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Shorter Front Sight.


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#1 TN.Frank

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Posted 12 March 2004 - 06:35 PM

huh.gif Well, I took my 27A1 out today and put a few rounds thru it. It shot straight but because I made the short range blade into a peep sight it's shooting low. I couldn't for the life of me use the notch that was on that blade, couldn't even see it, guess it's my glasses or something but by drilling it out and making a peep out of it I can sight the front blade just fine. Trouble is that at 25 yrds I'm shooting about 3" low. I need to get a shorter front sight to bring my point of impact up about 3" to get zeroed in. I don't plan on using the sight folded up, long range style so a shorter front blade won't matter for long range, I just want to get the short range sight hitting POA. Before I file on it I wanted to see if I could just get a shorter replacement and save my self some trouble. Sorry about rambling on so, thanks for any info.

Edited by TN.Frank, 12 March 2004 - 06:36 PM.

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#2 TN.Frank

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Posted 12 March 2004 - 10:19 PM

I didn't drill the appture bigger, if anything it's too big from the factory. I drilled the notch part and made IT an appture like it should have been from the factory. The notch sight is just plain stupid that close to your eye, no way can you focuse on it to aim the gun. I drilled a hole dead center below the notch and now I have an appture sight for my "close range" sight as well as for my "long range flip up sight". Problem is that the gun is sighted in for close range using the usless notch and since the appture that I drilled is lower then the notch it makes the gun shoot low. blink.gif
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#3 PK.

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Posted 12 March 2004 - 10:36 PM

Use the following formula to calculate how much you need to remove from your sight:

C= R/E divided by D

C= correction (the amount of metal to remove)
R= sight radius
E= amount of POI error
D= distance from target (in inches)

HTH

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#4 TN.Frank

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Posted 12 March 2004 - 10:52 PM

huh.gif So is it 28"x4" divided by 2700"?? that would give me .042 to take off, does that sound about right. Can't I just buy a front sight that 40 thousands shorter? I really hate to file on anything on this guy. I even ordered a different mag catch so I can put the stock one up and not mess with it. I'm sure that someone has to have different front sight blades that I can buy. Also, do ya'll understand what I did now? I didn't touch the ladder part of the sight, it's the part that you sight thru when the ladder is folded down, the part with the notch that I made into an appture sight. Does anyone know why the factory didn't make both parts of the sight appture? Wouldn't it make more sence then that crazy, hard to see notch. blink.gif
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#5 junglewalk

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Posted 12 March 2004 - 11:08 PM

blink.gif Holey Sister Mary Hombre PK !.....Just glancing at your formula, made my 2-celled brain hurt, and made me want to get a knuckle sandwich from that big Nun in my past !!! huh.gif .....Frank, I cut that awful block off, got a $10. rear adjustable 03 Sprigfield sight, & soldered onto the track....The other peep still works, when the ladder is lifted up. Of course, in order to have left/right adjustment, I had to cut a half-moon in the right protective ear. You can elect not to go that far, if you choose.... wink.gif Elevation of the peep is under your control too, for adjustment of different weights/powered ammo you may shoot, that Phil was talking about. Here is a pic..........jw
user posted image
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#6 TN.Frank

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Posted 12 March 2004 - 11:56 PM

smile.gif Now that looks sweet JW. I thought about just chuckin' the whole rear sight(since you can't adjust it for windage any way) and just stickin' an M1 style sight on it. That way I'd have a peep set for 100 yrds. with a higher notch that's suppose to be set for 250yrds. I really think 100 yrds. is about as far as I'd care to shoot this gun so the peep on the M1 sight would work out great. I really don't want to screw up this gun filing on it, I'd rather replace a part then mess up an original part. It's a 27A1 Deluxe that I want to make look more like a WWII style '28A1 so an M1 non-adjustable sight would be fine. Also, I'd like to take off the comp., don't think a 45ACP in a 11lb. gun really needs a comp. and it'd make it 2" shorter too boot. Would the M1 sight and base be a good option if I can't get a replacement front sight to bring up the POI? Of course I could always use alittle Tennessee elevation and just aim alittle higher to get the bullet to hit where I want it too. LOL. Really though, would the M1 sight work ok for what I'm after? ph34r.gif
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#7 TN.Frank

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Posted 13 March 2004 - 12:56 PM

PhilOhio, this gun has screws holding on the rear sight, not pop riviets so it's just a matter of unscrewing the "Lyman" style sight and replacing it with an M1 style sight. The screw holes should have the same spacing and the screws that held the Lyman sight will work for the M1 sight. This is just a simple swap of parts. I have found out that the comp is on a threaded bbl. so I can't just take it off and put on an M1 style front sight. I'm just going to leave the comp on, it's not that big of a deal. I guess another thing that I could do would be to get longer screws for the Lyman and put a plate under it. That would raise it up so it'd hit POA with the new peep that I drilled. I think an 1/8"(0125") plate would work, I could use the Lyman as a template to mark off the holes in a plate, then blue it and install it with the longer screws, that would solve the problem and I'd still have a stock looking sight on the gun. I guess I wouldn't even have to use a plate, I could just use some washers under the Lyman with longer screws to adjust the highth. I may give that a shot(pun intended,LOL) to see if it'll work. Talk to ya' later. wink.gif
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#8 TN.Frank

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Posted 13 March 2004 - 01:32 PM

huh.gif This sounds odd but heck, I'm new to Thompsons. I unscrewed the rear sight from the upper receiver and took some dementions of the screws. I'm getting 5/64" at 36 Threads/inch. Does that sound right, if not what are the screws that hold on the rear sight? All I need to do is that some that are 1/8" longer, same counter sunk type and add some 1/8" thick washers between the receiver and base to raise the sight. That should get me on target. If it does then I'll see about having a plate made that's the same thickness(so it'll look nicer) and have one made up. It shouldn't cost more then about $5 bucks to have it made up. Then I can blue it to match the gun and loctite the screws into place so they won't come loose. What about that, looks like I've come up with a way to adjust the elevation on a Thompson without replacing the sights, LOL, what'll I think of next?? rolleyes.gif
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#9 PK.

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Posted 13 March 2004 - 02:21 PM

the screws are metric; M4x0.7
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#10 TN.Frank

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Posted 13 March 2004 - 02:24 PM

I'll check at Lowe's, they normally have a good selection of screws. I agree, eaiser is always better and this method doesn't alter the gun. I hate to file on things if I don't have to. I can get some washers and shim it up until it's hitting where I want it to hit. Then I can measure the thickness of the washers with my dial calipers and have my local gun smith machine a plate that'll fit the base of the Lyman exsactly. If it's made right you won't even really notice that it's there. Also, if I want to change the POI I can have a thicker or thinner plate made up and mark it for a know distance. That way I could have one made up for 25yrds, 50yrds, 100yrds and 150yrds respectively. In fact if someone wanted to they could make up a group of plates with matching screws and sell em' as a kit. Food for thought for some of you gunsmiths out there(PK). wink.gif
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#11 TN.Frank

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Posted 13 March 2004 - 02:26 PM

Thanks PK, dang metric, well Lowe's might have them, they do have a good selection. By the by, did you get my PM about the cocking knob? Talk to ya'll later. biggrin.gif
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#12 Charlie

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Posted 14 March 2004 - 05:30 PM

Speaking of washers, while reading these posts, I was wondering if you could somehow attach (silver solder?) an appropriately sized washer right over the area where you look through the rear sight notch. You couldn't adjust elevation.
But you couldn't do it with the open rear sight notch, anyway.
And that way you get an aperture and not need to file down the front sight.

Just my $.02

Charlie
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#13 TN.Frank

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Posted 14 March 2004 - 07:52 PM

I had thought about that(adding a washer to make an apture out of the notch) but didn't think it'd look quite right. I did find a bunch of M4x.7 screws at Lowe's today along with the proper washers. They also have some strips of aluminium that should be wide enough to make a plate out of once I get the proper thickness. I can get some alumimium black to make it match the blue on the receiver so it'll blend in better, also it'll be eaiser to work with then steel. I'm still kickin' around the idea of just getting an M1 style fixed rear sight, I think it'd look better. Talk to ya'll later. biggrin.gif
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#14 AZDoug

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Posted 14 March 2004 - 11:49 PM

I assume you are talking modern production SA 1927A.

WH/Kahr was kind of funky with their sights, front and aft even back in the FA production.

The ersatz lyman sights appear to have a P17 Enfield ladder on the 1980's guns, and I have no idea what they put on after that, but the P17 ladder had a different aperture height that the original lyman, and WH made taller front sights, IIRC, to compensate for that.

Now another problem you may have is I have seen the barrel bore and threads on WH later receivers are not lined up parallel to the receiver, so the barrel is tilted up or down somewaht to the receiver top, and that causes sight issues. (actually, i think the front barrel seating surface is not perpendicular to the receiver, casuing barrel pointing out at funny direction).

Just get a sight and modify it by building it up with weld or something until is works.

Doug
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#15 Supershooter

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Posted 15 March 2004 - 09:31 AM

This fix may have an effect similar to scratching fingernails on a blackboard for some of you, but it is not time consuming or invasive. Bend the barrel upward. I've had a .22 tubular magazine rifle and a shotgun come into my hands that would not shoot to point of aim. A little barrel bending fixed both and it is not visible. The rifle shot low with the rib completely removed from the rear sight. It was brought up to point of aim with bare hands, butt on the floor with pressure on the muzzle and middle of barrel. Support the Tommy barrel between two wood blocks and bear down in the middle after testing the barrel's stiffness to get a feel for its bendability. You can do it at the range, bending in stages and test firing. If you go too far, bend it back a little.
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#16 TN.Frank

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Posted 15 March 2004 - 12:41 PM

cool.gif I would agree, having worked at McMillan Arms in the late 80's I know how important it is to have a straight barrel if you want any kind of accuracy at all. It's eaiser to adjust sights and if you mess up a sight it's eaiser to replace then it is to replace a barrel. If it works for you that's cool, but this Thompson is my baby, I've wanted one for most of my life and now that I've got it I really don't want to mess it up. In fact, I'm even going to pass on a good deal on a 45ACP pistol so I can order some parts for my Thompson from PK, that's how important this gun is to me. wub.gif I really love my '27A1.
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#17 wolfer113

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Posted 15 March 2004 - 01:04 PM

you people use the sights?????? lol.....hey frank...just stick the barrel in a fork of a tree and bend it till it hits where you want...lol..lol.....j/k...where in TN do you live frank? i'm about 30 miles north of nashville...on the tn/ky line.....close to clarksville....springfield area.....always looking for shooting buddies thats near.....you can email me at ibewolfer@aol.com ........Thanks
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#18 TN.Frank

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Posted 15 March 2004 - 01:15 PM

smile.gif I'm about 120 miles east of Nashville in a little town called Crossville, 'course it ain't so little anymore. Do you ever get down to Smashville to watch the Preds play? I love Hockey, next to guns it's my favorite thing. Looks like they may make the playoffs this year. Anyway, talk to ya' later. cool.gif
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#19 TN.Frank

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Posted 15 March 2004 - 03:10 PM

wink.gif Yup, this is the place. ph34r.gif
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#20 LIONHART

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Posted 16 March 2004 - 01:08 PM

After AO/WH ran out of the original Lyman Sights they did switch to the Enfield P17 Rear Sight, housed in the traditional Rear Sight Base. They must have ran out of those too, since they later switched to their own manufacture POS Rear Sight. Frank, perhaps you can locate an original P17 Ladder Sight and install that one. Might be a good way to go. Just my .02
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