2011BLDR
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Posts posted by 2011BLDR
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The gas port presser and the dwell time of that port presser are critical to the operation of the direct gas impingement system. The Original carbine gas port Location, presser and the dwell time were developed in the XM177 carbine program that featured a short barrel (10.3”) with a muzzle device that increased back presser to increase reliability. When this device was classified as a “suppressor” by the ATF, Colt increased the length to 11.5” and adjusted the port size. The M4/ M4A1 carbines were designed to utilize all of the existing parts (gas tubes, hand guards…) from the short barreled carbines (XM177, Commando 11.5”) so that no new tolling and parts would be needed, the 14.5” barrel was only to allow for mounting of a bayonet and has been the source of many of the inherent reliability issues, as the port presser and the dwell time are not optimal. Additionally the 14.5” barrels exhibit a reduced service live due to accelerated port erosion that causes erratic and increased cycle timing leading to increased extraction, ejection and feeding problems further reducing overall reliability. The commercial 16” carbines that use the carbine gas system exhibit even less reliability than the 14.5” versions due to the additional 1.5” of barrel and the corresponding increase in port presser and dwell time leading to faster port erosion and the associated erratic / increased cycle timing leading to the same increased extraction, ejection and feeding problems.
The original ammunition that the carbine gas system was designed around was M193 Ball. The ammunition change to M855 Ball was instated with no design changes to the original gas port presser and dwell time. The continued expansion of the ammunition menu has also contributed to the reliability issues in the M16 carbine family. At the two extreme ends of the current ammunition menu are the frangible bullet loads designed for CQB and the 77GR Long Range Match ammunition. Both loads have a different gas presser curve than the current standard M855 Ball and effect the port presser and dwell time differently.
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2011BLDR
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I have 2 open pistols with slide mounted Optima/ Fire Point/ J Point.
• The first one was done by SHPD (built around 1997-98) where the Optima weaver mount was trimmed down and screwed in to the slide retaining the location points between the mount and optic to aid in not losing zero when changing batteries. I have changed batteries numerous times and never lost Zero. This Is Optima that was a replacement under warranty when the first lens became loose in the body, no issues in 125,000 rounds since on this optic.
• The second one has the Arredondo double battery package that Arredondo milled the slide for this has location points machined in to the slide. I have changed batteries numerous times and never lost Zero on this set up either. This Is Fire Point picked up on close out, no issues in 125,000 rounds on this optic. The electronics are becoming tired; the dot is not as bright as it uses to be even with a double battery. I will be trying the Delta point as a replacement soon.
On both guns I have no issues with retaining zero and only re-zero when making a change to my load.
I tried a Pride Fowler and it did not last, the battery door screws striped themselves under recoil in less than 1,000 rounds.
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2011BLDR
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There are 2 kinds of parallax as related to small arms :
1. Optical
2. Sight location relative to bore
Aim points and EOTech are both pretty much optical parallax free.
Both will have a parallax in the over bore height, the distance between the sighting mechanism and the weapon's bore can introduce significant errors when firing at close range and is also influenced by the chosen BZO and ballistics. A 14.5” barreled .223 firing M855 with a 25M/ 300M BZO will have a -4” offset at 1m a + 18” offset at 175M and be on at 25M & 300M
http://en.wikipedia.org/wiki/Parallax
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2011BLDR
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I have used different optics in the past and rank them in the following order:
1. S&B 1.1-4X Short Dot with CQB reticle
2.
3.
4.
5. TR21 Amber Triangle
6.
7.
8. EOTECH XPS3-2 and 3X flip magnifier
9. Aim Point M4 (2 MOA dot) and 3X flip magnifier
10.
11.
12. Millet 1-4X DMS
13. Aim Point M2 (4 MOA dot) and 2.5X flip magnifier
14.
15.
16. 3.5 or 4X ACOG with fiber optics
17.
18.
19. Any dot sight without a magnifier
The blanks in the above chart represent what I feel are the missing levels of capability between the optics. I have shot a friend’s Meopta 1-4X and would rank it on par with the TR21. I also feel the TR24 would stay on the same ranking as the TR21 it really offers nothing to close the gap to the S&B (i.e. repeatable BDC elevation knob, changeable BDC elevation knob, ability to half switch the power to the dot and use only the cross hair and the Mil reference lines built in to the reticle).
The S&B 1.1-4X Short Dot is a very misunderstood optic it has inherent capabilities that nothing else can match but is often dismissed solely on price point. The oracular adjustment allows the 1.1 setting to be as low as .90 if focused for close in targets (CQB). Additionally having a rear lens cap in place will severely compromise the performance on the 1.1 setting.
Out.
2011BLDR
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The Larue "po boy" is great but there are some small issues to be aware of:
• Eye relief is short; it needs to be at the rear of the receiver rail. Running it in front of a backup iron rear sight really compromises the “po boy” eye relief.
• The “po boy” has a focus ring located at the front of the tube; I see many of them mounted with the front of the tube flush with the mount effectively eliminating the ability to adjust the focus.
If you are starting with no optics then investing in 1-4 scope is better than a dot + magnifier. If you already have a dot then a magnifier can offer an expanded capability for less of an investment.
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2011BLDR
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How a trigger feels when you shoot, how it breaks and how it resets is far more important to me. I want a really short reset with a forward bias in the trigger. I use free hanging weights to test and set all my triggers. The following are my setups:
• Limited 5” .40 is at 2LB
• Limited 6” is over 1.75LB but under 2LB
• Limited 5” 9mm is over 1.75LB but under 2LB
• Open guns are over 1.5LB but under 1.75LB
Parts selection also plays a part in this, I only us the Clark 4 finger sear spring this allows greater latitude to adjust the disconnect reset function and forward trigger bias.
Out.
2011BLDR
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Inconsistency is it.
I have 3 STI frames that have utilized the same 9 ea .40 SVI mags from an older SVI framed pistol that I sold years ago. All 4 pistols have worked flawlessly on the 9 SVI mags until I cracked a grip in the 6” gun this year and had to replace it. The gun has had major problems since installing the replacement grip; the old trigger simply has too much movement in this grip. I will be rebuilding it with a new grip, trigger, hammer, sear and disconnect to eliminate the issues.
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2011BLDR
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Triggers need to be fit to each grip. The drag could be interference on the trigger body or on the bow. What you describe sounds like it is the bow. Best way is to mark each part of the trigger reinstall and move it back and forth in the grip. Then look for the drag marks and remove material as needed. Go slow and recheck often.
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2011BLDR
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In addition to removing the tang I add plastic (2011 only) to the top of the main spring housing on one side where it interfaces with the bottom of the grip safety then adjust with a file so that the grip safety is held down hard. Be careful not to change the profile on the mainspring cap hole.
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With a tritium vial, I assume?
Yes, tritium front and rear I will git an exact on the width tonight.
Out,
2011BLDR
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Springfield Armory TRP Operator front night sights are .100
Out,
2011BLDR
Leupold Delta point red dot sight
in Open Pistols
Posted
I just received the Delta point as a replacement for a Fire Point / J Point on an open pistol that has a milled slide for the Arredondo double battery package and mount machined in to the slide. My initial impressions are that the Delta point glass is very clear, electronics are very bright and the lens size is much larger. I hope to be able to BZO Friday and shoot a match on Sat.
Out.
2011BLDR