M48A Accuracy Issues

[Patrick Chadwick]

Guys, I am not disputing that the PRVI ammo may be lighter loaded than other types. What I repeat is that it cannot be the sole explanation for such a serious drop as illustrated in the previous pic posted by Darren. If it's really that bad, the blade must be grotesquely tall or the rifle has a serious fault.

[Sentryduty]

Who has the charts kicking around for sight radius and post height corrections and see if this is even in the realm of adjustment?

I just seen them the other day and cannot recall where.

---------- Post added at 02:22 PM ---------- Previous post was at 02:16 PM ----------

Ah here we go:

As an example, a K98 has a sight radius, rear sight to the back of the front sight, of 20 inches. 20/28 = .714. Multiply this by .004, .714 X .004 = .0028 inches. This is approximately how much you need to move the front sight to move the point of impact at 100 yards 1 inch.

Based on 7.5" vertical adjustment at 100 yards (3600"), with a sight radius of 20" Brownells calculator suggests shortening the front sight by 0.042" to correct the point of aim.

Next question to guys who actually own a K98 (Which I do not) is that a reasonable adjustment? Is there enough "blade" on that style of sight to do such a thing without filing it down to a useless nub.

[Sentryduty]

More update, other Mauser forums tells of different height front sight blades, they suggest that the sight height is marked in (mm) on the underside of the blade when removed from the sight block. Common sizes seem to be 5.3mm to 6.1mm



0.042" is 1.0668mm so if we had a tall 6.1mm sight on the rifle a 6.1-1.0668mm = 5.032mm foresight height for a 100m zero.

I recall that we should be correcting to a 200m zero correct? (asking the audience) which should be about 2.5" high @ 100yrds (approx)? That would suggest that we would need even more front sight reduction, seems like we are on paper running out of foresight blade.

Can anyone check my homework?

[vintage hunter]

What I repeat is that it cannot be the sole explanation for such a serious drop as illustrated in the previous pic posted by Darren

Patrick, I've personally witnessed some of my friends shooting 196gr SP PRVI 8mm ammo on my range and seeing the bullets strike 4-6'' low at 100yds when fired from rifles(most scope sighted hunting rifles) zeroed to be dead on at that range with other brands of ammo loaded with 195-200gr bullets with an average muzzle velocity of 2550 fps.
However, if the OP's rifle is shooting as low as Darren's illustration suggests then I tend to agree with you on the problem being caused by something more than just sluggish ammo.

[Sentryduty]

If the OP's rifle is shooting as low as Darren's illustration suggests then I would agree that the problem is being caused more than just sluggish ammo.

If I read the post correctly, and the "mockup" target I made is accurate, then I too am starting to think something unusual is going on with the rifle.

I was aiming at the center of the black. The shots were clustered in the bottom 3 inches of the target.

[mr.tickle]

So like this?

Yes that would be it!

[cipherk98]

Perhaps it would have been more accurate for me to say while my PPU ammo shoots low, it's low relative to surplus. At 100 yards it's typically 1-2" low whereas surplus is typically 1-2" high, depending on my skill level that day. So in thinking on it I agree with Patrick, something else is going on here, probably with the sights as mine also tends high despite some tweaks likely having been made to the sights back when the stock was cut for my grandfather to hunt deer with (it's since been debubba'd). The only ammo I've had shoot seriously poorly is 170gr Core-Lokt which shouldn't even be discussed in the same sentence as surplus or modern FMJ ammo for these. I had issues with wild groups due to stock fitment issues when I first got the replacement WWII stock for it but it wasn't shooting low.

[Sentryduty]

Yes that would be it!

Good confirmation, thanks!

So gents, we have a rifle that is printing nearly 7.5" low from the expected POI, that should get us started.

Mr Tickle, can you post some photos of your front sight and possibly measure the height of the front blade to see what we are starting with?

[mr.tickle]

Good confirmation, thanks!

So gents, we have a rifle that is printing nearly 7.5" low from the expected POI, that should get us started.

Mr Tickle, can you post some photos of your front sight and possibly measure the height of the front blade to see what we are starting with?

It won't be until friday or saturday before I can get a picture up. But I'll try to get one posted.

Does anyone know an easy way to remove the sight hood?

[AFJon]