Reloading 223 for a Mossberg MVP Predator - Bolt Action

[robertvarner]

I've recently started reloading and have been consuming information with a fire-hose about the subject. I've run into a question I need some help with from those with more experience in this subject area.

I want to determine which C.O.A.L to use for reloading different bullet types like HP, SP, FMJ, or V-Max. So, I slit the neck of a case with a dremel tool to allow me to slide a bullet into the brass, but with enough tension to hold it in place. Then I inserted a round manually into the chamber and carefully closed the bolt.

This process came from some of my reading and viewing the "Gospel of YouTube" videos , where you could measure C.O.A.L when the bullet slides into the case until it hits the lands when the bolt is closed. There are several methods that I found on the subject. This is one i selected to try.

I carefully removed the round and used digital calipers to measure the overall length as follows:

• 55g HPBT 2.301 in
• 55g SP 2.313 in
• 55g FMJ BT 2.363 in
• 53g V-Max 2.436 in

What I am seeing is these case length measurements are different than those found in the reloading data books and internet for their recommended C.O.A.L. for several loads. It appears the COAL lengths in the data loads would be short in my Mossberg MVP, leaving a considerable gap before the barrel lands. I can't find any data on what the C.O.A.L should be on my Mossberg either.

Are my assumptions correct? Can I use my measurements lengths (minus several 1000s) as a guide for reloading for this Mossberg MVP or should I stick pretty close to those found in the documented data loads; Lee, Hornady, etc?

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[Greenbug]

Your reloads will still need to fit in your magazine (unless you only plan to single load them). Standard AR magazine that fits in you Mossberg kinda limits the overall cartridge length to about 2.250" on the 223/556. If using your rifle as a repeater you will not be able to load your cartridges to match your throat depth and still fit in the magazine.

 

[robertvarner]

Your reloads will still need to fit in your magazine (unless you only plan to single load them). Standard AR magazine that fits in you Mossberg kinda limits the overall cartridge length to about 2.250" on the 223/556. If using your rifle as a repeater you will not be able to load your cartridges to match your throat depth and still fit in the magazine.

That was my other concern. I did not want to add that rambling from me, since my message as getting long already. The rifle is already pretty accurate with the loads I shot today (within 1 MOA), but I was just trying to squeeze more accuracy out of it if I could.

The load data I've seen recommend 2.200 inches. If I get as close as the AR Mag will allow of 2.250 in, will that add additional accuracy or am I chasing-rainbows?

 

[ron]

I reload thousands of 223 match ammo annually for an ARs. Load to bullet manufacture
case OAL data to fit the magazine. Long range bullets like Sierra 80 grain SMK and Hornady
75 grain A-Max are loaded on the lands or a few thousands off. Only for 1/8 or faster
twist barrels. These special long range bullets do not shoot accurately jumping into the throat.
As the barrel wears my 80 SMK are loaded farther and farther out. Until it is time for a new barrel. These long range bullets will not fit the magazine single load only.
I love your home made tool. But Hornady sells a bullet comparator and oal gauge to measure
from the ogive of the bullet.
Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO) - Part 2

Your Mossburg is a 1/9 twist? Here is an excellent load for 200 yards or less for about any
twist rate barrel. Sierra 53 SMK and 26 gr WW 748. 2.250 OAL, Winchester brass. The 53 SMK
is a flat bottom bullet. You will need to chamfer the case mouths. WW 748 meters perfectly.
As always check all recipes with published data. I like these load data books. All major
bullet and powder manufactures.

 

[robertvarner]

Thanks for the info. I've looked for that book, but it was put of print then. Will need to wait until I can find a location where it is available or reprinted (possibly in digital form?).

The tool I built was made using two thumbscrews and two connector nuts. The thumbscrews are tapped into the side and can clamp in place on a cleaning rod that slides down the barrel measuring the distance between the bolt head and the tip of the sliding bullet resting on the lands.

I made it in an hour without having to spend more than $10 on parts. And, since I'm a tinkerer my labor was worth it. It's my newbie energy working on figuring things out.

I wonder if there is a way to build a floor plate similar to my Rem 700 that could replace the AR mag that has length limitations. That seems odd, but I still wonder if the accuracy attempt is worth it.

 

[osprey]

Pri magazines will allow you to load to a longer coal than any other mag and are very high quality. Precision Reflex - Product Detail - PRi 5.56 / .223 15 Rd. Steel Magazine - Add To Cart To See Price

 

[ron]

Midway and Brownells has the load book in stock.
Loadbooks USA 357 Sig Reloading Manual - MPN: 357 Sig
https://www.brownells.com/reloading...manuals/loadbook-223-remington-prod87632.aspx
The tool you built does not measure off the Ogive. Look at the article from Berger I posted above.
Bullet tips very too much for an accurate measurement. Load your bullets to magazine length
OAL from bullet manufacture load data. Forget this throat measuring stuff this is for specialty
long range bullets your rifle twist rate cannot stabilize these. Start with one bullet and powder
combination. And change only one variable at a time. I do 5 round batches varying powder
charges by .2 grains. Shoot the 5 shot groups see what your rifle likes.
FYI Most 55 grain FMJ bullets do not shoot that well. Try the recipe I have posted above
and see if you can beat it.
From the bench 5 rounds @ 100 yards .2" group. AR 20" Service Rifle with 2X7 Leupold.

 

[robertvarner]

Great information! Thanks.

 

[Bealzybub]

There are other things involved too that you have to factor when utilizing a measuring system as you've devised or with the other tool posted above. I have that tool. As previously mentioned with your twist rate you're going to have to stick with bullets on the lighter side so experiment with those and ya kinda get what ya get. I'd try the recipe that Ron provided as a starting point. I've learned all this from experience with a Browning BBR in 7mag. I went and got some of those fancy Berger bullets, actually called and talked to Walt, got the gauge, tried charge weights, overall lengths ad infinitum. Turns out my 7mag has a love affair with Nosler 120g bullets, manual recommended COAL, 63.5g's of IMR4350. Makes one neat little hole with a bullet a lot lighter than I ever wanted to use in the 7mag. I will say however that making those little tiny groups is more satisfying than being able to use that heavier bullet, then I simply added a 300 Win Mag to the collection.

 

[Member 5605]

With proper charge, 2.220" will produce fantastic results and fit in the magazine.

 

[DLS]

That's a great tool you created there, but it does have one problem that the Stoney Point / Hornady tool shown in ron's post does not.

You will get some variable inaccuracy (a few thousands) if you use your bolt to push the case into the chamber UNLESS you remove the ejector. The spring loaded pressure the ejector places on the case is the cause of this variance.

It's a hassle to remove the ejector, and as already stated by ron it's really better to measure from the bullet ogive, so while you are on the right track and made up a really cool device, I'd still recommend you get the comparator tools.

Just my take on this matter. Good luck on load development … to me it's as much fun as actually shooting.