to see if anyone has experienced anything similar.

I am using ADG brass, h1000 powder federal gold medal match large rifle magnum primers and have tried 175 eld-x and 180 ELD-M bullets velocities are measured on a Garmin zero chrono

During my load work ups I am struggling to find any nodes at all and my velocities jump around a lot there have been 2 charge weights that gave decent which were 66.6grns and 67.5 grns after my initial testing I loaded 5 rounds of 66.6, 66.4 and 66.8 grns, the 66.6 grn group gave me an average velocity of 2815fps with and SD in the teens, 66.4 grns was an average of 2790 with a SD in the 20's and 66.8 had an average of 2754 with an SD in the 20's.

That's just an example and I've been seeing similar results across all charge weights if I load up 5 rounds at least 2 of them are 50-200fps different than the rest and it's had me pretty confused.

The other day I tried a few different primers with a load of 67.5grs and was kinda shocked. I loaded 5 rounds each with gold medal match magnums and Remington lrm primers the federals had an SD of 28 the Remington's had an SD of 9. I also loaded 2 rounds at the same charge with white river standard large rifle primers and the SD from those was 1.6, I know 2 shots is not a significant source of data but still definitely worth exploring more.

So it would seem that my rifle doesn't like the powder/primer combo I've been using and just wanted to see if anyone else has ran into something similar with this cartridge.

Just as a note so far every group I've shot with this rifle has been under 1" at 100yds but I haven't got it out to farther distances yet

I use 70.5 gns.of retumbo In my 7 PRC with 175 Berger's and federal 215 with a 22" proof and it's going 2956 with SDS at 3.5 , I would look at your neck tension , I use a mantrel 283 size and it works great on all of my 7 PRC

 

[palmtree191]

Following as I'm interested to hear what your solution is. I'm just getting into reloading for my 7 PRC.

 

[waveslayer]

We haven't started to suggest on your reloading practices... most of the time everyone blames equipment, powder, primers etc, but how are you reloading your ammo?
Have you annealing your brass after your stated 4 firings, which is a lot to go before annealing that caliber? How are you annealing.
What powder measure are you using, are the bullets seated consistently?
Too many questions on fire forming on low charges... don't waste resources. Use QL and have two loads, new Brass loads and once fired loads.

 

[Johrichal]

Thanks for all the replies! You guys are awesome.

@Rflshooter & magnummaniac - that's a long the lines of what I was thinking I've read that some people have had problems with "fast" primers in some loads due to the primer unseating the bullet before the powder is fully ignited or something like that. Id rather not run the bullet into the lands as I built this primarily as a hunting rifle and don't want to end up with one a little too long at the wrong time. I never thought of crimping but will definitely add that to my list to try, and I have not taken the bolt apart to clean it but I probably should, thanks.

@Tiny Tim - I started with a .311 neck bushing that I ordered before I had my brass found out that gave me about .003 neck tension and have since switched to a .312 so about .002 tension. Definitely not a new reloader been loading for my hunting rifles for about 20 yrs and long range guns for the last 10 or so yrs I measure charges with a Frankford arsenal intellidropper than double check them on a self "accurized" RCBS 10-10 beam scale.

@letzhunt - Lol no pet unicorns here I used to use RE 26 for my .270WSM but haven't seen that for years and even if I found some I'd be hesitant to buy it for fear that I'd find the perfect load then never be able to buy it again. I do have some N565 in the mail though and will be giving that a try when it arrives.

I loaded up 10 rounds each of the RLRMP and white river LRP last night and hopefully will get out today to try them out, I'll let you know how it goes thanks again everyone for the advice

 

[Johrichal]

@waveslayer - I'm not trying to blame anything on equipment it could very well be something I'm doing but I load for quite a few different calibers the same way I am for this one and have never had any similar problems my bullets are seated consistently I check every third one and rarely have a variance, I'm not set up to anneal yet several years ago I bought the stuff to build an annealer but haven't gotten around to putting it together yet. I don't have QL but have been meaning to look into getting it

 

[Johrichal]

And by fire forming on low charges I usually take my new brass and run a load at book starting charges to fire forn

 

[waveslayer]

Annealing will help with consistency with neck tension, correlating to consistent velocities

 

[EFouraker]

A lot of times the problem with Velocity spreads can be in the ignition system of the bolt. If the firing pin has drag it will fight you. And just because an action is a "custom action", doesn't make it immune to this. I see it all the time. There is a small percentage of rifle builders that even understand this. Most are just installing barrels.

 

[Johrichal]

@EFouraker - how do you determine that and what can you do to fix it? This is my first "custom" action it's a kelbly nanook

 

[Flea21]

I had a similar issue with my 25-6.5 PRC.. I recommend going with Vhitavuori Powder, N565 or something in that burn rate. I'd be willing to bet things will turn around for you.

 

[captrjc]

I had a similar situation with a mod 70 300wsm. After I switched to Remington 9 1/2 primers everything settled down and the rifle shot great. I started with Federal tried cci and even Winchester. I was able to get it to shoot decent with the cci but the Remington primers gave me a wide node and pretty consistent .5-.75 MOA - 1"-1.5" groups at 200 yards on a bench. It was a while ago and I can't remember the recipe specifically.

 

[RockyRandy]

I don't know but would any of his SD numbers have anything to do with a new rifle that isn't broke in yet?

 

[sakoluvr]

50 - 200 fps variance with the same load is crazy. Check the garmin

 

[belldar]

I had the same issue with my H1000 with inconsistent velocities. Switched to H4831sc and it did much better with my last 7prc