reducing extreme spread?

[craigyboy]

Just looking for some pointers from the more experienced loaders, I am having a few problems with extreme spread in my loads, accuracy is definatley there and at 100 she is shooting in the mid 1's but the extreme spread is going to show up badly at long range. Yesterday I got a few shocks on the chrony with extreme spreads of over 100fps happening a few times . I dont really know where it is coming from, brass is all neck turned and necks are extremely consistent well under 1 thou, I have tried different primers no luck either, primers are all seated consistenly with remi 7 1/2 primers being 3 tho below and cci 400 primers being .0015 below, I went through a whole batch with the calipers and they were all good, I use an arbor press and hand dies and can really feel neck tension when seating bullets it again feels quite consistant. The only thing I can point the finger at is my rcbs 505 scales they do seem a bit funny at times for example sometimes the charge is a bit heavy so I take out a bit of powder and when the pan settles again it reads even heavier than before but I still dont know if these slight variances would make enough of a variation for 100 fps. Any help is much appreciated as i have a range day coming up on the 12th dec and really want to play around at 600m but its pointless with extreme spread like this. In previous loading for other cartridges extreme spread has been a more resonable 30-40 fps (still too high for my liking but certainly acceptable). I am very careful about my loading and always do my best to make the best ammo possible but this one has me stumped. If its any help I am using laupa brass, h322 powder.

[Vermincinerator]

Craigy,

Is this in your 20Tac?

 

Ian.

[Guest rogern]

Just looking for some pointers from the more experienced loaders, I am having a few problems with extreme spread in my loads, accuracy is definatley there and at 100 she is shooting in the mid 1's but the extreme spread is going to show up badly at long range. Yesterday I got a few shocks on the chrony with extreme spreads of over 100fps happening a few times . I dont really know where it is coming from, brass is all neck turned and necks are extremely consistent well under 1 thou, I have tried different primers no luck either, primers are all seated consistenly with remi 7 1/2 primers being 3 tho below and cci 400 primers being .0015 below, I went through a whole batch with the calipers and they were all good, I use an arbor press and hand dies and can really feel neck tension when seating bullets it again feels quite consistant. The only thing I can point the finger at is my rcbs 505 scales they do seem a bit funny at times for example sometimes the charge is a bit heavy so I take out a bit of powder and when the pan settles again it reads even heavier than before but I still dont know if these slight variances would make enough of a variation for 100 fps. Any help is much appreciated as i have a range day coming up on the 12th dec and really want to play around at 600m but its pointless with extreme spread like this. In previous loading for other cartridges extreme spread has been a more resonable 30-40 fps (still too high for my liking but certainly acceptable). I am very careful about my loading and always do my best to make the best ammo possible but this one has me stumped. If its any help I am using laupa brass, h322 powder.

 

I am by no means an experienced reloader but i have been 'rolling my own' for 15 years now.

 

I assume the scales are the beam type? I had some 505 myself and got the same unreliable readings as you, about 2 years ago I dumped them and got the RCBS electronic scales, I wasnt loading for accuracy like you, I just wanted a weight of powder I could believe. To my mind a beam scale aint precise enough.

 

Regards

 

Roger

[craigyboy]

yeah Ian it is the tac20, cant understand it, its hellish accurate but velocitys are all over the place. Roger the scales are beam type, I do have electronic scales but they do that much arseing about stabilizing I get bored waiting on them.

[Ronin]

Two (well three) things Craig

 

1, what calibre are you shooting?

 

2, How is your powder charge density? If your not filling the case this can lead to large ES.

 

3, RCBS scales - they are VERY succeptible to grit, fluff and anything else getting into the needle point bearing (the v shaped wedge) that can lead to the scales sticking and giving false readings.

Try cleaning the bearing and metal bearer, throw a few charges weigh then and then re weigh them - do you get the same results?

 

Neck tension is covered - I take it you have turned all necks to the same size and are using a bushing die for re size? Its a slim possibility you have too much tension, but I doubt this.

 

If its shooting in the 1's, try it farther out and see how you go - 20 - 30 fps ES wont show up too much in a rifle thats shooting 1/2 MOA, with the accuracy youre getting, I would question if you'd notice out to 300. 600's a different game however.

 

Finally, how many firings have the cases had - are they difficult to chamber?, if yes they may require the shoulders bumping back.

 

Oh one more thing - case OAL, are all cases cut to EXACTLY the same length, this has a big effect on internal pressures / MV.

 

Ramble on!!

[Ronin]

Fxxk me

 

I started my reply when there were no replys!!

[craigyboy]

Andy its a tac20 I am shooting. Case density is probably about 90% I am a grain off compressed loads, I tired compressed loads but my chrony was up to its usual tricks, it worked all day and for the last 10 rounds it decides to give err1 readings. I had thought about neck tension, I am currently using 2 thou of tension, I have bushings for 1 thou of tension I might try out. Cases are trimmed for every firing they are on there third firing and I have to admit the bolt is a bit stiff to cam down I have been trying to get a body die but no one has one, I will have to order one from the states. I am sitting here with my load book now and on the most part variations are in the 40-30 fps range but there is always one or 2 that are way off. I have made up a chamber guage and I ma going to check my chamber length incase I am not trimming back enough, I took the chamber length from the reamer print and trimmed them back 15 thou so I cant see this being a problem but its worth checking. Thanks for the pointers gives me a few things to ponder.

[Ronin]

From what you say, i'll hazzard a guess its too much pressure caused by stretched cases - cure is a body die.

 

(or new cases)

 

You could get your smith to make a body die from your reamer?? Blank dies are available from Neil Jones custom in the states, or your smith may be able to make you a one off?

 

If your using an Arbour press (I recall you are??) I dont think you can use a body die with these (may be way off here)

 

I had a similar problem with my 6.5x284 with excess pressure in normal loads untill I realised the shoulder was moving, body die cured the problem. (so did 200 new cases )

[craigyboy]

Andy, youre right you cant use a a body die with the arbor press, I do have a rcbs rock chucker 2 though. That would be a good job if I got neil to make me a die from the reamer, as I dont really want to touch the body of the brass as the chamber is lovely and straight, a die made from the reamer would just bump the shoulders and probably not touch the body, good idea andy I will have to contact neil. I have 100 brand new brass sitting ready but I am sure this brass will work fine when bumped back, do you think it would be wise to bump them back every firing? Do you think they will need much lube, they shouldt really as the brass should fit the die it will just be the shoulders, I read somewhere the best way to set up a bump die is by feel as well as measuring i.e take out the firing pin and get a tight piece of brass and set the bump up just to touch the shoulder and keep adjusting the die down until the bolt is just a tad stiff when closing halfway down. I have been getting catred primers also, if you saw the primers from yesterday on the compressed loads, the centre of the primer is craterd and the burr is about 0.020 thivk, though I am pretty sure this is do with the slack firing pin hole also which will be rectified very soon, thanks for the help.

[Vermincinerator]

Craigy,

Over the years i have found that extreme spreads are an indicator of your loading technique rather then your chosen components, think about what you are doing when you areloading and make sure you do everything exactly the same, each time you load.

The lowest spreads were not neccessarily the most accurate.

This has been the case for both my 6BR and my 243 AI but mainly the BR.

The most accurate loads @100yds never had the lowest spreads.

The lowest spread loads would group 3/4 @100yds, 3/4 @200yds and 3/4 @300yds

Where as the most accurate 100yd load would be doing 1 1/2"-1 3/4" at 300yds.

Never resolved this but had a similar problem when developing loads for my 222 some years back.

I too was using H322 and was getting mediocre accuracy with wide spreads, i switched to Vit 133 and noticed remarkable increas in accuracy and a tightening of the spreads to single figures.

Try some Vit 133 buddy.

If this dont work have a look at your case capacity and measure it in grains of water to see if there is any descrepency.

 

Ian.

[craigyboy]

Thanks ian, if I can get my hands on some vhit 133 I will be sure to try some, its hard to get at the minute here (so is everything it seems)