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View Full Version : To Throat or Not To Throat


Edward429451
February 21, 2008, 09:06 AM
Settle this for me. My shooting buddy has a Para-Ord LDA, and I have a Colt. We load 45's together for both of us to go shooting. We load mostly LRN sized at .452.

His Para LDA has a match barrel and quite close tolerences, and has trouble feeding my LRN bullets at 452. It feeds jacketed bullets at 451 just fine. My Colt has long since been throated and will feed anything without bobble.

He's trying to get me to start sizing my LRN to 451 so he can feed them without problems. I don't want to, these have worked for me for so long that it aint broke and I don't want to fix it. I also do not want to start the logistical nightmare of sizing to two different sizes and trying to keep them segregated.

I say he should get his Para chamber throated. He thinks this will destroy the so called match qualities (accuracy) of his barrel and he is hesitant to do it. His Para is quite accurate, moreso than my Colt. The crux (to me) is that these pistols are our carry guns, and reliability is more desired than precision accuracy. So what if his barrel goes from 1/2" groups at 50 yards (Hypothetical, neither he nor I can shoot that well anyway) to 2" groups? (also hypothetical, remains to be seen if it would degrade accuracy that much), at least it would take a big leap forward in reliability.

I can see not toying with a match rifle barrel because of the distances involved, but on a carry pistol? C'mon man, they're short range anyway, it wouldn't make that much difference. Or would it?

If he has his Para throated, can he expect less accuracy. If so how much? I'd like to hear from some gunsmith types, or Shooters who shoot so much that they know of what they speak because they've BTDT. Can we please keep this objective and not any subjective 'tell him to get a Colt/Glock/Sig' comments? He likes his LDA and does not want to get anything else at this time.

Discuss and enlighten us.

Jim Watson
February 21, 2008, 10:09 AM
I think undersize chambers are a plague on the 1911 community. If it were MY gun, I would run in a standard chamber reamer immediately. I did that on one gun with a "minimum match chamber". The reduction in accuracy was detectable only with a Ransom Rest and reliability was greatly improved.

But it is HIS gun and he seems too prejudiced to make the adjustment. I don't know under what agreement you are furnishing him bullets or ammo, but I would suggest he buy his own lubrisizer with a .451" die. Or a Lee Carbide Factory Crimp Die which irons out the loaded round, bullet and all.

Edward429451
February 21, 2008, 10:34 AM
Thanks for the response Jim. There's no real agreement. It's my equipment, but he pitches in on primers & powder and helps load. It makes me feel sorta bad in a way that he doesn't really enjoy the fruits of his contributions, but I don't want to tweak the whole operation just for his pistol. I don't want to come across as a butthole to him about it, he's a good friend and shooting buddy.

But I'm not a gunsmith so he's hesitant to tweak his chamber on my advice and needs reassurances from knowledgeable people before he's convinced to take the plunge...thus the thread!

I hate those Lee crimpers that size down the whole case & bullet too. That can't be good for the cartridge.

Cowart
February 21, 2008, 01:29 PM
I hate those Lee crimpers that size down the whole case & bullet tooThis may point at the source of the problem. You need to put a taper crimp on the loaded rounds for reliable feeding. This will not destroy the accuracy, and can actually increase it. What kind of crimp are you using?

Unclenick
February 21, 2008, 05:18 PM
To answer your original question, throating won't help. His match barrel has very likely already been throated. The problem is as Jim Watson stated, that it needs a full dimension chamber reamer run in.

The Lee Factory Crimp die in its .45 ACP incarnation applies a taper crimp and squeezes the cartridge OD down. This is to do exactly what your buddy wants, and that is to increase feed reliability. It generally will not deteriorate .45 ACP lead bullet accuracy as the amount of bullet distortion is typically less than being pushed into the barrel throat causes. However, if you have a setup that is shooting well for you, I would not change it. Instead, get a cheap Lee challenger press or a Lee Hand Tool and have your buddy run his ammo separately through the Lee FC die in that press.

In addition to all that, your two guns probably don't like identically seated bullets anyway. When I was shooting a lot of Bullseye matches back in the 80's, I did a lot of experimenting with what it takes to get lead bullets to shoot. In addition to cast bullets, I used to co-purchase a lot of 185 grain swaged Star bullets with other members of our shooting club back then. Those short, soft bullets needed some attention to make them shoot. What I discovered was the one thing that made a serious improvement in group size and would make even a big chamber shoot well, is to seat them to headspace off the bullet rather than the casemouth or, as commonly happens, off the extractor hook (worst for accuracy).

To headspace off the bullet in a 1911, pull the barrel out of the gun and adjust seating depth until a cartridge placed in the chamber with the muzzle down just stops with the casehead even with the back of the barrel extension (hood). This is not likely to be the same seating depth for your gun and your buddy's, so mixing up loads you share won't work for best accuracy, though the shorter of the two seating depths should function in both guns.

http://img529.imageshack.us/img529/1733/45seatingpossibilitiesxls9.jpg

Jim Watson
February 21, 2008, 07:01 PM
I figured Edward was using the term "throated" as a rifleman would, to describe extending the leade into the rifling; not to describe grinding on the feed ramps of a 1911. Which a sharp SAAMI chamber reamer would take care of unless the bullet had an unusual shape.

Seating the bullet to fit the chamber is indeed the best way; Internet Citation of OAL to the third decimal place is not much help if the bullets are not of the same design and preferably out of the same mould.

Edward429451
February 22, 2008, 11:10 AM
No, I was using term throated like Ayoob and all those other gunwriters did in the 80's...get your self a 45, have it ramped & throated, extended ejector and better sights...so I did and my GM feeds almost anything now. Now I see the distinction you guy speak of of running a full size reamer into the chamber.

I barely flare my brass, just enough to not shave lead (550B) and tapercrimp with a Dillon TC die. They are 100% reliable in my GM.

UncleNick, very interesting post. It never occured to me to seat on the lands in a pistol, rifle yes but not in a pistol. You've opened up a whole new direction of experimentation for me, thanks. I'll have him bring over his LDA tonight and we'll compare chamber lengths as you describe.

I tried a LFC die in 44 recently and compared to my *usual* rounds, I did not like how much the brass was worked and figured that all that sizing could not be good for the cartridge. I popped out that carbide sizing ring and just use the crimp feature now.

We already explored the cause of the FTF in his gun. Finished ammo comes out with a .469-.4735 OD, and all the ones that jam in his gun are .473 -.4735 OD, the smaller OD rounds work fine for him. I can load up a magfull of his FTF rounds and my GM just gobbles them up. Interestingly enough, the rounds that fall out at .473-.4735 are older looking brass, and the smaller ones are always newer looking brass.

Unclenick
February 22, 2008, 10:19 PM
You might set aside all your Remington brass for your friend, then. It is famously thin at the case mouth, though that thin brass work hardens so fast, you don't get many reloads out of it before bullets start falling in, despite sizing. It's a good candidate for that Lee FC die, since it won't last anyway.

You'll find some brass, like IMI and some other military stuff get's really thick at the neck. I've got some commercial brass like that too, somewhere. Can't recall the make. South African, maybe.

Throating the underside of the chamber mouth so it makes a more suitable extension to the feed ramp in counterbattery won't affect your buddy's match chamber fit. I, like Jim, took your use of "throating" to refer to a .45 ACP throating reamer's job. That tool puts a more gradual lead angle on the rifling in the throat than the standard GI barrel got. Match barrels often already have that as they come, if they're intended for softball, though not all do.

Brownells has a fixture for chamber throating. I was taught to do it freehand by scraping (though I would cheat with a carbide rotary file in a Dremel tool). I later rigged a collet spin indexer to let my drill press handle the job with that same rotary file. Take a look at a GI barrel's chamber throating sometime, and you'll appreciate why the original .45 accuracy guys found the procedure necessary for SWC bullet feeding.

T. O'Heir
February 23, 2008, 01:49 AM
Paras aren't Colts and Colts aren't Paras. No two firearms, no matter what they are, will shoot nor feed the same ammo the same way. You need to work up a load for your pistol and forget your buddy's pistol. Then your buddy can work up a load for his. The only thing that's the same is the need for taper crimping only.
Chamfering the aft end of a chambering is a feeding thing only, usually with a Colt barrel, but loads or bullet diameters have nothing to do wit hit.

Edward429451
February 23, 2008, 11:21 AM
No two firearms, no matter what they are, will shoot nor feed the same ammo the same way.

I keep hearing this and am not sure that it's true. I realize that it can be true with individual weapons, but as a rule, maybe not. What about the various kinds of Match ammo on the market? People say get XXX brand of ammo, it works great...Hey thanks, works great for me too...
How often do people report bad results with good factory ammo? Not very often. How can this be if what you say is true? If the ammo is made match grade, chances are good that it will be good ammo in more than one gun.

Same thing with the old adage that you can't sight in someone elses rifle. Bullhockey. If one applies the four principles of marksmanship (steady, sight alignment, trigger control, and breathing) to a rifle to sight it in, and another guy picks up said rifle and applies same fundamentals...how can it not shoot to same poa? Of course if 2nd shooter doesn't apply same fundementals, applys a cant or so forth, then results will differ. For this reason the military instructs its soldiers to that if your weapon is lost and they have to pick up anothers rifle, do not attempt to adjust the sights, just apply correct marksmanship fundamentals and keep on going.

If the ammo is crap to start with then the ammo will be crap in many guns. I don't think its an unreasonable proposition to pursue a load that will work good in 2 diff guns. My 45 load works good and very similar in 3 diff guns that I know off the top of my head. How can this be? This is a problem with his gun. We're not gamesman so are not looking for gilt edge accuracy, just minute of felon. Thise are modest goals and very realistic I think.

I guess I'll try to convince him to get his chamber reamed. UncleNicks suggestions will certainly be explored also. Dangit, his gun should be able to feed RN lead and go into lockup reliably.

Lotsa good food for thought brought to the table here. Thanks, and keep it coming.

Unclenick
February 23, 2008, 08:49 PM
To answer several of your questions, lots of semi-auto pistols, especially compact ones, are finicky about which commercial ammo they will and will not feed. This often has more to do with how the magazine lips are formed than it does the feed ramp or chamber mouth, so you might want your buddy to try different magazines, if he hasn't already. Sometimes even going to a different make is necessary. When I attended Gunsite's classes, much was made of whether Wilson or Star made the best 8 round 1911 magazines at the time (early 90's), and which was reliable and which suffered early spring weakness.

Hardball is the common ammo standard and all 1911's should feed it, if their magazines are in good order. However, not all round nose bullets are the same as hardball. The GI stuff has a bullet with an elliptical nose form. Many cast and swagged and some foreign hardball are closer to a hemisphere, making them fatter just behind the tip, and less feed friendly in profile than the original shape. Check the bullets you are buying for this shape difference. Get a box of surplus GI ammo or try Remington, which I recall being pretty close to GI shape for comparison. If he can't feed those, he should complain to the gun's maker.

All brass has a certain amount of spring to it. The fatter the chamber it is fired in, the less completely it returns to shape in the sizing die. If you are leery of squeezing bullets, you can try removing the crimping ring from a Lee FCD, and just running the empty case into it's carbide ring to see if that clears up discrepancy in the finished case diameters? It can also help to pump a case into the regular sizing die twice or three times. Use your calipers to check the effect.

Sighting someone else's rifle only works for optical sights on low recoiling calibers or on bags at the bench. With iron sights, differences in vision will alter the sight picture up to several m.o.a. No two human bodies are shaped the same, either, so medium to heavy recoiling guns are supported differently by their shoulders, changing the recoil moments of the rifle and how the barrel deflects as the bullets move through it. It isn't all that uncommon in sitting position, for example, for two shooters to have 3 or even 4 m.o.a. difference in POI with the same M1 Garand. I know that in prone rapid fire I consistently I throw both Garand and M14 rounds about 1 m.o.a. left of my own windage setting for sitting rapid. I have to adjust for that when I move to the 300 yard line. Bottom line, you have to know your personal come-ups and windage adjustments for each range and position and they aren't necessarily the same as the next guy's. So, that's where the idea of not sighting a rifle for someone else comes from. It only refers to precision shooting. You can still get someone very close on paper with no problem, but you often can't get them closer than that last one or two m.o.a. for position shooting at matches or in the field.

P.S., Have you fired your buddy's gun with the same ammo and had the same feed problem? Sometimes how solidly and firmly you grip the gun makes the difference in feed.

drail
February 23, 2008, 10:58 PM
Unclenick is right on this one. Seen this before.

Edward429451
February 24, 2008, 11:51 AM
Wow, maybe Unclenick should change his handle to Paul Harvey. I think I know something and now for the rest of the story....

Anyway, he has one Para mag, and the rest are 47D's. I (think) the nature of the jams make it not mag related. They all make it into the chamber but some will not let the pistol lock up into battary. Some will when the rear of the slide is tapped with the palm, others will not.

The LRN bullets we use are Lymans 452374 RN, and lately we're using a knock off of the same bullet, a Lee custom group buy 6 cav mould which had the lube groove squared up and they actually have more ojive than the original Lyman bullet. This makes them slightly longer than the Lyman and more pointy. The 2 similar bullets give about the same reliability in his Para. Looking at them side by side, one would think that the Lee version is more feed friendly than the original Lyman.

Brass...I have suspected what you suggest about some of the brass, possibly being older (?) and springing back to cause it. I (probably incorrectly) figured that if my Colt will eat them, then his Para should too. I will try sizing them 2-3 times and check to see if that has any discernable effect, and also some diff brands like the R-P as you suggested.

Sighting a rifle for someone else...I understand completely what you're saying here. These things had never occured to me. (recoil moments & eye, uh, parralax (?)). Hmm.

Interesting question, have I fired his gun and had problems?..I have fired his gun but nowhere near as much as he does, prefering to stick with mine for the practice. Well, no, his gun has never jammed when I shot it. I kind of chalked that up to the odds of him shooting it more than me. Maybe this is an occassional limp wristing thing he does? He is of small stature and his recoil spring is a little lighter than the one on my Colt. I'll segregate some of the fat rounds and see if I can get his Para to jam on me next range trip. Maybe I'll hand him some of the smaller rounds and tell him they're the fat ones as a kind of placebo and not mention the possibility of limp wristing to see what happens.

We compared chambers last night. My Colt looks like a funnel and his Para is absolutely smaller and straight (to the naked eye at least) with no discernable taper at all. He didn't want to do a wax chamber cast, so next range trip I'll make sure to seperate a number of fired cases from his gun to check alongside mine for measurements. Can I expect this to be an accurate way to get chamber measurements?

And how are you using the term softball? LRN bullets or load power (light load)?

Slopemeno
February 24, 2008, 12:42 PM
I'd add more taper crimp.

somerled
February 24, 2008, 07:32 PM
Edward, it might be something as simple as just screwing down the taper crimp die down an eighth of a turn. Aside from damaged magazines, rounds a bit too wide at the case mouth is the leading cause of malfunctions. If the case mouth diameter is larger than .473 in., that will cause problems in many pistols.

Unclenick
February 24, 2008, 08:43 PM
You have a lot to play with already, but you've dropped another good hint in mentioning that weaker recoil spring. It will have a harder time pushing a round into the chamber. Such a spring is common in wad guns (which term I use to refer to target .45's set up specifically to shoot the 185 and 200 grain lead semi-wadcutters over light target charges; softball is properly the 230 grain RNL bullet, but I use the term sloppily to mean any non-jacketed bullet). The light spring doesn't lighten recoil. On the contrary, the least sharp recoil will be felt using a spring too heavy to let the slide get into full counterbattery. At that spring weight the shots feel spongy because the slide never touches down on the frame at all, avoiding the sharp rap. This would be a neat way to reduce recoil, except that unless your grip is identical shot-to-shot, a little limp-wristing can absorb enough rearward motion to prevent the slide from getting behind the next round in the magazine at all, causing a failure to feed. So the best bet is to use the heaviest spring that still lets the slide achieve full counterbattery every time.

Short of a chamber cast, measuring your fired cases is next best. They will have sprung back a little after firing, but the average difference between yours and his taken over a number of cases should tell the tale about the differences in chamber size and maybe even in shape. It also occurred to me that if your chamber is wider and throated at the chamber mouth where his is not, the slight bulge that forms at the unsupported area of the casehead and which is not reached by all carbide sizing rings, may also be a problem. See how far your carbide die sizes down near the casehead and measure that area for comparison with his gun, too.

If grip is the issue, have your buddy try shooting from the classic Weaver stance. Jeff Cooper, God rest his soul, drilled it into us as the best shot and recoil controller because of its rigidity. I won't argue here the opinions that other holds are faster or more instinctive — trick shots prove that if your circumstances let you fire hundreds of thousands of rounds, you can make almost any hold work — but you pretty much can't limp wrist a Weaver hold if you are doing it properly.

To review, the Weaver stance has the gun arm straight and locked or very close to locked, so it forms a kind of straight stock extension. The off hand foot goes half a step forward to let the off hand fingers reach out ahead of the extended gun hand and wrap around its fingers. The offhand elbow is then pulled down until it produces about 40 lbs of rearward pressure back against the straight gun arm. Thus, the gun grip is jammed between opposing 40 lb pressures, pre-loading the recoil resistance of the gun hand and thereby supplying a fairly rigid palm to recoil back against. The fact recoil can't move that pre-loaded palm back easily during cycling is what ensures the slide achieves full counterbattery and gets a good elastic bounce forward to assist the recoil spring in stripping the next round from the magazine and shoving it up the ramp and into the tube.