A little lesson learn't

[Marky610]

Were all been told not to work up fairly hot loads in winter and expect them to work in summer (well I know it's only spring but quite warm yesterday here).

 

Well I'd like to add 'especially with small fast calibers'

 

 

I worked up a load for my 20 Tac (24.3gr RL10x 40gr v-max Rem 6 1/2 primmer) it shoots really well, slight bit of cratering on the primmer, no worries.

 

Been knocking over foxes all winter with it fitted with a N750 nv scope. My mate has a look through the N750 and decides he wants to buy it so I sold it to him and the rifle sat unscoped in the cabinet for a few weeks. Anyway bought a Sightron S-Tac last week for it (awesome scope!) fitted it and went to zero it up yesterday. Had a few shot's got it nearly there when on the next shot I ended up with the plastic bolt shroud bouncing off my face (forgot to say, Tikka M590)

 

After the initial 'what the hell?' had a look at the case and theres a hole in the primmer!

 

 

So what to do? Lessen the load? But I want speed speed and more speed or find a harder primmer? Might be a fault with the firing pin?

 

 

Over to you guy's

[Swamp Donkey]

The smaller the case, the larger the pressure change. I'd rework your load

 

Pete

[tackb]

it's your face so you can do what you like but i'd back the load off personally ?

[pork chop]

i,d back off change to a 7 1/2 primmer and work back up.did it knock your roll up out

[silpig]

That's really odd, Mark! My own 20 Tac has done a very similar thing (and is of course cut from the same reamer)!I worked up a load last year, about this time. I was getting a bit of flattening/catering, but not a lot! Anyway, I've not used it for a few months as I've just moved house. When I did come to use it recently, I noticed that the primers were really flattened and cratered! However, this was at night when it was probably no warmer than when I initially worked up the load.I've not shot any paper so can't comment on any differences in group size, though, I would expect they have opened up quite a bit as the load seems to have changed quite a bit. Out of interest, do you know what speeds your load was initially producing? Luckily I only have a couple of rounds left so instead of just running another batch I will work up another (more moderate) load. I am using N133 by the way.

Adrian.

[c18rch]

I had a bad batch of CCI primers a while back. Every so often, I would say 3 or 4 out of 100 would pierce. This was with the same load that I have used for 8 years or more and never had any problems with previously. Changes to a new batch of primers, still CCI, problem solved.

 

Worth a try if you haven't had problems with the load previously.

[AnthonyR]

I don't have Quickload in front of me at the mo but I am pretty sure you are over the top with that load, max with 39gr bullets is 23.8gr IIRC, I know many do run theirs hotter but if your load is hot now at 12-15C it's only going to get worse....

 

Todd Kindler may well be a small caliber genius but his loads are seriously OTT, I couldn't get anywhere even remotely close to them with my 20Tac

[gbal]

Hmmm...i think backing off makes the most sense....would you even notice the "performance drop" in any case?For the 204 Ruger,dropping from 4225 to 4050,both commercial,safe,loads with 32g bullets,same BC ,means the drop/drift at 300y with 200y zero is only a half inch more-- -4.1/10.1 and -4.6/10.6...,click,click and you are done.

Whatever velocities you think you are running,this is the reality-there is not much in it,where it matters.Might even be more accurate,but should be safer,and kinder to barrels.

Gbal

[Finman]

I've had my M590 bolt shroud come off broken as well, and it was using an electronic scale that would not calibrate properly and threw odd loads (didn't find out till I had this problem). In my case, same thing happened: primer pierced. I would check the load again and lower it a few tenths of a grain. I was thankful that I was able to replace the shroud too....

 

best wishes

 

Finman

[Foxshooter]

I don't know, sometimes you worry me Mark. I'd stick with torches, NV and all that electrickery stuff

 

Mark

[Marky610]

Checking my notes from when I worked up the load I got pressure signs at 24.8 gr and best group at 24.2 gr so went either side of the 24.2 as I went up in .2 steps and 24.3 shot best.

 

I'll have to rework the load. New shroud ordered from Lumley Arms/ Turvey Stalking, call them what you will, oh and a nice little custom carbon fiber bolt handle whilst I was at it ;-)

[Chickenthief]

Carbon build up in the throat area will also spike pressure.

 

The Rem 6½ is a "thin" primer and switching to a 7½ will make a difference.

 

[Andrew]

It's always been my practice to live with a slight flattening of primers, but cratering of any degree I consider a serious warning sign and back away from the charge thatr causes it. In winter I would have considered it a red flag, but that's me.~Andrew

[oaken]

The Rem 6½ is a "thin" primer and switching to a 7½ will make a difference.

 

Spot on. The 61/2 is for hornet and handgun only, don't let unscrupulous dealers tell you they should be OK in anything else!

71/2 for anything generating more pressure than the hornet.

If you have a slightly enlarged firing pin hole from wear or your firing pin extends eversoslightly too far there will be trouble ahead with 61/2s.

Rup

[Raifuru]

In QL 24.3 grains of 10x for a 40 is hot. However, in my Sako 75 with I can happily shoot 24.6 10x with a 40 and QL states that as way in the red. I had a 17 Rem built on a 595 and had more than a few problems with max loads where the extractor and clip that held it in would part company from the bolt. I have found that I can load the 20 way in excess of what QL states, but that was a while ago and I don't do that these days. Again not recommended to follow, but if you use Tod Kindlers loads in QL they are all considerably over hot.

[fizzbangwhallop]

Just another angle to consider in conjunction with powder weights and primers...........

 

I loaded the first batch of new Lapua brass for my .20Prac and was getting signs of pressure on my primers (CCI400's, Rem 7.5's) using fairly mild loads of N133.

 

Went back down to see Neil McK fearing the bolt would need work and we worked out that the shoulders had been bumped slightly too much allowing the case to move back on firing an imprinting the firing pin hole on the primer.

 

It turned out that the Lee shellholder I'd been using had a lower than the standard accepted deck height of whatever it is...... apparently Lee have a bit of a reputation for this. Switched to an RCBS shellholder for a new box of Lapua and problem solved.

 

 

Cheers

 

Fizz