NATO CCI 34 primers and load impact

Warpspasm · Oct 23, 2017

I finally got around to picking up some CCI No. 34 7.62 military primers for use in my MAS 49/56. I know that a change in primers can make a difference in load performance, but this was a bigger difference than I expected. I had a really nice load I used for the 49/56 consisting or Winchester primers and 40gr of I4895 behind a 155gr Hornady 3039 match bullet. It gave me about 1.5" groups at 100 yards. The only factor I changed was switching to the CCI military primers. Now, with that same load it is all over the place. A few will group then the POI will drop and then go up again. Basically, my 1.5" group is now a 10" group. It's kind of weird. When switching to the military is there a "rule of thumb" on how to adjust the other components in a load?

BradMacc82 · Oct 23, 2017

Sounds like a good load, but an unstable load. Ideally, with a truly stable load (not necessarily the most accurate load) - there should minimal downrange effects based on changes to the load - such as primer, COL, or even a tenth or two grain of charge.

Personally, I'd just start a new load based off the #34's if you're going to be switching to those for the foreseeable future. Hell, if nothing else, I'd take those #34's off your hands - as that's what my load is developed with for the .260Rem.

SKIP · Oct 23, 2017

Great. UPS just delivered 2K of CCI #34.

BradMacc82 · Oct 23, 2017

I'll take 'em, gladly.

Warpspasm · Oct 23, 2017

Stop hijacking my thread! LOL

kalister1 · Oct 23, 2017

Why did you switch Primers?
I guess what I am saying is: If it ain't broke, don't fix it.

Warpspasm · Oct 23, 2017

kalister1 said:
Why did you switch Primers?
I guess what I am saying is: If it ain't broke, don't fix it.

The MAS 49/56 is VERY prone to slam fires. With regular commercial primers I usually get a double shot every 20 or 30 rounds. Not a good thing. The firing pin channel is clean and dry.

kalister1 · Oct 23, 2017

That is a good enough reason for me! Sorry, no help, never used them.

Warpspasm · Oct 23, 2017

kalister1 said:
That is a good enough reason for me! Sorry, no help, never used them.

Yeah, it's not fun when it's not intentional.

K-43 · Oct 23, 2017

CCI says to use Magnum primer data and says the "Initiator mix optimized for ball/spherical propellants". So yes, you need to rework your loads. And yes, I know there probably isn't any "magnum primer" data for your round, but that shouldn't be a problem since you have to work up anyway.
I used them for Garands for years, then switched to Wolf when CCI were scarce. The sensitivity seems to be the same, but the Wolf seem milder to me.
http://www.cci-ammunition.com/products/primers/primers.aspx?id=30

Magnumite · Oct 23, 2017

A couple things. BradMaac mentioned the load possibly being unstable with the single change causing great deviations from past performance. I agree there. A chrono would really help in load development.

Additionally, I load so that accuracy and POI doesn't change significantly which small changes in load charge weight nor component selection (saving defective or unstable bullets). Example, a load I used in a 30-30 Contender I had was stable with credible accuracy throughout a range of about 3.5 grains of powder. There was a sweet spot but changes in primers didn't effect overall load performance.

Warpspasm · Oct 23, 2017

So, what makes a load unstable?

quickdraw17 · Oct 24, 2017

Interesting. I used 34s to work up a 308 load (when I couldn't find any other large primers) and wasn't too impressed. I decided to use them to try and develop a hunting load for my 300 WM. Found a load that grouped 3/8", which greatly exceeded my expectations. Might be worth changing powders/charge weight to see if that helps.

BradMacc82 · Oct 24, 2017

Warpspasm said:
So, what makes a load unstable?

An unstable load may show good (even great) accuracy, but is not tolerant to small deviations in the load itself - such as COAL variations, charge weight variations, brand of primer being used - even temperature swings, to an extent.

Ed Shell would likely be able to give a better description than I could, as the man has forgotten more than I know when it comes to this stuff.

Using my .260 as an example, I load 43.3gr H4350 with a #34 primer to a COL of 2.815", with a variety of brass from diff't makers. It's a very stable load, although not the tightest grouping load. I can swap brands of primers, have a variation of up to .3gr of charge, COL can vary from 2.810" to 2.817" and the effects downrange on the target are minimal.

K31 · Oct 24, 2017

Warpspasm said:
I finally got around to picking up some CCI No. 34 7.62 military primers for use in my MAS 49/56. I know that a change in primers can make a difference in load performance, but this was a bigger difference than I expected. I had a really nice load I used for the 49/56 consisting or Winchester primers and 40gr of I4895 behind a 155gr Hornady 3039 match bullet. It gave me about 1.5" groups at 100 yards. The only factor I changed was switching to the CCI military primers. Now, with that same load it is all over the place. A few will group then the POI will drop and then go up again. Basically, my 1.5" group is now a 10" group. It's kind of weird. When switching to the military is there a "rule of thumb" on how to adjust the other components in a load?

"Rule of thumb" is that any time you change a component you begin from the minimum load and work up again. Changing primers can change the velocity as much as 7% (in tests done by Hodgdon).

jimbobborg · Oct 24, 2017

Do you have a chronograph? I'd suggest you get one and test the old load and the new load. That'll give you a better idea of what's going on. And you should have one anyway.

Magnumite · Oct 24, 2017

I have experienced a decrease in velocity going from standard to magnum primers with a ball powder. Chatting with a couple others they said they experienced the same thing on occasion. I do know the deviations were smaller.

Warpspasm · Oct 24, 2017

jimbobborg said:
Do you have a chronograph? I'd suggest you get one and test the old load and the new load. That'll give you a better idea of what's going on. And you should have one anyway.

Yep. I have one. I won't get a chance to fool with it until next week though.

Pinecone · Oct 24, 2017

Warpspasm said:
So, what makes a load unstable?

http://optimalchargeweight.embarqspace.com/

And if you really want to get into the physics, look up Optimal Barrel Time.

Melnic · Oct 25, 2017

I second the OCW method. For the loads I've used it, its made for loads that can deal with variations I may put into the batch. This is only for the guns I've really wanted to spend time on tweeking the accuracy. Much of my reloading, I'm just doing milsurp calibers for the fun of it.

I"m no wise old expert but going from 1.5" to 10" with just a primer change does not sound right though. If you have a good bullet, you should not vary that much unless there is something Really inconsistent about what you are doing or how you are shooting.

Scoped? something loose?

NATO CCI 34 primers and load impact

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