I was asked this question the other evening around a fire. Later that night a thought occurred to me about how many times I have been asked this question by folks. I figure a few more of you out there would like to know as well.
You should NOT attempt to fire a 6.5 Creedmoor (CM) cartridge in a rifle chambered in 6.5 Precision Rifle Cartridge (PRC). Both cartridges share the same bore diameter, but not the same chamber dimensions. Although the 6.5 CM cartridge will fit inside the chamber of a 6.5 PRC, it would be unsafe and unwise to attempt to fire.
Now that you have the answer lets take a quick look at what makes them different and see what commonalities they share. And specifically why you wouldn’t want to try to shoot the CM cartridge in a PRC Rifle.
6.5 Creedmoor and 6.5 Precision Rifle Cartridge differences
Although there are similarities they have one major difference that puts them into completely different categories (or families if you will) of cartridges. And that is in the case itself or better yet their parent case. Or more specifically their case head measurement.
Most new cartridges these days are a spinoff of an older (parent) proprietary cartridge. Reason being, the economics and the manufacturing process. Manufacturers aren’t so keen on investing a lot of time and funds into new tooling, dies, components and floor space for their machinery on a new whizbang that may be a quick fad. This goes for gun and ammunition manufacturers. So when a company designs a new cartridge they typically draw it from an existing cartridge in in production. This ensures that most of the components needed for the ammunition and firearms of a new cartridge are already being manufactured. Making it cheaper to bring the new cartridge to market.
In the case of our two cases. The 6.5 Precision Rifle Cartridge was drawn from the 375 Holland and Holland (H&H) family. And the 6.5 Creedmoor’s lineage traces way back to the 30’06 Springfield. In both cases not much other than the case head measures or resembles their parent cases. Which is what we are going to discuss next.
The CM’s case head measure .473 inches nominally. While the PRC case head measures .532 inches nominally. The “nominally” refers to the small plus/minus variance that is allowed due to manufacturing tolerances. So what does this have to do with your question? When chambered the cartridge extractor holds the case against the bolt face. Due to the smaller case head. The 6.5 CM case wouldn’t be held against the bolt face when chambered. This would allow the cartridge to move freely around in the chamber. Especially since the 6.5 PRC chamber us substantially larger than a 6.5 CM chamber. Resulting in the firing pin possibly not even connecting with the primer when the trigger is pulled.
If you look closely at the case diagrams above from Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI) you will notice that other than the bullet/projectile diameter itself the CM case is smaller overall than that of the PRC case. If the CM round were to be fired in the PRC chamber the case would not be properly supported by the larger PRC chamber. This could lead to failure of the case’s integrity. When this happens more pressure is put directly on the barrel’s chamber and the bolt. At the very least this could damage your rifle’s chamber. Moving further along the line of catastrophe, failure of the rifle’s integrity is also possible. This could lead to severe injury or death of the person firing the rifle.
What these cartridges share
I know what you’re thinking. If these cartridges are so different why would I ever be asked if they can be interchangeable? Some cartridges are interchangeable, examples are in this list by SAAMI. In our case lets look at some reasons why I’ve been asked in particular. Starting with the obvious, the name. I won’t go to deep here because a large book could be written on cartridge names. The short version is. When a new proprietary cartridge is submitted to SAAMI the name has to be different enough from any other cartridge so as to not get the consumer confused. Leading to someone purchasing and attempting to fire the wrong ammunition in the wrong gun.
In our case they both share 6.5. The 6.5 in both names refer to the metric diameter of the bore often known as the caliber. Most manufacturers will put a caliber reference into the name of the cartridge for marketing and/or to distinguish for safety. For our case study we can throw 6.5×47 Lapua, 6.5×284 Norma, 6.5 Grendal and lets not forget 6.5×55 Swede (introduced in the 1890s) to name a few.
Another similarity is that both cartridges were brought to market by Hornady. And both are marketed heavily in the long range realm which leads some to ponder if they share a relationship akin to the 38 Special and .357 Magnum interchangebility. It is possible that Hornady was trying to cash in on the popularity of the 6.5 Creedmoor when they added the 6.5 PRC. Along with the addition of the 6mm Creedmoor and the 6mm ARC as well. Or that they were just filling niche sectors of the market.
One of the last similarities they share and probably the least of the reasons leading to the 6.5 CM in a 6.5 PRC question, is their shoulder angle and overall appearance. Both share the same 30 degree case shoulder angle and similar neck length. Making their case look similar, but by no means compatible. This has nothing to do with one shooting through the other’s rifle. Simply the 30 degree shoulder is very popular today for reloading purposes, powder efficiency and feeding reliability.
Final Thoughts
Why would Hornady make a new 6.5 cartridge when they already have one? Well at the end of the day money, competition and R&D would have to be some of the reasons. The 6.5 has always had a very strong following outside the US and a very small but dedicated following inside the US. But arguably it wasn’t a mainstream cartridge until the 6.5 CM ripped through the countryside creating a new opportunity. Naturally other companies wanted in on the action and sent their engineers to the drawing table. The 6.5 Creedmoor is a great cartridge but it does have a few shortcomings. One area was the ability to deliver downrange kinetic energy and bullet velocities that a magnum round provides. Now that “6.5” is a popular designation in the us. And is common on gun and ammo shelves everywhere it gave manufactures the ability to remake and remarket older less popular rounds. Rounds like the .264 Winchester Magnum (also a 6.5mm Caliber) introduced in the ’50s and push them out to the public who at the moment cant get enough of any “6.5”
So now that you know the similarities, differences and a little trivial knowledge! Lets end by circling back to the beginning……… A 6.5 Creedmoor will not safely shoot in a 6.5 PRC.