| Posted: Fri Nov 13th, 2009 06:00 AM |
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M70 BOSS
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Today I checked my M70 30-06 with my COL gage. I sild the case in with the bullet loosely in the neck. The measurement that I came out with was 3.31 All of the reloading manuals list the COL at 3.340 What I don't understand is - why is my chamber shorter than the SAAMI listing in the reloading manuals?
Is it the bullet? I am loading 165 gn Nosler partition bullets.
I have some left over factory rounds the I measured. These rounds are federal premium loaded with 165 gn Speer grand slams. The federals measured at 3.180
The other rifles that I have loaded for both had throats that were longer than the listed lengths in the manuals. Please shed some light because I don't understand this.
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| Posted: Fri Nov 13th, 2009 09:16 AM |
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OldStuffer
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Difference in chamber reamer used. Apparently Remington's used at that time was 30-thou shorter throated. This is one of the reasons handloading is a very specific "science", each firearm is it's own creature, all very much alike, all subtly different.
Be advised that the more your seating depth is deeper than the load recipe was, the higher your particular pressures will be.
30-thou strikes me as a fair variance to note.
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| Posted: Fri Nov 13th, 2009 12:29 PM |
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fryboy
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every bullet is different ,they may have a shorter or longer ogive , saami specs are kinda vague ...they also have a lil leeway ( ie;min and max ...as long as it's within those ...) some companies ( such as weatherby ) make sure that the freebore is a mile long ( well it seems like it lolz)they do this to insure safety and a drop in starting pressure add to that that with use a rifles lands get worn ( look at 6mmbr.com for stories of "chasing the lands" ) when worn the lead is longer ,saami specs call for a max length ,quite often the mag is designed around this length but the chamber may or may not be ,add to that something such as a roundnose bullet will engage the lands before a long pointy spitzer will thus one will be shorter and the other longer yet both may function fine ,end result if it fits the mag u can make it as long as the chamber will allow but to make it shorter than a published recipe will indeed increase pressure
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| Posted: Sat Nov 14th, 2009 04:07 AM |
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M70 BOSS
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I figure it out. For now on I am not using that OAL gage. I measured it using a bullet, a case and locking down the bolt. Much better.
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| Posted: Sat Nov 14th, 2009 07:32 PM |
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StretchNM
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I think you have to be extra careful checking the length-to-lands that way because of bullet slip in the case mouth. I did it that way too, but recently I changed to a different method that someone described in this forum or another. I found some wildly different measurements.
Another shooter described (I have added my modifications to the procedure so it works for me):
- take a wooden dowel that will fit in the bore;
- close the bolt and press the wooden dowel against the bolt face (making sure it's not resting on the ejector);
- mark the dowel at the muzzle - accurately with a razor blade;
- take a shorter length of dowel and hot glue one of your bullets on the end (making sure there isn;t alot of slop hanging over the sides that would interfere inside the chamber throat). THe other fellow used a pencil to push the bullet to lands, but I found it hard to get the bullet inside the chamber on my 22-250!;
- remove the bolt and insert this dowel/bullet "tool" into the chamber, keeping gentle pressure against the lands;
- push the other dowel in from the muzzle until it touches the bullet. Hold it there without moving it.;
- mark the dowel at the muzzle with a razor blade (I used long, fine sewing pins pushed into the dowel for this one);
- measure between your first razor mark and your second. This will be the maximum OAL, touching the lands, for that particular bullet.
This procedure only takes about 3 or 4 minutes per bullet. I have a full woodshop so dowels, hot glue, etc are readily available to me. If you don;t, once you get the dowels and some hot glue, you'll be set. The glue doesn;t stick to the bullets once you're done with each.
For my 22-250, I measured about 7 or 8 different bullet types/weights that I use, and it took me about 30 minutes....maybe 45. I used 3/16" dowels.
I haven;t done my 25- and 30-06 yet. I'll probably use 3/16" or maybe 1/4" for the .25-06, and maybe 1/4" or 5/16" for the 30-06 if it'll fit.
As I said, I noted some major inconsistencies in some of my bullet measurements using the old method. I believe this one is more accurate. Thanks to whomever provided that method if he's in this forum and reading this.
Last edited on Sat Nov 14th, 2009 07:44 PM by StretchNM
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| Posted: Sat Nov 14th, 2009 10:13 PM |
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M70 BOSS
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Thanks stretch. I gotta go to the hardware store anyway. I'll pick the stuff up there and give it a try.
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| Posted: Sun Nov 15th, 2009 03:36 AM |
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M70 BOSS
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Yo Stretch! That worked like champ! I measured it three times and time it was within a thou or two. Best method I've used yet. Thanks for the tip. Whoever thought that up is the man!
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| Posted: Sun Nov 15th, 2009 04:37 AM |
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StretchNM
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Glad it worked for you M70. All I'm doing is passing along a good idea from another reloader. A little more confidence in the accuracy of the measurement, right? :)
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| Posted: Sun Nov 15th, 2009 04:52 AM |
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miestro_jerry
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I have seen many chambers that are in "spec" but in one case a 223 Remington bolt gun would only accept factory ammo. All of the FL SB dies available just did squeeze the case down enough. A 30-06 Savage I had wouldn't let me do oal in it, it was slightly too short for most factory spec ammo.
I buy the stuff from Brownell's to make a casting of the chamber and then try to figure out what is going on. One time I decided a simple solution was to have some one run a "known good" reamer in to the chamber, it gave the rifle another personality that was accurate but not where I think it should have been, but the guy who I had do the work, tried it on a another rifle and was really successful with that rifle. He got a Tack Driver.
So now I adjust things to the rifle and tend to mark the ammo for one rifle to be used with that rifle.
The Rem 770 I just got has a slightly different character to the chanber, not exactly sure, but RN bullets don't chamber when they are the proper over all length, but the spire points chamber easily.
Jerry
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