Can't get AA#9 to slow down

Discussion in '10mm Reloading Forum' started by Mountain10mm, Aug 13, 2018.

  1. Mountain10mm

    Mountain10mm

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    I thought 38 years of reloading was extensive, but I have way more to learn and need some help. I'm loading 10mm with #9, 200gr. XTP's, CCI300 primers, and new Starline brass (plain brass, not nickel plated). Firearm is a G20 with a Jarvis 5.5" barrel. My goal is a 1200fps +/- with the 200gr. XTP. (No matter what I do what the G20 or magazines in terms of springs, I get FTF's with hotter ammo - the slide speed is too fast and rides over the next round in the mag. Issue for another time.)

    So the reloading issue...
    With 12.3 grains of #9 I get velocities of 1260fps. With 11.6 grains I get velocities of 1233fps. Two issues with this. First the velocities are higher, for the given amount of powder, than everyone is getting (from the oh-so-trusted internet). Second, I'm getting very little change in velocity, given the significantly reduced (IMO) powder charge. Accurate's load data shows 11.3 grains should give 1030fps with a 200gr. XTP. I'm at 11.6 getting 1233fps??????

    I know my taper crimp is tight as feeding issues happen if the cartridge mouth's edge isn't snugged up against the bullet. Press is a Dillon 650.

    For comparison, Double Tap's 200grain JHP comes out at 1190+/- in the same barrel, so I know the barrel chamber isn't overly tight. I've been shooting this barrel for about 10 years, it's not the barrel.

    Chrono was checked with a known rounds and it is reading accurately. Powder is checked with a calibrated scale for load development - charges are accurate.

    Any thoughts???
    Thanks.
     
  2. Kwesi

    Kwesi

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    Wish I could help. I can share my data and hopefully Taterhead will be along to share. My LabRadar results:

    13.0 AA9
    200 XTP
    Win LPP
    Mixed SL ( not virgin )
    1.257-1.262
    KKM barrel
    Ave 1,215

    One thought: virgin brass has better neck tension. My Win LP run hotter than CCI 300.
     

  3. gjarcher

    gjarcher Captain USN ret.

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    Your load with AA9 is commensurate with my load using 200gr HDY XTP and Starline brass w/ CCI300 primers. With a 7" KKM Barrel, I get nearly the same muzzle velocity corrected at 45fps/inch of barrel. FWIW, I found that either WLP or CCI350 primers produced better and more consistent velocity, although the CCI 350 primer is 15fps faster than the CCI300

    Concerning your failure to feed issue, I think you've answered your own problem ... RSA spring is too weak for the power factor. Slide slams back too fast, slide fails to return to battery too slow.
    You didn't explain what RSA spring values you used, but my suggestion would be to use at least 22# and possibly 24#. I'm using a DPM 3-spring RSA to good effect, 12.8gr AA9,200gr HDY XTP, CCI350/WLP, 7" KKM barrel @ 1302 fps ... that'd be about 1232 fps out of your 5.5" barrel.
     
  4. Taterhead

    Taterhead

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    EDIT Due to more carful reading of the OP:

    The readings do seem high.

    My stock 4.6 barrel gets a nice round 1200 fps (give/take depending on ambient temps) at 13.0 gr under a 200 gr XTP. 11.6 is 1025 to 1050. Chrony errors? Scale setup errors?

    End EDIT:

    Regarding the slide-over misfeeds. I experienced that exact issue too. I'm a bit of a contrarian when it comes to recoil spring assemblies. Going lighter actually corrected the problem for me. A lot of guys on here are far more knowledgeable than me with the mechanics of firearms, but this is what I think is happening:

    I don't think the velocity of the rearward slide travel matters as much as some argue. The next-in-line cartridge cannot begin its upward travel until the slide clears. The critical timing issue, I think, is the amount of rearward dwell time, and then the forward slide return velocity. Too little dwell, and too quick return = next round can't get in position soon enough. Going from my 22 pounder to a 17 pound RSA cured all, and I mean ALL issues. The problem with a heavier RSA (again, this is how I understand it) is that it reduces rearward dwell time and increases the forward slide return velocity.

    If I had to guess, the issue is greatest with a full mag? More weight for the mag spring to lift.

    Another thing to look for, or to have a buddy observe, is that these heavy loads impart a lot of twist from the torque. If you remove the slide and insert a loaded mag. Yank on the slide and mag plate, as if recoiling and twisting. See how far out-of-alignment the mag and cartridge can get by tugging on the mag base plate. Mindfulness of this is useful in the grip so that left handed pinky doesn't pull on the base plate.
     
    Last edited: Aug 18, 2018
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  5. Mountain10mm

    Mountain10mm

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    Taterhead, thanks for the input. Still seems like my velocity is high - probably a problem most people wish they had. I just want it to be safe; however, there are no signs of high pressure, as in no smileys, flattened primers or even black streaks on the brass. I'm going to just keep downloading it until I end up at 1200fps. I might try a single stage press too and see if a different set of expanding/taper crimp dies has any effect. The only thing I can think of is that the brass has an overly tight grip on the bullet creating slightly higher pressures, which is resulting in higher velocities.

    Was hoping to make a super light target load too with a 200gr. FMJ at 900-1000fps. The way AA#9 is going, I might have to switch powders for that.
     
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  6. WeeWilly

    WeeWilly

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    Your velocities do seem very high to me, although all my #9 results are with the stock G20.

    I would definitely switch powders if you want 900-1000fps, something faster for sure.
     
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  7. Duke45Big

    Duke45Big All anti-gunner stink worse than filled diapers.

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    As stated above check your recoil spring sounds to light for your loads.
     
  8. gjarcher

    gjarcher Captain USN ret.

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    I went back through my Reloading Log when I was first working up 200gr HDY XTP in the G40 OEM 6" barrel, RCBS 40/10mm dies, Starline Brass, WLP primer,Taper crimp .421", COAL 1.260", Pro Chrono @ 10':
    12.4gr AA9 = 1206 avg (1223 fps est. muzzle velocity)
    Corrected for a 5.5" barrel, estimated muzzle velocity would be about 1200 fps. So your chrono results do seem higher than normal.

    All other things equal, I'd recommend focusing on the tighter than normal taper crimp, which could account for the higher pressures/velocities ... and may also be a source of poor accuracy.

    FWIW, a source of 'discomfort' is the great disparity between Hornady and Accurate Maximum Load Data for AA9 and the 200gr XTP bullet; (13.2gr vs. 12.5gr respectively)... I don't put much faith in either one, trusting more to caution by starting below minimum load, and measuring case head expansion, case bulge, and primer appearance when compared to chronograph readings. Also, the XTP is a long, jacketed bullet which often results in compressed loads ... I've always had strange results with compressed loads, and the more compression, the stranger the results; I try to avoid compressed loads whenever if I can.
     
    Last edited: Aug 17, 2018
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  9. Taterhead

    Taterhead

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    With a little carbon on the brass on the second firing, I've found that velocities drop. When I go full-tilt with 10mm, I start with new Starline cases, then relegate those once-fired gems to the range/reloading assortment. Everything about new Starline brass is "sticky". In fact, I think there is a memo from Dillon somewhere that explains what to do about expanders sticking in new cases. Bullet pull for days, and that agrees with No. 9.

    I'd highly recommend the baby brother of No. 9: Accurate No. 7, if you want to go 900-1000 fps. It has the similar properties of fantastic metering, low flash, and clean burning. No. 9 will get there too on the very low end, but No. 7 will be more efficient. I also really like WSF for modest velocity 10mm loads.
     
    Last edited: Aug 18, 2018
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  10. Taterhead

    Taterhead

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    I did not carefully enough read the original post, so I'm revising my initial post above.
     
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  11. Taterhead

    Taterhead

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    I more carefully read the OP, and I agree with you Willy. Post is revised above.
     
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  12. agent clark

    agent clark

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    [QUOTE="gjarcher, post: I'm using a DPM 3-spring RSA to good effect, 12.8gr AA9,200gr HDY XTP, CCI350/WLP, 7" KKM barrel @ 1302 fps ... that'd be about 1232 fps out of your 5.5" barrel.[/QUOTE]

    GJ, how do you have your triple spring set up? I got one recently and left the standard recoil spring, but put the mid-sized bushing on. It seemed to shoot like stock the one time I've shot it since, with Sig ammo. My goal was to ramp it up a bit to not toss brass when I load it hot.
     
  13. usnret

    usnret

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    Long Shot os also a good 10mm powder.
     
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  14. gjarcher

    gjarcher Captain USN ret.

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    I use the heaviest spring with the largest bushing. I only use the DPM RSA with the 7" KKM barrel and loads with PF>250; ie, 200gr HDY XTP @ 1300+ fps or 190gr CEB Solid @ 1300+ fps.

    I've found the DPM RSA does little for me when shooting lighter loads, other than not throwing the brass as far; ie 150gr~165gr @ 1200 fps. Consequently, I use the OEM RSA with the OEM 6" barrel for target/SD ... I don't shoot competition, so those that do might have better insight to the effectiveness of the DPM RSA and how to set it up for lighter loads.

    ... don't want to get too far off OP's topic.
     
  15. alank2

    alank2

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    AA#9 is a slow burning powder and the Lee manual shows the starting charge for 200gr jacketed at 12.2gr and the 200gr XTP at 11.3gr. Both of these at 1.250 OAL. Do you have the list of velocities from the string? Are they consistent or jumping around wildly? Be careful with slower powders and lighter loads, they often don't burn consistently. I'd recommend switching to a faster powder like AA#7 perhaps.