Coal issues

[pow1]

Quick question quys:

 

Been measuring to find the coal but am getting funny results..

 

I used 3 neck sized cases (previously shot from my rifle), one with a small cut in the neck, other with a bigger cut and the last with no cut.

 

All 3 give different lengths to the other, but each gives the same with different heads..

 

Id have thought once hitting the lands thats it, its I the case at a set distance and can't go any further in irrespective of the resistance from the case!

 

Advice would be greatly received!

[Andrew]

Maybe the ogives on the first bullet aren't consistent? ~Andrew

[pow1]

I tried with 4 different heads in each case, each is consistent in each case.....

[Andrew]

I see. I thought you tried another form of bullet in the same four cases and all came out the same.

 

You could do without this and simply load to listed OAL.~Andrew

[jcampbellsmith]

....You could do without this and simply load to listed OAL.~Andrew

 

+1. I find as I reload more, I take fewer and fewer measurements. All I look for these days is a round that fits the magazine and chambers without any issues.

 

Regards

 

JCS

[gbal]

Pow, Andrew and JCS are essentially loading as do commercial ammo companies-'one size fits all'-so long as it is to SAAMI (or CIP in Europe) dimensions-which is what chambers and magazines are made to. Many reloaders want to fine tune ammo to their rifles preference,which may be a tad more accurate. For hunting (ie fairly large kill zones,say 1+moa,it probably matters but little-which is why commercial ammo works finea half inch eithe way won't be a failure fot that reason.

 

Re length-bullets from the same box often vary a good few thou ", so if you measuring COAL (cartridge overall length) the same length might mean differnt seating depths/jump to rifling-which may matter in fine tuning.Better by far to use cartridge base to ogive,as the ogive is more consistent,and cartridges loaded to same catridge base to ogive will have the same 'jump' even if not the same irrelevant COAL (COAL matters for fitting the magazine,of course. Use a seating depth guage too (with screw on dummy cartridge).

Bryan Litz of Berger Bullerts has a brief explanatuon of this,well worth reading (COAL v CBTO).

 

(Do you have any problems with your current reloads...how do you measure 'hitting the lands'-in itself not typically the best shooting position for many rifles ).

 

gbal

[jcampbellsmith]

http://www.bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-1/

 

http://www.bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-2/

 

Regards JCS

[pow1]

Gbal,

 

I havent reloaded for the creedmoor yet (thats what thos is for).

 

I have happily used this method for my 308 and use 30 tho jump successfully.

 

Im just really confused as to whats happening here:(

[pow1]

Gbal,

 

I havent reloaded for the creedmoor yet (thats what thos is for).

 

I have happily used this method for my 308 and use 30 tho jump successfully.

 

Im just really confused as to whats happening here:(

 

I use the hornady comparator with insert with my digital calipers to measure.

[gbal]

pow,OK-it's not very clear just what the issue is...

I don't get what a small cut in the case is,or a 'bigger cut'...tight neck chambers need. Outside neck cutting,but you would have said if your rifle is a tight neck....

Could you possibly mean 'neck sized' to differnt depths-pretty unlikely scenario,and the 'uncut' one wouldn't then chamber...???

Are the three cases (small,bigger and no 'cut" ) different lengths?

You say the three give the same COAL (?) but with differnet bullets (possible,of course as bullets differ in length,especially when differn makes etc-seems unlikely that they would just all 'cancel out' the bullet differnces with the case differnces....are you using 'differeent bullets (makes etc)?...with the same press/bullet seater...?

I can't make much clearly of your last point either.

Some might be my lack of understanding,but it does seem to lack clarity....so it's hard to suggest much....HOrnady comparator/insert is OK,the optimal jump (note jump-ie off the lands) for the 6.5CM may well be less than 30thou,butthat's not the issue here...("resistance from the case"....? Unclear,but don't force anything...are 'loaded' rounds chambering,or what....???

 

g

[Laurie]

The SAAMI standard leade (ie the parallel 'freebore' section ahead of the case and before the throat leading into the lands is specified at only 0.2645" diameter for the Creedmoor - that is a mere half thou' larger than the nominal 0.264" bullet diameter. At least one model of 6.5mm bullet I have tried miked out at over this figure, and most are the full 0.2640". The 260 Rem is also specified at this value and I can only assume this is a hangover from the bad old days of US ignorance about 6.5mm cartridges when most American models were made with 0.263" shanks.

 

In any event, 260 chambers seem to be cut with suitable clearances here, but there are lots of stories of 6.5 Creedmoor rifles where the bullets touch the leade sides and need pushing through. So far, I've encountered two such chambers - one custom; one in a factory Savage 12 LRP. The former was so 'tight' it actually left shallow rifling marks on the bullet if you chambered then unloaded a round.

 

I found using the Hornady / Stoney-Point OAL gauge / modified case on the Savage that some bullets slipped through the leade OK, some were checked and needed a hard push to get through this section to the throat. The 140gn Nosler CC was fine, the 139 Scenar and 142gn SMK weren't. If the bullet is just 'kissing' the leade walls, the split case-neck system simply won't work - the bullet will be pushed back into the neck by differing amounts each time you try - I suspect this is your problem.

 

Moreover, if the bullet touches, it affects performance, pressures and depending on the degree of friction may see serious copper fouling of the barrel in relatively few rounds. Such chambers need the leade polishing out a little.

 

The factory Savages apparently suffer a lot from this with the manufacturer presumably using reamers until they wear right down to minimum SAAMI - there are many posts on the 6.5 Creedmoor Forum bemoaning this. I hope Savage has realised there was a problem and changed its specs a little.

 

To see if you're suffering from this, make up an inert round with each bullet you're loading to the SAAMI COAL and carefully chamber / extract it. If you suffer from the problem you'll have scuff marks all around the shank - not to be confused with a single scuffed are caused by the bullet touching the feed ramp / chamber lip as it is chambered.

[Laurie]

The SAAMI standard leade (ie the parallel 'freebore' section ahead of the case and before the throat leading into the lands is specified at only 0.2645" diameter for the Creedmoor - that is a mere half thou' larger than the nominal 0.264" bullet diameter. At least one model of 6.5mm bullet I have tried miked out at over this figure, and most are the full 0.2640". The 260 Rem is also specified at this value and I can only assume this is a hangover from the bad old days of US ignorance about 6.5mm cartridges when most American bullet models were made with 0.263" shanks.

 

In any event, 260 chambers seem to be cut with suitable clearances here, but there are lots of stories of 6.5 Creedmoor rifles where the bullets touch the leade sides and need pushing through. So far, I've encountered two such chambers - one custom; one in a factory Savage 12 LRP. The former was so 'tight' it actually left shallow rifling marks on the bullet if you chambered then unloaded a round.

 

I found using the Hornady / Stoney-Point OAL gauge / modified case on the Savage that some bullets slipped through the leade OK, some were checked and needed a hard push to get through this section to the throat. The 140gn Nosler CC was fine, the 139 Scenar and 142gn SMK weren't. If the bullet is just 'kissing' the leade walls, the split case-neck system simply won't work - the bullet will be pushed back into the neck by differing amounts each time you try - I suspect this is your problem.

 

Moreover, if the bullet touches, it affects performance, pressures and depending on the degree of friction may see serious copper fouling of the barrel in relatively few rounds. Such chambers need the leade polishing out a little.

 

The factory Savages apparently suffer a lot from this with the manufacturer presumably using reamers until they wear right down to minimum SAAMI - there are many posts on the 6.5 Creedmoor Forum bemoaning this. I hope Savage has realised there was a problem and changed its specs a little.

 

To see if you're suffering from this, make up an inert round with each bullet you're loading to the SAAMI COAL and carefully chamber / extract it. If you suffer from the problem you'll have scuff marks all around the shank - not to be confused with a single scuffed area caused by the bullet touching the feed ramp / chamber lip as it is chambered.

[pow1]

Gbal, by cut in the case i hacksawed a small notch in the neck to allow for the head to seat more easily.

 

I measured all 3 cases and they are the same length!!

 

Out atm, but will be home later and will reply properly!