Wildcat Cartridges

There has been a lot of noise and confusion around the 6.5 Grendel® and the similar cartridges that have sprung up around it. Two have surfaced that bear a closer look. The 6.5 BPC has become “the” bolt action chambering that can safely fire Grendel ammo. The differences in the chamber dimensions are minor; the 6.5 BPC was developed by Jim Borden and Dr. Louis Palmisano, the latter of PPC fame. The newest entry into this race is the 264 LBC-AR™ from Les Bear Custom, as the name implies this

Headstamped brass by Hornady

chambering is optimized for the AR platform. The biggest difference between these variations is that fact that the latter two are open use, in other words, anyone can chamber for them, like any factory cartridge.

Some sources call the BPC and the LBC cartridges “improved”. When you compare the drawings this is improved label is pretty hard to understand. There is little difference aside from the tolerances for case expansion, and the throat design. They do have a 30 degree shoulder verses a 28 degree shoulder on the Grendel, however, this will not provide any noticeable change in ballistics as the volume of the case is virtually unchanged. In fact, 2 degrees is barely outside the tolerance limits that most tool makers offer.

Ammo for the 264 LBC-AR

Black Hills Ammunition has new loads being built exclusively for Les Baer Custom at his request and with his assistance in load development. The .264 LBC-AR is loaded with a 123-grain Hornady A-Max bullet is available exclusively from Les Baer Custom. It’s designed for use in Les Baer Custom rifles as well as rifles of other manufacturers, and will also perform in rifles chambered for the 6.5 Grendel cartridge. The brass is produced by Hornady and head stamped .264 LBC-AR. Naturally this brass could be sized in a 6.5 BPC die and used for rifles so chambered.

Clymer Reamers announced at the 2010 Shot Show in Las Vegas that they would soon be shipping piloted chamber reamers that match up to the “West Coast” pattern.  They are also moving to the screw attachment for these reamers as apposed to the old spring clip style retainers.

Todd Wilms, Owner of Clymer is clearly proud of his products and rightfully so.  When he purchased the company almost five years he set about the work of moving the company to a new facility, rebuilding and replacing machines and in short looking at the entire operation with an eye toward improving the products they make.

Patrick Ryan at Redding told me that one to items that Redding is making a standard stock item for 2010 is dies for the “260 Imp. 40”.  That translates as the 260 Ackley Improved to you and me.

We talked about popular wildcats they had made dies for recently.  The 6mm SPC was one that had seen some strong interest.  I am a firm believer that the pendulum has begun to swing away from huge cartridges with super case capacity.  Economics may enter into the change but more likely it is shooters learning that they don’t like recoil, and smaller cases are the easiest route away from recoil.

Ballistics from the 6mm SPC will fall right between the 6mm BR and the 6mm PPC so it is in a good family.  Accuracy should be awesome in a well built gun.  It’s not as short and fat as it’s cousins but that should not hinder result too much.  Like many things in life, its more about having faith than anything else.

Headspace for Ackley Improved cases should be a no-brainer. Ackley set up probably the simplest headspace system for a line of wildcats that any gunsmith ever devised.

Rimless or Rebated Improved Chambers…

Ackley Improved cartridges in this category seem to receive the most abuse at the hands of hobbyists and local gunsmiths who do not understand the proper headspace of Ackley Improved designs. P.O. Ackley did establish specific headspace dimensions for all his Improved case designs. The process is extremely simple and for this reason alone folks seem to think they need to make it more complex. Keep it simple.

The most important innovation that Ackley brought to the “improved” concept was with regard to bottleneck rimless cases. He chose the simplest of mechanical solutions to insuring that his improved cases would safely fire factory loads. He shortened the chamber by .004” (4/1000 of an inch). Because the factory case is then a crush fit between the bolt face and the junction of the neck and shoulder, proper headspace is insured. This is why Ackley prescribes setting the barrel back on such cases. You will note that if you follow these simple guidelines there is no confusion about the headspace measurements for “Ackley Improved” designs in rimless or rebated cases.

Some confusion seems to arise out of this headspace issue. Folks get confuse between the set up for a rimless bottleneck case and a rimmed or belted case when discussing ‘Improved” chamberings. Rimless and rebated cases are the case designs which always require a barrel set back to be properly headspaced. As memtioned in the paragraph above headspace on an Ackley Improved rimless or rebated designs is .004” shorter than standard. The shorter headspace means you have no choice but to set the barrel back if you want correct headspace.

There are special Ackley, go-gauges, they have the same shoulder angle as the parent case but they are shorter. This ingenious method effectively controls headspace with factory cartridges in the new larger, ‘Improved’ chamber. The factory cartridge or parent go-gauge becomes the no-go for the new chamber. This system works because the parent go-gauge is .004” longer than the Ackley gauge, exactly the same as the difference between the parent go-gauge and no-go gauge. Example: 30-06 Ackley Improved go-gauge is used with the standard 30-06 go-gauge as the no-go gauge.

The only place the factory case will touch in the new chamber that matters is the bolt face and the junction of the neck and shoulder on the case. It will actually slightly crush the case shoulder when you close the bolt on the factory round. If you eject such a case unfired you will normally see a shinny area on the shoulder where the case was crushed just a little. This crush fit maintains proper headspace during the fire-forming process.

Chambering an Improved Rimmed Case…

Rimmed cases are the easiest of all Improved or wildcat cases to chamber for. The rim is the headspace control feature on these cases. The rim is trapped between the bolt face and the rim cut in the back of the barrel. So if the rim is headspaced correctly you can have almost any shape of case fire-formed beyond the rim, so long as it will extract. The action of the firearm is not sentient; it does not care what the chamber looks like. So rimmed cases utilize standard headspace gauges for the caliber, no Ackley gauges needed.

There is no need to set the barrel back on a rimmed cartridge when you convert it to an Improved design! Why? Because the rim controls headspace, the fact that the shoulder will be moved forward and the neck shortened has exactly NO effect on headspace. Reamers for improved cases normally have the rim cutter integral to their design. Simply paint the rim cut in the barrel with machinists blue, when the rim cutter gets close to this material just watch close, as soon as it scratches the material, stop reaming. Utilizing this method there is no danger of changing the headspace of the gun in the process of ‘Improving’ the chamber.

Rimmed cases headspace on the rim of the case only, ‘Improved’ cases of the rimmed variety often incorporate a shorter neck, thus the shoulder is moved forward to increase capacity, this is combined with increased shoulder diameter. Often rimmed cases benefit the most from an ‘Improved’ design, simply because they gain a much higher percentage of case capacity.

Chambering an Improved Belted Chamber…

What was said of rimmed cases above is also true of belted cases. Belted designs headspace on the belt much the same way rimmed cases headspace on the rim. The distance between the bolt face and the belt cut in the barrel is the headspace for these cartridges. Like the rimmed designs, ‘Improved’ belted cases use the standard headspace gauges, no Ackley gauges.

While it is possible to use machinist blue as suggested with the rimmed case, you will quickly find that it is much harder to determine if the machinist blue has been scratched, there is simply much less area to view. For this reason it is a good idea to set the barrel back when doing a belted magnum improved case. If the barrel is slick with no sight holes drilled in it you can set it back .004” so that that bolt will not close on the go gauge. Then rechamber with the Improved reamer until the go gauge will allow the bolt to close normally.

I recently picked up a set of the Handloader Magazines on DVD.  The set covers 40 years of Handloader, from the first issue on up. There is a wealth of information buried in these old magazines and the DVD’s take up far less space on the shelf than 40 year of old magazines.   Aside from that you can search the entire collection from one file which is located on all the individual disks.

Say you want to know more about Rocky Gibbs…  Just put his name in the search window and all instances of his name from the first issue to the last will be listed.

By trial and error you can adjust your searches to be more accurate and return more useful information.  I should warn you though, it’s a little like when you pulled an encyclopedia out as a kid to do a report for school and find yourself reading about casting bullets in stead of reloading tools, etc.

Before I picked up these DVDs I had a pretty strong collection of magazines going.  I have already eliminated my Rifle and Handloader collection.  Now somebody needs to do the same thing for American Rifleman. 

If you have not read many old gun magazines you would probably be surprised to find that much of the material was more technical in nature in years past.  Some data may be outdated by new technology but its valuable from the stand point of reminding us how much can be accomplished with very few tools.  Frankly, many magazines today would do well to return to more technical articles, that broaden our knowledge of ballistics an the mechanics of shooting.   Either way, this collection of classic material on disk is highly entertaining for the gun buff and educational for any wildcatter.

OK, Shot Show is just a couple of weeks away now.  We will be attending the show and will look for reloading tools, bullets, dies, and of course anything that might be of interest to the wildcatter.

Watch here for updates during the Shot Show. 

Here is a link to an article that might help answer a few questions if your learning your way around wildcats and some of the nomenclature.  This article also discusses some methods and concepts that could be helpful, check it out.

FindArticles - Loading wildcat cartridges: a few simple considerations make life much easier
Guns Magazine, August, 2005, by Charles E. Petty

FDZ