7mm Rem Mag vs the new age

[35WhelenAI]

I honestly ask this and am re-asking what I said above with an addition in parentheses:

The 7mm PRC is the first time I've seen having to rely on barrel break in and seasoning in order to reach published velocities. A 30-06 ought to be over 2800 fps with a 180 gr factory anything after a hundred rounds or so, but it isn't (2650-2700 fps is pretty common achieved speed with factory ammo and 24" bbl). Is the 7 PRC different in that regard?

 

[TaperPin]

Ron Spoomer had a chat with the guys at Hornady about velocity differences between early 7prc and current production ammo. Hornady sounded pretty mater of fact about their powder supplier cutting them off of the fast powder the published velocities were based on, and the new powder is simply slower and will be for the foreseeable future.

From what Ron said, it sounds like Federal still gets the faster powder.

Maybe that’s already been said I missed it.

 

[Harvey_NW]

I honestly ask this and am re-asking what I said above with an addition in parentheses:

The 7mm PRC is the first time I've seen having to rely on barrel break in and seasoning in order to reach published velocities. A 30-06 ought to be over 2800 fps with a 180 gr factory anything after a hundred rounds or so, but it isn't (2650-2700 fps is pretty common achieved speed with factory ammo and 24" bbl). Is the 7 PRC different in that regard?

I thought it was pretty well known that a lot of box velocities are inflated, so you usually can't put much stock into numbers until your barrel speeds up and stabilizes. I understand there was an ammo and expectation issue between Hornady and consumers, but again, there are guys shooting 7 PRC with 24" barrels using Federal 175 ELD-X ammo and getting the advertised 3,000fps box velocity. I don't understand how this doesn't meet the requirement they set, or how it's even comparable to a 30-06.

 

[35WhelenAI]

It relates, IMO, because in 30 years, haven't heard as much talk about barrels speeding up to meet factory claims, or to get close than with the 7mm PRC.

 

[bmart2622]

How many guys were using chronographs 30 yrs ago compared to now? Its probably always been an issue but didnt come to light until chronos were more widely used. Its been pretty standard in my experience to not meet stated box velocity over the last 15 years. My trusted 30-06 would never hit stated velocities or publish speeds in reloading manuals, it did kill a lot of elk though

 

[35WhelenAI]

To be sure, I wasn't saying the point of reference was 30 years ago. I don't read of barrels speeding up with mainstream classic cartridges that have been around for 100 years or more whether years ago or today. I've been using a chronograph for 30 years though and don't see in my reloading notes appreciable differences with a new rifle/barrel whether in a hundred or 500+ of rounds through various rifles. It's all personal experience, those a with different experience may keep closer track than what I can tell based on my notes.

 

[MtnW]

I have not experienced velocity increases in my three main go to hunting rifles with increased round count. The rifles .300 Wea , .270 Win and .340 Wea..
In fact I have experienced zero increases or zero decreases in my .300 Wea.. My velocity in my .270 Win and .340 Wea has actually decreased by 50-75 fps due to different lots of the same powders over the last two decades. I also found this with earlier .340 Wea factory Ammo vs more current ammo. Federal Premium and Weatherby factory ammo has been most consistent and close to advertised velocity.I have owned a Oehler chronograph for a long time and now the Garmin.
I have never been a fan boy of Hornady bullets having had some failures early on. Also I think Hornady quality control varies on their various product lines. I do like the Hornady Lock-N-Load bullet comparator system.

 

[Harvey_NW]

I don't read of barrels speeding up with mainstream classic cartridges that have been around for 100 years or more whether years ago or today.

Firecracking, and increased pressure and velocity happens in every barrel ever made for smokeless powder. The only way you wouldn't notice it is if you're unnecessarily scrubbing it clean with an abrasive solvent every XX amount of rounds. With regular carbon and copper removal, or the easiest method of not cleaning at all, the velocities will increase and stabilize around the 100-250 round count. This is widely recognized by shooters, and has been documented by ballisticians like Bryan Litz/Applied Ballistics.

 

[35WhelenAI]

Appreciate the sources and verification. Looking at notes for my 35 Whelen AI built in 2002 that I have taken from shot one to over 650 documented rounds now. I have dropped back in the powder charge 1.5 gr (for same velocity) from the initial loads I developed when it was under 100 rounds.

I typically buy powder 2 pounds at a time, from the same lot. With that, I cannot rule out the change in powder lots over the course of 650 rds as the reason for dropping back 1.5 grs to keep the same velocity, with me assuming it was from a "faster" powder lot. Changing powder lots can cover a +/- 100-150 fps in anyone's book. We have all adjusted loads based on a new lot. But not much attention, until more recently, has been paid to barrels speeding up.

In any case, 2940 fps for a .358 200 gr TTSX with IMR 4064 or 3030 fps with Power Pro Varmint (25" Shilen bbl) are superb loads.

With that, I will re-cant and say that there's at least a decent chance my barrel experienced speeding up and I could be giving the change in lots too much play.

 

[Sinistram]

Hornady took a blasting because they failed to tell everyone that they were getting 150-200 fps less with the new powders they had to use but still claimed 3000 fps. If they would have been honest there wouldn't have been a big issue. With 26" barrels the speeds were around 2880 fps on average. Lots of info on YouTube confirms that. Had they developed a round that doesn't rely on RL 26 to get the speed they wanted they would have been better off. A 1 in 8 twist 7 mm RM will outperform the 7 PRC since it has more case capacity.

Exactly this. Well said!