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    • #24180
      Clear Cut
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      I want to run some low velocity rounds in my AR yet I wand it to cycle I have on order a mold, sizer ,gas checks and a buffer spring.The issue is the 1:7 twist bbl. that makes me think I should keep the MV at a low speed so as to not strip the bullet (62 grn PC’d GC’d coww).I was thinking about stretching the buffer spring and then cutting it until it performed the required task of cycling a round at some where in the 1,300 fps. OK I’m just putting it out there. Any comments ?
      Thanks CC

    • #24210
      IllinoisCoyoteHunter
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      What length gas system are you running?

    • #24216
      Anonymous
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      Clear Cut;n2326 wrote: I want to run some low velocity rounds in my AR yet I wand it to cycle I have on order a mold, sizer ,gas checks and a buffer spring.The issue is the 1:7 twist bbl. that makes me think I should keep the MV at a low speed so as to not strip the bullet (62 grn PC’d GC’d coww).I was thinking about stretching the buffer spring and then cutting it until it performed the required task of cycling a round at some where in the 1,300 fps. OK I’m just putting it out there. Any comments ?
      Thanks CC

      Do not modify parts

      One of the things I did when i built my upper / before i built it I modified the feed ramps –just a bit
      I used a pc of brass and if feed ramps were sharpe enough to scrape brass I polished edge till it did not take chunks out when you rub / turn brass on feed ramps

      You should with a bit of reading be able to full cycle cast bullets with a GC in a AR with out modifying parts
      You might have to do some reading (at the old place)
      it also depends on your barrel twist –1/7 soso / 1/9 better / 1/12 best –> rpm
      bullet weight
      read about dacron filler some powder needs it some don/t

      I built a new 223 upper 1/12 x 20 inch and with the right powder / bullet/ plus dacron was able to get full function in my first low powered / low velocity test in my first 50 rounds

    • #24218
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      I know just about enough about the AR platform to be really dangerous. It is designed as a fully balanced system. Change that balance between the gas volume /pressure ,reciprocating mass an springs and it stops working. .
      My suggestion is with the 1/7 twist is to shoot what it was intended to shoot . Stay with me . The twist is more suited to I think I read something about an 82 gr bullet. So I would try to find a cast bullet in that area of weight with cast and this just sounds stupid to type but upwards of 90 gr . Your speeds should be down around what you want and you should be in the pressure range needed to work in the system.

      The other approach is to use slow powders to hit the velocity numbers while keeping the pressures up/down . The 223/556 surprised me in a new AR in that a 22-55 NOE version at 62 gr hit 2200 fps with start loads and was reasonably accurate, as good as El cheapo fmj,with the 1/8 twist. I think 10x,and 4895 might be your best bets , 4198 did strange things but H322 worked well also.

    • #24260
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      I have a carbine gas system.I am not modifying the AR just a spring that I bought just for this reason ,I just think with a little modification It may work.The AR is the tinker toy of fire arms.I’m stuck with the 1:7 bbl. for now the 300BO is on hold till after taxes.

      CC

    • #24289
      IllinoisCoyoteHunter
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      I agree on not modifying anything on the rifle, even if it is a spring. This should be your last ditch effort.

      What powders do you have available? The one problem I ran into when running reduced loads in the ar was unburnt powder. I will have to look at my notes next time I am down in the shop. IIRC I used RL15 with a 62 grain cast bullet. I never really experimented with pistol powders, so I can’t give much advice there. With the carbine length gas system you will want to have sufficient pressure to cycle the rifle when the bullet is going past the gas port in the barrel. So, in your case, a powder that burns a bit faster and has a pressure peak faster may give good results.

    • #24332
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      There is a guy building a DI 45 ACP upper for ARs with a pistol length gas port. 8t can be done . A 16″ carbine gas may not be as hard to get where you want to go. Slower powder I think will leave you over gassed.

    • #24333
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      My parts should come in today so I may be able to start casting tomorrow.I’ll keep posting, more comments welcome.
      Thanks CC

    • #24334
      Phil
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      My results: 62 gr cast GC and 19 gr 4895 works well in both my 1:8 carbine and rifle. Accuracy is 1 MOA at 100 yds out of scoped rifle with occasional fliers. There were no mods to the ARs. I have no velocity numbers but are likely well above your desired 1300 FPS. I would guess more like 1900 FPS.

    • #24415
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      Well I picked up some IMR 4895 last night ,the CK’s and sizer came today. I’m still waiting for the mold.Phil I may have to go a little slower in my 1:7 bbl. to get the accuracy I want.
      CC

    • #25025
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      OK so the 62 grn fn NOE mold with coww h2o dropped PC’d GC’d come in at 68grn. I did a ladder test (started at 17 grns.) and the best group was 7/16″ bug hole at 25 yds on a rest with 21 grn’s of IMR 4895. I never had to change the springs to get cycling and the accuracy I was hoping for. I’ll do a 1/2 grn test next. After that I will stretch it out to 76 yds. (the longest range at the house) to see what it will do.

      CC

    • #25177
      Phil
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      Clear Cut;n3325 wrote: OK so the 62 grn fn NOE mold with coww h2o dropped PC’d GC’d come in at 68grn. I did a ladder test (started at 17 grns.) and the best group was 7/16″ bug hole at 25 yds on a rest with 21 grn’s of IMR 4895. I never had to change the springs to get cycling and the accuracy I was hoping for. I’ll do a 1/2 grn test next. After that I will stretch it out to 76 yds. (the longest range at the house) to see what it will do.

      CC

      Any idea of velocity for that load? My load is the same but no PC and a couple grains less 4895. I do not know the velocity, need to chrono sometime. Here is a 10 shot 100 yard target. I called the two flyers.

    • #25260
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      Nice shooting. I have no ideal what the speed is but I think it’s well over 2000 fps. work is keeping me from testing my new loads.

      CC

    • #25282
      Goodsteel
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      Bravo! Thank you for posting.
      (that’s a mighty slick looking bullet. May I ask what alloy?)

    • #25296
      Phil
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      Those were cast with pure lino. I have since cast with COWW/Lino in 50/50 and 25/75 mixtures. The 25% COWW and 75% Lino seems the best in terms of very good bullet fillout on these little critters and enough shrinkage for good release from the mold.

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