Fireforming 20 dasher

[trevort]

I hope to pick up my 20 dasher next week, BAT SV, Lilja 9 twist, McMillan hunter benchrest stock, Jewell trigger and NF scope.

I get the false shoulder idea and with a 20 cal neck that should be easy. I am getting this to shoot 55gn bergers and have 1000 on the shelf

I have 750 40 gn vmax left over from a 204 ruger I sold and was planning on using those to fireform.

Should I anneal necks first or is the factory anneal on lapua brass good enough for the first firing?

Can anyone suggest a starting load? Do I just use a mid range 20 br load (I have Varget and H4895 and am going to buy some re 15)

Should I anneal after first or second firing?

Any other warnings you would give to a newbie at fireforming?

 

[ab_bentley]

Use the appropriate loads for the 20br to fireform. No need to anneal unless it gives you a warm and fuzzy. It'll take two firings to get sharp shoulders but that shouldn't stop accuracy.

 

[Geno C]

Make sure there is enough neck clearance once you neck down. Most that I know that have these have to neck turn.

A standard 20br load will be fine, like said above.

 

[rickiesrevenge]

I dunno what your plans are for this rig. But you could load the 55's and go kill stuff while fireforming. I use a little over 29gr of varget in my 20br with 55's
Aaron

 

[Clavius-Walker]

You could also do the shotgun powder and cream of wheat fireforming, might not come out quite as good as the loaded fireform but may save on your barrel life which is short anyway in those things.

 

[trevort]

thanks for your help. I hope to get on paper whilst running in the barrel and have an accurate enough fireforming load to hunt small furries with.

I have a palma profile barrel parallel for 5 inches and finished at 28 so it can be set back to give me more life from it, then again the wife says I have too many guns and I don't have time to use them all so wearing out a barrel would be awesome

 

[SRM]

Playing with my dasher I have gotten goofy brass. I would anneal after necking and after firing.

 

[trevort]

I have 50 formed cases so far and another fifty loaded with the fireforming load. I got impatient and tried to size down with different bushings in a 6brAI fl bushing die. I killed a few.
Using 22 br form dies first did the trick. I will anneal before loading them again.

I have varget, re 15 and H4895. Anyone have any load data for the 55gn berger in the dasher or an opinion from experience on these powder choices?

Thanks in advance

 

[MrMajestic]

I would use full power loads to fire form or your blow length will come up short. Happens to my .22 Dasher and search and you'll find info for the 6mm Dasher. FWIW, 1/2 grain of Varget changes blow length .010" on mine and you don't get it back later. I use RL17 in the .22 and I would think it will give you some good velocity in the 5mm. FYI, I get 3640 fps with the 55's from my 28" 8 1/2tw 5X45AI using RL17.

 

[trevort]

I used 28,5gn of Varget and a 40gn vmax