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1950 mk7 DA |
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bubba ho tep 
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Joined: June 19 2017 Location: KY abode Status: Offline Points: 169 |
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 Topic: 1950 mk7 DAPosted: March 19 2022 at 7:35am |
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I don't have accuracy issues crimping...but I am also not shooting for 1 MOA or less. When I have sought super duper accuracy I have "soft loaded " rounds and it's a hard benchrest method to beat but does incur a marked pressure jump .
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bubba ho tep
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Joined: June 19 2017 Location: KY abode Status: Offline Points: 169 |
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Posted: March 19 2022 at 7:33am |
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I crimp all my cartridges , especially the 7,62 nato as I utilize them in L1A1's , HK and now an M1A. As well I always use a size trim die so ALL of my brass in any given caliber I have such a die for is absolutely consistent in length. I do so for even 303 as it is not hard in an enfield to knock a bullet in the case with rapid bolt manipulation.
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britrifles
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Posted: March 19 2022 at 2:02am |
You may get sub-MOA groups. When the barrel in my .303 Fulton No. 4 was fairly new, it gave 10 shot groups off the bench under 1 MOA with handloads and no crimp. With crimp, just over 1 MOA. The crimp die will give varying amounts of crimp (neck tension) depending on case length. Variability is detrimental to accuracy. You will never see a bench rest shooter use a crimp die. |
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Goosic
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Posted: March 18 2022 at 5:04pm |
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Using the crimp puts more tension on the bullet reducing accuracy especially with the 7.62mm. The accuracy load for the 7.62mm/.308 from what I have learned is 42.0grns of IMR4895 using the 168grn HPBT SMK. OAL of 2.83" with absolutely no crimp...
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Olddust
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Posted: March 18 2022 at 4:05pm |
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If “crimping is detrimental to accuracy”, not crimping the 7.62 loads I made up would make them shoot even better? The 39.5 grain load was 1-1.5 moa and the 40.5 was 1.0 moa What improvements should I expect with not using my collet crimp die? |
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britrifles
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Posted: March 18 2022 at 1:48pm |
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Yup, I did the same thing to my F/L sizing die.
I also bought a -0.001 inch undersize .303 mandrel from Lee for use in the collet neck sizing die to get a bit more neck tension.
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Shamu
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Posted: March 18 2022 at 1:27pm |
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^^^ This. I'll share a trick. take your expander ball & chuck it in a power drill. now spin it with some verry very fine carborundum wet & dry. Just enough to get a slick mirror finish. It reduces the diameter minutely & increases "pull" like crimping, but without the disadvantages mentioned.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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britrifles
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Posted: March 18 2022 at 12:55pm |
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You will find that crimping the case mouth on the bullet gives no improvement in accuracy. And unless the cases are all trimmed to the exact same length, it is detrimental to accuracy. I stopped crimping rifle cases when I discovered this about 20 years ago.
If loading for a lever action rifle with a tubular magazine, or pistol and revolver ammunition, a crimp is necessary to keep the bullet from moving in the case. But it is unnecessary in a box magazine fed rifle.
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Olddust
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Posted: March 18 2022 at 11:52am |
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Thank you for the kind words but I think it was some luck and the mostly rifle. Its an early dcra conversion.
I loaded 39-42g in half grain incremets but have yet to try the 41,41.5, 42 as my available range time ran out. However 39.5 gr was nearly as good as 40.5gr I am getting a ph5c for the 303 and hope to make some gains. Just received the lee neck sizing and factory crimp for 303 so i am going to try the same process. |
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britrifles
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Posted: March 17 2022 at 4:34pm |
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Sub-MOA groups is pretty tough to do with iron sights. You are an exceptional shooter! You are no novice Olddust!
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Olddust
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Posted: March 17 2022 at 12:09pm |
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That is interesting data. Trying to tune up a load for my Faz mk2.
I had great success in trying a few reloads of the 1965 7.62 components. My mk1 conversion really stacked them up with 40.5 gr of the stock powder/ bullet/ primed case with a seating depth of the longer end of the average military loading. Still had .065 jump to the lands but sub 1 moa 5 shots group with ph5 rear sight. Rested, as I am a novice in prone position. |
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britrifles
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Posted: March 17 2022 at 6:31am |
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I chrono’ed some DA 51 Mk 7z a few years back. Temp 50 deg F. Velocity data at 18 feet from muzzle.
MV = 2412 fps, ES = 78 fps, SD = 25 fps. 10 rounds grouped at 2 MOA. I pulled the bullets on ten rounds and subbed in a 174 gr SMK with these results: MV = 2507 fps, ES = 44 fps, SD = 14 fps. 10 rounds grouped at 2 MOA, 9/10 shots at 1 MOA Note that the SMK produced a higher muzzle velocity than the Mk 7 service bullet, nearly by 100 fps. Perhaps better bore sealing due to the thinner jacket on the SMK. |
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britrifles
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Posted: March 17 2022 at 3:58am |
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I don’t believe it is. I’ve shot hundreds of rounds of this, I always clean the bore and chamber right after every shoot with Hoppes 9.
The DI is known to be non-corrosive primers, but I’m not absolutely certain of the DA.
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Olddust
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Posted: March 17 2022 at 3:35am |
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Yes that’s the stuff. It is quite consistent in powder charge and bullet weight. Do know if the priming is corrosive?
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britrifles
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Posted: March 17 2022 at 3:30am |
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I still have a fair bit of DA 50 and DA 51, both are Berdan primed and loaded with NC Powder. Accuracy is quite good, the ‘51 shoots 1.5 MOA, and was used for DCRA matches.
DI is Defence Industries DA is Dominion Arsenal Is the headstamp on your DA cases look like this?  |
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Olddust
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Posted: March 16 2022 at 8:02pm |
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I am only pulling the berdan primed DA. Shooing the DI boxer primed for the brass.The powder is not cordite. Its little cylinder shaped grains. Looks Same as what was in the 65 DA 7.62.
Going to load from 10% under the average charge weight (39.6) and see if i can find a sweet spot. That DA berdan primed brass will get reduced loads of 4227 and cast lead for practice |
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Olddust wrote: