Front sight adjustments ?

[K-framer]

I have found, with a couple of trips to the range, that my newly acquired Model 10-5 snubby shoots consistently 6" low, at 10 yards. I thought it might have been ME, that is, my reaction to the wood stocks on the gun. However, I've now disproven that - the gun shoots the same with a rubber Pachmayr grip. There is no windage problem, the snubby shoots nice, tight groups in the centre of the target face, just 6" low.

My normal load is 3.6 grains of Bulleye, behind a 158 grain LSWC. This load shoots beautifully, though about 1.5" right and 1.5" low, in my other 10 (3" HB 10-8).

Obviously, the front sight will need to be filed down to raise POI. I noticed that the front sight on this 10-5 snubby is VERY high, MUCH taller than that of my 3" 10-8. I ran the calculations and it appears that I need to lower the front sight by 0.095" !, or thereabouts. Almost 1/10" ! I've done this sort of thing before, so I intend to be quite careful - I'll start with filing down the front blade only about 1/3 or so of the caliculated dimension - then test. That way, I should be able to "walk" the POI up to coincide with the POA.

My question is, is this typical with S&W revolvers ? My 10-5 appears (internally) almost unused. I really think that the previous owner put a few rounds through it (maybe only 1 box), then threw it in a drawer and neglected it. It certainly does not appear that the front sight has ever been touched - and it looks likely to have been done on my 10-8 (which was probably a duty gun). Anybody else have this experience ? Did S&W's of that era (probably '70 - 75) come with really tall front sights, with the intention that the end user would adjust as needed ? Or, is it that standard loads today are that much softer than those of that era ?

I'd be keenly interested in answers on this from some of the old hands here (please excuse the reference to age).
Thanks !

 

[DCWilson]

That is not typical. File away if you must, but may I first ask about the relative speed of your preferred load? I don't know if your preferred handload would be considered hotter than standard commercial loads, but warm loads land low. I encourage you to shoot a box of 148 gr match wadcutter ammo and observe where the holes appear. You might also ask a range buddy to fire a few rounds from the gun with the same ammo at the chosen sighting distance and see if he gets the same results.

Nearly a tenth of an inch sounds like too much to me. Just doing the proportions in my head, losing about .05 from the top of the front sight on a gun with a two-inch barrel should raise POI about six inches at 30 feet.

 

[K-framer]

Thank you for the insight, DCWilson. All good ideas, to be sure. I'll do some serious thinking, before any mods to the gun.

However, I do know that my "favored" hand load (it just happens to be the one that shoots the tightest groups) is not, according to the information I have, particularly hot. In fact, I've heard legions of people refer to a load about the same as this one (namely, 3.5 grains of Bullseye under a 158 grainer) as a standard target load. The published load info I have indicates that this load is smack in the range of standard 38 special loads - not at the light end, mind you, but definitely not in +P territory, either. This load gets me 1.5" groups, with my 3" 10-8, regularly. So, though there certainly CAN be large variances between the results of two guns, using the same load (and most often, there is some variance - even if the two guns are identical).....I doubt the load is the issue. At least, not the whole issue.

But, I do take your meaning - certainly it IS a good idea to test various loads to see if the results will be similar. I will do that.

Actually, since you mentioned it, another shooter did test the gun (with the same load), during this last range session. He is a friend, one of the RSO's and a very experienced shooter (much better than I). He got the same results....and agreed with me about the sight modification. He also produced approx. a 1" group, right at the bottom of the paper (6" low), with the gun - so I know that it's a shooter.

As to the velocity of the load, I don't know. I've not had the opportunity to chrono it (I don't own a chronograph, anyway). A couple of published sources indicate around 900 fps, but that was probably not achieved with a 2" barrel. So, I can't really say.

Finally, the calculated dimension for the front sight (height) reduction sounded excessive to me, too. It was derived from a formula involving the distance to the target, in inches (SD)....the desired change in POI, also in inches (DC).....and the sight radius of the firearm involved (SR).

Thus,

SR x DC
------------- =
SD

a dimension, indicating the desired height of the front sight.

Obviously, in this circumstance, IF the front sight is to be modified, it must be shortened, in order to raise POI. For my 10-5 snubby, this formula indicates that the desired front sight
height should be about 0.05893"......which seems awfully short to me ! So, I must admit, I do not quite trust this result.

This formula WAS designed for use with rifles. Perhaps that might make some difference here, I do not know.

If anyone has any more insight into this issue, I would welcome your input. In the mean time, I shall take my time and give the matter a thorough work through - BEFORE undertaking any irreversible mods to the gun.

Thanks very much.