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Thread: Slow barrel? Slow bullets?

  1. #1
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    Slow barrel? Slow bullets?

    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

  2. #2
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    Quote Originally Posted by Jäger View Post
    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...

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    Quote Originally Posted by Bimmer View Post
    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).

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

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    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
    Last edited by Pappabear; 09-02-17 at 19:23.
    "Air Force / Policeman / Fireman / Man of God / Friend of mine / R.I.P. Steve Lamy"

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    Quote Originally Posted by Bimmer View Post
    That's my question: Where are those "estimated" velocities coming from?
    Published data of the powder manufacturers for those bullet weights.

    Quote Originally Posted by Pappabear View Post
    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.

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    I have worked with this specific bullet as well. However I have not worked with the same powders you have. Initially my results were similar to your observations in that velocity seemed s little slow. Two things stood out, that the data I was using was for a vastly different bullet profile, and that the apparent pressures were well below expected. Don't give up on the 62.

    I would urge you to consider trying IMR 8208 XBR or benchmark. That said I would have assumed TAC to have achieved higher velocities.

    The last thought I will leave you with is that there is no surer sign of pressure than velocity. If you aren't getting velocity then your pressures MAY BE less than expected.

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    I'll go ahead and repeat Bimmer's question. What barrel length did the powder manufacturers use to generate their data? If it's from a 24" tube, that'll cover a solid portion of the difference. I'm not familiar with the C7A2, but I bet it's a lot shorter than 24".

    Ejector swipes and cratered primers (to a degree) are indications of excessive pressure in semi-autos.

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    Sorry for not responding sooner; we have some forest fire issues going on here at the moment in Montana that are getting most of my attention.

    Quote Originally Posted by grizzman View Post
    I'll go ahead and repeat Bimmer's question. What barrel length did the powder manufacturers use to generate their data? If it's from a 24" tube, that'll cover a solid portion of the difference. I'm not familiar with the C7A2, but I bet it's a lot shorter than 24".

    Ejector swipes and cratered primers (to a degree) are indications of excessive pressure in semi-autos.
    C7A2, somewhat similar to the M16A3: 20" bbl

    Sierra data: 20" bbl
    Hornady data: 20" bbl
    Western: 24" bbl
    Hogdon: 24" bbl

    Hornady provides data for both .223 developed with a 24" bbl and 5.56 with a 20" bbl. Looking at the same bullet, using the same powder, they show the .223/24" bbl to develop all of 50 fps more velocity than the 5.56/20" barrel. Of course (presumably) they show it as 5.56 data as they're loading to 5.56 pressure limitations as opposed to .223, so that negates some of the 4" in barrel difference. But it's nowhere in the neighborhood of 400 fps.

    I'm aware that test barrels aren't production barrels, and that while some of the load data was in 20" barrels, other data is not. And that each barrel is unique to itself. And that this bullet also creates variables when compared to data for other bullets of similar designs and bullet weight.

    However, we're talking about velocity differences between published velocity and actual velocity of 350 -400 fps. In a .22 caliber bore, generally speaking, I might expect to lose somewhere around 100 fps, depending on powders, yadda yadda, if a 24" barrel were cut back to 20". Not 100 fps for each inch a barrel were shortened.

    So (for example) out of my recent tests, 24.0 gr of BL(C) should produce somewhere around 2750 fps with this bullet; I'm getting 2426 with an ES of 23 and a SD of 8 (and a 1.5" nice round group at 200 yards I'm pretty happy with other than the velocity). At the top end, 26.0 grains should result in something like 2950 fps; I'm getting 2707 fps with an ES of 22 and a SD of 8. The expected velocities differ a little depending on whose data you use for reference, but my chronographed velocities still run 250 - 300 fps slower.

    With CFE223, a maximum published load of 26.4 grains should give something like 3100 fps; I'm getting 2869. An over maximum load of 27.2 grains shows nothing even faintly looking like a pressure sign - but still only 2902 with an ES of 58 fps and an SD of 21.

    I like the bullet enough that I bought a lot of them, and it's showing a lot of promise accuracy wise, but the way low velocities for charge weight is something I've never encountered before. But again, this is the first time I have done load development for a gas gun.

  10. #10
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    Slow barrel? Slow bullets?

    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.
    Last edited by grizzman; 09-11-17 at 12:21.

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