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Posted: 10/6/2015 7:08:24 PM EDT
[#1]
Excellent reliability in my x39 7.5 incher. 1900 to 1950 FPS with 123 grainers.
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Posted: 10/6/2015 7:45:38 PM EDT
[#2]
I've had 3 different 7.5" uppers over the years. Completely different builds. All ran like tops, and ate all types of ammo. Obviously they aren't 1000 yard tack drivers, but for what a PDW is supposed to do, they wouldn't have any issues.
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Posted: 10/6/2015 7:59:10 PM EDT
[#3]
I have a few ... No problems whatsoever. Like mentioned above, not a 1000yd driver but for personal defense weapon... Excellent.
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Posted: 10/6/2015 8:31:07 PM EDT
[#4]
Quote HistoryQuoted:
I have a few ... No problems whatsoever. Like mentioned above, not a 1000yd driver but for personal defense weapon... Excellent. Agreed |
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Posted: 10/6/2015 10:07:05 PM EDT
[#5]
I had a RRA, and it would shoot 10 rounds max before failing to extract. BCM extractor upgrade, nope. Buffer weight changes, up and down, nope, even using my friends bolt, buffer and spring, nope.
It was a RRA and never again will I own a 7.5 or a Rock River. |
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Posted: 10/6/2015 11:34:37 PM EDT
[#6]
No problems with function on a 7.5" 300blk with 0.094" gas port. Even fed 30 carbine bullets through it without a hiccup.
Only changed to a KAK 8.5" because of accuracy issues with a cheap eBay barrel. |
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Posted: 10/7/2015 4:07:49 AM EDT
[#7]
Thank you for all of the replies. What is the main cause for some of the problems? Is the length of the gas system that effects it?
Would like to hear some more velocities . My buddy has had a lot of problems with his RRA. My other buddies runs like a champ & is stupid accurate. |
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Posted: 10/7/2015 6:06:39 AM EDT
[#8]
No problems with my dpms kitty kat.
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Posted: 10/7/2015 6:15:28 AM EDT
[#9]
My Adams Arms 7.5" upper runs flawlessly.
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Posted: 10/7/2015 6:25:26 AM EDT
[#10]
My 7.5" SBR in 5.56 runs just fine, never had a single issue with it. Like the others have said I won't be engaging targets at 1000 yards and the flash is a killer at times but i've had no issues with it.
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Posted: 10/7/2015 7:44:19 AM EDT
[#11]
No idea about velocities, but my DPMS 7" upper works great. The only enhancements I made were an extractor O-ring and 9mm buffer to smooth it out (less expensive than an H3).
The only time it was troublesome was after a few hundred rounds of some nasty imported 22lr was fired through it first (Armscor) with a CMMG conversion. Otherwise it's been loads of fun and flawless. One of my coworkers did a Spike's 7.5" upper and it runs like a top as well. |
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Posted: 10/7/2015 5:39:54 PM EDT
[#12]
Thank you! does any one know if the 7" kmr will work with a 7.5 barrel?
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Posted: 10/8/2015 12:28:37 AM EDT
[#13]
I've used 7" carbine rails with 2 - 7.5" barreled pistols. Barrel was about even with the end of the rail. I would imagine KMR would have similar dimensions to other carbine rails, but can't be 100% positive.
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Posted: 10/8/2015 8:35:18 PM EDT
[#14]
7.5 budget PSA frankenbuild has been flawless up until my crappy $20 Chinese buffer came apart after a few thousand rounds.
My 16" rifle has had more issues |
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Posted: 10/8/2015 9:02:59 PM EDT
[#15]
I had some cycling issues with mine initialy, needed an adjustable gasblock. Problem solved
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Posted: 10/9/2015 3:25:41 PM EDT
[#16]
Quote HistoryQuoted:
My 16" rifle has had more issues I was thinking the same thing. I've had 16" rifles that gave me more stress than my 7.5" uppers. |
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Posted: 10/10/2015 1:04:25 AM EDT
[#17]
7.5" .30 cal barrels are more like 10.5". The x39, .300BO, and 6.8 all work well down to 7.5. 5.56 is where the issues lie, and the velocity starts falling off quicker under 10.5" Getting a few reports on it in one thread isn't going to sort out when you need to see how 1,000 of them run. And they need to be all the same caliber.
If 10.5" is dropping under 1,000 foot pounds at 100m, then you can expect 7.5" to be losing even more at a shorter range. What that is can be found on ballistic charts, what the gun is meant to do by and large doesn't change. It's a short range PDW for close quarters combat. Note that a lot of guys move up in caliber to regain the lost power, so, of course they aren't disappointed in how it works with 7.5". They're still getting knock down power. Be careful comparing apples and oranges, tho. 6.8 and .300 aren't cheap plinker, x39 has a different magazine and that affects cost and reliability in some cases. What you need to do is ask how it's working for the one caliber, and discard the reports of others who don't fit. And the answers are here, there are those who have to finesse it more than just putting it together to make it work. Same as all the boutique builds with a bunch of non GI parts and wonky gas length combinations. Plenty of that our there, too. If you like it build it, but don't expect it to run or last as long as a 16". The gas pressures are much higher across the board under 14.5" and there's more erosion at the gas port, plus pressure on the bolts. They just break more parts sooner. You can't get something for nothing. |
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Posted: 10/12/2015 1:24:04 AM EDT
[#18]
My brother has a 7" PSA.
It gets a stuck case (with broken rim) every time with Wolf. He tried a pigtail gas tube (which I don't believe in), o ring on extractor and without, adjusting gas, everything. Chamber pressures are too high before extracting. I would have thought that with a melonite barrel that it would be slicker, but nothing. It worked in the beginning, but once it got dirty, nothing. Yeah, other people have had success. But personally, I would go with a 10.5" carbine or even a 11.5 middy from faxon to make sure chamber pressures are lower before extracting. |
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Posted: 10/12/2015 5:57:04 AM EDT
[#19]
Quote HistoryQuoted:
My brother has a 7" PSA. It gets a stuck case (with broken rim) every time with Wolf. He tried a pigtail gas tube (which I don't believe in), o ring on extractor and without, adjusting gas, everything. Chamber pressures are too high before extracting. I would have thought that with a melonite barrel that it would be slicker, but nothing. It worked in the beginning, but once it got dirty, nothing. Yeah, other people have had success. But personally, I would go with a 10.5" carbine or even a 11.5 middy from faxon to make sure chamber pressures are lower before extracting. worked in the beginning but quit once it got dirty.....I wonder what the first thing you should do is? The steel case ammo and a pistol gas system aren't an ideal situtation to start with, toss in a little carbon and instant jammomatic. |
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Posted: 10/12/2015 8:53:56 AM EDT
[#20]
I've got 2 7.5" 5.56s w/ bear creak arsenal barrels % 1 7.62x39 7" from radical firearms. All with standard BCGs andcarbine buffers. All run perfect with wolf and tula.
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Posted: 10/13/2015 3:29:32 PM EDT
[#21]
Try using the heaviest buffer you can find (H3 or heavier) and a BCM 5 coil extractor spring. Gun sounds crazy overgassed. Sometimes it takes a few hundred steel case before it runs smooth. I had tons of stuck cases with Tula in an 8.5 nitride PSA but a heavier buffer and spring plus a break in helped get it to 100%.
Basically I think you need to increase the amount of time that the bolt is locked in battery, allowing the case to contract and be ripped out by the 5 coil spring. Also use a GI chamber brush on a rod with solvent and get that chamber clean. You may be doing these things already..just throwing some ideas out. |
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Posted: 10/15/2015 3:33:33 AM EDT
[#22]
I use a Aero Precision 7.5" melonite barrel with regular gas block, FA BCG, and LWRC Ultra Compact stock kit. Mine cycles pretty much anything I have ran through it. (prior to this config I ran it as a pistol on a SpringCo Blue spring and H2 buffer set up. No issues.
SBR 
Pistol 
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Posted: 10/15/2015 2:44:42 PM EDT
[#23]
So far my MSA defense build has worked flawlessly.
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Posted: 10/15/2015 7:41:14 PM EDT
[#24]
What hand stop is that?
Quote HistoryQuoted:
I use a Aero Precision 7.5" melonite barrel with regular gas block, FA BCG, and LWRC Ultra Compact stock kit. Mine cycles pretty much anything I have ran through it. (prior to this config I ran it as a pistol on a SpringCo Blue spring and H2 buffer set up. No issues. SBR http://i1319.photobucket.com/albums/t677/balloo933/DSC01825_zps5hy9xxca.jpg Pistol http://i183.photobucket.com/albums/x282/balloo932/DSC01674_zpse6d13fd6.jpg |
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Posted: 10/15/2015 10:14:53 PM EDT
[#25]
Quote HistoryQuoted:
What hand stop is that? Quote HistoryQuoted:
What hand stop is that? Quoted:
I use a Aero Precision 7.5" melonite barrel with regular gas block, FA BCG, and LWRC Ultra Compact stock kit. Mine cycles pretty much anything I have ran through it. (prior to this config I ran it as a pistol on a SpringCo Blue spring and H2 buffer set up. No issues. SBR http://i1319.photobucket.com/albums/t677/balloo933/DSC01825_zps5hy9xxca.jpg Pistol http://i183.photobucket.com/albums/x282/balloo932/DSC01674_zpse6d13fd6.jpg Gear Sector. i use KAC handstops on other builds, but I found that the Gear Sector and the KAC panels match up dam near perfectly together. |
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Posted: 10/16/2015 10:45:03 AM EDT
[#26]
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly.
On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. |
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Posted: 10/17/2015 7:14:35 AM EDT
[#27]
That tsx is a nasty bullet. Have you tried anything heavier in the tsx?
Quote HistoryQuoted:
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly. On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. |
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Posted: 10/17/2015 9:05:35 PM EDT
[#28]
Mine shot a gas key loose recently, still functioned but didn't lock back on an empty mag.
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Posted: 10/19/2015 1:48:00 PM EDT
[#29]
Quote HistoryQuoted:
My brother has a 7" PSA. It gets a stuck case (with broken rim) every time with Wolf. He tried a pigtail gas tube (which I don't believe in), o ring on extractor and without, adjusting gas, everything. Chamber pressures are too high before extracting. I would have thought that with a melonite barrel that it would be slicker, but nothing. It worked in the beginning, but once it got dirty, nothing. Yeah, other people have had success. But personally, I would go with a 10.5" carbine or even a 11.5 middy from faxon to make sure chamber pressures are lower before extracting. he should stick to brass or zinc case. My bushy m4 does this but with brass or zinc it runs just fine. Far as my 7.5 pistol runs just fine i ran cheap stuff and brass seems to be accurate for its intended use. 
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Posted: 10/19/2015 6:25:36 PM EDT
[#30]
Quote HistoryQuoted:
That tsx is a nasty bullet. Have you tried anything heavier in the tsx? Quote HistoryQuoted:
That tsx is a nasty bullet. Have you tried anything heavier in the tsx? Quoted:
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly. On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. Yes, I couldn't get enough velocity for the 50gr to expand completely in gelatin. These are the 50gr, top two are from my 18" 
These are the 45gr, (through the 18" at 3350fps all the petals sheared off) 
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Posted: 10/19/2015 7:12:45 PM EDT
[#31]
Thank you ! Thats good to know .
Quote HistoryQuoted:
Yes, I couldn't get enough velocity for the 50gr to expand completely in gelatin. These are the 50gr, top two are from my 18" http://i3.photobucket.com/albums/y59/glock2027/CIMG2123_zps4hnxjw6v.jpg These are the 45gr, (through the 18" at 3350fps all the petals sheared off) http://i3.photobucket.com/albums/y59/glock2027/4b1e86c3-6df5-4037-aae5-3e6f9ea8a4a3_zpsebhbg5rx.jpg Quote HistoryQuoted:
Quoted:
That tsx is a nasty bullet. Have you tried anything heavier in the tsx? Quoted:
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly. On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. Yes, I couldn't get enough velocity for the 50gr to expand completely in gelatin. These are the 50gr, top two are from my 18" http://i3.photobucket.com/albums/y59/glock2027/CIMG2123_zps4hnxjw6v.jpg These are the 45gr, (through the 18" at 3350fps all the petals sheared off) http://i3.photobucket.com/albums/y59/glock2027/4b1e86c3-6df5-4037-aae5-3e6f9ea8a4a3_zpsebhbg5rx.jpg |
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Posted: 10/19/2015 7:15:10 PM EDT
[#32]
Have you tried any other bullets / Like vmax, or nosler 77gr cc ?
Quote HistoryQuoted:
Yes, I couldn't get enough velocity for the 50gr to expand completely in gelatin. These are the 50gr, top two are from my 18" http://i3.photobucket.com/albums/y59/glock2027/CIMG2123_zps4hnxjw6v.jpg These are the 45gr, (through the 18" at 3350fps all the petals sheared off) http://i3.photobucket.com/albums/y59/glock2027/4b1e86c3-6df5-4037-aae5-3e6f9ea8a4a3_zpsebhbg5rx.jpg Quote HistoryQuoted:
Quoted:
That tsx is a nasty bullet. Have you tried anything heavier in the tsx? Quoted:
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly. On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. Yes, I couldn't get enough velocity for the 50gr to expand completely in gelatin. These are the 50gr, top two are from my 18" http://i3.photobucket.com/albums/y59/glock2027/CIMG2123_zps4hnxjw6v.jpg These are the 45gr, (through the 18" at 3350fps all the petals sheared off) http://i3.photobucket.com/albums/y59/glock2027/4b1e86c3-6df5-4037-aae5-3e6f9ea8a4a3_zpsebhbg5rx.jpg |
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Posted: 10/20/2015 9:34:39 AM EDT
[#33]
Quote HistoryQuoted:
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly. On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. Neat. How much penetration are you getting with the 45gr TSXs? |
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Posted: 10/20/2015 11:48:58 AM EDT
[#34]
Quote HistoryQuoted:
Neat. How much penetration are you getting with the 45gr TSXs? Quote HistoryQuoted:
Quoted:
I have had my 7.5", 95% dpms parts, for about 8 years, it has always run flawlessly. On my light 55gr plinker loads, it runs 2200fps,my defensive loads are 45gr TSXs they run 2550fps and are a bit warm but get complete expansion and penatration at 15yds in calibrated gelatin. Neat. How much penetration are you getting with the 45gr TSXs? About 13.5" @15yds 
Made a thread in the reloading section a while back. http://www.ar15.com/forums/t_6_42/447149_45gr_Barnes_TSX_expansion_from_my_7_5_AR_pistol.html |
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Posted: 10/20/2015 11:56:59 AM EDT
[#35]
Quote HistoryQuoted:
Have you tried any other bullets / Like vmax, or nosler 77gr cc ? No, I figured the TSX would be the best choice for expansion and holding together. I have 77gr and 90gr SMK loads for my 18", I fired a 90gr(~2600fps) into the gelatin and it mangled and came apart, not ideal. My intention was a defensive load for the pistol just to see if could be effective( aside from the blast and fireball  )
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Posted: 10/20/2015 7:48:48 PM EDT
[#36]
What would you say the max effective range is? I wonder how it compares to the 5.7? I think it uses a 40 grain vmax.
Quote HistoryQuoted:
No, I figured the TSX would be the best choice for expansion and holding together. I have 77gr and 90gr SMK loads for my 18", I fired a 90gr(~2600fps) into the gelatin and it mangled and came apart, not ideal. My intention was a defensive load for the pistol just to see if could be effective( aside from the blast and fireball )
Quote HistoryQuoted:
Quoted:
Have you tried any other bullets / Like vmax, or nosler 77gr cc ? No, I figured the TSX would be the best choice for expansion and holding together. I have 77gr and 90gr SMK loads for my 18", I fired a 90gr(~2600fps) into the gelatin and it mangled and came apart, not ideal. My intention was a defensive load for the pistol just to see if could be effective( aside from the blast and fireball )
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Posted: 10/21/2015 8:04:21 AM EDT
[#37]
Quote HistoryQuoted:
What would you say the max effective range is? I wonder how it compares to the 5.7? I think it uses a 40 grain vmax. Quote HistoryQuoted:
What would you say the max effective range is? I wonder how it compares to the 5.7? I think it uses a 40 grain vmax. Quoted:
Quoted:
Have you tried any other bullets / Like vmax, or nosler 77gr cc ? No, I figured the TSX would be the best choice for expansion and holding together. I have 77gr and 90gr SMK loads for my 18", I fired a 90gr(~2600fps) into the gelatin and it mangled and came apart, not ideal. My intention was a defensive load for the pistol just to see if could be effective( aside from the blast and fireball )
Barnes claims they expand down to 1800fps, if so, my load would make it to 185yds. I guess it depends on what effective means, I would consider effective to be full expansion and at least 12" of penatration. I would presume 50-75yds to be max range realistically. I don't know anything about the 5.7 to compare. Though I would say varmint bullets would be a very poor choice for a defensive round. |
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Posted: 10/21/2015 8:05:09 AM EDT
[#38]
...dt
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Posted: 10/21/2015 6:57:21 PM EDT
[#39]
Thank you! ill order some to try. Do you think r 15 would work? Quote HistoryQuoted:
Barnes claims they expand down to 1800fps, if so, my load would make it to 185yds. I guess it depends on what effective means, I would consider effective to be full expansion and at least 12" of penatration. I would presume 50-75yds to be max range realistically. I don't know anything about the 5.7 to compare. Though I would say varmint bullets would be a very poor choice for a defensive round. Quote HistoryQuoted:
Quoted:
What would you say the max effective range is? I wonder how it compares to the 5.7? I think it uses a 40 grain vmax. Quoted:
Quoted:
Have you tried any other bullets / Like vmax, or nosler 77gr cc ? No, I figured the TSX would be the best choice for expansion and holding together. I have 77gr and 90gr SMK loads for my 18", I fired a 90gr(~2600fps) into the gelatin and it mangled and came apart, not ideal. My intention was a defensive load for the pistol just to see if could be effective( aside from the blast and fireball )
Barnes claims they expand down to 1800fps, if so, my load would make it to 185yds. I guess it depends on what effective means, I would consider effective to be full expansion and at least 12" of penatration. I would presume 50-75yds to be max range realistically. I don't know anything about the 5.7 to compare. Though I would say varmint bullets would be a very poor choice for a defensive round. |
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Posted: 10/22/2015 8:06:02 AM EDT
[#40]
Quote HistoryQuoted:
Thank you! ill order some to try. Do you think r 15 would work? If you mean Reloader 15, no I doubt you would even be able to cycle the bolt much less get enough velocity for expansion with Reloader 15. You will likely need a faster burning powder that occupies less volume per grn. |
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Posted: 10/22/2015 2:43:53 PM EDT
[#41]
Excellent real world ballistics findings! Thanks for sharing your experience. It's refreshing to see actual proof instead of a bunch of speculating and theorizing.
Do you have a central repository for all such info? Like a master forum thread, or blog? |
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Posted: 10/22/2015 4:38:07 PM EDT
[#42]
Quote HistoryQuoted:
Do you have a central repository for all such info? Various threads strewn about Arfcom  , not really any terminal ballistics stuff though(other than this)
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Posted: 10/22/2015 4:40:19 PM EDT
[#43]
I use R15 with 77gr SMK through a 24" barrel...
This should help you find a suitable powder x427: Barnes load data |
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Posted: 10/23/2015 6:21:50 AM EDT
[#44]
Quote HistoryQuoted:
I use R15 with 77gr SMK through a 24" barrel... This should help you find a suitable powder x427: Barnes load data The light bullet wont let pressure get high enough with R15. |
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Posted: 10/23/2015 5:22:19 PM EDT
[#45]
Ok thank you !
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