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Post by HMC710 on Jul 9, 2013 13:46:07 GMT -5
Yes, the more powerful the load the farther fwd the shoulder gets pushed. Duplicated my "soft first shot" issue last night. Buffer wgts don't appear to be the issue. Checking to see if the bullets are getting pushed in farther during chambering there by increasing pressures. More to follow
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Post by HMC710 on Jul 15, 2013 8:25:59 GMT -5
WARNING: IT IS NOT RECOMMENDED TO RUN HIGH PRESSURE ROUNDS IN BLOW BACK OPERATION - CASE HEAD SEPARATION AND DAMAGE TO YOU AND YOUR RIFLE ARE HIGHLY PROBABLE. Ran some rounds through the 22 Reed Express blow back this weekend using the new 17R Buffer. After the Max and Super Max, I'm running out of adjectives as I keep adding weight to these things so I figured I would change before I go Plaid Had the soft first shot phenomenon on the first string again as the case dropped about 2' from me. Next two rounds recoiled harder and the cases ejected in the 4:00 position about 10' away. I didn't see them eject so I don't know if they hit the wall and bounced back or not, but I don't think so. A couple of the shoulders were mildly pushed forward but less than before. With the H3 and Super Max Buffer the cases ejected to the 1:00 position so that told me they hit the case deflector and bounced forward. The cases at 4:00 tell me the HMLR system is helping increase the "lock time" and slow down the bolt speed but still not to the point it matches a DI system. I ran a few more strings and did not get the soft first shot phenomenon again so next time I will try cleaning things up between strings and see what happens. I am tempted to do another barrel and see if I can get the chamber a bit tighter but that might increase the case head separation issue. As a note, these loads would not eject from the 1911 clone. I need to do a weight comparison between these to get a reference. Then I tried one of my heavy loads and had case head separation. The dust cover was bent and have some stress marks by the Bolt Catch. This is definitely an accident waiting to happen so as much as I want this to work reliably I don't think the liability is worth it. The load I am running with 6.3 gr of Herco puts me around 2500 fps but we got close to 3000 fps out of the gas gun. Human nature tells me that if its available someone with push it and end up with case head separation and trouble. I've done it twice already so maybe its time to put this one on the shelf..... If anyone has a 5.7x28 I would be curious to know what the buffer and carrier weigh.
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Post by 22boomer on Jul 15, 2013 15:28:19 GMT -5
Go to this location for a look; www.57center.com/6m8/parts-accessories.htmlSpecs listed for standard semi-auto buffer is 16oz. ($37) specs listed for standard semi-auto bolt is 16oz. The total weight for the full auto bolt and buffer is 2.30 pounds.
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Post by HMC710 on Jul 15, 2013 16:48:17 GMT -5
Thanks bud! My buffer is 17 ounces. I'll weigh up the bolt assembly when I get home. Comparing the two rounds, the 5.7 has a base of .303" and capacity of 12gr H2O. The RE base is .392" with a capacity of 16.1 gr H2O. Even tho the 5.7 is rated for 50 ksi vs the RE with 35ksi, they both show equal recoil values in QL (if that means anything). I am thinking the real world recoil is a function of the base dia * psi vs bullet dia and the 5.7 would show less recoil. Doing the simple math for FxA = 3605 lbs for the 5.7 and 4245 lbs for the 22 RE. Looks like its time for my last trick......
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Post by 22boomer on Jul 15, 2013 18:37:52 GMT -5
Thanks bud! My buffer is 17 ounces. I'll weigh up the bolt assembly when I get home. Comparing the two rounds, the 5.7 has a base of .303" and capacity of 12gr H2O. The RE base is .392" with a capacity of 16.1 gr H2O. Even tho the 5.7 is rated for 50 ksi vs the RE with 35ksi, they both show equal recoil values in QL (if that means anything). I am thinking the real world recoil is a function of the base dia * psi vs bullet dia and the 5.7 would show less recoil. Doing the simple math for FxA = 3605 lbs for the 5.7 and 4245 lbs for the 22 RE. Looks like its time for my last trick...... I'm just stating what I've found when shooting both the 22RE and 5.7FN round. The 22RE, like the 7.62X25 was limited actually by the pistol it was designed for. I got loads from Accurate Powders to cover both the pistol strength and for the DI AR-15. For the 22RE the Starline is someplace between the pistol and AR pressure limits. With the 5.7X28, I've seen a pressure limit of something like 50,000psi for the brass but the pistol is actually limited to something like 37,000psi and I believe the FN brass is actually someplace in between. If I load the 5.7FN brass up to a good level for my AR the primer pockets last maybe three reloads. If I load the 22RE Seller&Bellott brass hot with a 30gr bullet it will last a long long time -- the same load in the Starline brass seems to last 5 or 6 reloads before the primer pockets get loose. Now, I'm talking a locked breach AR-15 for both the cartridges. I know that the 5.7X28 case is long and is almost straight sided and may lock for an instant in the chamber but the 22RE has a fair amount of taper as I believe you found out. I still don't understand that business with the first shot in the BB being soft recoil and the second and third being hard recoil. Have you tried loading the magazine with the three rounds and firing the first round and then stopping and ejecting the second round to see if the cartridge case is damaged or the bullet pushed in? I know this may all be a moot point now since you decided the 22RE may be dangerous in a BB but you must be a little curious? Is there a possibility that the 22TCM may be tested in the future? The 22TCM has much less case taper.
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Post by HMC710 on Jul 16, 2013 11:59:59 GMT -5
The BB bolt is 15.75 oz. My original calculation put the new buffer at 17 oz, but after review it calcs out to 25 oz so I'll have to weigh it and see for sure. At the max value that puts us at 40.75 oz = 2.55 lbs Using the ratio of pressures, bolt face and weights, simple math puts the RE buffer + bolt to 2.95 lbs. Does the tapered case have an effect, I would say absolutely, but we still have case head separation to contend with. Am I going to develop the TCM in blow back? Not unless I start doing the DI versions and have extra time and cash, or, someone underwrites it. The only reason I''m fixated on the RE blow back is that I can feed it from Uzi mags. I am going to cut the barrel chamber down and rechamber it with less relief and see if it makes any difference. As far as the soft first shot, I've tried every combination possible until I had the last case head separation and I'm making some mods from there....
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Post by 22boomer on Jul 16, 2013 18:04:18 GMT -5
The BB bolt is 15.75 oz. My original calculation put the new buffer at 17 oz, but after review it calcs out to 25 oz so I'll have to weigh it and see for sure. At the max value that puts us at 40.75 oz = 2.55 lbs Using the ratio of pressures, bolt face and weights, simple math puts the RE buffer + bolt to 2.95 lbs. Does the tapered case have an effect, I would say absolutely, but we still have case head separation to contend with. Am I going to develop the TCM in blow back? Not unless I start doing the DI versions and have extra time and cash, or, someone underwrites it. The only reason I''m fixated on the RE blow back is that I can feed it from Uzi mags. I am going to cut the barrel chamber down and rechamber it with less relief and see if it makes any difference. As far as the soft first shot, I've tried every combination possible until I had the last case head separation and I'm making some mods from there.... I like the way you want to stick with things. Any good round that will feed from existing magazines and their magblocks is a good thing for people that already have that stuff but want to shoot something different. I hope the right combination shows up soon!
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Post by HMC710 on Jul 17, 2013 6:29:36 GMT -5
How about the definition of Insanity! Good thing I have a couple DPMS Lo Pro receivers on hand Cut 1/2" off the chamber and installing another "extension" and will give it another go.
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Post by HMC710 on Jul 18, 2013 6:00:21 GMT -5
Got the chamber re-cut with just enough chamfer to de-burr it so its a bit tighter. Kept head space to a minimum and will mount it in a DPMS Lo Pro heavy upper. Maybe give it a go this weekend after the 300 BO's get shipped.
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Post by HMC710 on Jul 22, 2013 8:03:35 GMT -5
The new chamber made all the difference in the world, its like a totally new round With the buffer system I have in, the case would not eject as the BCG only moved 1" at the most. Recoil was minimal and this is the result I had expected from the start. The down side is two-fold: 1. Now the rounds don't feed reliably even with the spire points. 2. Pressures build fast and I got a stuck case when I pushed it a bit. I did not try putting a stock buffer / spring combo in and try again as I was on a time crunch (see 300 BO thread ) but now that the bolt speed is under control, its time to refine what we have here. Pressure: The 6.3 gr Herco load shows up at just under 35000 psi in Quick Load, and I believe it when shooting this round. The primers did back out a bit with this load. Doing some experiments with another round using 7 gr of Herco, I bumped up the load a bit on the 22 RE and got a stuck case on the first round. Because they were not feeding reliably, or ejecting, I only loaded one at a time. The body of the case also showed stretch marks. The next two rounds fired but did not cycle the action. Again, recoil was very mild. I am thinking the "soft first shot" issue was the case sticking in the chamber a bit. QL estimates 41000 psi pressure for the 7.0 gr Herco load so my next move is to go back to H110 and Lil Gun and try again. Herco filled the case and the 7gr load was all it could take. If you tapped the case a bit it would settle down. That's what I was looking for was a safety net so you couldn't over load the case. Pressure II: The Tok case is good for 35ksi. The .223 is good for 60ksi. That's where the TCM has an advantage with the stronger case. I've had three case head separations in my life, 2 of them with the 22 RE blow back. That is a safety issue that has to be dealt with. Feeding: The old chamber took just about everything I could put in except some of the flat nose bullets. The Blow Back adapter can be modified to help this issue so we are going to give that a try first. What I don't want to do is compensate with the chamber - yet. Yet another reason the get the Uzi adapter done..... I am encouraged with the results as the testing is making some logical sense now. I'm still concerned on the pressure / safety side as they get out of control fast and I can't afford the liability. Lets see what our next move does.....
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Post by HMC710 on Jul 23, 2013 7:15:06 GMT -5
Working on the stock uzi mag adapter........ I fed a couple of the 225107 boolits but it did shave off some lead so I put slightly larger chamfer and polish on edge of chamber. Keeping the Uzi mag stock, the follower is tilted up quite a bit, which is what we want here. We'll see what today has in store.
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Post by HMC710 on Jul 25, 2013 7:02:53 GMT -5
Time to do some more testing so I swapped powder over to Lil Gun and loaded up some 35 gr VMax and 55gr FNGC using 10.5 - 12 gr of powder. All should be below max charges so we'll get some buffer combinations together and see what happens in the blow back.
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Post by HMC710 on Jul 26, 2013 7:46:26 GMT -5
Packed things up early yesterday to test the new systems. Installed a 9.7 oz buffer for the 10gr Lil Gun load and the rounds fed and fired from the Uzi mags. Bolt speed was higher than I wanted and the shoulders were pushed fwd a bit. While I had the 17/25 oz buffer out I put it on the scale and got 18 oz. That didn't match my calcs so I pulled the weights and some were over 2 oz and some .5 oz. Looks like some accountant is saving money Empty, the Rifle buffer was around 13 oz so I put that it and things would almost cycle with the 10gr load. Put in a couple of the 12 gr load and got a stuck case. Tried a couple of the 10gr H110 loads and the fed and fired fine - which did not make sense as its the same basic pressures as the 10 gr Lil Gun load - Lessons Learned: 1. Uzi mag worked great but bullet selection is limited. 2. There is a load / buffer combination that works great. 3. Performance appears to be less than a DI gun. 4. There is a lot of "tuning" required on the Blow Back system 5. Safety is still an issue 6. 9mm owners can have another choice. 7. Buy more bullets..... 8. Take better notes. Our next move? 1. Safety is a concern as I have proven its easy to get this thing out of control. Even on the DI gun I hit over pressure very easily, but a locked breech is different than a straight blow back. The Tokarev blow back was also hard on the recoil system and installing a super heavy buffer in a rifle stock helped it out. The 9mm is even known for beating lowers to death. Plus I am sure someone has overload a Tok or 9 and had case failures, but when it happens twice, it gets your attention. 2. Bullet selection is limited. Bro is in Bench Rest mode so my new 45gr FNGC boolits are still waiting to be finished. The 22 Reed Express will probably be a "reload only" round unless Ron really gets a lot of incentive but even then downloading them for Uzi mags probably wouldn't happen. For me, this is not as big a deal as the very limited bullet selection. Swapping to the 30 Luger case would help that out, but that case drops from the 35ksi Tok level to 30ksi Luger level. Performance will suffer, but maybe that will help out on the recoil / safety side until someone overloads.... 3. Recoil tuning is possible and I've got a good selection of buffers and springs to work with now. The issue (or not) is weight. I haven't weighed this rifle yet but with the bull barrel, full quad hand guard with covers, A2 stock, scope, and 1+ lb buffer, 10 lbs would not surprise me. However, I have learned a bit experimenting with the HMLV recoil system, interesting..... 4. Case mortality is high. Because the pressures build so quickly and the necks are worked hard to form, they split easily. Keeping things toned down really adds life, but who wants to run at half throttle? Lots to think about as I watch the machine run this morning, but I think I'll polish things up a bit more and load up some of that brass rod in the lathe.....
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Post by HMC710 on Jul 27, 2013 7:56:02 GMT -5
Going over the chamber this morning and look for any marks or rough edges. May increase chamfer slightly but will take a look first. Have the polishing cloth out and will polish based on chamber condition. Loaded up some 10gr Lil Gun with the 40gr Armscor bullets seated to 1.200" for the Uzi mags. Have a range of buffers and springs set out and will find a safe round that will work and burn up some powder. Also loaded up some of the 37gr boolits at 1500 (est) fps just to see what would happen, along with some other interesting scenarios....
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Post by HMC710 on Jul 29, 2013 9:06:05 GMT -5
Polished up the chamber as there were some marks in it and I put a slightly larger chamfer on it and polished that. All the testing was done with 10 gr of Lil Gun and the Armscor 40gr TCM bullet. Last session the 17.25 oz carrier would not cycle the action but about 1/2" - 1" movement. Polishing took care of that and the most weight I could get for a buffer was 18.45 oz with the fake tungsten weights. The recoil was acceptable yet still harder than what I am looking for. The case shoulders were pushed forward a bit but nothing that didn't re-size right back down. Feeding was done with the Uzi mag and adapter and while it wasn't 100%, it was over 80% with the flat nose bullets. Nose down jams into the face of the barrel every time. Two interesting things did happen: 1. The soft first shot was back and duplicated every session. 2. Recoil increased by round fired. #1: Even with the light buffers, it felt like recoil was increasing by the shot. Once I got enough weight into the carrier to not cycle the first shot, the 2nd and 3rd shots would always cycle. I believe this is because of my test procedure and related to barrel temperature and therefore, chamber size. My test strings were 3 - 5 rounds and I would stop, change weights, load some ammo, go back and test. This took 5 - 10 minutes. If it was "dirt or residue", cleaning the gun would have effected this and it didn't. Temperature is the only thing I can come up with here but I don't have the resources to prove it. The light polish I gave the chamber made a big difference so any increase in diameter with temperature would also. #2: During testing and watching the fired cases it felt like the recoil went up as I shot. Looking at the cases, the 1st case looked better than the 2nd and the 2nd better than the 3rd. I pulled out the chronograph to check velocities. The avg was 2620 fps, High was 2650, Low was 2572. But the interesting part was the velocities went from 2650, 2638, 2619, 2572. They dropped 77 fps as I shot and I could definitely tell the recoil was increasing. Again, the first shot did not cycle and subsequent shots got the shoulders blown forward a bit. I fired 5 shots but the last one did not register. It started to rain so I didn't duplicate the test but between the chrono, case, and seat of the shoulder recoil readings, I believe it. Going back to Quick Load using the closest bullet data I could, the Speer 40 gr SSSP, it predicted 2328 fps for the 10 gr load. We were getting 2650 - 2572. Using the 2650 data and back feeding Quick Load, this equaled an 11.4 gr charge to duplicate this velocity. The predicted chamber pressures went from the initial 23,000 for the 10 gr charge to 33,000 for the 11.4gr charge to get the 2650 fps velocity. Quick Load is usually much closer than this so I will measure case volume again and see what I come up with. Changing gears on this I downloaded the ammo with Unique and tested "lighter" buffers. Getting to sub sonic loads this thing is a hoot to shoot and makes a great plinker. Feeding issues increased so I'm going to look at my adapter, the mags, and last, the barrel chamfer.
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