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C O L
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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Daveyboy
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PostPosted: Tue Jun 27, 2006 1:40 am    Post subject: C O L Reply with quote

So I'm loading some ammo for my Tikka in 6.5 x 55 swedish.

I use the stoney point OAL guage and then measure the length with a collet on the ogive of the bullet. Write down the length, take away 0.03 of an inch and that will do. Very Happy

So I get an empty case in the press and load a bullet. Keep adjusting it down until I get to the desired length and pop it into the chamber. will it fit? Nah! Way out! Shocked Shocked

so I press it in a bit more, check, no - press a bit more, check, no. Even did the trick of colouring in the bullet with a black marker pen to show the rifling scraping against the bullet. The two measure ments are way out. wtf

Finally, my Federal factory ammo is 2.93 inches and my homemade's are 3.0 inches. Down in length by over a tenth of an inch from what I measured with the guage.

Any comments?

D

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guncollector
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PostPosted: Tue Jun 27, 2006 7:54 am    Post subject: Re: C O L Reply with quote

I always take several OAL measurements with the Stoney Point gauge to make sure that I am just touching the lands and not pushing the bullet in a bit. This is a bit tricky with long, tapered bullets as there is not much difference in the diameter of the bullet from one point to another a few hundredths of an inch away. Rahter than averaging a few measurements, I keep measuring until I get 3 consistent readings.

I've also found that with some bullets, the taper is not the same from one to the next. Nothing you can see but you can measure it by measuring the COL using a Stoney Point collet on your micrometer and checking each bullet as they come out of the seating die. I beleive the seating die is putting them in the same length and variations are due to bullet variations. Unless you have some really crappy bullets, I doubt that this was your problem.
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popgun
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PostPosted: Tue Jun 27, 2006 9:43 am    Post subject: Re: C O L Reply with quote

Different bullets will have different readings on the Stoney Point COAL Guage. Then throw in that different guns have different distances to the lands AND magazine lengths you will have to take all into consideration when settling on a starting COAL for testing. Your first limitation unless you load one at a time is the magazine length. The second consideration is the distance to the lands and can you reach them at magazine length? Heavier bullets or a bullet from a different manufacturer will let you get closer to the lands too. If it's a hunting gun start with the maximum magazine length and shorten the COAL to see if you have an improvement. You will find that you can get a good accuracy load without being too concerned with seating near the lands.

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Daveyboy
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PostPosted: Tue Jun 27, 2006 9:56 am    Post subject: Re: C O L Reply with quote

Hi Gang

How far out do you want these bullets to be? These 6.5 swede's stick out like a bulldogs dangly bits!

I see what you are saying but popgun, if I went to the magazine length they wouldn't be in the case - seriously! and i'm using Nosler 120g balistic tips all out of the same box.

I took lots of readings. With the collet on top of the bullet I measured the maximum length to be 3.151". The factory ammo measured 2.938". I wanted to get to at least 3.1" as I reckoned this would minimize bullet jump, keep the pressures down - all that stuff. So I made one round - without the powder or the primer- and tried it in the chamber. Not a chance. It finally fitted at 3.0" which is 0.062" longer than factory but not at my target length. Standard Redding dies mean that you can be only so accurate - no competition die in this calibre.

Keep at it

David

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popgun
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PostPosted: Tue Jun 27, 2006 10:40 am    Post subject: Re: C O L Reply with quote

All part of the variables with your magazine length longer than the distance to the COAL of a round seated near the chamber. In any event don't be afraid of bullet jump. Some bullets will only shoot accurately with a long jump to the lands.
You are using a comparator on the factory round and it was loaded to SAMMI standards for Over All Length and not to any standard close to the lands (Comparator Over All Length). SAMMI ignores that factor all together and sets a chamber standard in a +- range and a standard seating depth.
Loading on or near the lands is an advanced loading technique that is used by target and varmint shooters and those reloading on the anal end for an everyday hunting rifle. I resemble all of those remarks ;-)
Just trying to say to not get your shorts in a wad about the distance to the lands. You can find an accuracy load at the Factory cartridge length, longer or shorter. It only costs you bullets, primers, powder and time on the range to find out. That is the only way to find out what your rifle prefers. Start simple and work up to complicated if you have to. Something as simple as changing a primer or powder may drop you into incredible accuracy without worrying about seating depth. I only wish the homework in school was as much fun and doing the homework on the range. Very Happy

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Spacedone
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PostPosted: Tue Jun 27, 2006 11:33 am    Post subject: Re: C O L Reply with quote

personally i dont worry alot about C O L. i prefer to use bullets with a crimp groove. i cut my cases to proper lenght then just load the bullet into the case until the crimp groove is 2 thirds of the way into the case and then i crimp the case

since im not shooting a 10,000 dollar target gun in super compitition i try to make all my ammo as close as possible round for round.

it doesnt have to be perfect as long as its consistant and safe.

if my shells all shoot 1 inch high and 1 inch left at 100 yards then i know that they are shooting 1 inch and 1 inch and i can compisate for that.

i know this isnt what the loading books say but after measuring a couple dozen boxes of factory ammo i noticed that even factory ammo the C O L isnt always the same changing slightly from Lot to Lot.

i crony all new loads and if my presssure isnt getting to high i load every shell as close to lenght.

one of the great things about not loading MAX loads is you have a large leeway from shell to shell.
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Handloader
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PostPosted: Tue Jun 27, 2006 10:41 pm    Post subject: Re: C O L Reply with quote

Allow me to confess that I have never realized any advantage using the comparators or other devices to establish COL. Using a resized case, trimmed to the required chamber/throat of a specific rifle (again, I confess to never relying on book measurements for trim length) I find it easy to simply seat a bullet only deep enough to have the closing bolt engage the bullet into the lands. Once this depth is established for a specific bullet, then it is a matter of simply adjusting the seating depth for either the lands or the magazine.

While various manuals will recommend between .15 and .40" for optimum seating depth from the lands, experimenting for me has shown accuracy advantages relative to seating depth. No surprise here. What is interesting is that there seems to be no constant as to what seating depth will deliver the best accuracy.
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george20042007
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PostPosted: Tue Jun 27, 2006 10:48 pm    Post subject: Re: C O L Reply with quote

Handloader wrote:
What is interesting is that there seems to be no constant as to what seating depth will deliver the best accuracy.

Confused I think it's the one that results in accuracy Bonk
Keep it coming...
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Daveyboy
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PostPosted: Wed Jun 28, 2006 1:42 am    Post subject: Re: C O L Reply with quote

Y'know Handloader, that's the way that i've ended up doing it. The bolt wouldn't close so I put the round back in the press and seated it deeper and deeper - by the depth of a gnats todger - until I could get the bolt to close. I've loaded up with 3 different powders so I'll try them out and let you know how they group.

Thanks y'all

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rrogacki
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PostPosted: Wed Jun 28, 2006 5:39 am    Post subject: Re: C O L Reply with quote

DaveyBoy,

There must be something about Tikka's. I have a T3 in .270 and if I seat the bullet according to my OAL gauge, the loaded rounds won't fit in the magazine, but chamber fine. What is going on with the Tikka's ??

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Daveyboy
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PostPosted: Wed Jun 28, 2006 5:56 am    Post subject: Re: C O L Reply with quote

rrogacki

Mine is the other way 'round. Loads of space in the magazine - although I have had this problem before in a .308 - but the damn things won't go in the chamber.

Still... Out on Friday AM so I'll know how they group.

d

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rrogacki
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PostPosted: Wed Jun 28, 2006 6:05 am    Post subject: Re: C O L Reply with quote

DaveyBoy,

Good luck - I hope you get the grouping size you are looking for. Let us know how it works out.

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guncollector
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PostPosted: Wed Jun 28, 2006 6:54 am    Post subject: Re: C O L Reply with quote

Daveyboy, unless I am missing something, the only way that the round won't allow the bolt to close is the bullet is running up into the lands. Somehow when you measure OAL using the SToney point stuff, you are getting a reading that is too long. Are you using the right collet for the 6.5 caliber?

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Daveyboy
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PostPosted: Wed Jun 28, 2006 9:53 am    Post subject: Re: C O L Reply with quote

The right collet? Well that I don't know about.

I chose one of 4 that fitted and used it on my factory and home made's. I thought that if you used the same collet then you would get consistant results. Same kit, same measuring method, same technique...

Am I about to learn something here? Shocked

Daveyboy

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rrogacki
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PostPosted: Wed Jun 28, 2006 10:05 am    Post subject: Re: C O L Reply with quote

Daveyboy wrote:
The right collet? Well that I don't know about.

I chose one of 4 that fitted and used it on my factory and home made's. I thought that if you used the same collet then you would get consistant results. Same kit, same measuring method, same technique...

Am I about to learn something here? Shocked

Daveyboy
DaveyBoy,

When useing the StoneyPoint Bullet Comparator, you need to use the collet that matches the caliber of your bullet. The set I have (B234-678) comes with the following collets - .224 (5.56mm), .243 (6mm), .257, .277, .284 (7mm) and .308 (7.62mm/8mm). Set B-14 comes with the 6.5mm collet and 13 other collets, but I believe you can order individual collets from www.midwayusa.com. If you don't use the right collet, your measurements will be way off.

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