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Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 6:42 am
by Promapper
OK, have only been loading metallic for a couple of months and keep trying to refine everything. Isn't that the point?

At any rate I have a couple of questions if you please.

1. Starting with a published case trim length.
what effect does the trim length have if it is short or long of the published "trim to" length?

2. I am using the standard RCBS seating dies and am having trouble getting any consistency on overall length. In the case of the 22-250 the starting length is 2.35. Without changing the die it varies from 2.348 to 2.354,
what sort of tolerances should I be looking at. I would like 1/2 MOA from the 22-250 and the 204. groups of 5 show that can happen but there is the flyer issue and I can't help but think the length is one of the culprits.

in seating the bullet I will twist it 180 degrees and seat again.
using hornady brass and Hornady 52 gr BTHP Match with Varget

And yup, I check the caliper zero before and after I measured them.

Here are the specs for the caliper
Accuracy: +/-0.001" (+/-0.02mm)
Resolution: 0.0005", 0.01mm, 1/64"
Repeatability: 0.0005", 0.01mm, 1/64"

Here is a sample string;
2.3500
1.3470
2.3490
2.3495
2.3520
2.3585
2.3480
2.3480
2.3495
235.40
2.3525
2.3525
2.3525
2.3500
2.3505
2.3500
234.60

What tolerance should I be looking at that are reasonable?

Thanks

Greg

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 7:01 am
by Rick in Oregon
Mapper: What you are most likely seeing is very small variances in the bullet tip, thereby giving erronious overall length readings. I suspect this is the case, especially if you are using poly-tipped bullets, as they always give small length variances as you describe. What really matters is the overall length in terms of base to bullet ogive....THAT'S the part that really matters, save for fitting into the magazine if that matters. Do yourself a favor and get a bullet comparator like the Hornady tool.

As for case length, you do want to trim your cases as close to the same length as possible. Minor differences in case length affect bullet grip/tension, and can show these variances on the target as vertical stringing (usually). If all your cases are say, .005" under trim length, no worries, if they're a tad long, just trim to the shortest case length for consistency.

One thing I'll pass along, is to not trim your new cases until AFTER they've been fireformed in your chamber. Trimming brand new cases is an excercise in chasing your tail, as they'll all change length somewhat at the first firing, and none of it will be consistent; some will even get shorter.....best to wait until they've been fired in your chamber, THEN trim to the shortest case length, keeping the "book trim length" in mind.

Keep everything as consistent as possible, and you'll get those .5" groups you're chasing. Oh, and welcome to the 204um! :D

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 7:05 am
by Promapper
Thanks Rick, makes perfect sense.

The 204 is a DPMS upper so the overall length is an issue there but the 22-250 is a savage single shot bull.

I will look into the tool you recommended.

Thanks again for the info and the welcome.

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 7:40 am
by bow shot
Rick nailed it as usual!

Promapper, you will never go wrong listening to Rick in Oregon ("RIO") :) .

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 7:51 am
by Rick in Oregon
Gee, thanks bow shot....appreciate the vote of confidence. :D

Now, I've got this great deal on a bridge near you for sale........ ;)

Say, doin' any good on those NY groundhogs this season?

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 7:56 am
by Bill K
bow shot wrote:Rick nailed it as usual!

Promapper, you will never go wrong listening to Rick in Oregon ("RIO") :) .
Oh, I question that.. :D He will lead you, next, down the rosey path of the 20VT... :eek: Bill K. Just joshing RIO.. I am so happy with that 20VT alongwith the 204Ruger.. :)

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 8:06 am
by Rick in Oregon
Bill: I just call 'em the way I see 'em. :D

I had two of my Coopers out for a few days last week...the 204 and the 20VT. The wind was mild, so I just shot the 20VT...ranges out to around 400 yards as the wind wasn't too bad (10-25 mph).

Here's a shot of the 20VT taken during tear down at the end of a glorious day of launching Skippy and his pals (see that rich green alfalfa down there? Chaulked full of ground squirrels by the thousands.):

Image

When you can launch a rat at 350-400+ yards with the VT, no need to grab the 204 unless you really need to stretch out there, or the wind becomes a factor. In a perfect world, WE NEED BOTH! :eek:

Promapper......sorry for the OT, but it's all Bill's fault! ;)

Re: Chasing my tail? .0030 +-

Posted: Tue May 08, 2012 5:11 pm
by bow shot
I only dispense fact, Rick...

'Funny you should ask about the chucks! I have an eary a.m. appointment with the turkey woods, and then its off to the farm down the road. I just got the nod to do an eradication job on the field that I was (gently) excluded from last year. I know there were 4 there, and I have all their holes lasered! Time for critter wackin'!!! Pics to follow!

Re: Chasing my tail? .0030 +-

Posted: Wed May 09, 2012 10:13 am
by Tokimini
bow shot wrote:Rick nailed it as usual! Promapper, you will never go wrong listening to Rick in Oregon ("RIO") :) .
RIO is a wealth of information when it comes to reloading and his advice has helped me out more than once.

Re: Chasing my tail? .0030 +-

Posted: Thu May 10, 2012 7:38 am
by bow shot
Hay is too high ... dang. Look out after the 1st cutting, 'chucks.

Re: Chasing my tail? .0030 +-

Posted: Thu May 10, 2012 8:25 pm
by RAMOS
I really should not go down this path, but somehow I can't resist. Evidently, I posted in agreement with RIO's thoughts a few too many times. Got a PM accusing me of being less than a man and sucking up to fit in. I took offense (in private), because last I checked, I had pretty good evidence of being a man. Not just anatomically, either. Anyway, the point is, Rick aint just a talking head. He can back up his advice with empirecal (sp) evidence. Taking his advice is a pretty safe bet. Crud, here I go again, sucking up! And, just for the record, we do not agree completely on everything. The only thing I would add would be be to measure your' actual chamber length to determine your' trim to length.

Re: Chasing my tail? .0030 +-

Posted: Fri May 11, 2012 7:27 am
by Bill K
Ramos.. Not to worry, many of us on this program use and appreaciate Rick's information and input. I would bet, that as I have found out after many years dealing with people, those the come up with comments like you stated occured, are having fits of jealousy. :P So just disregard, as you appearantly have, and enjoy our sport, fellow posters and shoot straight. :D :D Bill K :)

Re: Chasing my tail? .0030 +-

Posted: Fri May 11, 2012 7:40 am
by RAMOS
Me worry? No, just got my hackles up for a moment. Only happened with one individual. Considering how many members we have and everything discussed, can't imagine an easier bunch of folks to get along with. I was just having a bit of fun with my earlier post. Hope it got a chuckle out of Rick.

Re: Chasing my tail? .0030 +-

Posted: Mon May 14, 2012 7:10 am
by Rick in Oregon
:lol:

Yup, you did, and I know the clown who you are referring to. Don't see him about here too much lately either....all the better. Heck, we're all just tryin' to have fun here.

But thanks for the votes of confidence.....I just hope I'm worthy. Right now I'm just thinking about the pending squirrel trip and all the stuff I've gotta get ready. The sun is shining, the rats are plentiful, ammo loaded, the crew will be here soon.......gads, I love this time of year! :eek:

Re: Chasing my tail? .0030 +-

Posted: Mon May 14, 2012 7:35 am
by RAMOS
Promapper, did you get everything sorted out?

Rick, have fun feeding the raptors! Our weather the last few days has been perfect as well. Long time coming :)