IBS anyone?

[stagpanther]

Rifle is assembled--but I'm dead in the water; I've ordered the necessary neck bushings--in fact I ordered the same size bushings from multiple vendors all of whom said they were in stock but none of whom has packed and shipped them as of yet. The barrel I got was cut to Robinett's specs; the chamber neck being .330 and case length specified as 1.510. The design is intended to have a precise neck tension and bore engagement right from the start upon chambering. I've struggling with the mathematics of the thing--it's not quite as simple as adding up the various components because there is no 30 BR brass--you have to neck up either 6 or 7 mm brass; and of those two only 6mm BR is generally available. That's a pretty big jump and the brass is going to flow in such a way that I haven't been able to get precise consistency through the entire length of the neck to shoulder; I've ended up with external doughnuts at the neck/shoulder junction and that will stop the case from fitting the chamber. The trick (apparently from what I've read) is to get the brass sized well enough to get a first fire-forming shot. I know what you're thinking--just turn the neck, and I do have the turning equipment to do it--but I want to avoid removing brass if at all possible. I have smaller 308 bushings--but I think for this particular chambering assuming typical neck thickness of .012 to .02 the necessary bushings are going to be in the range of .327 to .329. As far as I know there is no "one pass" 30 BR sizing die, I guess because the brass is meant to be form-fitted to a particular chamber.

 

[georgehwbush]

so mr quigley you're using an experimental weapon with experimental ammunition, so lets experiment... :S


the more they over think the plumbing the easier it is to stop up the drain....

 

[stagpanther]

so mr quigley you're using an experimental weapon with experimental ammunition, so lets experiment... :S

I never said I didn't know how to use one.

 

[stagpanther]

The bugger is expanding the neck out with to 308. That additional diameter is going to have to displace the intersection of the neck and shoulder. That's the critical intersection that has to be just right or the cartridge won't chamber. On my Wilson 30 BR die when making a pass on the neck after enlarging it through a mandrel the bushing does not seem to go down far enough the neck (I've already trimmed the case length at that point)--what's happening is that there is a "flare" of the neck diameter at the shoulder junction that exceeds the chamber neck diameter of .330. From what I've read the goal is to get a functional cartridge that can fit and then be properly fire-formed. This isn't my first ride on a wildcat that needs case reworking and fire-forming; but it's been one of the most challenging so far.

 

[Shenna9220]

Ok, maybe this is a stupid question but you said above you have 6mm BR brass, so I assume you have a rifle that shoots that, can you use that in you first comp the get the process down while you perfect the 30BR?

 

[stagpanther]

Ok, maybe this is a stupid question but you said above you have 6mm BR brass, so I assume you have a rifle that shoots that, can you use that in you first comp the get the process down while you perfect the 30BR?

Very good question, actually. The 6mm BR I had was a low-quality barrel so I decided to "sacrifice" it for the 30 BR. I have other rifles which can shoot well--but the particular comp format I was looking at for this weekend is dominated by 30 BR; so I was just trying to "go with the flow." Yes I'm a whimp with excuses--but I have to budget how I spend my money and weekend travel and accomodations fees are not insignificant, even if the entry fee is.

 

[stagpanther]

Bushings for the die finally arrived today--I experimented withe various sizes from .329 down to .327; so far what I have found is with the Robinett chamber cut to exactly .330 and expanding the neck to accomodate .308 there is no way to avoid having to turn the neck to remove displaced metal from the shoulder at the base of the neck. I've already destroyed about 30 cases figuring that out! Another thing, the case length has to be reduced to 1.51 prior to the final neck sizing, I don't have the necessary neck turning attachments for my K&M neck turning rig to cut or pilot 30 cal, more stuff I have to order and wait on. The light at the end of of the tunnel appears to be once you finally succeed in getting a case properly fire-formed you can live happily ever after without worrying about these kinds of hassles--apparently the brass should last the life of the barrel!

 

[stagpanther]

Parts for the K&M neck turner came in. For once I did something smart and also ordered range of neck tension pilots--I found it was impossible to get the OD neck diameter to fit the .330 chamber and also trim using a standard .308 pilot, I had to drop down to .306.

This is the very first cartridge that I succeeding in getting to load a .308 bullet and fits the chamber. Good grief. I'm not sure I have the patience to hassle with making a bunch of these.

BTW--the shell holder is snugged to the handle by a small hex head screw. Do not over-tighten it or the head will snap right off. Here's the proof.

 

[stagpanther]

Let the record show, that on this day, the 26th of July, 2024--after breaking the set screw off the K&M neck turning tool, shearing the handle off of my Wilson case trimmer and destroying roughly 40 6mm BR cases--I finally succeeded in loading 4 live cartridges of the 30 BR for fire-forming and they actually fit the chamber and cycled from the magazine!!!

No, it's true, I did finally figure out the Rubic's cube that the 30 BR is for a feeble mind like mine.

And here are my 4 little darlings; 125 tipped match kings driven by a low end load of 29 grs of VVN130. The matchkings are a bit on the large side for precision shooting with the 30 BR from what I've read but I have lots of em and I'm going to be using lots of bullets to fire-form the cases.

They fit in MDT's BR magazine perfectly and cycle without any hangups.

Here is the conglomeration assembled--it may seem a bit undignified for a select match grade barrel to be fitted to an Axis action, but I didn't realize I didn't have any other short actions available, so it is what it is until I can pony up the scratch for a Zermatt Origin.

 

[stagpanther]

I did fire them, after all that trial and error, I honestly had no idea what to expect. I popped my trusty Mark 5 HD scope on, used one of the cartridges to bore-sight in and then shot the next three at the target dot. Looks promising just for a fire-forming load--now I'm motivated to carry on.

Post fire-forming cases:

I'll be selling fireformed 30 BR brass for $50 for each case.

 

[georgehwbush]

now as per my "looking into it" i'll pass until all the bugs are worked out and brass and dies are everywhere..... not holding my breath, but looks good on paper.

 

[stagpanther]

From what I can tell, the cartridge has been around for over 20 years but remains a specialty for unique competition shooting. It is a cartridge that is specifically designed--or rather you design it, to form fit with very small tolerances into your specific barrel's chamber with the bullet seated into the lands. Because of that, I don't know if it will ever catch on as a "general purpose" cartridge, like the 6 PPC. Hornady is pretty good at looking at these kinds of things and then figuring out a commercially-viable variant--who knows.

 

[stagpanther]

Freshly neck-turned case. I'll make a couple finishing passes through the bushing die just to even off the outside before loading the charge and bullet. Now that I seem to have figured out the process and the settings the whole thing beginning to end to produce ready-to-load brass from 6mm BR brass I've managed to get down to about 5 minutes per case to have a case case ready to fire form. As frustrating as the learning process was (and it's quite probable I'm still making mistakes that need to be improved upon) I learned some really interesting new things about precision loading along the way--so that made it worth it.

 

[georgehwbush]

nice

 

[stagpanther]

Thanks--almost gave up on this one--now I'm excited about what might be possible.

 

[stagpanther]

Fire-formed a few more cases today. Just out of curiosity I brought the labradar along just to see where I was--shot these two groups at 165 yards (lost access to the longer lanes again). The numbers were not great, I was averaging around 2,650 fps and the ES was around 25 to 30 fps and the SD was around 12 fps for these two 5 shot groups. Sweet spot velocity for this cartridge is between 2900 and 3100 fps from what I've read, but I wasn't expecting much since I was shooting soft charges around 29 grs. Nonetheless, the groups were pretty good--without the flier in each group would have been even better. Once I get 50 cases formed up I will start serious load development.

 

[stagpanther]

The last of the Petersen brass to be fire-formed into 30 BR. My goal for now is to do 50 cases each of Petersen and Lapua to start load development.

My goal of this somewhat tedious work is to rework the neck to hold the bigger bullet and set the neck tension and diameter at the same time. The brass flows when being resized and forms a doughnut--more like a tire IMO--at the base of the neck and the brass won't chamber unless that doughnut is cut away and then fire-formed into a smooth transition from the shoulder to the neck. That area is the bright ring in the picture above.

Here are the first 15 cases of Lapua brass I'm starting work on:

The interesting thing that I encountered was the Lapua brass is somewhat different from the Petersen brass; it seems a little harder/denser and has different characteristics upon expansion and resizing than the Petersen brass--the technique I used with the Petersen brass did not work with the Lapua brass and the lapua needed an extra pass through the 308 mendrel. The Lapua was also noticeably harder to trim; and I found I had to carefully clean and lubricate the carbide blade and pilot after each case neck trimming.

From what I've read--groups in the .4 to .5 MOA are not acceptable for this cartridge for competitive shooting and really should consistently produce groups in the .2 to .3 MOA range. Zero one hole groups are supposedly fairly common with the 30 BR (!).

 

[georgehwbush]

so are you getting 3k ft/s out of your loads yet?

if so would you care to mention the powder and charge weight?

 

[stagpanther]

so are you getting 3k ft/s out of your loads yet?

if so would you care to mention the powder and charge weight?

Not even close--but I'm not trying to--all I'm trying to do for right now is form up the brass for when I get into the serious load development. Forming the brass is a major undertaking (at least for me, what I've read makes it sound like an easy as pie simple neck up); I found it's pretty tricky getting the right dimensions so that you get the perfect fit and neck tension for the chamber dimensions of your particular barrel. I have 35 more 6BR lapua cases to do and then I'll be ready to go.

As for loads, that's pretty simple--assuming you're lucky enough to find custom bullets; the sweet spot weight range from what I've read is between 110+ and 120- grs (with a specific ogive angle and meplat) and the powders of choice are H4198 and VV N130. I have used both powders in the fire-forming process, haven't noticed much difference between them except that the N 130 seems to foul the bore faster. My first loads will probably be Berger 115 gr bullets since that's all I could find for now. Powder charge weights for both seem to lie in the 30 to 34 gr weight range. From what I've read, once you find the sweet spot load for your barrel, you can "set it and forget it" and not have to fiddle with tuning for different ranges. Two good resources are here and here.

 

[stagpanther]

At long last--100 fire-formed 30 BR cases ready for load development. It will be a few days before my first "serious" 30 BR loads since a 300 wby mag rifle needs my attention first.