Slow barrel? Slow bullets?

[Jäger]

Hi... been here a while and lurked much longer. New to AR-15 reloading (taxpayer took care of both providing the rifle and the ammunition for the last 30 years, thank you very much), but not reloading. Been reloading for 30 years for everything from varmint rifles to handguns for competition. No reloading experience for semiautomatic rifles, however - everything I owned up until now in the rifle category is bolt action.

Minimal details are: I have a new AR-15 from Colt Canada, essentially a clone of the C7A2 service rifle they make for the Canadian military, minus the go-fast parts. True mil-spec (for better or worse) from the same parts bin they build rifles for the Canadians, Brits, Dutch, etc. Specific to my question, the barrel is one of Colt Canada's hammer forged chrome plated barrels.

So I bought a bunch of the Hornady 62 gr. bullets Midsouth is selling, 4,500 to be exact. I'm not expecting great accuracy from a milspec barrel with anything. But potential is there: I'm getting 2.5" 10 shot groups at 200 yards at 2950 fps with Sierra 52 gr. HP Match bullets (no load development, just tested with a load Wally Hart used to suggest to test a .223 Remington).


Anyways, the immediate question concerning this Hornady 62 gr. bullet is this: The velocities I am getting with this bullet are VERY low for what expected velocities are for similar powder charges for similar bullet weights. I understand manufacturer test barrels are different, using data for different bullets, no two barrels are the same, yadda, yadda, yadda. But these seem REALLY slow, and diameters of the bullets mic out to being at spec. Checked my chronograph with other rifles using loads of known velocity. Spot on; not the chronograph.

So while I continue looking for a load that will give me reasonable velocity along with reasonable accuracy, any input on these slow velocities and where to go from here? I'm going to tiptoe past the max charges I've loaded up to with these powders to date, but I'm a complete novice at detecting the onset of excessive pressures in a semiautomatic rifle. Little screenshot attached of the spreadsheet I've recorded the initial results in, giving the data so far with these bullets.

Thanks for comments and suggestions.

data.jpg

[Bimmer]

The velocities I am getting with this bullet are VERY low for what expected velocities are for similar powder charges for similar bullet weights...

Shot in the dark:

How slow? 50fps would be no big deal. 200fps would be significant.

Are you looking at published data? A lot of those are from 24" barrels...

[Jäger]

Shot in the dark:

How slow? 50fps would be no big deal. 200fps would be significant.

Are you looking at published data? A lot of those are from 24" barrels...

As per the attached data in the OP, in the case of CFE 223 Varget and TAC, 300 fps... (also aware the CCI primer s/b 450, not 400).

[Bimmer]

That's my question: Where are those "estimated" velocities coming from?

[Pappabear]

Every bullet and brass and primer combo create its own rules. If you want more velocity, push up your powder charge. Some bullets have flat bases others not. Every little thing changes pressure / outcomes.
Even every lot of powder can differ...
If no signs of pressure, push up powder slowly and safely.

Sounds like accuracy is spot on, well done.

Good luck.

PB

[Jäger]

That's my question: Where are those "estimated" velocities coming from?

Published data of the powder manufacturers for those bullet weights.

Every bullet and brass and primer combo create its own rules. If you want more velocity, push up your powder charge. Some bullets have flat bases others not. Every little thing changes pressure / outcomes.
Even every lot of powder can differ...
If no signs of pressure, push up powder slowly and safely.

Sounds like accuracy is spot on, well done.

Accuracy of some does look worth investigating further. Aware of variations due to different combos, powder, primers, lots, etc But although I'm not obsessed with velocity, 300+ fps is a lot to leave laying on the table. Particularly with a relatively light bullet over distance.

[grizzman]

A 20" barrel length definitely wouldn't be the cause of that much velocity reduction.

Have you contacted Colt Canada yet? I don't consider this normal at all.

[Jäger]

A 20" barrel length definitely wouldn't be the cause of that much velocity reduction.

Have you contacted Colt Canada yet? I don't consider this normal at all.

Nope, not yet. If I end up with a load with reasonable accuracy at reasonable velocities, I probably won't bother. Haven't done much shooting with other bullets to see if the same situation occurs as well. If it's only this one bullet and results match published data more closely with other bullets, then it's not the chamber/bore. Before I call anyone, I'll have my gunsmith buddy borescope the barrel to see if there's anything unusual to see, and do a Cerrosafe casting of the bore and chamber.

[opngrnd]

Find a way to double check your powder scale. I has this issue once.

[Jäger]

Already checked that out while I was checking out the chronograph as well, thanks.