perzentkar 0 Posted October 14, 2013 Report Share Posted October 14, 2013 I'm new an haven't found my way around yet. I want to buy a 5.45 barrel blank but it is unturned and I have a lathe. What do I need to do in order to finish this rifle barrel into a mountable barrel? I was told something about tapering and crowning and such but I guess I am looking for the steps and what they involve. Any help is greatly appreciated. Quote Link to post Share on other sites
Sdustin 578 Posted October 14, 2013 Report Share Posted October 14, 2013 What kind of rifle are you building? Cause a true blank will need the chamber end machined to fit your receiver, then turned to the correct outer diameter and if it's semi auto a gas port drilled, then crowned and a chamber cut. The tools to do this are very expensive, like fund a life time of gun buys. But if you have access to the tools and know someone that knows what they are doing its not impossible just cost prohibitive. Quote Link to post Share on other sites
perzentkar 0 Posted October 14, 2013 Author Report Share Posted October 14, 2013 This is a barrel blank for a 5.45 with a 1 in 7 twist, i need it turned to fit an AR upper receiver, and the barrel itself is 1" in diameter overall, I was actually thinking about maybe doing this particular gun as being blowback operated. and milling out part of the upper to put a charging handle on the left side of the receiver versus the standard ar charging handle. Thoughts please? Quote Link to post Share on other sites
TonyRumore 1,332 Posted October 14, 2013 Report Share Posted October 14, 2013 I don't think blowback would work. The bolt/carrier would move rearward while there was still too much pressure and blow the case out. You need a barrel extension (locking lug piece), DPMS part number BL-17. Thread the chamber end 13/16-16 and install the extension with about .006" clearance between the bolt face and the barrel chamber face. Cut the chamber using a reamer and set the headspace at about .001" - .002" off the go-gauge. Contour the exterior as desired. Your most common gas block diameters are .935", .750", and .625" so you will need to pick one of those for the diameter at the gas block/port position. Drill a .063" gas port hole and test fire with one round in the magazine. If the bolt does not lock back, drill it a bit larger. Keep doing so, until the bolt locks back. Tony Quote Link to post Share on other sites
Sim_Player 1,939 Posted October 15, 2013 Report Share Posted October 15, 2013 (edited) It warms my heart to see someone willing to take up a challenge. It keeps the hobby alive. I am certainly no authority but, Tony's advise is very sound. I'm going to be building a small shop space in the near future. A press and a lathe are at the top of the list, of tools to acquire. Cutting the crown and polishing appear to require minimal tooling. Good luck! Edited October 15, 2013 by Sim_Player Quote Link to post Share on other sites
perzentkar 0 Posted October 15, 2013 Author Report Share Posted October 15, 2013 (edited) I have no idea how to install the barrel extension and do it right. Then does that fit the upper for an Ar receiver for 5.56? I just did some research and it looks like I can definitely do this if I use the machining equipment here at college. Can I do this by means of hand threading at all? Should I secure the Barrel extension onto the barrel with blue or red loctite? Could you please explain what you mean by threading the chamber end and such? Edited October 15, 2013 by perzentkar Quote Link to post Share on other sites
JoeAK 337 Posted October 18, 2013 Report Share Posted October 18, 2013 Personally, I'd do single point threading on the barrel where possible, since you mention college, make sure you practice it a few times first. I don't know much at all about ARs, but based on the size of the thread, I'd say it's where the barrel screws into the receiver. Quote Link to post Share on other sites
Sdustin 578 Posted October 18, 2013 Report Share Posted October 18, 2013 No theres a barrel extension that attaches to the chamber and the whole assembly slips in the receiver and is held in with the barrel nut. If I was the OP and was dead set on a 545 ar id just buy a barrel with the extension already there. Then I would buy a bolt action and make a 545 bolt gun with the blank. That would be much easier for a first build. Quote Link to post Share on other sites
JoeAK 337 Posted October 18, 2013 Report Share Posted October 18, 2013 (edited) Definitely, I wouldn't pick a picky gun to build my first parts for. Though I did make myself a nice gas puck for my S-12, and way too many muzzle brakes for my 7.62x39. (ETA: which is where I got that nice muzzle flash in the picture below, that was the first one I made) Edited October 19, 2013 by JoeAK Quote Link to post Share on other sites
Sdustin 578 Posted October 18, 2013 Report Share Posted October 18, 2013 JoeAk could you make a slant brake scaled up slightly and threaded 5-8x24 for my saiga 308? Quote Link to post Share on other sites
JoeAK 337 Posted October 19, 2013 Report Share Posted October 19, 2013 Possibly, I'd have to see if I can get some more 4140 from my friend, and see about a tap for that size. Quote Link to post Share on other sites
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