300 win mag OAL question

[TraumaControl]

Rifle: Remington 700 Magpul Elite
Bullet: Nosler RDF Ultra High BC match bullets 175 gr HPBT

I used Hornady's OAL guage with modified case and I am getting a measurement of 3.5" as the ogive hits the lands.

Federal Premium Gold Medal match grade ammo is 3.328-3.333" OAL and groups 3/4 MOA.

I want to develop a good load for the rifle and after reading a bit regarding OAL I am at a loss on how to shorten the distance of free travel before the rifling without going over 3.34" overall length. I have two loads the I loaded initially with OAL of 3.333 and weighed out the brass and bullets trying to be as consistent as possbile, but this OAL free travel thing is throwing me for a loop. Should I just not worry about it too much as long as the loads I test group okay?

 

[nn8734]

You don’t have to worry about OAL other then ensuring it fits in the magazine. I’d start at .030 off the lands and go from there, tweaking the jump inward or out until you get single digit SD and sub-25 ES and vertical dispersion at 300 is 1 MOA or less.

Assuming that’s what you do, your case head to ogive will be 3.470”

Alternatively, you can try to get close to the FGMM load by pulling one apart and weighing the charge (not sure what powder they use or what you are using) but I believe they use a 215M primer.

I’d also consider 185 Berger Jugs if the 175 Noslers don’t work out. BC is .560 vs .536 for the RDFs

 

[918v]

You’re not hitting the lands at 3.5” with the RDF.

 

[TraumaControl]

What would I be hitting then? Advanced the modified case and OAL gauge into the chamber with the bullet seated in the case. Once it stops I advanced the plunger gently to advance the bullet. Once I met resistance I secured the plunger and removed the gauge and case from the chamber. The bullet was lightly stuck in the barrel and was shaken free and replaced in the modified case with the secured plunger. Measured with calipers and repeated 15 time and came out 3.5” every time.

 

[nn8734]

What would I be hitting then? Advanced the modified case and OAL gauge into the chamber with the bullet seated in the case. Once it stops I advanced the plunger gently to advance the bullet. Once I met resistance I secured the plunger and removed the gauge and case from the chamber. The bullet was lightly stuck in the barrel and was shaken free and replaced in the modified case with the secured plunger. Measured with calipers and repeated 15 time and came out 3.5” every time.

Sounds like you’re performing the procedure correctly, maybe just double check the measurement itself.

I am at the lands with my win mag / 190 SMKs at a loaded round oal of ~3.6ish, depending on the ogive of the specific bullet being measured (don’t have the rounds in front of me at the moment otherwise would measure).

Im not immediately familiar with the RDF but the 175 smk would require a longer oal than the 190 to hit the lands.

 

[918v]

175 RDF needs at least .070” more COAL than SMK to hit the lands. The RDF nose portion is that much longer.

Maybe the freebore has a burr. I would break the barrel in before taking any measurements.

 

[TraumaControl]

Re did the measurements again. Using modified case with OAL guage.

Federal GMM OAL OAL 3.331"
Modified case with guage measures 3.500" with 175 gr RDF bullet
Modified case with SMK 180 gr bullet 3.514"

Gauge was zeroed. Rechecked measurements 10 times and they were all consistent. No burrs.

So going forward, if I want to load to decrease free travel, it seems I should test from 3.47 OAL for RDF?

 

[spife7980]

If that’s what you get then that’s what you get. You now know your max length for the chamber. Start at that length if it can fit in your mag, if not then shorten it until it does.

Next is to get the Hornady bullet comparators so that you can measure based on the ogive riiiiiight in front of the bearing surface where the bullet actually touches the barrel instead of the nose that floats in space.

 

[FredHammer]

I think it might be best to just load everything to max allowable magazine length and tweak accuracy with everything else. I’ve gone down this distance to lands rabbit hole and discovered some of my most accurate loads were .060-.095 off the lands.