Problem while Fire-Forming for 6mmBR-A

[Alexander-M]

My new 6mmBR-A rifle is coming along well. It has a Panda F-Class action; Shurley Brothers LowRider XL stock; Brux 30” (finished) 4-groove, SS, 1:7.83 twist, straight 1.25” barrel; Jewel BR trigger; and is topped off with a NF Comp scope. The chamber was cut with a Wheeler-6BRA-#1 reamer from JGS.

I started with 200 Lapua 6mmBR brass cases to fire-form, plus 200 of the same, which I sent to DJ’s brass service to be hydro formed. So far I have been using Varget, CCI450 primers, and Berger 105-gr Hybrid bullets. I also have H4895 and 108-gr BT Target bullets yet to try.

Both the Hyd-Frm and Fir-Frm rounds have been impressive. At 100-y, the 5-round groups measure from 0.141” to 0.197” with the MagnetoSpeed attached. At 600-y the 5-round groups have had vertical of 0.23M, 0.28M and 0.31M, and the horizontal has been as or more impressive.

Problem:
Nine of the Fir-Frm rounds did not fire (DNF). I attempted firing two or three times each, but they did not go off. Not all happened the same day, and the temperature was between 13°F and 29°F when this occurred; I have no clue whether this has a bearing.

I pulled the bullets from the DNF rounds and re-seated them longer for more of a jam (0.016”), and five went off, but still have four that DNF. I took these four rounds apart and switched to Federal GM205M primers for these four, plus for six new rounds, and all 10 rounds fired, but two were pierced. These two pierced primers caused the bolt to open very hard in each case, which was caused by pieces of primer lodged inside the bolt, as I found later on at home.

Next step was to change the trigger hanger with a 0.0300 hanger to provide a longer firing pin travel. With this 0.0300 hanger and the CCI450, 10 out of 10 rounds fired the first time, but one out of five DNF last time. Remember, all of the Hyd-Frm rounds have gone off just fine; it has been just some of the Fir-Frm that DNF.

I have a match coming up (maybe) and had planned to fire-form then. I am not too concerned about having several of the DNF rounds, as I can take extras, but what can I do with these DNF rounds? I can take them apart and reuse the bullets and powder, which worked fine when I tried the GM201M primers, but I really do not want to use these Federal primers again.

Any suggestions are welcome!

Thank you for reading this.

Alex

 

[Kyle Schultz]

Do you feel some resistance when you close a stripped bolt on a 6BR case? If not, I'm thinking there is a headspace problem. Perhaps the chamber was cut a little deep. The Ackley cases headspace on the neck-shoulder junction. If you've neck turned the 6BR brass and inadvertently cut too deep into the shoulder, that may be the cause of the excessive headspace. I'm sure some of the 'smiths will offer their thoughts.

 

[Alexander-M]

Kyle,

No, no resistance. [< This statement was incorrect, as I later found out after double-checking the bolt closure] But keep in mind that the BR cases will be loose in the BRA cut chamber because of the 30° vs 40° angle shoulders. While I have been jumping the BRA rounds (need to try this more), I am jamming the BR rounds to help eliminate the slack.

As I said, no problems at all with the already formed cases.

Thx!

Alex

 

[Falfan2017]

Strange I have a similar chamber and when I fireform before sizing I do feel resistance like the shoulder is pushing against the chamber. Do you have a headspace gauge?

 

[swd]

Kyle,

No, no resistance. But keep in mind that the BR cases will be loose in the BRA cut chamber because of the 30° vs 40° angle shoulders. While I have been jumping the BRA rounds (need to try this more), I am jamming the BR rounds to help eliminate the slack.

As I said, no problems at all with the already formed cases.

Thx!

Alex

That's why it's best to chamber them .002"-"003" short on a case for a slight crush. It helps eliminate that problem.

 

[Kyle Schultz]

Alex:

Read this thread... http://forum.accurateshooter.com/threads/6brdx-vs-6brai.3938261/#post-37093978

 

[Alexander-M]

Kyle, et al -

(I will read that thread next.)

In the meantime, I went back and checked the stripped bolt closing effort, and it is different than I said earlier:
The stripped bolt closes by itself completely on its own; it just falls shut.
However, and which I did not remember correctly -
With a BR round with the neck already turned, the bolt requires just a slight bit of effort start closing, and then less effort to completely close, but nothing like the bolt by itself.
With a Hyd-Frm BRA round with the neck already turned, the bolt requires just a tad more effort than the BR, but not a lot either.

And now to read that thread - -

EDITED:
OK, I just read the thread. (It appeared long - 4 pages - but many of the posts had to do with the name and acronyms and not with the real subject.)

I understand what is discussed, but cannot find this 0.004 dimension mentioned here: "- 0.004" from 6BR GO gauge is what was on the reamer print from JGS for the one I bought... haven't had a chance to fire a round yet, so how well that actually works IDK " on the Wheeler-6BRA #1 reamer print from JGS.

Be it as it may, what is the best option I have now for fire-forming?

Alex

 

[Sheldon N]

But keep in mind that the BR cases will be loose in the BRA cut chamber because of the 30° vs 40° angle shoulders.

My understanding was that the 6BRA should be chambered 0.004 short of a 6BR go gauge so that it provided a slight crush fit on virgin 6BR brass. My gunsmith did mine at around 0.003 short of a Go Gauge and 90% of the cases had light to moderate resistance on bolt close, with only a few dropping free. I also did a solid bullet jam just to make sure that the cases were solidly headspaced against the bolt face.

Agree with the switch to softer Federal primers for fire-forming. Less likely to DNF or push the case forward like a 450 primer.

 

[Sheldon N]

Also, what is your powder charge weight for fire forming? Perhaps it's too hot if you're blowing primers. I fireformed at 29.8 Varget, about 1.5 grains below my final charge weight for match loads with Varget.

 

[Kyle Schultz]

Alex:

I don't think the "6BR go gauge less 0.004" is a formal reamer spec; thus it probably wouldn't appear on the reamer print. It doesn't appear on the JGS print I have. Rather, I think that is a practice gunsmiths follow when dealing with Ackley chambers. Given that you are having failure to fire issues, I would still be very suspicious that your chamber is a tad too long.

You'll have to discuss this with your gunsmith. Good luck!

 

[Alexander-M]

Also, what is your powder charge weight for fire forming? Perhaps it's too hot if you're blowing primers. I fireformed at 29.8 Varget, about 1.5 grains below my final charge weight for match loads with Varget.

I am using 30.00 gr of Varget for fire-forming. I started with 28.00, and increased to 30.00 in 0.5 increments, and stopped at 30.00 where it appeared to be most accurate. I had no desire to go higher for fire-forming. The DNF occurred at lower than 30.00 as well. I did not try the GM205M with less than 30.00, but I am hesitant to use these primers again for fear of piercing while fire-forming. I suspect they will be fine once the cases have been formed, and will eventually try them.

Thx!
Alex

 

[Alexander-M]

Alex:

I don't think the "6BR go gauge less 0.004" is a formal reamer spec; thus it probably wouldn't appear on the reamer print. It doesn't appear on the JGS print I have. Rather, I think that is a practice gunsmiths follow when dealing with Ackley chambers. Given that you are having failure to fire issues, I would still be very suspicious that your chamber is a tad too long.

You'll have to discuss this with your gunsmith. Good luck!

That will be the next step (talking with my gunsmith*), but I am sort of stuck now with the match I would like to shoot Saturday. I could use the Hyd-Frm cases, which have been flawless so far, but my objective was to fire-form during a match.

Thx

Alex
* I have discussed this issue with him, hence the GM205M, and the the 0.0300 hanger, and also tried the bolt from my 284W - all of which seemed to help and appeared to have solved the problem, but then yesterday I had another DNF!

 

[mikeeg02]

Alex:

I don't think the "6BR go gauge less 0.004" is a formal reamer spec; thus it probably wouldn't appear on the reamer print. It doesn't appear on the JGS print I have. Rather, I think that is a practice gunsmiths follow when dealing with Ackley chambers. Given that you are having failure to fire issues, I would still be very suspicious that your chamber is a tad too long.

Actually, its quite common, at least with JGS. Saves you from having to buy a separate go gauge when headspacing a barrel to a wildcat chamber. Heres the bottom of mine. If you pay more for a custom go gauge, then it says "Uses a custom headspace gauge with the same name". As my other reamer I ordered that way.







If you had failed to fires, and your using 450 primers, you likely have too much headspace between your cases and chamber. Seating bullets long helps. But if you want to make sure they go off, use 205s or 400s and tune your load to them. I've had that happen, and so has @Nature Boy if I remember right.

Seating your bullets long may not put them where they need to be accurate. And is dependent on bullet seating force to ensure firing. Changing your tune to work with 205s or 400s will work and allow you to still shoot accurately.

30 grains of varget and 205s shouldnt be a problem. That worked for me, but it wasnt as accurate of a forming load with virgin cases as 450s and 29.6gr h4895, tune the seating depth.

EDIT: Somethings were put out of order.

 

[DJSBRS]

I make my 6 BRA Hydro -formed brass .003 short of a 6 BR PTG Go gauge. Then I know it should fit and fire properly as long as the gunsmith stays within the proper go vs no go variance of no more than .004. Some of the issue may be that within the box of new brass, the heads space of those could vary as much as .004 thousand. Believe me, I have measured thousands of Lapua brass over the years. The neck thickness varies as well.

DJ

DJ's Brass Service
205-461-4680

 

[rardoin]

I had similar issues forming 6.5 x55 SM to BJ-AI using RWS brass. I would get perhaps 3/20 to fire..grrrrr. I tried seating the bullets long into definite jam and still not much more success. I switched to Lapua brass and only about 1/20 FTF's. The RWS brass would not crush on bolt closure but the Lapua would...and that made all the difference. I am unsure why jamming the bullets would not work on the RWS...I don't recall using very light neck tension but perhaps that contributed to the issue in the 'short' brass. I would also consider dropping the charge and going with the Federal 205 primers. You may find a very adequate load at a little less velocity than you would normally run but good enough for local matches. FF loads in the above mentioned case have cleaned targets at 600yds.

 

[Kyle Schultz]

Alex:

Others may disagree but I still think your fundamental issue is a wonky chamber and that's what you need to get fixed. All these tricks and work arounds may let you a FF a case but what happens after that? Are you going to be limited to a soft-cup primer like the 205? Does changing the trigger hanger cause other issues like excessive cock on close? Hope you get this resolved. Good luck!

 

[mikeeg02]

Once its fire formed, what does it matter? The only time it would is if you had several barrels and they all headspace differently, and you want to use the same die without adjustment.

After they are formed to the chamber, size the case properly and there wont be an issue.

 

[rardoin]

Alex:

Others may disagree but I still think your fundamental issue is a wonky chamber and that's what you need to get fixed. All these tricks and work arounds may let you a FF a case but what happens after that? Are you going to be limited to a soft-cup primer like the 205? Does changing the trigger hanger cause other issues like excessive cock on close? Hope you get this resolved. Good luck!

I will respectfully disagree. Once you get the brass fireformed it will shoot fine with any primer. Some new brass 'crush fits' in an Ackley chamber better than others. Once formed all is well.

OOPS...did not read Mike's post...we are saying the same thing.

 

[Alex Wheeler]

Heres what I do.
I chamber them .004" short on a 6BR go gauge. Depending on the lot of brass, usually you will need to bump the new case a little to get a perfect fit, sometimes they are ok out of the box. You should be looking for a one finger close. You should not have to force it. Keep the lugs greased. Either way I highly recommend NOT using cci 450s or br4s for fireforming. You dont have a solid shoulder yet and those primers have hard cups, anything to absorb energy can cause issues. When I hydro formed dasher brass I did it long so I could bump it to fit the chamber, same idea with the BRA. Heres a little work around, run the 6 br cases through the tightest br die you can find, but do NOT bump the shoulder. This will make them longer.

 

[Sheldon N]

Heres a little work around, run the 6 br cases through the tightest br die you can find, but do NOT bump the shoulder. This will make them longer.

That's a great suggestion.

I've also used a standard Hornady 308 FL die on Dasher brass to get adequate base sizing, before I had a Harrells D4 Dasher die. Squeezed the case quite effectively and gave me headspace that was about 0.004 longer than when I started.