Overall Length Question

BearNaked

BearNaked

Beer Saved The World
Full Member
Minuteman
Feb 13, 2017
609
217
Texas
#1
I am still working on a load for my 260 Remington and have noticed something that is starting to get me worried that it was not installed properly.

I am loading 143 ELD-X and 130 hunting VLD but both of these do not get over 2.77" overall even though the caliber calls for an overall of 2.8".

I guess i always assumed the 2.8" listed was a minimum. does this sound like something is wrong or am i just over thinking this.

Would this shorter length cause a "big" spike in pressure or is it negligible?

Needless to say i wont have an issue mag feeding them.
 
#2
Case overall length (COAL) doesn't mean anything other than if a cartridge will fit in your magazine or not. Case base to ogive (CBTO) is the measurement that is importent as you are determining the distance between the contact point of the bullet and your barrel lands and yes, the distance off the lands does have an impact on pressures. Having a bullet crammed into the barrel lands can cause an unfavorable pressure spike (depending on your load) whereas just a very long COAL may have no impact on pressure at all. A Hornady overall length guage, a set of the bullet comparator bushings, a modified case in your caliber and a set of calipers will help you determine your CBTO. Hope that makes sense.....
 
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#3
I have this bullet set .020" off the lands right now but it is really short. my CBTO # is 2.126" at the lands so i will be setting them back to 2.106".

I understand the more important # is the CBTO but wouldnt the chamber, or at least in my previous rifle, need to be longer so the COAL is at least 2.8"? main reason for this thought is that i wont be able to use any factory ammo since it is based on COAL measurements with the same style of bullets (ex: precision hunter, prime, ext). So in theory, factory ammo would be jammed and cause potential issues with pressure as most factory ammo is not meant to run jammed or at least that is my understanding.

My question on pressure is before the bullet hits the lands. starting out with a compressed load versus non compressed would produce higher pressure right? even if the charge was the same? i guess the bigger question is does the pressure change whether the same charge is compressed or not?
 
#4
It's not that a bullet seated into the lands creates higher pressures, per se, it's that the pressure curve gets moved closer to the chamber causing a steeper, quicker rise in pressures. Normally, some of that pressure escapes past the bullet, before the bullet hits the lands, and pressure beings to build as the bullet moves down the barrel. Remember, as the bullet moves down the barrel, the volume containing the pressure is increasing as well. This increase in volume is offset by the speed of the powder that is being burnt, or more accurately, the amount of gas that the burnt powder is generating. Hence why different powders perform slightly differently in different length of barrels of the same chambering. It's all a fairly delicate balance, when you think about it.

This same balance is why single base cylindrical powders actually have holes that run through the kernel of powder. So that the surface area being burned increases as the kernel gets smaller through combustion. Hatcher's Notebook has a fairly good write up on this...
 
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#7
It seems short to me. Who cut your chamber? If other than a factory barrel, I'd ask the smith what dimensions he cut the chamber to and why. As you would expect, some projectiles can be seated longer than others, due to the profile and where the ogive ends up with respect to the total bullet length.
 
#8
Like Lash mentioned, that sounds a bit short. Sounds like the throat was cut short, especially given that the Berger 130 VLD's are still short. VLD's usually cause the opposite problem due to the severe taper of the ogive (usually they have to be seated way out there to be close to the lands, and magazine length becomes a constraining variable).

The key question in my mind is; How does it shoot? Do you feel limited in case capacity, having to seat the bullet so deep?

If the answer is yes for the first question, and no to the second, then just shoot on. Eventually the throat will wear and you'll have to seat bullets further out to maintain your bullet jump anyways.

JMTCW...there's a lot of ways to skin this cat.
 
#9
I got the barrel from northland shooters supply.

Honestly, i cannot get the 130's to shoot at all and have now moved on to the 143 eld-x to see what they do.

the best the 130's provided at 300 yards was a 5" group during load development using Reloader 17, IMR 4451, H4831SC. i would rather just go back to my 20" 308 if that is the best i am going to get out of a 260 rem 26".

Ill call northland later today but i think i am SOL on this being i have shot several rounds through it.
 
#10
A sammi spec or even a match grade chamber should be able to handle factory loads without issue. If your throat is so short you can't run factory 260, something very strange is going on. Was this a barrel blank that you had a smith chamber?
 
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