Help with .270 COL

[USMCDM24]

So I started this in another post but it leads me into another question not related with that post. Anyways, I'm trying to find a starting COL for my M700 in .270. So here's what I've found out so far...

I've started with a "dummy round" (just bullet & case, no powder/primer) loaded a little long, put dry erase marker on the bullet & tried to chamber it. I gradually went down on my seating press until it would chamber & the rifling would no longer leave "scratch" marks in the dry erase mark. I then went down 1/2 turn more on the seating press (I read this is a good way to get a good starting COL if you don't have equipment to do so). My COL is 3.467" & has enough room to load in my magazine & can still be chambered.

My questions are: 1) is this a good (translated: safe) way to get a good starting COL? & 2) does a COL of 3.467 sound about right? The cartridge seems a little "long" although the bullet is seated 0.36".

I plan on starting with 54gr of H4831 (as recommeded by one of the folk on the other post) under a 140gr Ballistic Tip.

 

[JD338]

You are spot on.
Now if you were to measure a shell that is touching the lands and subtract your loaded overall length, the difference is what you are off the lands. A good starting point is .020" off the lands.

Let us know how she shoots!

JD338

 

[USMCDM24]

Thanks for helping out a newb JD. This is a great forum.

 

[JD338]

Thanks for helping out a newb JD. This is a great forum.

Happy to help you out buddy!

Let us know if you have any more questions, there is a wealth of knowledge here on the Nosler forum. :wink:

JD338

 

[USMCDM24]

So started loading some work-up loads with the COL up above. What is a tolerable variance between overall lengths? I use an RCBS RC with RCBS dies & sometimes I can go through seating 5-6 bullets with a .002" variance but then I will seat the next bullet & it will be .005" to .010" longer/shorter than the previous. I have checked that die is tight with the lock screw tight as well & use the exact same stroke each time. Is this an acceptable variance between cartridge lengths? I just want to make sure.

 

[JD338]

You will be fine. Just make sure you have enough clearance in the magazine.

JD338

 

[rick smith]

If you are measuring to the bullet tip, you can expect larger differences than if you measure on the ogive. Get yourself a Stoney point tool or similar device that will measure on the ogive and I think your differences will go down. Ideally you want your loaded rounds to measure as close as possible to the ogive not the tip.Rick.

 

[USMCDM24]

So looking at Cabela's (which I love their products for the price) I see a Hornady (I believe used to be Stoney Point) Chamber All & an OAL gauge (w/Modified Case). It looks like the Chamber All attaches to your caliper to measure your seated cartridge where the OAL gauge will measure your rifle chamber. So to get consistant seating best "tuned" to my rifle, would I need to purchase both?

 

[USMCDM24]

To follow up, I eventually want to try a bunch of different bullets & although the method I used on the bullets I've already tried (only 2) seems to work decent it seems to be more time consuming & a maybe a little less accurate than using the gauges above.

 

[rick smith]

Forgot they were purchased by Hornady. The modified cases are used for finding seating depth to the lands. The Kit that comes with the different caliber inserts is used to measure to the ogive on the bullet, a far more accurate method than using the bullet tip. They also have collars used to measure the headspace of a fired round from your rifle. Very useful for setting FL dies when the case starts getting tight in the chamber.
You need to expand your catalog selection so you can be like the rest of us and acquire more neat tools, go to be a gadget guy if you load your own. Sinclair International, Midway USA, Dillon Precision, Midsouth, Natchez just to name a few.Rick.

 

[USMCDM24]

Thanks Rick. I'm a total gadget guy so chances are I will buy all of the 'toys' that go along with reloading.

 

[Hegland]

USMC - I had a similar experience a while ago with my .270 in a Vanguard rifle. I had what I thought were abnormally long cartridge lengths, around 3.45", as well as .010" variations in overall length. So, I bought a comparitor and here's what I learned:

1) The longer length was insignificant; no pressure signs on fired cases, accurate, and plenty of room in the magazine.

2) The differences in overall lengths, when measured off the ogive of the bullets, turned out to be only one or two thousandths instead of the 10 when measured from the plastic tip.

As a side note, I had much better luck with H4350 than with either H4831 or Rl22, which are usually the go-to fuels for the .270. Was shooting the 140 accubonds and 130 solid bases.