Fire form 6 Dasher problems

[dra1911]

First 10 rds were formed using 0.025" jam. Length was 1.541 +/- 0.001" Next 40 rds I used a false shoulder and 0.025"jam. Length was from 1.529" to 1.532". Majority were 1.531". Used 30gr varget, CCI450, 105 AMAX, 0.004" neck tension and blue box lapua brass. Only changes were the barrel was sent to MMI Trutec. Only things I can think of are my chamber was not completely dry and there was imperial sizing wax left on the cases. Any help appreciated

 

[DMC]

PM Sent

 

[dra1911]

Thanks. PM sent with a few questions.

 

[dra1911]

Could I try to refire form the short cases? Is it OK to rinse my resized brass in mineral spirits to remove any sizing wax?

 

[shooter63]

dry chamber & brass try 205 m primer & 30.5 gr. varget with the load& shoot method 25th. jam/ plenty of nk. tension at least 4th i use 265 nk. bushing /after initial fireforming/ nk. size& load your accuracy load this is with a 272 no turn nk.usually my cases length is 1.548 to 1.550 after 2nd firing/ false shoulder method also works well with 205 m fed primer regards shooter63

 

[johara1]

Clean and dry the chamber and the cases with non chlorinated brake cleaner and don't let it get hot clean and dry the chamber every 5-10 rds. i can regulate the length with the load,by going up a little they should get longer. If they don't,your chamber maybe to highly polished...... jim

 

[dra1911]

Fired twenty rounds these evening. OAL was 1.540" with a couple at 1.539". This is the same as the first ten rounds using 0.025" jam before the barrel was treated by MMI Trutec. I hope I can get a few more thousandths in the next couple of firings. Thanks for all the help.

 

[johara1]

What is your chamber length?... jim

 

[dra1911]

Cut the chamber with a PTG reamer. Suppose to be 1.555" with a 1.545" trim length.

 

[johara1]

If your chamber is 1.555 you don't need to do anything when fire forming the brass can't go forward. measure the chamber length with a longer piece of brass say 1.560. the bolt should not close easy. A 6br case will work for this,but i kind of doubt if it's 1.555...... jim

 

[dra1911]

Measured several pieces of new 6BR brass. They were 1.555" Dave Kiff told me to trim the dasher brass to 1.545". PTG calls the reamer the blue box special.

 

[johara1]

What is written on the die and you are told and what it is may not be the same. If a longer case chamber it is not 1.555. If you have access to an optical comparator is the only true measurement....... jim

 

[benjamin199]

How consistent is your base to shoulder measurement when comparing jam fire forming to using a false shoulder? I think this is the more important measurement.
Could it be you are getting a better formed case using the false shoulder so it's using more of the brass and giving you a shorter length overall on the new cases?

 

[dra1911]

My OAL was the same, 1.538"-1.540", jammed or false shoulder with jam. The difference was the degreased chamber and cartridges (1.539") vs. non degreased chamber and cartridges (1.530"). I used a Sinclair bump gage and the difference between the shoulders were very close to the difference in OAL cartridges. I could cover 9 of the 10 shots at 100 Yds with a dime. I called two shots out and the fouler shot was under the dime. I have 40 rounds loaded for a ladder test, 31.1 gr to 32.6 gr Varget and 105 Amax. Waiting for the weather to clear up. Next on the to do list is to finish and test fire the 284 Win. Thanks to everyone for all the help.

 

[johara1]

Sounds like the chamber is too polished and you had it coated or something ..... i usually ruff them up a little with 120 grit paper on a mandrel to give a nice cross hatch so the case has something to get a hold of......jim

 

[Leaddog]

I shoot quite a few pieces of 1.537 brass and don't seem to have any problems. It shoots just as well as my 1.550 brass if I keep the throat clean from carbon build up. I have a .266 neck and 1.55 freebore (Mark King rifle). I trim my necks to .010 thickness. I shoot the 105 Hybrids.

Anyone experiencing accuracy problems shooting short brass? I just don't see it.

 

[tenring]

I have shot Dasher brass as short as 1.515" and saw no change in accuracy. Just don't mix them with longer brass. And, keep carbon ring out.