Range Day and 165 Grain Work-Up

[Pr589]

So I managed to make it our to the range for a nice day of shooting with the intention of finding out what 165 grain load works best in my M305.

Beautiful day...sunny, 26 degrees and by the time I got to the range, most folks had already left. To start, I ran through a box of Hornady 150 grain SSTs over 41.5 grains of IMR 4895. A lighter load (40.5 grains) has been shooting well for me but I've seen powder marks half-way down some cases. I thought this might indicate too-light a load, failing to fully expand the neck and allowing gas blow-back - so up to a hotter load as an experiment. Anyway, it showed acceptable grouping of 2.2" over 50 rounds but had my first experience with a case head separation with the once-fired Federal brass. This is weird since the load is well below max and I am up to 6 firings on Hornady brass, with no stretch marks or loose primer pockets.
Although I am still having difficulty adjusting for first round flyers, in between a 1.5" and 2.9" group snuck in this little nugget - my best to date.



So on to the ladder test using cheap 165 grain Hornady Interbond over IMR4895, in CBC brass/primers. I had started at 39.5 grains, adding 0.5 grain increments in batches of 15-20 rounds each (i.e. enough for 3-4, 5-round groups at each loading) and stopping at a conservative 41.5 grains (reloading books show such a huge variation in max loads). First round flyers are a huge pain as I was holding POA constant to see if the load would help with flyers, which it does not.

See my results below. These aren't statistically significant due to the small samples but what is interesting is that the rifle seems to have a negative accuracy node at 40.5 grains - hates it for some reason and many others claim great results at this loading. I think I'm going to try some heavier loads since the brass is still showing no pressure signs and the rifle is functioning perfectly.




I think its interesting that I'm getting the best accuracy from lighter loads with both 150-ish grain bullets and with the 165's. Flyers are still the bane of my existence and while the worst flyers seem to have been culled by warming up the barrel with a string of Norinco before shooting for effect, I still get inconsistent groupings. Mediocre 2-3 inch groups often are tight 4-round packets and one flyer.

These groups are from the 39.5 grain series.

 

[45ACPKING]

Good post, thanx for sharing.
The infamous M14 flier, pretty common.
2-3 inch groups put your rifle within the passing grade for an NM rifle.
Try a 10 shot group with your "best" load, although this is better done without a mag change. This is where it's handy to have one of them 10 round AIA mags hehehe
2-3" groups from your favorite bolt gun would be considered mediocre. 2 to 3" groups, consistantly from an M14/M1A is respectable

 

[Pr589]

Hey Thomas - Consistency is the challenge. So do ya think that a unitized gas cylinder would help with the flyers, or tighten groups further?

 

[AbHobbyist]

Pr589

A most excellent post!!

If I may make a suggestion, and you may already been doing this.

I have been talking to some very experienced shooters.

They suggested to me, and have demonstrated that with bolt guns, when you change powders the change in fouling can be detrimental to accuracy.

A recent experiment demonstrated that a change in powder, (which changes the fouling inside the barrel) can and most times will increase group size by as much as 0.75-1 moa from the resulting flier(s).

It was suggested that on a powder change (or in this case an ammo change), the first 3 rounds should be put into the berm, and then resume group testing.

As the M-14 design seems to get its best accuracy when the harmonics of the system are fluid an even, I could see that the change in fouling might change the harmonics.

It would be interesting to see if this technique might help with some of your flyers.

Just food for thought.

regards

AbH

 

[Pr589]

Ab

I was intrigued by your suggestion since as I mentioned I'm using Norc ammo to effectively do the "3-rounds into the berm" exercise however I haven't given much credence to the powder fouling issue in guns like the M305. So as an analytical kinda guy I took a look at the range days since I started doing the warm-up routine to see if there was much change from the 2nd group to the 3rd, etc. Now this isn't the best sample since it includes groups where I am doing a ladder (keeping POA constant) and others where I am adjusting for first round flyers....but what the heck.

See the results below. I overlaid the number of rounds fired in groups so that you could see how much data was used.



On the surface I'd say that the fouling effect was negligible (but again the data isn't the best). What might be interesting is that I think I get tired after shooting more than 9 groups in sequence

Next time out, I'll try 1 group Norc, followed by 2 groups of handloads in a few repetitions to see what happens.

Thanks for suggesting an interesting experiment.

I'm also anxious to see how adjustments of the Blackfeather tension screw affect groups - now that I have what seems like a dynamite load. Seems to me that the barrel tension from the BF screw is similar to what some talk about regarding front hand-guard tension, which I have seen recommended to be adjusted to 5 -10 pounds for best accuracy.